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PubMed1986

Bovine herpesvirus-1 and Pasteurella haemolytica aerobiology in experimentally infected calves.

Eight calves (2 calves in each of 4 groups) were exposed to an aerosol of bovine herpesvirus-1 (BHV-1) and 4 days later to an aerosol of Pasteurella haemolytica. Samples of tracheal and exhaled air were taken simultaneously beginning 1 day before viral exposure and once a day up to 3 to 4 days after the bacterial exposure. Samples were also taken during the period of aerosol exposure. Only 0.04% to 0.42% of P haemolytica-carrying droplets of the bacterial aerosol passed beyond the cranial part of the respiratory tract to the trachea. Nevertheless, numbers of bacteria as few as 1 bacterium/L of tracheal air were sufficient to produce fatal disease in the lungs of BHV-1-infected calves. In 1 of 4 groups, BHV-1 was isolated from most daily samples of exhaled and tracheal air. Pasteurella haemolytica was isolated 7 times more frequently from air when calves were kept at 1 C than when calves were kept at 23 C. The number of P haemolytica-carrying droplets in exhaled air was low (less than 1/L of air); however, samples obtained during the time that calves were coughing contained up to 10 P haemolytica-carrying droplets/L of air. It was learned that the cranial part of the respiratory tract serves as an efficient filter on inhalation and exhalation, but this filter is deficient in the animal when coughing occurs. This process expels infective droplets of size suitable for inhalation by other cattle in close proximity.

Aerosols↗
PubMed1984

Effect of alcoholic cirrhosis on ethane and pentane levels in breath.

Lipid peroxidation can be monitored by measuring one or several highly volatile alkanes in exhaled air. The concentrations of ethane and pentane were determined in breath samples from patients with alcoholic and non-alcoholic cirrhosis as well as from healthy subjects. The greatest increase of exhaled pentane was found in 17 patients with alcoholic cirrhosis (2.85 +/- 2.37 pmol/ml) in comparison with 10 patients with non-alcoholic cirrhosis (0.71 +/- 0.33 pmol/ml) and 10 control subjects (0.59 +/- 0.41 pmol/ml). On the contrary, no significant difference was detected as far as exhaled ethane is concerned. These data suggest that: a) gas-chromatographic determination of exhaled pentane may play a significant role in detecting alcohol-induced liver disease; b) hepatic injury may be mediated by lipid peroxidation in these patients.

Breath Tests↗
PubMed1977

[Pharmacokinetics of methylmethacrylate monomer of bone cements: method for qualitative and quantitative monomer determination in respiratory air].

The methylmethacrylate-monomer deported into circulation from bone cement implantation during endoprothetic operation is subject to unaltered exhalation. Qualitative evidence of monomer excretion in the exhaled air is established in animal experiment. The quantitative determination of monomer in the exhaled air in man undergoing hip-joint replacement are stated and the method is demonstrated. Pharmacocinetically exhalation has priority over metabolisation.

Acetabulum↗
PubMed1997

Detection of impaired intrapulmonary convective mixing by aerosol bolus dispersion in patients with emphysema.

The broadening of an inhaled aerosol bolus (aerosol bolus dispersion) during respiration provides a noninvasive, nonradioactive, and easy to perform technique which is a measure of the extent of convective gas mixing processes in the lung and symmetry of ventilation during the breathing cycle. In this study, this technique was evaluated for the ability to detect ventilation inhomogeneities in pulmonary emphysema (PE). An aerosol bolus undergoes changes in shape between its inspiration and expiration. In comparison with the inhaled bolus, the exhaled bolus is more spread because of convective mixing and may have a shift in the location of the mode caused by asymmetries of filling and emptying of lung units. We hypothesized that in PE these changes differ from healthy subjects and are related to lung health. Twenty nine patients with PE inhaled 25 ml boluses containing 0.9 micron monodisperse aerosol particles into volumetric lung depths of 200, 400, 600, and 800 cm3. The control group were 79 healthy subjects. As each bolus was expired, we measured bolus dispersion (volumetric width at one-half aerosol concentration peak height) and mode shift. In patients with PE exhaled boluses were significantly broader than those exhaled by normal subjects at all volumetric lung depths. At a lung depth of 800 cm3, patients showed a bolus dispersion that was 52% greater than that of healthy subjects (p < 0.0001) and they exhaled the bolus mode earlier (p < 0.0001). Aerosol bolus parameters were not influenced by anthropometric data. Pulmonary function parameters indicating obstruction showed a weak negative correlation with aerosol bolus parameters (R2 < 0.4). The bolus parameters appeared to be supplemental to conventional lung function tests and significantly indicated marked ventilation asymmetry and altered convective gas transport in pulmonary emphysema. The results support the use of the aerosol bolus dispersion test in assessing peripheral parenchymal lung injury.

Administration, Inhalation↗
PubMed1997

Pharmacokinetics of methanol and formate in female cynomolgus monkeys exposed to methanol vapors.

The 1990 Clean Air Act Amendments contain mandates for reduced automotive emissions and add new requirements for the use of alternative fuels such as methanol to reduce certain automotive pollutants. Methanol is acutely toxic in humans at relatively low doses, and the potential for exposure to methanol will be increased if it is used in automotive fuel. Formate is the metabolite responsible for neurotoxic effects of acute methanol exposure. Since formate metabolism is dependent on folate, potentially sensitive folate-deficient subpopulations, such as pregnant women, may accumulate formate and be at higher risk from low-level methanol exposure. Our objective was to determine the pharmacokinetics of 14C-methanol and 14C-formate in normal and folate-deficient monkeys after exposure to 14C-methanol vapors at environmentally relevant concentrations: below the threshold limit value (TLV), at the TLV of 200 parts per million (ppm), and above the TLV. Four normal adult female cynomolgus monkeys were individually anesthetized with isoflurane, and each was exposed by endotracheal intubation to 10, 45, 200, or 900 ppm 14C-methanol for 2 hours. Concentrations of the inhaled and exhaled 14C-methanol, blood concentrations of 14C-methanol and 14C-formate, exhaled 14C-carbon dioxide (14CO2), and respiratory parameters were measured during exposure. After exposure, 14C-methanol and 14CO2 exhaled, 14C-methanol and 14C-formate excreted in urine, and 14C-methanol and 14C-formate in blood were quantified. The amounts of exhaled 14C-methanol and 14CO2, blood concentrations of 14C-methanol and 14C-formate, and 14C-methanol and 14C-formate excreted in urine were linearly related to methanol exposure concentration. For all exposures, blood concentrations of 14C-methanol-derived formate were 10 to 1000 times lower than endogenous blood formate concentrations (100 to 200 mM) reported for monkeys and were several orders of magnitude lower than levels of formate known to be toxic. Since the metabolism of formate in primates depends on the availability of tetrahydrofolate, the same four monkeys were next placed on a folate-deficient diet until folate concentrations in red blood cells consistent with moderate folate deficiency (29 to 107 ng/mL) were achieved. Monkeys were then reexposed to the highest exposure concentration, 900 ppm 14C-methanol, for a similar 2-hour period, and again the pharmacokinetic data described above were obtained. Even with a reduced folate status, monkeys exposed to 900 ppm methanol for 2 hours had peak concentrations of methanol-derived formate that were well below the endogenous levels of formate. Although these results represent only a single exposure and therefore preclude broad generalizations, they do suggest the body contains sufficient folate stores to effectively detoxify small doses of methanol-derived formate from exogenous sources, such as those that might occur during normal use of automotive fuel.

Adult↗
PubMedDate not supplied

Real-time measurement of particulate matter deposition in the lung.

Air pollution and cigarette smoke are recognized health risks. A method was developed for the measurement of the deposition fraction (DF) of polydisperse particulate matter (PM) in human airways. Ten normal volunteers [three females, age range 18-67 years, mean age (SD) 43.9 (14)] made single breath exhalations after inhalation to total lung capacity. The exhaled breath was diverted to a multichannel laser diffraction chamber where the particulate profiler measured 0.3 - 1.0-microm particles. DF was inversely related to expiration flow-rate, 0.69 (0.02) at 4 l min-1 and 0.5 (0.01) at 13 l min-1, respectively (p<0.05), and was influenced by the inhalation flow-rate [0.70 (0.02) at 3 l min-1 and 0.59 (0.02) at 13 l min-1, respectively (p<0.05)], while no differences were found between nasal and oral inhalation (0.68 (0.05) versus 0.67 (0.06), p>0.05). Higher breath holding times were associated with elevated DF [0.74 (0.02) at 20 s, and 0.62 (0.05) without breath holding (p<0.01)]. When the expiratory flow was controlled and the breath hold time standardized, DF was reproducible (CV = 4.85%). PM can be measured in the exhaled breath and its DF can be quantified using a portable device. These methods may be useful in studies investigating the health effects of air pollution and tobacco smoke.

Adolescent↗
PubMed2003

Evaluation of the level of nicotine dependence among adolescent smokers.

The questionnaire containing ten items evaluated the degree of dependence in students-volunteers from Brno secondary and vocational schools (ages ranging from 15 to 17 years) and the anamnestic data were compared with the specific (urinary cotinine) and non-specific (CO in the air exhaled) biological tests of exposure to smoking. The sample of 147 students examined contained 42% non-smokers, 25% occasional smokers and almost 33% of those who smoked every day. Almost 10% children smoked more than 10 cigarettes a day, and more than 20% children stated that they smoked 60 and more cigarettes a week. In accordance with the pre-developed degrees of dependence, compiled by the scores of the individual responses, 59% of the respondents (including the non-smokers) were ranked among the non-dependent. The second most frequent group contained the "strongly dependent" (almost 17% of all persons, e.g. 30% of smokers), 3.4% of examined persons (6% of smokers) were ranked in the sub-group of persons with a very high degree of dependence. Highly positive correlations were found between the evaluation of the dependence degree according to the anamnestic data and the exposure bio-markers (urinary cotinine/creatinine and CO in the air exhaled): the values of correlation coefficients were 0.615 and 0.764, resp. Both bio-markers also correlated negatively with the time of the last exposure to both active and passive smoking. The individual items in the dependence questionnaire had positive correlations with the objective exposure indicators which had statistical significance. The strongest relationship was observed in the question about the first morning cigarette--the highest correlation coefficients, being followed by signs evaluating the smoking frequency and the usual number of cigarettes smoked per day and in a week. The lowest relationships concerned the occasions for smoking and the unpleasant symptoms associated with the withdrawal. The anamnestic questionnaire could explain 42.6% of urinary cotinine level variability (converted to the density measured by creatinine content) and 65.8% of variability of CO content in the air exhaled. It was demonstrated that regular adolescent smokers at the ages between 15 to 17 years inhaled the cigarette smoke and the young smokers' inner exposure to nicotine had been proved as well. In this age group, there are many individuals who have a strong or a very strong dependence on nicotine. As a result, it is necessary to promote smoking cessation and nicotine dependence treatment by recommending pharmaceuticals of substantial nicotine therapy.

Adolescent↗
PubMed2005

[Methods of expired nitric oxide assessment in pulmonary diseases in children].

Assessment of exhaled nitric oxide (eNO) creates new diagnostic possibilities for evaluation of the inflammatory process especially in children, in whom not all of the contemporary methods of diagnosing respiratory tract diseases are applicable. eNO concentration can be measured in children of all age, including neonates. Direct assessment of eNO is possible with an on-line method, in which NO is directly exhaled into a chemiluminescence analyser. An off-line method is performed by exhalation into a collapsible bag of nonreacting material and analysing the collected air with appropriate analysers. eNO measurement is a non-invasive, repeatable, rapid and sensitive method, producing results even during measurement. Assessment of eNO in children may be used to quantify inflammation in asthma and other respiratory tract diseases specific for this age group. Monitoring of the therapy and response to the anti-inflammatory agents i.e. glucocorticosteroids and anti-leukotriene drugs can also be based on eNO measurement.

Breath Tests↗
PubMed2005

[Measurement of airway inflammation in asthma].

Despite of the tremendous progress, which was made within the last few years in the diagnostics and treatment of asthmatic patients, there is a lack in a simple, non-invasive methods, which could be useful in the diagnostics and anti-inflammatory treatment monitoring. Invasive methods, such as bronchofiberoscopy (bronchoalveolar lavage fluid analysis and bronchial biopsy), enabled the better understanding of the pathophysiology of asthma and the elaboration of the grounds of pharmacological treatment of this disease. Unfortunately, these methods are less useful in the clinical practice due to their invasiveness. Spirometry, which is essential in diagnostics and treatment of asthmatics, is only indirect way of the airway inflammation assessment. Recent studies are focused on noninvasive methods of the evaluation of airway inflammation, such as measurements of exhaled nitric oxide (FENO) and allergic inflammation mediators in the inducible sputum. The higher degree of inducible form of nitric oxide synthase (iNOS) expression and higher levels of nitric oxide in exhaled air are observed in asthmatic patients. Many studies confirm, that the measurement of exhaled nitric oxide is a simple, non-invasive method in diagnostics and treatment monitoring in asthmatics, which does not intensify the symptoms of asthma.

Asthma↗
PubMed1985

Thermodilution cardiac output measurement. Effects of the respiratory cycle on its reproducibility.

Thermodilution cardiac output measurements are commonly employed in the management of critically ill patients. Serial measurements often show significant variation, and poor reproducibility limits their clinical utility. There are no clinical studies revealing when to perform thermodilution cardiac output measurements in relation to the respiratory cycle. We prospectively studied 32 patients in a randomized scheme comparing three thermodilution cardiac output measurements at peak-inspiration, at end-exhalation, or randomly in spontaneously breathing and mechanically ventilated patients. Saline injections initiated at peak-inspiration or end-exhalation resulted in cardiac output measurements with much smaller standard deviations than those seen with random injections. Thermodilution cardiac output measurements performed at random times in the respiratory cycle should be avoided, and we recommend initiating these measurements at end-exhalation.

Cardiac Catheterization↗
PubMed1996

Measurement of expired nitric oxide levels in children.

Nitric oxide (NO) can be measured directly in expired air in adults. The purpose of our study was to measure NO levels in children and to compare these values with adults. Exhaled NO was measured in 39 normal prepubertal children (23 girls), aged 9-11 years (mean 9.9 years). Exhaled NO was measured by the chemiluminescence method that is sensitive in a range of 2 to 4,000 ppb of NO on an adapted analyzer (Dasibi Environmental). Wearing a nose clip. 5 measurements were recorded in each child with exhalation 1) directly into the NO analyzer (flow rate 240 mL/min) with measurements of NO, carbon dioxide, and mouth pressure; and 2) using a T-piece to allow measurements at a different flow rate. For all measurements, background NO levels were less than 10 ppb. The mean direct level was 49.6 ppb, SD 37.8 (range, 11.5-197.2 ppb) compared with T-piece levels of 29.2 ppb. SD 27.1 (range, 5.1-141.2 ppb). There was no significant difference between boys and girls for direct or T-piece recordings. Mean direct NO in boys was 43.1 ppb, SD 40.5 and in girls 55.2 ppb, SD 35.4; mean T-piece in boys was 25.6 ppb. SD 29.2 and in girls 33.8 ppb, SD 25.1. Mean NO levels in prepubertal children are lower than in adults and show no difference between males and females.

Adult↗
PubMed1977

Investigations into the metabolism and mode of action of the colon carcinogens 1,2-dimethylhydrazine and azoxymethane.

Colon cancer can be induced reliably in rodents with 1,2-dimethylhydrazine and azoxymethane (AOM). Our studies deal with the mode of action of these compounds and their organotropism. A partial summary of our previous work on the metabolism of 1,2-dimethylhydrazine and its inhibition by disulfiram, carbon disulfide and other thiono-sulfur compounds is presented. On-going studies with AOM-14C indicate that in male F-344 rats, this carcinogen is rapidly metabolized to 14CO2 (37%, 48 hours), and to methylazoxymethanol-14C (MAM) (0.6--1%), which, along with other metabolites, appears in the urine. Pretreatment of rats with phenobarbital or chyrsene increased exhaled 14CO2 to 53% and 65%, respectively. Pretreatment with disulfiram or CS2 causes a complete, although transient, inhibition of exhaled 14CO2, decreases urinary MAM, and increases significantly the levels of unmetabolized AOM in the exhaled air and in urine. Thus, phenobarbital and chrysene appear to stimulate, while disulfiram and CS2 appear to inhibit, the metabolism of AOM. In vitro hydroxylation of AOM to MAM was demonstrated with rat liver homogenates and microsomal fractions. A hypothetical scheme for the endogenous formation of AOM is presented.

Animals↗
PubMed2005

Biomedical risk assessment as an aid for smoking cessation.

BACKGROUND: A possible strategy for increasing smoking cessation rates could be to provide smokers who have contact with healthcare systems with feedback on the biomedical or potential future effects of smoking, e.g. measurement of exhaled carbon monoxide (CO), lung function, or genetic susceptibility to lung cancer. We reviewed systematically data on smoking cessation rates from controlled trials that used biomedical risk assessment and feedback. OBJECTIVES: To determine the efficacy of biomedical risk assessment provided in addition to various levels of counselling, as a contributing aid to smoking cessation. SEARCH STRATEGY: We systematically searched he Cochrane Collaboration Tobacco Addiction Group Specialized Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1966 to 2004), and EMBASE (1980 to 2004). We combined methodological terms with terms related to smoking cessation counselling and biomedical measurements. SELECTION CRITERIA: Inclusion criteria were: a randomized controlled trial design; subjects participating in smoking cessation interventions; interventions based on a biomedical test to increase motivation to quit; control groups receiving all other components of intervention; an outcome of smoking cessation rate at least six months after the start of the intervention. DATA COLLECTION AND ANALYSIS: Two assessors independently conducted data extraction on each paper, with disagreements resolved by consensus. MAIN RESULTS: From 4049 retrieved references, we selected 170 for full text assessment. We retained eight trials for data extraction and analysis. One of the eight used CO alone and CO + Genetic Susceptibility as two different intervention groups, giving rise to three possible comparisons. Three of the trials isolated the effect of exhaled CO on smoking cessation rates resulting in the following odds ratios (ORs) and 95% confidence intervals (95% CI): 0.73 (0.38 to 1.39), 0.93 (0.62 to 1.41), and 1.18 (0.84 to 1.64). Combining CO measurement with genetic susceptibility gave an OR of 0.58 (0.29 to 1.19). Exhaled CO measurement and spirometry were used together in three trials, resulting in the following ORs (95% CI): 0.6 (0.25 to 1.46), 2.45 (0.73 to 8.25), and 3.50 (0.88 to 13.92). Spirometry results alone were used in one other trial with an OR of 1.21 (0.60 to 2.42). Two trials used other motivational feedback measures, with an OR of 0.80 (0.39 to 1.65) for genetic susceptibility to lung cancer alone, and 3.15 (1.06 to 9.31) for ultrasonography of carotid and femoral arteries performed in light smokers (average 10 to 12 cigarettes a day). AUTHORS' CONCLUSIONS: Due to the scarcity of evidence of sufficient quality, we can make no definitive statements about the effectiveness of biomedical risk assessment as an aid for smoking cessation. Current evidence of lower quality does not however support the hypothesis that biomedical risk assessment increases smoking cessation in comparison with standard treatment. Only two studies were similar enough in term of recruitment, setting, and intervention to allow pooling of data and meta-analysis.

Biofeedback, Psychology↗
PubMed1994

Biological monitoring of exposure to low concentrations of styrene.

A field study was conducted on 39 male workers exposed to styrene at concentrations below 40 ppm (time weighted average, TWA). Analyses were carried out on environmental air, exhaled air, blood, urine, and two major urinary metabolites of styrene: mandelic acid (MA) and phenylglycoxylic acid (PGA). Head space gas chromatography (GC) with a flame ionization detector (FID) was used for determination of styrene in blood and urine. Postexposure exhaled air was analyzed using capillary GC. Environmental styrene exposure was measured by personal sampling using carbon cloth personal samplers. Urinary metabolites of styrene were determined by high pressure liquid chromatograph (HPLC). When the end-of-shift breath, blood, and urine styrene levels were compared with environmental TWA values, blood styrene correlated best with styrene in air (r = 0.87), followed by breath styrene (r = 0.76). Poor correlation (r = 0.24) was observed between environmental styrene exposure and urine styrene. When styrene metabolites were compared with environmental styrene, the sum of urinary MA and PGA correlated better with styrene in air than MA or PGA alone. The correlations between urinary metabolites and environmental styrene improved when corrected for the specific gravity of urine. Even better correlations were observed when the urinary metabolites were corrected for creatinine. The correlation coefficients for environmental styrene and end-of-shift MA, PGA, and MA+PGA were 0.83, 0.84, and 0.86, respectively. The correlation coefficients between environmental styrene and next morning urinary metabolites fell to 0.47, 0.61, and 0.65 for MA, PGA, and MA+PGA, respectively. These results suggest that determination of the total MA and PGA in urine samples is preferred than separate measurements of MA or PGA. The good correlation between environmental exposure and styrene in the exhaled air also suggests that breath styrene level can be a useful indicator for low level styrene exposure, as the method is specific, noninvasive, and rapid. Urinary styrene seems to be a less reliable indicator for low level styrene exposure.

Adult↗
PubMedDate not supplied

Assessment of the effect of respiration on the esophageal variceal blood flow using transesophageal real-time two-dimensional Doppler echography.

The effect of spontaneous respiration on esophageal variceal flow was evaluated using 5 MHz color flow Doppler echography. Twenty-one patients with esophageal varices, of whom 19 had liver cirrhosis (95%), were examined with a convex array transesophageal transducer. The direction and velocity of the variceal flow during inhalation and exhalation could be inferred from the color, its brightness or the Doppler time-velocity spectrum. The mean intravariceal flow velocity was significantly higher during inhalation (20.6 cm per sec) than in exhalation (11.5 cm per sec; p less than 0.01). The direction of intravariceal flow at any given point did not change throughout the respiratory cycle. However, a combination of real-time color flow imaging and the doppler time-velocity spectrum revealed that, when the sampling point was near the peak of the curve of the varix, the spectrum falsely indicated reversal of direction between inhalation and exhalation. This semiinvasive method, which yields anatomical and physiological information simultaneously, appears to be very useful for the study of variceal flow.

Adult↗
PubMed1983

Comparative toxicokinetics of 2,3-14C-and 1-14C-acrylonitrile in the rat.

The tissue distribution, elimination and covalent binding of 2,3-14C-and 1-14C-acrylonitrile (VCN) were studies in male Sprague-Dawley rats given an oral dose of 46.5 mg kg-1. Exhalation of unchanged VCN, 14CO2 and H14CN was monitored at selected intervals. Only 5% of the total dose administered was recovered was unchanged VCN. Rate given 2,3-14C-VCN exhaled only 2% of 14C activity was 14CO2 and none was recovered as H14CN, whereas rats given 1-14C-VCN exhaled about 12% of 14C activity as 14CO2 and 0.5% as H14CN. In the initial 24 h, 40% of radioactivity from 1-14C-VCN appeared in urine, while 60% was recovered in the urine of rats given 2,3-14C-VCN. The red blood cells retained significant amounts of radioactivity from both the compounds for more than 10 days after administration, whereas the 14C activity in plasma declined sharply. The highest level of radioactivity from both compounds was recovered in the gastrointestinal tract. In liver, kidney, brain, spleen, adrenal, lung and heart tissues the unbound percent radioactivity decreased, while irreversible percent covalent binding to macromolecules in relation to total increased concomitantly. Subcellular fractionation of the tissues showed that most of the covalently bound radioactivity was distributed in non-cytosolic fractions. As compared to 1-14C-VCN administered animals, the percentage of covalent binding of 2,3-14C-VCN was significantly higher even 72 h after dosing. The relationship between covalent binding and acrylonitrile toxicity is discussed.

Acrylonitrile↗
PubMed1989

Reducing inadvertent PEEP by controlling end-tidal pressures in the trachea.

Mechanical ventilation using exhalation times too brief for completion of exhalation results in inadvertent positive end-expiratory pressure (IPEEP) and increased functional residual capacity (FRC). The endotracheal (ET) tube with side lumen allows us to monitor tracheal airway pressures and to determine the contributions of the ET tube to IPEEP. We hypothesized that, during rapid rate ventilation, controlling the positive end-expiratory pressure (PEEP) level in the trachea rather than at the ET tube adaptor will counter effects of the ET tube on IPEEP and result in less increase of FRC. Thirteen anesthetized rabbits were ventilated at rates of 30, 60, 90, and 120 breaths per minute (BPM). Peak inspiratory pressure was held constant, and PEEP was adjusted to 2 cmH2O, measured conventionally at the proximal end of the ET tube. Pulmonary function tests were made and then repeated while PEEP was held constant in the trachea, measured at the distal end of the ET tube. Controlling PEEP conventionally resulted in mean (+/- SE) FRC values of 13.7 +/- 3.8, 14.8 +/- 3.9, 17.1 +/- 4.5, and 21.1 +/- 5.3 ml/kg at 30, 60, 90, and 120 BPM, respectively. Controlling PEEP at the trachea yielded FRC values of 13.7 +/- 3.8, 13.6 +/- 3.4, 15.3 +/- 4.4, and 16.3 +/- 5.4 ml/kg, respectively. Increasing the ventilator rate above 60 BPM did not affect minute ventilation or blood gases. These results suggest that controlling PEEP in the trachea reduces effects of IPEEP on FRC by countering the contribution of the ET tube to the resistance of gas flow during exhalation.

Animals↗
PubMed1993

Is n-pentane really an index of lipid peroxidation in humans and animals? A methodological reevaluation.

Volatile hydrocarbons such as ethane and n-pentane are known to originate from peroxidation of polyunsaturated fatty acids in membrane lipids and they are accepted as a sensitive and direct index of lipid peroxidation both in vitro and in vivo. Until now, an appropriate and commonly accepted method for the analysis of volatile hydrocarbons in exhalation air has not been described. We therefore developed a methodology for routine application in humans that is based on cryofocusing in combination with gas chromatography and is adaptable to mass spectrometry. The samples may be stored in stainless steel bombs up to 3 weeks, and sample volumes necessary to analysis are variable and can be adapted to analytical requirements. The interference by water and carbon dioxide, always present in excess, is strongly reduced. Mass spectroscopic analysis of exhalation air in human control subjects demonstrates, however, the presence of isoprene as the major constituent hitherto identified as n-pentane. The commonly used columns fail to separate n-pentane and isoprene. Based upon studies of the diverse methodologies reported in literature, it must be assumed that the reported responses of the gas chromatographic "n-pentane" peak in exhalation air of humans and animals, hitherto identified exclusively by authentic reference gases, are actually responses to isoprene or, at least, a mixture of both n-pentane and isoprene.

Adult↗