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At least 757 records · Page 42Linked to original sources
PubMed2000

Atypical "tails-up" capnograph due to breach in the sampling tube of side-stream capnometer.

OBJECTIVE: An atypical "tails-up" capnograph pattern was noticed in a patient during the use of an accidentally crushed sampling tube with a slit-like hole. We investigated the mechanics involved in the observed capnograph pattern. METHODS: Forty consenting ASA I patients of both sexes presenting for tonsillectomy were included in this study. After intravenous induction of anaesthesia, intermittent positive pressure ventilation (IPPV) using a mechanical ventilator was maintained for 20 min and the capnograph trace, ETCO2, and inspiratory/expiratory sevoflurane were compared using a breached sampling tube and then an intact sampling tube. Similar comparisons were made during spontaneous breathing. RESULTS: During IPPV, an atypical "tails-up" capnograph was noted using the breached sampling tubing. At similar inspiratory sevoflurane (2.0 +/- 0.03) levels, expiratory levels (0.9 +/- 0.03) were significantly lower when using the breached sampling tube than the intact tube (1.7 +/- 0.03). ETCO2 with the breached sampling tube (26.8 +/- 0.30 mmHg) showed significantly lower values than with the intact sampling tube (37 +/- 0.3). During spontaneous breathing, the capnograph was normal in shape with both sampling tubes, but ETCO2 and both insp./exp. sevoflurane levels were lower with the breached sampling tube. CONCLUSION: During IPPV, pressure in the breathing circuit is lower during exhalation, thus allowing air to enter through the slit-like hole in the sampling tube causing erroneously low ETCO2 and expiratory sevoflurane. With inspiration, positive pressure in the breathing circuit, transmitted to the sampling tube, prevents air admixture and the upsurge in CO2 is displayed giving the capnograph an atypical "tails-up" appearance. During spontaneous breathing, since pressure in the breathing circuit barely becomes positive during exhalation and is negative during inspiration, air mixes with the sampled gas during both phases and so the capnograph shape was normal but with lower values for ETCO2, insp./exp. sevoflurane, and nitrous oxide levels. If undiagnosed, this defect in the sampling tube can lead to significant errors in the measurement of inspired and expired gas concentrations.

Adolescent↗
PubMed1996

Recovery of 13CO2 and 14CO2 in human bicarbonate studies: a critical review with original data.

1. In order to establish biological and/or methodological explanations for the wide variability in recovery (50-100%) of labelled CO2 after administration of [13C]bicarbonate or [14C]bicarbonate, 34 human bicarbonate studies involving 480 subjects were analysed, and potential methodological issues were investigated in the laboratory. 2. Overall, continuous infusion studies reported a higher recovery than bolus studies (84 +/- 11% versus 69 +/- 12%; P < 0.001). No significant differences in recovery were found between 14C and 13C studies, children and adults, obese and lean subjects, or rest and exercise (steady state). Higher recoveries were found during feeding than during fasting (84 +/- 8% versus 74 +/- 7%; P < 0.001). Different methods used to analyse the results (0-10%) and different study protocols, which include differences in the duration of infusions and background drift in 13C enrichment (0-10%), contribute to the variability. 3. The laboratory studies suggest multiple sources of potential error, including loss of CO2 from the scintillation fluid (up to > 30%, but only in 14C studies in which the scintillation fluid is not alkalized), diffusion of CO2 through syringes and tubing (0 to > 10%), non-linearity of CO2 analysers (up to 8%), inaccuracies in the measurement of bicarbonate concentrations (13C studies) or the strength of CO2-trapping agents (14C studies; 0-8%). 4. It is concluded that much of the variability in the recovery of labelled bicarbonate is likely to be attributable to methodological differences, and that attention to these will ensure better interpretation of metabolic studies that involve oxidation of carbon-labelled substrates.

Adult↗
PubMed1999

Evaluation of the SCOTI device for confirming blind nasal intubation.

The sonomatic confirmation of tracheal intubation (SCOTI) is a new device used to confirm the correct placement of tracheal tubes. It utilises a sonic technique for recognition of a resonating frequency for detection of tracheal intubation. We compared its predictive value with that of the clinical auscultatory method and a capnograph to confirm 132 blind nasal intubations using three different tracheal tubes [red rubber (n = 82), polyvinyl chloride (n = 33) and RAE preformed nasal (n = 17)]. SCOTI correctly identified 70.8% of intubations and chest auscultation did so 99.2% of times. All results were confirmed using a capnograph. The SCOTI device gave a false-negative value in 37 patients (28%) and a false-positive result in two patients (1.5%). The response time for confirming intubations was 2.5 (1.5) s for the SCOTI, 4.1 (1.1) s for a capnograph and 40 (9.4) s for the auscultatory method. The erroneous results shown by the SCOTI device were highest when polyvinyl chloride tubes with a Murphy's eye were used for intubation. This study shows that this device is not very useful for ascertaining the correct placement of tracheal tubes after blind nasal intubation.

Adult↗
PubMed2000

Difficult airway equipment in English emergency departments.

The need for tracheal intubation in the emergency department is often unpredictable and precipitous in nature. When compared with the operating room, a higher incidence of difficult intubation is observed. There are currently no accepted guidelines with respect to the stocking of difficult airway equipment in the emergency department. We have conducted a telephone survey to determine the availability of equipment for the management of the difficult airway in English emergency departments. Overall, the majority of units held a curved laryngoscope blade (100%), gum elastic bougie (99%) and surgical airway device (98%). Of alternative devices for ventilation, a laryngeal mask airway was kept by 65% of departments, a needle cricothyroidostomy kit by 63% and an oesophageal-tracheal twin-lumen airway (Combitube) by 18%. Of alternative devices for intubation, fewer than 10% held a retrograde intubating kit, intubating laryngeal mask, bronchoscope or lighted stylet. Seventy-four per cent of departments held an end-tidal carbon dioxide detector.

Airway Obstruction↗
PubMed2002

Evaluation of an expired fraction carbon dioxide monitor.

Respiratory monitoring is an important aspect of critical care, especially in neurosurgery and neuro-intensive care. Fixed capnographs are too cumbersome to allow monitoring during patient transport. Recently several portable expired fraction carbon dioxide devices have been developed, but no evaluation of their clinical peformance has been reported. We compared the Criticare POET LT Handheld expired fraction carbon dioxide monitor, in three different settings, to fixed capnographs and arterial blood gas analysis. A methodology for systematic appraisal of end-tidal capnographs is proposed.

Adult↗
PubMed2003

Survey of use of end-tidal carbon dioxide for confirming tracheal tube placement in intensive care units in the UK.

The use of end-tidal carbon dioxide monitoring to confirm the correct placement of a tracheal tube immediately after intubation is mandatory in the operating theatre. Tracheal intubation in critically ill patients can be challenging. Quick and accurate confirmation of tracheal tube placement is essential to minimise complications. This survey explored the use of end-tidal carbon dioxide monitoring to confirm tracheal tube placement in intensive care units in the UK. Questionnaires were sent to either the lead clinician or clinical director of randomly selected general adult intensive care units. One hundred and twenty-seven replies were received from the 215 questionnaires sent (response rate 59%). Twenty per cent of the units did not have an end-tidal carbon dioxide monitor, 20% had one end-tidal carbon dioxide monitor per bed and 60% had one end-tidal carbon dioxide monitor between several beds. Only 50% of the units having an end-tidal carbon dioxide monitor use it to confirm correct tracheal tube placement. Of these 50%, only about a third use it for every intubation. Seventy-two per cent of respondents felt that end-tidal carbon dioxide is well suited to confirm correct placement of tracheal tube in critically ill patients, but 50% did not think that confirmation using end-tidal carbon dioxide should be mandatory for intubations outside the operating theatre. Half of the units not having end-tidal a carbon dioxide monitor cited lack of resources as a reason. In summary, although four in every five intensive care units surveyed have end-tidal carbon dioxide monitors, only a small proportion use them to confirm correct placement of tracheal tube after intubation.

Adult↗
PubMed2003

Mainstream vs. sidestream capnometry for prediction of arterial carbon dioxide tension during supine craniotomy.

We compared the performance of mainstream capnometry as a measure of arterial carbon dioxide tension (Paco2) with sidestream recordings in adult neurosurgical patients undergoing supine craniotomy. Two hundred and forty patients were randomly assigned so that the end-tidal carbon dioxide tension (PEco2) was measured using either a mainstream or sidestream infrared capnometer. All patients received propofol anaesthesia and ventilation was adjusted according to clinical requirement. Arterial blood gas analyses were performed after induction, prior to dural incision, during surgery and before wound closure. Simultaneous haemodynamic and ventilatory parameters were also recorded. For 1007 paired measurements of PEco2 and Paco2 (mainstream, n = 503; sidestream, n = 504), the mean (SD) mainstream arterial to end-tidal carbon dioxide tension difference, 0.64 (0.16) kPa, was smaller than the corresponding sidestream values, 0.99 (0.40) kPa (p < 0.001). The limits of agreement for the mainstream analyser, 0.32-0.96 kPa, were also narrower than the sidestream recordings, 0.19-1.79 kPa (p < 0.001). In both capnometers, the arterial to end-tidal difference in carbon dioxide tension did not change with time. However, there was greater within-patient variation in the sidestream group. Our study showed that mainstream PEco2 provided a more accurate estimation of Paco2 than sidestream measurement.

Adolescent↗
PubMed2000

Accuracy of end-tidal carbon dioxide monitoring using the NBP-75 microstream capnometer. A study in intubated ventilated and spontaneously breathing nonintubated patients.

Arterial carbon dioxide partial pressure measurements using the NBP-75 microstream capnometer were compared with direct PaCO2 values in patients who were (a) not intubated and spontaneously breathing, and (b) patients receiving intermittent positive pressure ventilation of the lungs and endotracheal anaesthesia. Twenty ASA physical status I-III patients, undergoing general anaesthesia for orthopaedic or vascular surgery were included in a prospective crossover study. After a 20-min equilibration period following the induction of general anaesthesia, arterial blood was drawn from an indwelling radial catheter, while the end-tidal carbon dioxide partial pressure was measured at the angle between the tracheal tube and the ventilation circuit using a microstream capnometer (NBP-75, Nellcor Puritan Bennett, Plesanton, CA, USA) with an aspiration flow rate of 30 mL min(-1). Patients were extubated at the end of surgery and transferred to the postanaesthesia care unit, where end-tidal carbon dioxide was sampled through a nasal cannula (Nasal FilterLine, Nellcor, Plesanton, CA, USA) and measured using the same microstream capnometer. In each patient six measurements were performed, three during mechanical ventilation and three during spontaneous breathing. A good correlation between arterial and end-tidal carbon dioxide partial pressure was observed both during mechanical ventilation (r = 0.59; P = 0.0005) and spontaneous breathing (r = 0.41; P = 0.001); while no differences in the arterial to end-tidal carbon dioxide tension difference were observed when patients were intubated and mechanically ventilated (7. 3 +/- 4 mmHg; CI95: 6.3-8.4) compared to values measured during spontaneous breathing in the postanesthesia care unit, after patients had been awakened and extubated (6.5 +/- 4.8 mmHg; CI95: 5. 2-7.8) (P = 0.311). The mean difference between the arterial to end-tidal carbon dioxide tension gradient measured in intubated and non-intubated spontaneously breathing patients was 1 +/- 6 mmHg (CI95: -11-+13). We conclude that measuring the end-tidal carbon dioxide partial pressure through a nasal cannula using the NBP-75 microstream capnometer provides an estimation of arterial carbon dioxide partial pressure similar to that provided when the same patients are intubated and mechanically ventilated.

Aged↗