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Expiratory quantitative CT is not as accurate as inspiratory CT for quantifying pulmonary emphysema and probably reflects air trapping more than reduction in the alveolar wall surface.

To assess the pattern of abdominal muscle contraction in stable patients with chronic obstructive pulmonary disease (COPD), we studied electromyograms of the rectus abdominis, external oblique, and transversus abdominis muscles in 40 patients with variable degrees of chronic airflow obstruction (FEV1 between 17 and 82% of predicted); 12 control subjects with normal pulmonary function tests were studied for comparison. The subjects were studied during resting breathing in the supine posture, and the electromyograms were recorded with concentric needle electrodes implanted with the aid of a high-resolution ultrasound. The rectus abdominis and external oblique were silent in virtually all patients. In contrast, 17 patients had invariable phasic expiratory activity in the transversus abdominis, and 11 additional patients had intermittent transversus expiratory activity. Expiratory contraction of the transversus was related to the degree of airflow obstruction (p less than 0.005), and when present, it persisted in the seated posture. We conclude that (1) when breathing at rest, many stable patients with severe chronic airflow obstruction contract the abdominal muscles during expiration, and (2) this expiratory contraction is usually confined to the transversus muscle. These observations also indicate that the physiology of dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEP) in such patients should be reevaluated.

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Many patients with severe chronic obstructive pulmonary disease (COPD) contract the transversus abdominis (TA) muscle during expiration. The mechanical correlates of this contraction, however, are uncertain. In the present study, we have measured airflow, esophageal (Pes), and gastric (Pga) pressures, the anteroposterior (AP) diameter of the abdomen, and the electromyogram of the TA during resting breathing in 25 seated patients with severe COPD (FEV1 = 28 +/- 8% of predicted). Nine patients (Group I: FEV1 = 29 +/- 8% of predicted) in general had no TA activity during breathing, and 16 patients (Group II: FEV1 = 27 +/- 8% of predicted) had invariable phasic expiratory TA activity. In all patients of Group II, the decrease in abdomen AP diameter during expiration was associated with a gradual fall in Pga. In contrast, in 13 patients of Group II, the expiratory decrease in abdomen AP diameter was associated with a rise in Pga; this rise in Pga averaged 2.8 +/- 2.2 cm H2O. Furthermore, most patients had positive alveolar pressure at end-expiration, as shown by the time lag between the fall in Pes at the beginning of the inspiratory effort and the onset of inspiratory flow. However, whereas end-expiratory alveolar pressure averaged 2.4 +/- 2.2 cm H2O in Group II, it was only 0.8 +/- 0.6 cm H2O in Group I (p < 0.05). For the patient group as a whole, there was a close relationship between the rise in Pga during expiration and end-expiratory alveolar pressure (r = 0.87; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of age and posture on compliance of the rib cage (Crc) and diaphragm-abdomen (Cab) compartments of the chest wall was studied in 61 healthy adults (33 men, 28 women) aged 24-75 yr. Chest wall compliance (Cw) was measured by the weighted spirometer technique; Crc and Cab were derived from the slope of the relaxation line of the thoracoabdominal system obtained with two pairs of linearized magnetometers. While Cw was being measured, we monitored electrical activity of the abdominal external oblique muscle with a concentric needle electrode and thoracoabdominal configuration. In 52 subjects, the electromyogram did not show any abdominal muscle activity and the end-expiratory level never departed from the relaxed thoracoabdominal configuration, thus suggesting adequate respiratory muscle relaxation. Aging was associated with significant decreases in Crc and Cab. In the upright posture Crc decreased from 0.164 +/- 0.041 (mean +/- SD) l/cmH2O in the younger subjects (24-39 yr) to 0.114 +/- 0.027 l/cmH2O in the older subjects (55-75 yr). Cab concomitantly fell from 0.032 +/- 0.012 l/cmH2O to 0.020 +/- 0.007 l/cmH2O. These reductions were statistically significant (P less than 0.05-0.01) and were also present in the supine posture. Shifting from the seated to the supine posture did not cause any significant change in Cw but was invariably associated with a decrease in Crc and an increase in Cab.(ABSTRACT TRUNCATED AT 250 WORDS)

Asbestos bodies (AB) were counted by light microscopy in bronchoalveolar lavage (BAL) fluid obtained from 563 subjects. The presence of AB was found to reflect occupational exposure to asbestos and was rarely found in unexposed control subjects at concentrations above 1/ml of fluid (6.9% of white collar workers and 17.8% of blue collar workers). The overlap of results observed between subjects with definite exposure and those without underlines the difficulty in assessing exposure by questioning alone, which leads to underestimations or even overestimations of the risk. The highest counts (log mean, 120.5 AB/ml; range, 0 to 42,600) were found in patients with radiologic evidence of asbestosis, most likely reflecting the known association of this disease with retention of large amounts of long amphiboles, rather than in patients with pleural disease. A considerable overlap of results was also observed between groups with different diseases or without any apparent disease. Apart from uncertainties in the radiologic diagnosis, this may be explained by differences in latency since first exposure, in individual response to asbestos inhalation, or in pathogenic properties of different asbestos types. Because the presence of AB in BAL fluid appears to be a marker of exposure and not of disease, AB are more likely to be detected in patients presenting with asbestos-related diseases but in whom exposure is not confirmed by the occupational history (65 of 78 cases).

A meta-analysis of clinical trials of antihistamines was performed to assess the risk-benefit ratio of this therapeutic class in asthma. Double-blind randomized placebo-controlled trials assessing lung function changes under repeated use of antihistamine in adult asthma were selected, and the quality of studies was scored. Morning peak expiratory flow rate (PEFR) was the primary outcome: an effect size was computed for each study, with a 95% confidence interval (95% CI), and a mean effect size was computed, combining all studies. Effect sizes were also determined for secondary outcomes: evening PEFR, forced expiratory volume in one second (FEV1) and daily use of inhaled β-agonists.Nineteen studies were included in the meta-analysis. Mean quality score of studies was 59.4%; asthma was generally uncontrolled at study inclusion. Altogether, 582 antihistamine-treated and 557 placebo-treated asthma patients were evaluable. Antihistamines had little effect on airway calibre (mean increase in morning PEFR: 13 L·min -1 ; 95 CI: 8-18 L·min -1 ) and on use of inhaled β-agonists (mean reduction in daily use: 0.4 doses; 95% CI: 0-0.8 doses). Sedation occurred more often with antihistamines than with placebo (p<0.001); additional side-effects were mentioned, including weight gain, altered taste, headache and dry mouth.Respiratory and systemic effects observed after repeated use of antihistamines do not support the use of these medications in the treatment of asthma; better designed studies could affect this appraisal.