Previous studies have suggested that mucociliary clearance (MC) is impaired in asthmatic subjects. If so, impaired clearance may be an important factor in acute exacerbation. We proposed that if MC plays a significant role in acute illness, MC should be impaired during the exacerbation but improve after recovery. To test this hypothesis, five asthmatic patients with attacks requiring hospitalization underwent measurement of MC using radiolabeled aerosol and a gamma camera. They were studied on the second or third day after admission with repeat measurements after discharge. Spirometry was performed before all studies. After an equilibrium xenon scan (133Xe), which defined lung borders and measured regional volume, radiolabeled saline particles containing technetium-labeled (99mTC) sulfur colloid were deposited and used to label airway mucus. Deposition patterns were matched by regulating particle distribution and breathing pattern. MC was then measured as percentage retention of radioactivity at 10-min intervals for 2 h. When hospitalized, 96.0 +/- 2.06% (SEM) of the initial radioactivity was retained in the lung after 2 h, indicating little clearance of mucus from the lung. In fact, no significant changes were detected when activity at 120 min was compared with measurements at 10 min (99.2 +/- 0.22%, NS). After discharge clearance was markedly enhanced. That is, retention of lung activity was significantly lower at all time intervals from 10 min onward, with only 70.9 +/- 3.86% retained at 120 min (p = 0.008). During an asthmatic attack warranting hospital admission, MC is significantly impaired, with marked improvement following recovery.(ABSTRACT TRUNCATED AT 250 WORDS)
We studied deposition of radioactive monodisperse 1.5-micron aerosol in humans following inhalation during quiet breathing. Two groups were studied: normal, defined by tidal loops below the maximum expiratory flow-volume (MEFV) envelope [forced expiratory volume at 1 s at percent of forced vital capacity (FEV1%) 62-78]; and flow-limited, with tidal loops superimposed on MEFV relationship (FEV1% 21-57) and flow-limiting segments (FLS) known to exist in central airways. During simultaneous imaging with a gamma camera, fraction of inhaled aerosol deposited in the lung (DF) was determined by right-angle light scattering. With regions of interest defined by an equilibrium image of 133Xe, regional deposition was normalized for area and lung thickness and expressed as a central-to-peripheral (C/P) ratio. Deposition was uniform throughout the lung in normal subjects [C/P 1.02 +/- 0.07 (SD), n = 6]. In flow-limited group, central deposition predominated (C/P 1.98 +/- 0.64, n = 6, P less than 0.05). Tidal volume and inspiratory flow, forces thought to influence deposition during inspiration, were not different between groups. Spontaneous cough occurred in five flow-limited subjects during aerosol inhalation, with further increase in central deposition when compared with quiet breathing (C/P 1.85 +/- 0.60 to 2.69 +/- 0.600, P less than 0.01). During cough, tidal volume (ml) was reduced significantly (576 +/- 151 to 364 +/- 117, P less than 0.01) with no change in inspiratory flow (l/s) (1.37 +/- 0.23 to 1.38 +/- 0.40, P = NS). DF, however, was unaffected by cough (0.34 +/- 0.13 to 0.61 +/- 0.12, P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.