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Computation of respiratory heat exchanges
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 1, 1986
Summary
Two new equations estimate respiratory heat exchange, including sensible (WCV) and insensible (WEV) heat loss. These models are applicable across various atmospheric pressures and gas mixtures, crucial for understanding breathing in different environments.
Area of Science:
- Physiology
- Environmental Medicine
- Aerospace Medicine
Background:
- Accurate estimation of respiratory heat exchange is vital for understanding physiological responses to diverse environmental conditions.
- Existing methods may lack applicability across varying barometric pressures and gas compositions, limiting their utility in specialized settings.
- Quantifying sensible (WCV) and insensible (WEV) heat loss during respiration is essential for thermal comfort and safety.
Purpose of the Study:
- To propose and validate two sets of equations for estimating convective (sensible) and evaporative (insensible) respiratory heat exchanges.
- To ensure the applicability of these equations under various conditions, including sea-level, hypobaric, and hyperbaric environments.
- To provide a method for calculating heat exchange in both air and artificial gas mixtures.
Main Methods:
- Development of two distinct sets of equations to calculate WCV and WEV.
- Equations are designed for different environmental parameters: sea-level air (SLA), hypobaric/hyperbaric air (HA), and hypobaric/hyperbaric artificial atmospheres (HAA).
- Input parameters include inspired air temperature (TI), water vapor partial pressure (PIH2O), barometric pressure (PB), and for HAA, gas mixture density (rho mix) and specific heat (cp mix).
Main Results:
- The proposed equations provide estimates for WCV and WEV applicable to SLA, HA, and HAA conditions.
- Results can be expressed per liter of pulmonary ventilation (J x dm-3 BTPS) when physiological data are unavailable.
- When ventilation (V) is known, results are directly obtainable in power units (W).
Conclusions:
- The developed equations offer a versatile tool for assessing respiratory heat exchange across a wide range of environmental conditions.
- These equations are valuable for physiological research, particularly in scenarios involving altered atmospheric pressures or non-air breathing gas mixtures.
- The ability to express results in both energy per volume and power units enhances their practical application in diverse research and operational settings.