Does haemodilution reduce the proportion of type II muscle fibres in patients with chronic obstructive lung disease?
Haemodilution in patients with chronic obstructive lung disease significantly reduces the abnormally high proportion of type II muscle fibres, suggesting hypoxaemia drives this fibre type transformation.
The study comprised nine patients with chronic obstructive lung disease. Quadriceps muscle biopsies were studied with respect to fibre type composition before and after haemodilution that brought haemoglobin (Hb) to within normal limits. Ten days elapsed between the two biopsy occasions. The arterial oxygen tension (PaO2) and saturation (SaO2) were depressed to 8.4 +/- 2.0 kPa and 89 +/- 11% in the patients with chronic obstructive lung disease and increased to 9.2 +/- 2.1 and 91 +/- 8% with haemodilation. The type II fibre proportion was 71 +/- 12% before haemodilation and significantly higher than normal (reference group, see Aniansson et al. 1981). Following haemodilation the proportion of type II fibres decreased significantly to 60 +/- 14%. The proportion of type II fibres was directly related to the haemoglobin content before, but not after, haemodilation and was inversely related to PaO2 and SaO2 both before and after haemodilation. In conclusion, hypoxaemia may be a factor underlying the high proportion of type II fibres found in patients with chronic obstructive lung disease.
Hildebrand et al. (Fri,) studied this question.