Light- and electron microscopic investigations of pulmonary tissue after high-frequency positive-pressure ventilation (HFPPV).
Narcotisized dogs were artificially ventilated for periods of two to five hours with HFPPV. During this time the blood gases, pH and bases were controlled. In spite of sufficient oxygenation and CO2-elimination, a metabolic acidosis developed which could not be fully compensated by the addition of buffer solutions. In light and electron microscopy these lungs did not differ significantly from control lungs. Haemorrhages or atelectases were never observed. Type I cells as well as Type II cells in the alveoli are unchanged, i.e. the Type II cells were not depleted but contained numerous typical lamellar bodies with a diameter of 0.4-1 mu. The blood gas barrier was not widened and was ca. 3000 A wide. The alveolar surface was coated by an often fragmented electron-dense film (monolayer of the surfactant).