Neural respiratory drive during apnoeic events in obstructive sleep apnoea.

For a given neural drive, oesophageal pressure during apnoeic episodes may differ from that during airflow, since inspiratory airflow and increased lung volume both reduce pressure generation. It was, therefore, hypothesised that diaphragm electromyography (EMG) may provide additional data to oesophageal pressure when used for the assessment of neural drive in patients with obstructive sleep apnoea, whose breathing is associated with variable airflow and changes in lung volume. Neural respiratory drive was assessed using diaphragm EMG recorded from multipair oesophageal electrodes in 12 patients with obstructive sleep apnoea. Oesophageal pressure was also recorded. The mean+/-sd inspiratory oesophageal pressure swing was 11.0+/-3.7 cmH(2)O during wakefulness, 38.2+/-15.7 cmH(2)O at the end of the apnoea and reduced to 28.5+/-10.4 cmH(2)O at the beginning of arousal. The mean peak inspiratory diaphragm EMG signal was 21.8+/-6.5 muV during wakefulness, 38.6+/-14.0 muV at the end of the apnoea and further increased to 59.6+/-32.0 muV at the beginning of arousal. It was concluded that the pattern of neural drive assessed by oesophageal pressure differs from that measured by diaphragm electromyography during apnoeic events and, therefore, that diaphragm electromyography may be a useful adjunct to measurement of oesophageal pressure for the assessment of neural drive in patients with obstructive sleep apnoea.