Mechanisms of asthma and allergic inflammation
Short and long-term effects of cigarette smoking independently influence exhaled nitric oxide concentration in asthma

https://doi.org/10.1016/j.jaci.2005.03.025Get rights and content

Background

The fractional concentration of nitric oxide in exhaled breath (FeNO) is elevated in asthma. FeNO measurement has been proposed as a noninvasive index of disease activity. Cigarette smoking suppresses FeNO, which limits its use in smokers.

Objective

To identify and model short-term and long-term influences of cigarette smoking on FeNO.

Methods

The smoking history, FeNO, and fractional concentration of carbon monoxide in exhaled breath (FeCO) were measured in 53 subjects with asthma and 51 control subjects. A mathematical model of the short-term and long-term effects of cigarette smoking on FeNO was derived.

Results

Subjects with asthma had higher FeNO than controls (P < .001). Smokers had increased FeCO (P < .001). The short-term effect (hours since last cigarette) was associated with increased FeNO (P < .01) and decreased FeCO (P < .05). The long-term effect (years smoked) was associated with decreasing FeNO only in the subjects with asthma (r = −0.62; P = .005). These short-term and long-term effects were independent and were combined in a model predicting FeNO, predicted log10 FeNO = 1.23 − 0.58e−0.34t − 0.00000103 × (lifetime cigarettes), where t = hours since the last cigarette. This gave a convincing prediction of FeNO (r = 0.83; P < .0001).

Conclusion

Short-term and long-term effects of smoking influenced the measurement of FeNO. We defined a model that describes these effects. The use of this formula may improve the value of FeNO measurements in smokers with asthma.

Section snippets

Subjects

Fifty-three subjects with asthma (23 nonsmokers, 17 smokers, and 13 exsmokers) and 51 healthy subjects (20 nonsmokers, 20 smokers, and 11 exsmokers) were recruited from respiratory outpatient clinics and hospital staff, respectively. The diagnosis of asthma was based on the American Thoracic Society (ATS) criteria.11 Patients had not received oral corticosteroids in the past 4 weeks, and none had a history of a respiratory tract infection within the preceding 4 weeks. Current treatment included

Results

The number, sex, age, serum IgE level, atopic status, and FEV1 in the asthma and healthy control study groups, along with the inhaled corticosteroid use, asthma duration, and ATS asthma score of the asthma subjects, are listed in Table I according to smoking history. There were no significant age differences. The asthma group had significantly reduced lung function measured by the percent of predicted FEV1 (P < .001) and significantly higher IgE levels (P < .001) and atopy (χ2 = 23.6; P < .001)

Discussion

In this cross-sectional study, we have demonstrated coincidental short and long-term effects of cigarette smoking on the measurement of NO concentration in exhaled breath. These effects were independent and could be modeled mathematically.

We found that the FeNO was reduced in smokers with and without asthma compared with their nonsmoking counterparts, which is in agreement with other studies.4, 8, 9, 15, 16 We extended these observations by confirming a decrease in FeNO with increasing years

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    Ms. Fraser is supported by a research grant from the British National Flying Club.

    Disclosure of potential conflict of interest: All authors—none disclosed.

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