Chest
Volume 105, Issue 4, April 1994, Pages 1053-1060
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Respiratory Muscle Rest Using Nasal BiPAP Ventilation in Patients With Stable Severe COPD

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To more systematically evaluate the effect of respiratory muscle rest on indices of ventilatory function, nine outpatients with stable, severe COPD were treated with nasal pressure-support ventilation delivered via a nasal ventilatory support system (BiPAP, Respironics, Inc) for 2 h a day for 5 consecutive days. An additional eight control patients were treated with sham-BiPAP. Maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), maximum voluntary ventilation (MVV), arterial blood gas values, Borg dyspnea score, dyspnea-associated functional impairment scales, and distance walked in 6 min were measured in subjects prior to and following the week-long trial. Nasal BiPAP produced a 66.3 ± 6 percent reduction in peak integrated diaphragmatic electromyographic (EMG) activity. There were no statistically significant changes in MIP, MEP, MVV, arterial pH, PaCO2, or PaO2 or in objective measures of functional impairment from dyspnea in either group after ventilator or sham treatment. However, nasal BiPAP reduced the Borg category score during resting, spontaneous breathing from 2.0 ± 0.4 to 0.7 ± 0.3 (p<0.01) after 5 days of treatment. In contrast, sham BiPAP-treated patients had no change in their dyspnea score, which was 1.8 ± 0.4 and 1.3 ± 0.4 before and after sham treatment, respectively. Nasal BiPAP also increased distance walked in 6 min from 780 ± 155 to 888 ± 151 ft (p<0.01) (23,400 ± 4,650 to 26,640 ± 4,530 cm) (p<0.01), whereas sham-BiPAP had no effect (768 ± 96 and 762 ± 106 ft [23,040 ± 2,880 and 22,860 ± 3,180 cm]) before and after sham treatment, respectively). In conclusion, these results indicate that nasal pressure-support ventilation, delivered via nasal BiPAP, improves exercise capacity and reduces dyspnea over the short term in selected outpatients with stable severe COPD. Whether such short-term improvement can be sustained merits further study.

Section snippets

Patient Selection

Seventeen outpatients with severe COPD were identified from the records of the pulmonary function laboratory at MetroHealth Medical Center. Severe COPD was defined as an FEV1 less than 50 percent of the predicted value or a ratio of FEV1 to forced vital capacity less than 55 percent of the predicted value. Patients were in stable condition at the time of study; all had had pulmonary function tests and arterial blood gas measurements performed within approximately the previous 12 months.

Demographics

The characteristics of the study group are shown in Table 1. There were six women and three men with a mean age of 62 years in the nasal BiPAP group, and five women and three men with a mean age of 68 years in the sham-BiPAP group. Mean FEV1 was 0.76 ± 0.08 L and 0.73 ± 0.06 L for the nasal BiPAP and sham-BiPAP treated groups, respectively.

Diaphragmatic EMG

The peak heights of the integrated EMG signals were averaged over five consecutive breaths before, and again, 1 min after initiation of BiPAP ventilation.

DISCUSSION

In this study, nasal pressure-support ventilation, delivered via the nasal BiPAP ventilatory system, administered for 2 h/d for 5 consecutive days, significantly reduced severity of dyspnea and improved distance walked in 6 min in outpatients with stable severe COPD.

CONCLUSIONS

In the present study, a sham control group was employed to reduce placebo effects. Functional impairment, exercise tolerance, and severity of dyspnea were assessed using several different objective scales designed for this purpose in an attempt to lessen inaccuracies associated with subjective reports by patients. In addition, the regimen of nasal BiPAP treatment used was well tolerated by our patients. Our results suggest that, at least in the short term, nasal pressure-support ventilation,

ACKNOWLEDGMENT

We thank Daniel Stofan, and Ylonne Watkins and Diane Delletro for expert technical and editorial assistance, respectively. No industry support was obtained for this study, except for loan of a nasal BiPAP, model S/T-D ventilatory support system (Respironics, Inc), the solicitation of which was initiated solely by the authors.

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    Manuscript received October 27, 1992; revision accepted August 30, 1993

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