2.  Severe central sleep apnea, on CPAP at 10 cmH2O and supplemental oxygen at 8 liters per minute.  The breathing pattern is that of cluster or Biot's breathing throughout sleep.  The primary etiology is probably opiate use, with contribution with further exacerbation by severe obesity which acts to lower the baseline oxyhemoglobin saturation, and worsen desaturations during apneic episodes.