Obese patients may have hypersomnolence and muscle twitching associated with irregular periodic respiration.1-8 The periodic breathing frequently occurs during sleep or when the patient is lying supine and may disappear upon awakening or stimulation. The respiration is quite irregular in quality and is composed of periods of apnea and hyperpnea which are unequal from cycle to cycle, and the ratio of apnea to hyperpnea is often equal or greater than unity. This form of respiration has been called hypercarbic or ataxic periodic respiration, medullary, cluster, or Biot's respiration.9 It is distinguished from other forms of periodic respiration such as inspiratory gasping, apneustic-like inspiratory pauses, sustained periodic breathing, and Cheyne-Stokes respiration (Fig 1).
Ataxic periodic breathing occurs in low pontine and upper medullary lesions,9-11 narcolepsy,12,13 bulbar poliomyelitis,9 and myotonic dystrophy 14,15 as well as obesity. It resembles the periodic breathing of hedgehogs and hibernating mammals