Obesity hypoventilation syndrome: current theories of pathogenesis.
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To summarize recent primary publications and discuss the impact these finding have on current understanding on the development of hypoventilation in obesity hypoventilation syndrome (OHS), also known as Pickwickian syndrome.As a result of the significant morbidity and mortality associated with OHS, evidence is building for pre-OHS intermediate states that can be identified earlier and treated sooner, with the goal of modifying disease course. Findings of alterations in respiratory mechanics with obesity remain unchanged; however, elevated metabolism and CO2 production may be instrumental in OHS-related hypercapnia. Ongoing positive airway pressure trials continue to demonstrate that correction of nocturnal obstructive sleep apnea and hypoventilation improves diurnal respiratory physiology, metabolic profiles, quality of life, and morbidity/mortality. Finally, CNS effects of leptin on respiratory mechanics and chemoreceptor sensitivity are becoming better understood; however, characterization remains incomplete.OHS is a complex multiorgan system disease process that appears to be driven by adaptive changes in respiratory physiology and compensatory changes in metabolic processes, both of which are ultimately counter-productive. The diurnal hypercapnia and hypoxia induce pathologic effects that further worsen sleep-related breathing, resulting in a slowly progressive worsening of disease. In addition, leptin resistance in obesity and OHS likely contributes to blunting of ventilatory drive and inadequate chemoreceptor response to hypercarbia and hypoxemia.