Role of high-frequency ventilation in surfactant-depleted lung injury as measured by granulocytes.

Granulocytes were collected from the lung lavage fluid of surfactant-depleted rabbits to assess the relationship between granulocyte-related lung injury and ventilatory mode. The number of lavaged granulocytes was determined after 2 and 4 h of conventional mechanical ventilation (2CMV and 4CMV, respectively) or high-frequency oscillatory ventilation (2HFO and 4HFO, respectively). Stimulated respiratory bursts were assayed by luminol-dependent chemiluminescence (LDCL) with N-formyl-methionyl-leucyl-phenylalanine (FMLP) stimulation in four groups of rabbits. The number of lavaged granulocytes significantly increased with ventilatory duration in the CMV mode but not in the HFO mode. Meanwhile, peak LDCL response value with FMLP stimulation in 4CMV was substantially lower than values in the other three groups. The decrease in the granulocyte LDCL response in 4CMV suggests oxygen metabolite exhaustion in the cells. CMV increasingly induced the accumulation of granulocytes with activated respiratory bursts in the alveolar spaces with ventilatory duration. HFO did not cause granulocyte accumulation, nor did it impair granulocyte function. The results suggest that HFO is useful for the prevention of lung injury related to activated granulocytes.