Chest
Volume 101, Issue 2, February 1992, Pages 385-391
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Clinical Investigations
Physiologic Evaluation of Pressure Support Ventilation by Nasal Mask in Patients with Stable COPD

https://doi.org/10.1378/chest.101.2.385Get rights and content

We evaluated the physiologic effects of pressure support ventilation by nasal route (NPSV) in eight patients with severe stable COPD and chronic hypercapnia who were randomly submitted to 2-h sessions of NPSV both with a portable ventilator (Respironics BIPAP device) and with a standard ventilator (Bird 6400ST device) at an inspiratory airway pressure of 22 cm H2O. Two sessions with each ventilator were performed using an FIo2 of 0.21 in each patient on two consecutive days. One patient did not tolerate either form of ventilation. Comparison of spontaneous with BIPAP ventilation showed a significant improvement in pH, PaCO2, and PaO2. Ventilatory pattern assessed by a respiratory inductive plethysmograph showed a significant increase in minute ventilation (VE), VT, and Ttot. Integrated surface diaphragmatic EMG activity measured only during BIPAP device ventilation decreased from that measured during spontaneous breathing. Similar changes in blood gases and ventilatory pattern were observed during ventilation by the Bird 6400ST except for VT/Ti ratio, which significantly increased. Comparison of baseline with measurements performed 12 h after the whole cycle of treatment showed a significant increase in pH and VE and a decrease in PaCO2. We conclude that short-term NPSV may be useful in improving respiratory pattern and blood gases in stable COPD patients with chronic hypercapnia.

Section snippets

Subjects

Studies were carried out on eight male patients (mean age, 64.6±11.6 [SD] years; weight, 64.0±8.5 kg; height, 162±9 cm), all of whom were smokers or exsmokers with chronic hypercapnia. The physiologic characteristics of the studied population are shown in Table 1. Patient 5 also suffered from a fibrothorax. During the study, the patients were in a stable condition, without exacerbations of respiratory symptoms or any relevant acute disease. All of the patients received long-term oxygen therapy,

RESULTS

One subject (No. 8) was unable to tolerate both ventilators. He suffered from a more severe degree of hyperinflation than the other patients (Table 1). This subject was not included for further analysis. The other seven patients tolerated NPSV with both ventilators without discomfort or complications and all tolerated a PIP of 22 cm H2O. The actual pressure delivered measured at the mask ranged from 17 to 20 cm H2O without any differences between the two ventilators.

Changes in ventilatory

DISCUSSION

The results of this study show that NPSV may be of clinical utility in COPD patients with chronic hypercapnia.

Noninvasive ventilatory support for patients with chronic respiratory failure has been widely used in patients with neuromuscular or chest wall disease1, 2, 3, 4, 5, 6 or with COPD.20, 21 Intermittent negative-pressure ventilation (INPV) with body ventilators has given conflicting results in COPD patients, the sustained improvements in ventilatory function observed by some authors being

ACKNOWLEDGMENTS

The authors wish to thank Antonio Braschi, M.D., for useful talks and Miss Jacqueline McKay for kindly reviewing the English of the manuscript.

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