Comparison of CPAP and oxygen therapy for treatment of postoperative hypoxaemia in dogs

To compare 5 cmH₂ O of continuous positive airway pressure with oxygen therapy in dogs recovering from general anaesthesia with low SpO₂ values. continuous positive airway pressure is more effective than oxygen therapy in restoring normoxaemia (SpO₂ ≥95%).

Prospectively, dogs recovering from anaesthesia, with SpO₂ <95% after extubation (T0), were randomised and treated with continuous positive airway pressure (FiO₂ 0.21) or oxygen (O₂ ; FiO₂ 0.35-0.40) therapy. Dogs were monitored with SpO₂ every 15 minutes for 1 hour (T15, T30, T45, T60). Data from normoxaemic dogs (SpO₂ >95%) were used as control (CTR).

Of the 42 dogs enrolled, 34 completed the study. Eleven dogs were treated with O₂ , 10 with continuous positive airway pressure and 13 were CTR. The SpO₂ values at T0 were similar in the continuous positive airway pressure and O₂ groups and were lower than in the CTR group. At T15, T30, T45 and T60, the SpO₂ values in the continuous positive airway pressure group were higher than at T0; these were similar to those of the CTR group at the same time-points. In the O₂ group, SpO₂ values were significantly higher at T45 and T60 than at T0; 45.5% of dogs became normoxaemic at T45 and the remaining dogs became normoxaemic at T60. The average time to reach normoxaemia in the O₂ group (53.1±7.3 minutes) was longer than in the continuous positive airway pressure group (15.0±0.0 minutes).

In dogs recovering from general anaesthesia with pulmonary gas exchange impairment, normoxaemia is restored more effectively and rapidly by using continuous positive airway pressure than by oxygen therapy.