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PubMed2001

Respiratory monitoring in neuromuscular disease - capnography as an additional tool?

Daytime complaints like fatigue, sleepiness and cognitive dysfunction in neuromuscular disease can be due to nocturnal hypercapnia and hypoxemia. Daytime respiratory diagnostics does not reflect sleep disordered breathing. Nocturnal pulse oxymetry and capnography were performed in 11 patients (15-75 years old) with different slowly progressive neuromuscular diseases. Only four patients complained of dyspnea. Pulmonary function was abnormal in three patients. Blood gas samples showed a hypoxemia in three patients. Pulse oxymetry results were pathological in six patients. Nine patients presented abnormal capnographies. According to these results either nocturnal oxygen application was initiated or ventilatory parameters were modified. Daytime symptoms and muscular strength improved markedly. Capnography and pulse oxymetry should be performed during the course of neuromuscular disease to detect respiratory insufficiency. Capnography seems to be a more sensitive indicator for respiratory impairment especially when artificial ventilation has been initiated.

Adolescent↗
PubMed1998

Influence of pulse oximetry and capnography on time to diagnosis of critical incidents in anesthesia: a pilot study using a full-scale patient simulator.

OBJECTIVE: Many studies (outcome, epidemiological) have tested the hypothesis that pulse oximetry and capnography affect the outcome of anesthetic care. Uncontrollable variables in clinical studies make it difficult to generate statistically conclusive data. In the present study, we eliminated the variability among patients and operative procedures by using a full-scale patient simulator. We tested the hypothesis that pulse oximetry and capnography shorten the time to diagnosis of critical incidents. METHODS: A simulator was programmed to represent a patient undergoing medullary nailing of a fractured femur under general anesthesia and suffering either malignant hyperthermia, a pneumothorax, a pulmonary embolism or an anoxic oxygen supply. One hundred thirteen anesthesiologists were randomly assigned to one of two groups of equal size, one with access to pulse oximetry and capnography data and the other without. Each anesthesiologist was further randomized to one of the four critical incidents. Each anesthetic procedure was videotaped. The time to correct diagnosis was measured and analyzed. RESULTS: Based on analysis of 91 of the subjects, time to diagnosis was significantly shorter (median of 432 s vs. >480 s) for the anoxic oxygen supply scenario (p = 0.019) with pulse oximetry and capnography than without. No statistical difference in time to diagnosis was obtained between groups for the other three critical incidents. CONCLUSIONS: Simulation may offer new approaches to the study of monitoring technology. However, the limitations of current simulators and the resources required to perform simulator-based research are impediments to wide-spread use of this tool.

Anesthesia, General↗
PubMedDate not supplied

Capnography in the gastroenterology lab.

This article provides the reader with information and education regarding the use of capnography for both adult and pediatric patients undergoing procedural sedation during endoscopy by: reviewing the basics of capnography, in addition to the physiology of ventilation and oxygenation; illustrating how capnography may provide an earlier warning of hypoxemia than does pulse oximetry; briefly discussing current guidelines for procedural sedation and the potential role of capnography; and reviewing clinical situations causing changes in the capnogram waveforms and the nursing interventions that should be made in response to such changes.

Analgesia↗
PubMed2004

Current limitations of volumetric capnography in surfactant-depleted small lungs.

OBJECTIVE: To investigate the suitability of volumetric capnography for assessing alveolar gas exchange in very small, surfactant-depleted lungs. DESIGN: Prospective animal trial. SETTINGS: Animal laboratory in a university setting. SUBJECTS: Twenty-one ventilated newborn piglets (age <12 hrs; median weight, 890 g; range, 560-1435 g). INTERVENTIONS: Bronchoalveolar lavage with instillation of 30 mL/kg normal saline. Ventilatory, circulatory, and lung mechanic variables were measured before and 0, 30, and 60 mins after bronchoalveolar lavage. MEASUREMENTS AND MAIN RESULTS: The alveolar deadspace fraction calculated by the Bohr and the Bohr/Enghoff equations increased three-fold (p<.001) after bronchoalveolar lavage in capnograms with distinct alveolar plateau, whereas in capnograms without alveolar plateau no statistical significant difference was seen. The main problem of capnography in small and especially stiff lungs was the high number of discarded records exclusively caused by a missing alveolar plateau. Rates of discarded records of capnography were 9.5% before lavage and increased (p<.01) to 52.4%, 47.6%,42.8% after bronchoalveolar lavage (0, 30, and 60 mins). With decreasing exhalation time, the number of discarded records increased significantly. No plateau was seen in >75% of recorded files with exhalation times <200 msecs. The effect of bronchoalveolar lavage on all variables measured was quite different, with the highest impact on required ventilatory settings, calculated oxygenation variables, and compliance. The effect of bronchoalveolar lavage on arterio-alveolar CO2 difference, CO2 production, and alveolar deadspace was much lower and statistically significant only in capnograms with alveolar plateau. CONCLUSIONS: Volumetric capnography is a useful tool to detect impaired alveolar gas exchange in surfactant-depleted small lungs. However, the method failed if there was no alveolar plateau in the volumetric capnogram especially in stiff lungs with short exhalation times.

Analysis of Variance↗
PubMed2005

Capnography as a rapid assessment and triage tool for chemical terrorism.

The assessment and triage of victims of chemical terrorism in the emergency department and the prehospital setting has become an important priority. This article proposes the use of capnography as a prehospital assessment and triage tool for monitoring victims of chemical terrorism and for critically ill patients. Capnography provides the ABCs in less than 15 seconds and identifies the common complications of chemical terrorism. Further, the reliability of capnography is not affected by motion artifact or low perfusion and it is accurate and reliable in actively seizing patients. Emergency departments and emergency medical services systems should consider adding capnography to their chemical terrorism education and training.

Capnography↗
PubMed2005

Capnography screening for sleep apnea in patients with acute stroke.

Sleep apnea syndrome (SAS) is a prominent clinical feature in acute stroke patients. Diagnosis is usually established by polysomnography or cardio-respiratory polygraphy (CRP). Both diagnostic procedures produce high costs, are dependent on the access to a specialized sleep laboratory, and are poorly tolerated by patients with acute stroke. In this study we therefore investigated whether capnography may work as a simple screening tool in this context. In addition to conventional CRP, 27 patients with acute stroke were studied with capnography provided by our standard monitoring system. The trend graphs of the end-tidal CO(2) values (EtCO(2)) were used to determine the capnography-based estimate of the apnea-hypopnea index (AHI(CO2)). Index events were scored when the EtCO(2) value dropped for > 50% of the previous baseline value. We found that the AHI(CO2) correlated significantly with the apnea-hypopnea index measured with conventional CRP (AHI(CRP)) (r = 0.94; p < 0.001). An AHI(CO2) > 5 turned out to be highly predictive of an AHI(CRP) > 10. According to our findings, routinely acquired capnography may provide a reliable estimate of the AHI(CRP). The equipment needed for this screening procedure is provided by the monitoring systems of most intensive care units and stroke units where stroke patients are regularly treated during the first days of their illness. Therefore, early diagnosis of SAS in these patients is made substantially easier.

Aged↗
PubMed2004

Capnography accurately detects apnea during monitored anesthesia care.

Apnea and airway obstruction are common during monitored anesthesia care (MAC). Because their early detection is essential, we sought to measure the efficacy of capnography as an indicator of apnea during MAC at a variety of oxygen flow rates compared with thoracic impedance. Anesthesia care providers using standard American Society of Anesthesiologists monitors were blinded to capnography and thoracic impedance monitoring. Ten (26%) of the 39 patients studied developed 20 s of apnea; none was detected by the anesthesia provider, but all were detected by capnography and impedance monitoring. There was no difference in detection rates between the two methods. Higher oxygen flow rates decreased the amplitude of the capnograph but did not interfere with apnea detection. This pilot study revealed that apnea of at least 20 s in duration may occur in every fourth patient undergoing MAC. Although these episodes were undetected by the anesthesia provider, they were reliably detected by both capnography and respiratory plethysmography. Monitoring of nasal end-tidal CO(2) is an important way to improve safety in patients undergoing MAC.

Adolescent↗
PubMed1998

Aspirated air capnography with esophageal detector device to confirm tracheal intubation in rapid sequence induction.

Verification of the proper placement of a tracheal tube by capnography in rapid sequence induction can lead to aspiration if the patient is ventilated with the tube in the esophagus. In this study we have associated the capnography with the esophageal detector device as modified by Nunn. In 49 patients, two endotracheal tubes were introduced, one in the esophagus and the other in the trachea. An anesthesiologist, unaware of which tube is in the trachea, squeezed the bulb of the esophageal detector device, attached it to the sidestream of the capnography and the endotracheal tubes, then released it. No reinflation of the bulb was seen with the esophageal tube. Two types of reinflation were seen with the tracheal tube: slow (6 cases), all were obese, and instant (43 cases) in the remaining patients. The air aspirated from the respiratory tract by the bulb was analyzed by the capnograph; CO2 was detected from all the tracheal tubes but not from the esophageal ones. We concluded that the esophageal detector device and capnography used as described in our study is a simple reliable test to confirm the proper placement of a tracheal tube before starting ventilation in rapid sequence induction.

Adolescent↗
PubMed1995

Terminology and the current limitations of time capnography: a brief review.

The carbon dioxide (CO2) trace versus time (time capnography) is convenient and adequate for clinical use. This is the method most commonly utilized in capnography. However, the current terminology in time capnography has not yet been standardized and is, therefore, a potential source of confusion. Standard terminology that is based on convention and logic to represent the various phases of a time capnogram is essential. The time capnogram should be considered as two segments: an inspiratory segment and an expiratory segment. The inspiratory segment is termed as phase ); the expiratory segment is divided into phases I, II, III, and, occasionally, IV. Phase I represents the CO2-free gas from the airways (anatomical dead space); phase II consists of a rapid S-shaped upswing on the tracing due to mixing of dead space gas with alveolar gas; and phase III, the alveolar plateau, represents CO2-rich gas from the alveoli. The physiologic basis of phase IV, the terminal upswing at the end of phase III, which is observed in capnograms recorded under certain circumstances (such as in pregnant subjects and obese subjects) is discussed in detail. The clinical implications of the alpha angle, which is the angle between phases II and III, and the beta angle, which is the angle between phases III and the descending limb of phase 0, are outlined. The subtle but important limitations of time capnography are reviewed; its current status as well as its future potential are explored.

Carbon Dioxide↗
PubMed1994

Control of carbon dioxide levels during neuroanaesthesia: current practice and an appraisal of our reliance upon capnography.

With the widespread availability of capnography, many anaesthetists have swung away from formally verifying hypocapnia by intraoperative arterial blood gas analysis and, instead, have come to rely upon capnography as an acceptable and constant predictor of arterial CO2 tension (PaCO2) during neurosurgery. However, the nature of the arterial-end-tidal CO2 gradient is complex, and is frequently unexpectedly large, or even negative. The importance of close intraoperative CO2 control during neurosurgery--more specifically, routine hyperventilation, and our reliance upon capnography to guide intraoperative management--is reappraised. There is a growing appreciation of the adverse effects of hyperventilation and hypocarbia, especially upon abnormal or ischaemic brain, and it is clear that capnography alone cannot be used to confidently predict the true PaCO2 during neuroanaesthesia.

Anesthesia, General↗
PubMed1989

An investigation of capnography and pulse oximetry as monitors of pediatric patients sedated for dental treatment.

Traditional methods of monitoring sedated pediatric dental patients have major shortcomings. This study evaluated the use of capnography in conjunction with pulse oximetry for monitoring children during conscious sedation for dental treatment. The specific purposes of the study were to determine if capnography would: (1) detect ventilatory changes that subsequently cause an oxyhemoglobin desaturation as detected by pulse oximetry; and (2) detect an airway obstruction. Ten pediatric dental patients (mean age 2 years, 10 months) were sedated with 75 mg/kg of chloral hydrate in strict accordance with the Guidelines for the Elective Use of Conscious Sedation, Deep Sedation, and General Anesthesia in Pediatric Patients of the American Academy of Pediatric Dentistry and the American Academy of Pediatrics (1985). All patients were monitored continuously using both capnography and pulse oximetry. Analysis of data obtained using these monitors revealed that specific end-tidal CO2 values were not predictive for subsequent oxyhemoglobin desaturations and that capnography was very accurate in detecting complete obstruction of the airway. Pulse oximetry revealed that all patients had mild oxyhemoglobin desaturations and that 50% had moderate desaturations.

Anesthesia, Dental↗
PubMed2005

Concordance between capnography and arterial blood gas measurements of carbon dioxide in acute asthma.

STUDY OBJECTIVE: We examine the concordance between end-tidal partial pressure of CO2 (PetCO2) measured by capnography and arterial partial pressure of carbon dioxide (PaCO2) obtained by arterial blood gas in acute asthmatic patients presenting to the emergency department. METHODS: This was a prospective observational cohort study of acutely ill adult asthmatic patients undergoing an arterial blood gas measurement as part of their evaluation. PetCO2 was recorded during exhalation into a capnograph while arterial blood was pulsing in the arterial blood gas tubing. Concordance between PetCO2 and PaCO2 was displayed as a Bland-Altman matrix, using prespecified limits of agreement of +/-5 mm Hg difference between PetCO2 and PaCO2 in each patient. RESULTS: The mean difference between the PetCO2 and PaCO2 levels was 1.0 mm Hg (95% confidence interval -0.1 to 2.0 mm Hg), with a median of 0 mm Hg. Of the 39 patients enrolled, 37 (95%) fell within the a priori limits of agreement. CONCLUSION: In adult asthmatic patients with acute exacerbations, concordance between PetCO2 measured by capnography and PaCO2 measured by arterial blood gas was high. These findings must be validated before capnography replacement of arterial blood gas as an accurate means of assessing alveolar ventilation in acute asthma is recommended.

Acute Disease↗
PubMed1997

Capnography and ventilatory assessment during ambulatory dentoalveolar surgery.

PURPOSE: The purpose of this study was to determine whether capnography is a more sensitive monitor than auscultation of breath sounds in detecting ventilatory changes consistent with hypoventilation, obstruction, or apnea and in detecting ventilatory changes that can be associated with oxygen desaturation. PATIENTS AND METHODS: Fifty-five patients received intravenous agents and supplemental oxygen to achieve a state of deep sedation or general anesthesia for removal of impacted third molars. The surgeon/anesthetist monitored respiratory status using a pretracheal stethoscope and direct observation. A blinded observer with no access to the patient or anesthetist monitored respiratory status using capnography. A second observer monitored all respiratory parameters to allow for correlation between clinical and electronic monitors. RESULTS: Ventilatory status was continuously represented by capnogaphy. The Pearson correlation coefficient showed a positive correlation between increased end-tidal CO2 (PETCO2) and decreased oxygen saturation that became stronger with greater positive changes in PETCO2. An additive relationship was found between PETCO2 and respiratory rate (RR), with increased PETCO2 and decreased RR contributing to decreased oxygen saturation. CONCLUSION: Patients with nasal ventilatory exchange maintain this exchange throughout the anesthesia so that sampling of nasal PETCO2 is an effective way to monitor ventilatory status. Respiratory depression or obstructive ventilatory changes detected by capnography showed a high sensitivity and low positive predictive value in detecting oxygen desaturation. The current technology does not show a clinically satisfactory correlation between PETCO2 and oxygen saturation. However, a combined increase in PETCO2 and decrease in RR suggested a trend of decreasing oxygen saturation.

Adolescent↗
PubMed2003

A prospective randomised controlled trial of capnography vs. bronchoscopy for Blue Rhino percutaneous tracheostomy.

A crucial step for successful percutaneous tracheostomy is the introduction of the needle and guide wire into the trachea. Capnography has recently been proposed as one way to confirm tracheal needle placement. In this randomised controlled study, we used capnography in 26 patients and bronchoscopy in 29 patients to confirm needle placement for percutaneous tracheostomy using Blue Rhino kit. The operating times and the incidence of peri-operative complications were similar for both groups. Capnography proved to be as effective as bronchoscopy in confirming correct needle placement.

Adolescent↗
PubMed2006

Capnography rapidly confirmed correct endotracheal tube placement during resuscitation of extremely low birthweight babies (< 1000 g).

During neonatal resuscitation, the routine use of capnography to verify correct placement of the endotracheal tube is not an established international practice. We present four cases that illustrate the successful use of immediate capnography to verify correct tracheal tube placement even in extremely low birthweight (ELBW) prematures (< 1000 g) during resuscitation. Based on this limited experience, we reached institutional consensus among paediatricians and anaesthesiologists that capnography should become standard monitoring during all endotracheal intubations in premature babies.

Capnography↗
PubMed2003

Use of volumetric capnography to identify pulmonary dysfunction in horses with and without clinically apparent recurrent airway obstruction.

OBJECTIVE: To investigate whether volumetric capnography indices could be used to differentiate between horses without recurrent airway obstruction (RAO) and horses with RAO that were in clinical remission or that had clinically apparent RAO. ANIMALS: 70 adult Swiss Warmblood horses (20 used for pleasure riding and 50 used for dressage or show jumping). PROCEDURE: Horses were allocated to 4 groups on the basis of history, clinical signs, results of endoscopy, and cytologic findings (group 1, 21 healthy horses; group 2, 22 horses with RAO that were in remission; group 3, 16 horses with mild RAO; group 4, 11 horses with exacerbated RAO). Expiratory volume and CO2 curves were recorded by use of a computerized ultrasonic spirometer. Volumetric capnograms were plotted, and derived indices were calculated. RESULTS: Dead-space volume (VD) was calculated by use of the Bohr equation (VD(Bohr)) and for physiologic VD (VD(phys)). Ratios for VD(Bohr) to expiratory tidal volume (VT) and VD(phys) to V(T) as well as an index of effective CO2 elimination were significantly different among groups of horses. Age and use of the horses also significantly affected volumetric capnography indices. CONCLUSIONS AND CLINICAL RELEVANCE: Ratios of VD(Bohr) to VT and VD(phys) to VT as well as an index of effective CO2 elimination were sufficiently sensitive measures to distinguish between healthy horses and horses with RAO in remission. To optimize the ability of volumetric capnography indices to differentiate among horses in heterogeneous populations, it is important to account for effects of age and specific use of the horses.

Aging↗
PubMed1999

Capnography. A key underutilized technology.

Based on the multiple applications and the potential cost savings, every ICU should have enough capnography for all intubations and probably for all mechanically ventilated patients. Of the multiple clinical applications of capnography, most attention should be focused on its use with intubation and resuscitation. Other applications, such as blood gas and ventilation-perfusion scan reduction, should be instituted after the primary areas have been implemented. While capnography modules may appear to be expensive at first glance, an analysis of their clinical application reveals they can save the hospital hundreds of thousands of dollars beyond the purchase price.

Aged↗
PubMedDate not supplied

Capnography: beyond the numbers.

Detecting end-tidal pressure of carbon dioxide (PetCO2) is becoming increasingly common in the emergency transport setting. Several CO2 detection devices are suitable for emergency transport, including colorimetry, capnometry, and capnography. Capnography is the only device that displays a waveform of CO2 levels throughout the respiratory cycle. Analysis of this waveform is key to avoiding therapeutic errors. End-tidal PCO2 is best used for verifying endotracheal and nasal gastric tube placement and assessing the effectiveness of CPR. The use of capnography as a means of guiding manual or mechanical ventilatory therapy is unreliable in unstable, critically ill, or injured patients.

Capnography↗