Background-Low attenuation areas (LAA) on computed tomographic (CT) scans have been shown to represent emphysematous changes in patients with chronic obstructive pulmonary disease (COPD). However, the significance of LAA is still controversial in patients with asthma. This study was undertaken to assess the usefulness of lung CT densitometry in the detection of airspace enlargement in association with asthma severity. Methods-Forty five asthmatic subjects and 15 non-smoking controls were studied to determine the influence of age, pulmonary function, and asthma severity on mean lung density ( Conclusions-Decreased CT lung density in non-smoking asthmatics is related to airflow limitation, hyperinflation and aging, but not with lung transfer factor. (Thorax 2001;56:851-856) Keywords: high resolution computed tomography; asthma severity; lung function; age Asthma is a disease characterised by airflow limitation that reverses spontaneously or in response to treatment.1 The nature of asthma as a chronic inflammatory disease of the airways is well recognised.2 This inflammation process leads to irreversible changes in the airway.3-5 Frequent airway and lung parenchymal changes associated with asthma are considered to be responsible for the irreversibility of airway obstruction, an outcome that is observed in many severe asthmatics. Emphysema, on the other hand, is defined pathologically as a process that results in the increase of distal airspaces with destruction of their walls without obvious fibrosis. 6 The evidence for the presence of emphysema in asthmatic patients is controversial.Numerous studies have demonstrated the usefulness of computed tomographic (CT) scanning and high resolution CT (HRCT) scanning to detect and quantify pulmonary emphysema in patients with chronic obstructive pulmonary disease (COPD), [7][8][9][10][11][12][13][14][15][16][17][18][19] and a quantitative method using digital data as well as visual assessment of the scan are used to analyse the CT images. Low attenuation areas (LAA) on CT scans in vivo have been shown to represent macroscopic and/or microscopic emphysematous changes in the lungs of patients with COPD.7-12 However, one report has suggested that mean lung density (MLD) gives a good indication of hyperinflation rather than of emphysema. 20Some studies have investigated the use of CT lung densitometry in non-smoking asthmatic patients. [21][22][23][24] One study suggested that the percentage of pixels below -900 Hounsfield Units (HU) at full expiration reflects air trapping in asthmatic patients and correlates with pulmonary function. 21 Gevenois et al showed that acute expiratory airflow limitation and chronic hyperinflation did not influence the MLD or the relative area of the lungs showing attenuation values less than -950 HU (RA 950 ) in nonsmoking asthmatic patients. 22 They also found that CT lung densitometry was influenced by the total lung capacity (TLC) and age in healthy subjects. Biernacki et al observed that some patients with chronic stable asthma devel...

Recently, it was shown that both mean lung density (MLD) and the relative lung area with an attenuation of v-950 HU (RA950) are related to severity of asthma in nonsmoking asthmatics. The aim of the present study was to examine whether reduced computed tomography (CT) lung density during exacerbation could change after treatment.A cross-sectional study was performed to compare CT lung density in 30 stable asthmatics, 30 unstable asthmatics and 25 control subjects. In order to investigate longitudinally the effect of treatment on decreased CT lung density, 17 asthmatics with an exacerbation were followed at the initiation of treatment and 2 months after relief.The MLD was significantly lower and the RA950 significantly higher in unstable asthmatics than in controls and stable asthmatics. Both MLD and RA950 changed significantly with administration of systemic glucocorticoid therapy. The changes in forced expiratory volume in one second correlated significantly with those in both MLD and RA950. The changes in residual volume also correlated significantly with those in both MLD and RA950.It was concluded that decreased computed tomographic lung density during an asthma exacerbation is at least partially reversible, and changes in mean lung density and the relative lung area with a radiation attenuation of v-950 HU are related to the change in forced expiratory volume in one second and residual volume.

Low attenuation areas in computed tomography images from patients with chronic obstructive pulmonary disease have been reported to represent macroscopic and/or microscopic emphysema. The cumulative size distribution of the clusters has been shown to follow a power law characterized by the exponent D, a measure of the complexity of the terminal airspace geometry. We have previously found increased low attenuation areas in nonsmoking subjects with asthma. We examined the size distribution of the clusters in nonsmoking subjects with asthma compared with both nonsmoking control subjects and subjects with asthma with a smoking history. The percentage of lung field occupied by low attenuation areas (LAA%) and D in subjects with asthma with a smoking history differed significantly from nonsmoking subjects with asthma and control subjects. In nonsmoking subjects with asthma, both parameters differed significantly between severe asthma and mild or moderate asthma. The LAA% differed significantly between moderate and mild asthma, but D did not. In mild and moderate asthma, a highly significant correlation between LAA% and D was observed in patients with a smoking history, but not in nonsmoking subjects with asthma. Our results suggest that decreased D is mostly related to emphysematous change, and both measurements of LAA% and D may provide useful information to characterize low attenuation areas in subjects with asthma.

PurposeControlled clinical trials evaluating the efficacy of repeated Waon therapy for patients with chronic obstructive pulmonary disease (COPD) have yet to be conducted. The purpose of the present study was to evaluate whether repeated Waon therapy exhibits an adjuvant effect on conventional therapy for COPD patients.Patients and methodsThis prospective trial comprised 20 consecutive COPD patients who satisfied the criteria of the Global initiative for chronic Obstructive Lung Disease (GOLD) guidelines, stages 1–4. They were assigned to either a Waon or control group. The patients in the Waon group received both repeated Waon therapy and conventional therapy, including medications, such as long-acting inhaled β2 agonists, long-acting anticholinergics and xanthine derivatives, and pulmonary rehabilitation. The Waon therapy consisted of sitting in a 60°C sauna room for 15 minutes, followed by 30 minutes of being warmed with blankets once a day, 5 days a week, for a total of 20 times. The patients in the control group received only conventional therapy. Pulmonary function and the 6-minute walk test were assessed before and at 4 weeks after the program.ResultsThe change in vital capacity (0.30 ± 0.4 L) and in peak expiratory flow (0.48 ± 0.79 L/s) in the Waon group was larger than the change in the vital capacity (0.02 ± 0.21 L) (P=0.077) and peak expiratory flow (−0.11 ± 0.72 L/s) (P=0.095) in the control group. The change in forced expiratory flow after 50% of expired forced vital capacity in the Waon group, 0.08 (0.01–0.212 L/s), was larger than that in the control group, −0.01 (−0.075–0.04 L/s) (P=0.019). Significant differences were not observed in the change in any parameters in the 6-minute walk test. Data are presented as means ± standard deviation or median (25th–75th percentile).ConclusionThe addition of repeated Waon therapy to conventional therapy for COPD patients can possibly improve airway obstruction.

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