Flow-volume curves and total pulmonary resistance in normal bonnet and rhesus monkeys.

We measured expiratory flow-volume curves and total pulmonary resistance in 15 normal, anesthetized, upright bonnet (Macaca radiata) and 8 rhesus (M. mulatta) monkeys. Absolute maximum flows are about half that found in humans, but, if expressed in vital capacities per second, monkey flows are about four times that of humans. However, irrespective of flow rate, the typical shape of maximum expiratory flow-volume (MEFV) curves of rhesus monkeys is similar to that of normal young adults and that of bonnet monkeys is similar to that of normal older adults. Flow-limiting mechanisms that may determine MEFV curve shape and explain the differences and similarities of monkey and human MEFV curves are discussed. We propose that differences in function between bonnet and rhesus monkeys relates to the concept of dysanaptic lung growth that evolved to subserve behavioral differences between the two species of monkey.