From: Patterns of unexpected in-hospital deaths: a root cause analysis
TYPE I | Hyperventilation Compensated Respiratory Distress ( e.g. Sepsis, PE, CHF) |
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 | Stable SPO2 with progressively falling PaCO2 eventually yields to slow SPO2 decline (mitigated by respiratory alkalosis) and followed by precipitous SPO2 decline when metabolic acidosis dominates |
TYPE II | Progressive Unidirectional Hypoventilation (CO2 Narcosis) |
 | Progressive rise in PaCO2 (and etCO2) and fall in SPO2 over 15 minutes to many hours. (Often due to overdosing of narcotics or sedatives) |
TYPE III | Sentinel Rapid Airflow/SPO2 Reductions Followed by Precipitous SPO2 Fall. |
 | A state of "arousal dependent survival" that occurs only during sleep. Arousal failure allows precipitous hypoxemia during apnea causing terminal arousal arrest. |