There is increasing interest in ethane (C(2)H(6)) in exhaled breath as a non-invasive marker of oxidative stress (OS) and thereby a potential indicator of disease. However, the lack of real-time measurement techniques has limited progress in the field. Here we report on a novel Tunable Diode Laser Spectrometer (TDLS) applied to the analysis of exhaled ethane in patients with lung cancer. The patient group (n=52) comprised randomly selected patients presenting at a respiratory clinic. Of these, a sub-group (n=12) was subsequently diagnosed with lung cancer. An age-matched group (n=12) corresponding to the lung cancer group was taken from a larger control group of healthy adults (n=58). The concentration of ethane in a single exhaled breath sample collected from all subjects was later measured using the TDLS. This technique is capable of real-time analysis of samples with accuracy 0.1 parts per billion (ppb), over 10 times less than typical ambient levels in the northern hemisphere. After correcting for ambient background, ethane in the control group (26% smokers) ranged from 0 to 10.54 ppb (median of 1.9 ppb) while ethane in the lung cancer patients (42% smokers) ranged from 0 to 7.6 ppb (median of 0.7 ppb). Ethane among the non-lung cancer patients presenting for investigation of respiratory disease ranged from 0 to 25 ppb (median 1.45 ppb). We conclude that, while the TDLS proved effective for accurate and rapid sample analysis, there was no significant difference in exhaled ethane among any of the subject groups. Comments are made on the suitability of the technique for monitoring applications.

We report on a maintenance-free, ward-portable, tunable diode laser spectroscopy system for the ultra-sensitive detection of ethane gas. Ethane is produced when cellular lipids are oxidized by free radicals. As a breath biomarker, ethane offers a unique measure of such oxidative stress. The ability to measure real-time breath ethane fluctuations will open up new areas in non-invasive healthcare. Instrumentation for such a purpose must be highly sensitive and specific to the target gas. Our technology has a sensitivity of 70 parts per trillion and a 1 s sampling rate. Based on a cryogenically cooled lead-salt laser, the instrument has a thermally managed closed-loop refrigeration system, eliminating the need for liquid coolants. Custom LabVIEW software allows automatic control by a laptop PC. We have field tested the instrument to ensure that target performance is sustained in a range of environments. We outline the novel applications underway with the instrument based on an in vivo clinical assessment of oxidative stress.

The application of optical spectroscopy for rapid accurate measurement of breath biomarkers has opened up new possibilities for monitoring and diagnostics in recent years. Here, we report on how our recent advances in optical detection of ethane have enabled us to record dynamic breath ethane patterns for patients undergoing kidney dialysis. Ethane is well established as a breath biomarker for free radical induced cell degradation. Moreover, renal dialysis is known to induce such oxidative attack, and our measurements may offer insight into the nature of this assault. Specifically, we have discovered that patients undergo significant breath ethane elevation at the beginning of each dialysis session. We have found an inverse relationship between the magnitude of this effect and number of months patients have been receiving treatment. We comment on how further refinements of our technology will allow a more detailed evaluation of the ethane elevation effect and ultimately lead to the assessment of potential interventions.

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There is growing evidence that oxidative stress is increased in haemodialysis patients and that dialysis per se is a contributory factor. The elevated oxidant stress, a result of increased production of reactive oxidant species (ROS), may be due to increased pro-inflammatory activity and reduced antioxidant mechanisms. ROS are transitory molecules and therefore surrogate markers of oxidant damage are required. Identification of potential causes of oxidative damage such as dialyser membranes or dialysate has been proposed and therefore assessment of oxidative damage during a single dialysis session would be of interest. We have used breath ethane, a widely accepted marker of oxidative stress, to investigate the cause and extent of the resulting oxidative damage during single dialysis sessions. Our study involved assessment of breath ethane levels during haemodialysis in an end-stage renal failure haemodialysis population (n = 24). Breath samples were collected using discrete sampling techniques and were subsequently analysed using laser spectroscopy. Each patient adopted the role of longitudinal control in this study and his or her breath ethane level was monitored regularly during the dialysis session. Significant breath ethane elevation was observed at the beginning (within the first 10 min) of each dialysis session. This paper provides an in-depth statistical analysis and clinical discussion of the recent findings. A regression analysis of the collected breath ethane data showed a trend towards increased ethane levels for patients on dialysis for a shorter duration of time (r = 0.656, R-Sq = 43.3%, p = 0.001). Multiple linear regression was undertaken to further assess these associations and revealed that peak ethane levels were significantly and independently associated with time period on dialysis (p < 0.000), vascular access (p = 0.013) and male sex (p = 0.005). However, whilst diabetes status had demonstrated a correlation with peak ethane levels (0.525, p = 0.008) this was not independent of vascular access status. This multivariate linear model was significantly associated with Ln peak ethane levels (S = 0.744, R-Sq = 80.8%). The observed rapid rise in oxidative stress during the first few minutes after commencement of dialysis gives new insight into the dynamics of the oxidative damage resulting from dialysis treatment.