The effect of bilateral thoracoplasty on lung development in fetal sheep.

The relationship of breathing movements to lung development in the ovine fetus was investigated by partially removing ribs on each side of the chest and closing the deficiencies with silicone membranes at 114 days of gestation; the increase in compliance of the chest wall that resulted caused blunting of the amplitude of phasic negative pressures recorded in the trachea to less than 10 torr. Compared to sham operated controls (n = 5), the lungs of the thoracoplasty group (n = 5) at term weighed significantly (P less than 0.05) less, both wet (1.5 +/- 0.2 v. 2.3 +/- 0.1% of body weight) and dry (0.14 +/- 0.01 v. 0.18 +/- 0.01% of body weight. In addition, DNA content of the thoracoplasty group was less than that of the control group (0.47 +/- 0.05 mg v. 0.72 +/- 0.20 mg). Distensibility of the left lung with air at 40 cmH20 was less than in the thoracoplasty group than in controls (10.0 +/- 2.0 v. 18.9 +/- 3.0 ml.kg-1 body weight) but no differences were found in the concentrations of saturated phosphatidylcholine in lung tissue and lavage fluid, in DNA concentrations or in the amount of lung water (as % of wet weight of lung). It is concluded that phasic negative pressures of normal intensity are necessary for normal development of the fetal lungs.