Chest
Volume 105, Issue 1, January 1994, Pages 87-94
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Clinical Investigations: COPD
Four-week Negative Pressure Ventilation Improves Respiratory Function in Severe Hypercapnic COPD Patients

https://doi.org/10.1378/chest.105.1.87Get rights and content

Studies on respiratoiy muscle resting by negative pressure ventilation (NPV) in patients with stable COPD bave given conflicting results. Probable explanations lie in criteria of patients’ selection, method of NPV application, and lack of supervision of respiratoiy muscle rest Thirteen hypercapnic patients with COPD were, therefore, randomly assigned to either a NPV group or a control group. The NPV was applied by an airtight jacket (pneumosuit), 5 h a day, 5 consecutive days a week for 4 weeks. Both NPV group and control group performed in-hospital pulmonary rehabilitation program for a 4-week period. Arterial blood gases, spirometry, maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP), breathing pattern, and electromyogram (EMC) of the diaphragm and parasternal intercostal muscles were measured on the preintervention day, and at the end of the second and fourth weeks of treatment (days 13 and 27, respectively). The short-term effect of NPV on EMC suppression was also checked throughout the ventilatolry sessions in three different days (1, 12, and 26, respectively). A 6-min walking test (WT) and level of dyspnea by a modified Borg scale were evaluated on the preintervention and tibe last days. Negative pressure ventilation resulted in a significant reduction in EMG activity of both diaphragm and parasternal muscles, associated with significant increase in MIP, tidal volume, and ventilation, and increase in PaO2 and decrease in PaCO2. A significant relationship between change in MIP and change in PaCO2 was observed (r = 0.72, p < 0.01). Improvement in 6-min WT and dyspnea sensation was also observed, both being the sole changes in the control group. These data seem to indicate a beneficial role of respiratory muscle rest in improving respiratory function. Adequate supervision by personnel familiar with the equipment is likely to contribute to successful treatment.

Section snippets

Patients

The study was performed on 13 patients (mean ± SD age, 63.7 ± 5.7 years) with chronic obstructive pulmonary disease (COPD), according to the American Thoracic Society criteria.11 All patients were hypercapnic (mean ± SD PaCO2 = 60.6 ± 5.9 mm Hg) and had severe airflow obstruction. They were all free of active cardiovascular diseases. At the time of the study, all patients were in a clinically stable state. Informed consent was obtained from each subject.

Functional Evaluation

Routine spirometry obtained with subjects

Results

Functional data for the two groups of patients are summarized in Table 1. Both NPV and control groups exhibited severe airflow obstruction (FEV1/VC), hyperinflation (FRC), a marked reduction in MIP, and a moderate decrease in MEP, as compared with our laboratory reference values; all patients were hypercapnic (62.2 ± 6 mm Hg and 59.8 ± 4.5 mm Hg, for NPV and control groups, respectively) and hypoxemic (51.5 ± 5.5 mm Hg and 53.5 ± 7.1 mm H?, for NPV and control groups, respectively). No

Discussion

In this study, we provide evidence that in patients with stable COPD with chronic hypercapnia, NPV is able to produce amelioration in respiratory muscle strength, breathing pattern, arterial blood gases, along with a consistent suppression in EMG activity of the diaphragm and the parasternal intercostal muscles. These results are consistent with some reports,1, 5, 9, 22, 23 but at variance with others.6, 7, 8,10,24,25

Differences between our and other studies showing no benefit from NVP6, 7, 8,10

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    This research was supported by grants from the Ministero della Pubblica Istruzione of Italy.

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