Continuous positive airway pressure administered via face mask in tranquilized dogs

Objective To evaluate the tolerance of a continuous positive airway pressure (CPAP) mask in tranquilized dogs and compare PaO2 in arterial blood in dogs receiving oxygen with a regular face mask or CPAP mask set to maintain a pressure of 2.5 or 5 cm H2O. Design Prospective, randomized clinical study. Setting University teaching hospital. Animals Sixteen client-owned dogs without evidence of cardiopulmonary disease were studied. Interventions Eight animals were randomly assigned to each of 2 treatment groups: group A received 2.5 cm H2O CPAP and group B received 5 cm H2O CPAP after first receiving oxygen (5 L/min) by a regular face mask. Animals were tranquilized with acepromazine 0.05 mg/kg, IV and morphine 0.2 mg/kg, IM. An arterial catheter was then placed to facilitate blood sampling for pHa, PaO2, and PaCO2 determinations before and after treatments. Direct mean arterial pressure, heart rate, respiratory rate, and temperature were also recorded after each treatment. Measurements and Main Results CPAP administration was well tolerated by all animals. The mean arterial pressure, heart rate, respiratory rate, temperature, PaCO2, and pHa, did not differ at any time point between groups. Differences were seen in oxygenation; in group A, PaO2 significantly increased from a mean of 288.3 +/- 47.5 mm Hg with a standard mask to a mean of 390.3 +/- 65.5 mm Hg with the CPAP mask and in group B, PaO2 increased similarly from 325.0 +/- 70.5 to 425.2 +/- 63.4 mm Hg (P < 0.05); no differences were detected between the 2 CPAP treatments. Conclusions In healthy tranquilized dogs noninvasive CPAP is well tolerated and increases PaO2 above values obtained when using a regular face mask.