- Lung volumes
- Airway calibre
- Gas transfer
Spirometry: used in assessment of Lung volumes
--Volumes measured include:
* IC = Inspiratory capacity
* IRV = Inspiratory reserve volume
* TV = Tidal volume
* VC = Vital capacity
* FRC = Functional residual capacity
* RV = Residual volume
* ERV = Expiratory reserve volume
* TLC = Total lung capacity
Peak flow rates: used in assessment of Airway calibre
* Requires co-operation and maximum voluntary effort of the patient
* Flow rates measured include
- FVC = Forced vital capacity
- FEV1 = Forced expiratory volume in one second
* Absolute values depend on height, weight, age, sex and race
* FEV1 / FVC ratio is important
* Lung function can be classified as:Normal - Restrictive - Obstructive
* In restrictive lung disease FVC is reduced but FEV1/FVC is normal
* In obstructive lung disease FVC is normal or reduced and FEV1/FVC is reduced
Gas transfer: used in measurment of Arterial blood gases
* Also allow assessment of ventilation / perfusion mismatch
* Important parameters to measure are:
- pH
- Partial pressure of oxygen
- Partial pressure of carbon dioxide
* Technique is unreliable in the presence of other medical problems (e.g. anaemia)