Air leakage during nocturnal mechanical ventilation in patients with neuromuscular disease

Objective

Air leakage is a major problem in long-term assisted ventilation both invasive and non-invasive that becomes even more important during sleep. The objective of this work was to provide a method for continuous estimation of tidal volume changes in patients under ventilatory support during sleep.

Materials and methods

Recordings were from 14 patients with neuromuscular disorders admitted to hospital for a routine evaluation of assisted ventilation during sleep. Air leakage was continuously evaluated from: 1) the difference between the insufflated and expired volume using a flow meter; 2) the changes in lung volume using inductance plethysmography.

Results

Both methods showed presence of air leaks in all patients and also variations in their amount throughout the night. However, inductance plethysmography provided more rigorous measurement of air leaks than flow meters as it measures the amount of air actually entering the lungs. The magnitude of leakage does not appear to be related to the method of assisted ventilation (invasive or non-invasive) or to the characteristic of the assistance mode (volume control or volume assist control).

Conclusion

The proposed method offers a reliable, non-invasive, continuous, bedside evaluation of air leak changes in ventilated patients. On-line analysis can be performed to find optimal ventilator settings in order to compensate for leakage while providing patient comfort.