The most dangerous thing we can do as medical professionals is to remove a patient’s physiologic negative pressure breathing circuit and replace it with a mechanical positive pressure ventilator.

In the military we’ve watched the world change quickly. Our generation has fought in the mountains of Afghanistan, the cities of Iraq, the deserts of Syria, and everywhere in between. Winding down our involvement in these theaters, we have identified our lack of proficiency in Prolonged Casualty Care, and focused on this as our primary skill set for future AOs. With this new focus comes new (perhaps familiar) tools, procedures, and mindsets to appropriately manage our critically ill and properly triaged patients.  

Ventilation, perfusion, and acid-base balance are affected when we change a breathing mechanism on which the body is dependent. Reduction of Ventilator Induced Lung Injury (VILI), Ventilator Associated Pneumonia (VAP), perfusion shifts, acidosis, and other pathologies related to mechanical ventilation rely on properly trained operators and the appropriate device. 

The SAVE-2 rattling around in a pelican case, an aid bag, or in the bottom of a gun truck is for the critical care vent as trying to teach an ASVAB-waiver/Post-COVID bonus baby to translate Chinese. Will it breathe? Sure. Is it the right person for the job? No. 

As we examine better, more sophisticated options, we have one that’s seen the back of Blackhawks, and we have a new kid on the block. The Zoll EMV+ and the Inovytec Ventway Sparrow are both devices that can hold their own compared to the intelligent machines commonly seen in ICUs. We have dissected both devices and made a recommendation for use on the ground.

The Zoll Impact

The Zoll Impact has been vital in military transport, dating all the way back to the Impact Eagle. The current Zoll EMV+ is a rugged, O2-sparing, middleweight ventilator. It has unique features relevant for field use usually reserved for clean ICUs while still functioning in the high alpine of the North Cascade mountains for 6 hours at sub-zero temps. The EMV+ comes equipped to perform Assist Control (AC), Synchronized Intermittent Mechanical Ventilation (SIMV), and Non-Invasive (CPAP with pressure support). It has the ability to manage a patient with multi-modal settings and is ideal in all scenarios. 

These modes allow treatment for the entire continuum of care. The EMV+ performance ranges from fully sedated patients and paralyzed post-RSI patients who require maximum lung recruitment (AC ideal) to the weaning spontaneously breathing patients. It’s suitable for treating patients 48 hours post-induction where sedation must be spared (SIMV ideal) to the toxic inhalation patients requiring oxygenation without intubation (CPAP ideal). It uses a compression-driven system instead of a pneumatic system, which requires less oxygen drive and can operate utilizing atmospheric pressure and FIO2 of 21% for up to 10 hours. At 9.6 pounds, it’s burlier of the two options under review, however still very manageable.  

The Ventway Sparrow

The Ventway Sparrow brings most of the capabilities of the Zoll in a more compact, lighter package. Inovytec offers a “robust” military version of the design, with rugged packaging and efficient tech optimized for austere environments. FDA cleared in 2021, it advertises use from sea level to 25,000 ft ASL, capturing almost every environment, and is already being used by US forces on the small unit level. The difference is that this device delivers on an actual critical care capability to the battlefield, here’s how:

In both volume control settings, it has a primary SIMV with pressure support. It will deliver breaths to a set tidal volume with additional PEEP for alveolar recruitment, or SIMV in pressure control, which delivers breaths to a set Peak Inspiratory Pressure or PIP, avoiding over pressurization. There are two non-invasive modes (CPAP and High Flow Nasal Cannula) and an additional CPR mode (providing breaths with an advanced airway at set tidal volumes depending on age). 

The addition of High Flow Nasal Cannula (HFNC) mode is groundbreaking in a prehospital “rugged” ventilator This concept is still nearly exclusively available to the Hamilton T1 or other ICU critical care ventilators. Max battery life is about half that of the Zoll, but given that you can change batteries on the fly, this is acceptable for field use. The added weight savings and fact that the user can recharge batteries while the vent is in use is ideal, and why we feel that this technology is the future for battlefield application.

Final Conclusion

In reviewing both devices, we believe the Inovytec outperforms the Zoll as a primary GROUND ventilator. Its size, capability, and versatility give it the edge. Additionally, it possesses all modes necessary to function as a critical care equivalent, and it eliminates potentially unnecessary functionality to the end-user who typically has less need for multi-day ventilator operations. From a triage perspective, we must evaluate our resources and conditions if we are reaching beyond 24 hours with a single patient on a vent.

We’d be remiss to avoid mentioning pharmacologically managing our patients throughout all phases of care, especially during mechanical ventilation. Depending on your scheme of sedation and the condition of the patient, redosing sedation and analgesia via push dose will be the most sparing of limited supplies. However, this is most time intensive as we must be ahead of the curve for patients not on continuous infusions. Frequently, a patient who is non-compliant to the ventilator receives inadequate sedation and analgesia. Typically this patient doesn’t need additional paralysis in the traumatic environment. When presented with a patient becoming tachycardic, desaturating, or overbreathing on mechanical settings, it is best to start by troubleshooting the patient (P-DOPE) before troubleshooting the machine. This is helpful to remember when selecting the most desirable functions of a portable ventilator. 

We hope you enjoyed reading our recommendation on commercially available vents for field use. If you have comments, please leave them below. As always, we appreciate your support as we work to optimize care for patients injured in the field. Please feel free to email use with questions at support@cromedical.com.

References

Tripp, M. et al., (2021, December 27). Mechanical ventilation basics (CPG ID: 92) . Joint Trauma System Clinical Practice Guidelines. Retrieved September 9, 2022, from https://jts.amedd.army.mil/assets/docs/cpgs/Mechnical_Ventilation_Basics_27_Dec_2021_ID92.pdf 

Bauer, E. (2015). Ventilator management: A prehospital perspective. FlightBridgeED. 

El Sayed, M. J., Tamim, H., Mailhac, A., & Mann, N. C. (2019, January). Impact of prehospital mechanical ventilation: A retrospective matched Cohort Study of 911 calls in the United States. Medicine. Retrieved September 8, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6358412/

Zoll EMV+731 Spec Sheet https://www.zoll.com/-/media/00-literature/product/ventilators/emv-plus/emv_specsheet_a4_mp0270_eng.ashx

Inovytec Ventway Sparrow (Rugged) Spec Sheet https://www.inovytec.com/ventway-sparrow-military/