Physiological effects of posture on mask ventilation in awake stable chronic hypercapnic COPD patients

Stable chronic hypercapnic patients are often prescribed long-term mask non invasive pressure support ventilation (NPSV). There is a lack of informatio n on the effects of posture on NPSV. Therefore posture induced changes in p hysiological effects of NPSV in awake stable chronic hypercapnic patients w ere evaluated. In 12 awake chronic obstructive pulmonary disease (COPD) patients breathing pattern, respiratory muscles, mechanics and dyspnoea (by visual analogue s cale: VAS) were evaluated during spontaneous breathing (SB) in sitting post ure and during NPSV in sitting, supine and lateral positions randomly assig ned. Arterial blood gases were evaluated during SE and at the end of the la st NPSV session (whatever the posture). As expected NPSV resulted in a significant improvement in carbon dioxide te nsion in arterial blood (Pa,CO2) (from 7.4+/-0.85 to 6.9+/-0.7 kPa). When c ompared with SB, sifting NPSV resulted in a significant increase in tidal v olume and minute ventilation and in a significant decrease in breathing fre quency. Inspiratory muscle effort as assessed by oesophageal pressure swing s and pressure-time product per minute (from 14+/-4.8 to 6.2+/-3.5 cmH(2)O, and from 240+/-81 to 96+/-60 cmH(2)O . L . s . min(-1) respectively), intr insic dynamic positive end expiratory pressure (from 2.7+/-2.3 to 1.4+/-1.3 cmH(2)O) and expiratory airway resistance (from 18+/-7 to 5+/-3 cmH(2)O . L . s(-1)) decreased during sitting NPSV, whereas VAS did not change. Chang ing posture did not significantly affect any parameter independently of the patients weight, whether obese or not. In awake stable hypercapnic chronic obstructive pulmonary disease patients changing posture does not significantly influence breathing pattern and res piratory muscles during noninvasive pressure support ventilation suggesting that mask ventilation may be performed in different positions without any relevant difference in its effectiveness.