A comparison of pulmonary function in male smokers and nonsmokers

Effects of time, albuterol, and budesonide on the shape of the flow-volume loop in children with asthma

BACKGROUND

Assessment of asthma through spirometric analysis in children is challenging because of often normal FEV(1) values.

OBJECTIVE

We used Mead's slope ratio (SR; (dV /dV)/(V /V)) to analyze the shape of the flow-volume loop.

METHODS

We analyzed the effects of time, albuterol, and budesonide on FEV(1), FEV(1)/forced vital capacity (FVC) ratio, forced expiratory flow from 25% to 75% of expired volume, and Mead's SR both early (between 75% and 50% of FVC, SR61) and late (between 75% and 50% of FVC, SR35) in exhalation in the Childhood Asthma Management Program cohort at baseline, 4 months, and the end of the study in participants who received either inhaled placebo or budesonide twice daily.

RESULTS

In the placebo group both SR61 and SR35 improved over time. Bronchodilator consistently improved both SR61 and SR35, without change in degree of improvement over time. Similarly, in the budesonide group time and bronchodilator each independently improved both SR61 and SR35. At 4 months and the end of the study, patients receiving budesonide had significant improvements in SR61 relative to patients receiving placebo, which was independent of bronchodilator effect. Budesonide and placebo were not different with respect to prebronchodilator or postbronchodilator SR35.

CONCLUSION

Budesonide-treated patients have less concave flow-volume loops when compared with placebo-treated patients. Time and bronchodilator also make the flow-volume loop less concave. Furthermore, it appears that there are discrete bronchodilator- and corticosteroid-responsive components of airflow obstruction in pediatric asthma.

The smoker's paradox and the real risk of smoking

No satisfactory explanations have been offered for the smoker's paradox, the greater short-term survival of smokers after a myocardial infarction nor for the large variations in the coronary risk rate for smoking ranging between 1 and 5.9. These discrepancies as well as the smoker's paradox may be caused by different baseline characteristics of smokers and nonsmokers, whereas the usually quoted coronary risk of 2 is derived from studies based on the assumption of equal baseline characteristics. As neither this assumption nor the possibility of unequal starting conditions have been tested, we examined the main cardiovascular risk factors in smoking and nonsmoking boys as near as possible to baseline, at the age of fourteen. This age appeared to be best suited, because boys starting to smoke early are most likely to become regular and heavy smokers. Of 336 boys, 39 had smoked 8.3+/-6.0 cigarettes/day for 15.5+/-11.2 months. Compared to nonsmokers, boys who started to smoke early had lower LDL cholesterol and alpha2-antiplasmin, greater handgrip strength, vital capacity and forced expiratory volume, better perfomance on bicycle ergometry and higher testosterone. The differences in total cholesterol, LDL cholesterol, vital capacity, handgrip strength, testosterone and alpha2-antiplasmin persisted after adjustment for age, body mass, and testosterone. In addition, the differences in perfomance on bicycle ergometry and forced expiratory volume persisted after adjustment for age. These favourable baseline characteristics of those starting to smoke early can explain the smoker's paradox. In addition, they suggest that the individual coronary risk in smokers is considerably higher than 2, because the assumption of equal baseline characteristics of smokers and nonsmokers cannot be upheld.

Influence of smoking habits on change in carbon monoxide transfer factor over 10 years in middle aged men

BACKGROUND

Emphysema is associated with a reduction in carbon monoxide transfer coefficient (TLCO/VA), but little is known about the evolution of changes in TLCO/VA in middle aged smokers at risk of developing chronic airflow obstruction.

METHODS

TLCO/VA (single breath method) was measured on two occasions 10 years apart in 122 middle aged men.

RESULTS

Initially TLCO/VA averaged 97% predicted in never smokers (n = 42, mean age 37.2 years), 99% predicted in ex-smokers (n = 21, mean age 41.9 years), and 85% predicted in those who smoked over 15 cigarettes a day (n = 42, mean age 42.0 years). Mean rates of decrease in TLCO/VA over 10 years, however, were similar in the three groups, so that differences between smokers and non-smokers did not increase during the 10 years. Seventeen men (mean age 40.9 years) who initially were smokers became sustained ex-smokers within two years of the first measurement; in these men mean absolute values of TLCO/VA rose, averaging 89% predicted at the first assessment but 102% predicted 10 years later.

CONCLUSION

By the age of about 40 years TLCO/VA was lower in smokers than in never smokers but this difference did not increase over the following 10 years. Sustained ex-smokers had values similar to those of never smokers even when TLCO/VA was known to have been reduced while they were smoking. Changes in TLCO/VA associated with stopping smoking were considerably larger than could be explained by carbon monoxide back pressure, indicating that mechanisms other than irreversible increase in the size of terminal air spaces underlie the lower values in smokers. To detect emphysema in smokers it is necessary to use reference equations that take account of current smoking.

Role of radio-aerosol and perfusion lung imaging in early detection of chronic obstructive lung disease

The efficacy of radio-aerosol and perfusion lung imaging in the early detection of chronic obstructive lung disease was evaluated in 38 subjects. The subjects included 5 non-smokers, 21 smokers with minimal or no respiratory symptoms and 12 patients with chronic obstructive lung disease. Each subject consented to a respiratory questionnaire, detailed physical examination, chest X-ray examinations, detailed pulmonary function tests and 99mTc-radio aerosol-inhalation lung imaging. Perfusion lung imaging with 99mTc-labelled macroaggregated albumin was performed in 22 subjects. A significant correlation (P less than 0.001) was observed between the degree of abnormalities on radio-aerosol imaging and pulmonary function tests (PFTs) including forced expiratory volume in 1 s, maximum mid-expiratory flow rate and mean transit time analysis. Abnormal radio-aerosol patterns and deranged PFTs were observed in 21 subjects each. Of 21 subjects with abnormal radioaerosol pattern 8 had normal PFTs. Of 21 subjects with abnormal PFTs 8 had normal aerosol images. Aerosol lung images and PFTs were abnormal more frequently than perfusion lung images. The results suggest that radio-aerosol lung imaging is as sensitive an indicator as PFTs for early detection of chronic obstructive lung disease and can be usefully combined with PFTs for early detection of alteration in pulmonary physiology in smokers.

Total effective time of the forced expirogram in disease: sources of error and a correction factor

Effective time of the forced expirogram is a sensitive index for the detection of mild airways obstruction. However, there is evidence that this measurement is not superior to maximum flow rates in the lower half of the forced vital capacity or even FEV1 and FEV1% in some patients suffering from obstructive lung disease. Furthermore we noticed that in some patients with a decrease of the forced vital capacity caused by exacerbation of airways obstruction, the effective time was not appreciably changed. We concluded that this apparent disadvantage of the effective time is the result of the different forced vital capacities. To eliminate this error we transformed the forced expirogram to the equivalent curve that the patient would produce, if his forced vital capacity was equal to the predicted mean value for his age, sex, and height. The derived corrected total effective time seems to have increased sensitivity for detection of small changes in expirograms obtained from the same subject or from different subjects.

Repeatability of the moments of the truncated forced expiratory spirogram

It is proposed that if the spirogram is truncated for moment analysis, this should be done with respect to volume and not time. Errors are incurred when the moments of one spirogram are compared with those of another. These errors are maximal with no truncation and are reduced by truncation. A method is described for deriving sequential truncated moments of the forced expiratory spirogram. The repeatability and discriminatory power of the truncated moments were assessed over five consecutive days in 21 symptom-free subjects and were compared with conventional spirometric tests. The first and second moments about the origin of the spirogram (alpha 1 and alpha 2), the moment ratio (square root alpha 2/alpha 1) and the forced expiratory time to truncation (FET) are progressively less repeatable within individuals the later the truncation point. The discriminatory power of alpha 1 and alpha 2 and FET declines with later truncation but the discriminatory power of the moment ratio is maximal with truncation at 85% forced vital capacity (FVC) an diminishes sharply if truncation is beyond 95% FVC. At 75% FVC truncation alpha 1 is as good as FEV1% in discriminating between our subjects, whereas alpha 1 at 100% FVC is only half as good as FEV1%. The moment ratio at 90% FVC truncation is highly reproducible (mean within person coefficient of variation 2.1%), has important discriminatory power and is little influenced by events early in the spirogram (correlation with FEV1% r = -0.61, p less than 0.001). The moment ratio at 90% of FVC has attributes which may be useful in detecting early airway obstruction and its further study is warranted in order to establish its normal range and predictive value.

Partial effective times of the forced expiratory spirogram in health and mild airways obstruction

The partial effective times of the expiratory spirogram were calculated in 80 normal non-smoking subjects aged from 20 to 69 years and in 30 patients aged from 30 to 58 years with chronic bronchitis. Of these patients, 28 had a normal FEV1/FVC ratio, while the other two had a low ratio. Partial effective times were calculated for 10% segments of the expired FVC from total lung capacity (0% FVC) to residual volume (100% FVC) and became progressively longer after 50% of the FVC had been expired in normal subjects. The elongation to the partial effective times was more pronounced with age. In the patients with simple chronic bronchitis (normal FEV1/FVC ratio) the partial effective times were longer than normal after 50% of the FVC had been expired and after 10% of the FVC had been expired in the two patients with chronic bronchitis and low FEV1/FVC ratio. The partial effective times of the forced expiratory spirogram, especially that at the 80--90% part of the FVC, seem to be very sensitive indices for the early detection of mild airways obstruction.