Increased peak expiratory flow variation in asthma: severe persistent increase but not nocturnal worsening of airway inflammation.

Asthma at night is characterized by a nocturnal increase in airway obstruction. It has been hypothesized that nocturnal asthma results from an increase in airway wall inflammation at night. However, studies on inflammatory cells in bronchoalveolar lavage (BAL) fluid and bronchial biopsies have produced conflicting data. This study assessed inflammatory cell numbers at 16:00 h and 04:00 h in bronchial biopsies of 13 healthy controls, 15 asthmatic patients with peak expiratory flow (PEF) variation < or =15% and 10 asthmatic patients with PEF variation >15%. There was no significant increase at night in the number of CD3, CD4, CD8, CD25, AAI (tryptase) and EG2-immunopositive cells in the submucosa in both groups. Numbers of EG2-positive cells in the two asthmatic groups were significantly higher than in healthy controls, both at 16:00 h (p<0.05) and 04:00 h (p<0.01). The number of EG2, CD4 and CD25-positive cells at 04:00 and 16:00 h tended to be higher in asthmatics with a PEF variation >15% than in asthmatics with PEF variation < or =15%. At 04:00 h the median numbers of EG2-positive cells (per mm basement membrane) in subjects with PEF variation >15% and < or =15% were 6 and 3 cells, respectively, and at 16:00 h 4 and 25 cells respectively. Increased nocturnal airway obstruction is not associated with increased numbers of inflammatory cells in the bronchial submucosa at night. Apparently, asthmatic patients with a peak expiratory flow variation >15% suffer from a higher overall severity of bronchial inflammation at night and during the day.