Significance of Cardiogenic Mixing in Dog Lungs
Since the early observations of DuBois et al. (1952) and of West and Hugh-Jones (1961) it has been known that the heart beat causes fluctuations of airway pressure. Variations of intrapulmonary pressure that occur synchronously with the heart beat were suggested to result from the cardiac motion itself or from cyclic changes of intrathoracic blood volume. Airflow variations caused by the beating heart in lobar and segmental bronchi have been determined in patients at bronchoscopy and found to occur asynchronously, flow increasing in one airway while decreasing in another (West and Hugh-Jones, 1961). The mechanisms underlying cardiogenic intrapulmonary gas flow, changes in heart volume or alterations in shape and position of the heart, are still controversial. Recent evidence suggests that the total heart volume remains essentially unchanged during the cardiac cycle (Hoffman and Ritman, 1985) and would therefore favour cyclic changes of shape and/or position of the heart causing airway pressure swings.
KeywordsHeart Beat Cardiac Action Beating Heart Heart Arrest Intrathoracic Blood Volume
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