Demand valve ventilation in a swine pneumothorax model.

Bag-valve-mask (BVM) and oxygen-powered demand valve (OPDV) are two available adjuncts for artificial ventilation. Use of OPVDs has been limited by concern for causing or worsening pneumothorax. This study examined the effect of OPDV and BVM ventilation in swine with pneumothorax. This was a randomized, crossover design. Five female swine (16 to 23 kg) were sedated (ketamine/xylazine), anesthetized (alpha chloralose), and intubated. Right chest injury was induced, through an incision, using a 14-gauge needle to produce disruption of underlying lung parenchyma. An 18F Foley catheter was inserted and sealed in the right pleural space at the cut-down site. For each trial, a pneumothorax was induced by instilling 300 mL of air. Each subject underwent 10-minute ventilation trials with OPDV and with BVM by the same investigator, blinded to instrumentation. Post-trial pneumothorax volume, heart rate, blood pressure, end-tidal CO2 (ETCO2), and arterial blood gases were measured. There was no significant difference in pneumothorax volume after OPDV ventilation (310.8 mL) versus BVM ventilation (315.4 mL) (P = .821). There were no significant differences between heart rates, blood pressures, or arterial blood gases, although ETCO2 showed statistically significant decreases from baseline in both OPDV (33.0 to 28.6) and BVM (33.8 to 30.2) trials. However, multiple comparisons showed no significant differences between OPDV and BVM at any time points. In this model, OPDV and BVM ventilation did not differ in their effects on pneumothorax volume or hemodynamic variables. No animal showed signs of tension pneumothorax.