The Portable Helicopter Oxygen Delivery System (PHODS) in the Altitude Chamber: Cerebral and Peripheral Blood Oxygen and Perceptual Vigilance

The Portable Helicopter Oxygen Delivery System (PHODS) provides supplemental oxygen (O2) to Army aircrew at altitudes up to 18,000 feet (ft) above mean sea level (MSL). Previous PHODS tests and evaluations (T&E) used conventional pulse oximetry to monitor peripheral blood O2 saturation (SpO2). The present T&E incorporates near infrared spectroscopic (NIRS) measures of regional cerebral blood O2 saturation (rSO2). Army aircrew (N = 22) assessed PHODS functionality and effectiveness in an altitude chamber during three challenges: 10 minutes of a visual reaction time test, 5 minutes of text reading, and 2 minutes of a physical workload challenge (self-paced squats). Throughout the T&E, SpO2 and rSO2 were measured continuously at ground level and at pressure altitudes of 14,000 and 17,800 ft MSL. Results indicate that the PHODS maintained constant SpO2 throughout all testing but not rSO2 in the presence of workload. The possible operational significance of this finding is discussed.