Acute thoracoabdominal and hemodynamic responses to tapered flow resistive loading in healthy adults

Abstract

We investigated the acute physiological responses of tapered flow resistive loading (TFRL) at 30, 50 and 70 % maximal inspiratory pressure (PI_max) in 12 healthy adults to determine an optimal resistive load. Increased end-inspiratory rib cage and decreased end-expiratory abdominal volumes equally contributed to the expansion of thoracoabdominal tidal volume (captured by optoelectronic plethysmography). A significant decrease in end-expiratory thoracoabdominal volume was observed from 30 to 50 % PI_max, from 30 to 70 % PI_max, and from 50 to 70 % PImax. Cardiac output (recorded by cardio-impedance) increased from rest by 30 % across the three loading trials. Borg dyspnoea increased from 2.36 ± 0.20 at 30 % PI_max, to 3.45 ± 0.21 at 50 % PI_max, and 4.91 ± 0.25 at 70 % PI_max. End-tidal CO₂ decreased from rest during 30, 50 and 70 %PI_max (26.23 ± 0.59, 25.87 ± 1.02 and 24.30 ± 0.82 mmHg, respectively). Optimal intensity for TFRL is at 50 % PI_max to maximise global respiratory muscle and cardiovascular loading whilst minimising hyperventilation and breathlessness.

Keywords: Cardiac output; Inspiratory muscle training; Thoracoabdominal volumes.