TIME TO EQUILIBRATION OF OXYGEN-SATURATION USING PULSE OXIMETRY

Objective: To determine the time it takes for O-2 saturation measured by pulse oximetry to equilibrate after a change is made in supplemental O-2 administered by nasal cannula in patients with cardiac and pulmonary disease. Methods: A prospective, observational study of a convenience sample of 51 patients treated in a university-affiliated ED with nasal cannula O-2. Patients were placed on and/or subsequently taken off O-2 via nasal cannula set at 2 or 4 L/min based on clinical indications. Oxygen saturation was measured at 1-minute intervals over a 30-minute period using finger-probe pulse oximetry. Of the 51 patients in the study, 43 were monitored while O-2 treatment was initiated and 18 were monitored when it was discontinued. Results: Most (95%) of the patients placed on O-2 attained equilibration of O-2 saturation within 3.5 minutes. Most (95%) of the patients taken off supplemental O-2 attained equilibration of O-2 saturation within 4.5 minutes. Conclusion: The interval to equilibration of O-2 saturation in patients receiving O-2 by nasal cannula is considerably shorter than the 20-30 minutes generally suggested. Adequacy of O-2 supplementation should be assessable much sooner than was previously taught.