Question 5c

• Estimate for each of the subjects in the graph when the FEV1 has declined by 20%.

In the healthy subject the FEV1 does not fall by 20%; hence we cannot establish a PC20 or PD20 in that subject.

In the subject with mild asthma a fall in FEV1 of 20% is achieved at about 7 µmol histamine (PD20). In the patient with more severe asthma the PD20 is about 0.7 µmol, a 10-fold lower dose.