What is the best way to measure lung function?

Risk factors for small airway obstruction among Chinese island residents: a case-control study

BACKGROUND

We investigated the prevalence of and risk factors for small airway obstruction (SAO) among Chinese island residents to establish means to prevent and treat SAO.

METHODS

From October 17, 2011 to November 1, 2011, a total of 2,873 residents aged >20 years who lived on the Huangqi Peninsula of Fujian were recruited by random cluster sampling. They were asked to complete a Burden of Obstructive Lung Disease (BOLD) questionnaire and underwent physical examinations and lung function evaluations. SAO was defined as a forced expiratory flow at 50% of vital capacity, Vmax50%, of less than 70% of predicted. Risk factors for SAO were assessed from among demographic and anthropometric variables, blood chemistry results, and questionnaire response items.

RESULTS

A total of 216 (7.52%) Chinese island residents were identified as having SAO (95 males; 121 females). Their survey and test results were compared with 432 age and sex-matched healthy controls (192 males; 240 females) for SAO risk factors. Among numerous factors investigated, only diabetes mellitus (p = 0.039), smoking index (SI, p<0.001 for SI>600), second hand smoke (p = 0.002), and lack of regular exercise (p<0.001) were significant risk factors for SAO.

CONCLUSIONS

The risk factors for SAO among Chinese island residents appeared to be similar to those among people who live in high-density urban environments and impoverished rural areas. Public health policies and medical practices directed toward improving respiratory health for island residents should be comparable to those used for urban and rural dwellers.

The role of the FEF50%/0.5FVC ratio in the diagnosis of obstructive lung diseases

OBJECTIVE

To evaluate the contribution of a new coefficient, the FEF50%/0.5FVC ratio, obtained from the maximal expiratory flow-volume curve, to the diagnosis of obstructive lung disease (OLD); to test this coefficient in differentiating among patients considered normal, those with OLD and those with restrictive lung disease (RLD); and to determine cut-off points for each functional diagnosis, as well as the probability for each diagnosis based on individual values.

METHODS

A prospective, cross-sectional study analyzing the pulmonary function of patients referred to the Porto Alegre Hospital de Clínicas, in Porto Alegre, Brazil, between January and December of 2003. We collected demographic and spirometric data. The patients were divided into three groups: normal; OLD; and RLD. We calculated the FEV1/FVC and FEF50%/0.5FVC ratios, and we compared the mean FEF50%/0.5FVC values among the groups. We used Pearson's correlation test in order to compare FEF50%/0.5FVC with FEV1/FVC. The patients were again divided into two groups: those with OLD and those without OLD. We calculated the likelihood ratio for different cut-off points.

RESULTS

The mean age of the patients was 55.8 +/- 14.7 years. There were significant differences among the groups in terms of the mean FEF50%/0.5FVC (2.10 +/- 0.82, 2.55 +/- 1.47 and 0.56 +/- 0.29, respectively, for normal, RLD and OLD; p < 0.001). There was a positive correlation between FEF50%/0.5FVC and FEV1/FVC in the OLD group (r = 0.83). We found that an FEF50%/0.5FVC < 0.79 strongly suggests OLD, whereas an FEF50%/0.5FVC > 1.33 practically excludes this diagnosis.

CONCLUSIONS

The FEF50%/0.5FVC ratio is a potentially useful parameter in the differential diagnosis of OLD and correlates positively with the FEV1/FVC ratio.