Respiratory drive during carbachol challenge in allergic sheep

Diaphragmatic activity is the standard assessment of respiratory neural out put but is difficult to measure and cannot be used for long-term clinical m onitoring. The tidal breathing minute ventilation ((V') over bar) and mean inspiratory flow (V-T/t(I)) reflect respiratory drive and can be monitored non-invasively using respiratory inductive plethysmography (RIP). Recent fi ndings indicate that peak inspiratory acceleration (PIA) correlates to diap hragmatic activity during CO2 rebreathing in piglets. The aim of the presen t study was to assess whether tidal breathing peak inspiratory acceleration reflects respiratory drive during carbachol challenge. Aerosolized carbach ol was administered to 15 allergic sheep until pulmonary resistance increas ed by at least 400%. After threshold dose, slight increases in (V') over ba r and V-T/t(I) were seen (8 and 5%, respectively; P=NS), while PIA increase d by 30% (P <0.05). The change in PIA was closely correlated to changes in (V') over bar and V-T/t(I) (r = 0.73, P <0.01 and r = 0.88, P <0.001, respe ctively). In conclusion, peak inspiratory acceleration reflected respirator y drive during bronchoprovocation. Further, this new measure of drive has t he potential to accurately estimate drive in chronic obstructive lung disea se where intrinsic positive end expiratory pressure prevents accurate selec tion of beginning inspiration necessary for computation of, e.g. V-T/t(I).