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PubMed1986

Effects of captopril on hemodynamics and blood gases in chronic obstructive lung disease with pulmonary hypertension.

The effects of Captopril, an angiotensin-converting enzyme inhibitor, on pulmonary hemodynamics and blood gases were studied in 9 patients with chronic obstructive lung disease (COLD) and pulmonary hypertension (PA-P greater than 20 mm Hg). Hemodynamic data were recorded prior to Captopril administration (50 mg per os) and for the next 60 min. Following Captopril administration, significant reductions in mean pulmonary artery pressure (PA-P) (p less than 0.05), in mean pulmonary wedge pressure (PW-P) (p less than 0.05), and in total pulmonary resistance (TPR) were noted; significant reductions in mean brachial artery pressure (BA-P) and systemic vascular resistance (SVR) were also recorded, while cardiac output, heart rate and blood gas tensions showed no significant changes. Furthermore, the higher the hypoxemia, the greater was the reduction in BA-P (p less than 0.05). We therefore feel that Captopril, when administered to COLD patients with pulmonary hypertension, may protect the pulmonary circulation from hypoxic pulmonary vasoconstriction.

Adult↗
PubMed1987

Respiratory gases, acid-base balance and lactate concentrations of the midterm human fetus.

Respiratory gases, acid-base balance, and lactate and hemoglobin concentrations were measured in 14 fetal blood samples between 17 and 21 weeks of gestation. The samples were obtained at the time of fetoscopy performed for prenatal diagnosis. Results have been compared with two reference groups: (a) 4 patients in whom fetal cord blood sampling was performed at 32-36 weeks of gestation, and (b) 10 patients at the time of elective cesarean section, 35-39 weeks. PO2 and oxygen saturations were significantly higher and hemoglobin concentration lower in the mid-gestation fetus. Acid-base balance was not significantly different. There was a significant correlation between maternal and fetal hemoglobin concentrations. The oxygen affinity of fetal blood was not significantly different from that described for term fetuses with a oxygen saturation of less than 90%.

Acid-Base Equilibrium↗
PubMed1995

Profile of alveolar gases during periodic and regular breathing in preterm infants.

To determine the changes in alveolar PCO2 (PACO2) and PO2 (PAO2) during periodic and regular breathing epochs in the same infants, we studied 11 preterm infants during quiet sleep (birth weight 1,630 +/- 94 g; gestational age 31 +/- 1 weeks; postnatal age 32 +/- 3 days). A total of 94 breathing/apneic cycles were analyzed and compared with regular periods. During periodic and regular breathing epochs, there were negative correlations of PAO2 on PACO2. Short (< or = 5 s) and long (> 5 s) apneas for individual infants occurred along the regression line for that infant. There was not a single overall critical PACO2 below which apnea occurred, but for individual infants the PACO2 and the PAO2 of the breath preceding apnea varied within a limited range. Apneas occurred in clusters of PACO2 and PAO2 along the average regression line of PAO2 on PACO2. Analysis of the data showed that apnea occurred at the lowest PACO2 and highest PAO2 levels if allowance was made for circulation time. During apnea, 'the best fit' for the increase in PACO2 and the decrease in PAO2 was linear, rather than logarithmic. The findings suggest the following. (1) There is not a single overall critical level of PACO2 for apnea to occur, but in a given infant this level varies within a limited range. This indicates that these infants are likely breathing near the apnea threshold. (2) Short and long apneas appear to occur randomly along the regression of PAO2 on PACO2 for a particular infant. (3) The changes in alveolar gases are linear during apnea.(ABSTRACT TRUNCATED AT 250 WORDS)

Apnea↗
PubMed1996

Cord lactate, pH, and blood gases from healthy neonates.

Lactate, pH, pO2, and pCO2 were determined in arterial, venous, and free-flowing mixed umbilical cord blood obtained from deliveries of apparently healthy neonates. The goals of this study were to establish reference ranges for lactate and pH against which results in cases of high-risk labor and delivery could be compared, to see how the gases correlated with these values, and to determine whether easily accessible mixed umbilical cord blood can serve as the sample in lieu of cord arterial or cord venous blood. Arterial and venous cord lactates were 2.98 mmol/l (+/- 1.40) and 2.80 mmol/l (+/- 1.35), respectively, from 85 cords obtained from vaginal and cesarean deliveries. Mixed cord blood lactate, obtained on 48 cords, was 2.72 mmol/l (+/- 1.28) versus 3.14 and 2.97 mmol/l for the arterial and venous samples from those cords, respectively, and correlated quite well with lactate from the venous specimens (r = 0.97). Differences of > 0.5 mmol/l occurred between mixed and arterial cord bloods in 21 patients, and between mixed and venous cord bloods in 6 of the 48 patients, respectively. We conclude that (1) less than 2.5% of deliveries of apparently healthy neonates have arterial, venous, or mixed cord lactates > or = 7.0 mmol/l and pH < or = 7.15, (2) neither cord venous pO2 nor pCO2 correlate well with cord venous lactate, and (3) readily available mixed cord blood is a satisfactory specimen for the measurement of venous cord latate.

Carbon Dioxide↗
PubMed1995

Should mechanical ventilation be optimized to blood gases, lung mechanics, or thoracic CT scan?

This study was aimed at providing data for optimization of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). The effects of ventilation with positive end-expiratory pressure (PEEP) titrated to blood gases were studied by thoracic computed tomographic (CT) scans and lung mechanics measurements in eight patients. CT density histograms at end-expiration were used to investigate the effects of PEEP on three differently aerated zones. Static pressure-volume (P-V) curves were used to determine the deflection point above which baro-volotrauma (a combination of barotrauma and volotrauma) may occur. Peak pressures, plateau pressures, and lung volumes measured by Respitrace were compared with the deflection point. CT scan showed that PEEP increased "normally aerated" areas, decreased "nonaerated" areas, and did not change "poorly aerated" zones. No correlations were found between CT scan and either PaO2 or mechanical data. Pressure at the deflection point was lower than the usually recommended 35 to 40 cm H2O for peak pressure in four patients (range, 28 to 32 cm H2O). With regard to plateau pressures, only one patient was ventilated above the deflection point. However, monitoring of volumes showed that these four patients had an end-inspiratory volume above this point. We conclude that mechanical ventilation may be initially adjusted on the basis of blood gas values and then optimized on the basis of lung mechanics to limit the risk of baro-volotrauma.

Adolescent↗
PubMed1998

Lung volume reduction surgery has variable effects on blood gases in patients with emphysema.

Most studies of bilateral lung volume reduction surgery (LVRS) report increases in arterial oxygenation (PaO2). Some suggest this results from an increased alveolar ventilation, but others imply that ventilation-perfusion heterogeneity is reduced. We measured arterial blood gases (ABGs) on air before and 3 mo following LVRS in 46 patients (61% of eligible patients), estimate the difference between alveolar and arterial O2 (AaPO2), and correlated the changes observed with preoperative ABGs, and with pre-and postoperative pulmonary function. The mean +/- SD change in PaO2 and AaPO2 was +3 +/- 10 mm Hg (p = 0.058) and +1 +/- 11 mm Hg (p = NS), respectively, and the range of change was large (-17 to +29 mm Hg and -24 to +23 mm Hg, respectively). The mean change in PaCO2 was -3 +/- 5 mm Hg (p < 0.05) and ranged from -11 to +5 mm Hg. Changes in PaO2 and AaPO2 were poorly correlated with changes in PaCO2 or with pre- or postoperative pulmonary function. Although some patients had a marked improvement in ABGs following LVRS, almost as many deteriorated. On average, only minimal effects were seen. Although mean alveolar ventilation improved somewhat, the effect of LVRS on PaO2 primarily resulted from alterations in ventilation-perfusion heterogeneity.

Aged↗
PubMed1999

Effects of salmeterol on arterial blood gases in patients with stable chronic obstructive pulmonary disease. Comparison with albuterol and ipratropium.

Administration of beta-adrenergic agonist bronchodilators to patients with airways obstruction commonly results in transient decreases in Pa(O(2)) levels despite bronchodilation, an effect that has been attributed to these drugs' pulmonary vasodilator action. We compared the acute effects on gas exchange of salmeterol with those of albuterol and the anticholinergic agent ipratropium in 20 patients with stable chronic obstructive pulmonary disease (COPD). Each agent was given in recommended dosage on separate days in a double-blind, crossover format, and the patients' arterial blood gases (ABGs) were measured at baseline and at intervals to 120 min. Small but statistically significant declines in Pa(O(2)), the primary outcome variable, were found after administration of both salmeterol and albuterol. The decline in PaO2 after salmeterol was of lesser magnitude but was more prolonged than that after albuterol, the greatest mean change being -2.74 +/- 0.89 mm Hg (mean +/- SEM) at 30 min after salmeterol, and -3.45 +/- 0.92 mm Hg at 20 min after albuterol. Following ipratropium, the corresponding change was -1.32 +/- 0.85 mm Hg at 20 min. These declines, which were almost entirely attributable to increases in the alveolar-arterial difference in oxygen tension Delta(A-a)DO2 tended to be more marked in subjects with higher baseline PaO2 values. No subject experienced a decline in PaO2 to levels below 59 mm Hg. There were no significant differences among the three drugs studied. We conclude that despite small decreases in PaO2 after each of the three drugs, the declines were small transient, and of doubtful clinical significance.

Administration, Inhalation↗
PubMed1987

Effects of an anticholinergic bronchodilator on arterial blood gases of hypoxemic patients with chronic obstructive pulmonary disease. Comparison with a beta-adrenergic agent.

Adrenergic bronchodilators have the potential drawback that they may increase hypoxemia in spite of relieving air-flow obstruction in patients with asthma. Anticholinergic bronchodilators are of interest as alternatives to beta-adrenergic agents, particularly in patients with chronic bronchitis and emphysema, yet little is known of the effects of either class of agent on gas exchange in patients with this diagnosis. We compared their effects on gas exchange in 12 patients with chronic bronchitis and emphysema who also had arterial hypoxemia in a double-blind crossover study. We found that nebulized atropine methonitrate, a quaternary ammonium anticholinergic bronchodilator, resulted in only minor and statistically insignificant effects on gas exchange at all times for as long as 60 min after its inhalation. In contrast, the beta-adrenergic bronchodilator metaproterenol hydrochloride resulted in a statistically significant decrease in the PaO2, the greatest mean decrease being 5.0 +/- 2.5 mm Hg (mean +/- 1 SD). The effects of metaproterenol on arterial blood gases in this population of patients were more prolonged than those previously reported in asthmatic subjects with lesser degrees of hypoxemia. An anticholinergic bronchodilator might be preferable in patients with hypoxemia caused by chronic bronchitis and emphysema in that it does not carry the risk of worsening systemic hypoxemia.

Aged↗
PubMed1980

Effects of the administration of O2 on ventilation and blood gases in patients with chronic obstructive pulmonary disease during acute respiratory failure.

The effects of the administration of 100% oxygen on minute ventilation (VE) and arterial blood gases were studied in patients with chronic obstructive pulmonary disease during acute respiratory failure. The administration of O2 resulted in an early decrease in VE, which averaged 18% +/- 2 SE of the control VE, and was due to a decrease in both tidal volume (VT) and respiratory frequency (f). This was followed by a slow increase in VE, such that after 15 min of breathing O2, VE rose to 93 +/- 6% of the control room air value, with both VT and f similar to control values. Despite the small difference between VE while breathing room air and that at the fifteenth minute of O2 inhalation, PaCO2 increased by 23 +/- 5 mmHg, and no significant correlation was found between the changes in VE and PaCO2. By the fifteenth minute of O2 inhalation the PaO2 averaged 225 +/- 23 mmHg, and it was concluded that despite the removal of the hypoxic stimulus of O2 inhalation, the activity of the respiratory muscles remained great enough to maintain VE at nearly the same degree as that while breathing room air. Consequently, the changes in PaCO2 after the administration of O2 were mainly due to increased inhomogeneity of VA/Q distribution within the lungs.

Aged↗
PubMed1982

Effects of airway anesthesia on pattern of breathing and blood gases in patients with chronic obstructive pulmonary disease during acute respiratory failure.

To assess the role played by airway receptors in the genesis of rapid and shallow breathing of patients with chronic obstructive pulmonary disease (COPD), we studied the effects of airway anesthesia in 14 patients with COPD during acute respiratory failure. Airway anesthesia was performed by fiberoptic xylocaine administration from the larynx to the subsegmental bronchi, all patients being intubated or tracheostomized. A small decrease in minute ventilation of 6 +/- 1% of the control values occurred after airway anesthesia. This was due to a decrease (p less than 0.01) in respiratory frequency (f) (14.5 +/- 1%). The latter resulted from an increase (p less than 0.0005) in the expiratory time, whereas the inspiratory time did not change significantly. On the other hand, tidal volume increased (p less than 0.02) by 10.1 +/- 0.6%. In all patients, these modifications were accompanied by arterial blood gas deterioration, mean PaO2 and PaCO2 of 42 +/- 3 mmHg and 62 +/- 3 mmHg, respectively, 15 min after xylocaine administration, as compared with 48 +/- 2 mmHg and 54 +/- 2 mmHg, respectively, during the control period. No correlation was found between the changes in minute ventilation and PaO2 or PaCO2. We conclude that (1) activation of airway receptors are involved in the determination of the rapid and shallow breathing observed in patients with COPD during acute respiratory failure, and (2) airway xylocaine anesthesia that worsens arterial blood gases is contraindicated in these patients.

Aged↗
PubMed1986

Effect of flow rate on blood gases during constant flow ventilation in dogs.

We studied the effect of flow rate (V) on arterial blood gases during constant flow ventilation (CFV) in 9 anesthetized, paralyzed dogs weighing 9.5 to 26.5 kg. The constant flow was administered through catheters placed in each mainstem bronchus. Alveolar ventilation increased linearly with increasing V over the range of 0.18 to 1.0 L/s but was relatively constant at flows above 1.0 L/s. We found that CFV produced normocapnia at a mean V of 0.48 +/- 0.21 L/s (mean +/- SD). However, we did not find any significant relationship between body weight and the V required for normocapnia. At all flow rates we found a relatively large alveolar to arterial oxygen difference (48.9 +/- 8.8 mmHg, mean +/- SD), suggesting significant inhomogeneities in ventilation-perfusion. Our data are consistent with a 2-zone model of gas exchange where gas exchange is dominated by bidirectional convective streaming in the airways closest to the jets, cardiogenic induced flows in the most peripheral airways, and jet-induced turbulence in those airways between these 2 regions.

Animals↗
PubMed2004

Computational fluid dynamics simulation of laser-ablated carbon plume propagation in varying background gases for single-walled nanotube synthesis.

A computational fluid dynamics study was conducted to model the plume resulting from the laser ablation of a carbon target in a laser ablation oven for the production of carbon single-walled nanotubes (SWNTs). The goal is to gain understanding into the fluid dynamics and thermodynamics of the plume to ultimately improve SWNT production techniques. The simulations were carried out with a 12-species, 14-reaction chemistry model that included carbon species from C to C6. Metal catalysts in the carbon target were ignored for these simulations. Simulation times ranged from immediate ablation onset to 8 ms past the initial onset of ablation. A secondary goal of the study was to compare computational results with experimental results for three different background gases in the laser ablation oven-argon, helium, and nitrogen. Computational results indicated that lighter carbon species were more quickly diffused into the background gas for helium and nitrogen, resulting in lower localized mass fractions of carbon nanotube "feedstock." The expectation is that this effect will reduce the production of carbon nanotubes, which has been confirmed by experimental evidence. From this investigation, a possible "indicator species" for the production of SWNT appears to be C5.

Argon↗
PubMedDate not supplied

Effect of anesthetic gases on middle ear pressure in the presence of effusion.

Halothane, randomly with or without nitrous oxide (N2O), was administered by face mask to 69 children (selected by tympanometric and otoscopic evidence of chronic otitis media with effusion) for pressure equalization (PE) tube insertion in one or both ears. Tympanograms were obtained from 127 ears prior to and soon after the induction of a satisfactory level of anesthesia. The effect of anesthesia was identical whether N2O was used or not: 85% (75/88) of ears with flat tympanograms (B) remained B (all contained fluid); 15% (13/88) became peaked and 62% (8/13) of those contained fluid. All but two ears with peaked tympanograms showed substantial increases in middle ear pressure (mean: 179 mm H2O, range: -70 to +550 mm H2O) regardless of the presence of fluid. We conclude the N2O is not responsible for aerating the middle ear in the usual surgical setting, and that assisted ventilation used in mask inhalation anesthetic techniques will inflate all normal middle ears, most ears with a peaked tympanogram regardless of fluid, and 15% of ears with a nonpeaked tympanogram. It is unlikely that inhalation of anesthetic gases is responsible for displacement of middle ear fluid down the eustachian tube within the time constraints of the usual operating room setting.

Anesthesia, Inhalation↗
PubMed1980

Simultaneous analysis of respiratory gases and nitrous oxide in dental patients.

The simultaneous analysis of respiratory gases in the presence of nitrous oxide is described. The modified gas chromatographic technique used is especially applicable to dental situations where continuous monitoring is not necessary. It employs readily available equipment and does not involve interference with other dental procedures.

Anesthesia, Dental↗
PubMed2000

Quantitative analysis of trace gases of breath during exercise using the new SIFT-MS technique.

We show how the concentration of the breath gases ammonia, acetone, and isoprene vary with time during exercise using the new selected ion flow tube mass spectrometry (SIFT-MS) technique. The expired breath concentrations of ammonia, acetone and isoprene were observed within the range of 50-500, 100-1400 and 5-400 ppb, respectively. Increasing acetone levels were observed for most subjects during the exercise period. However, isoprene levels decreased with time during exercise. Older subjects showed higher levels of isoprene compared with younger subjects. The ammonia time profile with exercise showed both decreasing and increasing patterns for different subjects.

Acetone↗
PubMed2002

Effect of hypobaric hypoxia on blood gases in patients with restrictive lung disease.

Several publications have reported effects of hypobaric conditions in patients with chronic obstructive pulmonary disease. To the current authors' knowledge, similar studies concerning patients with restrictive lung disease have not been published. The effect of simulated air travel in a hypobaric chamber on arterial blood gases, blood pressure, and cardiac frequency during rest and 20 W exercise, and the response to supplementary oxygen in 17 patients with chronic restrictive ventilatory impairment has been investigated. Resting oxygen tension in arterial blood (Pa,O2) decreased from 10.4+/-1.6 kPa at sea level to 6.5+/-1.1 kPa at 2,438 m simulated altitude, and decreased further during light exercise in all patients (5.1+/-0.9 kPa). Pa,O2 at this altitude correlated positively with sea-level Pa,O2 and transfer factor of the lung for carbon monoxide (TL,CO), and negatively with carbon dioxide tension in arterial blood (Pa,CO2). Pa,O2 increased to acceptable levels with an O2 supply of 2 L x min(-1) at rest and 4 L x min(-1) during 20 W exercise. In conclusion, most of the patients with restrictive ventilatory impairment developed hypoxaemia below the recommended levels of in-flight oxygen tension in arterial blood during simulated air travel. Light exercise aggravated the hypoxaemia. Acceptable levels of oxygen tension in arterial blood, with only a minor increase in carbon dioxide tension in arterial blood, were obtained by supplementary oxygen.

Adult↗
PubMed2006

Incidence of asthma among workers exposed to sulphur dioxide and other irritant gases.

The aim of the present study was to investigate whether repeated peak exposure (gassings) to sulphur dioxide (SO2) and other irritant gases increases the risk of new-onset asthma. A questionnaire was sent to 4,112 sulphite workers, of whom 1,919 completed the questionnaire and 396 completed the short-form questionnaire, which was sent out as a last reminder. A sample of 130 nonrespondents completed a telephone interview using the short-form questionnaire. The incidence of adult-onset, physician-diagnosed asthma during employment duration was analysed in relation to exposure to SO2 and gassings giving rise to respiratory symptoms. Incidence rates, as well as incidence rate ratios with 95% confidence interval (CI), were calculated. Further Cox regression models were used allowing assessment of hazard ratios (HR) stratified for sex and adjusted for atopy, smoking habits and age. The incidence rate for asthma among sulphite mill workers reporting gassings of SO2 was 6.2 out of 1,000 person-yrs, compared with 1.9 out of 1,000 person-yrs among subjects unexposed to SO2 and any gassings (HR (95% CI) 4.0 (2.1-7.7)). Among males reporting gassings to SO2, the HR (95% CI) for asthma was 5.8 (2.6-13) compared with unexposed males. In conclusion, repeated peak exposure to sulphur dioxide increased the incidence of asthma during work in sulphite pulp mills, which supports the hypothesis of irritant-induced asthma.

Adolescent↗