Table 2

Some of the most common causes of a carbon monoxide transfer coefficient (KCO) which is lower or higher than the reference value.

Low KCOHigh KCO
Diffuse alveolar damage Pulmonary fibrosis Connective tissue/ autoimmune disease Sarcoidosis, asbestosis, bleomycin -Pulmonary hypertension associated Vasculitis Thromboembolic Congestive heart failure/ mitral stenosis Pulmonary oedema Intrapulmonary shunting Pulmonary arteriovenous malformations Hepatopulmonary syndrome Airflow obstruction Emphysema Churg-Strauss syndrome BronchiolitisLoss of units (discrete) Pneumonectomy 21, 22 Local destruction/infiltrates Incomplete alveolar expansion Pleural disease 25 Neuromuscular 20 Chest wall deformity 26 Poor technique Alveolar haemorrhage 27 Anti-GBM disease Pulmonary vasculitis Wegener's granulomatosis SLE Idiopathic haemosiderosis Increased pulmonary blood flow ASD 28 Asthma 29

  • TL,CO (% pred) may also be high; GBM: glomerular basement membrane; SLE: systemic lupus erythematosus; ASD: atrial septal defect.