COMMONLY ASKED QUESTIONS REGARDING ESOPHAGEAL DETECTOR DEVICE TECHNOLOGY:

1.Why should any device be used to confirm endotracheal tube placement?

2. Studies of confirmation devices used during intubation of patients in the field have demonstrated occasional failure of these devices to properly identify proper tracheal placement of endotracheal tubes. For example, ETCO₂ fails to identify tracheal tubes in up to 35% of patients suffering cardiac arrest, and EDD's may fail to fill in morbidly obese patients , or those with substantial fluid in their airways. Given these limitations, why should field providers use these devices?

3. Please address the situations where esophageal detector device technology may fail to identify properly placed endotracheal tubes.

4. If a patient has been ventilated with positive pressure by bag-valve-mask apparatus prior to intubation and has a stomach full of air, would this device not simply aspirate air from the stomach if the endotracheal tube were esophageal?

5. On the same note, what if you ventilate a patient through an esophageal ETT. Does this increase the likelihood of air being briefly in the esophagus and risk a false result?

6. What if you are certain the tube passed through the cords, yet the Esophageal intubation detector fails to fill with air?

7. What advantages and disadvantages does the Esophageal intubation detector have compared to currently available portable end tidal CO₂ monitors?

8. Given the very low incidence of esophageal intubations in the hands of an experienced anesthesiologist, and the several percent nonfilling despite tracheal ETT location found with esophageal intubation detectors, why use it?

9. Address the previous question in relation to prehospital care providers. Is there a need for this device in the field?

10. Some systems are using the Combitube^TM for prehospital airway control in trauma patients. Is there any information regarding this device and esophageal intubation detectors?

Why should any device be used to confirm endotracheal tube placement?

Endotracheal intubation is complicated, and requires proper training, quality assurance and careful clinical judgment to avoid tragic mishaps, regardless of new technology. Though it seems reasonable that ventilating selected patients through an ETT should improve survival, this assumption is flawed if the procedure is done improperly and procedural induced complication rates are frequent. An intubation gone badly almost assures a poor outcome. Yet this procedure is performed across the country, usually with no requirements for confirming ETT location other than the clinical judgment of the intubator, and large variations in the quality of training and case review. All of us know that clinical judgment alone can be misleading. Anesthesiologists, who intubate in relatively ideal conditions (usually) understand this concern and mandate use of alternate methods.

Studies of confirmation devices used during intubation of patients in the field have demonstrated occasional failure of these devices to properly identify proper tracheal placement of endotracheal tubes. For example, ETCO₂ fails to identify tracheal tubes in up to 35% of patients suffering cardiac arrest, and EDD's may fail to fill in morbidly obese patients , or those with substantial fluid in their airways. Given these limitations, why should field providers use these devices?

The technology is imperfect. The error, in my opinion, is to conclude that since confirmation devices are imperfect they are not helpful. Paramedics are talented enough to perform multiple complex tasks and evaluations. They are certainly bright enough to be taught the limitations of certain devices and properly use these devices. In fact, if nothing else, confirmation devices heighten providers awareness of the complexities of intubation and the grave consequences should it be done improperly. These devices force the users to carefully assess every tube that gives them the "wrong answer." It may result in an occasional tracheal tube being removed, but this is better than leaving esophageal tubes. Recent studies have demonstrated an alarmingly high rate (8.4-17%) of undetected esophageal intubations occurring in the field. EMS providers need to ensure they are doing their very best in the serious procedure of endotracheal intubation. Errors are devastating. Some alternative method of identifying tube location should be used in conjunction with clinical judgment to assure the identification of every esophageal ETT.

Please address the situations where esophageal detector device technology may fail to identify properly placed endotracheal tubes.

A specific group of patients account for the vast majority of cases where EDD devices fail to identify proper tracheal tube location, and these cases can often be predicted in advance. One large study on 2140 patients specifically addressed the question of which patients had proper tracheal intubation, but failure of the EDD device to fill. This study found that 85% of the cases were in morbidly obese patients, the remainder in patients with bronchospastic or obstructive disease, pulmonary secretions or mainstem intubations. Similar findings are re-iterated in most studies and editorial letters that address this issue. A proper training model educating EDD users to carefully check tube depth prior to EDD use and to beware of false positive results in specific patients types, such as those listed above, will reduce unnecessary removal of many tracheal placed tubes.

If a patient has been ventilated with positive pressure by bag-valve-mask apparatus prior to intubation and has a stomach full of air, would this device not simply aspirate air from the stomach if the endotracheal tube were esophageal?

This is a frequently asked question, and on initial consideration seems likely. However, if one considers the mechanism of action and the location of the tip of the endotracheal tube in the esophagus the answer becomes more clear. The vacuum applied by the Esophageal intubation detector causes the walls of the esophagus immediately adjacent to the endotracheal tube (ETT) tip to occlude the tube completely. When examining a chest x-ray of a patient with significant gastric air distention, there is not air in the esophagus itself, therefore, air is not aspirated from the esophagus in these situations. This specific question has been addressed both in an animal model and in the OR and does not occur. So far, over 800 esophageal intubations have failed to aspirate air, although in one case vomit was aspirated (a clear indication of a problem with the endotracheal tube). Theoretically, a patient could regurgitate air simultaneously with Esophageal intubation detector aspiration and a false result might occur, though the data demonstrates clearly that if this occurs, it will be an extremely rare event.

On the same note, what if you ventilate a patient through an esophageal ETT. Does this increase the likelihood of air being briefly in the esophagus and risk a false result?

To get the best safety advantages from the Esophageal intubation detector , ETT ventilation prior to use is discouraged due to the risk of gastric distention and subsequent vomiting and aspiration. The labeling recommends caution in any patient vigorously ventilated through the ETT just prior to Esophageal intubation detector use. On the other hand, several authors using bulb type EDD's recommend squeezing the bulb after attachment to the ETT. If the endotracheal tube is esophageal, the air will gurgle out the mouth and down into the stomach and will not affect accuracy. However in tracheal intubations, this air is available for re-aspiration and actually has been demonstrated in one large study to reduce the incidence of false negatives by over half (4.6% down to 2.6%).

What if you are certain the tube passed through the cords, yet the Esophageal intubation detector fails to fill with air?

This device is an adjunct to clinical judgment. It enhances and improves, but does not replace judgment. In such a situation, be very wary of your placement. First check tube depth, position properly and recheck. Oftentimes a mainstem bronchus intubation will prevent proper inflation . Secondly, pull the tube back 1/2 cm and rotate 90 to 180 degrees and recheck since there is the possibility that the distal openings are occluded by the tracheal wall. If air still does not return, use auscultation, revisualization and other means such as ETCO₂ to confirm location. If still unsure, reintubate. Caplan, et al in their review of anesthesia malpractice cases found that half the cases of missed esophageal intubations in the OR were documented to have adequate breath sounds. In these cases, 98% of the patients suffered bad outcomes. Clyburn and Rosen suggest that undetected esophageal intubations may actually be more common in situations where the tube is "seen" to pass the cords, since the intubator is less alert to the possibility of a problem, is subconsciously convinced the ETT is tracheal, and is therefore more complacent . On the other hand, there is an occasional nonfilling in properly placed ETT's, as stated in the text above, so clinical judgment cannot be ignored.

What advantages and disadvantages does the Esophageal intubation detector have compared to currently available portable end tidal CO₂ monitors?

One of the Esophageal intubation detector advantages is that it does not rely on physiologic parameters such a CO₂, so that in the patient with severely compromised physiology (severe hypotension, cardiac arrest) the Esophageal intubation detector maintains accuracy. It offers the safety advantage of immediate identification of tube location without the need to ventilate the tube and risk gastric distention if improperly placed. It also does not require a power source, and its simplicity makes malfunction unlikely. Finally, Esophageal intubation detector is inexpensive, compact, lightweight, durable and has a long shelf life. It fits well in a scrub shirt pocket, crash cart, intubation tray and ambulance kit, making it a cost effective means of ensuring a confirmation device is available for all emergent intubations. EDD's major disadvantage is that it is not a monitoring device and in selected patients, may not accurately identify tracheal tubes [just as ETCO₂ will not properly identify all ETT's ]. Table 1 reviews specific advantages and disadvantages of the Esophageal intubation detector . Table 2 compares esophageal intubation detector s to ETCO₂.

Given the very low incidence of esophageal intubations in the hands of an experienced anesthesiologist, and the several percent nonfilling despite tracheal ETT location found with esophageal intubation detectors, why use it?

This is a very good question. In fact, the incidence of nonfilling after an experienced anesthesiologist intubates will as often mean the tube is tracheal as esophageal (individually dependent). On the other hand, it will greatly heighten awareness and make the intubator very carefully check tube location in these patients since there now is a very high risk that an esophageal intubation is present. There are specific situations, such as poor or non-visualization of the cords (which is not infrequent in trauma patients) and in teaching cases where someone else is intubating, where this technology gives an immediate answer and allows rapid correction prior to ventilation. Though infrequent, vomiting and aspiration can be devastating and this device reduces the risk of such occurrences. Finally, even the best make mistakes. This is an easy mistake to detect if one is careful and compulsive.

Address the previous question in relation to prehospital care providers. Is there a need for this device in the field?

This is a different situation. Systems which collect the incidence of esophageal intubations report 8% or higher initial esophageal intubation rates. In the only prospective prehospital intubation study to date (done in Los Angeles and Orange county California on pediatric patients) the incidence of undetected esophageal intubation was 8.4% with an additional 8-9% tube "dislodgment" after reported proper placement. Orlando, Florida has reported a 17% undetected esophageal intubation rate in the field. There is also a substantial incidence of aspiration in patients who require emergent intubation. Clearly a problem exists. In the prehospital setting, nonfilling of the Esophageal intubation detector implies esophageal location until proven otherwise. Unfortunately, many prehospital systems use nothing other than judgment. This probably accounts for the not infrequent cases of unrecognized esophageal intubations presenting to emergency departments.

Some systems are using the Combitube^TM for prehospital airway control in trauma patients. Is there any information regarding this device and esophageal intubation detectors?

Yes, there is one article. The authors of the article found esophageal intubation detectors to be reliable in distinguishing the location of the distal portion of the Combitube. Based on the result, one can then determine which port to ventilate through. Due to the complexity of the Combitube (two ports for ventilation) the algorithm is slightly more complex than that used for endotracheal tubes. One must be very careful to aspirate from the distal port to ensure accurate results.