The effect of age on respiratory function of fischer-344 rats

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Abstract
Respiratory function of adult male and female specific-pathogen-free Fischer-344 rats in 3 age groups was measured by plethysmography. Groups included young adults at 102 days, midadults at 53.8 days and old adults at 815 day of age. Measurements included spontaneous breathing patterns, subdivisions of lung volume, quasistatic lung pressure-volume relationships and CO diffusing capacity. The midadult and old rats were larger in body size than the young rats and had larger values for breathing pattern variables and lung volumes. The midadult rats had lower values for functional residual capacity and residual volume and a greater quasistatic lung compliance than the young or old rats. There were no age-related differences in the position of the midportion of the quasistatic pressure-volume curve; when volumes were expressed as percentages of maximal lung volume, the curves of the older groups lay to the right of the curve for the youngest group. Although these differences suggested the possibility of a slight reduction of respiratory efficiency in the old rats, there was no clear indication of a major loss of respiratory function with age. Differences between males and females were largely related to body size, although young and midadult females had larger size-adjusted values for lung volumes than males. Rat lungs undergo significant changes during adulthood due primarily to continued lung growth; however, the pattern of change may be different than that of man and the degrees of the changes, suggesting a possible function loss in aged subjects, were less than those observed in man at an equivalent portion of the life span.