Effects of single hyperinflation using a sustained high pressure manoeuvre during inhalation anaesthesia in horses

The effect of a single hyperinflation using a sustained high-pressure manoeuvre (SHPM) during inhalation anaesthesia was evaluated in horses. Twenty-eight client-owned male horses were recruited; 14 were operated on in dorsal recumbency and 14 in lateral recumbency. For each category, horses were randomly allocated to either the 'breathing spontaneously' or 'mechanically ventilated' group. After 30 min of anaesthesia, baseline cardiorespiratory parameters were collected and a SHPM of 50 cmH2O during 50s was undertaken. In the group of horses breathing spontaneously and positioned in dorsal recumbency, venous admixture developed significantly more than in other groups and a single SHPM only partially and transiently improved arterial oxygenation. No benefit of the respiratory manoeuvre was observed in the other groups.