Pulmonary gas exchange in elderly subjects

Abstract

P Pu ul lm mo on na ar ry y g ga as s e ex xc ch ha an ng ge e i in n e el ld de er rl ly y s su ub bj je ec ct ts s H. Guénard, R. Marthan Pulmonary gas exchange in elderly subjects. H. Guénard, R. Marthan. ©ERS Journals Ltd 1996. ABSTRACT: Although important alterations in structure and function develop with age, the hypothesis that the lungs are capable of maintaining adequate gas exchange for the maximum human life span is generally accepted. This hypothesis was examined by measuring arterial oxygen and carbon dioxide tension (Pa,O 2 and Pa,CO 2 ) alveolo-arterial differences in oxygen and carbon dioxide tension (PA-a,O 2 and Pa-A,CO 2 ), steady state transfer capacity of the lung for carbon monoxide (TL,CO,ss) as well as the gas exchange ratio (R) in a series of 74 healthy subjects aged more than 68 yrs (69-104 yrs). In addition, Pa,O 2 and Pa,CO 2 were measured in a series of 55 young healthy subjects, who acted as controls.In the elderly subjects, except for TL,CO,ss, there was no significant correlation between any of the other variables and age. However, for a given Pa,CO 2 , Pa,O 2 was always lower in the group of elderly subjects than in the group of young control subjects. TL,CO,ss, as well as TL,CO,ss/minute ventilation (V ' 'E) ratio, was correlated with age, according to the following regression equations: TL,CO,ss (mL·min -1 ·kPa -1 ) = 126-0.90 × age (yrs), and TL,CO,ss/V ' 'E (kPa -1 ×10 3 ) = 13.5-0.085 × age, respectively.These results show that arterial oxygen tension did not decrease with age in this series of elderly subjects. However, the decrease in steady-state transfer capacity of the lungs for carbon monoxide with age indicates that oxygen transport could be diffusion-limited in elderly subjects, at least when oxygen consumption is increased.

Función respiratoria en la senectud

“…Diversos estudios 25,[27][28][29][30] Los valores obtenidos con estas dos ecuaciones (Figura 2) se extrapolaron hasta los 80 años 31 . Sin embargo, las gasometrías en sujetos sanos de 90 y más de 100 años han detectado que en >70 a 75 años los valores de la PaO 2 medidos 30,33,34 , son mayores que los calculados por estas ecuaciones y que en edades >70-75 años, no existe una correlación significativa entre PaO 2 y los años de edad 33,34 (Tabla 3). En estos segmentos etáreos tampoco se encontró correlación entre edad y P [A-a] O 2 , aunque este gradiente es mucho más alto que en el adulto joven (promedio 33 ± 4,5 mmHg entre 69 y 104 años de edad 33 .…”

“…Ulteriormente en personas entre 69 y 104 años 33 , se ha detectado que a diferencia de lo que ocurre en jóvenes, el nivel de PaCO 2 no modifica la PaO 2 (Figura 3). Lo cual sugiere que en estas edades la hiperventilación empeora la distribución de la relación V'/Q' 33 .…”

Review article: Age related alterations in respiratory function — anesthetic considerations

“…28 The expected annual reduction in diffusing capacity approximates 0.3 and 0.2 mL·min -1 ·mmHg -1 in males and females, respectively, 9 and the changes are more pronounced after 40 yr of age. Women between the ages of 25 and 46 yr have the smallest annual decrease in diffusing capacity, suggesting a protective effect of estrogens, but after age 47 the yearly decline in diffusing capacity in women approaches that in men.…”

“…[35][36][37] Aging is also associated with a decline in the ability to perceive methacholine-induced bronchoconstriction when compared with younger subjects. 28 Blunting of the response to hypoxia and hypercapnia, as well as a lower ability to perceive respiratory sensations such as bronchoconstriction, represent a loss of important protective mechanisms which may result in lesser awareness of the disease and its delayed diagnosis in elderly patients. …”

“…Women between the ages of 25 and 46 yr have the smallest annual decrease in diffusing capacity, suggesting a protective effect of estrogens, but after age 47 the yearly decline in diffusing capacity in women approaches that in men. 29 The decrease in diffusing capacity is attributed to ventilation/perfusion mismatching, decline in pulmonary capillary blood volume 28 and the loss of the alveolar surface area. 30 …”