Can We Improve Sleep Quality by Changing the Way We Ventilate Patients?

Abstract

Sleep is an integral part of daily life. Both disrupted andrestricted sleep adversely affect well-being and predisposeto chronic medical problems [1]. For example, in epide-miologic studies, women reporting 5 or fewer hours ofsleep per night are at significantly increased risk of incidentcardiovascular disease and diabetes over a 10-year timeperiod [2, 3].Critically ill mechanically ventilated patients have longbeen known to have poor sleep quality [4], but the potentialimportance of sleep disturbance in these patients is onlynow starting to be recognized [5, 6]. Sleep deprivation mayadversely affect respiratory, cognitive, cardiovascular,endocrine, and immune function in normal subjects [7–9];altered sleep architecture may be associated with anincreased incidence of delirium in ICU patients [10]. Fur-thermore, in the case of long-term positive-pressure ther-apy, adherence to the treatment may be influenced by howit affects sleep [11].There are numerous factors that adversely affect sleepquality in critically ill patients. Noise, nursing care, circa-dian rhythm disruption, and light exposure have all beenimplicated [12, 13], as have severity of illness andmedications [14]. Interest, however, has recently turnedtoward the mode and settings of mechanical ventilation as acause of sleep disturbance [15].Major causes of sleep disturbance associated withmechanical ventilation include patient-ventilator asyn-chronies [16], central apneas due to overventilation [17],and inadequate ventilatory support due to improper settingsor air leaks leading to increased respiratory effort [18].Therefore, there is a renewed interest in finding novel waysof adequately ventilating patients while minimizing sleepdisturbance.In a previous issue of Lung, Crisafulli et al. [19] pre-sented the findings of a pilot study comparing a newermode of noninvasive ventilation, average volume assuredpressure support (AVAPS), to noninvasive pressure sup-port (NIV-PS) therapy in nine stable hypercapnic COPDpatients. AVAPS differs from NIV-PS in its ability toensure more consistent minute ventilation by slowlyadjusting inspiratory positive airway pressure (IPAP) toachieve a preset tidal volume. Therefore, there is a theo-retical benefit in that this mode of ventilation couldimprove nocturnal ventilation in hypercapnic patients,leading to improvements in CO