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PubMed1983

Capnography for detection of accidental oesophageal intubation.

The clinical diagnostic signs for detecting inadvertent oesophageal intubation may all be misleading. We therefore tested the practice of recording exhaled carbon dioxide during the intubation procedure as an additional measure for detection of accidental oesophageal intubation. Twenty patients were intubated simultaneously into the trachea and oesophagus and the carbon dioxide concentration was continuously recorded from both sources. Manual ventilation of the lungs always resulted in a typical CO2 curve pattern. Ventilation by mask prior to the intubation obviously resulted in some filling the stomach by exhaled gas in 9 of the 20 patients. In these cases some CO2 could be detected during oesophageal ventilation. As the oesophageal CO2 concentrations were very low initially, compared to the tracheal recordings, and carbon dioxide completely disappeared after a few ventilations into the oesophagus, distinguishing between the tracheal and oesophageal capnography tracings was easy.

Carbon Dioxide↗
PubMed1989

Early detection of inadvertent oesophageal intubation: pulse oximetry vs. capnography.

The aim of our retrospective study was to evaluate the efficacy of routine pulse oximetry and capnometry for detection of oesophageal tube misplacement. Patients undergoing ENT interventions at our hospital are routinely monitored by ECG, arterial blood pressure by cuff, capnography, and pulse oximetry. Beat-to-beat values of Sao2 and CO2 waveform were recorded by a graphic printer connected to a microcomputer, ASA I patients were routinely preventilated with FIO2 = 0.3, and ASA II-III patients with FIO2 = 1.0. Anaesthesia was performed by junior anaesthesiologists under the close supervision of a resident. During a 16-month period, 1372 patients were anaesthetized. The records of 21 patients with accidental oesophageal tube misplacement were available for retrospective evaluation. Nine patients were preventilated with FIO2 = 0.3 (ASA I), 12 patients with FIO2 = 1.0 (ASA II-III). Rapid detection of oesophageal tube position as early as the first ventilation is possible by capnometry, because of the highly significant difference in end-tidal CO2 (0.2 +/- 0.2 vol%; tracheal intubation: 3.7 +/- 0.9 vol.%; P less than 0.0001). The present advanced pulse oximetry method does not permit differentiation between oesophageal and tracheal tube position within 30 s in patients preventilated with FIO2 = 1.0. Oesophageal misplacement was detectable within 7.5 +/- 0.9 s in patients preventilated with FIO2 = 0.3 due to a 2.1 +/- 0.8% decrease in Sao2 (P less than 0.001). Our results underscore the significance of capnometry for rapid detection of inadvertent oesophageal intubation. High-resolution pulse oximetry is a valuable supplement but not a substitute for capnometry.

Carbon Dioxide↗
PubMed1995

Evaluation of capnography in nonintubated emergency department patients with respiratory distress.

OBJECTIVE: To evaluate the ability of noninvasive capnographic measurement of end-tidal CO2 tension (PetCO2) to predict arterial CO2 tension (PaCO2) in nonintubated ED patients with respiratory distress. METHODS: A prospective, nonblind study was performed in a level I trauma center/community teaching hospital ED. Participants included all nonintubated adult patients with respiratory distress requiring measurement of arterial blood gases (ABGs); 29 patients were enrolled. PetCO2 was measured with a capnography monitor, using both baseline tidal volumes and forced expiratory volumes. The bias between PetCO2 values and simultaneous measurements of PaCO2 by ABG was assessed. RESULTS: PetCO2, measured with forced expiration, and PaCO2 agreed well, with bias (i.e., average difference) = 0.44 +/- 0.52 kPa (3.3 +/- 3.9 torr). PetCO2 measured with the tidal volume breath produced an unacceptably high bias of 0.82 +/- 0.70 kPa (6.1 +/- 5.2 torr). Levels of agreement between PaCO2 were similar for smokers and nonsmokers and for men and women. The arterial-end-tidal CO2 tension (Pa-etCO2) difference was not related to PaCO2. Pa-etCO2 correlated with age (r = 0.473; p = 0.01), and was significantly higher in patients with pulmonary disease (1.32 +/- 0.56 kPa; 9.9 +/- 4.2 torr) than it was in those without pulmonary disease (0.46 +/- 0.55 kPa; 3.5 +/- 4.1 torr; p < 0.001). CONCLUSIONS: Noninvasive PetCO2 monitoring may adequately predict PaCO2 in nonintubated ED patients with respiratory distress who are able to produce a forced expiration. PetCO2 is less accurate for PaCO2 with tidal volume breathing and in patients with pulmonary disease.

Adult↗
PubMed1993

Use of capnography for assessment of the adequacy of alveolar ventilation during weaning from mechanical ventilation.

A prospective study was conducted to determine the reliability of noninvasive end-tidal CO2 (PETCO2) monitoring as a reflection of arterial CO2 tension (PaCO2) during weaning from mechanical ventilation (MV). Simultaneous PaCO2 and PETCO2 determinations were compared during MV and again during a spontaneous breathing trial just before returning the patient to MV. Three groups of patients recovering from acute respiratory failure were evaluated. Group 1 consisted of 16 patients (28 observations) without parenchymal lung disease. Group 2 consisted of 22 patients (31 observations) with alveolar filling diseases. Group 3 was composed of 13 patients (22 observations) with emphysema. Significant Pearson correlation coefficients were demonstrated between PaCO2 and PETCO2 during both MV and spontaneous breathing in all three groups. Significant correlation was also demonstrated between the change in PaCO2 and the change in PETCO2 associated with weaning for each group; however, the degree of correlation varied between groups. Our data suggest that capnography offers a reasonable estimate of PaCO2 and changes in PaCO2 during weaning in patients without parenchymal lung disease. However, PETCO2 is less sensitive to changes in PaCO2 for patients with parenchymal lung disease, particularly patients with emphysema. Interpretation of capnographic data requires a full understanding of its limitations. An approach to capnographic monitoring during weaning is discussed.

Aged↗
PubMed1989

Capnography is not as sensitive as pulmonary artery pressure monitoring in detecting marrow microembolism. Studies in a canine model.

We studied several methods for detecting pulmonary embolic events in a model of fat and marrow microembolism during canine cemented arthroplasty procedures. The cardiopulmonary effects of bilateral cemented arthroplasty in this model include increased pulmonary artery pressure and pulmonary vascular resistance accompanying a decrease in arterial oxygen tension. We documented significant fat and marrow microembolism by postmortem quantitative morphometry of lung sections. Vessels occluded ranged in diameter from 0.5 to 190 microns. The acute increases in pulmonary artery pressure (PAP) (to 26.8 +/- 4.4 mm Hg from 15.3 +/- 3.3 mm Hg) after cemented arthroplasty were not detected by changes in continuously monitored end-tidal CO2 or in right atrial or arterial blood pressures. Although capnography is a useful intra-operative monitor, in this model it is less sensitive than PAP monitoring in detection of fat and marrow microemboli.

Animals↗
PubMed1992

Accuracy of capnography in nonintubated surgical patients.

Previous studies have reported mixed results when correlating etCO2 and PaCO2 in mechanically ventilated patients with underlying respiratory disease. However, the utility and accuracy of capnography in nonintubated patients, without chronic pulmonary disease, has received little attention. We studied 25 nonintubated surgical patients to (1) examine the correlation between PaCO2 and etCO2 and (2) describe the relationship between dead space (VD/VT), venous admixture and P(a-et)CO2. End tidal CO2 was lower than PaCO2 by an average of 3.6 mm Hg. Regression analysis found a close correlation between dead space and the P(a-et)CO2 gradient (r = 0.77, p < 0.001), while venous admixture was of lesser importance (r = 0.47). Capnographic estimates of PaCO2 can be useful for continuously monitoring the respiratory status of nonintubated spontaneously breathing patients weaned from mechanical ventilation. This may be of particular value in trauma victims and in selected surgical patients without underlying respiratory disease in whom other injuries require continued critical care.

Adolescent↗
PubMed1992

[Expiratory capnography in asthma. Perspectives in the use and monitoring in children].

The shape of the capnogram, which is related to uneven ventilation, is modified in obstructive diseases and especially during crisis of asthma. The most significant change is a rise in the slope of the "alveolar plateau". In this study, we measured the end-tidal slope (ETS) of the capnogram, calculated on 0.36 s before the end of expiration, and we compared this indice to usual spirometric measurements (FEV 1) in 21 control subjects and in 24 asthmatic subjects. The mean ETS in control subject was 0.08 +/- 0.06%/s, it was 0.3 +/- 0.23% in asthmatic subjects (p < 0.001). In the latter, we found a very significant correlation between ETS and FEV 1 (r = 0.83, p < 0.001). Thirteen asthmatic subjects were tested for a second time, immediately after inhalation of a beta 2-mimetic drug. They exhibit a very strong correlation between the rise of FEV 1 and the loss of ETS (r = 0.96, p < 0.001). These results show that the analysis of the capnogram's shape is a quantitative method for evaluating the severity of the bronchospasm. This ability, added to specific advantages (non-invasiveness, effort-independence) opens new fields of application to capnography: measurement of the bronchospasm in children, computerized monitoring of asthma.

Adult↗
PubMed1991

[Evaluation of tissue perfusion by simultaneous monitoring of aortic flow rate and capnography].

Ten patients under general anaesthesia were subjected to non-invasive haemodynamic monitoring, together with arterial gasometry and capnography. When enflurane was administered for maintenance anaesthesia, a 33 percent fall in aortic flow rate was observed (P less than 0.01), together with prolongation of the pre-ejection period and left ventricular pre-ejection/ejection ratio, an increase of central venous pressure and total vascular systemic resistances. The end-expiratory CO2 (Pet CO2) was reduced by 13 percent (P less than 0.05). There was no significant variation in arteriolo-alveolar CO2 difference (P(a-A)CO2). Under dobutamine (mean dose: 3.4 +/- 0.5 micrograms/kg/min), the haemodynamic parameters returned to their initial values. Pet CO2 rose above its initial level (+ 12 percent; P less than 0.05), but P(a-A)CO2 was not significantly modified. The variations of Pet CO2 were parallel with those of aortic flow rate. It is concluded that the changes in Pet CO2 observed during haemodynamic modifications could be used as markers for qualitative evaluation of tissue perfusion.

Aged↗
PubMed1981

[Measurement of PACO2 in children by capnography and mass spectrometry (author's transl)].

The present study examines the errors of measurement under working conditions using a capnograph and suggests a methodology to obtain optimal results in a given clinical situation. The authors compare the PCO2 measured with the aid of capnograph using CO2 absorption by infrared, with simultaneous measurements of PCO2 using a mass spectrometer as the reference. The observations measured included static and dynamic responses to a step variation of 5% CO2 and also the PACO2 in normal 9 to 12 year old children. The results show that the errors using a capnograph may reach 45 per cent at the highest respiratory frequencies. The influence of the dimensions of the sampling apparatus and the output of the sampling pump on the measurement of PACO2 are discussed. The static and dynamic calibration allow optimal operating conditions for the requirements of a patient in bed. (In this study children aged 9 to 12, with a respiratory frequency of less than 40/min). The errors after achieving optimal conditions is independent of respiratory frequency and always remained less than 5 per cent. A few simple rules are suggested to avoid the errors we have seen and if proper precautions are taken capnography can be considered as a good method for measuring PACO2 in children.

Breath Tests↗
PubMed1995

[Capnography in pediatric anesthesia: pitfalls and applications].

Expired CO2 analysis is an important area of anaesthetic monitoring. It ranges from ventilator connection to the estimation of alveolar dead space. In paediatric anaesthesia, end tidal CO2 measurement and analysis as well as PaCO2 estimation are subject to a rather large number of mistakes. Confrontation between the technical specificities of CO2 monitors and the anatomical and physiological distinctive characteristics of the paediatric patient is mainly responsible for the interpretation difficulties encountered. Nevertheless capnography remains fundamental for paediatric ventilation monitoring.

Anesthesia, General↗
PubMed1994

[Noninvasive patient observation in veterinary medicine: pulse oximetry and capnography. I. Pulse oximetry].

Two non-invasive continuous techniques for monitoring the respiratory function during anaesthesia have been established during the last year: pulse oximetry for monitoring the adequate oxygen supply and capnography for measuring the carbon dioxide elimination. In human medicine both are accepted as essential monitors with great reliability. Whether clinical use and interpretation can be transferred to animals without any restrictions will be discussed by looking on the physical and engineering background as well as the physiologic interpretation of the measured variable and their capability to detect critical events during administration of anaesthesia. Part I: Pulse oximetry measures the arterial oxygen saturation continuously and non-invasively. Its application in veterinary medicine must be discussed critically concerning the method as well as the interpretation. The information obtained is very different during injectable and inhalant anaesthesia. Respiratory depression is easy to detect while the animal breathes room air spontaneously. Is the inspired air enriched with oxygen, like during inhalant anaesthesia, normal values of oxygen saturation can mask the respiratory insufficiency and may give a false sense of security.

Anesthesia↗
PubMedDate not supplied

Respiratory monitoring: pulse oximetry and capnography in children during anesthesia and intensive care.

Monitoring the critical care patient by pulse oximetry and capnography permits the early diagnosis and follow-up of various clinical events in a precise manner, with considerable safety and with no need for invasive procedures. These techniques have been extensively evaluated in adults, but only recently have they been studied in pediatric patients, including newborn infants. In the present review we discuss the working principles, indications, advantages and limitations of each technique, as well as the interpretation of the results.

Anesthesia↗
PubMedDate not supplied

[Evaluation of tissue perfusion by simultaneous non-invasive monitoring of the hemodynamic profile and capnography].

OBJECTIVES: To assess the simultaneous variations in blood gases and CO2 tele-expiratory pressure (ETCO2) produced by changes in tissue perfusion in anesthetized patients with stable lung perfusion, alveolar ventilation and metabolic states. MATERIAL AND METHODS: Forty patients were divided into two groups. Group 1 included 20 ASA I patients undergoing orthopedic surgery on the lower extremities. Group 2 included 20 ASA I-III patients undergoing peripheral vascular surgery during which myocardial depression developed after isoflurane administration. The decrease in minute volume was measured in the descending aorta by esophageal ultrasound in both groups. Other hemodynamic parameters were measured by digital plethysmography. ETCO2 was measured by lateral aspiration capnography, and central venous pressure was measured in group 2 by subclavian venous catheter. Measurements were taken before and after release of the tourniquet in group 1, and before and after the decrease in minute volume (> 30%) in group 2. RESULTS: Release of the tourniquet after a mean compression time of 51 +/- 07 minutes produced an increase of 52% (p < 0.001) in minute volume in all patients in group 1; an increase of 23% (p < 0.001) in ETCO2; and a decrease of 60% (p < 0.001) in total vascular resistance. In group 2 a 15% decrease in ETCO2 (p < 0.01) was observed, coinciding with a 35% decrease in minute volume (p < 0.01). CONCLUSIONS: An increase in minute volume produces an increase in ETCO2 while a decrease in minute volume results in a decrease in ETCO2. This means that sharp changes in ETCO2 may be useful in judging the degree of change in tissue perfusion when other parameters like alveolar ventilation, lung perfusion and metabolic rate remain constant.

Adult↗
PubMed1993

[Monitoring respiratory mechanism and gas exchange in patients on respirators (side stream spirometry, capnography, oxigraphy, measurement of anesthetic agent concentration, pulse oximetry)].

Author describes the working principles of the side stream spirometry, capnography, oxygraphy, anaesthetic agent concentration measurement, pulse oximetry, all of them incorporated in a new type of monitor, as well as the informations obtained by using them, concerning lung mechanics and gas exchange. The graphic and digital data, provided by the monitor are visualizing the correlations among the components of lung mechanics and are helping in setting up optimal ventilatory parameters, both during anaesthesia and during ventilation in an intensive care unit. The monitor approaches gas exchange from several aspects, which enhances the judgement of the efficacy of ventilation.

Anesthesia, Inhalation↗
PubMed1993

[The detection of gas embolisms in neurosurgery caused by joint monitoring with capnography and the Swan-Ganz probe. (Apropos of 7 patients operated on in the sitting position].

The aim of this study was to detect per-operative venous gas embolism in neurosurgery using capnography coupled to the Swan-Ganz catheter method. Using both methods, our study, carried out on seven patients operated in the sitting position, showed an occurrence of air embolism in four cases. The diagnosis of air embolism was made on a rapid and progressive drop of FECO2 with, at the same time, a rise of the pulmonary arterial pressure.

Adult↗