Ethane is a product of lipid peroxidation and can be measured in the exhaled air as an index of oxidative stress. Oxidant/antioxidant imbalance is important in the pathogenesis of chronic obstructive pulmonary disease (COPD). Therefore, we measured exhaled ethane in 22 patients with COPD (mean age +/- SEM, 59 +/- 8 yr; 19 male) and compared it with other noninvasive markers of oxidative stress and inflammation such as carbon monoxide (CO), measured electrochemically, and nitric oxide (NO), measured by chemiluminescence. Exhaled ethane was collected during a flow and pressure-controlled exhalation into a reservoir, discarding dead space air contaminated with ambient air. A sample of the collected expired air was analyzed by chromatography. Compared with normal subjects (n = 14; eight men; age, 33 +/- 2.8 yr), patients with COPD not on steroid treatment (n = 12; FEV(1), 58 +/- 6%) had elevated levels of exhaled ethane (2.77 +/- 0.25 and 0.88 +/- 0.09 ppb, respectively, p < 0.05), CO (5.96 +/- 0.50 and 2.8 +/- 0.25 ppm, p < 0.05) and NO (11.86 +/- 0.53 and 6.77 +/- 0.50 ppb, p < 0.05) levels. Ethane was correlated to FEV(1) (r = -0.67, p < 0.05). Patients receiving steroid treatment (n = 10; FEV(1), 56 +/- 2%) had lower levels of ethane (0.48 +/- 0.05 ppb) than did steroid-treated patients, whereas CO (5.99 +/- 0.63 ppm) and NO (9.11 +/- 0.53 ppb) levels were similar in the two treatment groups. Exhaled ethane is elevated, correlates with FEV(1), and is significantly lower in patients treated with steroids, so it may be complementary to the use of NO and CO in assessing and monitoring oxidative stress in COPD.

Patients with isolated diaphragm paralysis depend on recruitment of extradiaphragmatic respiratory muscles to increase ventilation, but little is known about exercise performance or the response of the inspiratory muscles to loaded breathing. By convention, unilateral diaphragm paralysis is regarded as a trivial condition whereas bilateral paralysis is considered to be potentially life-threatening. In fact, no data exist concerning exercise performance under these conditions. We studied incremental treadmill exercise performed by eight patients with bilateral diaphragm paralysis, eight patients with unilateral diaphragm paralysis, and eight age-matched control subjects. Respiratory muscle endurance (RME) was also measured by an inspiratory threshold loading method. Exercise time, compared with control subjects (671 seconds), was moderately reduced in unilateral diaphragm paralysis (512 seconds, p = 0.07) and further reduced in bilateral diaphragm paralysis (456 seconds, p = 0.02). Similarly, peak minute ventilation was lower in patients with unilateral diaphragm paralysis (84 L x min(-1), p = 0.01) and in patients with bilateral diaphragm paralysis (69 L x min(-1), p = 0.001) compared with control subjects (114 L x min(-1)). However, patients with unilateral diaphragm paralysis and patients with bilateral diaphragm paralysis had increased ratios of peak oxygen consumption to peak minute ventilation compared with control subjects (p = 0.0007 and p < 0.0001, respectively). Nine patients had normal RME; exercise time was moderately increased in these patients (502 seconds) compared with seven patients with reduced RME (461 seconds). In conclusion, although exercise performance is impaired in bilateral diaphragm paralysis, these patients can sustain a reasonable exercise load, particularly if RME is preserved and compensatory mechanisms have developed. In addition, exercise tolerance is diminished in patients with unilateral diaphragm paralysis.

Chronic obstructive pulmonary disease (COPD) is characterised by high morbidity and mortality. It remains unknown which aspect of lung function carries the most prognostic information and if simple spirometry is sufficient.Survival was assessed in COPD outpatients whose data had been added prospectively to a clinical audit database from the point of first full lung function testing including spirometry, lung volumes, gas transfer and arterial blood gases. Variables univariately associated with survival were entered into a multivariate Cox proportional hazard model.604 patients were included (mean±sd age 61.9±9.7 years; forced expiratory volume in 1 s 37±18.1% predicted; 62.9% males); 229 (37.9%) died during a median follow-up of 83 months. Median survival was 91.9 (95% CI 80.8–103) months with survival rates at 3 and 5 years 0.83 and 0.66, respectively. Carbon monoxide transfer factor % pred quartiles (best quartile (>51%): HR 0.33, 95% CI 0.172–0.639; and second quartile (51–37.3%): HR 0.52, 95% CI 0.322–0.825; versus lowest quartile (<27.9%)), age (HR 1.04, 95% CI 1.02–1.06) and arterial oxygen partial pressure (HR 0.85, 95% CI 0.77–0.94) were the only parameters independently associated with mortality.Measurement of gas transfer provides additional prognostic information compared to spirometry in patients under hospital follow-up and could be considered routinely.

Background -The aim of this study was to simulate an in flight environment at sea level with a fractional inspired concentration ofoxygen (Fio2) of0-15 to determine how much supplemental oxygen was needed to restore a subject's oxygen saturation (Sao2) to 90% or to the level previously attained when breathing room air (Fio2 of 0-21). Methods -Three groups were selected with normal, obstructive, and restrictive lung function. Using a sealed body plethysmograph an environment with an Fio2 of0-15 was created and mass spectrometry was used to monitor the Fio2. Supplemental oxygen was administered to the patient by nasal cannulae. Sao2 was continuously monitored and recorded at an Fio2 of 0-21, 0-15, and 0*15 +supplemental oxygen.Results -When given 2 JIm ofsupplemental oxygen all patients in the 15% environment returned to a similar Sao2 value as that obtained using the 21% oxygen environment. One patient with airways obstruction needed 3 Jm of supplemental oxygen to raise his Sao2 above 90%. Conclusions -This technique, which simulates an aircraft environment, enables an accurate assessment to be made of supplemental oxygen requirements. (Thorax 1996;51:202-203 new technique enables the required oxygen flow rate to be titrated to the patients' requirements.