Ventilatory neural drive in chronically hypercapnic patients with COPD: effects of sleep and nocturnal noninvasive ventilation

Abstract

Sleep brings major challenges for the control of ventilation in humans, particularly the regulation of arterial carbon dioxide pressure (PaCO2). In patients with COPD, chronic hypercapnia is associated with increased mortality. Therefore, nocturnal high-level noninvasive positive-pressure ventilation (NIV) is recommended with the intention to reduce PaCO2 down to normocapnia. However, the long-term physiological consequences of PaCO2 “correction” on the mechanics of breathing, gas exchange efficiency and resulting symptoms (i.e. dyspnoea) remain poorly understood. Investigating the influence of sleep on the neural drive to breathe and its translation to the mechanical act of breathing is of foremost relevance to create a solid rationale for the use of nocturnal NIV. In this review, we critically discuss the mechanisms by which sleep influences ventilatory neural drive and mechanical consequences in healthy subjects and hypercapnic patients with advanced COPD. We then discuss the available literature on the effects of nocturnal NIV on ventilatory neural drive and respiratory mechanics, highlighting open avenues for further investigation.

Chronic obstructive pulmonary disease (COPD) and COPD-like phenotypes

“…The pathophysiological mechanism of chronic hypercapnic respiratory failure is complex and not entirely understood but hypoventilation seems to play the primary role ( 46 , 47 ). During sleep, hypoventilation is more pronounced and nocturnal home non-invasive ventilation (NIV) has been used in these patients ( 48 ). Early studies of home nocturnal NIV in those patients showed no benefit ( 49 , 50 ) but recent randomized controlled trials (RCTs) showed improvement in clinical outcomes, including reduction in hospitalizations and mortality benefit ( Figure 1 ) ( 51 , 52 ).…”

Effects of non-invasive ventilation on sleep in chronic hypercapnic respiratory failure

“…20 The combination of these pathophysiological changes in COPD directly exaggerates the normal ventilatory changes in healthy adults during sleep, resulting in sleep hypoventilation and development of hypercapnic respiratory failure. 21 These pathophysiological constraints are reflected in the symptoms and quality of life, as measured by clinical outcomes and standardised validated questionnaires. The Pittsburgh Sleep Quality Index (PSQI) is a widely available tool used to evaluate subjective sleep quality; the higher the score, the worse the subjective sleep quality.…”