Chest
Volume 87, Issue 6, June 1985, Pages 790-795
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Clinical Investigations
Helium-Oxygen Breathing in Severe Chronic Obstructive Pulmonary Disease

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The effect of breathing helium-oxygen (He-O2) mixtures was evaluated in 15 patients with severe chronic obstructive pulmonary disease (COPD). Gas exchange was assessed during quiet breathing at rest before and after 15 minutes of breathing 80 percent He-20 percent O, mixtures in all patients. Functional residual capacity (FRC) determined during argon (Ar) washing studies fell significantly while breathing He-O2, but we did not find significant changes in minute ventilation, tidal volume, respiratory frequency, or inspiratory or expiratory timing. Eleven patients showed decreases in arterial Pco2 and CO2 excretion during resting breathing on He-O2. Expiratory flows were increased at a given lung volume during He-O2 breathing as expected. Apparently, mechanical work of breathing was decreased in patients with severe COPD while breathing He-O2, leading to a reduction in PaCo2 and improvement in overall alveolar ventilation. These findings lend support to the therapeutic use of He-O2 under some conditions in patients with severe COPD.

Section snippets

Subjects

Fifteen stable adult male patients ranging in age from 52 to 73 years (mean 61 years) with the diagnosis of severe COPD were studied. Informed written consent was obtained from all patients. All patients had either a forced expiratory volume in one second (FEV1) less than or equal to 1 L; or the ratio of forced expiratory volume in one second to forced vital capacity (FEV1/FVC %) less than or equal to 50 percent. Nine subjects were outpatients followed up in our pulmonary clinic. Six were

Results

Our subjects had FEV1 values that ranged from 0.55 to 1.30 L (mean ± SEM: 0.87± 0.07 L); the percentage of predicted FEV1 ranged from 17 to 51 percent (mean ± SEM: 30±3 percent) and FEV1/FVC% ranged from 16 to 47 percent (mean ± SEM: 35 ± 2 percent). Ten of the 15 patients had a 20 percent or greater improvement in the FEV1 after inhalation of an isoetharine HC1 aerosol. Baseline arterial blood gas measurements obtained at an FIo2 ranging from 0.21 to 0.27 (depending on the individual needs of

Discussion

Our finding of a decreased FRC while breathing He-CO2 is consistent with the anticipated effects of breathing a less dense gas in severe COPD.

In patients who are substantially hyperinflated, it is possible that expiratory pleural pressures can be sufficiently positive during resting breathing to result in expiratory flow limitation, while at the same time the patients may be maintaining elevated resting lung volumes by continuing to use inspiratory muscles during expiration. This circumstance

Acknowledgments

Mrs. Lida-Claire Gamon and Mr. Charles M. Goldman provided skillful technical assistance.

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Supported in part by NIH grants HL-25233, HL-25830, and the Medical Research Service of the Veterans Administration.

Manuscript received August 27; revision accepted November 26.

Reprint requests: Dr. Swidwa, VA Medical Center, Brecksville, Ohio 44141

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