Clinics in chest medicine
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Clinics in chest medicine · Sep 2014
ReviewCongenital central hypoventilation syndrome: a neurocristopathy with disordered respiratory control and autonomic regulation.
Congenital central hypoventilation syndrome (CCHS), a rare neurocristopathy with disordered respiratory control, is characterized by alveolar hypoventilation and diffuse autonomic nervous system (ANS) dysregulation. Mutations in the paired-like homeobox 2B (PHOX2B) are causative, leading to physiologic ANS dysregulation and pathologic abnormalities. ⋯ Breathing complications occur despite the lungs and airways being normal. Disordered respiratory control demonstrated by absent or severely attenuated ventilatory, behavioral, and arousal responses to both endogenous and exogenous hypoxemia and hypercarbia results in severe physiologic compromise.
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Respiration during sleep is determined by metabolic demand; respiratory drive is determined by a central respiratory generator. Changes in pharyngeal dilator muscle tone resulting in increased upper airway resistance and collapsibility contribute to hypoventilation. ⋯ This article reviews mechanisms of central control of respiration and normal upper and lower airway physiology. Understanding sleep-related changes in respiratory physiology will help in developing new therapies to prevent hypoventilation in susceptible populations.
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The sleep state is associated with significant changes in respiratory physiology, including ventilatory responses to hypoxia and hypercapnia, upper airway and intercostal muscle tone, and tidal volume and minute ventilation. These changes are further magnified in certain disease states, such as chronic obstructive pulmonary disease, restrictive respiratory disorders, neuromuscular conditions, and cardiac diseases. This article discusses the regulation of breathing during sleep in health and associated comorbid conditions.
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Sleep respiration is regulated by circadian, endocrine, mechanical and chemical factors, and characterized by diminished ventilatory drive and changes in Pao2 and Paco2 thresholds. Hypoxemia and hypercapnia are more pronounced during rapid eye movement. Breathing is influenced by sleep stage and airway muscle tone. ⋯ Medications partially improve obstructive sleep apnea and stabilize periodic breathing at altitude. Potential adverse consequences of medications include precipitation or worsening of disorders. Risk factors for adverse medication effects include aging, medical disorders, and use of multiple medications that affect respiration.
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Maturational changes of breathing during sleep contribute to the unique features of childhood sleep disorders. The clinician's ability to evaluate common disorders related to sleep in children relies on an understanding of normal patterns of breathing during sleep across the ages. This article reviews respiratory physiology during sleep throughout childhood. Specific topics include an overview of respiration during sleep, normal parameters through childhood including respiratory rate, oxygen saturation, and measures of carbon dioxide, normal patterns of apneas throughout childhood, and features of breathing during sleep seen in term and preterm infants.