Project Title: Effects of Reduced Pressures on Health-Compromised Populations
Anticipated Outcome: The data from this research will enable the FAA and the aerospace industry to ensure that airworthiness (FAR 25.841) regulations for cabin pressure are appropriate for today's flying public.
Project Summary: During normal flight operations, cabins are maintained at pressures equivalent to altitudes of 8000 ft (2.4 km) or less above sea level. At this level, the partial pressure of oxygen in arterial blood flow drops to 8.3 - 8.9 kPa (62 - 67 mm Hg) versus 12.7 - 13.3 kPa (95 - 100 mm Hg) at sea level. FAR 25.841 specifies the cabin pressures required in airliner cabins, but this is based upon older studies of healthy military pilots and crew. Serious health effects could occur in people with compromised health (e.g., cardiovascular disease) as a result of our aging population. New guidelines may be required to decrease health risks for people with susceptible medical conditions.
A panel with scientific expertise in pulmonary physiology, neurocognitive response, cardiology and aerospace medicine was assembled and reviewed existing scientific literature and previous un-published studies related to the physiologic and cognitive responses to reduced partial pressure of arterial oxygen (SAO2) in healthy adults. Based upon this review, the panel recommended additional studies related to assessment of health and safety plus physiologic and cognitive function under conditions of prolonged reduced SAO2. The panel supported exploring some of these altitude/pressure effects through a chamber-based flight simulation study.
The chamber study was conducted at the FAA's Civil Aeromedical Institute in Oklahoma City and examined participants during simulated altitude and ground conditions to better understand the potential physiological effects of flying at altitude. In total the study enrolled 41 participants, 40 of whom participated in two chamber runs (one altitude and one ground). Initial analyses is include altitude and the outcomes of SAO2 levels and fatigue. These outcomes are being examined in the context of co-morbidities, demographics (i.e. gender, age, ethnicity), subject group (healthy, cardiovascular, smoker), body mass index, pre-chamber EKGs, pre-chamber blood pressure, flight seats, trial day, CO2, and temperature.
Southwest Airlines recently (June 2009) facilitated a follow-up in-flight study on six of the participants of the chamber study during flights from Oklahoma City to Baltimore, Baltimore to Las Vegas, and Las Vegas to Oklahoma City. Data similar to that collected in the environmental chamber study were collected in the in-flight measurements including the following: Lifeshirt system physiological data, cognitive data, biological specimen data, and participant survey self-report data.
Research Team:
John D. Spengler, Harvard School of Public Health
Eileen McNeely, Harvard School of Public Health