The Use of a Helium-Oxygen Mixture during Maximum Expiratory Flow to Demonstrate Obstruction in Small Airways in Smokers

Abstract

A B S T R A C T We measured the response to breathing a mixture of 80% helium and 20% oxygen (He) during a maximum expiratory flow-volume (MEFV) maneuver in 66 nonsmokers and 48 smokers, aged 17-67. All of the subjects studied had (forced expiratory volume in 1 s/forced vital capacity [FEV,.o/FVC]) X 100 of greater than 70%. While the flow rates of the smokers were within ±2 SD of those of the nonsmokers at 50% VC (Vmaxwo), both groups showed a reduction in flow with age (nonsmokers: r = -0.34, P < 0.01; smokers r = -0.52, P < 0.001). Nonsmokers showed no significant reduction with age in response to breathing He, while smokers showed a marked reduction with age (r = -0.63, P < 0.001 at Vmaxw). We also measured the lung volume at which maximum expiratory flow (Vmax) while the subject was breathing He became equal to Vmax while he was breathing air, and expressed it as a percent of the VC. This was the most sensitive method of separating smokers from nonsmokers. These results indicate that the use of He during an MEFV maneuver affords sufficient sensitivity to enable detection of functional abnormalities in smokers at a stage when Vmax while they are breathing air is normal.

How does HeO2 increase maximum expiratory flow in human lungs?

“…Becauise a helium-oxygen (HeO2) gas mixtuire has a lower gas density than air, the normal response to Dr Received for publication 18 July 1979 and int revised form 29 April 1980. 720 breathing this mixtture is an increase in maximum expiratory flow (Vmax) (1,2). The magnittude of this increase (AVmax) is often less in persons with obstructive airway disease and the decrease in response is presumed to be dependent upon the site of air-flow obstruction.…”

Spirometric standards for non-smokers and smokers of India(eastern region).

“…Thus, narrowing and resultant increase in resistance in the small airways and/or a decrease in elastic recoil pressure of the lung can cause decreased flows at these lung volumes. According to DOSMAN et al (1975), early changes in smokers are probably due to narrowing of the small airways. The present observations are in accordance with this view which also coincide with WALTER et al (1979).…”

Assessment of changes in airway calibre I. Tests of forced expiration.

“…More information can be obtained by comparing MEFV curves with the subject breathing air and a helium-oxygen mixture (Despas, Leroux & Macklem, 1972;Hutcheon, Griffin, Levison & Zamel, 1974;Dosman, Bode, Urbanetti, Martin & Macklem, 1975; (Figure 7). Theoretically the effects of the reduced density of a helium-oxygen increase in maximum expiratory flow, but with all other flow regimes maximum expiratory flow will increase.…”

“…The technique has been fairly widely applied to asthmatic subjects, some of whom retain helium-responsiveness while others do not (Despas et al, 1972;Benater, Clark & Cochrane, 1975). It has also been used to detect abnormalities in smokers with normal MEFV curves breathing air (Dosman et al, 1975) (Rosenblatt & Stein, 1962;Lal et al, 1964) which in subjects with airway disease is one of the least repeatable aspects of the spirogram.…”