Nocturnal assisted ventilation using bilevel positive airway pressure: The effect of expiratory positive airway pressure

Abstract

Increasing expiratory positive airway pressure (EPAP) has theoretical advantages during overnight nasal ventilation. We wanted to evaluate the effect of the addition of EPAP upon the control of nocturnal hypoventilation. Seven patients with neuromuscular/skeletal (NMS) disorder (mean±SD forced vital capacity (FVC) 1.06±0.28 l, arterial oxygen tension (PaO2) 9.1±0.6 kPa, and arterial carbon dioxide tension (Paco2) 6.9±0.9 kPa), and seven patients with chronic obstructive pulmonary disease (COPD) (FEV1 0.46±0.14 l, PaO2 6.2±0.6 kPa, and Paco2 8.4±1.1 kPa) all underwent full polysomnography on two nights during bilevel positive airway pressure (BiPAP) ventilation, with and without the addition of expiratory positive airway pressure, which was matched to the level of dynamic positive end-expiratory pressure (PEEP) or set at a minimum value of 5 cmH2O. In the group with neuromuscular/skeletal disorders the maximum transcutaneous carbon dioxide tension (PtcCO2) overnight was lower (inspiratory positive airway pressure (IPAP) 8.1±1.4 kPa, IPAP/EPAP 7.3±0.9 kPa) and the minimum level of arterial oxygen saturation (SaO2min) increased (IPAP 77.1±6.7%, IPAP/EPAP 83.6±4.2%) when expiratory positive airway pressure was added. There were no differences in mean PtcCO2 or mean oxygen saturation, but sleep quality was worse (non-rapid eye movement (non-REM) sleep IPAP 266±44 min, IPAP/EPAP 226±32 min). In the patients with COPD, expiratory positive airway pressure conferred no advantage. In conclusion, 5 cmH2O expiratory positive airway pressure improved the control of nocturnal hypoventilation in patients with neuromuscular/skeletal disorders, but not in patients with COPD. However, expiratory positive airway pressure may have a deleterious effect upon sleep quality in some patients.