Saudi Journal of Otorhinolaryngology Head and Neck Surgery

ORIGINAL ARTICLE
Year
: 2022  |  Volume : 24  |  Issue : 3  |  Page : 114--117

Height measurement and ultrasound assessment of subglottic region for the estimation of appropriate endotracheal tube size in pediatric population


Salwa AlRashed AlHumaid1, Fahad AlSaab1, Abdullah Arafat1, Abdullah ALMajed1, Nezar AlZughaibi2, Adnan Koumi2, Marwan Hdaki2, Mohammed ALMutairi3, Homod ALHoraim3,  
1 Department of Surgery, Division of Otolaryngology–Head and Neck Surgery, King Abdulaziz Medical City and King Abdullah Specialist Children's Hospital, National Guard Health Affairs, Riyadh, Saudi Arabia
2 Department of Pediatric Anesthesia, King Abdullah Specialist Children's Hospital, National Guard Health Affairs, Riyadh, Saudi Arabia
3 Departement of Surgery, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia

Correspondence Address:
Dr. Salwa AlRashed AlHumaid
Department of Surgery, Division of Otolaryngology and Head and Neck Surgery, King Abdulaziz Medical City and King Abdullah Specialist Children's Hospital, National Guard Health Affairs, Riyadh
Saudi Arabia

Abstract

Background: Choosing the appropriate endotracheal tube (ETT) size in pediatric patients is crucial to guarantee well ventilation and reliable end-tidal gas monitoring. Different methods have been established for choosing appropriate ETT size with varied validities depending on the demographics of the patients. Objectives: The primary objective is to investigate a relationship between the height of the patient and the appropriate ETT size and form a predictive formula. Design: A prospective, observational study was conducted between November 2019 and March 2020 in a pediatric hospital, Riyadh, Saudi Arabia. Setting: Patients below 14 years of age admitted for elective day surgery with American Society of Anesthesiologist Class 1 or 2 were invited to participate. Patients with anticipated difficult airway or neck mass or those refused to enroll were excluded. Methods: After obtaining institutional review board approval, informed consents were taken from all patients' guardians. Collected data were gathered in excel sheet. Main Outcome Measures: Demographic and clinical data were collected. The subglottic area was measured before induction of anesthesia by bedside ultrasound machine. No formulas were used for ETT size used. Sample Size: 71 children were included in the study. Results: The ETT based on the height of the patient was estimated using the formula below as “estimated ETT size if other formula used:” {INSIDE:1] estimated based on height. Pearson's correlation results revealed a positive association between the ETT used and ETT estimated. The relationship between variables is insignificant, with a P > 0.05. There was an overestimation in both the ETT used and ETT estimated in the stepwise regression analysis. About 88.5% overestimate the ETT used based on age, and about 89.7% overestimate the ETT based on patient height. The F-value change statistics indicates a statistical significance of ETT used and ETT estimated. Conclusion: It is crucial to have an accurate ETT tube size used in children. The height of the child was found to have good correlation with ETT size in our Saudi population. Limitation: Part of the limitations faced was the fact that it was a single-center study which may not represent the population from other areas.



How to cite this article:
AlHumaid SA, AlSaab F, Arafat A, ALMajed A, AlZughaibi N, Koumi A, Hdaki M, ALMutairi M, ALHoraim H. Height measurement and ultrasound assessment of subglottic region for the estimation of appropriate endotracheal tube size in pediatric population.Saudi J Otorhinolaryngol Head Neck Surg 2022;24:114-117


How to cite this URL:
AlHumaid SA, AlSaab F, Arafat A, ALMajed A, AlZughaibi N, Koumi A, Hdaki M, ALMutairi M, ALHoraim H. Height measurement and ultrasound assessment of subglottic region for the estimation of appropriate endotracheal tube size in pediatric population. Saudi J Otorhinolaryngol Head Neck Surg [serial online] 2022 [cited 2022 Nov 29 ];24:114-117
Available from: https://www.sjohns.org/text.asp?2022/24/3/114/357634


Full Text



 Introduction



Endotracheal intubation is an invasive medical technique that is often done by an anesthesiologist by inserting a flexible tube in the trachea via mouth or nose. Choosing the appropriate endotracheal tube (ETT) size in pediatric patients is a critical element to make sure that the patients are well ventilated and end-tidal gas monitoring is reliable. A large ETT size might result in an insult to the upper airway (e.g., local ischemia, ulceration, and scar formation) and the susceptibility for subsequent subglottic stenosis,[1],[2] while choosing a small-sized ETT might cause inadequate ventilation, unreliable end-tidal gas monitoring, and an increase in the risk of aspiration.[3],[4],[5]

Formulas based on age such as modified Cole formula (size [mm, internal diameter (ID)] = age/4 + 4) for uncuffed ETT, Motoyama's formula (ID = age/4 + 3.5) for cuffed ETT, and other weight–height formulas are commonly used methods to determine the appropriate ETT size. However, most of them do not work very well considering growth and racial variations among patients. Consequently, this may result in multiple attempts of reintubation which further exposes the patient's airway.

Recent studies suggested that ultrasound (US) can be a good predictor for the appropriate ETT size.[6],[7],[8],[9],[10] US is also a reliable method for determining the subglottic diameter. However, it might be impractical in an emergency situation that needs fast, easy to remember, and accurate method to predict the appropriate ETT size. Therefore, an accurate and easy formula is needed to predict the suitable ETT size. The primary objective of this study is to investigate a relationship between the height of the patient and the appropriate ETT size and form a predictive formula. The secondary objective is to find any correlation between patients of obstructive sleep apnea (OSA) and changes in the diameter of the airway.

 Methods



After obtaining the approval of the hospital's institutional review board, a prospective, observational study was conducted from November 2019 to March 2020 in the institution's pediatric hospital, Riyadh, Saudi Arabia. Pediatric patients below 14 years of age admitted for elective day surgery (adeno/tonsillectomy, myringotomy) with American Society of Anesthesiologist (ASA) Class 1 or 2 were invited to participate in the study. Patients with anticipated difficult airway or neck mass or those refused to enroll were excluded. Informed consents were taken from all patients' guardians in the preoperative preparations. Collected data were divided into two domains. Demographic data such as age, gender, weight, height, ASA Class, and past medical history were recorded. As for clinical data, parameters collected were subglottic US measurement, ETT size used, airway finding during intubation, and presence of postoperative stridor. The subglottic area was measured before induction of anesthesia by bedside US machine. No formulas were used for ETT size used.

Descriptive data were presented as mean (standard deviation [SD]) for the continuous variables. Categorical variables were presented as frequencies and percentages. Chi-square test was utilized to identify correlations and associations between the variables. Differences exhibiting P < 0.05 were considered statistically significant. Pearson's correlation was used to measure the strength and the relationship between variables. Regression analysis was employed to determine the relationship between the ETT used and the ETT estimated. P < 0.05 was considered statistically significant.

 Results



A total of 71 children were included in the study. 47 (66.2%) were male with a mean (SD) age of 6 (3.12) years. The mean (SD) height was 114.3 (20.9) cm, while the mean weight was 25.3 (20.6) kg. Majority of patients had unremarkable past medical history. Five patients had bronchial asthma, one had G6PD, and another was diagnosed with Stickler. Of the 71 included patients, 90% had ASA Class 1 with only 7% having OSA symptoms. 76% of the patients underwent adenotonsillectomy, 12% adenoidectomy only, and 8.5% myringotomy. A summary of the participant characteristics is illustrated in [Table 1].{Table 1}

The ETT based on the height of the patient was estimated using the formula below and fed into the SPSS SPSS, JMP, United Kingdom. as “estimated ETT size if other formula used:”

[INLINE:1]

[Table 2] and [Table 3] show the ETT descriptive statistics and Pearson's correlation results, respectively.{Table 2}{Table 3}

It is clear from the descriptive statistics that ETT based on age has a mean (SD) of 1.59 (0.496). ETT estimated based on height has a mean (SD) of 1.94 (1.275). From the Pearson's correlation results, it is clear that there is a positive correlation between the ETT used and ETT estimated (r = 0.101, P = 0.431, and N = 71). The relationship between variables is insignificant with a P > 0.05.

As shown in [Table 4], the step-wise regression analysis was used. From the result, there was an overestimation in both the ETT used and ETT estimated. About 88.5% overestimate the ETT used based on age and about 89.7% overestimate the ETT based on patient height. The F-value change statistics is 0.000 and 0.009, which indicates a statistical significance of ETT used and ETT estimated.{Table 4}

From our collected data, there were no changes in diameter of airway in patients with OSA compared to non-OSA.

 Discussion



Choosing the appropriate ETT size in pediatric patients is crucial to guarantee well ventilation and reliable end-tidal gas monitoring. A small-sized ETT might cause inadequate ventilation, unreliable end-tidal gas monitoring, and an increase in the risk of aspiration, whereas a large ETT size might cause an injury to the upper airway such as local ischemia, ulceration, scar formation, and the susceptibility of having subsequent subglottic stenosis. Therefore, different methods have been established for choosing the appropriate ETT size. Their validities varied in the literature depending on the demographics of the patients and the status of surgery. Thus, easy to remember ETT size formula is crucial for accurate size choice.

Von Rettberg et al. compared published formulas of proper ETT size estimation in pediatric population. Up to 2009, 22 formulas were identified and validated for patients above 1 year of age.[11]

In 2009, Turkistani et al. concluded that the age-based and fifth fingernail width predicted the best fit of ETT more accurately than length and multivariate formula in their Saudi pediatric sample size.[12]

The pediatric Broselow emergency tape is a length-based tool to predict body weight during emergency. Subramanian et al. recently published their findings in predicting and evaluating the ETT size used in 199 recruited pediatric patients. Their results showed that age-based formula had a correct predictability rate of 59.8%, the Broselow formula had a correct rate of 50.3%, whereas the length-based formula had 48.7% accuracy.[13]

Shih et al., in their 336 Chinese pediatric population, found to have 82.4% accuracy in length-based formula to predict a suitable ETT.[14]

Our findings were similar to what was described by the Chinese. The height of the child was found to have good correlation with ETT size in our Saudi population using the following formula:

[INLINE:2]

From our collected data of subglottic US measurement, there were no changes in the diameter of airway in patients with OSA compared to non-OSA.

Part of the limitations faced in this study was the fact that it was a single-center study which may not represent the population from other areas. The other was the relatively small sample size enrolled.

 Conclusion



It is crucial to have an accurate ETT size used in children. The height of the child was found to have good correlation with ETT size in our Saudi population. The above-described height formula is also easy to remember in case of emergency cases to predict the accurate ETT which may decrease the need for multiple trials of intubations.

Acknowledgments

The authors would like to thank all the medical interns, residents and nurses who participated in the study. Special thanks to the Otorhinolaryngology Department and Anesthesia Department at the institution for their technical support.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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