Forced expiratory volume in 1 second FEV

Figure 3.1 A dual-phase response in a polyurethane foam worker after bronchial provocation with toluene diisocyanate (TDI). Early-phase bronchospasm is followed by spontaneous recovery, which in turn is followed by late-phase bronchospasm. The concentration of methacholine required to reduce the forced expiratory volume in 1 second (FEV,) by 20 per cent (PC20) fell from a baseline normal of 25 mg. ml 1 to 10 mg. ml 1 the day after TDI challenge (with permission from Bernstein, JA et ai., 1996).

Asthma is a common chronic inflammatory disorder that affects the airway passages of the lungs. Primarily, asthma is characterized by reversible, episodic narrowing of the airway s smooth muscle secondary to hypersecretion of mucus, hyper-reactivity, and mucosal edema. The narrowing may be of sudden or prolonged onset, which accounts for the varying degrees of airway obstruction seen in this disease. The hallmark of airway obstruction is a reduction in the forced expiratory volume in 1 second (FEV and the ratio of FEVj to the forced vital capacity (FVC). 

---