The influence of a low air pressure environment on human metabolic rate during short-term (< 2 h) exposures

Abstract

Passengers in aircraft cabins are exposed to low-pressure environments. One of the missing links in the research on thermal comfort under cabin conditions is the influence of low air pressure on the metabolic rate. In this research, we simulated the cabin pressure regime in a chamber in which the pressure level could be controlled. Three pressure levels (101/85/70 kPa) were tested to investigate how metabolic rate changed at different pressure levels. The results show that as pressure decreased, the respiratory flow rate (RFR) at standard condition (STPD: 0°C, 101 kPa) significantly decreased. Yet the oxygen (O ) consumption and carbon dioxide (CO ) production significantly increased, as reflected in the larger concentration difference between inhaled and exhaled air. A significant increase in the respiratory quotient (RQ) was also observed. For metabolic rate, no significant increase (P > 0.05) was detected when pressure decreased from 101 kPa to 85 kPa; however, the increase associated with a pressure decrease from 85 kPa to 70kPa was significant (P < 0.05). Empirical equations describing the above parameters are provided, which can be helpful for thermal comfort assessment in short-haul flights.

A study of thermal comfort in residential buildings on the Tibetan Plateau, China

“…In order to study the effects of hypobaric conditions on people's thermal responses, Ohno H et al [40] conducted experiments to clarify the interactive effects between barometric and thermal events on people's thermal comfort under hypobaric conditions (pressures about 30% below that at sea level) and the results showed that some physiological features change when the altitude increases which leads to subjects finding it difficult to express their thermal state. Cui et al [41] studied the effect of low pressure on human physiological responses in an artificial chamber, and found significant effects when it decreased to 85/70kPa. Wang, H. et al [42] conducted an experiment in a decompression chamber to simulate the hypobaric conditions, and found that people become more sensitive to draught and expect lower air movements.…”

A Review about Thermal Comfort in Aircraft

“…The metabolic rate under four different pressure levels ( 1 atm, 0.95 atm, 0.9 atm, 0.8 atm ) and three different air temperature levels (22°C, 25°C, 28°C) were measured. Cui et al [58] studied the effect of low pressure environment on human metabolic rate. The metabolic rate under three different pressure levels (101 kPa, 85 kPa, 70 kPa) was measured.…”