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PubMed1991

Influence of the bicarbonate pool and on the occurrence of 13CO2 in exhaled air.

In 13CO2 breath tests, based on 13C:12C ratio measurements, the appearance of 13C in exhaled CO2 was monitored after the administration of a 13C-labelled compound. Independently of the substrate used, the existence of a bicarbonate pool into which the CO2 produced enters before being exhaled, imposes a delay on the appearance of changes in the 13C:12C ratio. To estimate the nature and magnitude of this delay, we applied a two-compartment model to describe the kinetics of the body bicarbonate pool and we evaluated the 13C:12C ratio of CO2 entering that pool from the measured 13C:12C ratio in the exhaled CO2 after an oral intake of "naturally labelled" 13C-glucose. Our results demonstrated that discrepancies between total and exogenous glucose oxidation in relation to the peak occurrence time, as well as the absolute quantities, could be adequately explained by the interference of the bicarbonate stores.

Bicarbonates↗
PubMedDate not supplied

Modeling the concentration of ethanol in the exhaled breath following pretest breathing maneuvers.

A previously developed mathematical model that describes the relationship between blood alcohol (ethanol) concentration and the concentration of alcohol in the exhaled breath at end-exhalation (BrAC) has been used to quantitate the effect of pretest breathing conditions on BrAC. The model was first used to "condition" the airways with different breathing maneuvers prior to simulating a single exhalation maneuver, the maneuver used in standard breath alcohol testing. On inspiration, the alcohol in the air reaches local equilibrium with the alcohol in the bronchial capillary bed prior to entering the alveolar region. On expiration, approximately 50% of the alcohol absorbed on inspiration is desorbed back to the airways. BrAC correlates with the amount of alcohol that is desorbed to the airways. The six pretest breathing conditions and the percent change in BrAC relative to the control maneuver were: hyperventilation (-4.4%), hypoventilation (3.7%), hot-humid air (-2.9%), hot-dry air (0.66%), cold-humid air (0.13%), and cold-dry air (0.53%). The mechanism underlying these responses is not due to changes in breath temperature, but, rather to changes in the axial profile of alcohol content in the mucous lining of the airways.

Air↗
PubMed1999

Inhaled and exhaled nitric oxide.

Inhaled nitric oxide (NO) is used to treat various cardiopulmonary disorders associated with pulmonary hypertension. The rationale is based on the fact that NO, given by inhalation, only dilates those pulmonary vessels that perfuse well-ventilated lung units. As a result, pulmonary gas exchange is improved while pulmonary vascular resistance is reduced and pulmonary blood flow is increased. Inhaled NO has been successfully applied to treat persistent pulmonary hypertension of the newborn, reducing the need for extracorporeal life support. Although pulmonary hypertension and altered vasoreactivity contribute to profound hypoxaemia in adult and paediatric acute respiratory distress syndrome (ARDS), the benefit of inhaled NO still remains to be established in patients with ARDS. ARDS is a complex response of the lung to direct or indirect insults, leading to pulmonary vasoconstriction and various inflammatory responses. Recent randomized trials suggest that inhaled NO only causes a transient improvement in oxygenation. Whether this effect is important in the long-term management of ARDS remains to be established. NO, measured in the exhaled breath, is an elegant and non-invasive means to monitor inflammation of the upper and lower respiratory tract. In the normal upper airways, the bulk of exhaled NO originates from the paranasal sinuses. Exhaled NO is increased in nasal allergy and decreased in cystic fibrosis, nasal polyposis and chronic sinusitis. That NO production is increased in asthmatic airways is also well established. However, several questions still need to be addressed, in particular evaluation of the sensitivity and specificity of the measurement techniques, and assessment of the bronchodilator action of endogenous NO.

Administration, Inhalation↗
PubMed1998

Application of a new method for analysis of exhaled gas in critically ill patients.

OBJECTIVE: Application of a new method for analysis of exhaled gas in critically ill patients. DESIGN: Open study. SETTING: Surgical intensive care unit of an university hospital. PATIENTS: Thirty-seven consecutive, critically ill, mechanically ventilated patients. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Chemical analysis of the patient's exhaled gas was based upon substance adsorption and concentration onto activated charcoal, microwave desorption and gas chromatographic separation. Patients with acute respiratory distress syndrome (ARDS) exhaled less isoprene than those without ARDS [9.8 (8.2-21.6) vs 21.8 (13.9-41.4) nmol/m2 per min [median (95% confidence interval)], p = 0.04]. In patients who developed pulmonary infection, pentane elimination increased from 0.4 (0.0-5.4) to 2.7 (0.6-6.1, p = 0.05) nmol/m2 per min and isoprene elimination decreased from 5.2 (0-33) to 5.0 (0-17, p = 0.05) nmol/m2 per min, resulting in a significant increase in pentane/isoprene ratio from 0.1 (0-0.3) to 0.4 (0-15, p = 0.007) when compared to patients without pulmonary infection. CONCLUSIONS: The new method allows quantitative analysis of human gas samples with low substance concentrations and is well suited for clinical studies which involve the investigation of metabolic processes in the lung and the body.

Adult↗
PubMed1999

Single breath exhaled nitric oxide in lung transplant patients: a preliminary clinical study.

Exhaled nitric oxide is considered as a marker of airway inflammation. We report here our preliminary experience with single-breath exhaled nitric oxide measured in lung transplant patients with and without bronchiolitis obliterans syndrome and in cardiac transplant patients. Peak and end-expiratory nitric oxide concentrations did not differ between groups, but single-breath exhaled nitric oxide recordings were strikingly different in patients suffering from bronchiolitis obliterans syndrome, with a slower decrease from peak to end-expiratory nitric oxide concentration. Further studies are required in order to determine whether theses abnormalities reflect the inflammatory process of bronchiolitis obliterans syndrome.

Adult↗
PubMed2003

Exhaled NO level and number of eosinophils in nasal lavage as markers of pollen-induced upper and lower airway inflammation in children sensitive to grass pollen.

OBJECTIVES: This study investigates the upper and lower inflammatory response induced by natural exposure to grass pollen in atopic and non-atopic children. METHODS: After children's atopic profile had been assessed, their nasal lavage fluid (NAL) and exhaled air was sampled once before and once during the pollen season. Level of nitric oxide (NO) was determined in exhaled air, and the following mediators were measured in NAL: ECP, IL-6, IL-8, albumin, uric acid, and urea. The number of eosinophils in NAL was determined after Giemsa staining. During the experiment ozone and pollen levels were measured continuously. RESULTS: During the pollen season the level of grass pollen was 95 pollen grains per cubic metre. At baseline, 8.0% and 5.4% of total cells in NAL of children sensitive to, respectively, house dust mite (HDM) and pollen + HDM were eosinophils, whereas virtually no eosinophils were observed in NAL of non-atopic children. In contrast to the non-atopic and HDM groups, in children sensitive only to grass pollen, grass pollen induced a threefold increase in the percentage of NAL eosinophils and a 2.5-fold increase in the NAL level of ECP ( P<0.05). In all groups, the NAL levels of albumin, uric acid, urea, IL-6 and IL-8 were not significantly increased by pollen exposure. At baseline, children sensitive to HDM showed significantly higher exhaled nitric oxide (eNO) values than non-atopic subjects and children sensitive only to pollen (79 to 141% increase). During pollen exposure eNO of children sensitive only to pollen increased from 35.8 to 64.5 ppb ( P<0.05), whereas no increase in eNO was observed in the other children. CONCLUSION: Pollen-sensitive children show a season-dependent upper and lower airway inflammatory response, resembling the continuous inflammation in HDM-sensitive children.

Biomarkers↗
PubMed2003

Tidal off-line exhaled nitric oxide measurements in a pre-school population.

UNLABELLED: Exhaled nitric oxide (ENO) is used as a non-invasive marker of airway inflammation. The aim of this study was to measure ENO in a pre-school population using a relatively novel method, the off-line tidal breathing method, and to investigate differences in ENO between subjects with different presentations of wheezing. ENO was measured in 129 children (median age 4.4 years, quartiles 4.0-4.8 years) through a mouth mask attached to a two-way valve with an expiratory resistance of 5 cm H(2)0. Mean tidal ENO concentration (tENO) was calculated from triplicate measurements. Mean +/- SEM tENO for 89 control subjects was 13+/-0.4 ppb (95%CI 11.8-13.7 ppb); this level was significantly different from tENO in 15 children with a history of recurrent wheezing (18.6+/-1.9 ppb; 95%CI 14.5-22.7 ppb; t-test P<0.0001). Mean tENO in 16 children with a single wheezing episode was 11.4+/-1.0 ppb (95%CI 9.2-13.6 ppb) and thus significantly different from the recurrent wheezing group (t-test P=0.0024). CONCLUSION: The off-line tidal breathing method is a feasible and appealing method for measuring exhaled nitric oxide in pre-school children. With this method, higher tidal exhaled nitric oxide levels were found in children with recurrent wheezing.

Breath Tests↗
PubMed2004

Exhaled nitric oxide levels in infants with chronic lung disease.

UNLABELLED: Chronic lung disease (CLD) is an inflammatory disorder; in patients with other inflammatory disorders exhaled nitric oxide (NO) levels are elevated. The aim of this study was to test the hypothesis that prematurely born infants with CLD would have elevated exhaled NO levels compared to those without CLD and healthy term-born infants. Ten infants with CLD (median gestational age 26 weeks; CLD group), ten infants without CLD (median gestational age 32 weeks; non-CLD group) and ten term-born infants (term group) were examined at post-conceptional ages between 36 and 45 weeks. NO levels were measured during spontaneous tidal breathing. A facemask was positioned over the infant's nose and mouth and a sampling catheter was inserted through a small leak-free valve into the facemask. To measure nasal NO, the tip of the sampling catheter was placed in the nasal space and to measure facemask NO, the catheter tip was positioned inside the facemask at the infant's lips. Nasal compared to facemask NO levels were higher in all three groups (CLD; non-CLD; term: P=0.017, P=0.012 and P=0.017, respectively). The CLD group had higher peak nasal and facemask NO levels than the non-CLD ( P=0.011 and P=0.034 respectively) and the term ( P=0.005 and P=0.01 respectively) infants. Regression analysis demonstrated that facemask NO levels were significantly related to CLD, independent of gestational, post-natal and post-conceptional age ( P=0.006). CONCLUSION: our results suggest that exhaled nitric oxide levels are elevated in chronic lung disease infants. Facemask measurement of nitric oxide levels might be a potentially useful method to monitor infants with chronic lung disease.

Case-Control Studies↗
PubMed1993

Application of thermal desorption to the biological monitoring of organic compounds in exhaled breath.

We have developed a thermal desorption-gas chromatographic method for the analysis of organic compounds in exhaled breath air, to be used in the biological monitoring of environmental exposure. The exhaled breath sampler is based on the concentration of compounds present in alveolar air in a solid sorbent material. Isoflurane (1-chloro-2,2,2-trifluoroethyl-difluoromethyl-ether), an inhaled anaesthetic used widely in surgery, and styrene, used in boat construction and the manufacture of fibreglass-reinforced plastics, are partially eliminated from the body in exhaled breath, samples of which can therefore be used to monitor biological exposure to these two organic compounds. Recoveries were tested in controlled atmospheres of isoflurane or styrene, with Chromosorb 106 or Tenax, respectively, as the adsorbent. We also investigated the influence of relative humidity, an important factor in breath sampling, on adsorption.

Air↗
PubMed1981

Comparison of lung diffusing capacity during rebreathing and during slow exhalation.

In five normal sitting subjects DLCO and Qc were measured from the disappearances of a stable isotope of carbon monoxide (C18O) and of acetylene with respect to an inert and insoluble reference gas (Helium). Measurements were made during two respiratory maneuvers: (1) during rebreathing both at functional residual capacity (FRC) and near total lung capacity (TLC); and (2) during a slow exhalation at a constant rate from TLC to FRC. Changes in gas concentration were measured at the mouth during both maneuvers with a respiratory mass spectrometer. Mean DLCO was significantly higher during rebreathing near TLC (34.6 ml . min-1 . mm Hg-1) than near FRC (28.8 ml . min-1 . mm Hg). Mean DLCO measured during slow exhalation near FRC (32.7 ml . min-1 . mm Hg) was significantly higher than DLCO measured during rebreathing over the same volume range. Measurements of Qc were not significantly different between the rebreathing and slow exhalation maneuvers. Differences in DLCO between the two methods at FRC were not due to differences in Qc.

Adult↗
PubMed1990

Gas mixing in dog lungs during high frequency ventilation studied by partial washout-single exhalation technique.

Gas mixing was studied in 10 anesthetized paralyzed dogs during high-frequency low tidal ventilation (HFV). After simultaneous washin of ethane (1%) and washout of resident argon (0.9%) the gas inflow was switched to atmospheric air for varied time intervals leading to varied levels of C2H6 washout and Ar washin. After the stop of HFV at predetermined test gas washout/washin levels, a constant-flow exhalation by a servo ventilator was performed and expirograms of C2H6 and Ar were recorded. Measurements were performed at varied ventilation frequencies (10-40 Hz), stroke volumes (20-40 ml), lung volumes (730-830 ml), expiratory flow rates (0.1-0.01 L/sec), breath-holding prior to exhalation (0-12 sec) and test gas washout levels achieved by varying the washout time (1 to 65 sec) before onset of exhalation. The expirograms showed a close to linearly rising alveolar plateau. They were analyzed for series dead space and alveolar slope which was normalized to the initial-to-final partial pressure difference. The normalized slopes of C2H6 washout and Ar washin were averaged, whereby the effect of shrinking lung volume due to continuing CO2/O2 exchange at low R was assumed to be suppressed. The slope was little affected by changes of stroke volume, decreased slightly with increasing frequency, and decreased considerably with breath-holding or increasing lung volume. As washout progressed, the alveolar slope first increased, attained a maximum at about half-washout and thereafter decreased. The finite values of the alveolar slope indicated that intrapulmonary gas mixing during HFV was incomplete. The slopes were larger than expected from diffusion calculations on symmetrically branching lung models. The behavior of the slope at varied washout levels suggested involvement of parallel ventilation/volume inhomogeneity coupled with sequential emptying.

Animals↗
PubMed1996

Evidence of nitric oxide in the exhaled gas of Asian elephants (Elephas maximus).

Nitric oxide (NO) produced in the respiratory tract is released into the respiratory gases of humans, rabbits, guinea-pigs, and rats. We analysed the NO concentrations in the exhaled gas of four awake Asian elephants. Two methods were employed: (1) exhaled gas was sampled from the elephants' trunks with a 1 L syringe and analysed for NO concentrations by chemiluminescence; (2) respiratory gas was continuously aspirated via a thin plastic tube positioned within the trunk and on-line analysed for NO concentrations by chemiluminescence. Syringe sampling (n = 4), when corrected for dilution by ambient air using linear regression analysis, revealed a mean NO concentration of 31 parts per billion (ppb); highest exhalatory concentrations measured during continuous suctioning were 27 and 28 ppb (n = 2). The exhaled NO concentrations in elephants are similar to those found in humans measured with a comparable technique. This supports the hypothesis that a size-independent 'normal value' of endogenous NO is provided in the airways which may contribute to regulation of pulmonary ventilation and perfusion by autoinhalation in some mammals.

Animals↗
PubMed1991

Simulating gas flow through the exhalation leg of a respirator's patient circuit.

The effectiveness of prescribed respiratory therapy is often dependent upon the choice of a respirator (ventilator) that excels for a particular mode of ventilation. The exhalation value of a ventilator is most often the key to a strong or weak performance. A computer model of the patient's gas flow through the expiratory circuit and exhalation valve is not only beneficial for design, but can also be used to study the optimum performance for a particular mechanical system. For this paper, the system that was used incorporated a linear voice coil actuator suspended by flat spider springs. The details of the modelling are given on a theoretical basis (with the appropriate equations), and the packaged simulation is described. Results are presented for simple computer algorithms with the intention of demonstrating the proper behaviour of the system. There are suggestions for further detailed studies to compare the linear voice coil model with other common exhalation valve mechanical designs, under various modes of ventilation.

Algorithms↗
PubMed1989

The effects of dose of elemental mercury and first-pass circulation time on exhalation and organ distribution of inorganic mercury in rats.

The lung plays a major role in the removal of dissolved elemental mercury (Hg0) from the bloodstream. During the first passage through the lung after an intravenous dose of Hg0 dissolved in aqueous buffer, from 10 to 17% was exhaled depending on the dose (0.11 or 1.1 micrograms Hg/rat) and the injection site (jugular versus tail vein). Furthermore, evidence is presented that subsequent exhalation over the next 50 s, before the rats were killed and the mercury determined in the lung at that time, was largely Hg0-extracted during the first pass. The total mercury extracted during the 60 s period was in the range of 40-49% of the dose. The oxidation of Hg0 to Hg2+ in red cells is important in limiting the availability of Hg0 to certain tissues. Thus, after a short residence time in blood (0.6 s after jugular vein injection), 12.9-17% is exhaled in the first pass as compared to 10.4-12.2% with a longer residence time (1.8 s after tail vein injection). Furthermore, there was a general tendency, even at 60 s after dosing, for certain tissues - lung, brain, and heart - to have higher values after dosing from the jugular vein. It was estimated that the half-time for oxidation was 3.3 s. Our results confirm previous observations that the form of inorganic mercury greatly influences the short-term deposition in certain tissues. Thus as compared to Hg2+, administration of Hg0 increases lung levels 5-10-fold; brain, 4-fold; and heart, 3-fold. Blood levels are lower after Hg0, particularly after the higher dose. Such findings are consistent with a model wherein Hg0 is in part oxidized by red blood cells, the remainder rapidly diffusing in tissues where it is also oxidized to Hg2+.

Animals↗
PubMed2005

Simultaneous determination of 222Rn and 220Rn exhalation rates from building materials used in Central Italy with accumulation chambers and a continuous solid state alpha detector: influence of particle size, humidity and precursors concentration.

A method to determine simultaneously the rates of 222Rn and 220Rn released from building materials quarried in Central Italy is presented. The method makes use of a continuous monitor equipped with a solid state alpha detector, in-line connected to a small accumulation chamber. The effects of chamber leakage and back diffusion on 222Rn free exhalation rate is evaluated. The influence of available exhalation surface, humidity content and precursors concentration on radon and thoron exhalation rates is investigated.

Journal Article↗
PubMed2005

Effect of maximal dynamic exercise on exhaled ethane and carbon monoxide levels in human, equine, and canine athletes.

Exercise-induced oxidative stress (EIOS) refers to a condition where the balance of free radical production and antioxidant systems is disturbed during exercise in favour of pro-oxidant free radicals. Breath ethane is a product of free radical-mediated oxidation of cell membrane lipids and is considered to be a reliable marker of oxidative stress. The heatshock protein, haem oxygenase, is induced by oxidative stress and degrades haemoglobin to bilirubin, with concurrent production of carbon monoxide (CO). The aim of this study was to investigate the effect of maximal exercise on exhaled ethane and CO in human, canine, and equine athletes. Human athletes (n = 8) performed a maximal exercise test on a treadmill, and canine (n = 12) and equine (n = 11) athletes exercised at gallop on a sand racetrack. Breath samples were taken at regular intervals during exercise in the human athletes, and immediately before and after exercise in the canine and equine athletes. Breath samples were stored in gas-impermeable bags for analysis of ethane by laser spectroscopy, and CO was measured directly using an electrochemical CO monitor. Maximal exercise was associated with significant increases in exhaled ethane in the human, equine, and canine athletes. Decreased concentrations of exhaled CO were detected after maximal exercise in the human athletes, but CO was rarely detectable in the canine and equine athletes. The ethane breath test allows non-invasive and real-time detection of oxidative stress, and this method will facilitate further investigation of the processes mediating EIOS in human and animal athletes.

Adult↗
PubMed2006

Breath alcohol concentration determined with a new analyzer using free exhalation predicts almost precisely the arterial blood alcohol concentration.

A new breath alcohol (ethanol) analyzer has been developed, which allows free exhalation, standardizes measured exhaled alcohol concentration to fully saturated water vapor at a body temperature of 37 degrees C (43.95 mg/L) and includes a built-in self-calibration system. We evaluated the performance of this instrument by comparing standardized alcohol concentration in freely expired breath (BrAC) with arterial (ABAC) and venous (VBAC) blood alcohol concentrations in fifteen healthy volunteers who drank 0.6 g of alcohol per kg body weight. The precision (coefficient of variation, CV) of the analyzer based on in vivo duplicate measurements in all phases of the alcohol metabolism was 1.7%. The ABAC/BrAC ratio was 2251+/-46 (mean+/-S.D.) in the post-absorptive phase and the mean bias between ABAC and BrAC x 2251 was 0.0035 g/L with 95% limits of agreement of 0.033 and -0.026. The ABAC and BrAC x 2251 were highly correlated (r=0.998, p<0.001) and the regression relationship was ABAC = 0.00045 + 1.0069 x (BrAC x 2251) indicating excellent agreement and no fixed or proportional bias. In the absorption phase, ABAC exceeded BrAC x 2251 by at most 0.04+/-0.03 g/L when tests were made at 10 min post-dosing (p<0.05). The VBAC/BrAC ratio never stabilized and varied continuously between 1834 and 3259. There was a proportional bias between VBAC and BrAC x 2251 (ABAC) in the post-absorptive phase (p<0.001). The pharmacokinetic analysis of the elimination rates of alcohol and times to zero BAC confirmed that BrAC x 2251 and ABAC agreed very well with each other, but not with VBAC (p<0.001). We conclude that this new breath analyzer using free exhalation has a high precision for in vivo testing. The BrAC reflects very accurately ABAC in the post-absorption phase and substantially well in the absorption phase and thereby reflects the concentration of alcohol reaching the brain. Our findings highlight the magnitude of arterio-venous differences in alcohol concentration and support the use of breath alcohol analyzers as a stand-alone test for medical and legal purposes.

Adult↗
PubMed2005

Radon exhalation of hardening concrete: monitoring cement hydration and prediction of radon concentration in construction site.

The unique properties of radon as a noble gas are used for monitoring cement hydration and microstructural transformations in cementitious system. It is found that the radon concentration curve for hydrating cement paste enclosed in the chamber increases from zero (more accurately - background) concentrations, similar to unhydrated cement. However, radon concentrations developed within 3 days in the test chamber containing cement paste were approximately 20 times higher than those of unhydrated cement. This fact proves the importance of microstructural transformations taking place in the process of cement hydration, in comparison with cement grain, which is a time-stable material. It is concluded that monitoring cement hydration by means of radon exhalation method makes it possible to distinguish between three main stages, which are readily seen in the time dependence of radon concentration: stage I (dormant period), stage II (setting and intensive microstructural transformations) and stage III (densification of the structure and drying). The information presented improves our understanding of the main physical mechanisms resulting in the characteristic behavior of radon exhalation in the course of cement hydration. The maximum value of radon exhalation rate observed, when cement sets, can reach 0.6 mBq kg(-1) s(-1) and sometimes exceeds 1.0 mBq kg(-1) s(-1). These values exceed significantly to those known before for cementitious materials. At the same time, the minimum ventilation rate accepted in the design practice (0.5 h(-1)), guarantees that the concentrations in most of the cases will not exceed the action level and that they are not of any radiological concern for construction workers employed in concreting in closed spaces.

Construction Materials↗