In this study, we only found moderate correlations between measures of the chest wall relevant for needle decompression and body dimensions like age, weight and height. For chest wall thickness, the highest correlation was found with weight of the children (2nd ICS MCL
r = 0.57, 4th ICS AAL
r = 0.64). BMI also correlated well with CWT at 4th ICS AAL (
r = 0.60) but not at 2nd ICS MCL (
r = 0.44). Correlation for Broselow categories (2nd ICS MCL
r = 0.42, 4th ICS AAL
r = 0.38) and height (2nd ICS MCL
r = 0.42, 4th ICS AAL
r = 0.40) were lower and the lowest correlation was found for age (
r = 0.38 at both insertion sites). Hossain et al. investigated CWT in a convenience sample of children presenting to the emergency department using ultrasound. Their results for correlation of CWT with weight (2nd ICS MCL:
r = 0.55; 4th ICS AAL:
r = 0.58) are comparable to ours. Correlation of CWT with age, height, BMI and Broselow color, however, was not investigated. Mandt et al. in a CT-based evaluation, also found the highest correlation between chest wall thickness and weight (2nd ICS-MCL:
r = 0.53; 4th ICS-AAL:
r = 0.45) and reported a lower correlation with height-based Broselow categories [
2]. In most adult studies however, BMI, followed by weight, showed the strongest correlation with chest wall thickness [
10‐
12]. In multivariable regression analysis in this present pediatric study, weight had the greatest influence on the children’s CWT, with a more pronounced influence at 4th ICS AAL. However, the effect size was low with a partial
R2 ranging from 0.31 to 0.4. Both our own previous data as well as Mandt’s data showed a large variability of CWT within an age group [
2,
3]. Given the at most moderate correlation of CWT with anthropometric data, the low effect size in multivariable regression analysis and the large variability within age groups, one seems to be able to roughly guess CWT from patient characteristics, but accurate prediction of the required insertion depth does not seem possible.
One of the many possible complications of needle thoracostomy that has previously been described in adults is laceration of the intercostal vessels [
13]. The width of the intercostal space has, to the knowledge of the authors, not received any attention in adult studies and, even though injury appears much more likely in pediatric needle thoracostomy, was only investigated in one pediatric CT-based study [
3]. The results of this study match very well with the results of the ultrasound measurements presented here. Previously recommended bore sizes for decompression in infants vary from 22 to 14G. The margin of safety the provider has when using a 14G needle in an infant is extremely small. One might even encounter an infant in which the use of a 14G needle unavoidably leads to laceration of the intercostal vessels. The mean diameter of the 4th ICS at AAL was 5.3 mm in this study, the outer diameter of a common 14G needle is 2 mm. This leaves a mean safety margin of 3.2 mm. Even a slight deviation from the correct angle of insertion in direction towards the upper rib might therefore lead to vessel injury. With an 18G or 22G needle the difference between the outer diameter of the needle and the width of the ICS is still small with 4 mm and 4.4 mm but increases by 25% or 37.5% compared to the 14G needle. Width of the ICS was moderately correlated with age, weight, height and Broselow color (
r = 0.58–0.71). There was no correlation with BMI. For all variables, except BMI, correlation was higher at 2nd ICS then at 4th ICS. Multivariable regression analysis showed height being the only factor with significant influence on width of the ICS. This influence was more pronounced at 2nd ICS (
R2 = 0.47–0.50) then at 4th ICS (
R2 = 0.31–0.37). To our knowledge, there are no other studies investigating influences on width of the ICS in children or adults to which these findings could be compared.