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The alveolar-capillary membrane diffusing capacity and the pulmonary capillary blood volume in heart transplant candidates
  1. O A Al-Rawasa,
  2. R Cartera,
  3. R D Stevensona,
  4. S K Naikb,
  5. D J Wheatleyb
  1. aDepartment of Respiratory Medicine, Glasgow Royal Infirmary, Glasgow G31 2ES, UK, bUniversity Department of Cardiac Surgery, Glasgow Royal Infirmary
  1. Dr O A Al-Rawas, Department of Medicine, College of Medicine, Sultan Qaboos University, PO Box 35, Postal Code 123, Muscat, Sultanate of Oman email: orawas{at}


OBJECTIVES To determine the mechanism of impairment of pulmonary transfer factor for carbon monoxide (TLCO) in heart transplant candidates, as this is the most common lung function abnormality.

SETTING Regional cardiopulmonary transplant centre.

METHODS TLCO and its components (the diffusing capacity of the alveolar-capillary membrane (DM) and the pulmonary capillary blood volume (VC)) were measured using the Roughton and Forster method and the single breath technique in 38 patients with severe chronic heart failure awaiting heart transplantation (mean age 51 years, range 19 to 61; mean left ventricular ejection fraction 12.8%). Results were compared with data from 26 normal subjects (mean age 47 years, range 27 to 62).

RESULTS Mean per cent predicted TLCO, DM, and VC were significantly reduced in patients (69.9%, 81.4%, and 80.2% of predicted, respectively) compared with controls (97.7%, 100.1%, and 102.3% of predicted, respectively, p < 0.001). The relative contribution of the two components of TLCO in patients was similar to that of normal subjects, with each component accounting for approximately 50% of the total resistance to diffusion (1/TLCO).

CONCLUSIONS TLCO impairment in patients with severe chronic heart failure awaiting heart transplantation results from a proportionate reduction in both DM and VC, suggesting a significant disturbance of the pulmonary vascular bed.

  • heart failure
  • diffusing capacity
  • pulmonary transfer factor
  • pulmonary capillary blood volume
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