Article Figures & Data
Figures
- Fig. 1.
For inspiratory load compensation testing, this threshold positive expiratory pressure (PEP) training device was inverted and connected to a respiratory sensor (black arrow). The subject was briefly disconnected from the ventilator, and the sensor was connected directly to the tracheostomy tube. The valve of the training device remained closed until sufficient inspiratory pressure was generated to overcome the 10 cm H2O load. Once the threshold pressure was reached, the valve opened, permitting inspiratory air flow (white arrow). Expiration was unimpeded by the training device.
- Fig. 2.
Progression of spontaneous breathing trials administered during inspiratory muscle strength training study interventions. Subjects who could not initially tolerate at least 1 hour of spontaneous, unassisted breathing (right) underwent trials of reduced pressure support or CPAP (left).
- Fig. 3.
Maximum inspiratory pressure did not significantly differ between the weaned and unweaned groups (P = .24). In both groups the maximum inspiratory pressure increased after inspiratory muscle strength training (IMST). * Analysis of variance main effect P = .03. The data bars represent the mean values and the whisker bars represent the standard deviations.
- Fig. 4.
Correlation between maximum inspiratory pressure and inspiratory load compensation (ILC) ventilatory variables in the 16 difficult-to-wean subjects, prior to inspiratory muscle strength training (IMST), with a 10 cm H2O load. Before IMST the maximum inspiratory pressure in the subjects who ultimately weaned from mechanical ventilation after IMST (shaded data points) significantly correlated with peak inspiratory flow (r = 0.64, P = .008), and there was trend in inspired VT (r = 0.45, P = .08). The white data points represent the subjects who failed to wean. In contrast, no linear relationship was found between maximum inspiratory pressure and inspiratory or expiratory timing during ILC.
- Fig. 5.
Inspiratory load compensation responses before and after inspiratory muscle strength training (IMST) in the unweaned versus weaned subjects, with a 10 cm H2O load. In the weaned subjects peak inspiratory flow was significantly greater (P = .02) and inspired tidal volume was significantly larger (P = .03), both before and after IMST. The duty cycle (ratio of inspiratory time to total respiratory cycle time), inspiratory time, and expiratory time (not shown) were similar between the groups. * Main effect for weaning outcome P < .05. In each data bar the horizontal line represents the median, the top and bottom of the bar represent the IQR, and the whisker bars represent the 95th percentiles.
- Fig. 6.
Detailed inspiratory load compensation performance before and after inspiratory muscle strength training (IMST) in the weaned subjects. After IMST the peak inspiratory flow was significantly larger (* main effect P = .03), tidal volumes of all breaths were significantly larger († P = .007), and duty cycle was significantly longer († main effect for IMST P = .049). Duty cycle was also significantly longer with greater loads (‡ P = .048). In contrast, inspiratory time did not change after IMST. In each data bar the horizontal line represents the median, the top and bottom of the bar represent the IQR, and the whisker bars represent the 95th percentiles.
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