Expiratory muscle loading increases intercostal muscle blood flow during leg exercise in healthy humans.
We investigated whether expiratory muscle loading induced by the application of expiratory flow limitation (EFL) during exercise in healthy subjects causes a reduction in quadriceps muscle blood flow in favor of the blood flow to the intercostal muscles. We hypothesized that, during exercise with EFL quadriceps muscle blood flow would be reduced, whereas intercostal muscle blood flow would be increased compared with exercise without EFL. We initially performed an incremental exercise test on eight healthy male subjects with a Starling resistor in the expiratory line limiting expiratory flow to approximately 1 l/s to determine peak EFL exercise workload. On a different day, two constant-load exercise trials were performed in a balanced ordering sequence, during which subjects exercised with or without EFL at peak EFL exercise workload for 6 min. Intercostal (probe over the 7th intercostal space) and vastus lateralis muscle blood flow index (BFI) was calculated by near-infrared spectroscopy using indocyanine green, whereas cardiac output (CO) was measured by an impedance cardiography technique. At exercise termination, CO and stroke volume were not significantly different during exercise, with or without EFL (CO: 16.5 vs. 15.2 l/min, stroke volume: 104 vs. 107 ml/beat). Quadriceps muscle BFI during exercise with EFL (5.4 nM/s) was significantly (P = 0.043) lower compared with exercise without EFL (7.6 nM/s), whereas intercostal muscle BFI during exercise with EFL (3.5 nM/s) was significantly (P = 0.021) greater compared with that recorded during control exercise (0.4 nM/s). In conclusion, increased respiratory muscle loading during exercise in healthy humans causes an increase in blood flow to the intercostal muscles and a concomitant decrease in quadriceps muscle blood flow.
Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, M. Simou, and G. P. Livanos Laboratories, Athens, Greece.
Dimitris
D
Athanasopoulos
Zafeiris
Z
Louvaris
Evgenia
E
Cherouveim
Vasilis
V
Andrianopoulos
Charis
C
Roussos
Spyros
S
Zakynthinos
Ioannis
I
Vogiatzis
D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity; D002302:Cardiac Output; D002307:Cardiography, Impedance; D004396:Coloring Agents; D015444:Exercise; D005080:Exercise Test; D045853:Exhalation; D006801:Humans; D007208:Indocyanine Green; D007366:Intercostal Muscles / Q000098:blood supply* / Q000378:metabolism; D035002:Lower Extremity; D008297:Male; D009119:Muscle Contraction; D010101:Oxygen Consumption; D052097:Quadriceps Muscle / Q000098:blood supply* / Q000378:metabolism; D012039:Regional Blood Flow; D019265:Spectroscopy, Near-Infrared; D013318:Stroke Volume; D013997:Time Factors; D055815:Young Adult
D004396:Coloring Agents; D007208:Indocyanine Green