END-TIDAL CARBON-MONOXIDE CONCENTRATION IN CHILDHOOD HEMOLYTIC DISORDERS

Objectives: Endogenous carbon monoxide (CO) is produced mainly by heme catabolism. As CO is excreted solely by the lung, a simple technique for measuring the end tidal carbon monoxide (ETCO) level was assessed as a method for screening for haemolytic disease in children. Methods: Two end expiratory breath samples were collected from normal children and from children with haemolytic disease using a one way valve conne ctor between a mouth piece and an anaesthetic bag. The samples were an alysed by gas chromatography for CO and carbon for dioxide (CO2). The CO2 value was used to normalise the CO value to an alveolar concentrat ion. Carboxyhaemoglobin (HbCO) also was measured in the patient group for correlation analysis with ETCO. Results: A total of 21 children wi th beta thalassaemia major, 15 children with other haemolytic diseases (hereditary spherocytosis n=8, haemoglobin H disease n=3 and thalassa emia intermedia n=4) and 23 normal children were studied. The mean ETC O concentrations in the three groups were 3.21 p.p.m., 7.41 p.p.m. and 0.69 p.p.m., respectively, which were significantly different from ea ch other (P<0.0001). There was a significant correlation between ETCO and HbCO in the patient groups (r=0.85; P<0.0001). Conclusions: The en d expiratory breath collection device is a simple and feasible sample collection method. The results confirm that ETCO can be used clinicall y to distinguish children with a variety of haemolytic disorders from normal subjects.