Abstract
Introduction: Changes in ventilation/perfusion matching can be assessed by mainstream (MS) or sidestream (SS) capnography. While MS capnography is more accurate than SS, the instrumental dead space of MS airway adapters prohibits their use in rats. Therefore, we aimed to adapt a human-use MS capnograph sensor in rats by 3D printing.
Methods: A new MS airway adapter was designed and 3D printed for a commercially available human capnography sensor (Capnostat 3™) with an instrumental dead space fitting for rats. The device was validated in ventilated rats (n=6) and compared to a rodent-use SS capnograph (Harvard Apparatus Type 340) using different PEEP levels and respiratory rates. Shape factors (2nd and 3rd phase slopes: S2, S3), end-tidal CO2 (ETCO2), and average expiratory CO2 levels (PECO2) were determined from time and volumetric domains. The arterial partial pressure of CO2 (PaCO2) was used as a reference.
Results: MS capnography using the 3D printed adapter detected ETCO2‑PaCO2 gradients of ‑4.6 mmHg [95%CI: ‑5.59–‑3.66] compared to ‑13.5 mmHg [‑14.96–‑12.02] of the SS approach. The MS and SS methods showed a significant (p<0.001 for all), strong correlation regarding the main shape factors in both the time (ETCO2 r=0.75; S2 r=0.73), and volumetric domains (S2 r=0.70; PECO2 r=0.72).
Conclusions: The 3D printed MS airway adapter resulted in an ETCO2‑PaCO2 gradient closer to the physiological ‑10 to ‑5 mmHg compared to the SS method in rats. The 3D printed adapter also enables the determination of shape factors of the capnogram, demonstrating the benefits of 3D printing in adapting human-use devices to experimental settings.
Funding: OTKA-NKFIH FK134274, NTP-NFTO-20-B-0301
Footnotes
Cite this article as: European Respiratory Journal 2021; 58: Suppl. 65, PA3220.
This abstract was presented at the 2021 ERS International Congress, in session “Prediction of exacerbations in patients with COPD”.
This is an ERS International Congress abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only).
- Copyright ©the authors 2021