The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

THE CLINICAL EFFECT OF HELIUM-OXYGEN MIXTURES ON GAS EXCHANGE IN PATIENTS WITH OBSTRUCTIVE VENTILATORY DEFECTS

P. Harrison, RRT; D. Onorato, MD;. Pulmonary Division, Respiratory Care Department, Hartford Hospital, Hartford, Connecticut

INTRO: Helium is a biologically inert, insoluble gas whose Reynolds number, density and kinematic viscosity favor the production of laminar flow at all flow rates, thereby reducing resistance to airflow in the conducting airways. Mixtures of heliox have been demonstrated to reduce dead space, PIP, inspiratory and expiratory work of breathing and favorably alter ventilation perfusion relationships in animal models of obstructive lung disease. We reasoned that a substitution of helium-oxygen mixtures for nitrogen-oxygen in the treatment of obstructive lung disease would convert turbulent flow to laminar flow, thus reducing airway resistance and work of breathing, and enhancing parameters of gas exchange.



Methods: A retrospective chart review of all spontaneously breathing patients with a diagnosis of status asthmaticus, COPD exacerbation, chronic bronchitis or emphysema over a 24 month period treated with mixtures of helium-oxygen in a large tertiary teaching hospital. Parameters examined include pH, pO_2, respiratory A-a gradient and a/A ratio. Gas mixtures evaluated ranged from 60% to 80% helium and 21% to 40% oxygen. (See data below, mean ± SEM.)



Results: THE EFFECT OF HELIUM/OXYGEN MIXTURES ON GAS EXCHANGE AND RESPIRATORY RATE IN PATIENTS WITH STATUS ASTHMATICUS:

60%/40% (N=13)70%/30% (N=10)

(±SEM)

PREPOST%[Delta]PRE POST% [Delta]

pCO_247.20(2.14)39.20(1.56) 17 49.30(1.79) 39.70 (1.53) 19.5

pO_2 91.80(8.80) 109.20(7.17) 19 90.30(7.15) 93.30 (3.43)4.0

A-a 148.70 (22.80) 123.50 (10.00) 17 89.00 (11.50) 70.90 (3.51) 20.0

a/A0.43(0.05) 0.17(0.01) 60 0.53(0.03)0.25 (0.01) 52.0

RR37.80(1.02)27.40(1.09) 27 37.90(1.03) 27.20 (1.02) 28.0

THE EFFECT OF HELIUM/OXYGEN MIXTURES ON GAS EXCHANGE AND RESPIRATORY RATE IN PATIENTS WITH SEVERE COPD:

60%/40% (N=13) 70%/30% (N=10)

(±SEM)

PREPOST%[Delta] PRE POST[Delta]%

pCO_260.30(6.13)59.90(8.45)0.652.40(1.65) 44.20 (1.29) 15

pO_2114.30 (21.40)86.50(9.75) 24.0 129.10(3.21) 73.90 (4.73) 42

A-a 128.90 (29.50) 115.60 (13.07) 10.077.70 (23.60) 84.70 (4.21)9

a/A0.50(0.06) 0.35(0.09) 30.0 0.62(0.08)0.28 (0.01) 54

RR33.80(0.12)29.50(1.90) 12.035.40(2.39) 25.50 (1.42) 28

FINDINGS: In patients with status asthmaticus, heliox reduced pCO_2 17-19%, A-a gradient and a/A ratio 17-10 and 50-60% respectively. In asthmatics, heliox reduces respiratory rate, suggesting attenuated dyspnea. However, in patients with chronic bronchitis, emphysema or COPD, mixtures of 70% helium and 30% oxygen reduced pCO_2 by 15% and pO_2 by 42%, suggesting an accentuation of venous admixture. Mixtures of 60% helium and 40% oxygen had no effect on reducing pCO_2. In patients with COPD, heliox 70/30 reduced respiratory rate. These changes are consistent with the known physical properties of heliox and the aberration of physiology of small airway disease. These observations suggest that the use of heliox mixtures in status asthmaticus is safe and effective.

OF-95-064

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