Effectiveness of noninvasive respiratory strategies for the management of postoperative hypoxaemia in dogs: a prospective, randomized clinical trial

Objective To evaluate the effectiveness, the time to restore normoxaemia (TRN), and the tolerability of face mask (FM), continuous-positive-airway-pressure helmet (CPAP), or high-flow nasal cannulae (HFNC) as noninvasive respiratory support strategies for treating transient postoperative hypoxaemia in dogs. Study design Prospective, randomized, clinical trial. Animals A total of 600 client owned dogs anaesthetized for various procedures. Methods At the end of general anaesthesia, the haemoglobin oxygen saturation (SpO 2 ) on room air (SpAT) was used for assessment of oxygenation 10 minutes after extubation (T-POST). Hypoxaemic dogs (SpO 2 < 95%) were randomly assigned to: FM-group [flow rate = 10 L minute –1 ; fraction of inspired oxygen (F I O 2 ) = 0.3–0.4], CPAP-group (flow rate = 10 L minute –1 ; F I O 2 = 0.3–0.4; CPAP = 5 cmH 2 O), and HFNC-group (flow rate = 2–2.5 L kg –1 minute –1 at 37 °C; F I O 2 = 0.3–0.4). Treatments lasted 1 hour, divided into 15-minute intervals (T15, T30, T45, T60) with 10 minutes of treatment and 5 minutes of SpAT. The TRN during SpAT was recorded. Interface tolerance was assessed using a dedicated scale. SpO 2 and TRN were compared with two-way ANOVA, Kruskal–Wallis was used to test for differences in tolerance score between groups. p < 0.05. Results At T-POST, 168 dogs (28%) were hypoxaemic, and 76 of them completed the study (CPAP-group n = 31, FM-group n = 24, HFNC-group n = 21). All treatments restored normoxaemia. TRN was faster in the CPAP-group compared with HFNC-group and FM-group (mean ± standard deviation: 16.9 ± 15.7, 27.8 ± 20.8, and 40.4 ± 12.8 minutes, respectively) ( p < 0.05). Tolerance was good for all devices, without differences between groups. Conclusions and clinical relevance Postoperative hypoxaemia in dogs can be effectively treated with FM, HFNC, or CPAP, the latter restoring normoxaemia more rapidly.