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.
Emergency endotracheal intubation is a daily and vital part of the practice of pediatric emergency medicine. The standard method for confirmation of endotracheal tube (ETT) placement is direct laryngoscopy, with the assistance of careful clinical examination and colorimetric end-tidal carbon dioxide detectors (CECDs). Chest radiographs obtained immediately after intubation are used to assess ETT depth, especially when direct laryngoscopy and clinical determination are difficult and the CECD results are equivocal. In some instances, however, access to immediate postintubation chest radiographs may be hampered for a multitude of reasons.
CECDs are used for rapid ascertainment of ETT placement; however, they have limitations.1 CECDs have a shelf-life of ∼15 months, and they can be damaged by mucus, gastric contents, or epinephrine saturation of the pH-sensitive membrane.2,3 False-negative readings (ie, failure to detect carbon dioxide despite correct placement of the ETT in the trachea) occur during circulatory arrest, when carbon dioxide-rich blood is not reaching the lungs to allow for expiration of the carbon dioxide.1 Similarly, false-negative outcomes can result in the erroneous diagnosis of esophageal intubation with the absence of ventilation, attributable to severe bronchospasm or kinked ETTs.4,5 Ingestion of carbonated beverages or positive-pressure ventilation with a bag-valve mask may result in increased carbon dioxide levels within the stomach, which in turn can result in false-positive color changes.6 The latter can be avoided by assessing the pH membrane after 6 breaths. CECDs do not confirm the exact location of the ETT but imply that the tube is near a carbon dioxide-rich source, as is the case when the ETT is located near the cords but not necessarily through the cords.7 There is a need for an adjunctive method for ETT placement confirmation. Ideally, the method for confirming appropriate ETT placement in an emergency setting should be rapid, noninvasive, simple, and objective. Bedside ultrasonography (BUS) possesses these qualities.
The literature is sparse with regard to well-controlled studies using ultrasonography for ETT placement. Drescher et al8 performed a nonblinded, prospective, comparative study using BUS to note the differences between tracheal intubation and esophageal intubation in cadavers and intubated adult ICU patients. The presence or absence of a “comet head and tail” in the trachea determined whether a patient was intubated appropriately. Raphael and Conard9 showed the utility of ultrasonographic confirmation of ETT placement but also used ultrasonography to detect the foam- or saline-filled cuffs. Slovis and Poland10 and Lingle11 both demonstrated in small case series in neonates that ETT position could be identified by using the arch of the aorta. Hsieh et al12 used thoracic sonography to determine the depth of ETT insertion by imaging the motion of the diaphragm. Similarly, Chun et al13 and Weaver et al14 used the ultrasound sliding lung sign to confirm the depth of ETT placement. Given the existing literature regarding the use of BUS for ETT placement, we chose to evaluate the efficacy of BUS in identifying ETT placement in a pediatric population.
Design and Study Population
This 2-part study was conducted in the PICU and emergency department (ED) of an urban, tertiary care, children's hospital from January 2005 through June 2006. Phase I, a convenience, case series-based study, occurred in the PICU with previously intubated subjects. Phase II, a convenience, nonblinded, prospective study, occurred in the pediatric ED with newly intubated patients. All investigators were trained in the use of the ultrasound instrument at the American College of Emergency Physicians-sponsored ultrasonography course in Columbus, Ohio. They then had ≥1 year of experience and were credentialed through a program established by our department of radiology. The institutional review boards at the University of Tennessee Health Sciences Center (Memphis, TN) and LeBonheur Children's Medical Center approved the protocol.
For phase I, we approached a total of 50 subjects and enrolled 49. The participant's parent or legal guardian gave written informed consent. Phase I of the study included PICU patients between the ages of 1 day and 17 years who underwent ETT placement by our PICU/ED physicians or anesthesiologists or were intubated in the field or at another hospital.
For phase II, 50 patients were approached and enrolled in the study. In phase II of the study, only patients between the ages of 1 day and 17 years who underwent ETT placement by pediatric ED physicians were recruited. During phase II, emergency consent, as stipulated by our institutional review board approval, was obtained from 16 families and patients before intubation, where appropriate, and from 34 families after their respective family members had been intubated.
Subjects underwent intubation because of cardiorespiratory arrest, respiratory distress (secondary to asthma, pneumonia, apnea, or seizure activity), or altered mental status, for preparation for a surgical procedure, or for protection of the airway. Subjects whose conditions were too unstable to allow BUS, who were known to be allergic to the ultrasound gel, or who were ≥18 years of age were excluded from the study. In phase II, an investigator was contacted after a treating physician made the decision to intubate the patient. Therefore, the decision to intubate was made independent of the study.
BUS was performed by using a Sonosite Titan ultrasound instrument (Sonosite, Bothell, WA). We observed the ETT through the cricothyroid membrane (CTM) by using 2 different probes. A high-frequency, linear transducer (HFLT) (25 mm, 10 MHz) and a low-frequency, curvilinear transducer (LFCT) (11 mm, 5–8 MHz) captured images in both the transverse and longitudinal (or sagittal) views. All images were saved onto a compact flashcard.
Depending on the phase of the study, an attending physician from the ICU, ED, or anesthesiology department determined the need to intubate the patient. The investigators examined each subject before, during, or after intubation, to determine the Mallampati classification.15 Subjects were intubated by using standard methods, and the intubating physician confirmed ETT placement via direct laryngoscopy, auscultation, clinical examination, and use of a CECD (Nellcor, Pleasanton, CA).
To acquire the image of the ETT, we identified the CTM, placed the ultrasound transducer over the CTM, and imaged the ETT by using the HFLT and/or LFCT in the transverse and longitudinal (or sagittal) axes. Direct pressure was placed on the CTM by using the ultrasound transducer, to reduce the likelihood that air would obscure the view of the ETT. During phase I, confirmation of ETT placement was performed in the PICU up to 24 hours after intubation and then after extubation, by using both transducers. During phase II, confirmation with BUS was performed during or immediately after intubation in the ED. The LFCT was found to be most versatile, given the results of phase I, and was used exclusively during phase II. The use of BUS did not delay the care of the patient in any instance. Depending on the phase of the study, portable chest radiographs were obtained either before or after the BUS examination.
The primary objective in phase I was to assess the feasibility of using BUS to acquire high-quality images of the ETT. To assess which variables most affected our ability to acquire a good BUS image of the ETT in the trachea, each of the 2 ultrasonographers (Drs Galicinao and Godambe) determined the ease of obtaining an image by using an “ease scale,” which was based on a Likert scale. The ease of measuring the size of the CTM and of obtaining images from that view was determined by using a scale of 1 to 10, with 10 being the easiest. All images were then compared with those obtained after the subjects were extubated. We also measured the length and width of the CTM by using digital calipers (Stewart-MacDonald, Athens, OH) and calculated the surface area of the CTM.
In phase II, the primary objectives were to confirm ETT placement in patients in the ED by using BUS and to compare the results with methods considered the standard of care, namely, CECD and chest radiograph. We also compared the length of time needed to complete the BUS examination and to obtain a chest radiograph. The time needed to complete a BUS examination, from the time the ultrasound examination was initiated to the point at which clear longitudinal and transverse images were obtained, was measured by a recording nurse with a digital stopwatch. The time needed to obtain a chest radiograph was measured from the time it was ordered to the point at which the chest radiograph was actually obtained.
Secondary variables consisted of the following: demographic data, including the subject's age, race, and gender; significant medical history, including prematurity; history of previous intubations; reason for intubation; size of ETT; and American Society of Anesthesiologists16 and Mallampati15 classifications. Statistical analyses were performed by using SAS/STAT 9.1.3 software (SAS Institute, Cary, NC).
Table 1 shows the demographic data for our subjects. Our sample populations for the 2 phases had ethnic compositions that represented accurately our hospital's surrounding population. The mean ages were 4.0 and 3.8 years for phases I and II, respectively, with an age range of 1 day to 17 years. American Society of Anesthesiologists and Mallampati classifications ranged from I to III and from I to II, respectively. Overall, ETT sizes ranged from 2.5 to 7 mm, with 65% being uncuffed tubes and 35% being cuffed tubes. The mean surface area of the CTM, which was measured in phase I only, was 98.9 mm2 (range: 8.95–483 mm2).
For phase I, we obtained images of the ETT through the CTM by using the HFLT and LFCT in transverse and longitudinal views. In the transverse view, the presence of a comet head and tail confirmed the presence of the ETT (Fig 1A). In the longitudinal view, 2 bold parallel lines represented the ETT (Fig 1B). For each patient, a chest radiograph ultimately confirmed the depth of insertion. After successfully observing and identifying endotracheal intubations for all 49 subjects, we compared the findings with those obtained after extubation.
The 2 investigator-ultrasonographers assessed the first 10 patients independently, with a resulting κ correlation coefficient of 0.91. There was no correlation (with the Pearson correlation coefficient) between the ease of imaging and the patient's age, patient's weight, CTM surface area, or ETT size, using either of the 2 ultrasound transducers.
Subjects with subjectively shorter necks and those with small cervical collars (4 and 2 of 49 patients, respectively) proved to be most difficult to image. Although the HFLT provided good images, because of its “hockey stick” shape it was not ideal in circumstances where space was limited. Despite this, images were eventually successfully acquired with both transducers in all instances.
In all except 1 case, the absence of both the comet head and tail in the transverse view and the bold parallel lines in the longitudinal view signified an empty trachea in the extubated subject. The 1 exceptional case involved a 7-month-old male infant who underwent imaging after extubation. His transverse view, obtained after extubation, revealed a comet tail. It is likely that the large transducer depicted the infant's relatively small tracheal ring as a comet tail17 or the finding was an exaggerated periodic resonance artifact, as described by Drescher et al.8 However, 2 bold parallel lines were not evident in the longitudinal view for this extubated patient. Therefore, the acquisition of 2 views is crucial for the successful confirmation of ETT placement.
After completion of the first phase of the study, the second phase was initiated. Its primary objectives were to confirm ETT placement in patients in the ED by using BUS and to compare the results with those obtained with the CECD and chest radiography. Fifty patients were recruited for phase II of the study. The mean time to obtain a chest radiograph, from the time it was ordered to the moment it was obtained, was 14.0 minutes (95% confidence interval: 12.3–15.8 minutes). The mean time to complete a BUS examination with the LFCT to confirm ETT placement through the CTM was 17.1 seconds (95% confidence interval: 12.9–21.2 seconds). BUS confirmed ETT placement in all cases as determined through chest radiographs and clinical examinations, with resulting sensitivity, specificity, positive predictive value, and negative predictive value of 100% (Table 2). However, the CECD failed to detect proper ETT placement in 2 cases and did not clearly detect improper placement in a third case. The sensitivity, specificity, positive predictive value, and negative predictive value for the CECD were 95%, 100%, 100%, and 33%, respectively. BUS proved to be crucial for the rapid confirmation of proper ETT placement for those 3 patients.
The first patient was a 2-month-old male infant who was intubated because of prolonged apnea after a bout of emesis with possible aspiration. A pediatric resident performed the initial intubation attempt. The CECD showed a pale tan color change, and there was no visible chest rise. When the BUS examination suggested that the ETT was in the esophagus, the attending ED physician quickly reintubated the patient. The BUS examination was able to confirm proper placement of the ETT, as well as the orogastric tube.
The final 2 patients were a 17-year-old, male patient in status asthmaticus and a 3-month-old, formerly premature (30 weeks of gestation) infant with reactive airway disease and bronchopulmonary dysplasia, who were each intubated because of impending respiratory failure. Each patient was reintubated twice because the CECDs did not change color, there was minimal chest wall excursion, and pulse oximetry readings remained <80%, despite proper observation with direct laryngoscopy and confirmatory BUS images at the CTM in each instance. In each case, after ∼10 manual bag-valve mask-ventilated breaths with assisted manual exhalation through application of pressure to the chest wall, the CECDs finally turned yellow and the pulse oximetry readings became >90%, thus confirming proper ETT placement. Each patient seemed to have had a bronchospasm, which resulted in the difficulties with secondary confirmation of ETT placement.
In these 3 instances, the CECD had limitations, as described previously, related to poor pulmonary compliance, air trapping, and bronchospasm secondary to asthma or bronchopulmonary dysplasia or ETT obstruction secondary to gastrointestinal contents in the pharynx.1,4,5 The BUS views through the CTM may be helpful in each of these situations, to confirm proper ETT placement. In addition, BUS can be of assistance to an attending physician observing a trainee's intubation attempt in real time.
Our study suggests that BUS can be used to confirm ETT intubation in an emergency setting. This technique can serve as an adjunctive measure to confirm proper placement of the ETT in the trachea, in addition to physical examination, use of the CECD, and chest radiography. The time savings with this technique were substantial, given that it was 49-fold quicker than a chest radiograph (17.1 seconds vs 14.0 minutes). The 2 phases of our study demonstrated both advantages and limitations of this technique. We propose the use of both the CECD and BUS, along with physical examination and direct laryngoscopy, to confirm ETT placement.
Clearly, 2 views (transverse and longitudinal) are needed to observe adequately the ETT in the larynx. Raphael and Conard9 also found that imaging in the longitudinal or sagittal view was necessary when they tried to detect the cuffs of the ETTs in their study. The rate-limiting step is adequate access to the CTM, which is improved when the patient is in the sniffing position. The larger size of the Sonosite HFLT is a challenge with infants who have shorter necks and younger trauma patients who have smaller cervical collars. Although the HFLT provides better-quality images, its size makes it awkward in situations where space is limited. In these situations, the narrower LFCT is best, which is why we used this probe exclusively in phase II of the study.
This study had several limitations. First, it was a convenience study that occurred first in the PICU and then in the ED. Blinding was not attempted and the samples were not randomized, because of the nature of our emergency consent. Because successful ETT intubations were eventually performed for all patients, there might have been subtle biases that were not measured or accounted for. In addition, because only 2 investigators (Drs Galicinao and Godambe) actually performed the ultrasound studies at a single institution, the applicability of the method in general use needs to be determined. Moreover, we did not study esophageal intubations sufficiently. Our success rate for ETT intubation on the first attempt was 98% (49 of 50 cases) during phase II, with only a single esophageal intubation noted. This may also explain our high specificity and sensitivity. This bias is attributable to the fact that all of the intubations were performed in the presence of or by an experienced pediatric emergency physician. This study needs to be performed in a setting in which the success rate is not as high, such as an uncontrolled nonhospital setting.18
Finally, the depth of ETT insertion was not determined in this study. Lingle11 and Slovis and Poland10 described BUS verification of ETT position through comparison of the ETT position in reference to the aortic arch in neonates. No additional published reports regarding the use of this particular view beyond the neonatal period exist. This concurs with our experiences regarding the difficulty of obtaining these views in children beyond the neonatal period (J.G. and S.A.G., unpublished observations, 2006). Hseih et al,12 Chun et al,13 and Weaver et al14 demonstrated secondary confirmation of the depth of ETT position by examining the symmetry of diaphragmatic excursion in pediatric patients12,13 and sliding lung findings for the pleural interfaces on both sides of the chest in adult cadavers.14 Since the completion of this study, Werner et al19 demonstrated that BUS using a view just below the CTM and above the suprasternal notch could be used to differentiate esophageal and tracheal intubation in a controlled operating room setting for patients who intentionally underwent either type of intubation.
We contend that multiple views are ultimately needed to ascertain correct ETT positioning. For some patients with asthma or bronchopulmonary dysplasia (as seen in this study), who have poor air movement and diaphragmatic excursion secondary to air trapping and severe bronchospasm and therefore no color change in the CECD, the sliding lung views may not show adequate diaphragmatic motion to confirm proper ETT placement (J.G. and S.A.G., unpublished observations, 2006). In such situations, the addition of the CTM views may be useful. Similarly, in a setting in which a patient has a unilateral pneumothorax, the asymmetry of the sliding lung or diaphragmatic view may confirm the presence of a pneumothorax but cannot confirm whether the ETT is in the proper position.14 Finally, ETT obstruction secondary to gastrointestinal contents in the pharynx may compromise the CECD and also prevent adequate ventilation to permit adequate diaphragmatic excursion. In such situations, the use of the CTM view may provide additional confirmation that the ETT is in the trachea.
This study represents a first step toward the development of a protocol for the use of BUS in the determination of proper ETT placement. Unlike previous studies, phase II of this study was performed with pediatric ED patients during rapid sequence intubation. The use of BUS requires specialized training, which is accessible to most medical providers, and considerable experience. Despite its limitations, it is evident that BUS can be used to facilitate the timely confirmation of proper ETT placement. The use of the CTM view could potentially be invaluable for a supervising physician monitoring the intubation performed by a physician in training in real time. In trauma cases in which there are distorted neck anatomic features, BUS may allow for proper guidance of tube placement. BUS can also be helpful in situations involving cardiac arrest, bronchospasm, and air trapping or other cases in which a CECD may not function properly. As noted by Chun et al,13 the use of ultrasonography in the field or during transport may have tremendous potential. This 2-phase study is being followed by another study examining the need for multiple other views, in addition to the transverse and longitudinal views of the CTM. Larger multicenter studies, especially ones in which the ultrasonographers are blinded to the clinical examination and CECD results, are needed to assess the efficacy of this technique.
We thank Joseph Weinberg, Timothy O'Connor, Barry Gilmore, Donald T. Ellis, II, and Andrea Patters for critical review of this manuscript. We also thank Keven Cutler for helpful suggestions during the planning stages of this project and for assistance with the recruitment of patients. Finally, we thank the physicians and staff members of the LeBonheur Children's ED and ICU for continued support throughout this project.
- Accepted June 4, 2007.
- Address correspondence to Sandip A. Godambe, MD, PhD, Division of Pediatric Emergency Medicine, Department of Pediatrics, LeBonheur Children's Medical Center, 50 N Dunlap St, Memphis, TN 38103. E-mail:
The authors have indicated they have no financial relationships relevant to this article to disclose.
This work was presented in part at the American Academy of Pediatrics meeting; October 7, 2005; Washington, DC.
- ↵Muir JD, Randalls PB, Smith GB. End tidal carbon dioxide detector for monitoring cardiopulmonary resuscitation. BMJ.1990;301 :41– 42
- ↵Hsieh KS, Lee CL, Lin CC, Huang TC, Weng KP, Lu WH. Secondary confirmation of endotracheal tube position by ultrasound image. Crit Care Med.2004;32(suppl) :S374– S377
- ↵Murphy MF, Walls RM. The difficult and failed airway. In: Walls RM, Luten RC, Murphy MF, Schneider RE, eds. Manual of Emergency Airway Management. Philadelphia, PA: Lippincott Williams & Wilkins; 2000:31– 43
- ↵Chevallier P, Marcy P, Arens C, Raffaelli C, Padovani B, Bruneton JN. Larynx and hypopharynx. In: Bruneton JN, ed. Applications of Sonography in Head and Neck Pathology. Heidelberg, Germany: Springer-Verlag; 2002:165– 191
- Copyright © 2007 by the American Academy of Pediatrics