Ci a ion: A andia, N.; Ga a e, J.I.;
Mabe, J. Medical De ices wi h
Embedded Senso Sys ems: Design
and De elopmen Me hodology o
S a -Ups. Senso s 2023,23, 2578.
h ps://doi.o g/10.3390/s23052578
Academic Edi o s: Mia Folke,
Ma ia Linden, Ma s Bjö kman and
Ning Xiong
Recei ed: 29 Janua y 2023
Re ised: 23 Feb ua y 2023
Accep ed: 24 Feb ua y 2023
Published: 26 Feb ua y 2023
Copy igh : © 2023 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
senso s
A icle
Medical De ices wi h Embedded Senso Sys ems:
Design and De elopmen Me hodology o S a -Ups
Ne ea A andia 1,* , Jose Ignacio Ga a e 2and Jon Mabe 1
1Teknike , Basque Resea ch and Technology Alliance (BRTA), 20600 Eiba , Spain
2Depa men o Elec onics Technology, Uni e si y o he Basque Coun y (UPV/EHU), 48080 Bilbao, Spain
*Co espondence: ne ea.a andia@ eknike .es
Abs ac :
Embedded sys ems ha e become a key echnology o he e olu ion o medical de ices.
Howe e , he egula o y equi emen s ha mus be me make designing and de eloping hese de ices
challenging. As a esul , many s a -ups a emp ing o de elop medical de ices ail. The e o e, his
a icle p esen s a me hodology o design and de elop embedded medical de ices while minimising
he economic in es men du ing he echnical isk s ages and encou aging cus ome eedback. The
p oposed me hodology is based on he execu ion o h ee s ages: De elopmen Feasibili y, Inc emen al
and I e a i e P o o yping, and Medical P oduc Consolida ion. All his is comple ed in compliance
wi h he applicable egula ions. The me hodology men ioned abo e is alida ed h ough p ac ical use
cases in which he de elopmen o a wea able de ice o moni o ing i al signs is he mos ele an .
The p esen ed use cases sus ain he p oposed me hodology, o he de ices we e success ully CE
ma ked. Mo eo e , ISO 13485 ce i ica ion is ob ained by ollowing he p oposed p ocedu es.
Keywo ds: embedded sys ems; medical de ices; new p oduc de elopmen ; wea able de ices
1. In oduc ion
Nowadays, o add ess he heal hca e sec o ’s challenges, bio echnology is con inu-
ously demanding inno a ion. Recen e en s such as he COVID-19 pandemic highligh
he need o de elop mo e sophis ica ed, eliable, and connec ed medical moni o ing and
diagnos ic de ices quickly and e icien ly. In addi ion, he ageing o he popula ion and
he inc ease in dependency a es, oge he wi h he equi emen o moni o and ca e o
pa ien s’ heal h a hei homes, aise he need o new echnological sys ems o deal wi h
hese si ua ions.
Embedded connec ed sys ems ha e become a key echnology o apidly de eloping
inno a i e low-cos diagnos ic solu ions. Embedded sys ems can be ound in bo h moni o -
ing and diagnos ic sys ems. Some examples a e glucose moni o s, pacemake s, wea able
moni o ing de ices, e c.
Being awa e o he cu en oppo uni y in he sec o , an inc easing numbe o bio ech
s a -ups a e en e ing he medical de ice business. Despi e ha ing excellen ideas and
echnical solu ions, many o hese s a -ups ail. This is due o a lack o knowledge o he
heal hca e sec o and he egula o y equi emen s ha mus be me .
The design and de elopmen o embedded medical de ices a e egula ed by Eu opean
Medical De ices Regula ions: 2017/745 MDR [
1
] and 2017/746 IVDR [
2
]. These wo egu-
la ions ha ha e en e ed in o o ce in 2022 o egula e he design and de elopmen o hese
de ices wi h mo e s ic equi emen s han he p e ious di ec i es. De ices al eady on he
ma ke mus be ece i ied ollowing hese egula ions, obliging heal hca e companies o
adap hei p oduc design and de elopmen p ocesses. No icing he di icul y in adap ing o
he new equi emen s, on 16 Feb ua y 2023, he Eu opean Commission decided o ex end he
deadline, depending on he isk o he de ice [
3
]. O he s anda ds de ine addi ional aspec s.
Many egula o y equi emen s demand a p ocedu al me hodology o pe o ming
such de elopmen s. A e analysing exis ing p oduc design me hodologies, none has been
Senso s 2023,23, 2578. h ps://doi.o g/10.3390/s23052578 h ps://www.mdpi.com/jou nal/senso s
Senso s 2023,23, 2578 2 o 30
iden i ied ye ha ully mee s he needs o s a -up companies wishing o de elop medical
de ices. None o he iden i ied me hodologies is de ined in a way ha can add ess he
h ee key cha ac e is ics o hese de elopmen s: compliance wi h new Eu opean medical
de ice egula ions, de elopmen o inno a i e p oduc s wi h embedded ha dwa e and
so wa e, and inexpe ienced companies in he sec o .
The e o e, as i s main con ibu ion, his a icle p esen s a me hodology ha ou lines
he s eps o design and de elop embedded medical de ices. As i is a me hodology o
s a -ups, he a o emen ioned me hodology aims o minimise inancial in es men du ing
high- isk echnological phases. In addi ion, i encou ages he e alua ion o he de ice by
he clien o p oduc manage in he ea ly s ages o de elopmen .
The p oposed me hodology, in ended o be a guide o s a -ups in he medical sec o ,
is alida ed h ough i s applica ion in he de elopmen p ocesses o se e al medical de ices.
The main use case is he de elopmen o a wea able medical de ice o i al signs moni o -
ing. Howe e , o he use cases a e p esen ed as e e ences. Many ha e al eady ob ained he
CE ma king, hus demons a ing he me hodology’s e ec i eness. Fu he mo e, he mos
c i ical p ocedu es o he me hodology we e alida ed by he ce i ica ion body Socié é
Géné ale de Su eillance (SGS) wi hin he ISO 13485 ce i ica ion p ocess conduc ed in
Teknike , a Resea ch and De elopmen Cen e.
The p oposed me hodology add esses he needs iden i ied in a icle [
4
]. Figu e 1
illus a es how he wo a icles a e ela ed.
Figu e 1.
A icle con ex . In blue a e aspec s add essed in he a icle [
4
], and in pu ple a e hose
co e ed in his a icle.
2. Regula o y Con ex
Du ing medical de ice design and de elopmen phases, compliance wi h he s anda ds
egula ing hese phases is pa amoun . The e o e, his sec ion aims o b ie ly highligh he
s anda ds co e ing he design and de elopmen phases o medical de ices in Eu ope. The
main egula ions a e he Eu opean Medical De ice Regula ion (MDR) and he Eu opean In
Vi o Medical De ice Regula ion (IVDR), which de e mine medical de ices’ equi emen s o
CE ma king. In a icle [4], he main equi emen s o each s anda d a e ex ac ed.
The MDR [
1
] de ines he ules and obliga ions ha all manu ac u e s and dis ibu o s
mus comply wi h o place a medical de ice on he Eu opean ma ke . On he o he hand,
Senso s 2023,23, 2578 3 o 30
he IVDR [
2
] de ines he same aspec s o in i o medical de ices. In addi ion, o he
s anda ds egula e speci ic aspec s o medical de ice design and de elopmen p ocesses.
The IEC 60601 amily o s anda ds [
5
] de ines unc ional sa e y and pe o mance
equi emen s o elec ical medical de ices and equipmen . I co e s such aspec s as
elec omagne ic compa ibili y.
The IEC 62304 [
6
] s anda d desc ibes he p ocesses associa ed wi h all phases o he
so wa e li ecycle o a medical de ice. This s anda d aims o ensu e ha medical de ice
so wa e is de eloped sa ely.
The ISO 14971 [
7
] s anda d de ines he equi emen s o isk managemen and p o ides
a amewo k o assessing and con olling he sa e y isks associa ed wi h medical de ices.
This s anda d is key o bo h medical de ice manu ac u e s and hei supplie s.
Ano he key s anda d is IEC 62366-1 [
8
], which co e s he usabili y o medical de ices.
This s anda d helps designe s add ess he de ice’s usabili y aspec s o ensu e ha i s use
in ol es minimal isk.
ISO 13485 [
9
] egula es quali y managemen sys ems o medical de ices. To his end,
his s anda d de ines he cha ac e is ics ha a quali y managemen sys em mus ul il o
ensu e ha hese p oduc s a e eliable and o high quali y.
Finally, IEC 81001-5-1 [
10
] de ines he li ecycle and equi emen s o de eloping and
main aining medical so wa e o make i cybe secu e. The p ocesses de ined in his
s anda d a e equi alen o hose de ined in IEC 62304. The e o e, i can be conside ed ha
his s anda d complemen s IEC 62304 in e ms o cybe secu i y.
3. Re iew o he P oduc Design Me hodologies
The use o a p oduc design me hodology can help o add ess he egula o y and echnical
equi emen s in ol ed in he de elopmen o hese de ices e ec i ely. The e o e, his sec ion
e iews exis ing me hodologies o p oduc design. Speci ically, i includes Hea yweigh
me hodologies such as Wa e all, V-model, Inc emen al, I e a i e, Spi al and P o o ype; Agile
me hodologies such as Sc um, Kanban and C ys al amewo ks; and o he me hodologies
such as Lean S a up, Design Thinking and S age-Ga e. Hyb id me hodologies ha combine
di e en me hodologies a e also discussed. Fo each o he e iewed me hodologies, hei
sui abili y o di icul y in being implemen ed o he de elopmen o heal hca e p oduc s is
de ailed. Finally, a e no icing ha none o he s a e-o - he-a me hodologies ul ils he na u e
o he de elopmen o embedded medical de ices and hei egula ion, he mos ele an
equi emen s o cha ac e is ics o each o he cu en me hodologies a e ex ac ed. This aims o
p o ide a s a ing poin o he de ini ion o a new me hodology o designing and de eloping
embedded medical de ices. I is wo h no ing ha when de ining hese equi emen s, special
conside a ion is gi en o he equi emen s ha a me hodology mus mee o enable a s a -up
company o success ully de elop a medical de ice.
3.1. Hea yweigh Me hodologies
Hea yweigh me hodologies a e hose based on linea and sequen ial ask execu ion.
The basis o hese me hodologies is o ensu e ha he de elopmen is ca ied ou as planned.
They base he success o he p ojec s on deadlines, cos s and quali y. To accomplish his,
de elopmen is planned and di ided in o di e en phases, which cons i u e he li ecycle.
In gene al, hese me hodologies end o ha e he ollowing cha ac e is ics [11,12]:
•
P edic i e app oach: Classic managemen de ines in de ail he expec ed ou pu and
d aws up a de elopmen plan, which is used o calcula e he cos and deadlines.
Du ing execu ion, moni o ing and su eillance ac i i ies a e ca ied ou o a oid any
possible de ia ions om he plan.
•
De ailed documen a ion: De elopmen s end o ha e a la ge amoun o documen a ion.
This is due o he emphasis on he iden i ica ion o equi emen s.
•
P ocess-o ien ed: I s objec i e is o de ine a p ocess ha is able o answe o he needs
o he manage , designe , codi ie , e c. Each p ocess o he me hodology is usually
di ided in o di e en sub-p ocesses.
Senso s 2023,23, 2578 4 o 30
•
Uni e sali y: P ojec s, despi e hei di e si y, ha e common execu ion pa e ns. Manage-
men p ac ices a e based on hese cha ac e is ics and a e alid o any ype o p ojec .
3.1.1. Wa e all Me hodology
This me hodology da es back o 1970 when Wins on W. Royce de ined he Wa e all
model ha exis s oday [
13
]. The Wa e all me hodology is based on a sequen ial p oduc
de elopmen p ocess. The p ojec is di ided in o sequen ial phases and can only mo e
o he nex phase when he p e ious one has been comple ed. I s name de i es om
he sequen iali y equi ed by his app oach. This me hodology includes i e phases [
14
]:
equi emen s de ini ion, design, implemen a ion, e i ica ion and main enance.
Wa e all’s s uc u e is simple and clea [
15
]. I s use is ecommended in cases whe e
he equi emen s a e expec ed o emain s able h oughou de elopmen [
16
]. This allows
planning du ing he ini ial de elopmen phase bo h in e ms o ime and cos . In addi ion,
he deli e ables gene a ed a each s ep ensu e an e icien low o in o ma ion be ween
phases. This, oge he wi h i s clea and well-de ined s uc u e, makes i an easy me hod-
ology o con ol and manage he p ojec . I s clea s uc u e, easy managemen and he
possibili y o con ol de ia ions make i an ideal me hodology o inexpe ienced eams.
On he o he hand, being a linea and sequen ial me hodology makes i no e y lexible
o changes ha may a ise du ing he de elopmen p ocess [
17
]. A simple change implies
e-execu ing all he phases, esul ing in a e y cos ly p ocess. This me hodology ocuses on
ul illing es ablished equi emen s and does no p io i ise ea ly cus ome eedback [
18
]. Fo
example, in de elopmen s in ol ing use in e ace design, his can become a p oblem since
cus ome eedback is no ecei ed un il he la e s ages o he p ojec . In addi ion, ano he
di icul y o p ojec s wi h so wa e componen s is ha es ing is comple ed a a e y la e
s age and only a he sys em le el. Iden i ying so wa e bugs a e he comple ion o he
en i e de elopmen can lead o a high le el o ewo k [19].
In hecase o he de elopmen o anew medicalde ice, he e i ica ion o c i ical pa s mus
be comple ed a he ea ly s ages o de elopmen . The e o e, his me hodology is no sui able o
use in de elopmen s wi h high echnical unce ain y. The design and de elopmen p ocedu es
de ined in he medical de ice s anda ds sugges he use o sequen ial and linea me hodologies,
such as Wa e all, as hey de ail a speci ic o de o execu e some de ined p ocesses [20].
3.1.2. V-Model Me hodology
The V-Model me hodology is also known as he Ve i ica ion and Valida ion Model.
Paul Rook de ined i in 1980 as an e olu ion o he Wa e all me hodology [
21
]. As wi h
Wa e all, i is a sequen ial me hodology, equi ing he comple ion o one phase be o e
mo ing on o he nex . In his case, i s ocus is mo e on achie ing he success ul e i ica ion
o all s ages, hus ensu ing a high quali y o de elopmen [
22
]. This me hodology is based
on h ee p ocesses, he i s one, he le pa o he V-model ha de ines he con e sion
o equi emen s in o design, and he second one, he lowe pa o he V ha conside s
he implemen a ion o execu ion. Finally, he hi d p ocess, he igh pa o he V-model,
con empla es he in eg a ion and e i ica ion o he de elopmen [23].
Simila ly o Wa e all, i is simple and easy o implemen . In con as o Wa e all, he
planning and de ini ion o he e i ica ion a e comple ed p io o de elopmen , sa ing
ime and cos . On he o he hand, he execu ion o e i ica ion is en isaged a e he imple-
men a ion o he comple e de ice. This can be ine icien o e y complex de elopmen s.
As wi h Wa e all, i is a igid me hodology wi h no lexibili y o changes o e o s [
24
].
In addi ion, his app oach does no con empla e using ini ial p o o ypes o alida e he
concep . This me hodology is app op ia e o adding unc ionali y o an exis ing p oduc
o o he ull de elopmen o a new p oduc . I is also sui able o use in eams wi h high
echnical expe ise and in scena ios wi h low echnological unce ain y.
Rega ding i s applicabili y o medical de ice de elopmen , he IEC 60601-1 de ines
as an example a V-model o he de elopmen o a P og ammable Elec ical Medical
Sys em (PEMS). Likewise, his model is also adop ed by he IEC 62304 s anda d o he
Senso s 2023,23, 2578 5 o 30
de elopmen o medical de ice so wa e. The e o e, i can be concluded ha he mos
s aigh o wa d way o comply wi h some o he medical de ice s anda ds is o use he V-
model. Howe e , i is no a sui able me hodology o s a -ups as hey do no usually ha e
consolida ed echnical eams, he p oduc equi emen s o be de eloped a e no de ined
om he beginning o he p ojec and he de elopmen s, due o hei na u e, usually p esen
a high deg ee o echnical unce ain y.
3.1.3. Inc emen al Model
The inc emen al model seeks a p og essi e g ow h o he p oduc ’s unc ionali y.
Tha is, he p oduc will g ow g adually in each i e a ion un il i eaches he unc ionali y
equi ed by he end cus ome [
25
]. I is also known as he Successi e Ve sion model.
The main cha ac e is ic o his me hodology is ha asks a e di ided in o i e a ions o
achie e he desi ed unc ionali y [
26
]. The i e a ions in his model a e no independen ;
hey a e linked de elopmen s. Unlike in Wa e all and V-model, du ing he ea ly s ages o
de elopmen , he clien can ha e pa ial deli e ables ha allow hem o assess how he
in es men is being ma e ialised. As p esen ed in Figu e 2, each de elopmen phase is
composed o ou asks: equi emen s, design, implemen a ion, and es ing.
Figu e 2. Inc emen al model and i s ou pu s.
In e ms o p ojec managemen , his app oach is mo e complex han Wa e all, as i
equi es de ailed planning, mo e phases o manage, s onge communica ion and coo dina-
ion wi h he clien , and he gene a ion and con ol o di e en e sions o he de elopmen .
Likewise, i is necessa y o ha e a clea ision o he inal goal o he de elopmen , as he
ini ial planning mus ake in o accoun all he s ages o he p ojec . All his makes he cos
o de elopmen highe han using he Wa e all me hodology.
This me hodology is an ad an ageous al e na i e o medical p oduc de elopmen
whe e he o e all equi emen s a e clea . I is also sui able when he e is a lo o echnical
unce ain y o he echnical eam is no highly quali ied.
3.1.4. I e a i e Model
The I e a i e model is based on he i e a ion o se e al Wa e all cycles. Howe e ,
his model does no equi e ha ing all he speci ica ions o he sys em o s a wi h he
de elopmen [
27
]. The model execu ion s a s wi h he c ea ion o an ini ial e sion o he
sys em. Then, i is e alua ed, and u he i e a ions a e pe o med o imp o e and add
unc ionali y o he sys em. The inpu s and ou pu s o he model a e p esen ed in Figu e 3.
Senso s 2023,23, 2578 6 o 30
Figu e 3. I e a i e model and i s ou ou pu s iden i ied as (1)–(4).
This cus ome -o ien ed model ocuses on ob aining use eedback o de ec e o s in
he ea ly s ages o de elopmen . E ec i e eedback and model execu ion equi e a good
communica ion plan and he clien ’s in ol emen as ea ly as possible [
28
]. I is o ien ed
owa d e ec i e isk managemen as i educes isk by p o iding con inuous e iew and
edesign o he p oduc [
29
]. S a -up companies o en adop his me hodology o b ing
hei solu ions o ma ke quickly, as i allows hem o ha e a unc ional sys em solu ion a
he end o each i e a ion [30].
Howe e , i s use o medical p oduc s is no ad isable, as no conside ing all he
sa e y equi emen s a he beginning o he de elopmen can lead o a sys em a chi ec u e
ha does no mee he inal equi emen s, de ia ing he p ojec om i s a ge ed lead
imes and cos . The de elopmen o medical p oduc s in ol es he gene a ion o a lo o
documen a ion, which u he inc eases as he p oduc e ol es, o he pe o mance o
ce i ica ion es s o en need o be epea ed. This app oach can be in e es ing o de eloping
unc ionali ies ha a e no an essen ial pa o he medical de ice and whe e end-use
eedback is impo an , e.g., o he design o use g aphical in e aces.
3.1.5. Spi al Model
The Spi al model was de eloped by Ba y W. Boehm in 1986. I is a combina ion o
he Wa e all model and he I e a i e model [
31
]. I is based on a se ies o i e a ions. A e
he execu ion o each i e a ion, a p o o ype is a ailable on which o assess i s isks and
sui abili y. This model ocuses on educing de elopmen isks. Typically, i is di ided in o
ou phases [
32
]: de e mina ion o objec i es and iden i ica ion o al e na i e solu ions, isk
iden i ica ion and analysis, de elopmen and es ing, and planning he nex i e a ion.
Comple ing a ask is equi ed o mo e on o he nex s ep, which makes i s execu ion linea
and sequen ial. A he end o each phase, he equi ed deli e ables a e gene a ed, easing he
ansi ion be ween phases. In addi ion, he ocus is on ecei ing cus ome eedback ea ly in he
design p ocess, which equi es a con inuous dialogue wi h he cus ome .
The I e a i e and Spi al models ha e simila applica ions, bu in his case, his model
places pa icula emphasis on isk analysis [
33
]. As discussed abo e, he e ec i e de el-
opmen o a medical de ice elies on accu a e isk managemen . The e o e, his model is
mo e app op ia e han he I e a i e model o medical de ice de elopmen . Despi e his, i
p esen s he same p oblem as he I e a i e model. On he one hand, con used speci ica ions
a he beginning o he p ojec can cause de ia ions in he p ojec deadlines and cos s.
On he o he hand, due o heal hca e egula o y equi emen s, i may no be p o i able o
launch pa ial p oduc e sions o ma ke .
Senso s 2023,23, 2578 7 o 30
3.1.6. P o o ype Model
The p o o ype model is based on he de elopmen o sys ems called p o o ypes. I is
an i e a i e p ocess o ial and e o . S a ing om an ini ial speci ica ion, a p o o ype is
buil and e alua ed be o e an imp o ed p o o ype is de eloped [
34
]. The model, as shown
in Figu e 4, is composed o six phases [
35
]: ini ial equi emen s, design, p o o ype building,
cus ome e alua ion, p o o ype e inemen and p oduc implemen a ion and main enance.
Figu e 4. P o o ype model.
This model equi es a high deg ee o cus ome in ol emen . The e o e, i is possible
o iden i y whe he he de elopmen sa is ies he use ’s expec a ions in he ea ly s ages o
de elopmen . In addi ion, e o s o de ia ions can be iden i ied ea ly, and i can help o
educe cos s and ime compa ed o he Wa e all model. On he o he hand, as wi h I e a i e
de elopmen , he numbe o i e a ions can some imes inc ease d ama ically, leading o
highe cos s and delays.
The ac ha he e a e se e al i e a ions can esul in low-quali y documen a ion. This is
a po en ial p oblem in medical de ice de elopmen , as documen a ion is a c ucial pa o he
p oduc ce i ica ion p ocess. O en, he gene a ion o unc ional bu simpli ied p o o ypes can
be con using o he clien as hey can hink ha hei de elopmen is almos eady in ad ance.
This me hodology equi es good communica ion wi h he clien so ha hey unde s and he
cu en s a us o he p oduc as well as he emaining phases o he de elopmen .
Like he i e a i e p ocess, i is especially in e es ing o he de elopmen o g aphical use
in e aces. Th ough p o o yping, he use can expe ience ea ly in he de elopmen s ages how
he in e ace will look and make sugges ions o changes. I is also e ec i e when he echnical
solu ion is no clea ; p o o yping helps o minimise exis ing unce ain ies.
3.2. Agile Me hodologies
The o igin o Agile me hodologies da es back o 1968. This yea , a name was gi en o
he cos o e uns and quali y de iciencies ha we e being su e ed in di e en so wa e
de elopmen s [
36
]. A ha ime, he e was a g owing awa eness ha he equi emen s
we e cons an ly changing in p ojec s. Since hen, new me hodologies ha e eme ged o
wo k in dynamic and changing en i onmen s. Likewise, hese me hodologies assume ha
he co e o he p ojec s is he people who mus be in ol ed in he execu ion o deal wi h
unexpec ed e en s.
The e o e, Agile me hodologies we e de eloped o add ess he huge amoun o bu eau-
c acy ha adi ional me hods ha e o deal wi h. Agile me hodologies a e no documen a-
ion o de elopmen -planning o ien ed. The ac ha hey do no dedica e a huge e o
o planning makes hese me hodologies easily adap able o changes. In addi ion, hese
me hods a e people-o ien ed and no p ocess-o ien ed, as hey do no ocus on de eloping
p ocesses ha wo k o he eam; hei ole is jus o suppo he eam [37].
Senso s 2023,23, 2578 8 o 30
In 2001, se e al agile design expe s c ea ed he Agile Alliance, a non-p o i o ganisa-
ion o p omo e agile de elopmen and suppo o ganisa ions ha wan ed o implemen
hese me hodologies [
38
]. As a i s s ep, his alliance d a ed he Agile Mani es o. This
mani es o is de ined o p omo e be e ways o de eloping so wa e. Al hough Agile was
c ea ed o so wa e de elopmen , he philosophy p omo ed by his mani es o can be
ex ended o any o he p oduc . To his end, i de ines ou co e alues and 12 p inciples on
which his philosophy is based [39].
Agile de elopmen me hodologies ha e se e al concep s ha cons i u e hei co e. Fo a
be e unde s anding o di e en agile amewo ks, he main e ms a e b ie ly de ailed [40].
•
Inc emen al and I e a i e De elopmen : his means ha each i e a ion o p oduc
de elopmen is unc ional and adds new unc ionali ies o he p oduc .
•
Backlog: i is a lis o de elopmen s (new ea u es, changes, co ec ions, e c.) o be
implemen ed.
• Use S o ies: lis o p oduc equi emen s.
•
Daily Mee ing: he eam holds a daily mee ing o iden i y p oblems and es ablish
co ec i e measu es.
•
Re ospec i e Miles one: om ime o ime, o a he end o he p ojec , all eam
membe s spend a day analysing he mos signi ican e en s ha ha e occu ed du ing
he de elopmen o he p ojec .
3.2.1. Sc um F amewo k
Sc um is one o he mos ex ended agile amewo ks. I has i s o igin in a s udy o new
de elopmen p ocesses used o success ul p oduc design in Japan and he Uni ed S a es [
41
].
These de elopmen s we e based on e y gene ic and inno a i e equi emen s and had a e y
sho ime o ma ke . The Sc um me hodology ocuses on expe ience-based lea ning and sel -
o ganisa ion o add ess p oblems and e lec ion on wins and losses. Al hough i is conside ed
an agile p ojec managemen ool, his amewo k includes mee ings and u ili ies ha help
eams o s uc u e and manage wo k. The main elemen s o Sc um a e [42]:
• Backlog managemen : O ganisa ion o ac i i ies by he p oduc owne is equi ed.
• Planning: O ganisa ion o he i ems o be add essed du ing he i e a ion (Sp in ).
•
Sp in : A pe iod in which he eam wo ks oge he o achie e a de elopmen miles one.
•
Daily Sc um mee ing: A daily mee ing whe e ask acking is comple ed. Tasks a e
moni o ed h ough a dashboa d whe e he eam has a isual o e iew o he wo k.
This dashboa d p esen s he lis o use s o ies and he s a us o di e en sub- asks
classi ied as o do, in p og ess and done.
•
Sp in e iew: A he end o du ing he execu ion o he sp in , he eam mee s o
e iew he achie ed inc emen .
•
Sp in e ospec i e: A he end o he sp in , he eam mee s o assess and sha e wha
wen igh and wha wen w ong wi hin he i e a ion.
Sc um has oles and esponsibili ies. Typically, a eam has be ween i e and 15 mem-
be s, including he P oduc Owne , he Sc um Mas e and he de elopmen eam [
43
]. The
P oduc Owne is in cha ge o op imising and maximising he p oduc ’s alue. Likewise, i
is in cha ge o he P oduc Backlog and is he link be ween he eam and i s s akeholde s.
The P oduc Owne mus iden i y and clea ly de ine he objec i es in each sp in . The
Sc um Mas e is esponsible o ensu ing he Sc um is ca ied ou co ec ly. The e o e, i is
esponsible o managing he Sc um p ocess and he p oblems ha may a ise all along he
p ocess. The de elopmen eam consis s o se e al p o essionals who a e in ol ed in he
de elopmen o he p oduc . The wo king eam c ea es he inc emen o each sp in . In
Figu e 5, he Sc um wo k low is p esen ed.
Senso s 2023,23, 2578 9 o 30
Figu e 5. Sc um wo k low.
Agile me hodologies, pa icula ly Sc um, cons i u e a use ul ool o s a -ups as his
me hodology o e s ools ha quickly answe cus ome needs. I also helps he eams o
sel -manage o c ea e simpli ied p o o ypes. On he o he hand, Sc um equi es expe ienced
manage s o apply he me hod o be e ec i e. In addi ion, his me hodology is no easy o
in eg a e wi h he classical p ojec managemen app oach usually employed in medical
de ice de elopmen . This cha ac e is ic may make his me hodology comple ely sui able
o de eloping medical de ices.
3.2.2. Kanban F amewo k
Kanban is an agile p oduc de elopmen amewo k. I was de ined in 1940 by he Toyo a
enginee Taiichi Ohno. He de eloped a sys em o con olling supply chain s ocks [
44
]. This
amewo k is based on he philosophy o con inuous imp o emen , quali y assu ance, was e
educ ion and lexibili y. I aims o manage de elopmen lows in a isual way. To do so, i
elies on dashboa ds [45]. In 2007, Mic oso employee Da id J. Ande son o mula ed he ou
p inciples and six basic p ac ices o Kanban [46] aligned wi h he Agile Mani es o.
In e ms o oles, wo main oles a e de ined: Se ice Reques Manage and Se ice
Deli e y Manage [
47
]. The Se ice Reques Manage is esponsible o iden i ying cus-
ome expec a ions and needs. I is also esponsible o selec ing and p io i ising he wo k
i ems. The Se ice Deli e y Manage is esponsible o he wo k low and mus acili a e
he Kanban p ocess.
Like Sc um, his amewo k o e s signi ican ad an ages o s a -ups. I can manage
a con inuous low o wo k inpu . I suppo s wo k inpu a any ime, e en wi h an ongoing
ask. This app oach is mo e app op ia e o eam membe s wi h wo k en ies ha a y in
scope and p io i y. I also suppo s main enance and suppo asks. On he o he hand,
Kanban is no a e y s uc u ed me hod, so i is ha de o implemen his amewo k in a
company whe e employees a e no e y expe ienced. Mo eo e , i does no i p ojec s ha
equi e a high deg ee o p edic abili y and ully de ined planning.
3.2.3. C ys al F amewo k
C ys al is a amewo k amily o agile de elopmen ocused on people and hei
in e ac ions. This me hodology was de ined in 1991 by Alis ai Cockbu n, c ea o o he
Agile Mani es o. Speci ically, he w o e i s i s de ini ion o IBM [
48
]. This me hodology
pu sues indi idual imp o emen o achie e he o e all imp o emen o he eam. I ocuses
mainly on people, in e ac ion, communi y, skills, alen , and communica ion. The p ocess
low s a s om an episode. Episodes a e small de elopmen s ha a e he basis o di e en
componen s. Toge he , hese episodes o m an In eg a ion. I e a ions a e eleased on a
daily o weekly basis. Once he di e en i e a ions a e inished, he p ojec is in eg a ed,
e i ied, and deli e ed [49].
Senso s 2023,23, 2578 16 o 30
4.3. Phase 1—De elopmen Feasibili y
In his phase, he idea o concep o be de eloped is esea ched and de ined by
conduc ing se e al p oo s o concep . As men ioned abo e, he de ini ion o he in ended
use and he isk analysis o he de ice is essen ial o de e mine he applicable egula ion.
The e o e, du ing his phase, he asks and app oaches equi ed o de ine he in ended
use and minimise unce ain ies o po en ial isks mus be execu ed. Typically, hese es s
a e ela ed o he main cha ac e is ics o he u u e medical de ice. Wi hou he success ul
implemen a ion o such ea u es, he de ice could no usually be launched on he ma ke .
Figu e 10 p esen s he equi ed inpu s o he execu ion o his phase, he use cases o he
de elopmen and he gene a ed ou pu s.
Figu e 10. De elopmen Feasibili y phase: key cha ac e is ics, inpu s and ou pu s.
As a s a ing poin , i is common o ha e a gene al idea o he de elopmen , which is
usually ela ed o he measu emen p inciple o senso isa ion s age o he u u e medical
de ice. Howe e , he e is a ely a conc e e echnical idea o how o sol e i . In some cases,
he e is a sligh idea ha he inal solu ion will be an embedded sys em wi h di e en
pe iphe als such as came as, an ennas, senso s ages, hea e s, ligh ing sys ems, e c. Usually,
sol ing he measu emen o moni o ing p inciple is possible, bu i s echnical easibili y
is no gua an eed. The e o e, du ing his phase, i is in ended o de ine and cla i y he
pa ame e s o be moni o ed o con olled o diagnosing o ea ing a physical condi ion
o disease.
Hence, his phase should include hose es s o p oo s o concep needed o o e come
he main unce ain ies o he p ojec —pa icula ly hose ha could make he u u e p oduc
un easible. The e o e, he esul ing p o o ypes will be used o wo pu poses. On he one
hand, hey will help o minimise he echnical unce ain ies aced by he de elopmen eam.
Fo example, o cla i y conce ns ela ed o speci ic pa ame e s o embedded sys ems, such
as pe o mance o he a ailable ha dwa e, eliabili y o sensing s ages, maximum la ency,
he accu acy o a ouch panel, e c.
On he o he hand, p o o ypes can be used o allow he end use o make high-le el
decisions on he concep . I he e is no end-use access, his ole is o en gi en o he p oduc
manage . Fo example, suppose a cus ome wan s o in oduce a ba code eade . The di e en
ypologies will be analysed and es ed o selec he bes o sui he cus ome ’s needs. Suppose a
ouch panel is o be in oduced, bu i s echnology needs o be cla i ied. The cus ome mus
ha e di e en minimum iable p o o ypes o e i y capaci i e and esis i e panels. This way,
cus ome eedback can be ob ained o de ine he bes echnical solu ion.
The iden i ied asks will be lis ed and speci ied, each execu ed by a specialis allowing
pa allel execu ion o some o he asks. Howe e , he easibili y will be alida ed so ha
he p ojec manage will os e communica ion be ween eam membe s.
4.3.1. Deli e able: De elopmen Feasibili y Repo
Du ing his phase, he de elopmen easibili y documen will be gene a ed. The pu -
pose o his documen is o c ea e enough in o ma ion o decide whe he he de elopmen
is easible. This documen should assis in e alua ing echnical, economic and ma ke
easibili y. Al hough his me hodology only con empla es he design and de elopmen
Senso s 2023,23, 2578 17 o 30
phases and excludes he business o ma ke ha he u u e de ice may ha e, i has o
gene a e in o ma ion so ha he clien o p oduc manage s can decide on hese aspec s.
The in o ma ion included in he de elopmen easibili y is summa ised below:
•
Use cases: A i s app oach o he use cases, he main use cases should be iden i ied
and w i en in as much de ail as possible.
•
Unce ain ies and po en ial isks: Based on he in o ma ion p o ided in he use cases,
po en ial isks and unce ain ies o be o e come mus be iden i ied a he beginning o
he p ojec .
•
Planning and scope: Once he s a ing poin , unce ain ies and use cases a e known,
he scope o he phase mus be de ined and planned. The accep ance and e iew o
his poin by he clien a e essen ial, as i helps o ensu e a sha ed de elopmen ision.
•
Technical easibili y esul s: This sec ion will include he es s’ esul s and he main
conclusions on echnical easibili y. This in o ma ion mus be clea and p ecise.
•
Legal easibili y: In o ma ion ega ding any con lic be ween he p oposed solu ion
and an al eady egis e ed in ellec ual p ope y should also be included.
•
Ma ke analysis: The eam should sea ch o simila de ices al eady a ailable on he
ma ke . The echnical solu ion and i s cos will be analysed.
•
Economic analysis: A i s app oxima ion o he uni cos o he de ice and he cos o
p oduc de elopmen (phase 2 and phase 3) should be made.
4.3.2. De elopmen Feasibili y Checkpoin
Once he easibili y phase has been execu ed, he p ojec manage mus deli e he
associa ed deli e ables and p esen he mos ele an conclusions o he clien . A his
poin , a decision has o be made on whe he o s a he de elopmen o he i s in eg a ed
p o o ype o he u u e p oduc . This decision usually in ol es uppe managemen , who
ypically ha e absolu e con ol o e he ac i i y. In addi ion, he clien company mus ha e
o he inpu s om di e en depa men s, such as inance o sales, o inal app o al.
4.4. Phase 2—Inc emen al and I e a i e P o o yping
A e cla i ying he unce ain ies o he p ojec , i is possible o s a wi h he Inc e-
men al and I e a i e P o o yping phase. This phase aims o design unc ional p o o ypes
ha answe o use cases and equi emen s de ined by he clien . As a esul , a ully unc-
ional and in eg a ed p o o ype will be a ailable. Howe e , i will be pa ially e i ied and
documen ed. The inpu s and ou pu s o his phase a e p esen ed in Figu e 11.
Figu e 11. Inc emen al and I e a i e p o o yping phase: key cha ac e is ics, inpu s and ou pu s.
To his end, he design and de elopmen p ocesses use an Agile me hodology based
on he i e a i e c ea ion o inc emen al p o o ypes. Inc emen al de elopmen is p oposed
o add ess he lack o p ecise equi emen s and o allow he in oduc ion o equi emen s
and changes in each i e a ion. In his way, i seeks o educe he echnical and inancial isks.
An i e a i e model is p oposed o allow he clien o assess he sui abili y o he app oach
a he end o each i e a ion. The Agile amewo k o he p oposed model o phase 2 is
p esen ed in Figu e 12.
Senso s 2023,23, 2578 18 o 30
Figu e 12. P oposed Agile me hodology amewo k.
This phase is based on he adap a ion o he main cha ac e is ics o agile me hodologies.
The key aspec s a e de ailed as ollows:
•
Inc emen al and i e a i e de elopmen : The me hodology p oposes an inc emen al
and i e a i e de elopmen o he di e en unc ionali ies o he u u e p oduc . I
s a s wi h hose ha p o ide he mos ou s anding alue and a e iden i ied, analysed
and de eloped in a pa allel way. Once he gene a ed ou pu has been e alua ed wi h
he clien , i e a ions a e ca ied ou un il he desi ed unc ionali y is comple ed.
•
Roles: Th ee main oles will be de ined: he p oduc manage o clien , he p ojec
manage and he de elopmen eam. The p oduc manage will de e mine he inpu
equi emen s o he second phase. I will also de ine he p ojec backlog and KPIs, he
i e a ion backlog and he e ospec i e mee ing o each i e a ion. The p ojec manage
will accep he equi emen s p oposed by he p oduc manage , manage he p ojec
and i e a ion backlog and de ine he KPIs. I will also coo dina e he i e a ion ollow-
up, e iew and e ospec i e mee ings. The de elopmen eam will unde ake he
echnical ac i i ies and pa icipa e in he i e a ion planning, he ollow-up mee ings,
he de ini ion o he KPIs and he e iew mee ing o each i e a ion.
•
Key Pe o mance Indica o s (KPIs): KPIs will be de ined o gua an ee he co ec
p og ess o he p ojec . They will help objec i ely measu e he de elopmen o he
p ojec . Two g oups o KPIs will be es ablished, one o he p ojec and he o he o
he i e a ion. The p ojec KPIs will be de ined du ing a mee ing be ween he p ojec
manage and he clien o p oduc manage . On he o he hand, he i e a ion KPIs will
be pa ame e s ha will be de ined and measu ed be ween he p ojec manage and
he eam membe s. The p ojec KPIs will be e alua ed in he e ospec i e mee ings
be ween he p ojec manage and he clien . On he o he hand, he upda e o he
i e a ion KPIs will ake place du ing he ollow-up mee ings and hei e alua ion
du ing he i e a ion e iew mee ings.
•
P ojec backlog and use s o ies: A lis o all he ac i i ies o be unde aken h oughou
he p ojec is a ailable. These ac i i ies will be ca ied ou in se e al i e a ions o
he p oposed model. Each ac i i y o be execu ed will be desc ibed, p io i ised, and
ca ego ised acco ding o he unc ional block o which i belongs. The in o ma ion
abou each ac i i y will be known as a use s o y, and he p ojec manage and he
p oduc manage will be esponsible o comple ing and upda ing i .
•
I e a ion planning and i e a ion backlog: A he beginning o each i e a ion, he
ac i i ies o be de eloped and he deadlines a ailable o hem will be de ined. The
ac i i ies execu ed du ing an i e a ion will be iden i ied as he i e a ion backlog. The
p oduc manage and he p ojec manage will decide on he backlog o each i e a ion.
Du ing his mee ing, he in oduc ion o possible changes o he es ablished plan will
be e alua ed. I d as ic changes a e iden i ied, he whole eam will ha e o analyse he
Senso s 2023,23, 2578 19 o 30
impac and decide whe he i is easible o unde ake hem. The p ojec manage will
be in cha ge o dis ibu ing he asks among he eam membe s. Howe e , all o he
eam will be in ol ed du ing he planning p ocess.
•
Follow-up mee ing: Two mee ings will be held wice a week o discuss he p og ess
o he asks. In hese mee ings, he eam will b ie ly commen on he s a us o each
de elopmen and, i any, will explain he p oblems encoun e ed. These mee ings
a e in ended o keep he whole eam awa e o he p og ess o he de elopmen ,
upda e KPIs and ake co ec i e ac ions o ensu e ha he de elopmen is ca ied ou
acco ding o plan. Addi ionally, hese mee ings will help o p omo e communica ion
be ween he di e en membe s o he eam. The p ojec manage will be esponsible
o coo dina ing his mee ing. A digi al dashboa d will be used as a suppo ool
whe e he eam will upda e he s a us o hei asks. The dashboa d will p esen ca ds
wi h he p io i ised and ca ego ised use s o ies, he s a us o each ask, da es and
esponsible pe sons. Figu e 13 shows he p oposed dashboa d o ma .
Figu e 13. P oposed Agile me hodology dashboa d.
•
I e a ion e iew: A e each i e a ion, a mee ing will be held o e iew he comple ion
o he asks assigned o ha i e a ion. I some o he ac i i ies s ill need o be comple ed,
hese should be e-planned in a subsequen i e a ion. In addi ion, du ing his mee ing,
he execu ion o he i e a ion will be e alua ed, and eedback om he whole eam
will be collec ed. I necessa y, co ec i e ac ions will be aken o imp o e he ollowing
i e a ions and ensu e con inuous imp o emen . Du ing his mee ing, he p og ess o
he i e a ion KPIs will also be e iewed. The p ojec manage and he de elopmen
eam will pa icipa e in his mee ing, and he p ojec manage will be esponsible o
coo dina ing i .
•
I e a ion Re ospec i e: A e e iewing he p og ess o he i e a ion in e nally (p ojec
manage and eam membe s), he conclusions and ac ions se will be communica ed
o he p oduc manage o clien . The esul s will hen be e iewed wi h he p oduc
manage , and he p og ess o he p ojec KPIs will be assessed.
4.4.1. O e all O e iew o he P oposed Model and I s Deli e ables
This sec ion aims o desc ibe he p ocesses o he p esen ed model as well as i s
execu ion low. Al hough i is ep esen ed in a V-shape and no in a ci cula way, his
model con empla es i e a ions o be able o change o add new equi emen s, speci ica ions,
design o implemen a ion du ing i s execu ion.
In he case o a change in a use equi emen , he en i e V-model has o be e- un. On
he o he hand, i he change a ec s a so wa e o ha dwa e speci ica ion, he speci ica ion,
design, implemen a ion, and e i ica ion phases mus be execu ed, including e iewing he
e i ica ion plans and hei execu ion. When he change in ol es a design modi ica ion, a
Senso s 2023,23, 2578 20 o 30
e iew o he de elopmen e i ica ion plan and he execu ion o he design, implemen a-
ion and e i ica ion phases shall be pe o med. Finally, i he implemen a ion changes, he
implemen a ion and e i ica ion phases mus be execu ed. This me hodology, h ough he
execu ion o pa ial i e a ion loops, seeks o acili a e he in oduc ion o changes du ing
de elopmen and a e he p oduc ’s elease. The model can be seen in Figu e 9.
Al hough he main objec i e o his phase is no o ensu e compliance wi h he medical
egula ions, he p oposed model and he gene a ed deli e ables a e de ined o be ully
complian a e he execu ion o phase 3.
The p ocess s a s wi h he de ini ion o he P ojec De elopmen Plan, which will
de ine he p ocess o be ollowed du ing he execu ion o he p ojec . Then, aking as a
s a ing poin he Use Requi emen Speci ica ion (URS), which e e s o he de ini ion o
he unc ional and no ma i e equi emen s, he P ojec T ans e ence Plan will be de ined.
This plan con empla es how he p ojec ans e will be ca ied ou , he p ojec accep ance
c i e ia and he de ini ion o he es s ha he de elopmen eam s ill needs o execu e.
These es s mus be pe o med by he clien , p oduc manage o ex e nal eam membe s
du ing phase 3.
Likewise, he ans e ence documen mus conside when he clien will ha e an
ou pu o he de elopmen o e alua e i . This me hodology p oposes gene a ing a se o
deli e ables o each i e a ion o he me hod. These deli e ables will se e o assess he
p og ess o he de elopmen and cla i y echnical unce ain ies.
Then, knowing he URS and he use cases o he u u e p oduc , he isks o he p oduc
a e analysed. The isk analysis and he URS will be he s a ing poin o de ining he p ojec
speci ica ions: So wa e Requi emen Speci ica ion (SRS) and Ha dwa e Requi emen
Speci ica ion (HRS). Once his de ini ion is a ailable, he So wa e and Ha dwa e es s o
he Func ional Ve i ica ion mus be de ined. These es s will e i y each o he de ined SRS
and HRS. A con ol miles one will e i y ha bo h he de ini ion o speci ica ions and he
de ini ion o he associa ed es s ha e been ca ied ou co ec ly.
A e he speci ica ion phase, he design phase ollows. Each HRS and SRS mus
be ansla ed in o a design, a So wa e Design Speci ica ion (SDS) and Ha dwa e Design
Speci ica ion (HDS). In addi ion, hese design speci ica ions mus be e i ied by So wa e
and Ha dwa e De elopmen Tes s, so he es plan mus be de ined a his poin .
Once he design has been made and he associa ed es de ined, a con ol miles one
mus be se o e i y ha p og ess is as expec ed. Once he con ol miles one has been
passed, so wa e coding and ha dwa e componen manu ac u ing can p oceed.
A e he implemen a ion, he de ined e i ica ion plans mus be execu ed, i s he
De elopmen Ve i ica ion Tes s, hen he Func ional Tes s, and inally he T ans e ence Tes s.
In addi ion, wo ans e sal p ocesses mus also be conside ed. On he one hand,
Con igu a ion Managemen de ines how each p ojec componen is o med. On he o he
hand, he Change Con ol documen is de ined, which collec s he changes du ing he
design and de elopmen phase as well as a e he elease o he p oduc .
Rega ding deli e ables, each phase desc ibed p e iously has a leas one ou pu ha
eco ds he ac i i ies pe o med. As he medical de ice egula ion speci ies, each s ep o
he design and de elopmen p ocesses mus be planned and documen ed; he e a e a lo o
plans and eco ds among he documen a ion de ined wi hin his me hodology.
The documen a ion gene a ed in his phase will be he ini ial e sion o he inal
p oduc documen a ion. Al hough he documen a ion e o is minimised, i should be gen-
e a ed as he de elopmen p og esses. Howe e , all he in o ma ion will be consolida ed,
and he inal p oduc documen a ion will be gene a ed in phase 3.
4.4.2. Inc emen al and I e a i e P o o yping Checkpoin
Phase 2 ends when he V-model is ully i e a ed wi h all ac i i ies o he p oduc
backlog. A e his execu ion, he checkpoin o ga e o phase 2 mus be execu ed. A his
poin , i is e alua ed whe he he es ablished objec i es ha e been achie ed. Addi ionally,
i is decided whe he o no o con inue wi h he execu ion o he de elopmen and mo e
Senso s 2023,23, 2578 21 o 30
on o phase 3 o consolida e he medical p oduc . This decision is usually made by he clien
o p oduc manage and he company’s execu i e eam. The uppe managemen usually
akes in o accoun echnical, economic and ma ke aspec s when making he decision.
4.5. Phase 3—Medical P oduc Consolida ion
The hi d s age o he me hodology aims o consolida e he de elopmen and u n i
in o a medical p oduc . To his end, he deli e ables gene a ed du ing phase 2 a e used as
inpu . In his phase, in ensi e e i ica ion is ca ied ou o consolida e and alida e bo h
he de elopmen and he gene a ed documen a ion. Inpu s and ou pu s gene a ed in his
phase a e p esen ed in Figu e 14.
Figu e 14. Medical P oduc Consolida ion phase: key cha ac e is ics, inpu s and ou pu s.
Al hough a ully unc ional design is a ailable as an inpu o his phase, i is o
be expec ed ha he clien o he p oduc manage will wan o in oduce changes o
imp o emen s ha ha e been iden i ied a e he deli e y o phase 2. Likewise, o alida e
he de elopmen , he design mus conside aspec s ela ed o i s indus ialisa ion. In his
phase, he ollowing asks will be unde aken:
•
Mino modi ica ions o imp o emen s: E en i he main de elopmen is comple ed,
mino changes o imp o emen s mus be accep ed du ing his phase, such as changes
in he colou s o he g aphical use in e ace, solu ions o minimise isks iden i ied
a e phase 2 de elopmen , e c.
•
Indus ialisa ion- ela ed unc ionali y: Du ing his phase, equi emen s ela ed o
he indus ialisa ion o he p oduc will be added. Fo his, i will be necessa y o
in ol e he p oduc ion depa men o , in he case o ou sou cing he indus ialisa ion
o he p oduc , he Elec onic Manu ac u ing Se ices (EMS) company ha will be
in cha ge o his ac i i y. The indus ialisa ion equi emen s will be conside ed an
addi ional use case o he exis ing ones. The e o e, indus ialisa ion equi emen s will
be added o he URS o he p oduc and will be conside ed in he SRS/HRS, SDS/HDS,
implemen a ion and e i ica ion phases. In addi ion, he p ojec de elopmen plan
mus be upda ed o indica e how his s age will be unde aken.
•
In ensi e e i ica ion and alida ion o he de ice: An exhaus i e e i ica ion o he
p oduc will be ca ied ou ; his e i ica ion mus co e 100% o he unc ionali y
de eloped by he de elopmen eam. The alida ion o he de ice is also conside ed
du ing his phase.
•
P oduc elease: The p ojec plan should con empla e how he p oduc elease and
upda es will be pe o med once he de ice is on he ma ke .
4.5.1. O e all O e iew o he P oposed Model and I s Deli e ables
In his phase, i is p oposed o ollow a V-model simila o he one p esen ed in phase 2.
Unlike phase 2, an Agile, I e a i e and Inc emen al model is no conside ed. Ins ead, a
sequen ial execu ion o he V-model is p oposed. This will ease p oduc ce i ica ion by
egula o y bodies since he e e ence s anda ds sugges he de elopmen o medical de ices
ollowing he adi ional V-model. Compa ed o he V-model p esen ed in phase 2, he only
di e ence is ha he ans e ence s age becomes a alida ion s age.
Senso s 2023,23, 2578 22 o 30
The p ocess s a s wi h he upda e o he P ojec De elopmen Plan gene a ed in phase 2.
This plan mus include how p oduc indus ialisa ion, alida ion and elease will be add essed.
Simila ly, he oles and scope o p ocesses should be upda ed whe e necessa y.
Then, he URS mus be upda ed wi h he use cases o be implemen ed o unde ake
he indus ialisa ion phase and he changes eques ed by he clien o p oduc manage .
Once he URS has been upda ed, he alida ion plan should be gene a ed; his plan will
co e he alida ion o all he de ined URS. Tes s ela ed o clinical e alua ion and esea ch
o pe o mance e alua ion and pe o mance s udies a e conside ed a his s age. Likewise,
any es ing ha applies o he p oduc acco ding o he IEC 60601 amily o s anda ds o
o he s mus be pe o med in acc edi ed en i ies.
The isks o he p oduc a e hen e-analysed, and, i necessa y, app op ia e con ol
measu es a e aken. Once he isk analysis has been pe o med, he so wa e and ha dwa e
speci ica ion s ages a e ca ied ou . This phase mus add ess new unc ionali ies and use
cases ela ed o indus ialisa ion. A e he speci ica ions a e p ecise, he ha dwa e and
so wa e’s unc ional and en i onmen al e i ica ion plan is de ined. Based on his, he
speci ica ion checkpoin mus be execu ed.
Subsequen ly, he high-le el design and de ailed ha dwa e (HDS) and so wa e (SDS)
design a e pe o med. The de elopmen e i ica ion plan mus also be de ined. The
de elopmen p og ess is hen e i ied using he design checkpoin . This is ollowed by
implemen ing he added unc ionali y, bo h so wa e and ha dwa e. A e he implemen a-
ion, he de ined e i ica ion plans mus be execu ed, i s he de elopmen plan, hen he
unc ional plan, and inally, he alida ion plan.
Finally, as in phase 2, con igu a ion managemen and change con ol p ocesses mus
be ca ied ou . Rega ding phase 3 deli e ables, all o hem a e p esen ed in Figu e 15.
Figu e 15. Deli e ables associa ed o he phase 3.
4.5.2. Medical P oduc Consolida ion Checkpoin
The de elopmen ends when he p oposed V-model is ully execu ed. A e wa ds,
he checkpoin o con ol ga e o phase 3 mus be comple ed. A his checkpoin , i will be
decided i he design and de elopmen ha e been success ul and whe he o no o mo e
on o he nex phase. This decision is made using in o ma ion and p o o ypes gene a ed
du ing he design and de elopmen phases, as well as o he ex e nal elemen s ha help o
assess he easibili y o comme cialising he p oduc . Usually, ma ke in o ma ion, eedback
om po en ial use s, e c., a e used as inpu . I he assessmen is posi i e, he p ocess o
egis a ion and ce i ica ion o he de eloped de ice wi h he no i ied bodies mus be
Senso s 2023,23, 2578 23 o 30
ca ied ou . This decision is usually aken by he company’s uppe managemen ha owns
he designed medical de ice.
5. Me hodology Valida ion
A e p esen ing he me hodology, his sec ion aims o alida e he p oposal. On he
one hand, he di e en use cases in which his me hodology has been success ully applied
a e de ailed. Fo each o hem, he phases o he me hodology ha ha e been applied
a e speci ied. Howe e , mos o he use cases a e associa ed wi h indus ial clien s, so o
con iden iali y easons, he desc ip ion o hese use cases is w i en in a gene al way wi hou
going in o echnical o clien -speci ic de ails. Ne e heless, he mos ele an in o ma ion
o alida e he me hodology is p esen ed. Likewise, he use case o a wea able, whose
de elopmen has been ca ied ou ollowing he p oposed me hodology, is de ailed in mo e
dep h. Simila ly, i is epo ed ha he me hodology has been implemen ed in Teknike ,
whe e hese p ocedu es ha e been audi ed du ing he ISO 13485 ce i ica ion p ocess.
5.1. Use Case 1: Medical De ice—Wea able De ice Senso
The wea able solu ion in ol es i al signs moni o ing pla o m in he o m o a
sma w is band, which can collec ele an da a abou he use ’s heal h. Cu en ly, many
sma wa ches o b acele s moni o i al signs. S ill, mos o hem a e no de eloped o
comply wi h medical de ice egula ions, so he da a hey p o ide canno be conside ed
eliable. The di icul y in ol ed in he p ocess o alida ion and ce i ica ion o medical
de ices means ha manu ac u e s do no ce i y hem as such and ins ead add disclaime s
on hei p oduc s indica ing ha hey a e no diagnos ic de ices. This de elopmen aims o
p o ide a w is band ha o e s eliable diagnosis and accu a e esul s. This is achie able as
he p oposed me hodology allows us o add ess in a clea and s uc u ed way he echnical
and egula o y equi emen s ha his ype o de ice has o ace. In e ms o i s ca ego y, i
is a de ice classi ied by MDR as IIb and IEC 62304 as class B.
The sys em uses Blue oo h communica ion o moni o i al signs and o he me ics
emo ely. In his way, i p o ides heal hca e specialis s wi h enough in o ma ion o p e en
and de ec possible illnesses o acciden s in pa ien s who a e no in a con olled en i on-
men , such as a hospi al. The de ice inco po a es cu ing-edge, low-cos and low-powe
echnology. I is designed o be use - iendly, and a ully au oma ed measu emen sys em
equi ing minimal use in e ac ion.
Phases 1 and 2 o he p oposed me hodology ha e been ully implemen ed in his de elop-
men . Howe e , phase 3 is s ill in p og ess. The de elopmen is in he alida ion phase, whe e
usabili y es s ha e been ca ied ou in a eal en i onmen , namely in a nu sing home o he
elde ly. Clinical ials and he ce i ica ion p ocess o he de ice a e s ill pending.
5.1.1. Me hodology Phase 1—De elopmen Feasibili y
The implemen a ion o he me hodology s a s wi h he execu ion o phase 1. Fi s ly, he
exis ing echnologies and solu ions o hese ypes o de ices a e e iewed, and he c i ical
elemen s a e iden i ied: he measu emen subsys em, in pa icula he measu emen o oxygen,
hea a e and he pe o mance o elec oca diog ams. A e his, he i s app oxima ion o
he solu ion is pe o med o clea he unce ain ies o he measu emen subsys em.
The di icul y o measu ing hese signals means ha he i s phase ocuses on alida -
ing he measu emen easibili y o he Pho ople hysmog aphy (PPG) and Elec oca dio-
g aphy (ECG) p ocesses. As a echnical solu ion, op ical PPG is p oposed, as i makes i
possible o measu e bo h oxygen and hea a e. I he essels a e illumina ed, he amoun
o e lec ed ligh is p opo ional o he oxygen and hea a e alues. Using he ECG,
eco ding he hea ’s signals is possible, o which elec odes a e necessa y.
This sys em’s easibili y e i ica ion is ca ied ou wi h a i s elec onics p o o ype,
including he sensing s age. In addi ion, as he housing is pa icula ly ele an o ligh
emission and ECG pe o mance, a 3D-p in ed e sion o he housing is used o alida e he
concep . Figu e 16 shows he i s p o o ype o alida e he measu emen p inciple.
Senso s 2023,23, 2578 24 o 30
Figu e 16. Fi s p o o ype o alida e easibili y.
The ini ial esul s ob ained we e no sa is ac o y. On he one hand, o he PPG, when
he in ensi y o he emi ed ligh was high, he housing could no isola e he LED channels
om he pho odiodes. The e o e, he need o space s be ween he pho odiodes was
iden i ied o isola e he ligh om he LEDs u he . In addi ion, he ecei ed signal was oo
weak due o he housing hickness, which was oo hick o he pho odiodes o be in di ec
con ac wi h he skin. Fo all hese easons, i was decided o use a Te lon shee o simula e
he isola ion ha should exis in he inal housing be ween he di e en LED channels. A
p o isional PCB assembly was hen made. A e es ing, i was concluded ha using wo
LED/pho odiode combina ions was enough.
In he case o he ECG, al hough he design allowed ob aining he signal om he hea ,
i was oo weak. The e o e, i was concluded ha his was due o he a ea o he elec odes
being oo small. This hypo hesis was alida ed by di ec ly welding la ge elec odes. The
esul s ob ained we e sa is ac o y. Figu e 17 shows he un il e ed PPG and ECG alues.
Once he p ojec manage and p oduc manage ha e alida ed he esul s, phase 2 o he
de elopmen p oceeds.
Figu e 17. Measu emen s made wi h PPG and ECG senso .
5.1.2. Me hodology Phase 2—Inc emen al and I e a i e P o o yping
Following phase 2 o he p oposed me hodology, he unc ional de elopmen o he
de ice is ca ied ou inc emen ally and i e a i ely.
As a esul o he inc emen al and i e a i e de elopmen o he unc ionali y, a sma
b acele designed o he emo e moni o ing o he main i al signs in elde ly o dependen
pa ien s in he home en i onmen is ob ained. This de ice is equipped wi h embedded
elec onics o pe o m pho ople hysmog aphy (calcula ion o hea a e and blood oxygen
sa u a ion), lead I elec oca diog aphy (be ween le and igh hand), and moni o body
empe a u e and physical ac i i y.
Measu emen s a e au oma ically aken egula ly wi h minimal pa ien in e en ion,
making i as simple as possible. Pa ien s place hei igh hand on he de ice when p omp ed
Senso s 2023,23, 2578 25 o 30
by he wea able o pe o m he elec oca diog am. The collec ed da a a e s o ed in he in e nal
memo y and can be downloaded h ough USB using he cha ging pla o m o h ough
Blue oo h communica ion. Table 2lis s he main echnical cha ac e is ics o he wea able.
Table 2. Wea able’s echnical speci ica ion.
Cha ac e is ic De ini ion
Use in e ace RGB LED and Buzze
Communica ion in e ace USB and Blue oo h 5.1 (BLE)
Ba e y 370 mAh (1 week)
In e nal lash memo y 4 Gb
Size 49 mm ×45 mm ×15 mm
Elec oca diog am In e ace 2 ea elec odes and 2 on elec odes
Pho ople hysmog aphy in e ace 1 Red LED, 1 In a ed LED, 1 g een LED and 2 pho odiodes
The elec onics o he de ice a e embedded in a squa e sphe e. The elec onics a e
di ided in o wo connec ed PCBs; one is used o he sensing s age, and he o he is used
o he con ol s age. Bo h PCBs a e held in he lowe case, while he ba e y is in he uppe
case. A con en ional, adjus able silicone s ap is used o as en i o he w is . As shown in
Figu e 18, he LED indica o and he on elec odes a e loca ed on he on o he de ice.
A he back o he de ice a e he ea elec odes used o he pho ople hysmog aphy (LEDs
and pho odiodes). The cha ging and se ial communica ion po is also loca ed on he back
o he w is band. Figu e 18 shows he loca ion o hese elemen s.
Figu e 18. F on and ea side o he de ice.
5.1.3. Me hodology Phase 3—Medical P oduc Consolida ion
Finally, he execu ion o phase 3 has begun, o which he V-model has been comple ed,
consolida ing all he de elopmen , e i ying each componen , and gene a ing he equi ed
documen a ion.
The de ice has been es ed o e i y he eliabili y o he measu emen esul s. Fi s ly,
he empe a u e senso ’s accu acy has been de e mined by empe a u e es s in a clima ic
chambe . Rega ding he SpO2 measu emen , a signal- o-noise a io measu emen was
pe o med by placing he de ice on he cha ging s a ion. This dock is designed o block
ex e nal ligh a e ac s and e lec he signal om he LEDs. In addi ion, bo h SpO2 and
ECG measu emen s ha e been e i ied using a calib a ed measu ing de ice. Angula speed
and linea accele a ion we e es ed by d i ing he de ice on he axis o a con olled mo o .
Finally, he inclina ion has been checked agains a calib a ed measu ing de ice.
The de elopmen is cu en ly in he alida ion phase. On he one hand, usabili y es s
ha e been ca ied ou on dependen and olde people li ing in an assis ed li ing acili y.
On he o he hand, en i onmen al, elec ical sa e y, and clinical ials, among o he s, a e
s ill pending. Those es s ha mus be pe o med in o icial ins i u ions a e s ill pending.
5.2. Use Case 2: Medical De ice o P o essional Use
This use case in ol es he use o he me hodology in de eloping a medical de ice o
p o essional use. The clien and owne o he de elopmen is a s a -up company ha does
no ha e enough echnical expe ise o de elop he p oduc en i ely. The e o e, hey decided
o ou sou ce pa o i . The clien ’s con ibu ion o he de elopmen is s ic ly limi ed o he
de ini ion o he algo i hm ha is he basis o he de ec ion pe o med by he de ice.
