An experience of performing spirometry by trained general practitioners

The article discusses the experience of teaching and conducting spirometry of general practitioners as part of the RESPECT study (RESearch on the PrEvalence and the diagnosis of COPD and its Tobacco-related aetiology). A total of 33 trained in spirometry general practitioners performed a study of 3119 patients. Quality criteria met 84.1% of spirometric studies. The analysis of the most common mistakes made by doctors during the forced expiratory maneuver is included. The most frequent errors were expiration exhalation of less than 6s (54%), non-maximal effort throughout the test and lack of reproducibility (11.3%). Independent predictors of poor spirogram quality were male gender, obstruction (FEV1 /FVC<0.7), and the center where the study was performed. The number of good-quality spirograms ranged from 96.1% (95% CI 83.2–110.4) to 59.8% (95% CI 49.6–71.4) depending on the center. Subsequently, an analysis of the reasons behind the poor quality of research in individual centers was conducted and the identified shortcomings were eliminated. The poor quality of the spirograms was associated either with the errors of the doctors who undertook the study or with the technical malfunctions of the spirometer.

Posterior cricoarytenoid activity and glottic size during hyperpnea in humans

We measured the electromyographic activity of the posterior cricoarytenoid (PCA) muscle simultaneously with glottic width (dg) in five normal human subjects during hyperpnea induced by hypoxia (7% CO2 in N2) or hypercapnia (9% CO2 in 50% O2). The glottic aperture was measured during inspiration at the time corresponding to peak inspiratory PCA activity and during expiration at the time corresponding to the minimum tonic activity. During hyperpnea, peak and tonic PCA activity increased simultaneously with widening of the vocal cords in both phases of the respiratory cycle. The PCA activity during both inspiration and expiration showed a single curvilinear relationship with dg of the form dg = A - Be-k.PCA (where A, B, and k are constants) in three of the five subjects. At 50% of maximum PCA activity, dg already reached 95% of its maximum value, which was less than that recorded during a voluntary forced expiratory maneuver. The single curvilinear relationship between PCA activity and dg could be due to the length-tension relationship of the PCA muscle and/or changes in its mechanical coupling, as well as simultaneous agonist and antagonist laryngeal muscle activity during progressive chemical stimulation. Also, further widening of the glottis during forced expiration suggests recruitment of additional muscles, e.g., the arytenoideus.

Effect of raised alveolar pressure on leukocyte retention in the human lung

To determine whether an increase in alveolar pressure delays the passage of leukocytes (WBCs) through the lung by compressing the lung capillaries, we measured the concentration of WBC across the lung in response to a forced expiratory maneuver. In 20 human subjects, blood was sampled from catheters placed in the pulmonary artery (PA) and left ventricle (LV) before, during, and after a forced expiratory maneuver held for greater than or equal to 20 s against an occluded airway. Pressures were recorded at the mouth and from both catheters. A significant fall in LV WBC (P less than 0.01) but not in PA WBC occurred during or immediately after the maneuver in 18 subjects, with a mean maximum decrease of 26 +/- 12% (SD) from base line (range 9-46%). Between 1 and 3 min after the maneuver, there was an increase in LV and PA WBC (P less than 0.01) above base line. The neutrophil and lymphocyte counts showed similar changes, but erythrocyte and platelet counts remained unchanged. The degree of fall in LV WBC correlated closely (r = 0.68, P less than 0.01) with the changes from lung zone 3 to zone 2 and 1 conditions, as determined from the pressure changes. We conclude that WBCs are retained in the lung during a forced expiratory maneuver because of alveolar capillary compression.

Failure of cholinergic blockade to prevent bronchodilatation following deep inspiration

The role of the cholinergic system in the phenomenon of bronchodilatation following a deep inspiration (BDFI) in humans has not been well established, although animal studies have suggested the cholinergic system to be of prime importance. We therefore induced cholinergic blockade with inhaled ipratropium bromide (Sch-1000) in five asymptomatic subjects and then assessed whether BDFI had been abolished. Since BDFI is only evident where there is normal or increased bronchomotor tone, prostaglandin F2 alpha (PGF2 alpha), a noncholinergic bronchoconstrictor, was used to re-establish bronchomotor tone in the presence of cholinergic blockade. At each stage the presence or absence of BDFI was assessed by comparing flows from a partial forced expiratory maneuver started at approximately 60% of vital capacity (Vmaxp) with flows from a forced expiratory maneuver started at lung capacity (Vmaxc). Flows were measured at the last 40% of vital capacity. The percent ratio of Vmaxp/Vmaxc was used as an indicator of BDFI. In the presence of cholinergic blockade and with reestablishment of bronchomotor tone with PGF2 alpha, BDFI could still be demonstrated (Vmaxp/Vmaxc percent ratio: control 110.3 +/- 10.6, after Sch-1000 129.4 +/- 10.3, after Sch-1000 and PGF2 alpha 59.4 +/- 6.9; P = 0.001). We conclude that there is not an essential role for the cholinergic system in the phenomenon of BDFI in healthy individuals.