Laryngeal mask airway versus endotracheal tube for percutaneous dilatational tracheostomy in critically ill adults

Review question

We compared different ways of securing patients' airways so that the patients can continue to be ventilated during planned opening of the trachea. This procedure is needed for adults hospitalized for a length of time in an intensive care unit (ICU) and continuing to require artificial ventilation. The use of a laryngeal mask airway was compared with the existing endotracheal tube in terms of the safety and effectiveness of the procedure.

Background

Critically ill adults in an ICU often require mechanical ventilation to help them to breathe. Initially they are ventilated using an endotracheal tube (ETT) placed in the trachea (windpipe). Patients receiving long-term ventilation may require a tracheostomy with the breathing tube placed directly into the trachea to avoid damage to the trachea and larynx by the ETT. An opening in the neck and trachea (tracheostoma) is created and a tracheostomy tube is then inserted into this opening to ventilate the patient. This procedure is known as percutaneous dilatational tracheostomy (PDT) and is one of the most common interventional bedside procedures performed in the ICU. PDT uses a cannula to puncture through the skin to reach the trachea, followed by widening (dilatation) of this access to place a tracheostomy tube in the trachea.

PDT enters a critical stage when the tracheal cannula is inserted and the previous means of breathing, through the ETT, is loosened in the trachea and then removed. Several complications can occur at this stage.

The ETT can be damaged and the patient may not receive sufficient oxygen, the contents from the stomach may enter the lungs causing a severe lung infection, the oesophagus may be damaged, and air may get into the space between the lungs and the chest wall, or tissues in the chest may become inflamed.

A laryngeal mask airway (LMA) is often used for general anaesthesia and can also be used during PDT. It is secured in the throat and does not have to be withdrawn during the PDT, although the seal of the LMA is not as effective as that of an ETT.

Study characteristics

The evidence is current to January 2018. We included nine randomized controlled trials (517 participants). The trials included between 40 and 73 participants.

Key results

Although use of the LMA procedure may shorten the period during which the airway is insecure, the procedure is more likely to have to be changed.

Only one small study of 40 participants reported the number of people who died from any cause during their stay in hospital, without any difference between treatment groups. No deaths were caused by the procedure itself in the five studies (281 participants) that reported this outcome. Eight studies reported the number of participants with one or more serious adverse events, showing no clear evidence of a benefit for a laryngeal mask airway or endotracheal tube (467 participants). Serious adverse events that occurred were irregular rhythm of the heart beat, low blood oxygen concentrations, accidental displacement of the ETT or LMA, damage of parts of the ETT, minor bleeding and reflux of swallowed food into the airways. Neither method was superior in terms of preventing any adverse event.

The duration of the procedure was clearly shorter in the laryngeal mask group, by well over a minute (6 studies, 324 participants). This benefit was associated with a higher risk of needing to change over to a different procedure (8 studies, 434 participants). Longer-term complications were not sufficiently investigated.

Quality of the evidence

We judged the quality of evidence to be very low or low because we could not obtain important information on the methods used to conduct these studies. We had serious concerns about study limitations, the small number of participants in the studies and the variation in findings within and between studies (imprecision). Most studies were limited in reporting on patient relevant outcomes. The first study was published in 2002 and techniques have improved over time since then.

Authors' conclusions: 

Evidence on the safety of LMA for PDT is too limited to allow conclusions to be drawn on either its efficacy or safety compared with ETT. Although the LMA procedure may shorten the period during which the airway is insecure, it may also lead to higher conversion rates. Also, late complications have not been investigated sufficiently. These results are primarily based on single-centre trials with small sample sizes, and therefore the level of evidence remains low. Studies with low risk of bias focusing on late complications and relevant patient-related outcomes are necessary for definitive conclusions on safety issues related to this procedure. The dependency of the successful placement of a LMA on the type of LMA used should also be further assessed.

There are two studies awaiting classification that may alter the conclusions once assessed.

Read the full abstract...
Background: 

Percutaneous dilatational tracheostomy (PDT) is one of the most common bedside surgical procedures performed in critically ill adults, on intensive care units (ICUs), who require long-term ventilation. PDT is associated with relevant life-threatening complications: Cuff rupture or accidental extubation may lead to hypoxia, aspiration or loss of airway. Puncture of the oesophagus, or creating a false passage during dilatation or replacement of the tracheostomy tube, can lead to pneumothorax or emphysema. Wound infections may occur which can cause mediastinits, especially after creation of false passage or in early tracheotomized post-sternotomy patients after cardiac surgery. During the procedure, the patient's airway can be secured with an endotracheal tube (ETT) or a laryngeal mask airway (LMA). This is an updated version of the review first published in 2014.

Objectives: 

To assess the safety and effectiveness of LMA versus ETT in critically ill adults undergoing PDT on the ICU.

Search strategy: 

We searched the following databases to 9 January 2018: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and Embase. We searched for reports of ongoing trials in the metaRegister of Controlled Trials (mRCT). We handsearched for relevant studies in conference proceedings of five relevant annual congresses. We contacted study authors and experts concerning unpublished data and ongoing trials. We searched for further relevant studies in the reference lists of all included trials and of relevant systematic reviews.

Selection criteria: 

We included randomized controlled trials (RCTs) that compared use of laryngeal mask airways versus endotracheal tubes in critically ill adults undergoing elective PDT in the ICU, without injuries to or diseases of the face or neck. We imposed no restrictions with regard to language, timing or technique of PDT performed.

Data collection and analysis: 

Two review authors independently assessed the eligibility and methodological quality of each study and carried out data extraction. Our primary outcomes were all-cause mortality, procedure-related mortality and tally of participants with one or more serious adverse events. Where possible, we combined homogeneous studies for meta-analysis. We used Cochrane's 'Risk of bias' tool and used GRADE to assess the quality of evidence for key outcomes.

Main results: 

We included nine RCTs in this review involving 517 participants.

Studies had a high or unclear risk of bias. The main reason for this was low methodological quality or missing data, even after study authors were contacted. Study size was generally small, with a minimum of 40, and a maximum of 73 participants.

In one study (40 participants), three deaths in the LMA group and two deaths in the ETT group were reported, although none of the deaths were related to the procedure (very low-quality evidence).

Five studies (281 participants) reported on procedure-related deaths, stating that no procedure-related death occurred at all (very low-quality evidence).

It is uncertain whether there is a difference in the number of people experiencing one or more serious adverse event(s) between LMA and ETT (risk ratio (RR) 0.86, 95% confidence interval (CI) 0.41 to 1.80; 467 participants, 8 studies, very low-quality evidence).

The duration of the procedure may be shorter in the LMA group (mean difference (MD) -1.46 minutes, 95% CI -1.92 to -1.01 minutes; 6 studies, 324 participants, low-quality evidence).

However failure of procedure, as allocated by randomization, requiring conversion to any other procedure, may be higher in the LMA group (RR 2.82, 95% CI 1.22 to 6.52; 8 studies, 439 participants, low-quality evidence).

We did not find any clear evidence of a difference between ETT and LMA groups for all other outcomes. Only one study provided follow-up data for late complications related to the intervention, showing no clear evidence of benefit for any treatment group.

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