Effects of continuous positive airway pressure administered by a helmet in cats under general anaesthesia.

Abstract

OBJECTIVES: The aim of this study was to evaluate the respiratory effects of non-invasive continuous positive airway pressure (CPAP) administered by a helmet in healthy cats under anaesthesia. METHODS: Fifteen healthy male cats scheduled for castration were anaesthetised with medetomidine (20&#x2009;&#xb5;g/kg), ketamine (10&#x2009;mg/kg) and buprenorphine (20&#x2009;&#xb5;g/kg) intramuscularly. When an adequate level of anaesthesia was achieved, a paediatric helmet was placed on all subjects. The helmet was connected to a Venturi valve supplied with medical air and cats received the following phases of treatments: 0 cmHO (pre-CPAP), 5 cmHO (CPAP) and 0 cmHO (post-CPAP). Each treatment lasted 10&#x2009;mins. At the end of each phase an arterial blood sample was drawn. The following data were also collected: mean arterial pressure, respiratory rate, heart rate and the anaesthesia level score (0&#x2009;=&#x2009;awake, 10&#x2009;=&#x2009;deep anaesthesia). The alveolar to arterial oxygen gradient (P[A-a]O) and the venous admixture (Fshunt) were also estimated. Data were analysed with two-way ANOVA (<0.05). RESULTS: The arterial partial pressure of oxygen was higher (<0.001) at CPAP (103.2&#x2009;&#xb1;&#x2009;5.1&#x2009;mmHg) vs pre-CPAP (77.5&#x2009;&#xb1;&#x2009;7.4&#x2009;mmHg) and post-CPAP (84.6&#x2009;&#xb1;&#x2009;8.1&#x2009;mmHg). The P(A-a)Oand the Fshunt were lower (<0.001) at CPAP (4.4&#x2009;&#xb1;&#x2009;2.3&#x2009;mmHg; 7.4&#x2009;&#xb1;&#x2009;3.1%) vs pre-CPAP (18.9&#x2009;&#xb1;&#x2009;6.4&#x2009;mmHg; 22.8&#x2009;&#xb1;&#x2009;4.6%) and post-CPAP (15.6&#x2009;&#xb1;&#x2009;7.3&#x2009;mmHg; 20.9&#x2009;&#xb1;&#x2009;4.6 %). No other parameters&#x2009;differed between groups. CONCLUSIONS AND RELEVANCE: Non-invasive CPAP applied by a helmet improves oxygenation in cats under injectable general anaesthesia.