Respiratory mechanics in normal bonnet and rhesus monkeys

We measured lung volumes and quasi-static volume-pressure relationships in 22 normal upright bonnet (Macaca radiata) and 12 rhesus (M. mulatta) monkeys. In comparison with interspecies pulmonary function/body weight regressions our monkeys' lung volumes are larger and their lungs are considerably more compliant, but their chest wall compliance is similar to a wide range of mammalian species. However, chest wall compliance of our monkeys was found to be considerably less than that of other more commonly used experimental mammals such as dogs, cats, and rodents. The monkey chest walls were found to be about four times as stiff (3.3 +/- 0.1 (ml/cmH2O)/kg), whereas their lungs were nearly twice as compliant (9.2 +/- 0.7 (ml/cmH2O)/kg) compared to those of supine beagle dogs. Thus, their stiff chest wall sets their functional residual capacity (64.1 +/- 1.2% TLC30) at a much larger percentage of total lung capacity (TLC30) than that of the supine beagle dog (33.8% TLC30). Residual volume (13.2 +/- 1.9% TLC30) equaled the trapped gas volume after bilateral thoracotomy and was set by airway closure. We found more hysteresis area in the chest wall than in the lungs. Our measurements indicate that the static mechanical behavior of the respiratory system of the monkey compares well to man and that the monkey has considerable merit as an animal model for human respiratory function and disease research.