E. Fornai

Effects of nicotine replacement therapy on markers of oxidative stress in cigarette smokers enrolled in a smoking cessation program

Twenty healthy, asymptomatic long-term cigarette smokers (8 males, 12 females; mean age: 43 +/- 9 years) were selected at random from a larger series receiving nicotine replacement therapy (NRT) for 12 weeks to study the effects of NRT on plasma markers of oxidative stress. Plasma aliquots, obtained at baseline (T0) and after 12 weeks (T12) of NRT, were used to measure malondialdeyde (MDA) and total Trolox-equivalent antioxidant capacity (TEAC). In subjects who completely quit smoking (quitters, n = 10), MDA was higher at T0 (1.08 mumol/l, interquartile range 0.85-1.16) than at T12 (0.71 mumol/l, range 0.32-0.92; p < 0.01), and TEAC was lower at T0 (1.20 mM, range 1.11-1.31) than at T12 (1.43 mM, range 1.31-1.49; p < 0.05). In subjects who had only reduced the number of cigarettes smoked per day (reducers, n = 10), differences between the T0 and T12 levels of MDA (0.81 [0.75-0.96] vs. 0.76 [0.58-0.84] mumol/l) and TEAC (1.28 [1.05-1.50] vs. 1.25 [1.09-1.42] mM) were not significant. At T0, MDA and cotinine levels correlated in reducers (r = 0.79, p < 0.05) and, though not significantly, in quitters (r = 0.50, p = 0.12). At T12 this relationship between MDA and cotinine was still present in the reducers (r = 0.70, p < 0.05), while the scatter of points in quitters was completely dispersed (r = (0.09). These results show that smoking cessation but not smoking reduction is associated with decreased markers of oxidative stress in the plasma of active cigarette smokers.

Studies of regional ventilation in asthma using 81mKr.

Functional images of pulmonary ventilation during tidal breathing can be obtained with a gamma camera by adding a continuous flow of radioactive krypton-81m (half-life = 13 sec) to the inspired air. The procedure is readily repeatable and provides ventilation images.81mKr ventilation scans were obtained in six asthmatic patients in various phases of the disease. During acute exacerbations, while chest x-rays showed only large-volume lungs, ventilation scans were grossly abnormal, showing large, segmental, or even lobar areas of reduced ventilation as well as an increase in size of the lung images. Similar alterations, although less pronounced, were shown in patients with mild-to-moderate shortness of breath and wheezing. Bronchodilators immediately improved the ventilation defects and reduced lung size. There was further improvement and eventual restoration of normal patterns following prolonged hospital treatment.

The assessment of gas exchange by automated analysis of O2 and CO2 alveolar to arterial differences

SummaryA computer program to measure breath by breath alveolar pressure (PA) and alveolar to arterial difference (AaD) for O2 and CO2, by a mass-spectrometer has been implemented. The program allows the determination of alveolar gas by different methods: 1. Bohrs equation (BE); 2. ideal alveolar air equation for O2 (IDO2); 3. end-tidal (ET); 4. by the Rahns definition of ‘mean alveolar gas’, i.e., alveolar pressures are defined when instantaneous respiratory exchange ratio (IRQ) equals mean respiratory exchange ratio (MRQ). This automated technique has been used in 16 patients with chronic obstructive lung disease (COLD) and 15 patients with pulmonary embolism (APE). In both groups of patients it was always possible to find in each breath the point where IRQ=MRQ and therefore to measure AaD by RD. IDO2 was significantly lower than PAO2 by the other methods. Also ET values of O2 and CO2 were significantly different from RD and BE in both groups of patients, however the difference was consistently higher in COLD patients. The different shape of the expirograms (steeper expirograms in COLD) is responsible for this different result. RD and BE AaD characterize gas exchange more precisely than ET, because the contribution of high VA/Q units is also evaluated. This is particularly important in COLD patients.Consideration on dead space measurements are also reported both for COLD and APE patients. In conclusion this automated technique provides the assessment of gas exchange for the use in clinical respiratory physiology and for the monitoring of gas-exchange in critically ill patients.

Ventilation-perfusion heterogeneity and gas exchange variables in acute pulmonary embolism evaluated by two different computerized techniques

SummaryThe mechanisms by which the disturbances of gas exchange develop in human pulmonary embolism are unknown. We investigated whether the inequality of ventilation-perfusion ratio is associated with the abnormalities of pulmonary gas exchange as evaluated by two different computerized techniques. We measured the alveolar to arterial gradients of oxygen and carbon dioxide by means of a computer based system with a mass spectrometer and the ventilation-perfusion distributions by the multiple inert gas technique in 5 patients with acute pulmonary embolism. In these subjects there was a marked ventilation-perfusion inhomogeneity, as detected from inert gases and this finding was in agreement with the impairment of the alveolar to arterial gradients and of their derived indexes. Consideration on the responsible mechanisms for the disturbances of gas exchange are also reported. In conclusion these two computerized techniques provide a useful assessment of the ventilation-perfusion relationships in order to explain the disturbances of gas exchange in critically ill patients.

Computer Evaluation of Expiratory Gas Parameters and Alveolar to Arterial Differences in Clinical and Research Pulmonary Medicine

The determination of alveolar-arterial differences of O2 and CO2 allows assessment of the overall efficiency of gas exchange.