Indirect assessment of thoracic fluid balance following maximal exercise in man

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 (D-Lco/V-A 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.