Systematic Review

Percutaneous dilatational tracheostomy (PDT) has become widely adopted in critical care units following Ciaglia’s first description of the dilatational technique40. Since then multiple percutaneous techniques have been described, introduced and widely evaluated in comparison to both each other and surgical tracheostomy (ST). Whilst the short-term complications of these techniques are well described, the prevalence and impact of longer-term outcomes, particularly TS, is unclear. Previous meta- analyses have attempted to address this problem but have been confounded by the low incidence of TS and, in particular, the limited number of studies reporting long-term outcomes 51-55.

On examination of current evidence, the meta-analysis published by Delaney et al, found a significantly decreased rate of wound infection after all commonly performed percutaneous techniques compared to surgical tracheostomy51. Additionally, there were reductions in mortality and bleeding in patients undergoing percutaneous tracheostomy in the critical care unit as opposed to ST in the operating theatre. Higgins et al, also reported a tendency towards a reduction in overall complications for percutaneous procedures53. In contrast, Oliver et al, found an increased incidence of minor early complications associated with percutaneous techniques but insufficient evidence to suggest a difference in late complications of poor cosmetic results and tracheo-cutaneous fistulae52. Cabrini et al, found that the six percutaneous techniques analysed (Ciaglia multiple dilator method (CPDT), guide wire dilating forceps (GWDF), single tapered dilator (STD), trans-laryngeal tracheostomy (TLT), balloon dilator (BD), single step rotational dilator (SSRD)) were largely comparable with the exception of the TLT, which was associated with an increased conversion rate to ST or other percutaneous technique and more severe early complications54. They also

found the STD was associated with fewer complications and failures. In a later analysis the same authors reported less operative bleeding and fewer technical difficulties associated with the STD technique compared to the GWDF technique using a composite endpoint55_.

The meta-analyses described above have included only randomised controlled trials (RCTs). The only exception to this was the analysis by Oliver which also included non-randomised prospective studies52. The largest single study incorporated into the previous analyses comprised 346 patients56. It is perhaps unsurprising, therefore, that none of the previous meta-analyses have reported differences in late complication rates. The exact incidence of long term complications following tracheostomy

procedures in the critically ill is difficult to quantify due to the associated mortality of critical illness, the sub-clinical nature of many tracheal stenoses and the difficulty maintaining follow up of these cohorts. From a number of prospective cohort series it would appear that sub-clinical TS is found in around 10% of survivors79 with

clinically evident lesions presenting in 0 - 0.35%57-59.

Despite its low incidence, TS causes significant ongoing morbidity and healthcare costs associated with its management. The management of choice for TS has been segmental tracheal resection since Grillo183 and Pearson112 demonstrated good outcomes. However, in some patients stenoses may not be amenable to surgery. Management of such patients presents a challenge; alternative treatments include endoscopic dilatation, laser ablation, tracheal stenting and cryosurgery107_{. These}

interventions may temporarily alleviate the symptoms of TS but as re-stenosis is a frequent occurrence repeated procedures are often necessary. Given this associated morbidity and the cost associated with the management of TS a clearer picture of the risk associated with each tracheostomy technique performed within the critical care

setting is required.

There is little direct evidence for the association of any peri-operative complications with the aetiology of TS. In a study, pre-dating the widespread introduction of PDT, assessing the impact of prolonged tracheal intubation and tracheostomy Stauffer identified a high incidence of complications associated with ST (36% for stomal bleeding, 36% for stomal infection) and a 65 % tracheal stenosis incidence74. Despite a number of moderate sized case series from tertiary centres reporting of the

management of tracheal stenosis none have specifically looked at the role of peri- operative events in the initiation of TS71,75,88,184. The only peri-operative event that has been postulated to have a role in the genesis of TS is tracheal ring fracture. Whilst a number of authors184-186 have suggested that tracheal ring fracture may be of

significance this is not necessarily borne out within large cohort studies59. Further studies have considered a role for infection in the initiation of TS. In an animal model of tracheal stenosis Squire inoculated the tracheas of rabbits with Staphylococcus aureus66. When compared to those without bacterial inoculation the incidence of

tracheal stenosis was higher and the resultant lesions narrower. Additionally, Welkoborsky examined operative specimens removed from 18 patients undergoing surgical resection for TS and felt infection at the stenotic segment played a part in its initiation in 4 patients69. Despite this work and evidence to suggest a greater incidence of stomal infections for ST compared to PDT51 there is no evidence to that the

incidence of TS differs between the two techniques or that antimicrobial treatment reduces the incidence of TS.

Despite this lack of direct evidence for the association of peri-operative events with the development of TS we postulated that some complications maybe surrogate markers for a more severe tracheal injury at the time of tracheostomy and thus affect

the healing process. When considering such problems it is possible that many of the events listed in Appendix 1 may lead the operator to settle for sub-optimal

tracheostomy tube positioning which may have an impact on later healing or

predispose to infection. We, therefore, felt that the role such factors may play in the initiation of tracheal stenosis was worthy of further study.

Therefore, we performed a systematic review of all prospective studies that reported long-term outcomes and assessed potential predisposing factors. Our aim was to determine if longer-term complication rates, with particular reference to TS, differed between percutaneous and surgical tracheostomy techniques in the critical care setting.

3.2 Single tapered dilator percutaneous tracheostomy: An 11-year review