Indirect assessment of thoracic fluid balance following maximal exercise in man

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Abstract
A series of three studies was conducted to help determine the physiological mechanism responsible for the previously reported increase in residual volume following maximal exercise. Study I showed that in 18 male volunteers, residual volume and total lung capacity were significantly (P<0.05) increased over the pre‐exercise values through 30 and 15 min of recovery, respectively. Transthoracic electrical impedance was significantly decreased below the pre‐exercise value through 15 min of recovery. This suggests that there was an increase in intrathoracic fluid following exercise. By experimentally manipulating central blood volume via G‐suit inflation and venous occlusion, study II (n = 10) showed that post‐exercise residual volume was relatively insensitive to increases in intravascular fluid within the thorax. Study III (n = 5) showed that the post‐exercise diffusion capacity (DLco/VA was unchanged following exercise, despite an increase in the post‐exercise heart rate. It was concluded that a subclinical pulmonary oedema is present following maximal exercise. A logical sequence of events was proposed as a possible explanation for the response of residual volume following exercise.