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Clinical InvestigationsEffect of Nasal Pressure Support Ventilation and External PEEP on Diaphragmatic Activity in Patients with Severe Stable COPD
Section snippets
MATERIALS AND METHODS
Seven patients (five male and two female) with severe COPD (FEV1 = 20 percent ± 6.9 of pred and FEV1/FVC = 35 percent ± 10.5) and respiratory muscle dysfunction (maximum inspiratory pressure [MIP] 44.6 ± 8.5 cm H2O) were studied after giving oral consent to a protocol approved by the Clinica del Lavoro Foundation of Pavia institutional ethics committee. All the patients were in a stable condition, as assessed by stability in blood gas values and pH in the preceding four weeks; indeed they had
RESULTS
One patient refused to swallow the gastric and esophageal balloons; therefore we could not record Pes and Pga swings and PTPdi. Another subject was unable to tolerate a PS of 20 cm H2O with or without PEEPe, while all the others tolerated NPSV at the different levels without any discomfort or complication. The actual pressure delivered measured at the mask for a PS of 10 and 20 cm H2O averaged 8.1 ± 0.2 and 15.9 ± 1.1 cm H2O, respectively; the effective PEEPe at the mask was 3.2 ± 0.3 cm H2O.
DISCUSSION
This study shows that NPSV acutely improves, in stable hypercapnic COPD patients, some indices of diaphragmatic activity such as Pdi, Edi, and PTPdi, increasing with the amount of PS used. These effects are enhanced by the application of external PEEP in these patients who all had auto-PEEP. Improved efficiency is not solely due to the action of NPSV in aiding the inspiratory muscles, but may also result from a different pattern of breathing, especially the marked decrease in respiratory
CONCLUSION
In conclusion, we demonstrated that NPSV is able to significantly reduce the diaphragmatic activity as assessed by a decrease in Pdi, Edi, and PTPdi in stable severe hypercapnic patients; these effects may be enhanced by the application of PEEPe in patients who showed dynamic PEEPi during spontaneous breathing. PS is usually tolerated up to values of 20 cm H2O when given by nose mask and may also acutely improve blood gases, while significantly reducing frequency.
These findings indicate that
ACKNOWLEDGMENT
As usual, the authors wish to thank Dr. R. C. Stanner for reviewing the English of the manuscript.
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Manuscript received December 9; revision accepted May 12.