Who is healthy (‘normal’) ?

In everyday life health can only be defined in terms of what it is not, i.e. by the absence of overt disease:

• no present or previous respiratory disease, which may directly or indirectly influence the respiratory system
• no skeletal abnormalities (e.g. kyphoscoliosis)
• no circulatory problems (e.g. cardiomegaly, hydrothorax)
• normal mental development
• engages in normal physical activities
• lifelong non-smoker
• capable of performing the spirometry tests