Kevin Gleeson

Volatile organic compounds in breath as markers of lung cancer: a cross-sectional study.

BACKGROUND Many volatile organic compounds (VOCs), principally alkanes and benzene derivatives, have been identified in breath from patients with lung cancer. We investigated whether a combination of VOCs could identify such patients. METHODS We collected breath samples from 108 patients with an abnormal chest radiograph who were scheduled for bronchoscopy. The samples were collected with a portable apparatus, then assayed by gas chromatography and mass spectroscopy. The alveolar gradient of each breath VOC, the difference between the amount in breath and in air, was calculated. Forward stepwise discriminant analysis was used to identify VOCs that discriminated between patients with and without lung cancer. FINDINGS Lung cancer was confirmed histologically in 60 patients. A combination of 22 breath VOCs, predominantly alkanes, alkane derivatives, and benzene derivatives, discriminated between patients with and without lung cancer, regardless of stage (all p<0.0003). For stage 1 lung cancer, the 22 VOCs had 100% sensitivity and 81.3% specificity. Cross-validation of the combination correctly predicted the diagnosis in 71.7% patients with lung cancer and 66.7% of those without lung cancer. INTERPRETATION In patients with an abnormal chest radiograph, a combination of 22 VOCs in breath samples distinguished between patients with and without lung cancer. Prospective studies are needed to confirm the usefulness of breath VOCs for detecting lung cancer in the general population.

Effect of oxygen breathing following submaximal and maximal exercise on recovery and performance.

To determine whether supplemental oxygen following exercise hastens recovery or enhances subsequent performance we evaluated its effectiveness in 13 male athletes. The exercise periods consisted of two 5-min submaximal efforts on a treadmill ergometer followed by a single bout to exhaustion. Intervals of exercise were separated by a 4-min recovery period during which the subject breathed either 1) room air, 2) 100% oxygen, or 3) 2 min of 100% oxygen followed by 2 min of room air on three nonconsecutive days. We found that breathing 100% oxygen produced no significant difference on the recovery kinetics of minute ventilation or heart rate, or improvement in subsequent performance as measured by duration of exercise (3.33 +/- 0.04 min, air vs 3.46 +/- 0.03, oxygen) and peak VO2 (59.9 +/- 2.2 ml.kg-1.min-1, air vs 54.5 +/- 2.2, oxygen). In addition, the perceived magnitude of exertion estimated by the Borg scale was no different during oxygen breathing. These findings offer no support for the use of supplemental oxygen in athletic events requiring short intervals of submaximal or maximal exertion.

Pneumonia in the intensive care unit setting.

Nosocomial pneumonia is a common and serious occurrence in the ICU. It most often results from aspiration of oropharyngeal secretions that have become colonized with pathogenic enteric gram-negative bacilli. Colonization occurs in association with acute and chronic illness and particularly with therapy that includes nasogastric or endotracheal tubes, H2 blocking antacid drugs, or antibiotics; aspiration is increased by anesthesia, sedative drugs, and upper airway instrumentation. The diagnosis of ICU-acquired pneumonia is complicated greatly by the nonspecificity of clinical and laboratory data, and the difficulty in distinguishing the organisms producing infection from those merely colonizing the airway when using routine culture techniques. Among specialized diagnostic techniques, quantitative culture of specimens obtained with the protected sampling brush offers the most promise in establishing a specific microbacteriologic diagnosis of nosocomial pneumonia. Empirical treatment with broad spectrum antibiotics is frequently necessary when a specific diagnosis cannot be made. The poor outcome associated with nosocomial pneumonia, regardless of treatment, suggests that methods to prevent dissemination and oropharyngeal colonization of the offending organisms should be emphasized.

Human Sleep-Disordered Breathing

obstructive sleep apnea is a common clinical disorder primarily affecting men who have a long history of heavy snoring. The incidence of the illness increases with both aging and obesity; its major clinical manifestation is the complaint of daytime hypersomnolence. This illness has received a great deal of clinical and investigative attention in the last ten years because its occurrence appears almost epidemic in nature. In addition, apnea-associated cardiac rhythm abnormalities raise the question of the possible influence of obstructive sleep apnea on unexplained nocturnal death. Recently other associated cardiovascular abnormalities, such as sustained pulmonary and systemic hypertension, have resulted in further interest in this recently discovered illness.