The effect of altitude and intensity of physical activity on the exergy efficiency of respiratory system

Izabela Batista Henriques, Carlos Eduardo Keutenedjian Mady, Cyro Albuquerque Neto, Jurandir Itizo Yanagihara, Silvio Oliveira Junior
3.516 757


The effect of altitude on exercise performance of lowlanders has long been discussed, but it is still unclear whether the performance reduction is related to inefficiency of the respiratory system, body tissues or both. In the present work, exergy analysis was applied to the human body in order to compare its exergy efficiency under basal conditions and during physical activity at sea level and high altitudes for different periods of acclimatization. Two control volumes were analyzed: respiratory system and human body as a whole. Data concerning mass and energy balances of the body and respiratory system were obtained from models available in the literature, which were modified based on medical literature to simulate the responses to physical activity at high altitude for different periods of acclimatization. The results indicated that the respiratory system exergy efficiency is reduced at high altitudes and under physical activity, while exergy efficiency of the body increases for both parameters, which may indicate that the discomfort reported at high altitudes is mostly related to the respiratory system than to the other ones. Concerning the acclimatization period, its influence was more pronounced on the respiratory system.


Exergy analysis; exergy efficiency; respiratory system; altitude; physical activity

Full Text:




ar arterial body body bl blood c convective dest destroyed e evaporative ex expired g gas in inflow liq liquid M metabolic out outflow r radiative resp respiration ΔT due to temperature variation ve venous WOB work of breathing References Prigogine, I., Wiame, J. Biologie et Thermodynamique des phenomenes irreversibles. Experimentia, 2(11):451453, 1964.

Zotin, A. I., Zotina, R. S. Thermodynamics aspects of developmental biology. J. Theoretical Biology, 17,5775, 1967.

Balmer, R. T. Entropy and aging in biological systems. Chemical Engineering Communications, 17, 171-181, 19 Aoki, I. Entropy principle for human development, growth and aging. J. Theoretical Biology, 150, 215-223, 19 Silva, C., Annamalai, K. Entropy generation and human aging: lifespan entropy and effect of Physical Activity Level. Entropy, 10,100-123, 2008.

Silva, C., Annamalai, K. Entropy generation and human aging: lifespan entropy and effect of diet composition and caloric restriction diets. J. Thermodynamics; 2009:1-10, 2009.

Mady, C. E. K., Ferreira, M. S., Yanagihara, J. I., Saldiva, P. H. N., Oliveira Junior, S. Modeling the exergy behavior of human body. Energy, 4, 546-553, 20 Batato, M., Borel, L., Deriaz O., Jequier, E. Analyse exergétique théorique et expérimentale du corps humain. Entropie, 26, 120-130, 1990.

Prek, M. Thermodynamic analysis of human heat and mass transfer and their impact on thermal comfort. Int. J. Heat and Mass Transfer,48, 731-739, 2005.

Prek, M. Thermodynamical analysis of human thermal comfort. Energy, 31, 732-743, 2006.

Prek, M., Butala, V. Principles of exergy analysis of human heat and mass exchange with the indoor environment. Int. J. Heat and Mass Transfer, 48, 731739, 2010.

Simone, A., Kolarik, J., Iwamatsu, T., Asada, H., Dovjak, M., Schellen, L., Shukuya, M., Olesen, B.W. A relation between calculated human body exergy consumption rate and subjectively assessed thermal sensation. Energy and Buildings, 43, 1-9, 2011.

Mady, C. E. K., Ferreira, M. S., Yanagihara, J. I., Saldiva, P. H. N., Oliveira Junior, S. Second law of thermodynamics and human body. Engenharia Térmica (Thermal Engineering), 10, 88-95, 2011.

Ferreira, M. S., Yanagihara, J. I. A transient threedimensional heat transfer model of the human body. International Communications in Heat and Mass Transfer, 36, 718–724, 2009.

Mady, C. E. K., Albuquerque Neto, C., Fernandes, T. L., Hernandez, A. J., Saldiva, P. H. N., Yanagihara, J. I., Oliveira-Junior, S. Exergy performance of human body during physical activities. Energy, 62, 370-378, 2013.

Albuquerque-Neto, C., Pellegrini, L.F., Ferreira, M.S., Oliveira Jr, S., Yanagihara, J.I. Exergy analysis of human respiration under physical activity. Int. J. Thermodynamics,13, 105-109, 2010.

Rahman, A. A novel method for estimating the entropy generation rate in a human body. Thermal Science, 11, 75-92, 2007.

Albuquerque, C.; Yanagihara, J. I., Turri, F. A carbon monoxide transport model of the human respiratory system applied to urban atmosphere exposure analysis. J. Brazilian Society of Mechanical Sciences and Engineering, 30, 253-260, 2008.

Mady, C. E. K., Oliveira-Junior, S. Human body exergy metabolism. Int. J. Thermodynamics, 16, 73-80, 20 Cavagna, G. A., Kaneko, M. Mechanical work and efficiency in level walking and running. J. Physiology, 68, 467-481, 1977.

Fritts, H. W., Filler, Jr J., Fishman, A. P., Cournand, A. The efficiency of ventilation during voluntary hyperpnea: studies in normal subjects and in dyspneic patients with either chronic pulmonary emphysema or obesity. J. Clinical Investigation, 38, 1339–1348, 1959. ASCE: American Society of Civil Engineers. The ASCE Standardized reference evapotranspiration equation. In: Final Report of Environmental and Water Resources Institute of The American Society of Civil Engineers, 2005.

American Society of Heating, Refrigerating and AirConditioning Engineers, Physiological principles and thermal comfort (ASHRAE). In: Handbook of Fundamentals, Atlanta, 2009.

Bärtsch, P., Saltin, B. General introduction to altitude adaptation and mountain sickness. Scandinavian J. Medicine & Science in Sports, 18, 1-10, 2008.