Potential Mechanical Ventilation System For Emergency Care During Spaceflight Missions

Abstract

Neurally Adjusted Ventilation Assist (NAVA) technology is an autonomous mechanical ventilator that is triggered by diaphragm activity (EAdi) to provide the necessary assisted breath required by the patient. This technology could be an asset toward medical autonomy during spaceflight missions. PURPOSE: To test if NAVA has potential for increasing medical autonomy during spaceflights and to test ventilatory assist with NAVA at rest and during steady state physical exercise. METHODS: EAdi, respiratory frequency (RF), tidal volume (VT) and pulmonary ventilation (VE) were measured on 5 participants (males, age: 24.8 ± 2.8 yrs, height: 1.74 ± 0.07 m, weight: 71.8 ± 11.9 kg, V02max: 51.42 ± 5.32 ml/kg/min) during 6 minutes of resting breathing (T0) and during 10 minutes at 70% of V02max on an ergocycle (T1: minutes 1-3 and T2: minutes 8-10). This protocol was performed without (WO) and with NAVA (W) 30 minutes later. Paired T-tests were performed between both conditions. RESULTS: A slightly lower EAdi was observed with NAVA at T0 (WO: 3.52 ± 1.04 μV, W: 2.67 ± 0.88 μV, p = 0.2761), T1 (WO: 15.74 ± 4.79 μV, W: 15.34 ± 6.16 μV, p = 0.9190) and T2 (WO:23.42 ± 4.4 μV, W:23.19 ± 2.83 μV, p = 0.9105). However, NAVA was activated at every inspiration meaning that the electrodes on the naso-gastric tube can capture EAdi at high RF; T0 (WO: 13 ± 3, W: 14 ± 6 breaths/min), T1 (WO: 21 ± 2, W: 18 ± 4) and T2 (WO: 27 ± 4 and W: 23 ± 4). VE was also slightly lower with NAVA at T2 (WO: 63.17 ± 7.72, W: 59.78 ± 7.52 L/min), but these results were not significant. VT was slightly higher with NAVA at T0 (WO:1.08 ± 0.3, W: 1.22 ± 0.75 L/breath), T1 (WO:2.11 ± 0.46, W:2.32 ± 0.8 L/breath) and T2 (WO:2.43 ± 0.47, W: 2.67 ± 0.76 L/breath), but these results were not statistically significant. Also, the mechanical ventilator portion triggered by NAVA was unable to offer sufficient positive pressure to maintain inspiratory flow during exercise (peaked during first minute of exercise). CONCLUSION: NAVA is light, portable, and auto adjustable, which are desirable characteristics for medical equipment for spaceflight missions. It provided assisted breathing at rest but was unable to offered limited mechanical ventilation airflow during exercise. Funding: Annie Martin received a scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC) for this project.