The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

Accuracy of the 7-8-9 Rules for Endotracheal Tube Placement in the Neonate

Nancy Johnson RRT-NPS, Jennifer Peterson MD, Kathleen Deakins RRT- NPS, Deanne Wilson-Costello MD, Robert Chatburn RRT-NPS FAARC
Departments of Pediatrics and Respiratory Care, Rainbow Babies and Children's Hospital, Case Western Reserve University, Cleveland, OH

Background: The 7-8-9 Rule in neonatal resuscitation adds 6 cm to an infant's weight to estimate the depth of endotracheal tube (ETT) insertion. Accuracy of this commonly used method has not been reported. The purpose of this evaluation was to determine the accuracy of the 7-8-9 Rule in predicting endotracheal tube placement in neonates.

Methods: Seventy-five consecutive neonates admitted to a neonatal intensive care unit who required oral intubation were identified. ETT was initially inserted to the depth predicted by the 7-8-9 Rule. ETT was secured after auscultation, ETT depth at the lip was documented, and a chest radiograph with digitalized measurements was obtained. Ideal mid-tracheal placement of ETT was defined a priori as the tip of ETT lying mid-trachea, halfway between the inferior portion of the clavicle and carina. Using the clavicle as a radiographic landmark, the difference between distances to mid-trachea and ETT tip was determined. This difference was added to the documented ETT depth at the lip to calculate the mid-tracheal ETT depth. Accuracy was determined using mean paired differences of the predicted and mid-tracheal ETT depths with 95% confidence intervals (CI). The range of error expected in 95% of the intubations at a 99% confidence level was calculated using the individual error interval. Statistics were performed using JMP 5.1 (SAS Corp., Cary, NC).

Results: Mean gestational age was 32 weeks (range 23 to 44) and mean weight was 2001 grams (range 490 to 4400). The mean paired differences between predicted and mid-tracheal ETT depths were -0.12 cm (95% CI -0.30 to 0.06). The error interval was -2.05 to 1.81 cm justifying ETT adjustment in 24% (18/75) of the neonates. Predicted and mid-tracheal ETT depths were significantly different for 2.5 ETT (mean difference of 0.30 cm, 95% CI 0.01 to 0.58, p=0.04) and 3.0 ETT (mean difference of -0.35 cm, 95% CI -0.65 to -0.05, p=0.03).

Conclusion: The 7-8-9 Rule appears to be a reasonably accurate method for endotracheal tube placement in neonates. However, individual error as large as 2 cm above or below mid-trachea may occur necessitating auscultation and radiographic confirmation. When comparing endotracheal tube sizes, significant error exists between mid-tracheal and predicted endotracheal tube depth.

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