Chest
Volume 123, Issue 4, April 2003, Pages 1038-1046
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Clinical Investigations
COPD
Acute Effects of Hyperoxia on Dyspnea in Hypoxemia Patients With Chronic Airway Obstruction at Rest

https://doi.org/10.1378/chest.123.4.1038Get rights and content

Study objectives:

Supplemental oxygen is used in hypoxemic patients with chronic airways obstruction (CAO) because it reduces pulmonary artery pressure and prolongs life. The purpose of this study was to assess at rest the effects of 30% oxygen inhalation on dyspnea, breathing pattern, neuromuscular inspiratory drive based on measurement of mouth occlusion pressure (P0.1), and dynamic hyperinflation (DH), as reflected by changes in inspiratory capacity (IC).

Methods:

Ten patients with stable CAO receiving long-term oxygen were studied at rest, before and after 5, 15, and 25 min of oxygen administration. Severity of dyspnea was rated using the visual analog scale (VAS). Breathing pattern parameters, P0.1, IC, and tidal expiratory flow limitation (EFL), were measured sequentially.

Results:

Eight patients exhibited EFL under baseline condition. During 30% oxygen breathing, the VAS score significantly decreased, associated with a concurrent increase of IC (11%). There was also a significant reduction of minute ventilation and tidal volume (11% and 12%, respectively), which was due to a significant decrease of mean inspiratory flow. Although not significantly, P0.1 decreased by 13%. Finally, two patients reverted from EFL to no EFL.

Conclusion:

Patients with CAO receiving long-term oxygen may benefit from hyperoxic breathing at rest, since it decreases the ventilation and the degree of DH, with concurrent improvement of dyspnea sensation.

Section snippets

Patients

The study was performed on 10 male patients with severe CAO receiving long-term oxygen. Nine patients had COPD, and one patient had bronchiectasis (Table 1). Diagnosis was made according to American Thoracic Society (ATS) guidelines.13 One patient with COPD (patient 7) had chronic pleural effusion. The patients were clinically and functionally stable at the time of the study, ie, absence of exacerbation and significant changes in spirometry during the preceding 4 weeks. No patients received

Results

All patients had severe obstructive pulmonary disease characterized by FEV1 < 42% predicted and FEV1/FVC < 54% (Table 1). In patient 5, who had bronchiectasis, the TLC was below the normal limits, a common feature in this disease, though the increased body weight (body mass index of 31) probably also contributed to his restrictive pattern. Only one patient (patient 10) was a responder to bronchodilation (ΔFEV1 = 21% of control) according to ATS but not European Respiratory Society criteria.

Discussion

The results of this study indicate that in patients with CAO receiving long-term domiciliary oxygen for severe hypoxemia, hyperoxic breathing at rest induces a significant reduction of ventilation and DH with concurrent improvement of dyspnea sensation.

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    This work was performed at Service de Réanimation Médicale et Assistance Respiratoire, Hôpital de la Croix-Rousse, Lyon, France.

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