Tuesday, October 19, 2010

Assessment gets by Lung function tests

Lung function tests Allows assessment of :
  1.  Lung volumes
  2.  Airway calibre
  3.  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
* Pulse oximetry gives an indirect estimate of gas transfer
* Technique is unreliable in the presence of other medical problems (e.g. anaemia)