Résumé :
|
Communication n° 662 Patients with advanced neuromuscular diseases often require chronic mechanical ventilation. Long term-assisted ventilation often has to address the problem of leakage, whether the device used is a nasal mask or tracheostomy. Air leaks frequently increase during sleep inducing impairment of sleep quality and may contribute to the ineffectiveness of assisted ventilation. The aim of this study was to provide continuous measurement of such leaks during sleep using a non calibrated respiratory inductance plethysmography (RIP) system (Visuresp®). Data was obtained in 15 patients with neuromuscular disease admitted to the hospital for a routine polysomnography. Breath-by-breath analysis was performed on the insufflation (Vin) and expiration (Vex) signals (flow meter) and the abdominal (Vabd) and thoracic (Vtho) volume changes (RIP). The proposed method is based on the assumption that as leaks increase during sleep, the values of Vex, Vtho and Vabd recorded during sleep latency may be taken as reference values, with all the values recorded during sleep being expressed as a percentage of these reference values. This gives actual tidal thoracic and/or abdominal volumes as a percentage of their reference values and thus avoids the need for calibration. The results show that 1) the sleep latency sample exhibited the highest value, suggesting that values measured during sleep latency may indeed serve as satisfactory reference values, 2) leaks were present in all subjects, 3) compared to the difference Vin-Vex changes in Vtho and/or Vabd indicate less leakage and 4) the Vtho and Vabd signals can be used alone to estimate leaks. In conclusion, this method provides a reliable, non-invasive, bedside evaluation of air leaks in ventilated patients. The results of on-line continuous measurement of air leaks by this method could provide a feedback signal to a control system, which would regulate the assisted ventilation accordingly so as to minimize the leaks.
|