Effect of Pressure Support Ventilation on Carboxyhemoglobin Toxicokinetic after Acute Carbon Monoxide Intoxication: a Swine Model.

INTRODUCTION: In an experimental study on carbon monoxide (CO) exposure in swine, we aimed to compare the influence of oxygen therapy using a non-rebreathing mask (NRM) to continuous positive airway pressure (CPAP) and two pressure support ventilation (PSV) devices on the decrease of the terminal elimination half-life of carboxyhemoglobin (COHb t1/2 ). This was the primary outcome.

METHODS: Eight spontaneously breathing pigs were sedated by propofol and exposed to 940 ppm CO several times (n = 25) to obtain COHb levels of 30%. CPAPb (high flow open system, CPAP Boussignac® [7.5 cmH2 O]), PSV-Vy (open system, Vylife Boussignac®), and PSV-Leg (closed system, Legendair® [inspiratory/expiratory airway pressure 12/4 cmH2 O]) devices were used in a randomized order and compared to NRM (O2 at 15 l min-1 ) and atmospheric air (AA). The primary outcome was COHb t1/2 . Multiple comparisons were performed using Dunn's tests.

RESULTS: Median FiO2 and minute ventilation were significantly higher in the PSV-Leg group than the NRM group (p < 0.05). Median COHb t1/2 was 251, 85, 82, 93, and 58 min for AA, NRM, CPAPb, PSV-Vy, and PSV-Leg, respectively. All the interventions were superior to AA in terms of CO elimination (p < 0.001), but there was no statistically significant difference between CPAP or PSV and NRM. There was only a trend between PSV-Leg and NRM (p = 0.18). The median AUCs for ln (COHb) × time (h) were 170, 79, 83, 100, and 64 for AA, NRM, CPAPb, PSV-Vy, and PSV-Leg respectively, with a statistically significant difference only between AA and PSV-Leg (p = 0.002).

CONCLUSION: In conclusion, in our study on CO intoxication in swine, the use of the closed PSV-Leg system led to the shortest COHb t1/2 . These results suggest that PSV-Leg can be more efficient than NRM in eliminating CO and support the design of a clinical study to assess this hypothesis.