Portable devices used to detect endotracheal intubation during emergency situations: a review

Advancing the scientific study of prehospital mass casualty response through a Translational Science process: the T1 scoping literature review stage

PURPOSE

The European Union Horizon 2020 research and innovation funding program awarded the NIGHTINGALE grant to develop a toolkit to support first responders engaged in prehospital (PH) mass casualty incident (MCI) response. To reach the projects' objectives, the NIGHTINGALE consortium used a Translational Science (TS) process. The present work is the first TS stage (T1) aimed to extract data relevant for the subsequent modified Delphi study (T2) statements.

METHODS

The authors were divided into three work groups (WGs) MCI Triage, PH Life Support and Damage Control (PHLSDC), and PH Processes (PHP). Each WG conducted simultaneous literature searches following the PRISMA extension for scoping reviews. Relevant data were extracted from the included articles and indexed using pre-identified PH MCI response themes and subthemes.

RESULTS

The initial search yielded 925 total references to be considered for title and abstract review (MCI Triage 311, PHLSDC 329, PHP 285), then 483 articles for full reference review (MCI Triage 111, PHLSDC 216, PHP 156), and finally 152 articles for the database extraction process (MCI Triage 27, PHLSDC 37, PHP 88). Most frequent subthemes and novel concepts have been identified as a basis for the elaboration of draft statements for the T2 modified Delphi study.

CONCLUSION

The three simultaneous scoping reviews allowed the extraction of relevant PH MCI subthemes and novel concepts that will enable the NIGHTINGALE consortium to create scientifically anchored statements in the T2 modified Delphi study.

A Prospective Evaluation of Transverse Tracheal Sonography During Emergent Intubation by Emergency Medicine Resident Physicians

OBJECTIVES

Establishing a definitive airway is often the first step in emergency department treatment of critically ill patients. Currently, there is no agreed upon consensus as to the most efficacious method of airway confirmation. Our objective was to determine the diagnostic accuracy of real-time sonography performed by resident physicians to confirm placement of the endotracheal tube during emergent intubation.

METHODS

We performed a prospective cohort study of adult patients in the emergency department undergoing emergent endotracheal intubation. Thirty emergency medicine residents, who were blinded to end-tidal carbon dioxide detection results, performed real-time transverse tracheal sonography during intubation to evaluate correct endotracheal tube placement.

RESULTS

Seventy-two patients were enrolled in the study. Sixty-eight instances (94.4%) were interpreted as correct placement in the trachea; 4 (5.6%) were interpreted as esophageal, of which 1 was a false-negative finding, therefore conferring sensitivity of 98.5% (95% confidence interval, 92.1%-99.9%) and specificity of 75.0% (95% confidence interval, 19.4%-99.4%) for correct placement. There was no significant difference in accuracy among resident sonographers with different levels of residency training.

CONCLUSIONS

A simple transverse tracheal sonographic examination performed by emergency medicine resident physicians can be used as an adjunct to help confirm correct endotracheal tube placement during intubation. In our cohort, the level of training did not appear to affect the ability of residents to correctly identify the endotracheal tube position.

Predictive Value of Tracheal Rapid Ultrasound Exam Performed in the Emergency Department for Verification of Tracheal Intubation

BACKGROUND

Verification of the correct placement of the endotracheal tube (ETT) has been one of the most challenging issues of airway management in the field of emergency medicine. Early detection of oesophagal intubation through a reliable method is important for emergency physicians.

AIM

The aim of this study was to assess the diagnostic accuracy of tracheal rapid ultrasound exam (TRUE) to assess endotracheal tube misplacement during emergency intubation.

METHODS

This was an observational prospective study performed in the emergency department of the major tertiary referral hospital in the city. We included a consecutive selection of 100 patients. TRUE was performed for all these patients, and subsequently, quantitative waveform capnography was done. The later test is considered as the gold standard.

RESULTS

From our total 100 eligible patients, 93 (93%) participants had positive TRUE results (tracheal intubation) and 7 (7%) patients have negative TRUE results (esophageal intubation). Quantitative waveform capnography report of all 93 (100%) patients who had positive TRUE was positive (appropriate tracheal placement). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of TRUE for detecting appropriate tracheal placement of ETT were 98.9% (95% CI, 93.3% to 99.8%), 100% (95% CI, 51.6% to 100%), 100% (95% CI, 95.1% to 100%) and 85.7% (95% CI, 42% to 99.2%) respectively.

CONCLUSIONS

Performing TRUE is convenient and feasible in many emergency departments and pre-hospital settings. We would recommend emergency units explore the possibility of using TRUE as a method in the assessment of proper ETT placement.

Bias in a prehospital esophageal detector device trial: lessons learned

OBJECTIVES

Our goals were to determine whether selection bias occurred in a prehospital study comparing an esophageal detector device (EDD) to a disposable capnometer for detecting esophageal intubation, and to determine whether such a bias would have changed the study's conclusions about EDD effectiveness.

METHODS

In a study of patients requiring prehospital intubation, we determined the sensitivity, specificity and predictive values of the EDD for detecting esophageal intubation. We then compared intubation success rate in patients who were enrolled in the study (n = 129) to that in eligible patients who were excluded from it (n = 107). After finding that the incidence of failed intubation was higher in the "excluded" group, we used sensitivity and specificity parameters derived from the study population to assess whether EDD test characteristics would differ in studied vs. excluded patients.

RESULTS

The first intubation attempt was successful in 125 of 129 study patients and 76 of 107 excluded patients (97% vs. 71%, p = 0.03), confirming the presence of selection bias. The negative predictive value of the EDD for esophageal intubation was 98% in the study cohort and would have been 77% in patients like those excluded (i.e., difficult intubation cases).

CONCLUSIONS

The high "first attempt" intubation success rate seen in this study was due to selective exclusion of failed intubations. This selection bias led to a clinically important overestimation of the EDD's negative predictive value. Bias may substantially alter the estimations of test accuracy reported in scientific studies. To reduce the chance of unrecognized selection bias in studies of diagnostic tests, investigators must determine whether recruited subjects resemble patients in whom the test will ultimately be used.

End-tidal carbon dioxide concentration monitoring in obstructive sleep apnea patients

PURPOSE

The objective of this study was to investigate the end-tidal carbon dioxide concentration (ETco(2)) monitoring in obstructive sleep apnea (OSA) patients during sleep and to explore whether the ETco(2) value may explain a significant portion of the relationship between ETco(2) value and apnea/hypopnea index (AHI) and nocturnal oxygenation indices.

MATERIALS AND METHODS

Thirty-eight consecutive patients underwent overnight polysomnography and were synchronously monitored for ETco(2) using an microstream capnometer. Mean and maximum values during wake time and different sleep stages were recorded. We grouped 38 OSA patients into 2 subgroups on the basis of their difference of mean total sleep time and wake time ETco(2) [(T - W) ETco(2)]; one group, 20 patients with (T - W) ETco(2) less than 0, and the other group,18 patients with (T - W) ETco(2) greater than 0.

RESULTS

Group with (T - W) ETco(2) less than 0 patients exhibited higher AHI (mean ± SD, 68.58 ± 22.78 vs. 27.61 ± 19.44 events/h) and lower nocturnal oxygenation indices (minimum Sao(2), 67.85 ± 10.08 vs. 82.61% ± 6.07%; mean Sao(2), 91.29 ± 3.31 vs. 95.15% ± 1.88%) compared with the other group.

CONCLUSIONS

In summary, the study provides preliminary data showing that ETco(2) potentially can be used in continuous monitoring of OSA patients. And, (T - W) ETco(2) can indicate the severity of OSA.

Endoscopic intubation of exotic companion mammals

Rabbits, guinea pigs, chinchillas and many other small exotic mammals are not intubated routinely, because intubation requires specialized equipment and is difficult to perfect. Using a face mask for these species solely on the basis that they are unable to regurgitate ignores the numerous other benefits of airway control. This article summarizes the many advantages of endotracheal intubation and the various methods of intubation that have been reported. It introduces endoscopic intubation as a method that overcomes many of the difficulties associated with other methods and describes the equipment needed, how to intubate with an endoscope, how to confirm proper endotracheal tube placement, and possible complications. Over-the-endoscope intubation is discussed in detail, as it appears to provide the most versatile and reliable method of intubating exotic companion mammals.

Analytic Review: Confirmation of Endotracheal Tube Position: A Narrative Review

Endotracheal tube (ETT) insertion is the primary method of definitive airway protection and control in critically ill patients. Detection of ETT malposition in a timely fashion is crucial in both elective and emergent intubation. In this review, we describe classic tests and highlight several new technologies that may assist the practitioner in determining ETT position within the esophago-tracheal complex, namely ultrasonographic and impedance-based methods. Strengths and weaknesses of particular methods are highlighted. Although many physical examination maneuvers have been described, reliance on the physical examination alone is insufficient for confirmation. Touted methods that appear failsafe, such as direct visualization of the ETT traversing the vocal cords have limitations, especially when dealing in the emergency setting accompanying a difficult to visualize airway. While carbon dioxide detection is an excellent confirmatory method, it is not infallible. Esophageal detection devices are useful as an alternative means of confirmation. New methods such as ultrasonic location of the ETT show promise but require further study. The clinician performing ETT insertion should have multiple confirmation methods that allow the practitioner to adapt to a variety of clinical situations, depending on local costs and availability. Finally, when the clinician still has uncertainty, or multiple tests give conflicting results, the availability of bronchoscopy at the bedside to visualize the carina through the ETT is useful.

Detection of malintubation via defibrillator pads

AIM OF THE STUDY

Endotracheal intubation is the preferred method to ensure proper artificial ventilation. Early detection of esophageal intubation is important for an individual patient's outcome. The aim of the study was to see if impedance measurements can be used to detect esophageal intubation, using the impedance measurement system of an experimental defibrillator.

MATERIALS AND METHODS

Patients who died at the emergency department of a tertiary care hospital were eligible to be studied. After death was declared, patients were ventilated with a predefined tidal volume alternately via the conventional tracheal tube and via an additionally tube placed into the esophagus. The lowest and respectively highest median impedance amplitude for the first three ventilations was used as cut-off to calculate predictive values.

RESULTS

We enrolled 10 patients (mean age 65 years (S.D. 14), 7 male) of whom 9 underwent CPR prior to death, 30% of the patients had a BMI>30. Severe lung-edema was present in 2 cases. The lowest tracheal impedance value was 0.736 ohms and the highest esophageal was 0.496 ohms. A ROC curve for this individualised approach gave an area under the curve of 1 (95% CI 0.001, 0.249).

CONCLUSION

There is a large and significant reduction in transthoracic impedance when the tube is malpositioned in the esophagus. It may therefore be feasible to detect malintubation via thoracic impedance changes as an aid to improve the survival of critical ill patients. Further investigations on a larger population are needed.

Use of bedside ultrasonography for endotracheal tube placement in pediatric patients: a feasibility study

OBJECTIVE

The purpose of our study was to evaluate the usefulness of bedside ultrasonography in verifying endotracheal tube placement in the pediatric population.

METHODS

This study consisted of 2 phases. In phase I, subjects were examined while intubated and after extubation to determine the presence of the endotracheal tube by applying each of 2 ultrasound transducers to the cricothyroid membrane. In phase II, pediatric patients were examined in the emergency department during intubation or immediately after intubation to ascertain proper endotracheal tube placement by using bedside ultrasonography. These results were compared with the results obtained with a colorimetric end-tidal carbon dioxide detector and chest radiographs.

RESULTS

Forty-nine and 50 patients (age: 1 day to 17 years) were recruited in the first and second phases of the study, respectively. The endotracheal tube was detected in all 99 patients by using bedside ultrasonography. Two views were required to show accurately the presence of the endotracheal tube in the trachea. Visualization was obtained in all cases, although short necks and cervical collars made the procedure more challenging. The sniffing position allowed for the best acquisition of high-quality images. Our linear transducer provided the best images but, because of its size, it was not ideal when space was limited. Therefore, the curvilinear transducer was used exclusively for phase II. During phase II, the mean times to acquire bedside ultrasonographic images of the endotracheal tube through the cricothyroid membrane and to obtain a chest radiograph were 17.1 seconds and 14.0 minutes, respectively. In 3 cases, bedside ultrasonographic images proved to be invaluable when the colorimetric end-tidal carbon dioxide detector yielded false-negative or equivocal readings.

CONCLUSIONS

Bedside ultrasonography can be used to accurately and rapidly determine the presence of the endotracheal tube within the trachea in pediatric patients.

Detection of oesophageal intubations using cuff pressures in a pig trachea–oesophagus model

BACKGROUND

The cuff pressures may be different in oesophageal and tracheal intubations. We conducted a study to evaluate if cuff pressures of endotracheal tubes (ETTs) could provide information to distinguish tracheal or oesophageal intubations in a pig trachea-oesophagus model.

METHODS

In each preparation of pig trachea-oesophagus model, the trachea and the oesophagus were intubated separately with a cuffed ETT, and the cuff pressures were measured after each 1 ml increment of air (1-10 ml) during inflation. The cuff pressures and the pressure-volume relationships in both intubations were compared.

RESULTS

The cuff pressures of oesophageal intubations were significantly higher than those of tracheal intubations in all comparisons from 1 to 10 ml of cuff volumes (P < 0.05). The cuff pressure-volume curve was steeper in the oesophageal intubation group, and the difference between the two curves was the largest when the cuff volume was 4-5 ml.

CONCLUSIONS

We conclude that the cuff pressures may be useful in detecting oesophageal intubations. This method is faster than other confirmation measures as it can detect inadvertent oesophageal intubations at the time of inflating the cuffs.

End tidal carbon dioxide monitoring in prehospital and retrieval medicine: a review

End tidal carbon dioxide (ETCO2) monitoring is the non-invasive measurement of exhaled CO2. The Intensive Care Society guidelines include (ETCO2) monitoring as one of the objective standards required for monitoring patients in transport, and the American Heart Association recommends that all intubations must be confirmed by some form of ETCO2 measurement. The physiological principles and technology underlying ETCO2 measurement and the clinical indication for its use in the prehospital environment are reviewed. ETCO2 monitoring has been widely established in the prehospital environment and is of particular use for verification of endotracheal tube placement. It is non-invasive and easy to apply to breathing circuits. The units now available are compact and rugged, with extended battery operating times, which are ideally suited for prehospital use and should be considered as an essential item for advanced airway management.

Model-Based Detection of Endobronchial Intubation

To detect endobronchial intubation (EBI) noninvasively in real time, we developed a novel, automated, lumped model-based approach. The model uses routinely monitored airway pressure and flow as inputs. The specificity of the method in detecting EBI was determined by testing events of stiff chest wall (SCW) in the absence of EBI. EBI was induced in 10 anesthetized, paralyzed, and mechanically ventilated mongrel dogs (19-45 kg) by advancing the endotracheal tube into the right mainstem bronchus. The event of SCW was created by wrapping a pressure cuff around the chest. Airway pressure and flow were continuously recorded at the mouth, and respiratory impedance was estimated from these signals. Model parameters were iteratively identified until the root mean square error between the respiratory and model-predicted impedance was minimum. The change in model parameters during EBI from baseline was analyzed. In nine of 10 cases, it was determined that during EBI, the model's compliance element (C1) decreased > or =50% and model's resistance element (R2) changed < or =10-fold from baseline. Testing this rule on 40 cases of SCW, four false positives were obtained. During SCW, R1 and R2 increased, whereas C2 decreased significantly from baseline. This preliminary study is a promising step toward noninvasive, real-time detection of EBI to aid clinicians in decision making.

Advanced cardiac life support before and after tracheal intubation—direct measurements of quality

STUDY HYPOTHESIS

Tracheal intubation should improve the quality of cardiopulmonary resuscitation (CPR) by enabling adequate ventilation without pauses in external chest compressions.

METHODS

Out-of-hospital cardiac arrests of all causes were sampled in this non-randomized, observational study of advanced cardiac life support in three ambulance services (Akershus, London and Stockholm). Prototype defibrillators (Heartstart 4000SP, Philips Medical Systems, Andover, MA, USA and Laerdal Medical AS, Stavanger, Norway) registered all chest compressions via an extra chest pad with an accelerometer mounted over the lower part of sternum and ventilations from changes in transthoracic impedance between the standard defibrillator pads. The quality of CPR was analyzed off-line for 119 episodes. Numbers and differences are given as mean +/- S.D. and differences as mean and 95% confidence intervals.

RESULTS

Chest compressions were not given in cardiac arrest for 61 +/- 20% of the time before intubation compared to 41 +/- 18% after intubation (difference: 20% (16-24%)). Compressions and ventilations per minute increased from 47 +/- 25 to 71 +/- 23 (difference: 24 (19, 29)) and 5.6 +/- 3.7 to 14 +/- 5.0 (difference: 8.7 (7.6, 9.8)) respectively. Four cases of unrecognized oesophageal intubation (3%) were suspected from the disappearance of ventilation induced changes in thoracic impedance after intubation.

CONCLUSION

The quality of CPR improved after tracheal intubation, but the fraction of time without blood flow was still high and not according to international guidelines. On-line analysis of thoracic impedance might be a practicable aid to avoid unrecognized oesophageal intubation, but this area needs further research.

The effect of vinegar on colorimetric end-tidal carbon dioxide determination after esophageal intubation

This study examines the effect of vinegar placement in the stomach on colorimetric end-tidal carbon dioxide (ETCO(2)) determinations after esophageal intubation. Using a blinded, prospective, before and after post-mortem swine model, colorimetric ETCO(2) was determined after aspiration of the stomach contents and after placement of aliquots of saline and vinegar. Data were compiled from 12 swine within 120 min post-mortem. In 12 of 12 trials, the ETCO(2) detector turned yellow, indicating "positive" determination of CO(2), but did not return to "purple" with multiple insufflations with 100% O(2). We conclude that esophageal intubation with a small amount of vinegar in the stomach can cause an irreversible color change of the detector to yellow. Color change indicating the presence of carbon dioxide without subsequent color change back to purple with insufflation with 100% oxygen should arouse suspicion of improper placement of the endotracheal tube.

Terrorism in South Korea

South Korea has experienced > 30 suspected terrorism-related events since 1958, including attacks against South Korean citizens in foreign countries. The most common types of terrorism used have included bombings, shootings, hijackings, and kidnappings. Prior to 1990, North Korea was responsible for almost all terrorism-related events inside of South Korea, including multiple assassination attempts on its presidents, regular kidnappings of South Korean fisherman, and several high-profile bombings. Since 1990, most of the terrorist attacks against South Korean citizens have occurred abroad and have been related to the emerging worldwide pattern of terrorism by international terrorist organizations or deranged individuals. The 1988 Seoul Olympic Games provided a major stimulus for South Korea to develop a national emergency response system for terrorism-related events based on the participation of multiple ministries. The 11 September 2001 World Trade Center and Pentagon attacks and the 2001 United States of America (US) anthrax letter attacks prompted South Korea to organize a new national system of emergency response for terrorism-related events. The system is based on five divisions for the response to specific types of terrorist events, involving conventional terrorism, bioterrorism, chemical terrorism, radiological terrorism, and cyber-terrorism. No terrorism-related events occurred during the 2002 World Cup and Asian Games held in South Korea. The emergency management of terrorism-related events in South Korea is adapting to the changing risk of terrorism in the new century.

Evaluation of a semi-quantitative CO2 monitor with pulse oximetry for prehospital endotracheal tube placement and management

OBJECTIVE

To evaluate three prototype versions of semi-quantitative end-tidal CO2 monitors with different alarm features during prehospital or interfacility use.

METHODS

Subjects were 43 adult, non-pregnant patients requiring intubation, or who already were intubated and required transport. Teams at one AirEvac and seven Advanced Life Support (ALS) paramedic stations were trained in the use of the monitors. Team members at each station evaluated each model for eight days. Participants completed questionnaires following each use.

RESULTS

The monitors performed properly in all cases, but in one case, vomit in the airway adapter tube prevented obtaining a readout. The monitors aided management in 40 of 43 cases (93%); in one, the monitor reading was reported as variable (between 20 and 30 mmHg) although the teams knew the monitors were semi-quantitative; in another, the monitor was not required, but performed properly; and the third was the one in which vomit in the tube prevented a reading. In 26 of 43 cases (60.4%), the monitor was used to confirm endotracheal tube placement (there were no instances of incorrect placement). In all cases, the devices were used to monitor respiration and oxygen saturation. Alarms were audible in the environment, but only preferred in the AirEvac situation. The "breath beep" feature was useful, particularly in patients in whom chest movements during respiration were difficult to observe.

CONCLUSIONS

"Breath beeps" were clearly audible and were a useful feature in all prehospital and transport environments, while audible alarms were desired only in the AirEvac situation. Semi-quantitative CO2 detection is valuable in the ALS/AirEvac environment, even for teams with high intubation success rates.

Capnography alone is imperfect for endotracheal tube placement confirmation during emergency intubation

This analysis primarily sought to determine the effectiveness of end-tidal capnography for tube placement confirmation during emergency airway management. Secondary objectives were validation of the rate of unanticipated esophageal placement during emergency intubation and quantification of the portion of intubations performed in patients with cardiac arrest where capnography is not recommended. The study was performed in two phases. For the primary objective, a meta-analysis was performed on all experimental capnography trials enrolling emergency populations. For the secondary objectives, inadvertent esophageal intubation and cardiac arrest rates were calculated from a large prospective multicenter observational study of emergency intubation cases. Data analysis included calculation of descriptive statistics, sensitivity, specificity, and confidence intervals (CI). Based on 2,192 intubations, a meta-analysis of previous capnography trials resulted in an aggregate sensitivity of 93% (95% CI 92-94%) and an aggregate specificity of 97% (CI 93-99%) for emergency tube placement confirmation. Thus, for emergency capnography use, the false-negative failure rate (tube in trachea but capnography reports esophagus) was 7% and the false-positive rate (tube in esophagus but capnography reports trachea) was 3%. This translates to potential harm for one patient in every 10 treated with capnographic confirmation alone (number needed to harm: 14 for false-negative, 33 for false-positive, and 10 for both). A further literature review demonstrated no sole method of tube placement confirmation is completely foolproof. Of 4,602 consecutive intubations reported to the National Emergency Airway Registry, 4% of emergency intubation attempts resulted in accidental esophageal intubation, and 10% occurred in nontraumatic cardiac arrest patients. During tracheal intubation of critically ill patients, it is concluded that the rate of accidental esophageal tube placement warrants continued improvement in emergency airway techniques. Misidentification of esophageal placement in the emergency setting may occur with capnography. Multiple methods of tube placement confirmation are superior to any single method because no single method has perfect accuracy.

The efficacy of esophageal detector devices in verifying tracheal tube placement: a randomized cross-over study of out-of-hospital cardiac arrest patients

We performed this prospective study to evaluate the efficacy of esophageal detector devices (EDDs), both the bulb and the syringe-type, to indicate positioning of endotracheal tubes (ETTs) in out-of-hospital cardiac arrest patients. Forty-eight adult patients with out-of-hospital cardiac arrest were enrolled. Immediately after tracheal intubation and ETT cuff inflation in the emergency department, the patients were allocated randomly to two cross-over groups. In Group 1 (n = 24), patients underwent a bulb test and a syringe test in sequence. In Group 2 (n = 24), patients underwent a syringe test and a bulb test in sequence. End-tidal carbon dioxide (ETCO(2)) was also monitored. In 56 attempts at tracheal intubation, the bulb, the syringe, and ETCO(2) indicated all eight esophageal intubations. In 48 tracheal intubations, the bulb test correctly indicated 34 tracheal intubations (sensitivity, 70.8%). The syringe test identified 35 tracheal intubations (sensitivity, 72.9%). The results of both tests agreed in 33 tracheal intubations. ETCO(2) was detected in 31 tracheal intubations (sensitivity, 64.6%). No statistical difference was found among the tests. EDDs were less sensitive in detecting tracheal intubation for out-of-hospital cardiac arrest patients. Therefore, proper clinical judgment in conjunction with these devices should be used to confirm ETT placement in these difficult situations.

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.