Predictors of difficulty in bedside percutaneous dilatational tracheostomy: pilot study

Introduction: percutaneous dilatational tracheostomy is currently one of the main procedures performed in an intensive care unit (ICU). However, there are no well-defined indicators of technical difficulty in performing the procedure. Objectives: to define predictors of difficulty in performing bedside percutaneous dilatational tracheostomy. Methodology: prospective cohort study encompassing 21 patients who underwent bedside percutaneous dilatational tracheostomy in the ICU at a single center. Results: Sternohyoid (SH) distance shorter than 7 cm is associated with a 50% increase in the risk of technical difficulty (OR 0.44 and p <0.03). Conclusion: the reduction in (SH) distance is related to an increased risk of difficulty in performing percutaneous dilatational tracheostomy in the ICU bed.

Although the occurrence of complications related to PDT is uncommon 4 , significant adverse events are described, mainly related to injuries in structures adjacent to the trachea, such as the vascular network, with consequent hemorrhage or failure to insert the tracheal cannula 5 , with impaired patient ventilation.
It is also worth remembering that, despite being a controlled environment, the intensive care unit is not routinely prepared for critical complications that may occur during surgical procedures 5

GOALS
To define predictors of difficulty in performing percutaneous dilatational tracheostomy.

METHODS
This is an observational prospective cohort study, in which we included 21 patients who underwent bedside percutaneous dilatational tracheostomy in the ICU at a single center.
A trained head and neck surgeon, with experience in PDT, performed the procedure. In all cases, the tracheostomy was guided by bronchoscopy (performed by a bronchoscopist or another head and neck surgeon trained in bronchoscopy). All procedures were performed in the ICU bed.
We collected data on age, sex, obesity, time of orotracheal intubation, size of the orotracheal cannula, sternohyoid (SH) distance, sterno-cricoid (SC) distance, presence of calcified trachea, tracheomalacia, thyroid goiter, and palpable trachea ( Table 1) We considered a difficult procedure the one displaying at least one of the following items: prolonged time; more than one tracheal puncture; dilation difficulty; and difficulty of the procedure referred by the surgeon.
We collected data on complications related to the procedure until the seventh postoperative day.
We used the REDCap software for the collection and management of clinical data.

Statistical analysis
We entered the data into the Stata IC v16 for Mac software.
We performed univariate analysis by logistic regression of all variables collected, to verify association with the outcome. The variables with p<0.20 were selected for multivariate analysis 9 .
We then performed a multivariate analysis by logistic regression, and chose the best model using the technique described by Hosmer and Lemeshow -Purposeful selection of covariates 10 .
We considered associations with p<0.05 as statistically significant 9 .

RESULTS
We included 21 patients, with a mean age of 60 years, 16 (76%) of whom were male, and 5 (24%), female. The mean time of orotracheal intubation was 14 Age, sex, time of orotracheal intubation, obesity, thyroid goiter, tracheomalacia and calcified trachea did not present a statistically significant association with the difficulty of the procedure, either by univariate or by multivariate analysis.
The SH distance had no statistically significant association by univariate analysis. However, in the multivariate analysis it was a predictor of reduction in difficulty, and SH distance shorter than 7 cm increased the probability of difficulty by 50% (OR 0.44, p<0.03) (Graphic 1).
with a 50% increase in the chance of technical difficulty (OR 0.44, p<0.03).
The other variables displayed no significant association. However, due to the reduced sample size, it is not possible to exclude them as predictors. We believe that SC distance is also an important predictor and we are expanding the study to include more patients and

CONCLUSION
Short SH distance is related to an increased risk of difficulty in performing bedside percutaneous dilatational tracheostomy at the ICU.

Graph 1.
Probability of having difficulty to carry out the procedure regarding the sternohyod distance (OR=0.44 p=0.03). *The graphic was created by the Stata IC v16 software for Mac, after a multivariate logistic re-gression analysis showing the respective confidence intervals (CI-95%) ** Outcome (y axis) -probability of difficulty to carry out the procedure/predictor (x axis) -sternohyod distance (cm) measured as straight line, having the patient in cervical extension ***The difficulty was defined as the presence of at least one of the following items: long time to carry it out; more than one tracheal puncture; difficult dilation; and surgeons' report of having had difficulty ot carry out the procedure.

DISCUSSION
In our study, SH distance was a predictor of difficulty in performing percutaneous dilatational tracheostomy. SH Distance less than 7 cm was associated