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At least 865 records · Page 48Linked to original sources
PubMed2005

Propofol total intravenous anesthesia for MRI in children.

BACKGROUND: The aim of this study was to assess clinical signs of airway patency, airway intervention requirements and adverse events in 100 children receiving propofol total intravenous anesthesia for magnetic resonance imaging, with spontaneous ventilation and oxygenation via nasal prongs. METHODS: Airway patency was clinically assessed and stepwise interventions were performed until a satisfactory airway was achieved. Propofol requirements, vital signs, procedure times and adverse events were also recorded. RESULTS: Ninety-three per cent of children had no signs of airway obstruction when positioned with a shoulder roll only, two required a chin lift, four required an oral airway and one required lateral positioning. The mean propofol induction dose was 3.9 mg.kg(-1) (range 1.8-6.4 mg.kg(-1)). The mean propofol infusion rate was 193 microg.kg(-1).min(-1) (range 150-250 microg.kg(-1).min(-1)). The initial and final mean respiratory rates were 26 and 23 b.min(-1) (P < 0.05). Movement was more likely at lower infusion rates (mean 175 microg.kg(-1).min(-1)). There were no respiratory or cardiovascular complications (calculated risk: 95% CI = 0-3%). The mean time from end of scan to discharge home was 44 min. CONCLUSIONS: This study demonstrates good preservation of upper airway patency and rapid recovery using general anesthetic doses of propofol in children.

Adolescent↗
PubMed2006

Measurement of expired carbon dioxide, oxygen and volume in conjunction with pretest probability estimation as a method to diagnose and exclude pulmonary venous thromboembolism.

BACKGROUND: The classical alveolar pCO(2)-pO(2) relationship predicts that pulmonary embolism (PE) causes a low ratio of pCO(2)/pO(2) at end expiration. Our purpose was to define a simple protocol to collect expired pCO(2)/pO(2) to diagnose PE. Emergency department patients with suspected PE were enrolled. Clinical pretest probabilities for PE were estimated prior to diagnostic testing using the Canadian score and clinicians' unstructured estimate. Patients provided three 30-s periods of tidal breathing, separated by three deep exhalations. Expired pCO(2), pO(2) and breath volume were measured. All patients underwent standardized objective testing for PE including 90-day follow-up. Diagnosis (PE+) required anticoagulation for image-proven PE within 90 days. RESULTS: Of 200 patients enrolled, 178 were included in final analysis (24 PE+). The mean coefficient of variability for the deep-exhaled and end-tidal pCO(2)/pO(2) ratios were 6.8 +/- 6.7 and 7.5 +/- 6.8%, respectively. Mean pCO(2)/pO(2) ratios were stable throughout the collection periods in both methods. When compared with the deep-exhaled ratio, the end-tidal mean ratio demonstrated slightly better diagnostic utility by the area under the receiver operating characteristic curve. The end-tidal ratios were divided into four interval likelihood ratios and coupled with pretest probability from the two methods to generate three sets of posttest probabilities. Receiver operating characteristic analysis demonstrated good overall diagnostic performance (areas under the curves >0.88) for both posttest probability sets. CONCLUSION: This preliminary work demonstrates that the end-tidal pCO(2)/pO(2) averaged from 30 s of breathing can produce clinically relevant likelihood ratios for the diagnosis and exclusion of PE.

Breath Tests↗
PubMed1998

End-tidal carbon dioxide monitoring in emergency medicine, Part 1: Basic principles.

End-tidal carbon dioxide (PetCO2) monitoring is becoming more common in both the ED and the out-of-hospital setting. Its main use has been as an aid when confirming endotracheal intubation. However, since CO2 is intrinsically coupled with states of metabolism, circulation, and ventilation, PetCO2 monitoring along with analysis of its capnographic component is becoming increasingly valuable for other uses in the ED. This article reviews the physiology of CO2, the means by which end-tidal CO2 may be monitored, and the components and analysis of the capnogram.

Capnography↗
PubMed1998

End-tidal carbon dioxide monitoring in emergency medicine, Part 2: Clinical applications.

End-tidal carbon dioxide (PetCO2) monitoring is becoming more common in both the ED and the out-of-hospital setting. Its main use has been as an aid when confirming endotracheal intubation. Other uses in the ED include monitoring CPR efforts and monitoring the ventilatory and hemodynamic status of intubated and nonintubated patients. In addition, future uses may include using PetCO2 as an adjunct when monitoring the status of asthma treatment, when making the diagnosis of pulmonary embolism, and when measuring cardiac output noninvasively. This article reviews these specific uses of PetCO2 monitoring in emergency medicine.

Capnography↗
PubMed2002

End-tidal carbon dioxide monitoring during procedural sedation.

OBJECTIVE: To prospectively determine whether end-tidal carbon dioxide (ETCO2) monitors can detect respiratory depression (RD) and the level of sedation in emergency department (ED) patients undergoing procedural sedation (PS). METHODS: This was a prospective observational study conducted in an urban county hospital of adult patients undergoing PS. Patients were monitored for vital signs, depth of sedation per the physician by the Observer's Assessment of Alertness/Sedation scale (OAA/S), pulse oximetry, and nasal-sample ETCO2 during PS. Respiratory depression was defined as an oxygen saturation <90%, an ETCO2 >50 mm Hg, or an absent ETCO2 waveform at any time during the procedure. The physician also determined whether protective airway reflexes were lost during the procedure and assisted ventilation was required, or whether there were any other complications. Rates of RD were compared with the physician assessment of airway loss and between agents using chi-square statistics. Spearman's rho analysis was used to determine whether there was a correlation between ETCO2 and the OAA/S score. RESULTS: Seventy-four patients were enrolled in the study. Forty (54.1%) received methohexital, 21 (28.4%) received propofol, ten (13.5%) received fentanyl and midazolam, and three (4.1%) received etomidate. Respiratory depression was seen in 33 (44.6%) patients, including 47.5% of patients receiving methohexital, 19% receiving propofol (p = 0.008), 80% receiving fentanyl and midazolam, and 66.6% receiving etomidate. No correlation between OAA/S and ETCO2 was detected. Eleven (14.9%) patients required assisted ventilation at some point during the procedure, all of whom met the criteria for RD. Pulse oximetry detected 11 of the 33 patients with RD. Post-hoc analysis revealed that all patients with RD had an ETCO2 >50 mm Hg, an absent waveform, or an absolute change from baseline in ETCO2 >10 mm Hg. CONCLUSIONS: There was no correlation between ETCO2 and the OAA/S score. Using the criteria of an ETCO2 >50 mm Hg, an absolute change >10 mm Hg, or an absent waveform may detect subclinical RD not detected by pulse oximetry alone. The ETCO2 may add to the safety of PS by quickly detecting hypoventilation during PS in the ED.

Adult↗
PubMed1998

Comparison of disposable circle and 'to-and-fro' breathing systems during anaesthesia in dogs.

Low-flow anaesthesia is beneficial in terms of reducing atmospheric pollution with waste anaesthetics and improving economy. This study compared a disposable circle and a 'to-and-fro' breathing system at low fresh gas flows (10 ml/kg/minute) in 19 dogs undergoing ovariohysterectomy. Ten dogs were assigned to the circle and nine to the to-and-fro breathing system. Fractional inspired halothane, end-tidal carbon dioxide and halothane were higher and mean blood pressure was lower in dogs using the to-and-fro system, possibly indicating an increased anaesthetic depth in this group. Use of both systems resulted in an elevated inspired carbon dioxide level, although this was significantly lower in the circle system. Further work will be required to determine the clinical relevance of this difference and whether rebreathing can be eliminated by higher fresh gas flows. The disposable circle studied may be used safely in dogs.

Anesthesia, Inhalation↗
PubMed2006

Monitoring of vital signs during dental care.

Advances in medicine have greatly increased the survival of patients with severe health problems and have significantly prolonged life in elderly individuals with systemic disorders. Concomitant advances in dentistry and evolving societal expectations regarding dental health and function have likewise ensured that these patients are increasingly retaining their teeth and/or seeking dental care. The administration of local anaesthetics and the performance of extensive dental procedures may cause stress and systemic disturbances in such patients. In order to avoid potentially serious reactions, dentists are obligated to monitor continuously their medically challenged patients. Monitoring provides three important benefits. First, it helps the dentist detect acute medical emergencies that may require an immediate response. Second, monitoring may reveal gradual deleterious trends that can often be easily reversed before a true emergency occurs. Third, monitoring can assist the dentist in evaluating the efficacy of any emergency treatments or preventive measures that are rendered. The purposes of this article are to: briefly review monitoring techniques and devices, discuss their suitability for use in the dental office, and provide some tips for their application during dental care. In overall decreasing order of routine importance, monitoring resources include the following: responsible personnel, non-invasive blood pressure monitor, pulse oximeter, ECG, and the pretracheal stethoscope or capnograph.

Blood Pressure↗
PubMed1998

Clinical assessment of gas exchange in mature horses.

There are limited methods of assessing pulmonary function in horses at rest. We developed clinical techniques to measure gas exchange efficiency in horses and evaluated 3 groups of horses that were 1) asymptomatic based on auscultation with rebreathing, transtracheal aspirate cytology, and thoracic radiographs (n = 6), 2) asymptomatic at rest but symptomatic with rebreathing (n = 11) and 3) symptomatic at rest (n = 9). Blood samples were obtained from the transverse facial artery and jugular vein. Maximal end-tidal CO2 tension (PETCO2) was measured by an infrared capnograph through a facemask. Alveolar O2 tension, dead space fraction (V(D)/V(T)), and physiological shunt fraction (Q(S)/Q(T)) were calculated using standard formulae. Arterial O2 tension in Group 1 horses (mean +/-s.d.103+/-3 mmHg) was significantly higher than in Group 2 or Group 3 horses. Q(S)/Q(T) in Group 1 horses (0.37+/-0.98%) was significantly lower than in Group 2 and Group 3 horses. Mean +/-s.d.V(D)/V(T) in Group 1 horses (-18.2+/-3.1) was significantly lower than Group 3 horses but not Group 2 horses.

Aging↗
PubMed2005

Monitoring of end tidal carbon dioxide and transcutaneous carbon dioxide during neonatal transport.

OBJECTIVE: To assess the accuracy of measurements of end tidal carbon dioxide (CO2) during neonatal transport compared with arterial and transcutaneous measurements. DESIGN: Paired end tidal and transcutaneous CO2 recordings were taken frequently during road transport of 21 ventilated neonates. The first paired CO2 values were compared with an arterial blood gas. The differences between arterial CO2 (Paco2), transcutaneous CO2 (TcPco2), and end tidal CO2 (Petco2) were analysed. The Bland-Altman method was used to assess bias and repeatability. RESULTS: Petco2 correlated strongly with Paco2 and TcPco2. However, Petco2 underestimated Paco2 at a clinically unacceptable level (mean (SD) 1.1 (0.70) kPa) and did not trend reliably over time within individual subjects. The Petco2 bias was independent of Paco2 and severity of lung disease. CONCLUSIONS: Petco2 had an unacceptable under-recording bias. TcPco2 should currently be considered the preferred method of non-invasive CO2 monitoring for neonatal transport.

Blood Gas Monitoring, Transcutaneous↗
PubMed2004

End tidal carbon dioxide as a predictor of the arterial PCO2 in the emergency department setting.

OBJECTIVES: Patients arriving in the emergency department (ED) need rapid and reliable evaluation of their respiratory status. Mainstream end tidal carbon dioxide (ETCO(2)) is one of the methods used for this purpose during general anaesthesia of intubated patients in the operating theatre. Sidestream ETCO(2) (SSETCO(2)) might be a non-invasive, rapid, and reliable predictor of arterial Pco(2) in non-intubated patients in respiratory distress. The aim of this study was to verify whether SSETCO(2) can accurately predict the arterial Pco(2) and to detect variables that may affect this correlation. METHODS: A prospective semi-blind study. The participants were 73 patients (47 men, 26 women) referred to the ED for respiratory distress. Arterial blood gas pressures and SSETCO(2) measurements were performed and recorded for all patients. Other parameters recorded were: age; body temperature; respiratory rate; blood pressure; pulse rate; and medical diagnosis. RESULTS: A significant correlation was found between SSETCO(2) and arterial Pco(2) (r = 0.792). Compared with the correlation curve of the whole group, age under 50 years deflected the correlation curve to the left, while temperature above 37.6 degrees C deflected it to the right. The rest of the parameters had no clear influence on the SSETCO(2)/Pco(2) correlation curve. CONCLUSIONS: There is a good correlation between SSETCO(2) and arterial Pco(2) in the ED setting. Young age may increase the arterial Pco(2)/SSETCO(2) gradient while raised temperature may decrease this gradient. Further studies are needed to confirm these findings in the normal healthy population.

Adolescent↗
PubMed2000

Measurement of carbon dioxide production in very low birth weight babies.

BACKGROUND: CO2 production is most commonly measured by using indirect calorimetry to quantify elimination of CO(2) in breath (VCO2). An alternative is to measure the rate at which CO2 appears in the body pool (RaCO2) by infusing a (13)C labelled bicarbonate tracer. VCO2 and RaCO2 generally differ but are related by c, a factor that adjusts for the incomplete recovery of infused tracer in the breath. The literature relating to human studies cites a wide range of values for c but the only neonatal study to determine c empirically estimated a mean value of 0.77. AIM: To estimate fractional recovery rate, c, in very low birthweight babies, and assess the feasibility of using the isotopic technique to measure CO2 production during mechanical ventilation. METHOD: Eleven spontaneously breathing, continuously fed, very low birthweight infants (median birth weight 1060 g, median gestational age 29 weeks) were studied. RESULTS: Mean (SD) VCO2 was 9.0 (2.0) ml/min (standard temperature and pressure dry, STPD) and mean (SD) RaCO2 was 9.6 (2.1) ml/min (STPD). The mean (SD) value of c was estimated as 0.95 (0.13). The 95% confidence intervals of the mean were 0.87-1.03. CONCLUSIONS: The results emphasise the importance of measuring c for a given study population rather than assuming a value based on adult studies. The close approximation of RaCO2 and VCO2 in this group of babies implies that the labelled bicarbonate infusion technique could be used to measure simply CO2 production during mechanical ventilation.

Breath Tests↗
PubMed1997

Effect of measurement conditions on measured levels of peak exhaled nitric oxide.

BACKGROUND: It is possible to measure nitric oxide (NO) levels in exhaled air. The absolute concentrations of exhaled NO obtained by separate workers in similar patient groups and normal subjects with apparently similar techniques have been very different. A study was undertaken to determine whether changes in measurement conditions alter the concentration of exhaled NO. METHOD: NO concentrations measured by a chemiluminescence analyser (Dasibi Environmental Corporation) and carbon dioxide (CO2) measured by a Morgan capnograph were analysed in single exhalations from total lung capacity in healthy volunteers (mean age 35.9 years). Ten subjects performed five exhalations at four different expiratory flow rates, at four different expiratory mouth pressures, and before and after drinking hot (n = 5) or cold (n = 5) water. Three subjects performed five exhalations on a day of high background NO (mean NO level 134 ppb) before and after a set of five exhalations made while both the subject and analysers were sampling from a low NO/NO-free reservoir system. RESULTS: The mean peak concentration of NO decreased by 35 ppb (95% CI 25.7 to 43.4) from a mean (SE) of 79.0 (15.5) ppb at an expiratory flow rate of 250 ml/min to 54.1 (10.7) ppb at 1100 ml/min. The mean peak concentration of NO did not change significantly with change in mouth pressure. The mean (SE) peak NO concentration decreased from 94.4 (20.8) ppb to 70.8 (16.5) ppb (p = 0.002, 95% CI 12.9 to 33.1) with water consumption. The mean NO concentration with machine and subject sampling from the low NO reservoir was 123.1 (19.4) ppb, an increase from results obtained before (81.9 (10.2) ppb, p = 0.001, 95% CI -19.9 to -62.7) and after (94.2 (18.3) ppb, p = 0.017, 95% CI 6.0 to 51.8) sampling with high ambient NO. CONCLUSIONS: The measurement of exhaled NO must be performed in a carefully standardised manner to enable different teams of investigators to compare results.

Adolescent↗
PubMed2000

MR imaging and cardiac pacemakers: in-vitro evaluation and in-vivo studies in 51 patients at 0.5 T.

PURPOSE: To evaluate the safety and feasibility of magnetic resonance (MR) imaging at 0.5 T in patients with implanted cardiac pacemakers. MATERIALS AND METHODS: Twenty-one models of pacemakers and 44 pacemaker electrodes were exposed to in vitro MR imaging with continuous registration of pacemaker output and temperature at the lead tip. Prior to MR imaging examination, pacemakers were programmed to an asynchronous mode (A00, V00, or D00). Pacemakers were examined before and after MR imaging. Forty-four patients with implanted pacemakers underwent 51 MR imaging examinations under cardiologic surveillance, continuous electrocardiography, pulse oximetry, and capnographic monitoring. RESULTS: MR imaging was safely performed in all patients. None of the pacemakers displayed a pacing dysfunction at MR imaging. No changes occurred in the programmed parameters in any device tested in vivo or in vitro. Maximum increases in the temperature at the lead tips were 8.90 degrees C at a specific absorption rate (SAR) of 0.6 W/kg and 23.50 degrees C under a worst-case radio-frequency (RF) heating condition with an SAR of 1.3 W/kg. CONCLUSION: MR imaging at 0.5 T can be safely performed in patients with implanted pacemakers in carefully selected clinical circumstances when appropriate strategies (programming to an asynchronous mode, adequate monitoring techniques, limited RF exposure) are used.

Capnography↗
PubMed2001

A method of reconstruction of clinical gas-analyzer signals corrupted by positive-pressure ventilation.

The use of sidestream infrared and paramagnetic clinical gas analyzers is widespread in anesthesiology and respiratory medicine. For most clinical applications, these instruments are entirely satisfactory. However, their ability to measure breath-by-breath volumetric gas fluxes, as required for measurement of airway dead space, oxygen uptake, and so on, is usually inferior to that of the mass spectrometer, and this is thought to be due, in part, to their slower response times. We describe how volumetric gas analysis with the Datex Ultima analyzer, although reasonably accurate for spontaneous ventilation, gives very inaccurate results in conditions of positive-pressure ventilation. We show that this problem is a property of the gas sampling system rather than the technique of gas analysis itself. We examine the source of this error and describe how cyclic changes in airway pressure result in variations in the flow rate of the gas within the sampling catheter. This results in the phenomenon of "time distortion," and the resultant gas concentration signal becomes a nonlinear time series. This corrupted signal cannot be aligned or integrated with the measured flow signal. We describe a method to correct for this effect. With the use of this method, measurements required for breath-by-breath gas-exchange models can be made easily and reliably in the clinical setting.

Algorithms↗