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Paper text:
the study by rajajee and colleagues   published in the previous issue of critical care , ' real - time ultrasound - guided percutaneous dilatational tracheostomy ' , is certainly thought provoking .
although both percutaneous tracheostomy and ultrasound for critically ill patients have been studied for decades , rajajee and colleagues have added a new twist : they incorporate ' real - time ' ultrasound in an effort to improve the safety of percutaneous tracheostomy in a heterogeneous case series of 13 patients , some of whom have problems known to make inserting a tracheostomy more challenging ( for example , two patients under cervical spine precautions , and six obese patients , of whom four had unclear anatomy by palpation ) . of importance , in this case series palpation and bronchoscopy were also used to determine anatomy ( that is , ultrasound alone was not tested ) and bronchoscopy was used to rule out injury to the posterior tracheal wall prior to passing the dilators . this small feasibility study does not allow us to draw any conclusions about the incremental benefits or harms of using ' real - time ' ultrasound over standard approaches in higher - risk tracheostomy patients , as few patients were included and there was no comparison group .
furthermore , this pilot series does not prove that we should all fire up the ultrasound before performing our next tracheostomy , but it does reinforce several important messages .
the first message is that neck ultrasound can provide useful additional information about variations in neck anatomy , which might lead to modifications of the planned surgical approach .
as figure 3 in the study nicely illustrates , ultrasound can be used to measure the distance from skin to trachea , allowing the choice of an appropriately sized tracheostomy tube ( that is , regular or extended length ) , which certainly might be beneficial for patients with larger necks .
however , it can be difficult to visualize the actual needle and its tract during an ultrasound - guided tracheostomy ( figure 4 in ) since the needle must enter the trachea almost directly below the skin puncture site , rather than being passed beneath the probe at an angle as is typically the case when using ultrasound to guide a biopsy or a central venous catheter insertion .
indeed , rajajee and colleagues   only saw the needle indentation of the tracheal wall in 4 of 13 patients .
another important limitation of ultrasound is that it does not image across air interfaces , and thus can not be used to rule out injury to the posterior wall of the trachea .
second , this study reminds us that multiple bleeding structures , such as the thyroid isthmus and anterior jugular and inferior thyroid vessels , may lie between the skin and the trachea .
unfortunately , the case series from rajajee and colleagues is unable to conclude whether or not knowing about the location of these structures as a result of ' real - time ' ultrasound , versus either pre - procedure ultrasound or no ultrasound at all , will actually reduce risks such as bleeding or , paradoxically , increase complications .
most of the randomized trials and cohort studies conducted to date on percutaneous tracheostomy ( of which few used ultrasound ) have shown that the incidence of bleeding with percutaneous tracheostomy is quite low and rarely requires surgical intervention . the infrequent bleeding observed in these studies
likely stems from a combination of factors , including careful selection of patients , few patients having midline neck vessels , the tamponade effect of the tracheostomy tube and dressings , and the surgical technique , including minimal or more extensive clearing of the midline prior to tracheostomy insertion . in rajajee and
colleagues ' case series some of the tracheostomy tubes were placed through more caudal tracheal rings in order to avoid ' pretracheal ' vessels visualized by ultrasound .
readers should be cautioned that routinely inserting tracheostomy tubes between tracheal rings lying low in the neck has been associated with an increased risk of tracheoinnominate fistula ( which has a mortality of up to 80% ) .
indeed , this is the reason most surgeons performing open or surgical tracheostomies will either displace overlying vessels laterally or ligate them rather than using a lower insertion .
the case series from rajajee and colleagues is thought provoking , but further study is required to determine whether routine use of ' real - time ' ultrasound will confer any significant benefit ( or harm ) over current percutaneous tracheostomy approaches .
considering the low rate of complications reported in most previous studies of percutaneous tracheostomy , we think a future study will be unlikely to detect a clinically important benefit from routine use of ' real - time ' ultrasound for all patients undergoing the procedure .
however , perhaps there exist subsets of patients having more challenging neck anatomy for whom ultrasound - guided needle passage might be safer than passing the needle blindly .
we encourage readers to become more familiar with neck ultrasound as an additional strategy to help plan a safe tracheostomy approach , and continue to use good clinical judgment when placing percutaneous tracheostomy tubes .
percutaneous tracheostomy has become a routine procedure in most intensive care units , and point of care ultrasound is becoming used with greater frequency to augment diagnosis and therapy for critically ill patients . 
 the case series from rajajee and colleagues incorporates ' real - time ' ultrasound in an effort to improve the safety of percutaneous tracheostomy . 
 while their report does not prove that ultrasound should be used prior to or during all percutaneous tracheostomies , it does reinforce several important safety considerations concerning the anatomy of the neck , and in particular the potential to encounter bleeding complications during these procedures .