Critical care medicine
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Critical care medicine · Sep 1984
Comparative StudyGas exchange during conventional and high-frequency pulse ventilation in the surfactant-deficient lung: influence of positive end-expiratory pressure.
High-frequency pulse ventilation (HFPV) was compared to conventional ventilation (CV) in a model of severe respiratory failure induced by serial lung lavages with warm saline in 8 mongrel dogs. Before the lavage, during HFPV at 4 Hz with a pulse volume (PV) of 125 ml, mean PaO2 was 107 torr and mean PaCO2 was 34 torr. After the last lavage, during CV at an inspired oxygen fraction FIO2 of 1.0 and a tidal volume (VT) of 535 ml, the PaO2 averaged 60 torr and PaCO2 was 45 torr. ⋯ The corresponding mean airway pressure (Paw) was about 20 cm H2O. Thus, application of PEEP during HFPV at low PV did not improve PaO2 even when measured Paw approximated 20 cm H2O. This suggests that HFPV with high PV is more effective than either CV with PEEP, or HFPV with low PV and PEEP.
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Critical care medicine · Sep 1984
Comparative StudyHigh-frequency positive-pressure ventilation with the MA-1 ventilator.
A conventional, low-frequency ventilator was modified to ventilate dogs at high frequencies of 85 to 185 cycle/min while cardiovascular and pulmonary variables were monitored. Although gas transport was adequate, cardiac output was diminished when compared to low-frequency ventilation. The addition of an in-line pneumotachograph markedly increased PaCO2 during high-frequency ventilation. Carbon dioxide transport was primarily dependent upon the magnitude of the tidal volume at all high frequencies tested.
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Critical care medicine · Sep 1984
Effect of continuous positive airway pressure on lung mechanics during high-frequency jet ventilation.
Six mongrel dogs were studied in a body plethysmograph to ascertain the effects of continuous positive airway pressure (CPAP) during high-frequency jet ventilation (HFJV), using an open system allowing gas entrainment. Increases in CPAP significantly reduced tidal volume. ⋯ At constant CPAP, tidal volume correlated well with the difference between peak airway pressure and CPAP, while the FRC change was correlated with the difference between end-expiratory pressure and CPAP. The relationship between end-expiratory airway pressure and total change in FRC was predictable from lung compliance at all levels of CPAP.
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Critical care medicine · Sep 1984
Measuring gas leakage from bronchopleural fistulas during high-frequency jet ventilation.
A simple volumetric system can be used to measure leakage from bronchopleural fistulas even when inspiratory volumes are unknown or when constant suction is required.