Field anesthesia machine ventilator oxygen consumption in models of high and low pulmonary compliance

Field anesthesia machine ventilators powered by compressed gas are designed for remote locations that may lack a pipeline supply of O2. This study determined the O2 consumption of the compPAC ventilator powered by E cylinders when ventilating the Vent Aid Training Test Lung model of high (HC) and low (LC) pulmonary compliance. Consumed O2 was calculated after measuring the mass of O2 depleted from the E cylinder. Three tidal volumes (V(T)) were tested (500, 750, and 1000 mL). The HC and LC settings were 0.100 and 0.020 L/cm H2O, respectively. N = 5 in each group, respiratory rate = 10 bpm, and I:E ratio = 1:2. Data were collected for 20 minutes per run. O2 consumption was directly proportional to V(T) and inversely proportional to compliance. The amount of O2 consumed by the ventilator ranged from 2.19 (interquartile range [IQR] 2.18-2.26) L/min in the HC-500 mL V(T) group to 3.76 (IQR 3.76-3.79) L/min in the HC-1000 mL V(T) group (P = 0.027) and from 2.63 (IQR 2.60-2.66) L/min in the LC-500 V(T) mL group to 4.89 (IQR 4.81-5.05) L/min in the LC-1000 mL V(T) group (P = 0.027). The volume of ventilator drive gas was less than minute ventilation (V(E)) in all groups.