Automatic end-expiratory air sampling device for breath hydrogen test in infants

An adaptive breath sampler for use with human subjects with an impaired respiratory function

An adaptive sampler for collecting 2.5 dm(3) samples of exhaled air from human subjects with an impaired respiratory function is described. Pressure in the upper respiratory tract is continuously monitored and the data used to control an automated system to collect select portions of the expired breathing cycle onto a mixed bed Tenax(trade mark) and Carbotrap(trade mark) adsorbent trap for analysis by GC-MS. The sampling approach is intended for use in metabolomic profiling of volatiles in human breath at concentrations greater than microg m(-3). The importance of experimental reproducibility in metabolomic data is emphasised and consequently a high purity air supply is used to maintain a stable exogenous volatile organic compound profile at concentrations in the range 5 to 30 microg m(-3). The results of a 90 day stability study showed that exogenous VOCs were maintained at significantly lower levels (40 times lower for isopropyl alcohol) and with significantly higher reproducibility (80 times lower standard deviation for isopropyl alcohol) than would have been be the case if ambient air had been used. The sampling system was evaluated with healthy controls alongside subjects with chronic obstructive pulmonary disease. Subjects were able to breathe normally with control subjects observed to breathe at a rate of 9 to 17 breaths per minute, compared to 16 to 30 breaths per minute for subjects with COPD. This study presents, for the first time, observations and estimates of intra-subject breath sample reproducibility from human subjects. These reproducibility studies indicated that VOCs in exhaled breath exhibit a variety of dynamic behaviours, with some species recovered with a RSD <30%, while other species were observed to have significantly more variable concentrations, 30 to 130% RSD. The approach was also demonstrated to reliably differentiate the differences in the VOC profiles between alveolar and dead space air.

End tidal carbon monoxide concentration in childhood haemolytic 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 connector between a mouth piece and an anaesthetic bag. The samples were analysed by gas chromatography for CO and carbon for dioxide (CO2). The CO2 value was used to normalise the CO value to an alveolar concentration. Carboxyhaemoglobin (HbCO) also was measured in the patient group for correlation analysis with ETCO.

RESULTS

A total of 21 children with beta thalassaemia major, 15 children with other haemolytic diseases (hereditary spherocytosis n=8, haemoglobin H disease n=3 and thalassaemia intermedia n=4) and 23 normal children were studied. The mean ETCO 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 each 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 end expiratory breath collection device is a simple and feasible sample collection method. The results confirm that ETCO can be used clinically to distinguish children with a variety of haemolytic disorders from normal subjects.