Airway inflammation and best lung function in asthma
Panizza JA., James AL., Ryan G., Finucane KE.
Asthma can cause irreversible airflow obstruction (Brown et.al. Thorax 1984;39:131) which may be due to chronic inflammation of airway walls with resultant structural changes over time. A relationship between airway inflammation and ventilatory function and its decline with time has not been established. To examine the hypothesis that chronic inflammation of airways and progressive airflow obstruction are related we examined smears of sputum obtained from 20 chronic asthmatics while on their usual treatment. Smears were stained with haematoxylin and eosin and the percentages of eosinophils (E), neutrophils (N), lymphocytes (L) and macrophages (M) were calculated. The subjects were from a cohort of 44 asthmatics studied in 1980 and 1997. In both studies FEV1 was measured at enrolment and after 2 weeks each of usual treatment, high dose inhaled corticosteroids (ICS) and prednisolone 0.6mg/kg/day. Peak flows (PEF) were measured daily and symptoms, usual severity of asthma and treatment were assessed by questionnaire. Results: The best FEV1 with maximum treatment in the 20 subjects was 80±25 % predicted and decline in FEV1 was 40±15 mls/yr. Sputum cell counts (%) were: E = 14.5±19.9,N=34.3±25.0,L=0.8±0.8, M= 44.7±24.6;none were related to worst or best FEVi, change in FEVi with treatment, PEF variability, treatment scores, dose of ICS or to asthma severity or decline in FEVi from 1980-1997. Conclusion: In this group of asthmatics, airway eosinophils and neutrophils were increased compared with reported values for normal subjects (Pizichini et.al. AJRCCM 1996;154:308). The independence of inflammatory cell numbers and best FEV1 and its decline with time suggests that inflammation is determined by acute, variable factors and may not determine the structural changes which cause persistent airflow obstruction.