Impaired tracheobronchial clearance in patients with mild stable asthma.

Abstract

ABSTRACr Tracheobronchial mucociliary clearance was measured with the radioaerosol technique in 25 patients with stable, mild asthma, none of whom was taking systemic corticosteroids. The results were compared with those obtained from a control group of 25 healthy subjects matched for age and sex. All patients and healthy subjects were non-smokers. Ventilatory function was significantly impaired in the asthmatic group, which resulted in a more central initial tracheobronchial deposition of inhaled radioaerosol than in the control group. Despite the shorter transit path along the ciliated airways for the tracer radioaerosol in the asthmatic group, mucociliary clearance was found to be significantly poorer than in the healthy control group. This may be important with respect to bronchial mucus plugging.Asthma is a disease characterised by reversible airway obstruction' caused by mucosal oedema, bronchial smooth muscle contraction, and hypersecretion of mucus.2 Death from "ciliary insufficiency" and mucus plugging of small airways in asthmatics has been known for many years.3 When the asthma is mild but variable, however, the roles of the cilia and of mucus and its clearance are ill defined. Mucociliary function in asthmatics has been examined by only a few investigators,4-9 who have confined their measurements primarily to the proximal airways of the lungs. The numbers of patients studied are small and the results are conflicting. We have therefore assessed tracheobronchial mucociliary clearance in a moderately large group of patients with mild, stable asthma and compared it with that in a group of matched healthy subjects. MethodsThe objective non-invasive radioaerosol technique'0 was used to measure whole-lung mucociliary clearance. Polystyrene particles 5 ,um in diameter tagged with the radionuclide technetium-99m (99mTc) (T112 = 6 h) were generated by means of a spinning top" generator located within an airtight tank. The radioaerosol was inhaled from the tank by each subAddress for reprint requests: Dr SW Clarke, Department of Thoracic Medicine, Royal Free Hospital, London NW3 2QG. Accepted 10 December 1982 ject or patient via a mouthpiece (a nose clip being worn) in eight discrete breaths starting from functional residual capacity and limited to 450 ml in volume by a Krogh spirometer. Inspiratory flow was measured by a pneumotachograph interposed between the spirometer and the tank. Each inhalation was followed by a three-second breath-holding pause to enable particles to deposit in the lungs by sedimentation. At the end of the inhalation procedure a water mouthwash and drink were used to clear the oropharynx and oesophagus of deposited radioaerosol.

Inhaled frusemide does not affect lung mucociliary clearance in healthy and asthmatic subjects

“…In our study, we have also demonstrated reduced lung mucociliary clearance in mild asthmatics compared to normal subjects, as reported previously [9,10]. The reduction in asthmatics is an underestimate of the time effect, because the radioaerosol was deposited on average more proximally within the lungs of asthmatics compared to normal volunteers.…”

“…Lung mucociliary clearance may be affected by a number of physiological, pharmacological, environmental and pathological factors [8]. In patients with mild stable asthma and those who are in clinical remission, lung mucociliary clearance is depressed, and the mechanisms by which this occurs are unclear [9,10].…”

Epithelial tethering of MUC5AC-rich mucus impairs mucociliary transport in asthma

“…Tracheobron chial mucociliary clearance is impaired in stable asthma (2) and worsens during acute exacerbations (3). The principal cause of death from asthma is asphyxiation from intraluminal airway obstruction by widespread mucus plugs (4)(5)(6).…”

Effect of TH2 cytokines and interferon gamma on beat frequency of human respiratory cilia

“…Clinical asthma manifestations include recurrent episodes of at least partially reversible wheezing, dyspnoea, cough, and increased airway mucus production. The asthmatic airway is characterized by epithelial damage, mucus hypersecretion, submucosal glandular hypertrophy, and goblet cell hyperplasia finally impairing mucociliary clearance (3)(4)(5)(6)(7). While efficient mucociliary clearance plays a fundamental role in the innate immune response system of the conducting airways, the impaired mucociliary clearance in asthma leads to prolonged exposure of inhaled pollutants and aeroallergens to the respiratory epithelium and an increased susceptibility to infections (4).…”