Pulmonary function studies in sickle cell anaemia

Pulmonary studies including the measurements of single-breath diffusing capacity for carbon monoxide (DL); Forced Vital Capacity (FVC); Residual Volume (RV) and Total Lung Capacity (TLC) were carried out in forty normal subjects; twelve patients with homozygous sickle cell anaemia and five patients with iron deficiency anaemia due to hookworm infestation. Normal subjects had a mean haemoglobin content of 13.4 g per 100 ml and a mean DL value of 28 ml/min/mmHg. In the patients with hookworm anaemia, the mean haemoglobin was 4.9 g per 100 ml while the mean DL value was 9 ml/min per mmHg. Patients with sickle cell anaemia had a mean haemoglobin content of 6.2 g/100 ml yet the mean DL value was 20 ml/min per mmHg. The study showed that patients with homozygous sickle cell anaemia have a disproportionately high DL value in the presence of severe anaemia which might be due to a chronically expanded pulmonary capillary blood volume as a compensatory mechanism to maintain an appropriate level of DL.