Effect of hyperinflation and atelectasis on fluid accumulation in the puppy lung

The effects of hyperinflation and of atelectasis on accumulation of fluid in the lung was studied in 12 anesthetized spontaneously breathing puppies. Vascular pressures were raised and the plasma colloid osmotic pressure was reduced by the infusion of 0.9% saline thus promoting the formation of pulmonary edema. A tracheostomy was performed and the left lower lobe catheterized in all puppies. In five puppies hyperinflation of the left lower lobe was achieved by applying a continuous positive airway pressure (CPAP) of 10 Torr. In seven other puppies the left lobe was made atelectatic by occluding its bronchus after ventilating the lungs with 100% oxygen. The right lung was ventilated to ambient pressure in all puppies. The extravascular lung water content was determined by the difference in wet and dry lung weights corrected for residual blood. We found that hyperinflation produced by CPAP enhanced and atelectasis opposed fluid accumulation in the puppy lung.