The overall duration of polysomnography was 570 min (the recording began at 9:16 pm and ended at 6:46 am), 505 min of which, up to the time of respiratory arrest, were analyzed. The last 65 min of the recording were those after final breathing, a time not studied in terms of hypnogram and apnea-hypopnea index to obtain polysomnography analysis and scoring when the patient was alive. Sleep time, according to the hypnogram, was 434 min. The tracings, obtained with measurements of nasal pressure airflow by nasal cannula and no thermocouple, confirmed the diagnosis of severe CSR with an apnea-hypopnea index of 93.3. This breathing pattern was evident from the beginning of our recording during wakefulness with airflow waveforms consistent with CSR, with a waxing-waning pattern and without respiratory pause. Fixed CSR with frank apnea developed throughout the recording after the patient fell asleep (Fig 1
, left, A). No obvious obstructive event was observed in this obese and hypercapnic patient. Oxygen saturation on room air was 61% in the beginning of the recording and averaged 58.7% during the night. At 5:22 am, after a last complete episode of CSR, absence of the waxing phase of the next cycle and of the negative component of the airflow waveform was observed, as active expiratory movements ceased (Fig 1, right, B). In addition, the amplitude of the waveform decreased, with lengthening of the pauses between respiratory cycles. The progressive and regular decrease in the amplitude of the waveform ended in complete absence of airflow movement 19 min later (Fig 2
, left, A). Cardiac arrest was documented 7 min after the respiratory arrest (Fig 2, right, B).