**5. Conclusions**

In this work, an intrinsic optical fiber FPI-based sensor integrated in a 3D-printed case was developed and evaluated as a spirometry device to assess the respiratory health of individuals. To evaluate the air flow dynamics and the induced mechanical impact in the 3D-printed structure, a simulation study with Solidworks software was performed, validating the described theoretical approach.

To evaluate the suitability of the proposed system to perform spirometry, tests were executed using the proposed spirometer and, for comparison, a commercial unit. The shape of the flow–volume and volume–time curves obtained with the FPI-based system are as expected and show a good agreemen<sup>t</sup> with the ones obtained through the commercial spirometer. The pulmonary parameters obtained for the different tests can also be considered within the expected range, as the values of 4.40 L and 6.46 L, for the FEV1 and FVC parameters, respectively, with an FEV1/FVC index of 68.5%. Additionally, an average value of 5.35 L/s was found for the PEF.

**Author Contributions:** Conceptualization, M.F.D.; formal analysis, A.C.N. and M.F.D.; investigation, A.C.N.; methodology, A.C.N.; software, T.P.; supervision, P.A. and M.F.D.; validation, A.C.N. and N.A.; writing—original draft, A.C.N.; writing—review and editing, T.P., N.A., P.S.d.B.A., P.A. and M.F.D. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work is funded by FCT/MCTES through national funds and when applicable cofunded by EU funds under the UIDB/50008/2020-UIDP/50008/2020, UIDB/50025/2020, and UIDP/ 50025/2020 projects. This work is also funded by FCT/MEC through national funds and when applicable co-funded by the FEDER-PT2020 partnership agreemen<sup>t</sup> under the project UID/EEA/50008/ 2019.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Acknowledgments:** Ana Catarina Nepomuceno acknowledges the IT internal project NICE-HOME. M. Fátima Domingues and Nélia Alberto acknowledge the REAct (FCT-IT-LA) and PREDICT (FCT-IT-LA) scientific actions, respectively. Tiago Paixão acknowledge the Fundação para a Ciência e Tecnologia for the gran<sup>t</sup> with the reference PD/BD/128265/2016.

**Conflicts of Interest:** The authors declare no conflict of interest.
