Article, Emergency Medicine

Tracheal ultrasonography and ultrasonographic lung sliding for confirming endotracheal tube placement: Speed and Reliability

a b s t r a c t

Background: In this study we aimed to evaluate the success of ultrasonography (USG) for confirming the tube placement and timeliness by tracheal USG and ultrasonographic Lung sliding in resuscitation and rapid sequence intubation.

Materials and methods: This study was a prospective, single-center, observational study conducted in the emergency department of a tertiary care hospital. Patients were prospectively enrolled in the study. Patients who went under emergency intubation because of respiratory failure, cardiac arrest or severe trauma included in the study. Patients with severe Neck trauma, neck tumors, history of neck operation or tracheotomy and under 18 years old were excluded from the study.

Results: A total of 115 patients included in the study. The mean age was 67.2 +- 17.1 with age 16-95 years old. Among 115 patients 30 were cardiac arrest patients other 85 patients were non-cardiac arrest patients intubated with rapid sequence intubation. The overall accuracy of the ultrasonography was 97.18% (95% CI, 90.19-99.66%), and the value of kappa was 0.869 (95% CI, 0.77-0.96), indicating a high degree of agreement between the ultrasonography and capnography. The ulrasonography took significantly less time than capnography in total. Discussion: Ultrasonography achieved high sensitivity and specificity for confirming tube placement and results faster than end-tidal carbon dioxide. Ultrasonography is a good alternative for confirming the endotracheal tube placement. Future studies should examine the use of ultrasonography as a method for real-time assessment of endotracheal tube placement by emergency physicians with only basic ultrasonographic training.

(C) 2016

Introduction

Intubation is a challenging procedure in emergency departments (EDs) because of the uncontrolled nature of the environment and a lack of team preparedness and may lead to the development of complications, such as unrecognized Esophageal intubation [1], which can cause high rates of mortality and morbidity.

Many techniques have been described for the confirmation of endo- tracheal tube placement [2], although chest radiography is considered the most reliable method. In general, chest auscultation is used for confirming tube placement, but unfortunately, 55% of one-lung intubations are misdiagnosed by auscultation [3]. The 2010 American Heart Association Cardiopulmonary Resuscitation guidelines state that quantitative waveform capnography is the gold standard method for confirming tube placement [4], but this method has some limitations,

* Corresponding author at: Bozok Universitesi Arastirma ve Uygulama Hastanesi Adnan Menderes Bulvari No:44, Yozgat, 66200.

E-mail addresses: [email protected] (S. Karacabey), [email protected] (E. Sanri), [email protected] (E.G. Gencer), [email protected] (O. Guneysel).

particularly in cardiac arrest patients, such as the need for epinephrine use, low pulmonary flow and low cardiac output [5].

Ultrasonography (USG) has a wide range of uses in EDs. It is non-

invasive, occurs in real time and thus improves the confidence of the physician in determining tube placement [6]. Tracheal ultrasonography images are not affected by very low pulmonary flow, contrary to capnography, and ultraSonographic detection of esophageal intubation can be performed prior to ventilation of the patient. Earlier detection of esophageal intubation could prevent ventilation of the stomach and its associated complications, namely emesis and aspiration.

In this study, we aimed to evaluate the success of USG for confirming tube placement and to evaluate the timeliness involved in tracheal USG and ultrasonographic lung sliding for patients undergoing resuscitation or rapid sequence intubation.

Materials and methods

This study was a prospective, single-center, observational study conducted in the ED of a tertiary care hospital. The study was conducted between September 1, 2013, and September 1st, 2014, and was approved by the hospital ethics committee.

http://dx.doi.org/10.1016/j.ajem.2016.01.027

0735-6757/(C) 2016

954 S. Karacabey et al. / American Journal of Emergency Medicine 34 (2016) 953956

Fig. 1. (A) Demonstration of transducer placement just superior to the Suprasternal notch. (B) Ultrasonographic image of esophageal intubation (C) Ultrasonographic image of tracheal intubation. (D) Longitudinal scan over an intercostal space, pleural lines, Dynamic lung sliding generated sandy pattern over M-mode, generally called a seashore sign.

Patients were prospectively enrolled in the study. In particular, patients who underwent emergency intubation due to respiratory failure, cardiac arrest or severe trauma were included in the study.

In contrast, patients with severe neck trauma, neck tumors, history of neck operation or tracheotomy, and under 18 years of age were excluded from the study.

The patients enrolled in the study were separated into 2 groups: The first group consisted of cardiac arrest patients who underwent emer- gency intubation during cardiopulmonary resuscitation (CPR), and the second group consisted of non-cardiac arrest patients who received Rapid Sequence Intubation .

Emergency intubations were performed by first-year emergency medicine residents. Tracheal and lung sliding USG were performed con- currently with intubation by 2 emergency medicine specialists who had completed a USG training course developed by the Emergency Medicine Physicians Association of Turkey.

Post-Intubation confirmation of endotracheal tube placement was performed using a capnometer (EMMA Mainstream Capnometer).

A Toshiba Aplio500 USG device and a 7.5 mHz Linear probe were used for USG. The transducer was placed transversely on the anterior neck just above the suprasternal notch. The position of the trachea was demonstrated by the appearance of a “comet-tail artifact”, specifically a hyperechoic air-mucosa (A-M) interface with a posterior reverberation artifact. To identify bilateral lung sliding over the lungs after intubation, the identified endotracheal tube position was defined as “endotracheal” if only one A-M interface with a comet-tail artifact was observed or “intraesophageal” if a second A-M interface, mimicking

a second airway (double-tract sign), appeared after the transducer was placed on both sides of the chest in the mid-axillary line near the fourth to fifth intercostal space (Fig. 1). The sonographers were not involved in the patients’ care and not aware of the waveform capnography results. One emergency medical technician measured the durations from completion of the endotracheal tube insertion to the time when sonographer had interpreted the sonographic results and to the time

at which the capnography results were obtained.

A data collection form was created to record the patients’ age, gender, capnography results, USG results and elapsed time prior to tube placement confirmation.

Statistical analysis

Various test characteristics, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and positive and negative likelihood ratios, were calculated using standard formulas for a binominal proportion, and the corresponding 95% confidence intervals (CIs) were calculated using the Wilson interval method. All statistical analyses were performed using SPSS statistical software, version 18.0 (SPSS Inc, Chicago, IL, USA) and SAS system ver. 8.2 (SAS Institute Inc, Cary, NC, USA). P b .05 was considered statistically significant.

Results

A total of 115 patients were included between September 1st, 2013 and September 1st, 2014. The patient ages ranged from 16 to 95 with a

Table 1

Ultrasonographic detection of tracheal or esophageal intubation

Total

RSI

Cardiac arrest

n = 115

Tracheal

Esophageal

n = 85

Tracheal

Esophageal

n = 30

Tracheal

Esophageal

USG tracheal

69

5

56

0

13

5

USG esophageal

2

39

0

29

2

10

USG, Ultrasonography; RSI, Rapid Sequence Intubation.

S. Karacabey et al. / American Journal of Emergency Medicine 34 (2016) 953956 955

Table 2

Test characteristics of the USG for tube placement confirmation

Total

RSI

Cardiac arrest patients

Sensitivity,% (95% CI)

97,18 (90,19-99.66)

100 (93,62-100)

86,67 (59,54-98,34)

Specificity, % (95% CI)

88,64 (75,44-96,21)

100 (88.06-100)

66,67(38,38-88,18)

PPV, % (95% CI)

93,24 (84,93-97,77)

100 (93,62-100)

72,22 (46,52-90,31)

NPV, % (95% CI)

95,12 (83,47-99,4)

100 (88,06-100)

83,33 (51,59-97,91)

PPV, positive predictive value; NPV, negative predictive value; CI, confidence interval.

mean of 67.2 +- 17.1. Among the 115 patients, 30 were cardiac arrest pa- tients, and the remaining 85 patients were non-cardiac arrest patients subjected to rapid sequence intubation.

The results of tracheal and esophageal intubation are shown in Table 1. The sensitivity, specificity, PPV and NPV of the tracheal ultra- sound and ultrasonographic lung sliding sign, which were determined using capnography as the gold standard, are shown in Table 2.

The diagnostic accuracy of ultrasound for confirming endotracheal tube placement was found to be superior for patients subjected to rapid sequence intubation compared with the cardiac arrest patients, but there was no significant difference between the two groups.

Forty-four esophageal intubations were performed, including 29 in non-cardiac arrest patients and 15 in cardiac arrest patients. The overall ultrasonography accuracy was 97.18% (95% CI, 90.19-99.66%), and the ? value was 0.869 (95% CI, 0.77-0.96), indicating a high degree of agreement between the ultrasonography and capnography results.

The positive likelihood ratio was 8.55, and the negative likelihood ratio was 0.03. No significant differences were found between the non-cardiac arrest and cardiac arrest groups.

The operating time of tracheal ultrasound is shown in Table 3, and the total duration of ultrasonography was significantly less than that of capnography.

Discussion

This study aimed to evaluate the accuracy and decision time of tra- cheal and lung sliding USG for confirming tube placement in both the RSI and CPR groups. Tracheal ultrasound achieved high sensitivity and specificity for confirming tube placement and yielded results faster than end tidal CO2. For this reason, USG may be a good choice for confirming tube placement.

Proper endotracheal intubation means that the tip of the endotra- cheal tube is located in the trachea and does not advance beyond the ca- rina and into a bronchus. Although quantitative waveform capnography is recommended by the American Heart Association in its 2010 cardiopulmonary resuscitation guidelines as the gold standard method for confirming tube placement, it has some limitations, particularly in cardiac arrest patients, such as the need for epinephrine, low pulmonary flow and low cardiac output [4,5].

Ultrasound is a common tool in EDs. In fact, ultrasound has many

uses in an ED, including the confirmation of endotracheal tube placement [7,8]. Previous studies have described the high sensitivity and specificity of the ultrasonographic lung sliding sign for confirming endotracheal tube placement. Lung sliding has been shown to be highly sensitive for differentiating esophageal versus tracheal intubation and shows one-lung intubation correctly; however, this method requires

Table 3

Time Requirement for tube place confirmation

Mean SD

Levene’s test F statistics

Levene’s test probability

t Statistics

t Probability

ETCO2 11.7565 3.0452

2.430

0.120

14.291

0.000

USG 5.8087 3.2630

ETCO2, end-tidal CO2.

ventilation to detect the results and is time-consuming [9-11]. In other studies, promising results have been obtained with tracheal ultrasound for endotracheal tube placement confirmation. Ma et al used transcricothyroid ultrasound to confirm tracheal intubation in a cadaveric model and demonstrated high sensitivity and specificity. Using tracheal ultrasonography, we can assess tracheal intubation in real time, and there is no need to ventilate the patients, but one-lung in- tubation may be misdiagnosed. As a result, in our study, we combined two techniques for confirming tube placement [12]. Two prospective studies showed that tracheal ultrasound presented up to 100% sensitiv- ity and specificity in live humans under a well-controlled operating- room setting [13,14]. In a recent study performed on 30 ED patients, high sensitivity and specificity values were obtained using combined ultraSonographic methods [15]. However, these studies have several limitations. First, these studies were performed on cadaveric models or on patients in well-monitored Operating rooms, making their results less applicable to emergency intubation. In addition, most of the studies had small sample sizes, indicating that their statistical power may be inadequate.

Our results demonstrated another potential use of ultrasound during resuscitation. The Advanced Cardiac Life Support guidelines emphasize early chest compressions and minimal interruptions. Tracheal USG can be performed in synchrony with endotracheal tube placement, even before clinical auscultation and without interruption of chest compressions [4].

Ultrasonography of the endotracheal tube placement at the trachea in already intubated patients has been described by Drescher et al [16], who reported that esophageal intubation appears as an anechoic circle close to the trachea as the tube enters the esophagus.

In our study, we had a high rate of esophageal intubation (38%) be- cause the intubations were performed by inexperienced first-year emergency medicine residents. Thus, we found that ultrasonography provides a faster diagnosis of false intubations.

Based on the results of study, we learned that the combination of tracheal USG and lung sliding is superior to capnography. In addition, in cardiac arrest patients, this combination is better than capnography because USG is not affected by low pulmonary flow. Furthermore, we demonstrated the considerable time advantage of ultrasound over capnography in confirming proper endotracheal intubation. However, USG was also affected by CPR, and the success rates in these patients were decreased compared with the success rates of those undergoing RSI.

In conclusion, ultrasonography is a good alternative for confirming endotracheal tube placement. Future studies should examine the use of ultrasonography as a method for the real-time assessment of endotracheal tube placement by emergency physicians with only basic ultrasonographic training. The impact of the use of this technique on the Laryngeal view and the feasibility of using this technique in the ED, intensive care units and out-of-hospital settings should be evaluated with a wider range of patients.

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