Extrapulmonary reduction in lung inflation (reduced VA) producing changes in DM or θVc that reduce DL,CO |
Reduced effort or respiratory muscle weakness |
Thoracic deformity preventing full inflation |
Diseases that reduce θVc and thus reduce DL,CO |
Anaemia |
Pulmonary emboli |
Other conditions that reduce θVc and thus reduce DL,CO |
Hb binding changes (e.g. HbCO, increased FI,O2) |
Valsalva manoeuvre (increased intrathoracic pressure) |
Diseases that reduce (in varying degrees) DM and θVc and thus reduce DL,CO |
Lung resection (however, compensatory recruitment of θVc also exists) |
Emphysema |
Interstitial lung disease (e.g. IPF, sarcoidosis) |
Pulmonary oedema |
Pulmonary vasculitis |
Pulmonary hypertension |
Diseases that increase θVc and thus increase DL,CO |
Polycythaemia |
Left-to-right shunt |
Pulmonary haemorrhage (not strictly an increase in θVc, but effectively an increase in lung Hb) |
Asthma |
Other conditions that increase θVc and thus increase DL,CO |
Hb binding changes (e.g. reduced FI,O2) |
Muller manoeuvre (decreased intrathoracic pressure as in asthma, resistance breathing) |
Exercise (in addition, a possible DM component) |
Supine position (in addition, possibly a slight increase in DM) |
Obesity (in addition, a possible DM component) |
VA: alveolar volume; DM: membrane conductivity; θ: carbon monoxide (CO)–haemoglobin (Hb) chemical reaction rate; Vc: volume of pulmonary capillary blood; FI,O2: inspired fraction of oxygen; IPF: idiopathic pulmonary fibrosis; Hb: haemoglobin.