Who is healthy (‘normal’) ?
In every day 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,
- or diseases 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 tests,
- etc.