Clinical Testing of the Apnea Prevention Device

Abstract

Narcotic-induced respiratory depression is a major cause of perioperative morbidity and mortality. Current monitoring modalities are inadequate to detect and treat respiratory depression in postoperative patients. Intermittent nursing assessments, even if conducted frequently, may not capture the rapid onset of airway obstruction, apnea, and hypoxia that can occur in many of these patients. Continuous nursing observation, as in an intensive care unit setting, is cost-prohibitive and impractical, given the large number of patients at risk. In an effort to address this problem, the author has created and tested the Apnea Prevention Device (APD), which is designed to detect the onset of hypoxia and instantly intervene to restore respiration and oxygen saturation in narcotized patients. The prototype APD used in this study consisted of a laptop computer running custom software, a pulse oximeter, and a nerve stimulator. Oxygen saturation data were acquired by the computer from the pulse oximeter, and stimuli to the patient were delivered either by headphones (verbal prompts) or a nerve stimulator (cutaneous). The APD program was written to analyze oximetry data and when indicated, deliver a series of stimuli of increasing intensity to arouse patients from narcosis. The device was tested on surgical patients in the postanesthesia care unit. An intervention delivered by the APD was scored as a success if the patient took a large tidal volume breath (as evidenced by chest rise) and there was a subsequent increase in oxygen saturation. The APD maintained a data log of oxygen saturations and interventions. In a subset of patients, it was possible to compare the functioning of the APD with routine nursing care. A total of 125 interventions were delivered by the APD to 10 patients with a 97% success rate. The depth of desaturations was less when the APD was in use than when patients received routine 1:1 nursing care. When the APD was functioning, the frequency with which nurses prompted the subjects to breathe was dramatically reduced. This study demonstrates that the prototype APD can successfully treat narcotic-induced respiratory depression in postoperative patients and does so in a manner that is superior to that provided by routine 1:1 nursing care. Such a device has the potential to decrease the morbidity associated with narcotic-induced respiratory depression in postoperative patients.