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At least 451 records · Page 25Linked to original sources
PubMed1993

Absence of a capnogram after positive end-expiratory pressure.

OBJECTIVE: The objective of this study was to evaluate the effect of positive end-expiratory pressure (PEEP) on capnography. DESIGN: The study design was experimental and open, and it was performed in the Anesthesiology Experimental Research Laboratory. METHODS: Six dogs (9.8 +/- 0.8 kg) were anesthetized and intubated. The animals' lungs were ventilated with a tidal volume of 137 +/- 34 ml and a respiratory frequency of 34 +/- 10 breaths/min to produce a PaCO2 of 35 to 45 mm Hg. Application of 20 cm H2O of PEEP was initiated for 1 minute, then repeated twice after 10-minute stabilization periods. Arterial pH and gas tensions were measured, and capnogram, airway gas flow, and airway pressure were recorded continuously. Airway gas flow was electronically integrated to calculate tidal volume. RESULTS: Mean values before application of PEEP were as follows: pHa, 7.37 +/- 0.04 mm Hg; PaCO2, 37.1 +/- 3.2 mm Hg; PaO2, 93.4 +/- 1.6 mm Hg; and PETCO2, 32.0 +/- 3.5 mm Hg. Compliance of the ventilator circuit was 3.3 ml/cm H2O. Mean deflation lung-thorax compliance was 41.5 +/- 10.3 ml/cm H2O. After application of PEEP, no capnogram was reported for 1 to 6 breaths, an average of 2.7 +/- 1.8 breaths. CONCLUSION: These results demonstrated that absence of gas flow immediately after the application of PEEP may transiently abolish a capnogram when the lung volume increases.

Anesthesia, Inhalation↗
PubMed1991

Reduction of fresh gas flow requirements by a circle-modified bain breathing circuit.

We modified a Bain circuit by placing the circuit into the Y piece of a standard carbon dioxide absorber circle, connecting the fresh gas hose on the anesthetic machine to the Bain's fresh gas inlet, and occluding the circle's fresh gas inlet. This circle-modified Bain breathing circuit was studied to evaluate whether it reduces fresh gas flow requirements. The Bain and modified Bain steady states were analyzed by mechanical and computer modeling. The mechanical model consisted of an artificial lung ventilated to steady state. Carbon dioxide was measured with capnography. Computer modeling was by compartmental analysis calculated with spread-sheet software. Steady-state solutions were obtained by numeric analysis. The circle-modified Bain greatly reduced retention of carbon dioxide. For example, with 1-liter tidal volumes, 10-liter minute volumes (10 breaths per minute), and a 2.1 L/min fresh gas flow, the steady-state end-tidal carbon dioxide values of the Bain and modified Bain were 9.3 and 4.6%, respectively, in the physical model (carbon dioxide inflow of 230 ml/min). Results from the mechanical model helped validate the computer model.

Anesthesia, Closed-Circuit↗
PubMed1988

Computer-assisted Doppler monitoring to enhance detection of air emboli.

Currently, two of the most sensitive clinical approaches commonly used to monitor for venous air embolism, i.e., precordial Doppler audio and capnography, require the attention of the anesthesiologist's eye or ear, which is a distraction from other aspects of care. To assess the feasibility of allowing the computer to relieve the necessity for continuous human monitoring, we developed a computer algorithm for monitoring the precordial Doppler audio. This algorithm extracted (1) the amplitude of certain higher-frequency components of the Doppler audio, (2) a measure of the average value of the envelope of Doppler audio, and (3) the ratio between the average value of the Doppler envelope and the amount of envelope signal variation at heart rate frequency and its multiples. These three features were monitored by an adaptive pattern recognition algorithm that compared each new value for each feature with the previously developed mean and standard deviation for that feature. If the changes in the three features exceeded a detection threshold, an alarm (indicating suspected air embolism) was activated. Implemented as a prototype system, the algorithm was given preliminary testing in 2 dogs and activated alarms at levels of air well below those reported to cause clinically significant hemodynamic changes in dogs. While decreasing the distraction for the anesthesiologist, this early prototype alarm system alerts its user to the need for analysis of the Doppler signals when it senses an air embolus.

Algorithms↗
PubMed1987

Now that we have pulse oximeters and capnographs, we don't need precordial and esophageal stethoscopes.

One clinician argues that precordial and esophageal stethoscopes are obsolete. Current technology, including pulse oximetry, electrocardiography, and capnography, is both easier to use and more accurate. Another clinician argues that these stethoscopes have an important place in safe patient management. They are an inexpensive but effective extension of the anesthesiologist's own senses.

Carbon Dioxide↗
PubMed1982

Sitting or prone? Another argument for the latter.

The case is described of a one-year-old child who underwent a craniectomy in the prone position for the removal of an ependymoma of the cerebellar vermis which had invaded the fourth ventricle. Circulatory arrest occurred. External cardiac massage was successfully carried out without any change of position, and the operation was satisfactorily completed. It is suggested that such an outcome would have been less likely had the patient been in the sitting position. The value of capnography as a guide to the adequacy of the circulation is emphasized and illustrated.

Blood Circulation↗
PubMed1994

Effort syndrome: hyperventilation and reduction of anaerobic threshold.

Effort syndrome is an entity in danger of being subsumed into "chronic fatigue syndrome" and lost to sight. Its distinctive feature is the reduction of the anaerobic threshold for work by depletion of the body's alkaline buffering systems through hyperventilation. This article describes the history and clinical features of effort syndrome and reports a study in which capnography is used to identify the anaerobic threshold by registering the respiratory response to the onset of metabolic acidosis. The patients' thresholds are low, and provide a goal for rehabilitation. In other forms of chronic fatigue syndrome, the pathogenesis and logic of therapy are unclear.

Adult↗
PubMed1996

Highlights of the annual meeting of the International Society for the Advancement of Respiratory Psychophysiology and the 14th International Symposium on Respiratory Psychophysiology.

This article provides a review of selected presentations and events that highlighted the annual meeting of the International Society for the Advancement of Respiratory Psychophysiology (ISARP) and the 14th International Symposium on Respiratory Psychophysiology, Toronto, Ontario, Canada, October 1995. The meeting, which was scheduled as a satellite to the 35th annual meeting of the Society for Psychophysiological Research, included two workshops (Diana M. Innocenti on "Identification of Individual Breathing Patterns and Introduction to the Reeducation of Dysfunctional Patterns in Hyperventilation, Asthma, and Emphysema" and Richard N. Gevirtz on "Respiratory and Psychophysiological Factors in the Diagnosis and Treatment of Functional Cardiac and Panic Disorders"), two symposia (one on "Breathing Retraining: Issues and Applications" and one on "Capnography and Hyperventilatory Hemodynamics"), three invited addresses (Hans Folgering on "Rehabilitation of Patients with Exercise Hypoxemia"; David Stubbing on "Assessing Impairment, Disability, and Handicap in Chronic Lung Disease"; and Robert Banzett on "Hypercapnia-Induced Air Hunger"), three panel sessions (one on "Respiratory Psychophysiology of Airway Obstruction," one on "Applied Respiratory Psychophysiology," and one on "Hyperventilation and Panic: Psychological Aspects"), and a poster session.

Congresses as Topic↗
PubMed1996

Congenital central hypoventilation syndrome (Ondine's curse syndrome) in two siblings: delayed diagnosis and successful noninvasive treatment.

UNLABELLED: Congenital central hypoventilation syndrome (CCHS, Ondine's curse syndrome) is a rare respiratory disorder; less than 100 cases have been reported. Familiality of the disease has been discussed, but only few familial cases have been reported so far. In this report we describe the occurrence of CCHS in two male siblings. Diagnosis was established only at the age of 4 years in the first case, although the patient had disease related symptoms since early infancy. The second patient was one of dizygotic twins, he was diagnosed with CCHS at the age of 8 months. Up to that age only moderate desaturations had been observed. The other twin was unaffected by the disease. Both patients were successfully treated by nocturnal positive-pressure ventilation via a specially adapted face mask. They show satisfactory physical and neurologic development. CONCLUSION: Our cases support the assumption of familiality in CCHS although the mode of inheritance remains to be clarified. Polygraphic recordings including capnography should be performed in siblings of CCHS patients early in life in order to avoid secondary complications. Noninvasive treatment by ventilation via special face masks is feasible.

Child↗
PubMed1990

Monitoring at home.

To reduce time committment and expense in the diagnosis of sleep apnea it is necessary to develop simplified monitoring techniques. The monitoring systems to detect apneas should have high sensitivity, good reproducibility, be inexpensive and practical to use. The following methods have been suggested: inductance plethysmography, capnography, flow measurements by thermistors, tracheal sound recording, static charge sensitivity bed, oximetry, activity monitoring, detection of snoring. Some devices to registrate breathing have been combined with oximetry and other methods. The results have been validated by polysomnography and show rather good correlations. However, there exists no information on the time and cost savings of a step wise diagnosis of sleep apnea.

Adult↗
PubMed1990

Monitoring for disconnection: ventilators with bellows rising on expiration can deliver tidal volumes after disconnection.

Anesthesia ventilators with bellows that rise on expiration (standing bellows) are favored over ventilators with bellows that descend during expiration (hanging bellows). Standing bellows will not rise if there is a disconnection, and thus they facilitate detection of disconnections. Yet, during a disconnection of ventilators with standing bellows, mechanical inspiration compresses the empty bellows beyond its resting position; with expiration the elastic bellows recoils and aspirates up to 140 ml, depending upon the fresh gas flow. Tidal volumes recorded after disconnection ranged from 50 to 140 ml (mean, 112.2 +/- 9.22 [SD]) at adult settings and from 55 to 90 ml (mean, 69.8 +/- 4.28 [SD]) at pediatric settings. Thus, spirometers that measure tidal volume (VT) in the expiratory limb of the breathing system may falsely indicate an expiratory VT after a disconnection of the breathing system at the Y-piece or the endotracheal tube. Existing low-pressure alarms and capnography alarms provide redundant warning of disconnection, however, should the ventilator continue to deliver small VTs after a disconnection.

Air Pressure↗
PubMed1990

Respiratory monitoring of carbon dioxide and oxygen: a ten-year perspective.

During the past 10 years, instrumentation has been developed that can continuously and noninvasively measure changes in carbon dioxide and oxygen. The information generated, which cannot be obtained through the human senses, provides vital clinical data regarding the effectiveness of intubation, ventilation, circulation, oxygenation, and the circuit. This instrumentation plays a major role in decision making both in the safe conduct of anesthesia and mechanical ventilation as well as in the detection and prevention of potentially catastrophic mishaps. For these reasons, a review of what has been learned regarding the instrumentation, collection, and interpretation of the clinical data, and the clinical value of the information is timely. The clinical significance of the carbon dioxide and oxygen waveforms, inspired to expired carbon dioxide and oxygen differences, alveolar-arterial gradients, and global supply-to-demand oxygen relationships measured by capnography, oxygraphy, and pulse oximetry are addressed in this essay.

Anesthesia, Closed-Circuit↗
PubMed1990

Observer reliability in detecting surreptitious random occlusions of the monaural esophageal stethoscope.

The esophageal stethoscope is used often during anesthesia to monitor ventilation and cardiac function. Deficiencies in observer vigilance may limit the effectiveness of this monitoring instrument. The aim of this study was to determine how long it took for an observer to detect a surreptitiously occluded monaural esophageal stethoscope in the setting of clinical anesthesia. During routine anesthesia, where an esophageal stethoscope was in use, a computer-guided device would artificially, silently, and at random time intervals, occlude the stethoscope tubing. Personnel using the stethoscope noted when they perceived the absence of stethoscope sounds. We studied 320 stethoscope occlusions in 32 patients. The time between stethoscope occlusion and detection was 34 +/- 59 seconds (mean +/- SD). Eighty-seven percent of detections were made in less than 60 seconds. However, 13% of detections were delayed for more than 60 seconds, and 2.3% for more than 240 seconds. While anesthesia personnel using an esophageal stethoscope could detect most stethoscope occlusions, failure to appreciate such episodes occurred in a small but significant number of cases. This suggests that the esophageal stethoscope has some definite limitations as a continuous monitor and that other monitoring techniques, such as oximetry, capnography, and ventilator disconnect alarms, as well as visual/tactile inspection of the patient, should be used as well.

Anesthesia, General↗
PubMed1986

Do we monitor enough? We don't monitor enough.

The choice of which intraoperative monitors to use for routine cases is difficult, because a multitude of monitors is available today. Monitoring is deemed necessary to avoid problems, although there is little hard evidence that a specific monitor will improve outcome. The risk associated with modern noninvasive monitors, however, is negligible, and they should be considered for routine use in all patients. Although errors in the variables displayed or misuse of correct information can cause difficulties, these result from a lack of education and are not a valid reason to abandon a particular monitoring modality. Regular use of such monitoring tools as the electroencephalogram would allow clinicians to become familiar with how to interpret it in normal and crisis situations. The cost of a disaster during anesthesia (such as unrecognized hypoxia) is high. The dollars spent to cover a single major malpractice award could buy a tremendous number of monitors. The state of the art in the mid-1980s demands traditional anesthesia monitors plus continuous capnography and measurement of peripheral oxygenation. Other negligible-risk monitors should also be used when feasible. Improvement in monitoring design, particularly in output formats and in integration of monitored data, will be essential in the next few years, as will training in the proper use of monitors.

Electrocardiography↗
PubMed1996

Pre-operative oximetry and capnometry: potential respiratory screening tools.

The growing number of patients admitted for outpatient surgery or for same-day admission makes it difficult to obtain thorough pulmonary evaluation. We wanted to evaluate the applicability of pre-operative pulse oximetry and capnography as possible pulmonary screening tools. In this preliminary study, 200 unselected, unmedicated adult patients who were being admitted for surgery were connected to a dual parameter patient monitor (Capnomac Ultima, Datex). A standard adult clip-on finger probe was used for pulse oximetric oxygen saturation. Sidestream capnometry documented the end-tidal carbon dioxide and the capnogram which was recorded for further analysis. In these unmedicated patients, the oxygen saturation ranged from 91 to 99% and was found to be 94% or less in five percent (N = 10) of the cases. The end-tidal carbon dioxide ranged from 21 to 48 mmHg. In five percent of the cases (N = 10) it was found to be 45 mmHg or higher, reflecting elevated arterial CO2. When the shape of the capnogram was rated, it was found normal in 54% of the cases. Slow rising capnogram, indicating mild (N = 84) or moderate (N = 8) airway obstruction was detected in 42% or 4% of the cases respectively. Since pulse oximeter and end-tidal carbon dioxide values are often not measured until after sedation or after induction of anesthesia, patients with pre-operative abnormalities might escape pre-operative detection. In unmedicated patients, routine pre-operative or pre-admission determination of oxygen saturation, end-tidal carbon dioxide and the capnogram may be a valuable screening tool.

Adult↗
PubMed1990

Apnoea and unconsciousness after apparent recovery from alfentanil-supplemented anaesthesia.

Several cases of recurrent respiratory depression progressing to apnoea and unconsciousness after apparent recovery from sufentanil have been reported recently. Alfentanil has the shortest elimination half-time of the narcotics used in anaesthesia, suggesting that it should be the least likely to cause postoperative respiratory depression. A case of recurrent unconsciousness and respiratory arrest after apparent recovery from alfentanil-isoflurane-nitrous oxide anaesthesia is reported. A total dose of 137 micrograms.kg-1 alfentanil was given over a 3.25-hr period to a 45-year-old female undergoing partial gastrectomy. Naloxone, 0.16 mg IV, rapidly restored spontaneous ventilation and consciousness. This case demonstrates that apnoea and unconsciousness can also recur after apparent recovery from alfentanil. Recovery room personnel should be aware of this phenomenon. Earlier detection may permit treatment before apnoea occurs. Patients given narcotic-supplemented anaesthesia should be monitored by capnography and/or pulse oximetry in the early postoperative period.

Adjuvants, Anesthesia↗
PubMed1991

Failure to awaken after general anaesthesia secondary to paradoxical venous embolus.

A patient is presented who failed to regain consciousness after an apparently uneventful nine-hour revision of a total hip replacement. There were no clinically important haemodynamic changes during the operation, and oxygen saturation, capnography and acid base balance were normal throughout. Postop CT of the head showed a large left MCA infarct with midline shift. At autopsy, the patient was found to have a previously unsuspected patent foramen ovale, and a venous embolus in the left internal carotid artery, which probably had originated from the periprostatic venous plexus with a large infarct in the distribution of the left anterior and middle cerebral arteries. The authors conclude that massive paradoxical venous emboli can occur during surgery with minimal haemodynamic changes.

Anesthesia, General↗
PubMed1996

Anaesthetic managements for conjoined twins with complex cardiac anomalies.

PURPOSE: To describe the perioperative assessment and anaesthetic management for surgical separation of three sets of conjoined twins with complex cardiac anomalies threatened with arterial desaturation and haemodynamic instability. CLINICAL FEATURES: Three sets of conjoined twins, one omphaloischiopagus, one omphalopagus, and one thoraco-omphalopagus, were considered for separation during the perinatal or infantile period. Preoperative functional evaluation including continuous pulse oximetry, capnography, and cardiac electrophysiological studies were considered to be as important as anatomical evaluation of the cardiac anomalies and cross-circulation by angiography in assessing the feasibility of surgical separation. Ipsilateral infusion of prostaglandin E1 and phenylephrine were applied to the cyanotic and healthy twins respectively, to restore arterial oxygenation intraoperatively and to avoid profound hypoxaemia. CONCLUSION: Surgical separation and anaesthesia should be well planned and rehearsed before clinical deterioration of the weaker twin. Aggressive pharmacological intervention and understanding of the cross-circulation pathophysiology is necessary to manage critical situations during surgical separation and in the postoperative period.

Anesthesia↗
PubMed1999

[Hemodynamic monitoring using esophageal Doppler ultrasonography during laparoscopic cholecystectomy].

PURPOSE: To evaluate the use of a 4-mHz continuous wave esophageal Doppler monitor in the hemodynamic management of 48 ASA I to III patients undergoing laparoscopic cholecystectomy. METHODS: General anesthesia was induced with fentanyl and propofol, maintained with N20 N20/02 and muscle relaxation was provided with atracurium. The lungs were mechanically ventilated. Non invasive arterial blood pressure, heart rate, capnography, arterial blood gas were monitored during CO2 pneumoperitoneum at 15-mmHg. Using the velocity waveform of descending aortic blood flow, the Doppler device estimated changes in cardiac output and systemic vascular resistances. RESULTS: Peritoneal insufflation resulted in a mean 19% decrease in cardiac output (range -49 to +5%; P < 0.05) and a mean 48% increased in systemic vascular resistances (range -7 to +101%; P < 0.01). There was no relationship between changes in cardiac output and mean arterial pressure or PETCO2. The esophageal Doppler provided, in two patients, details of hypertensive peaks (mean arterial pressure > 140 mmHg) which responded to administration of nicardipine. CONCLUSION: The Esophageal Doppler provided an easy-to-handle and non invasive tool to monitor changes in cardiac output during laparoscopic cholecystectomy. However, further comparison with a thermodilution cardiac output technique is required.

Adult↗