Tests to assess how the LUNGS are functioning. They range from simple spirometry (measuring breathing capacity) to sophisticated physiological assessments.

These include vital capacity (VC) – the maximum volume of air that can be exhaled slowly and completely after a maximum deep breath; forced vital capacity (FVC), a similar manoeuvre using maximal forceful exhalation; total lung capacity is the total volume of air in the chest after a deep breath in; functional residual capacity (FRC) is the volume of air in the lungs at the end of a normal expiration, with all respiratory muscles relaxed.

Dynamic lung volumes and flow rates reflect the state of the airways. The forced expiratory volume (FEV1) is the amount of air forcefully exhaled during the first second after a full breath – it normally accounts for over 75 per cent of the vital capacity. There are several other more sophisticated tests which may not be necessary when assessing most patients. Measurement of arterial blood gases is also an important part of any assessment of lung function.