Comparison of BiPAP Nasal Ventilation and Ventilation via Iron Lung in Severe Stable COPD: Results
The characteristics of 11 patients are demonstrated in Table 1. All were male with an average age of 69 ± 5 years. Average FEV, was 0.71 ± 0.21 L (28 percent ± 9 percent of predicted values). Mild hypoxemia (Pa02, 66 ± 13.7 mm Hg) and minimal hypercapnea (PaC02, 45.1 ± 10.8 mm Hg) were noted in ABG on room air.
Response to BiPAP
Figure 2 shows an example of the recorded tracings from one of our patients. Deep breath tracings were used to confirm the optimal position of the electrodes. The EMG activities were suppressed gradually with the use of BiPAP However, the result was not constant for other patients. Data of the EMG activities of both diaphragm and sternocleidomastoid muscles are displayed in Figure ЗА, which shows no significant difference between the baseline and those obtained 40 min after the use of BiPAP The change of phase angle was also insignificant. The changes of Vt, Vt/ Ti, and RR were also insignificant (Fig 4A).
Before and 40 min after BiPAP, there was also no significant change in pulse rate (88.1 ± 11.2/min vs 86.3 ± 10.0/min), etC02 (36.3 ±13.4 mm Hg vs 35.5 ±9.3 mm Hg), or Sa02 (95.1 ±2.3 percent vs 95.6 ± 2.0 percent).
Pimax and Рктах were not improved after the use of BiPAP for 40 min either (-49.0 ±20.0 cm H20 vs -48.6 ±37.5 cm H20 and 65.4 ±24.5 cm H20 vs 66.4 ±24.4 cm H20).
When the FEV, of the patients was below 0.55 L, the reduction in iEMGst was quite obvious after the use of BiPAP for 40 min (Fig 5). Conversely, the EMG was not suppressed or even increased in some patients when the FEVj was above 0.55 L (Fig 5). The difference of AiEMGst between these two groups was statistically significant ( — 62.93 percent ±23.27 percent vs 32.45 percent ±42.79 percent, p = 0.0056). The comparison of patient age, pulmonary function, and ABG between these two groups was demonstrated in Table 2. Furthermore, the correlation between FEV! and AiEMGst was statistically significant (Fig 6, r = 0.59, p<0.05).
Response to Iron Lung
The iEMGdi and iEMGst did not change significantly after the use of the iron lung for 40 min (Fig 3B). Unlike BiPAP, no significant correlation between pulmonary function and the change of EMG activities could be found. The change in phase angle was not significant either. There were insignificant changes in Vt, Vt/Ti, and RR (Fig 4B).
There were also no significant changes in pulse rate (PR) (89.6±8.6/min vs 85.9± 13.3/min), etC02 (34.7 ±7.5 mm Hg vs 33.5 ±6.9 mm Hg), or Sa02 (95.6 ± 1.5 percent vs 95.6 ± 1.8 percent).
The PEmax was not improved after 40 min of iron lung (66.5 ± 24.5 cm H20 vs 63.5 ± 26.5 cm H20). The Pimax even decreased from —48.6±37.5 cm H20 to — 33.4 ±34.3 cm H20, but the change was not statistically significant.
Figure 2. Representative tracings from our patient 9 during deep breath, rest, and BiPAP ventilation. Deep breath was to confirm the optimal positions of the electrodes. The integrated EMG activity of sternocleidomastoid muscle (iEMGst) showed gradual improvement from rest to 40 min after BiPAP ventilation.
Figure 3. Left (A), Phase angle, EMGdi, and EMGst showed insignificant and highly variable change during rest and BiPAP ventilation of different duration. Right (B), Similar findings were noted during iron lung ventilation. Values represent mean ± SD.
Figure 4. (Left (A), These figures demonstrate insignificant changes in Vt, Vt/Ti, and RR between rest and BiPAP ventilation of different duration. Right (B), Similar findings were noted during iron lung ventilation. Values represent mean ± SD.
Figure 5. The change in iEMGst after 40 min use of BiPAP was divided by the baseline iEMGst to obtain AiEMGst. When baseline FEV, of the patients was below 0.55 L (n = 4, circles), iEMGst w’as markedly improved. Conversely, iEMGdi kept unchanged or even increasing in patients with FEV, above 0.55 L (n = 7, triangles). The AiEMGst between these two groups was statistically significant (- 62.93 percent ± 23.27 percent vs 32.45 percent ± 42.79 percent, p = 0.0056). The dash lines are the mean values of both groups. Values represent mean ± SD.
Figure 6. This figure illustrates significant correlation between FEV, of the patients and the change in iEMGst (n = II, r = 0.59, p<0.05).
Table 1—Characteristics of 11 Patients With Severe COPD
|FEV,, % pred||28||9|
Table 2—Comparison of Pulmonary Function and Arterial Blood Gases (ABG) Between the Patients With FEV, Above 0.55 L and Those With FEV, Below 0.55 L
|Patients With FEV, >0.55 L||Patients With FEV, <0.55 L||P|
|Age, yr||70 ±5||68±2||NSt|
|FEV,, L||0.84±0.15||0.47 ±0.03||0.0008|
|FEV,, % pred||34.3±7.6||19.5± 1.3||0.0017|
|FVC, L||2.29±0.44||1.53 ±0.24||0.0199|
|FEV./FVC||0.37 ±0.05||0.32 ±0.03||NS|
|Pa02*||65.1 ±10.9||68.3± 15.6||NS|
|pH*||7.46 ±0.06||7.42 ±0.02||NS|