RESPIRATORY MECHANICS DURING FORWARD ACCELERATION*

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Abstract
The respiratory mechanics of forward acceleration were studied in 4 normal subjects. All of the lung volumes decreased proportionately with the exception of residual volume which became a larger fraction of the total lung capacity. The resting mid-pulmonary position decreased. As acceleration increased, intrapulmonic pressure increased for a constant volume, shifting the relaxation pressure-volume curve downward and to the right. Static and dynamic total pulmonary compliances decreased as a result of the decrease in functional residual capacity. Elastic work approximately doubled due to the work necessary to overcome acceleration resistance (PG). Non-elastic work did not change. Inspiration during 4 G acceleration was always active regardless of the end-expiratory position. It is suggested that respiratory mechanics during forward acceleration and negative pressure breathing are similar.