What's New in Critical Illness and Injury Science? The challenge of verifying tracheal airway placement: Solving the puzzle one piece at a time.

Ultrasound (US)-based techniques continue to prove themselves invaluable in an increasing number of clinical areas and patient scenarios.[12345678910] One of the areas where US seems to have been underappreciated, and most certainly underused, is confirmation of successful airway placement [Figure 1].[1112] The article by Drs. Hosseini, Talebian, Ghafari, and Eslami on secondary confirmation of endotracheal tube (ETT) position by diaphragm motion in right subcostal US view, featured in the current issue of IJCIIS, discusses their experience with using US as a secondary adjunct to ETT placement.[13] Hosseini et al. emphasize that US is an easily accessible, convenient, fast, portable, and inexpensive tool that can be used by clinicians at the bedside. The authors further describe the challenges of confirming ETT placement and the limitations of the standard capnography, especially in patients with severe airway obstruction, hypotension, pulmonary emboli, and low cardiac output. Additionally, in resource poor environments, various adjuncts considered by many to be standard and/or mandatory, may not be readily available or accessible. Portable US, in contrast, has been described being used in a variety of settings, from the base camp of Mount Everest to disaster scenarios, to aerospace applications.[4141516] As portable US devices are becoming more prevalent, the number of investigations into how they can help answer important clinical questions is increasing. As with any area of growing scientific inquiry, these new US studies give rise to new questions, doubts, and ultimately advances.

Figure 1

Demonstration of sonographic airway confirmation via direct visualization of the endotracheal (ET) tube within the trachea. (a) High frequency linear array image of transverse airway at larynx. The arrow is pointing to ET tube in airway with reverberations posteriorly; (b) Another image of airway at larynx with high frequency linear array probe used to outline the ET tube; (c) Long axis parasagittal image of the airway using high frequency linear array probe, with direct visualization of the ET tube (arrow)

Hosseini et al. describe a research project based in the Emergency Department at a large teaching hospital where apneic or paralyzed patients needing intubation were studied, excluding patients in cardiopulmonary arrest. Utilizing trained senior Emergency Medicine (EM) residents who received a 1-hour didactic course on US of the upper abdomen, patients were evaluated using portable US machine. As a part of the experimental design, other EM residents skilled in tracheal intubation placed the airway while blinded to the independent sonographer's findings of the upper abdomen and diaphragm. All patients received standard post-intubation evaluation by US.[13] The study presents very interesting overall results based on 57 patients in which 12 esophageal intubations occurred. US-trained EM residents identified 11 of 12 esophageal intubations by performing right subcostal sonographic assessment of diaphragm motion. In brief, post-ETT placement diaphragm motion toward the abdomen was designated as representative of intratracheal intubation, while diaphragm motion toward chest or nonsignificant motion was designated as being suspicious of esophageal intubation.

The use of US as an adjunct in airway management has become more popular since 2004 when Chun et al. described pleural sliding as an adjunct to confirm ETT placement.[14] In that article, the authors acknowledged that in resource poor environments, aerospace settings, noisy environments, and some patient populations, tracheal tube confirmation by traditional criteria may be limited. In these patients, could US be used as an adjunct to confirm successful endotracheal intubation? A growing body of evidence points to an affirmative answer to this question.[111217] In 2007, Sustic reviewed the role of US in airway management and described direct visualization of the trachea with US as well as the pleural sliding that occurs in successful tracheal intubation.[18] Sustic further describes the observed motion of the diaphragm on US, focusing on the paradoxical motion of the diaphragm toward the chest during esophageal intubation. The current study by Hosseini et al. describes this method and quantifies its effectiveness to further confirm correct ETT placement.[13] Because of the focused study population, a degree of caution needs to be exercised when generalizing the study's findings across various patient groups. Specifically, the reliability of the technique outlined by Hosseini et al., has not been quantified in nonparalyzed patients.

A number of clinical paradigms for sonographic confirmation of airway, assessment of breathing, circulatory shock, disaster triage, and neurologic disability have been proposed and diffused into many international venues of care.[412] However, the adoption of US assessment in the critical care setting seems to be proceeding somewhat slower than anticipated, especially in resource-rich environments, mainly due to the abundance of other methods for ETT placement confirmation. Whether primary confirmation through direct visualization of tracheal tube passage through the cords, mist in the ETT, capnography (color change or quantitative), or even auscultation by stethoscope, existing standard algorithms for confirmation of ETT placement are well entrenched. However, even in those resource-rich environments, certain patient groups are uniquely positioned to benefit from US-based airway confirmation, including the morbidly obese and the pediatric patient populations.[1920]

US use should be expanded in the context of new, updated, comprehensive algorithms that optimally utilize a combination of direct tracheal visualization [Figure 1], pleural lung sliding and diaphragm motion to confirm ETT placement. The greatest concern for all clinicians is the lack of prompt recognition of esophageal misplacement of the tracheal tube, which continues to be all-too-often initially mistaken for tracheal intubation. The work by Hosseini et al. brings us one step closer to solving this difficult clinical puzzle. As with most early clinical investigations, this study represents research that focuses on demonstrating the feasibility of a new idea and establishing a foundation for further research. As more refinements are made and more operators begin to use the technique and aggregate data, the true utility of the procedure can be realized. While US may not be the first line assessment after easy tracheal intubations, the wide adoption of US-based protocolized practice will help build the diagnostic confidence among clinician sonographers who will be called upon to determine tracheal versus esophageal intubation in the setting of complicated airway where successful intubation is less certain.

The other important component of this study by Hosseini et al., is the fact that EM residents were trained to obtain the US images. In order to successfully implement US-based airway algorithms, sonographic airway assessment skills will need to be disseminated among emergency physicians and intensivists across a variety of clinical environments. In many resource-rich centers, trained nonphysician sonography technicians operate mainly during regular business hours and are only available for restricted number of indications during nights, holidays, and weekends. The images they obtain are then read by a radiologist or other remote physician. In many instances sonographic technicians incidentally present during emergency situations may not have the necessary training to use the US device outside of their narrow focus of sonographic expertise. We applaud Hosseini et al. for their training program and encourage other institutions to facilitate US training that incorporates physicians who will be providing direct bedside care during critical illness. This study represents a convenience sample obtained in a teaching hospital; yet critically ill patients are encountered across a variety of settings and circumstances. Consequently, sonographic skills involved in airway assessment will require wide dissemination. Teaching of these skills takes relatively little time (1 hour in the Hosseini et al.'s study) so these skills may spread rapidly. The physician's ability to obtain and interpret focused US images without additional logistical support is crucial to the success of these initiatives. The ultimate goal is to bring 24/7 availability of potentially life-saving portable bedside assessment to the critically ill patient requiring tracheal intubation (and other bedside diagnostics/procedures).

We commend Hosseini et al. for this contribution to the literature while recognizing that more work needs to be done in this area. It is clear that sonography is a valuable tool that can be successfully used as an adjunct to confirm ETT placement. Focusing on austere and resource-limited environments, we see development and wider adoption of US-based algorithms to incorporate a variety of critical care and emergency clinical scenarios, including but not limited to cardiopulmonary arrest,[21] hypotension,[22] and critical care emergencies.[323] As ultrasound units become smaller and more affordable, these devices will invariably make their way into more environments and replace older, bulkier, and more expensive equipment. Algorithmic, evidence-based procedural confirmation evolves over time and is a combination of new ideas, championing efforts by pioneers, evidence-based research, and gradual refinement of protocols. Each newly introduced method must be cautiously adopted as one adjunct in the already existing algorithm. The efforts by Hosseini et al. represent a valuable new contribution in the area of sonographic ETT placement confirmation.