Strain-induced growth of the immature lung

Zhang, Shaoping, Vicki Garbutt, and John T. McBride.Strain-induced growth of the immature lung. J. Appl. Physiol. 81(4): 1471-1476, 1996.Toinvestigate the relationship between strain and postnatal lung growth,two groups of weanling ferrets were tracheotomized: the study group wasexposed for 2 wk to a continuous positive airway pressure (CPAP) of 6 cmH₂O and the other group wasexposed to atmospheric pressure (control). Total lung capacity after 2 wk was ~40% higher in the CPAP-exposed animals than in the controlanimals (n = 19 for the control groupand 18 for the study group; P < 0.01). CPAP exposure was also associated with increases in lung weightand total lung protein and DNA contents. Lung recoil, measured in asubgroup of animals, was characterized by air-filled and saline-filledstatic expiratory pressure-volume curves. Neither in the air-filledlungs nor in the saline-filled lungs was there a significant differencebetween CPAP-exposed and control animals in lung recoil at equalfractions of total lung capacity. These data indicate that mechanicalstrain was associated with an acceleration of lung growth in immatureferrets. The preservation of volume-corrected lung recoil and theexpected contribution of surface forces and tissue forces to lungrecoil in CPAP-exposed animals suggest that this response did notinvolve simple lung distension but included a remodeling of the lungparenchyma.