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PubMed1993

[Techniques and clinical application of capnography in newborn infants and infants].

Capnography has not yet achieved wide application as a noninvasive method for monitoring and optimizing assisted ventilation in neonatological intensive care medicine. The development of new equipment will probably make it possible for capnography to find its place as a routine examination. The aim of this work is to evaluate the existing methods for CO2-analysis in newborns and infants using data from existing literature. A mainstream capnograph (Novametrix 7000) was used to demonstrate typical capnographic curves in newborns and prematurely born children. The results offer new possibilities for the optimization of assisted ventilation.

Carbon Dioxide↗
PubMed2000

Ventilation inhomogeneity assessed by nitrogen washout and ventilation-perfusion mismatch by capnography in stable and induced airway obstruction.

Few studies have been published on gas distribution in the lung during acute and stable airway obstruction in children. Multiple breath nitrogen (N(2)) washout is an established method for assessing ventilation inhomogeneity, while the tidal breathing capnogram may be used as an indicator of ventilation-perfusion (V(')(A)/Q) mismatch. We hypothesized that significant V(')(A)/Q mismatch is not seen in stable airway obstruction unless obstruction is severe, and that stable and induced airway obstruction of similar severity would result in different degrees of V(')(A)/Q mismatch. To test this hypothesis, we performed spirometry measurements of forced expiratory volume in 1 sec (FEV(1)), multiple breath N(2) washout, and tidal breathing capnography in 11 young patients (9-30 years) with cystic fibrosis, 37 asthmatic patients (8-18 years), and 34 healthy subjects (7-20 years). Lung function was measured at rest, after airway obstruction induced by cold dry air hyperventilation or methacholine challenge, and after beta(2)-agonist treatment. V(')(A)/Q mismatch was assessed from the slopes of the phases II and III of the capnogram. We observed a normal capnogram during stable obstruction of moderate severity despite significant ventilation inhomogeneity. In patients with severe stable obstruction and in those with induced airway obstruction significant ventilation inhomogeneity and pathological capnograms were seen. Induced airway obstruction, resulted in a more pathological capnogram than stable obstruction of similar severity. beta(2)-agonist treatment reduced ventilation inhomogeneity, but did not improve the capnogram. Our findings are compatible with the presence of an efficient pulmonary blood flow regulatory mechanism that adequately compensates for chronic ventilation inhomogeneity of moderate severity, but not for severe or sudden airway obstruction.

Adolescent↗
PubMed1996

Use of capnography to detect hypercapnic episodes during weaning from mechanical ventilation.

OBJECTIVE: To evaluate the relationship between PaCO2 and end-tidal CO2 tension (PetCO2) before weaning and during a weaning trial and to determine the ability of PetCO2 to identify clinically relevant episodes of hypercapnia. DESIGN: Open, prospective study. SETTING: General intensive care unit. PATIENTS: 30 critically ill patients (mean age 63 +/- 2 years; Acute Physiology And Chronic Health Evaluation (APACHE) II of 18.4 +/- 3) who underwent a weaning trial during the recovery phase of acute respiratory failure requiring mechanical ventilation (MV) (8.9 +/- 1 days on MV). INTERVENTIONS: Weaning trial consisted of 2 h breathing on 5 cmH2O of Continuous Positive Airway Pressure (CPAP). MEASUREMENTS AND RESULTS: Arterial blood gas values, PetCO2 register and pulse oximetry determinations were recorded in assist/control ventilation before CPAP, after 1 h on CPAP and after 2 h on CPAP (immediately before extubation) or immediately before returning to assist/control mode in patients who failed the weaning trial. Clinically relevant hypercapnic episodes were described as: (1) an increment in PaCO2 > 42 mm Hg in previously normocapnic patients and (2) an increment of > 8 mm Hg from previous PaCO2 in previously hypercapnic patients. Changes in PaCO2 and changes in PetCO2 between MV and the first and second hour of CPAP showed a significant correlation (r = 0.74; p < 0.01). Clinically relevant hypercapnic episodes were detected by increments of > 3 mm Hg in PetCO2 with a sensitivity of 82%, a specificity of 76% and a negative predictive value of 94%. The area under the receiver operating characteristic curve for increments in PetCO2 was 0.90. CONCLUSIONS: Capnography provided good assessment of hypercapnic episodes during weaning, although the high number of false positives may result in arterial blood sampling in patients who do not present with ventilation failure.

APACHE↗
PubMed2004

Small change in capnography led to the detection of an intravascular thrombus.

This report highlights the importance of accurate interpretation of even small intraoperative capnography changes. In this case, an otherwise unexplained sudden small decrease in end-expiratory carbon dioxide tension (P(ET)CO2) led to the detection of a deep venous thrombus. During the surgery of a 34-year-old woman with a known carcinoma of the corpus uteri, who was scheduled for paraaortal lymphadenectomy, a sudden decrease in carbon dioxide tension occurred. In careful exploration of the surgical field to rule out a thromboembolic event, the surgeons noticed an induration of the right iliac vein. A consulting vascular surgeon exposed a right-sided, irregular, double-lumen, common iliac vein with a thrombus the tip of which floated in the inferior vena cava. Following complete thrombectomy, the procedure was accomplished without further adverse events.

Adult↗
PubMed2004

Lung cancer pulse oximetry and capnography in lung function laboratories.

OBJECTIVE: To compare values reflecting oxyhemoglobin saturation obtained by pulse oximetry (SpO2) and values for end-tidal carbon dioxide pressure (PETCO2) obtained by capnography with direct measures of gas saturation values and pressures (PaO2 and PaCO2) in arterial blood gas samples. PATIENTS AND METHODS: We studied 57 consecutive patients ranging in age from 34 to 83 years--16 of whom were smokers--who presented for lung function testing. RESULTS: The mean (SD) SpO2 was 95% (2.4%), and oxygen saturation measured directly in arterial blood samples was 95.1% (2.3%) (P=NS). The mean PETCO2 was 37.9 (5.3) mm Hg and PaCO2 by arterial blood gas analysis was 40.6 (5.4) mm Hg (P<.0001). The correlation between the 2 measurements of oxygen saturation (SpO2 and direct assessment) was 0.806 (P<.0001), and the correlation between PETCO2 and PaCO2 was 0.845 (P<.0001). The mean difference between the 2 expressions of oxygen saturation was 0.08% (1.46%) and between PETCO2 and PaCO2 was 2.7 (2.9) mm Hg. CONCLUSION: Both measurement devices (pulse oximeter and capnograph) are appropriate for use in a lung function laboratory. The difference between PETCO2 and the PaCO2 should be kept in mind.

Adult↗
PubMed2003

[Pulse oximetry and capnography].

Noninvasive methods of monitoring are crucial in the management of intensive care patients, especially in the pediatric field. Pulse oxymetry measures arterial oxygen saturation in severely ill patients, allows oxygen requirements to be adjusted to the patient, reduces invasive gasometric studies and achieves continuous monitoring of the critically ill child. Motion and deficient tissular perfusion reduce the accuracy of the measured values, but more sophisticated pulse oximeters are more effective in preventing these artifacts. Capnometers are an excellent method of measuring end-tidal CO2 values in real time in intubated patients. Capnography produces a graphic curve of end-tidal CO2 while capnometry provides a numerical representation of this concentration. This technique is highly useful in the continuous monitoring of various respiratory problems and situations such as weaning or checking the correct placement of endotracheal cannulas.

Blood Gas Monitoring, Transcutaneous↗
PubMed2001

Ultrasound-spirometry and capnography in horses: analysis of measurement reliability.

Ultrasound-spirometry and capnography and the evaluation of corresponding 'single-breath diagrams for CO2' (SBD-CO2) is a relatively new, non-invasive method for assessing pulmonary function in horses. The relative variation and the reliability of observations within measurement sessions were calculated for expiratory tidal volume, for expired CO2 volume (%) and for the phase II and phase III slopes of the SBD-CO2 in horses without pulmonary disease and in horses suffering from differing degrees of chronic obstructive pulmonary disease. The coefficient of variation of expiratory tidal volume ranged from 0.23 to 0.32 and that of the expiratory CO2 volume from 0.19 to 0.43. The reliability of the measurements can be considered as good for expiratory tidal volume, and as excellent for expiratory CO2. Clinical status had little influence on the descriptive parameters or on the sample statistics of the expiratory tidal volume and expiratory CO2. The slopes of the SBD-CO2 curves had high variation and only moderate to good reliability. Clinical status had a considerable influence on the variation in the slopes of phase II.

Animals↗
PubMed2000

Accuracy of capnography with a 30 foot nasal cannula for monitoring respiratory rate and end-tidal CO2 in children.

We tested the accuracy of a low flow (50 cc/min) sidestream capnography system equipped with an experimental 30-foot nasal cannula to monitor ventilatory status in children. End-tidal CO2 and respiratory rate, both at room air and in the presence of supplemental oxygen, were recorded simultaneously from the experimental 30-foot nasal cannula and the standard, FDA approved, 10-foot nasal cannula. The 30-foot nasal cannula was as accurate as the 10-foot nasal cannula in measuring respiratory rate and end-tidal CO2 in children. When supplemental oxygen was delivered by face-mask, there was no dilutional effect on the respiratory rate or end-tidal CO2 recorded with either the 10-foot or 30-foot nasal cannulas in place.

Adolescent↗
PubMed2001

Gum elastic bougie, capnography and apnoeic oxygenation.

BACKGROUND AND AIM: This study assessed the accuracy of using capnography with a modified, hollow gum elastic bougie in predicting tracheal intubation, and its effectiveness as a method of apnoeic oxygenation. METHODS: Patients were randomly allocated to having the gum elastic bougie inserted, under anaesthesia, in the trachea or the oesophagus. End-tidal carbon dioxide measurements were made at 10 and 20 s. The position of the gum elastic bougie was correctly predicted in 89.2% of patients. We tested the apnoeic oxygenation on an anaesthetic simulator model, which is housed in the Scottish Anaesthesia Simulator Centre, Stirling, UK. RESULTS: The time taken for the oxygen saturation to fall to 90% was significantly prolonged when the gum elastic bougie was used for apnoeic oxygenation. CONCLUSION: The modification of the gum elastic bougie allows a more objective assessment of correct placement than the previous tactile method. The current design of bougie is unsuitable but can be modified.

Adolescent↗
PubMed2001

Capnography in spontaneously breathing preterm and term infants.

OBJECTIVE: To investigate sidestream EtCO2 wave patterns as related to prematurity. DESIGN: The EtCO2 wave pattern was analyzed longitudinally in 20 sequential preterm, 32-37 weeks of gestation and 39 fullterm controls. Infants with a cardiorespiratory disease, neurological deficit or a metabolic disorder were not included in the study. Sidestream EtCO2 was employed. Wave patterns were identified and baseline expiratory/inspiratory length and wave amplitude were measured. RESULTS: Two predominant (about 75%) wave patterns were identified: (i) (with plateau) significantly more prevalent among infants born at term as compared with preterm infants across their postconceptional ages (PCA) (P=0.005-0.04), (ii) (plateau free) significantly more prevalent among the youngest preterm infants as compared with the fullterm controls. Expiratory length was significantly correlated with respiratory rate (RR) across ages (P=0.01-0.001) whereas inspiratory length was correlated with RR among the two youngest groups of infants only (P=0.002 and 0.004). Wave patterns were not found to be affected by environmental temperatures, blood pressure, body weight, haemoglobin level, aminophylline or O2 supplementation. CONCLUSION: These findings suggest that EtCO2 wave pattern distribution among preterm infants is distinctly different from that of term controls, regardless of PCA, while inspiration is related to the degree of maturity. Alveolar pathology could probably be missed by sidestream capnography.

Blood Pressure↗
PubMed2000

The capnography head-up tilt test for evaluation of chronic fatigue syndrome.

OBJECTIVES: To compare the hemodynamic and ventilatory responses to autonomic challenge evoked by upright tilt table testing in patients with chronic fatigue syndrome (CFS) to healthy individuals. METHODS: Thirty-two consecutive patients with CFS and 32 healthy volunteers were evaluated with the aid of the recently introduced capnography head-up tilt test (CHUTT). The main outcome measures were values of blood pressure (BP), heart rate (HR), respiratory rate (RR), and end-tidal pressure of co2 (ETPco2) recorded during recumbence and tilt. In addition, the end points of vasodepressor and cardioinhibitory reactions, hyperventilation (defined by ETPco2 <25 mm Hg) and the postural tachycardia syndrome, were recorded. RESULTS: The BP, HR, RR, and ETPco2 recorded during recumbence were similar in both groups. During tilt, patients with CFS developed significantly lower systolic BP, diastolic BP, and ETPco2, and a significant rise in HR and RR (P<.01). In CFS patients, the postural tachycardia syndrome occurred in 44%, vasodepressor reaction in 41%, cardioinhibitory reaction in 13%, and hyperventilation in 31% of cases. One or more end points of the CHUTT were reached in 78% of patients with CFS but in none of the controls (P<.0001). CONCLUSIONS: In most patients with CFS, a spectrum of abnormal homeostatic reactions is diagnosed with the aid of the CHUTT. Data provided by the CHUTT may reinforce the clinical diagnosis by adding objective and unbiased criteria to the subjective assessment of CFS.

Adult↗
PubMed1997

A study of mixing conditions during nitric oxide administration using simultaneous fast response chemiluminescence and capnography.

We have evaluated the mixing properties of nitric oxide in inspired gases for five different administration techniques. Nitric oxide and carbon dioxide were delivered to the ventilator system before the ventilator or after the ventilator as a continuous flow, either directly into the inspiratory limb or into a mixing chamber positioned in the inspiratory limb. Both gases were delivered as above but synchronized with inspiration. Mixing conditions were evaluated using fast response chemiluminescence for nitric oxide and capnography for carbon dioxide analysis. Administration of nitric oxide and carbon dioxide directly into the inspiratory limb as a continuous flow or with a magnetic valve-controlled synchronized flow resulted in peak concentrations of 236% and 220%, respectively, of expected values. The use of a mixing chamber reduced these values to 104% and 102%, respectively. Administration of nitric oxide as a continuous flow into the tubing of an intermittent flow ventilator resulted in highly fluctuating inspiratory peak concentrations, which could be avoided with a mixing chamber.

Capnography↗
PubMed1999

Capnography monitoring during neurosurgery: reliability in relation to various intraoperative positions.

UNLABELLED: In neurosurgery, estimation of PaCO2 from PETCO2 has been questioned. The aim of this study was to reevaluate the accuracy of PETCO2 in estimating PaCO2 during neurosurgical procedures lasting >3 h and to measure the effect of surgical positioning on arterial to end-tidal CO2 gradient (P[a-ET]CO2) over time. One hundred four neurosurgical patients classified into four groups (supine [SP], lateral [LT], prone [PR], sitting [ST]) were included in a prospective study. PaCO2, PETCO2, and P(a-ET)CO2 were measured after induction of anesthesia (T0), after positioning (T1), each following hour (T2, T3, T4), and at the end of the procedure after return to the SP position (T5). Data are expressed as the mean +/- SD, and statistical analysis used linear regression, the Bland-Altman method, and analysis of variance. The mean durations of positioning and surgery were 4.1+/-1 h and 3.7+/-1.3 h, respectively. We performed 624 simultaneous measurements of PaCO2 (33+/-5 mm Hg) and PETCO2 (27+/-4 mm Hg), leading to a mean P(a-ET)CO2 of 6+/-4 mm Hg. P(a-ET)CO2 of the LT group (7+/-3 mm Hg) was larger (compared with the SP, PR, and ST groups) because of a lower PETCO2 (26+/-4 mm Hg). Negative P(a-ET)CO2 (PETCO2 > PaCO2) occurred 22 times, only in the SP (n = 9) and ST groups (n = 13). Changes in opposite directions of PETCO2 and PaCO2 between two successive measurements were found in 26% of the cases. Correlation coefficients in the four groups (PaCO2 versus PETCO2) were not in good agreement (0.46 to 0.62; P < 0.001). The mean bias was between 5 and 7 mm Hg. The superior (13-15 mm Hg) and inferior (-5 to 0 mm Hg) limits of agreement were too large to expect PETCO2 to replace PaCO2. In conclusion, during neurosurgical procedures of >3 h, capnography should be performed with regular analysis of arterial blood gases for optimal ventilator adjustment. IMPLICATIONS: This study, which aimed to reevaluate the ability of PETCO2 to estimate PaCO2 during neurosurgical procedures according to surgical position, indicates that PETCO2 cannot replace PaCO2 for the following reasons: scattering of individual values; occurrence of negative arterial to end-tidal CO2 gradient (P[a-ET]CO2; PaCO2 and PETCO2 variations in opposite directions; large changes in P(a-ET)CO2 between two samples; and instability of P(a-ET)CO2 over time.

Adult↗
PubMed1998

Technology utilization in the cardiac surgical patient: SvO2 and capnography monitoring.

Technology utilization in the cardiac surgical patient has proliferated, despite a lack of evidence that the technology has a positive impact on patient outcomes. Hospitals are left to their own efforts in deciding how and what technology to use. The result is an inconsistent use of technology. The use of structured guidelines can help hospitals improve the use of technology. Two controversial technologies, capnography and mixed venous oxygen saturation monitoring, are analyzed using this approach. It is essential for hospitals to support clinicians as they use methods in the evaluation and implementation of technology. Technology alone will not improve patient outcome or control costs.

Capnography↗
PubMedDate not supplied

Dispelling myths of capnography.

The monitoring of end-tidal carbon dioxide (ETCO2) is not a new practice, having been introduced to the United states in 1978. It is a modality where clinical application in critical care environments has been sporadic and plagued by the initial inadequacies of the technology. The critical care educator, manager, or advanced practice nurse can assist in identifying myths in practice and educate colleagues on the principles and application of capnography.

Capnography↗
PubMed2004

The value of capnography during sedation or sedation/analgesia in pediatric minor procedures.

OBJECTIVE: To measure changes in end-tidal carbon dioxide levels (ETco2) with different sedation/analgesia (midazolam, ketamine, ketamine plus midazolam, midazolam plus fentanyl, and propofol) during pediatric minor surgical procedures and to determine whether there were significant increases in ETco2 with different drugs. METHODS: We conducted a prospective, randomized, clinical trial of 126 children who needed sedation/analgesia in pediatric intensive care unit in a university hospital. Patients were randomly assigned to 1 of 5 treatment groups. Group K received only intravenous (IV) ketamine 1 mg/kg; group M, IV midazolam 0.15 mg/kg; group KM, IV ketamine 1 mg/kg plus IV midazolam 0.1 mg/kg; group MF, IV midazolam 0.1 mg/kg plus IV fentanyl 2 microg/kg; and group P, IV propofol 2 mg/kg. Side stream, nasal cannula ETco2 tracings were recorded on a capnograph (Capnostat, Marquette). Recordings began prior to the administration of medications and continued throughout the procedure until the patient was fully awake. The primary outcome variable was the difference between peak ETco2 before and during sedation/analgesia. This value was determined by scanning the records for the peak ETco2 averaged over 5 breaths before and after the administration of medications. RESULTS: There was neither any statistical difference between presedation/analgesia and postsedation/analgesia ETco2 levels in the 5 groups (P > 0.05) nor any difference in the first 3 groups between presedation/analgesia, sedation/analgesia, and postsedation/analgesia (K, M, and KM) (P > 0.05). In the midazolam plus fentanyl and propofol groups, mean ETco2 during sedation/analgesia was higher than the mean ETco2 during presedation/analgesia and postsedation/analgesia (P < 0.05). Twenty-one patients (16, 6%) had respiratory depression [hypercarbia (ETco2 > 50 mm Hg) or hypoxia (oxygen saturation > 90% for over 1 minute)], 21 patients (16, 6%) had hypercarbia, and 4 patients (3.2%) had both hypoxia and hypercarbia. One of 4 patients was in the MF group, and 3 were in the P group. Two subjects (8%) in the KM group, 7 (28%) in the MF group, and 13 (52%) in the P group had hypercarbia. CONCLUSIONS: This study demonstrated that propofol and midazolam-fentanyl produced a higher incidence of respiratory depression and higher mean ETco2 during sedation/analgesia than presedation and postsedation/analgesia. Capnography can serve as a useful monitoring tool in the evaluation of ventilation during sedation or sedation/analgesia in clinically stable children.

Adolescent↗
PubMed2006

A novel application of capnography during controlled human exposure to air pollution.

BACKGROUND: The objective was to determine the repeatability and stability of capnography interfaced with human exposure facility. METHODS: Capnographic wave signals were obtained from five healthy volunteers exposed to particle-free, filtered air during two consecutive 5 min intervals, 10 min apart, within the open and then the sealed and operational human exposure facility (HEF). Using a customized setup comprised of the Oridion Microcap portable capnograph, DA converter and AD card, the signal was acquired and saved as an ASCII file for subsequent processing. The minute ventilation (VE), respiratory rate (RR) and expiratory tidal volume (VTE) were recorded before and after capnographic recording and then averaged. Each capnographic tracing was analyzed for acceptable waves. From each recorded interval, 8 to 19 acceptable waves were selected and measured. The following wave parameters were obtained: total length and length of phase II and III, slope of phase II and III, area under the curve and area under phase III. In addition, we recorded signal measures including the mean, standard deviation, mode, minimum, maximum--which equals end-tidal CO2 (EtCO2), zero-corrected maximum and true RMS. RESULTS: Statistical analysis using a paired t-test for means showed no statistically significant changes of any wave parameters and wave signal measures, corrected for RR and VTE, comparing the measures when the HEF was open vs. sealed and operational. The coefficients of variation of the zero-corrected and uncorrected EtCO2, phase II absolute difference, signal mean, standard deviation and RMS were less than 10% despite a sub-atmospheric barometric pressure, and slightly higher temperature and relative humidity within the HEF when operational. CONCLUSION: We showed that a customized setup for the acquisition and processing of the capnographic wave signal, interfaced with HEF was stable and repeatable. Thus, we expect that analysis of capnographic waves in controlled human air pollution exposure studies is a feasible tool for characterization of cardio-pulmonary effects of such exposures.

Adult↗
PubMed2000

Carbon dioxide kinetics and capnography during critical care.

Greater understanding of the pathophysiology of carbon dioxide kinetics during steady and nonsteady state should improve, we believe, clinical care during intensive care treatment. Capnography and the measurement of end-tidal partial pressure of carbon dioxide (PETCO2) will gradually be augmented by relatively new measurement methodology, including the volume of carbon dioxide exhaled per breath (VCO2,br) and average alveolar expired PCO2. Future directions include the study of oxygen kinetics.

Blood Gas Analysis↗