The effect of neuromuscular blockade on the efficiency of mask ventilation of the lungs*

Abstract

We conducted a two-part study to assess the practice of withholding neuromuscular blockade until the ability to ventilate the lungs using a bag and face mask (mask ventilation) has been established following induction of anaesthesia. The first part of the study consisted of a postal survey (71% response rate) of 188 anaesthetists in the Oxford region to assess their current practice. Thirty per cent of respondents always checked mask ventilation before administering a neuromuscular blocking drug, whereas 39% of respondents (all them consultants) never did this. A further 31% only did so in the case of known or anticipated difficulty with the airway. In the second part of the study, we measured inspired (V(TI)) and expired (V(TE)) tidal volumes before and after neuromuscular blockade in 30 patients undergoing general anaesthesia. The ratio V(TE)/V(TI) was used as a measure of the efficiency of ventilation. There was no difference in V(TE)/V(TI) before [mean (SD) 0.47 (0.13)] and after [0.45 (0.13)] neuromuscular blockade. We conclude that neuromuscular blockade does not affect the efficiency of mask ventilation in patients with normal airways.