Measurement of evoked diaphragm twitch strength during anaesthesia. Adaptation and evaluation of an existing technique

The technique of recording the mechanical response of the diaphragm after the transcutaneous stimulation of the phrenic nerve, during anaesthesia and surgery, is described in patients undergoing non-abdominal surgery. The pressure difference generated across the diaphragm after phrenic nerve stimulation was derived from the simultaneous recording of gastric and oesophageal pressures with air-filled balloon catheter systems. This was recorded as the diaphragm "twitch" in a manner similar to that of peripheral muscles. Special problems encountered in the use and the validation of the technique in the anaesthetized patient are considered.