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PubMed1997

[The value of capnography and exhaled CO2 in neonatal intensive care units].

OBJECTIVE: The objective of this study was to investigate the reliability of end-tidal CO2 (PetCO2) as a non-invasive guide of PaCO2 in the newborn and to analyze the influence of the relationship between ventilation-perfusion in the correlation between both determinations. PATIENTS AND METHODS: End-tidal CO2 (PetCO2) was monitored by capnography in 9 ventilated newborns: 146 arterial blood gas samples were drawn and the results were compared with the PetCO2 values obtained. The gradient or difference between PaCO2 and PetCO2 was calculated to determine the correlation. The ratio a/AO2 was used as an indirect indicator of the ventilation/perfusion relationship (V/Q ratio). RESULTS: The mean gestational age was 30.9 +/- 2.8 weeks and birth weight 1,648 +/- 596 g. The age at the beginning of the study was 2 +/- 1.5 days. The diagnoses corresponded to 5 cases of RDS (56%), 2 cases of wet lung syndrome (22%), 1 case of pneumonia (11%) and 1 pneumothorax (11%). The results of this monitoring were classified in function of the a/AO2 ratio obtained: Group A, a/AO2 < 0.2 and PaCO2-PetCO2 gradient = 13.3 +/- 5; Group B, a/AO2 = 0.2-0.29 and PaCO2-PetCO2 gradient = 8 +/- 2.7; and Group C, a/AO2 > 0.29 and PaCO2-PetCO2 gradient = 2 +/- 1.7. The results show a very good correlation from a a/AO2 ratio > or = 0.3 onwards. The a/AO2 ratio is the major determinant of PaCO2-PetCO2 differences and respiratory frequency has less influence. CONCLUSIONS: 1) Monitoring of end-tidal CO2 does not maintain a good correlation with PaCO2 in serious lung illness. 2) End-tidal CO2 measurement is an effective and accurate technique for the monitoring of newborns when the a/AO2 ratio > or = 0.3 and it can be useful for weaning of mechanical ventilation. 3) PaCO2-PetCO2 differences accurately show the changes in the ventilation-perfusion relationship.

Blood Gas Analysis↗
PubMed1976

[Clinical and experimental grounds for the method of spontaneous respiration with difficult exhalation (lung inflation) in children].

Three methods of inducing difficulty in breathing out in spontaneous ventilation are described: by means of a valve attached to an intubation tube (I), with a polyethylene sac secured hermetically on patient's head and connected to a source of oxygen (2), and also with the help of a low-pressure chamber for patient's body (3). Experiments and clinical observations (40 therapeutic seances in 23 children aged from 1 day to 7 years) have evidenced that this method is mostly more advantageous than artificial ventilation, it is highly efficient in treatment of aspiration pneumonia and pulmonary edema, also it may be used with prophylactic purposes following aspiration, artificial ventilation, in the immediate postoperative period, and after hyperbaric oxygenation.

Animals↗
PubMed1976

[14CO2 exhalation tests. Diagnostic improvement in gastroenterologic diseases].

For evaluation of 14CO2-breath-tests the three most employed tests, namely glycero-14C-tripalmitate-test, 14C-lactose-tolerance-test, and 14C-glycin-cholate-test, were performed in healthy volunteers (n = 69), patients with chronic pancreatitis (n = 18), manifest malassimilation (n = 8), lactase deficiency (n = 15), and patients, in whom a disturbed enterohepatic bile salt circulation was suspected (n = 19). Usefulness of malabsorption tests was limited by many false normal results. Cholylglycin-breath-test on the other hand was sensitive, but clinical significance remained questionable. In our opinion simple performance and lacking discomfort are no sufficient arguments for 14CO2-breath-test.

Carbon Dioxide↗
PubMedDate not supplied

Waiting to exhale.

Explore the source record for details and available documents.

Activities of Daily Living↗
PubMed2003

Nitric oxide in allergic airway inflammation.

PURPOSE OF REVIEW: Exhaled nitric oxide has been proposed as a useful noninvasive marker of airway inflammation in asthma. Great efforts have been made to standardize the methodology for exhaled nitric oxide measurement in both children and adults. As a consequence there is now an opportunity to establish the precise relationship between exhaled nitric oxide, atopy and airway inflammation, and to investigate whether or not there is a role for the measurement of exhaled nitric oxide in the management of patients with asthma. RECENT FINDINGS: A number of recent studies have investigated the relationship between exhaled nitric oxide and airway inflammation in asthma measured directly, using sputum induction, bronchoalveolar lavage and endobronchial biopsy. These measurements suggest that exhaled nitric oxide reflects eosinophilic airway inflammation in asthma, although there is no evidence for any relationship between exhaled nitric oxide and other airway inflammatory cells. Exhaled nitric oxide levels were found to be higher in atopic compared with nonatopic groups. These levels, however, are further elevated in atopic patients with asthma, suggesting that exhaled nitric oxide is not simply a marker of atopy. Although there is little evidence to support the routine use of measurement of exhaled nitric oxide in the management of patients with asthma, it may prove to be useful in assessing adherence to treatment with inhaled corticosteroids, or in the identification of patients in whom respiratory symptoms are associated with eosinophilic airway inflammation. SUMMARY: There is good evidence that exhaled nitric oxide reflects eosinophilic airway inflammation in asthma. Well designed, long-term studies are needed to evaluate whether the addition of exhaled nitric oxide measurements to clinical and lung function assessment results in improved asthma control.

Asthma↗
PubMed1983

Dynamic measurements of CO diffusing capacity using discrete samples of alveolar gas.

It has been shown that measurements of the diffusing capacity of the lung for CO made during a slow exhalation [DLCO(exhaled)] yield information about the distribution of the diffusing capacity in the lung that is not available from the commonly measured single-breath diffusing capacity [DLCO(SB)]. Current techniques of measuring DLCO(exhaled) require the use of a rapid-responding (less than 240 ms, 10-90%) CO meter to measure the CO concentration in the exhaled gas continuously during exhalation. DLCO(exhaled) is then calculated using two sample points in the CO signal. Because DLCO(exhaled) calculations are highly affected by small amounts of noise in the CO signal, filtering techniques have been used to reduce noise. However, these techniques reduce the response time of the system and may introduce other errors into the signal. We have developed an alternate technique in which DLCO(exhaled) can be calculated using the concentration of CO in large discrete samples of the exhaled gas, thus eliminating the requirement of a rapid response time in the CO analyzer. We show theoretically that this method is as accurate as other DLCO(exhaled) methods but is less affected by noise. These findings are verified in comparisons of the discrete-sample method of calculating DLCO(exhaled) to point-sample methods in normal subjects, patients with emphysema, and patients with asthma.

Adult↗
PubMed1995

CO2 rebreathing during BiPAP ventilatory assistance.

BiPAP ventilatory assistance can increase minute ventilation and reduce respiratory effort, but does not always reduce PaCO2. We studied the effects of BiPAP ventilatory assistance on PaCO2 and examined specific mechanisms whereby BiPAP ventilatory assistance may not lower PaCO2. BiPAP ventilatory assistance using a non-rebreather valve and volume cycled ventilation at similar settings produced significantly lower PaCO2 than BiPAP ventilatory assistance using a standard exhalation device. The failure of PaCO2 to fall with the standard exhalation device was due to exhalation past the exhalation device into the ventilator tubing, subsequent rebreathing of the exhaled gases, and an increase in dead space ventilation. Use of other fixed-resistance exhalation devices also resulted in exhalation back into the ventilator tubing. Use of a new plateau exhalation device or a non-rebreather valve eliminated CO2 rebreathing and its effect on dead space ventilation. Changing exhalation devices had no significant effect on BiPAP pressure generation or sensing capabilities. Our results indicate that the use of a standard exhalation device during BiPAP ventilatory assistance causes CO2 rebreathing, which can blunt any effect of BiPAP on PaCO2. Use of an appropriate alternative exhalation device can eliminate this problem.

Carbon Dioxide↗
PubMedDate not supplied

[Breath condensate--a medium obtained by a noninvasive method for the detection of inflammation mediators of the lung].

Collection of exhaled condensate (freezing of expired air under conditions of spontaneous breathing) is a non-invasive method permitting the collection of material originating from the lung and the lower respiratory tract so that it can be used for diagnostic examinations. In order to be able to evaluate the diagnostic evidence of exhaled condensate samples in cases of respiratory disease of the calf, leukotriene B4 (LTB4) in bovine exhaled condensate was determined. The influence of the breathing pattern and body temperature on the quantity of condensate to be collected was tested in a total of 49 exhaled condensate samples. It became obvious that the exhaled condensate quantity obtained per time unit is dependent on the ventilation volume per time unit (minute volume). In exhaled condensate samples from 35 clinically healthy calves, LTB4 concentrations of less than 250 pg/mL exhaled condensate were detected. A total of 14 exhaled condensate samples from 7 calves was analyzed before and after experimental respiratory infection with Pasteurella multocida D. In parallel to the analysis of LTB4 in exhaled condensate, the lung function of the calves was examined by means of impulse oscilloresistometry. The increase of LTB4 in the exhaled condensate post infection correlated significantly (p < or = 0.05) with decreases of respiratory reactance. The determination of LTB4 concentrations in exhaled condensate seems to be suitable, in principle, for the detection of inflammations in the respiratory system of the calf. Further studies are needed for the evaluation of the diagnostic validity of the method.

Animals↗
PubMedDate not supplied

A kinetic evaluation of 14CO2 in expired air after 14C-methacetin administration in rats, used for the in vivo study of the metabolism of drugs.

The pharmacokinetics of the blood level and the patterns of 14CO2 exhalation were determined simultaneously following i.v. administration of 14C-methacetin to the conscious rat. The pattern of exhalation of 14CO2 did not parallel the biexponential decline of radioactivity in the blood and a delay of 30-40 min preceded the maximal rate of 14CO2 exhalation. The total radioactivity exhaled remained constant at 56 +/- 4.5% (SD) of the applied dose throughout a tenfold dose range of methacetin (0.6, 4.0 and 6.0 mg/kg i.p.), administered to groups of three rats each and measured over a period of 4 hours. The pattern of radiolabel exhalation was biexponential with the low dose, linear with the medium dose and convex with the high dose. Although the total fraction of the label expired after 4 hours remained constant, the rates of exhalation at the higher dosages exhibited saturation type kinetics. At the higher dosage, since the pattern of 14CO2 exhalation did not accurately reflect the decline of methacetin seen in blood, one of the steps occurring between the demethylation process and the production of expired CO2 appears to be rate limiting. Significant increases in the amount of 14CO2 exhaled within 1 hour were obtained by pretreatment with phenobarbital, rifampicin and 3-methylcholanthrene. Again the proportion of radiolabel expired in 4 hours remained constant. Acute hepatic injury produced by pretreatment with graded doses of carbon tetrachloride resulted in graded reductions in the amount of 14CO2 exhaled in the first hour, although the total amount exhaled during the 4 hour collection period did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetamides↗
PubMed2005

End-expiratory carbon monoxide levels in healthy subjects living in a densely populated urban environment.

Carbon monoxide (CO) has a high affinity for haemoglobin and is a common cause of poisoning in industry and the home. Exhaled CO levels in patients with respiratory disease have been reported but exhaled CO in a large cohort of healthy subjects grouped by age and gender has not been reported. Exhaled CO levels and spirometry lung function data were recorded from 1032 subjects at a university campus and two commercial plazas. Subjects were also asked to complete a respiratory symptom questionnaire. Ninety-eight subjects reported respiratory disease and were excluded from the study. Non-smoking male subjects (n=508) had higher exhaled CO levels (4.36+/-2.54 ppm) [range 0-21 ppm] compared with female (n=348) subjects (3.72+/-2.12 ppm) [range 0-14 ppm] (p<0.0005), and older subjects (>60 years) had lower exhaled CO levels compared with young subjects (<22 years) (p=0.018). Over 13% of non-smokers had an exhaled CO greater than 7 ppm. Smokers showed significantly higher exhaled CO levels compared with non-smokers (p<0.0005) and smokers who complained of frequent cough and sputum production had higher levels of exhaled CO compared with smokers without such complaints. Smoking history (pack-years) was directly related to age (r=0.59) but correlated inversely with forced expiratory flow in the 1st second (FEV1) (r=-0.29) and peak expiratory flow rate (PEFR) (r=-0.25) (p<0.05). If a city's micro environmental CO concentrations and human activity patterns is available, regular monitoring of exhaled CO in healthy subjects has the potential to be used as a functional index of air pollution.

Adult↗
PubMed1999

Beta-adrenoceptor agonist stimulation of pulmonary nitric oxide production in the rabbit.

Nitric oxide (NO) is continuously produced in the lung and is present in exhaled air. We examined the effect of beta-adrenoceptor stimulation on the production of pulmonary NO in rabbits. Exhaled NO was measured by chemiluminescence in anaesthetized and mechanically ventilated rabbits and in buffer-perfused rabbit lungs. Intravenous infusions of adrenaline (0.1-10 microg kg(-1) min(-1)) elicited dose-dependent increases in exhaled NO. The increases in exhaled NO comprised an initial peak followed by a lower plateau level. The increase in exhaled NO was inhibited by propranolol (1 mg kg(-1)) but not by phentolamine (1 mg kg(-1)). Prenalterol, a beta1-adrenoceptor agonist, and terbutaline, a beta2-adrenoceptor agonist, also caused dose-dependent increases in exhaled NO. However, prenalterol was >100 times more potent than terbutaline. Infusions of forskolin (0.01-0.03 micromol kg(-1) min(-1)), an adenylate cyclase stimulator, elicited dose-dependent decreases in blood pressure and concomitant increases in heart rate but caused no alterations in exhaled NO. Nimodipine, a L-type calcium channel blocker, antagonized the increases in exhaled NO in response to prenalterol infusions. The increases in exhaled NO in response to adrenaline and prenalterol were also present in blood-free, buffer perfused lungs during constant-flow conditions. These results demonstrate that pulmonary nitric oxide production can be enhanced by beta-adrenoceptor stimulation. Furthermore, the results indicate that the beta-adrenergic stimulation of pulmonary NO production is not critically dependent on cyclic AMP formation but may require intact calcium-channels.

Adrenergic beta-Agonists↗
PubMed1980

Hysteresis in the relation between diffusing capacity of the lung and lung volume.

The diffusing capacity of the lung for carbon monoxide (DLCO) varies directly with lung volume (VA) when measured during a breath-holding interval. DLCO measured during a slow exhalation from total lung capacity (TLC) to functional residual capacity (FRC) does not vary as VA changes. Since VA is reached by inhaling during breath holding and by exhaling during the slow exhalation maneuver, we hypothesized that the variability in the relation between DLCO and VA was due to hysteresis. To test this hypothesis, breath-holding measurements of DLCO were made at three lung volumes, both when VA was reached by inhaling from residual volume (RV) and when Va was reached by exhaling from TLC. At 72% TLC, DLCO was 22% higher when VA was reached by exhalation compared to inhalation (P < 0.02). At 52% TLC, DLCO was 19% higher when VA was reached by exhalation compared to exhalation (P < 0.005). DCLO measured during a slow exhalation fell on the exhalation limb of the CLCO/VA curve. these data indicate that there is hysteresis in DLCO with respect to lung volume.

Adult↗