Discussion
This study found that simulator-based training for identification of endotracheal tube placement was efficacious in training novice users with high sensitivity and specificity. Our study showed POCUS to be an accurate and rapid method to detect correct position of the endotracheal tube (3.0 (IQR 3.0-4.0) seconds).
The majority of intubations were for emergent causes including respiratory failure, surfactant administration, and hemodynamic compromise; similar to those reported by Foglia et al. in 2019.26 Another study also listed reasons for ETT intubations such as prematurity (57.8%), respiratory failure (24.3%), life-threatening apneas (13.4%), and re-intubation after accidental displacement of ETT (4.5%).27
Several methods are considered as standard-of-care methods for ETT position confirmation including bilateral chest auscultation, capnography, and chest radiography. Studies in adults have demonstrated disposable CO2 detectors to be highly sensitive and specific for confirmation of ETT placement and reported a sensitivity and specificity of 91% and 100% when compared to clinical examination.27 Likewise, POCUS sensitivity and specificity for identification of an ETT was reported to be 0.98 (95% CI 0.97 to 0.99) and 0.98 (95% CI 0.95 to 0.99), respectively in a meta-analysis of f 323 adult intubations . They recorded a sensitivity of 91% and specificity of 97% of POCUS compared to standard methods.28 Similarly another meta-analysis reported sensitivities of 93-98% and specificities of 97-98% for POCUS.29
In contrast to adult POCUS, the use of this modality for ETT placement is somewhat scarce in pediatrics. Chou et al. in 2013 reported a sensitivity and specificity of 100% in children that underwent resuscitation and intubation.30 In our study, the sensitivity and specificity compared to standard care was 99.7% and 91.7%, respectively.
The time it takes to confirm ETT placement is critical regardless of the method chosen. Chest auscultation can be unreliable in a noisy environment during resuscitation and takes approximately 77 seconds to appreciate audible breath sounds.31 However, in our study, we recorded a short time of only 6.0 seconds with the auscultation method. The possible reasons could be the rigorous mandatory NRP training and certification that the health care providers in NICU undergo with repeated refresher trainings, leading to excellence in competency.
Capnography, although a reliable method with high sensitivity10 can depict false negative results in conditions with low cardiac output, inadequate pressure to inflate the lungs,10,32 and presence of secretions in ETT.33 However, it is a rapid method and studies have reported the time for capnography confirmation as 1.6 seconds (SD +/- 2.4).31 In a study by Aziz et al., the time required to confirm ETT position via capnography was 6 to 12 seconds.27 We reported a similar time of 3 seconds (IQR 3.0-4.0).
Use of POCUS is gradually gaining popularity with its rapid assessment and ease of interpretation in infants and newborns. It does not interfere during chest compression and is not affected by environmental noise and cardiac output.30 The average time required for POCUS used in emergency situations by physicians and anesthesiologists reported in literature is 9 seconds.29 Several studies have also measured the time to perform transtracheal ultrasound in emergent situations with a wide range from 5-45 seconds,15,28,34,35 while few studies have shown time to ultrasound to be shorter than capnography.28,36,37 However, our study showed no difference in interpretation time with both modalities.
This is the first study of its kind to assess diagnostic accuracy of POCUS for endotracheal tube placement in a neonatal population in the country. It was a prospective design with the largest sample size of newborns to date. We did not only measure the accuracy of POCUS with standard-of-care methods, but also measured the time to interpretation for each method in a real-time scenario. Moreover, POCUS and standard-of-care methods were interpreted independent of each other, thus minimizing the risk of bias.
The study has some potential limitations. In our setting we did not have each of the three standard-of-care methods for all intubations and hence the analysis was done by composite of at least two current methods. In addition, this was a single-centre study and hence the results may not be generalized.
Point of care ultrasound has various advantages and its clinical prevalence is increasing in adults and older children. Many of these applications and benefits can be translated to a neonatal population. This may improve resuscitation by timely recognition of ETT placement and minimize traditional unmeasured radiation exposure.