Figure 2. Ventilation inhibits alveolar growth.

(A) Histology after mechanical ventilation: (A1) non-ventilated 7-day old rat (A2) 7-day old rat ventilated for 12 h, (A3) 7-day old rat ventilated for 24 h, (A4) non-ventilated 8-day old rat. (B) Mechanical ventilation for 12 and 24 h significantly increased alveolar airspace (reduction in tissue-to-air ratio (A) as well as increase in mean linear intercept (D)) but decreased number of elastin-positive secondary septa (C). Medians with 25^th and 75^th quartiles are shown, bars are 5^th and 95^th percentiles, n = 12 rat pups per time group. MV, mechanical ventilation. * p<0.05.