Page 40 - JSOM Summer 2024

with differing CO production and/or oxygen consumption, University of Cincinnati Institutional Review Board approved
2
with and without spontaneous breathing. We only studied two the study as an exempt protocol 2019-1078 in October 2019.
portable ventilators and only one of each model. The system may The information, content, and conclusions do not necessar-
perform differently with other ventilators. The rebreather system ily represent the official position or policy of the University
was studied at simulated altitudes in an altitude chamber. The of Cincinnati, United States Government, Department of De-
system may perform differently in real-world conditions at alti- fense, or United States Air Force.
tudes encountered during aeromedical transport.
References
We did not evaluate long-term use on ventilator function 1. Daugherty EL, Branson R, Rubinson L. Mass casualty respiratory
(moisture in the ventilator inlet) nor did we evaluate the poten- failure. Curr Opin Crit Care. 2007;13(1):51–56. doi:10.1097/
MCC.0b013e3280129979
tial for contamination of the ventilator and need for cleaning 2. Mer M, Aryal D, Nielsen ND, et al. Critical care pandemic prepa-
between patients. Although we used several filters within the ration: considerations and lessons learned from COVID-19. Crit
system, perhaps these should be HEPA filters to reduce bac- Care Clin. 2022;38(4):761–774. doi:10.1016/j.ccc.2022.07.002
terial/viral contamination. The T1 portable ventilator (Ham- 3. Belle J, Cohen H, Shindo N, et al. Influenza preparedness in low-
resource settings: a look at oxygen delivery in 12 African countries.
ilton Medical, Bonaduz, Switzerland) is used in selected DoD J Infect Dev Ctries. 2010;4(7):419–424. doi:10.3855/jidc.859
medical scenarios and was considered for evaluation in this 4. Navuluri N, Srour ML, Kussin PS, et al. Oxygen delivery sys-
study. At the time of this study, our T1 ventilator did not have tems for adults in Sub-Saharan Africa: A scoping review. J Glob
an inlet that allowed attachment to the rebreathing system via Health. 2021;11:04018. doi:10.7189/jogh.11.04018.
standard connectors to collect the expired gas and therefore 5. Lowes T, Sharley P. Oxygen conservation during long distance
transport of ventilated patients. Air Med J 2005;24(4):164–171.
could not be adapted to the system for evaluation. 6. Lowes T, Sharley P. Oxygen conservation during long-distance
transport of ventilated patients: assessing the Modified Circle
Unlike standard oxygen supplementation, rebreathing carries System. Air Med J. 2006;25(1):35–39.
an additional risk. Under standard operation, exhaustion of 7. Austin PN, Branson RD. Using anesthesia machines as critical
care ventilators during the COVID-19 pandemic. Respir Care.
oxygen supplies or accidental disconnection results in delivery 2021;66(7):1184–1195. doi:10.4187/respcare.08799
of room air. Loss of the oxygen supply in a rebreathing sys- 8. Conway CM. Anaesthetic breathing systems. Br J Anaesth. 1985;
tem can result in delivery of hypoxic gas mixtures and patient 57(7):649–657.
injury. 9. Donnelly A, Dolling S. Anasethetic breathing systems. Anaesth
Intensive Care Med. 2019;20(2):90–94.
10. Byrick RJ, Janssen E, Yamashita M. Rebreathing and co-axial cir-
Conclusion cuits: a comparison of the Bain and MERA F. Can Anaesth Soc J.
1981;28(4):321–328.
The results of this study show that using low oxygen flow 11. SAVe II Operation Manual. M40100 Rev 4.2 (12/18); Firmware
≤3L/min with a rebreathing system attached to a portable ven- Version R1.0.5. AutoMedx, LLC; 2018. Accessed February 6,
2023. https://automedx.com/content/M40100-SAVe-II-Operator-
tilator can provide FiO ≥90% across a range of ventilator set- Manual-Rev.-4.2-Final-181206.pdf.
2
tings and lung models, both at ground level and at altitude. 12. Oswald RP, DeBoer GE. Portable anesthesia transport system.
In its current form, this system is not compatible with some J Clin Eng. 1991;16(6):521–526.
portable ventilators owing to its inability to attach to the ven- 13. Pollock NW, Natoli MJ. Performance characteristics of the sec-
tilator air intake in order to complete the closed system. Suc- ond-generation remote emergency medical oxygen closed-circuit
rebreather. Wilderness Environ Med. 2007;18(2):86–94.
tioning and disconnection from the ventilator should be used 14. Johannigman JA, Branson R, Lecroy D, Beck G. Autonomous
sparingly because of the risk of hypoxemia. In our models, control of inspired oxygen concentration during mechanical ven-
CO - absorbent life was at least 7 hours at all conditions, which tilation of the critically injured trauma patient. J Trauma. 2009;
2
66(2):386–392.
would be adequate for most aeromedical and ground transports 15. Johannigman JA, Muskat P, Barnes S, Davis K Jr, Beck G, Branson
and anywhere oxygen is scarce. Use of a rebreathing system RD. Autonomous control of oxygenation. J Trauma. 2008;64(4)
has the potential for oxygen conservation but requires diligent (suppl):S295–S301.
monitoring of inspired FiO and CO to avoid negative conse- 16. Bourassa S, Bouchard PA, Dauphin M, Lellouche F. Oxygen con-
2
2
quences. The addition of an oxygen analyzer and capnograph servation methods with automated titration. Respir Care. 2020;
65(10):1433–1442.
to assure safety adds cost, complexity, and logistical hurdles. 17. Barnes SL, Branson R, Gallo LA, Beck G, Johannigman JA. En-
route care in the air: snapshot of mechanical ventilation at 37,000
Author Contributions feet. J Trauma. 2008;64(2)(suppl):S129–S134.
TB and RB conceived the concept. TB conducted the experi- 18. Buchanan IM, Coates A, Sne N. Does mode of transport confer a
ment, collected and compiled the data, and wrote the first draft. mortality benefit in trauma patients? Characteristics and outcomes
at an Ontario lead trauma hospital. CJEM. 2016;18(5):363–369.
MS provided the statistics, TB, RB, and MS conducted data doi: 10.1017/cem.2016.15
analysis. All authors read and approved the final manuscript. 19. Ingalls N, Zonies D, Bailey JA, et al. A review of the first 10 years
of critical care aeromedical transport during operation iraqi free-
Disclosures dom and operation enduring freedom: the importance of evac-
The authors do not have financial relationships relative to this uation timing. JAMA Surg. 2014;149(8):807–813. doi:10.1001/
jamasurg.2014.621
article to disclose. 20. Mason PE, Eadie JS, Holder AD. Prospective observational study
of United States (US) Air Force Critical Care Air Transport team
Funding operations in Iraq. J Emerg Med. 2011;41(1):8–13. doi:10.1016/j.
jemermed.2008.06.032
This project was funded through a grant from the Air Force 21. Maddry JK, Mora AG, Savell SC, et al. Impact of Critical Care
Research Laboratory, Wright Patterson Air Force Base, OH. Air Transport Team (CCATT) ventilator management on combat
mortality. J Trauma Acute Care Surg. 2018;84(1):157–164. doi:
Disclaimer 10.1097/TA.0000000000001607
The University of Cincinnati and the United States Air Force
approved this publication for universal distribution. The PMID: 38837173; DOI: 10.55460/9E9N-X3QB

38 | JSOM Volume 24, Edition 2 / Summer 2024