Figure 2

(a) The top part of the figure shows the endotoxin induced increase in ventilation in dogs, which then decreases as the animal's ventilatory muscles fail. The numbers at the top represent the mean values for PCO₂ in septic animals at each stage. Note how stable they remain, even with decreasing ventilation. The bottom shows the changes in diaphragmatic and intercostal muscle flows that were associated with the changes in ventilation. Reproduced with permission from Hussain and coworkers [24]. (b) An example of the loss of diaphragmatic endurance in rats treated for 3 days with Streptococcus pneumoniae. After 3 days phrenic nerves were stimulated at 10 Hz for 30 seconds and transdiaphragmatic pressure (Pdi) was measured. Single twitches are shown at the beginning and end of 30 seconds of stimulation. There was a marked decrease in tension in septic animals compared with controls. Reproduced with permission from Boczkowski and coworkers [68].