Effect of positive end-expiratory pressure on breathing patterns of normal subjects and intubated patients with respiratory failure.

Abstract

The aims of this study included assessment of accuracy of respiratory inductive plethysmography when pulmonary hyperinflation was induced by application of PEEP, and examination of breathing patterns of normal subjects, intubated patients requiring mechanical ventilation and intubated patients immediately before extubation during application of PEEP by demand valve and high gas flow reservoir bag systems. Validation of tidal volume (VT) and end-expiratory level measured with respiratory inductive plethysmography to simultaneous spirometry (SP) was achieved with PEEP levels up to 12.5 cm H2O in 7 normals. In 17 intubated patients, almost all VT values measured with respiratory inductive plethysmography fell within +/- 10% of SP even with 2 to 3 changes of body posture. In normal subjects, increasing levels of PEEP from the demand valve system produced nonprogressive rises of VT and mean inspiratory flow, falls of frequency and fractional inspiratory time (TI/TTOT), and no changes of minute ventilation (Vmin) nor mean expiratory flow. PEEP from the high gas flow reservoir bag system produced nonprogressive rises of VT and rib cage (RC) contribution to VT, and rises of Vmin and mean inspiratory and expiratory flows between 10.0 and 12.5 cm H2O of PEEP. Intubated patients requiring intermittent mandatory ventilation (IMV) had a rapid, shallow breathing pattern unaltered by PEEP levels delivered by either system up to 12.5 cm H2O despite increases of end-expiratory level. Intubated patients who were about to be extubated breathed with patterns closer to ambulatory normal subjects with the exception of their elevated RC contribution to VT.(ABSTRACT TRUNCATED AT 250 WORDS)