Chest
Volume 118, Issue 5, November 2000, Pages 1315-1321
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Clinical Investigations
Asthma
Effects of Weight Loss on Peak Flow Variability, Airways Obstruction, and Lung Volumes in Obese Patients With Asthma

https://doi.org/10.1378/chest.118.5.1315Get rights and content

Study objectives

To clarify the pathophysiologicfeatures of the relation between asthma and obesity, we measured theeffects of weight reduction on peak expiratory flow (PEF) variabilityand airways obstruction, compared to simultaneous changes in lungvolumes and ventilatory mechanics in obese patients with stableasthma.

Methods

Fourteen obese asthma patients (11women and 3 men; aged 25 to 62 years) were studied before and after avery-low-calorie-diet period of 8 weeks. PEF variability was determinedas diurnal and day-to-day variations. FEV1 and maximalexpiratory flow values were measured with a flow-volume spirometer.Lung volumes, airways resistance (Raw), and specific airwaysconductance were measured using a constant-volume body plethysmograph.Minute ventilation was monitored in patients in supine and standingpositions.

Results

As patients decreased their bodymass index (SD) from 37.2 (3.7) to 32.1(4.2) kg/m2(p < 0.001), diurnal PEF variation declined from 5.5% (2.4) to4.5% (1.5) (p = 0.01), and day-to-day variation declined from 5.3%(2.6) to 3.1% (1.3) (p < 0.005). The mean morning PEF,FEV1, and FVC increased after weight loss (p = 0.001,p < 0.005, and p < 0.05, respectively). Flow rate at the middlepart of FVC (FEF25–75) increased even when related to lungvolumes (FEF25–75/FVC; p < 0.05). Functional residualcapacity and expiratory reserve volume were significantly higher afterweight loss (p < 0.05 and p < 0.005, respectively). A significantreduction in Raw was found (p < 0.01). Resting minute ventilationdecreased after weight loss (p = 0.01).

Conclusion

Weight loss reduces airways obstruction as well as PEF variability inobese patients with asthma. The results suggest that obese patientsbenefit from weight loss by improved pulmonary mechanics and a bettercontrol of airways obstruction.

Section snippets

Materials and Methods

Fourteen patients (11 women and 3 men; aged 25 to 62 years) witha clinical diagnosis of asthma and moderate to morbid obesity BMI(range, 32.5 to 42.5 kg/m2) were recruited forthe study. Characteristics of the patients and antiasthmaticmedications are presented in Table 1. Prior to our study, all patients participated as a control group inanother study.10 Their spirometric and serial PEF valueswere carefully followed up every 2 months for 1 year before starting inour study. Because they were

Results

The effects of weight reduction on BMI and symptom scores as wellas use of rescue medication are shown in Table 2. The mean weight loss was 13.7 kg (range, 8 to 18 kg). The mean BMIdecreased by 5.1 kg/m2 (range, 3.0 to 7.4kg/m2). Symptoms were recorded on a VAS scalefrom 0 to 100 mm. A significant reduction in dyspnea was demonstrated;the change in cough score was not statistically significant (NS). Theuse of rescue sympathomimetics was < 1 dose per day at baseline, andit did not change by the

Discussion

The results of our study indicate improved pulmonary functionafter weight reduction in obese patients with asthma, suggesting thatthese patients benefit from even modest weight loss. The increase inFEV1 with no change inFEV1/FVC ratio may rather reflect improvement inlung volumes, a well-known effect of weight loss inobesity,121617 than decrease in airways obstruction.However, increased FEF25–75 even when related tovolume (FEF25–75/FVC) may suggest a relief inperipheral airways obstruction.

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    This study was supported by the Finnish Cultural Foundation.

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