Efficacy of Positive vs Negative Pressure Ventilation in Unloading the Respiratory Muscles: Results (2)
Figures 2 and 3 summarize the effect of PPV and NPV in both normals and patients while receiving AV To maintain patient comfort, the Vt and Ve were higher during PPV as compared with QB and NPV (p = 0.01 or p = 0.05). Consequently, the etC02 was significantly lower during PPV (p = 0.01). A comparable Ve could not be achieved during NPV despite high negative pressures (mean = – 48 cm H20). The iEMG in absolute values showed a significant reduction for PPV as compared with QB (p = 0.01) and for PPV compared with NPV (p = 0.05). The difference between NPV and QB was not significant. Because Vt and Ve were noted to be higher during PPV, the iEMG was normalized for both Vt and Ve. This did not alter the results apart from a significant decrease in iEMG/VE when NPV was compared with QB. ventolin inhaler
Figure 2 represents the iEMG during assisted ventilation. The iEMG during PPV was reduced to 47 percent of the QB value while iEMG/VE and iEMG/ Vt were reduced to 29 percent and 24 percent, respectively. The reduction of iEMG during NPV was not significant. The remaining graphs in Figure 2 illustrate the greater reduction in iEMG/VE and iEMG/VT from QB and NPV achieved during PPV (p = 0.01). Although there was significant reduction in iEMG/VE during NPV as compared with QB (p = 0.05), this was not seen with iEMG/Vr.
Figure 2. This illustrates the reduction in EMC, EMG/Vt, and EMG/Ve for all subjects during PPV (open circles) and NPV (filled circles). (* PPV< QB, Tbkey A p = 0.01; + NPV<QB p = 0.05; and PPV<NPV during ventilation, p = 0.05 for EMG and EMG/Ve and p = 0.01 for EMG/Vt.)
Figure 3. Reduction in peak Pdi, PTI, and CV-Vt for all subjects during PPV (open circles) and NPV (filled circles). (* PPV<QB, Tukey A p = 0.01; + NPV<QB p = 0.01; and PPV<NPV, p = 0.05 for PTI and p = 0.01 for CV-Vt.)