Sleep Hypercapnia Research Articles

Is bilevel PAP more effective than CPAP in treating hypercapnic obese patients with COPD and severe OSA?

Commentary on Zheng Y, Yee BJ, Wong K, Grunstein R, Piper A. A pilot randomized trial comparing CPAP versus bilevel PAP spontaneous mode in the treatment of hypoventilation disorder in patients with obesity and obstructive airway disease. J Clin Sleep Med. 20XX;XX(XX):XXX-XXX. doi:10.5664/jcsm.9506.

Identification of sleep hypoventilation in young individuals with Becker muscular dystrophy: A pilot study

AimTo report on sleep hypercapnia in Becker muscular dystrophy (BMD) at earlier stages than ever recognized. Subjects and methodsThis retrospective study examined nocturnal hypercapnia in six young Becker muscular dystrophy (BMD) patients with deletions of one or more exons of DMD gene. Clinical information, consecutive data on forced vital capacity (FVC%), forced expiratory volume in one second (FEV1%), peak expiratory flow (PEF%), peak cough flow (PCF), average PCO2 in all-night monitoring, and left ventricular ejection fraction (LVEF) were reviewed. ResultsIn five BMD patients, including three who were still ambulant, nocturnal average PCO2 was elevated to >45 mmHg at 12–31 years of age. Noninvasive positive pressure ventilation was initiated in four patients. Gradual declines in FVC% and PEF% were evident in one BMD patient with exon 3–7 deletion, whereas these functions did not change in the remaining BMD patients. PCF, FEV1%, and LVEF were less informative for the assessment of respiratory function in this patient series. ConclusionSleep hypercapnia was present in certain BMD patients, which was unexpected from the routine pulmonary function tests. Individualized assessment of nocturnal PCO2, partly based on the deletion types, should be further explored in the clinical practice of BMD patients.

Response to Brugniaux, Foster, and Beaudin

to the editor: We thank Brugniaux et al. ([1][1]) for the comments, and we agree. It is likely that if sleep hypercapnia is an important mediator of cognitive impairment in sleep apnea syndromes, multiple mechanisms are at work. Altered cerebrovascular reactivity is plausibly one of them, with a

Sympathetic Withdrawal Augments Cerebral Blood Flow During Acute Hypercapnia in Sleeping Lambs

Cerebral sympathetic activity constricts cerebral vessels and limits increases in cerebral blood flow (CBF), particularly in conditions such as hypercapnia which powerfully dilate cerebral vessels. As hypercapnia is common in sleep, especially in sleep disordered breathing, we tested the hypothesis that sympathetic innervation to the cerebral circulation attenuates the CBF increase that accompanies increases in PaCO2 in sleep, particularly in REM sleep when CBF is high. Newborn lambs (n = 5) were instrumented to record CBF, arterial pressure (AP) intracranial pressure (ICP), and sleep-wake state (quiet wakefulness (QW), NREM, and REM sleep). Cerebral vascular resistance was calculated as CVR = [AP-ICP]/CBF. Lambs were subjected to 60-sec tests of hypercapnia (FICO2 = 0.08) during spontaneous sleep-wake states before (intact) and after sympathectomy (bilateral superior cervical ganglionectomy). During hypercapnia in intact animals, CBF increased and CVR decreased in all sleep-wake states, with the greatest changes occurring in REM (CBF 39.3% +/- 6.1%, CVR -26.9% +/- 3.6%, P < 0.05). After sympathectomy, CBF increases (26.5% +/- 3.6%) and CVR decreases (-21.8% +/- 2.1%) during REM were less (P < 0.05). However the maximal CBF (27.8 +/- 4.2 mL/min) and minimum CVR (1.8 +/- 0.3 mm Hg/ min/mL) reached during hypercapnia were similar to intact values. Hypercapnia increases CBF in sleep and wakefulness, with the increase being greatest in REM. Sympathectomy increases baseline CBF, but decreases the response to hypercapnia. These findings suggest that cerebral sympathetic nerve activity is normally withdrawn during hypercapnia in REM sleep, augmenting the CBF response.