The rate of respiratory depression with PCA is between 0.19% and 5.2%.
Risk factors for respiratory depression include the use of a basal infusion;
age greater than 70; obesity; sleep apnea; concurrent use of central nervous system depressants; upper abdominal or thoracic surgery; renal, hepatic, pulmonary,
or cardiac impairment; and a PCA bolus greater than 1 mg morphine without a basal rate.