Inspiratory Work, Power and Drive During Multiple Breath Extrinsic Resistive Loading in Healthy Adults

Abstract

An extrinsic resistive load (R) to breathing increases the work of breathing. The extrinsic airway resistive work (W) of breathing during inspiration is defined as: Waw = Paw * Vi.. The power (J) required to breathe with this load is defined as: Jaw = ∫ Waw*dt. With increasing R, the Waw and Jaw required to sustain minute ventilation (VE) increases. The respiratory control system in the brainstem provides an inspiratory drive over the inspiratory duration (Ti) to generate sufficient inspiratory pump force to move the air through the airways and into the alveoli. The element of inspiratory drive required to compensate for increased extrinsic resistance is a function of the inspiratory Paw generated over the Ti, hypothesized as the pressure‐time‐product: PtP = ∫ Paw*dt. Thus, we predicted the PtP must increase with increasing Jaw as a function of the magnitude of the R. In addition, we reasoned that sustained breathing against increased R's require increasing PtP to compensate for the Jaw required to sustain VE. Hence, we hypothesized during a 10‐breath R loading trial, the PtP for Breath 10 will be greater Breath 1 as a function of R. Finally, we hypothesized that the perception of breathing effort is directly proportional to the PtP and Jaw. Healthy participants were tested while breathing through a non‐rebreathing circuit with inspiratory flow‐resistive loads (R=0, 5, 10, 25, 50, 100 cmH2O/L/s). The subjects inspired for 10 consecutive breaths for each load magnitude in a randomized block order. Subjects estimated their perceived load intensity (MEInt) and unpleasantness (MEUn) for breaths 1, 5 and 10. VE was unchanged for all 10 breaths with all R loads. The Waw and Jaw increased with increasing R. The PtP significantly increased with increasing R and was directly proportional to the increase in Jaw. The PtP increased from breath 1 to 10 only for R=100 cmH2O/L/s. The MEInt and MEUn increased with increasing R directly proportional to the PtP and Jaw. The results of this study demonstrate the increase Waw associated with breathing against extrinsic R loads increases the Jaw required to sustain VE. The PtP (drive) increases proportionately to the Jaw. The MEInt and MEUn increased with the increased PtP and Jaw generating an increased sense of breathing effort and negative affective perception for loaded breathing.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.