Effects of proportional assist ventilation on exercise tolerance in COPD patients with chronic hypercapnia

Abstract

This study investigates the impact of proportional assist ventilation (PAV), a new mode of partial ventilatory support, on exercise tolerance and breathlessness in severe hypercapnic chronic obstructive pulmonary disease (COPD) patients. We also examined the effects of continuous positive airway pressure (CPAP) and pressure support ventilation (PSV). On two consecutive days, 15 stable hypercapnic COPD patients underwent four endurance tests on a cycle ergometer at 80% of their maximal workrate, receiving, via a nasal mask in random order, either: 1) sham ventilation (CPAP: 1 cmH2O); 2) CPAP (6 cmH2O); 3) PSV (inspiratory pressure support: 12-16 cmH2O; expiratory positive airway pressure (EPAP): 1 cmH2O); or 4) PAV (8.6+/-3.6 cmH2O x L(-1) and 3+/-1.3 cmH2O x L(-1)x s(-1) of volume and flow assistance, respectively plus EPAP: 1 cmH2O). Oxygen supply was standardized to maintain an arterial oxygen saturation (Sa,O2) of 92-93%. Breathing pattern and minute ventilation (by respiratory inductive plethysmography), pulse oximetry, end tidal partial pressure of CO2, cardiac frequency and sensations of dyspnoea and leg discomfort (by Borg scale) were monitored. In comparison to sham ventilation, PAV, PSV and CPAP were able to increase the endurance time (from 7.2+/-4.4 to 12+/-5.6, 10+/-5.2 and 9.6+/-4.6 min, respectively) and to reduce dyspnoea and oxygen flow to the nasal mask. However, the greatest improvement was observed with PAV. We conclude that PAV delivered by nasal mask can im-prove exercise tolerance and dyspnoea in stable hypercapnic COPD patients and hence this mode of ventilatory support may be useful in respiratory rehabilitation programmes.

Nasal proportional assist ventilation unloads the inspiratory muscles of stable patients with hypercapnia due to COPD

“…The data of this study confirm and extend previous observations, in patients with chronic respiratory insufficiency from both restrictive and obstructive diseases. It was shown that nasal-mask application of PAV improved the breathing pattern and arterial blood gases [1] and provided ventilatory assistance during exercise in severe nonhypercapnic [17] and hypercapnic [2] stable COPD patients. Other investigators have shown that PAV can unload the inspiratory muscles also in ventilatordependent intubated patients with acute respiratory failure due to exacerbation of COPD [4,5].…”

“…After those 40 min, FA and VA were combined to deliver PAV for an additional 40 min. Then, CPAP was increased 2±5 cmH 2 O for an additional 20 min. In two patients the signal from the gastric balloon became unsatisfactory during the course of the experimental procedure.…”

“…PAV was delivered through a commercial nasal mask (Respironics) by means of a prototype portable ventilator able to compensate for leaks (Respironics), as in the previous studies [1,2]. The ventilator delivers PAV according to the equation of motion generating a pressure in proportion to a patient's spontaneous effort.…”

“…elastance and resistance, is taken over according to a level of assistance, which has been decided by the caregiver and can specifically unload the resistive burden (flow assist: FA) and the elastic burden (volume assist: VA). As in previous studies [1,2], VA and FA were set initially at the minimum value of 2 cmH 2 O . L -1 and 1 cmH 2 O .…”

“…In recent studies [1,2], it has been shown that proportional assist ventilation (PAV) [3] can improve the breathing pattern and arterial blood gases during tidal breathing and decrease breathlessness during exercise in stable patients with chronic respiratory failure (CRF) and carbon dioxide (CO 2 ) retention. However, to understand whether PAV may play a role in the management of those patients, its effect on the patient's lung and respiratory muscle mechanics should also be investigated.…”