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

Abstract

The respiratory function of adult male and female specific pathogen free Fischer-344 rats in three age groups was measured by plethysmography. Groups included young adults at 102 days, mid-adults at 538 days and old adults at 815 days of age. Measurements included spontaneous breathing patterns, subdivisions of lung volume, quasistatic lung pressure-volume relationships and CO diffusing capacity. The mid-adult and old rats were larger in body size than the young rats and had larger values for breathing pattern variables and lung volumes. The mid-adult 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 mid-portion of the quasistatic pressure-volume curve; however, 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 mid-adult females had larger size-adujsted values for lung volumes than males. Rat lungs undergo significant changes during adulthood, due primarily to continued lung growth, but 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.