G. G. Weinmann

Interaction between high frequency jet ventilation and cardiovascular function

We have studied the interaction of high frequency jet ventilation with cardiovascular pressures and flows. Results in dogs show that the amplitude of all intrathoracic pressures and flows fluctuate with a frequency equal to the difference between the heart rate and ventilator rate. The magnitude of this amplitude variation may be sufficient to obliterate periodically the pulsations in pulmonary artery and right atrial pressures. It is also shown that these cardiovascular beats can occur when the ventilator rate is close to integral multiples of the heart rate. Direct measurement of pleural pressure and the observation that the beats are markedly reduced when the chest is open support the hypothesis that the primary mechanism responsible for these beats is the interaction of the respiratory fluctuations in pleural pressure with the cardiacgenerated pressure pulsations.

Gas transport during high-frequency ventilation: Theoretical model and experimental validation

AbstractWe present a theoretical model of gas transport through the dead space during high-frequency ventilation (HFV) with volumes less than dead space volume. The analysis is based on the axial distribution of transit times of gas moving through the dead space. The model predicts that for tidal volumes (V) much less than dead space (Vd), gas exchange will be proportional to the product of frequency (f) and V2. If gas transport is analyzed in terms of Ficks law, then the effective diffusion coefficient (Deff) can be shown to be equal to fV2 times a constant, whose value equals the square of the coefficient of dispersion of axial transit times through the dead space

Effect of high-frequency ventilation on histamine-induced lung injury in dogs

(\sigma _t /\bar t)^2

Evidence for ozone-induced small-airway dysfunction: lack of menstrual-cycle and gender effects.

. Experimental results in straight tubes fit the predictions of this model quite well. A

Model of gas transport during high-frequency ventilation

(\sigma _t /\bar t)

Effect of tidal volume and frequency on the temporal fall in lung compliance

through the entire dead space of about 30% is more than sufficient to account for gas exchange during HFV in physical models or in intact animals. An axial dispersion of this magnitude can be measured directly from a typical Fowler dead space determination in healthy subjects.