Article Notes
What did they do?
Chambers et al. compared ventilation parameters and respiratory complications in 104 children randomly allocated to ventilation with either a cuffed or non-cuffed ETT. They primarily investigated airway leak as measured by the difference between inspiratory and expiratory volumes.
And they found?
For both volume and pressure-controlled ventilation, leakage was lower for cuffed tubes than uncuffed. Notably leak was stable with cuffed tubes and PCV, but progressively increased over 30 minutes after intubation with an uncuffed tube.
Cuffed tubes required fewer intubations and changes, and resulted in fewer short-term complications (coughing, desaturation, hoarseness or sore throat).
Take-home message
Modern cuffed paediatric endotracheal tubes offer significant clinical advantages over uncuffed ETTs.
Daniel Jolley
Why should I read this?
The cuffed vs non-cuffed ETT debate for children and neonates is largely settled, demonstrating the superiority of modern cuffed tubes over their historical, uncuffed forbears. Nevertheless, despite reliable evidence to the contrary, many general anaesthetists still prefer uncuffed tubes for children.
Give me the quick overview
Shah & Carlisle explore the accumulated evidence supporting the shift to cuffed endotracheal tubes by paediatric anaesthetists, both in neonates and older children.
They challenge historical airway anatomy & physiology myths that once encouraged the use of uncuffed ETTs in children, and the questionable reliability of the widely-used Cole formula for tube size prediction (size = age/4 + 4; correct in only 50-75%).
The development of Weiss et al.'s Microcuff™ tube represents a watershed moment in addressing concerns of paediatric airway trauma from cuffed ETTs, resulting in improved ETT function without any increase in stridor.
More recently, Chamber's 2018 RCT compared cuffed and uncuffed ETTs in children undergoing elective general anaesthesia, and found that cuffed tubes improved ventilation and reduced short-term post-operative respiratory complications, in addition to decreasing tube changes.
Addressing concern for increased work-of-breathing and higher inspiratory pressures when using a 0.5 mm smaller ID tube, Shah & Carlisle note Thomas et al.'s 2018 laboratory study showing any such effect is easily compensated for with pressure support and automatic tube compensation.
Similarly, the authors also note that there has been no demonstrated evidence of an increased incidence of subglottic stenosis in children using cuffed ETTs.
Finally, Shah & Carlisle report on their updated meta-analysis, showing that cuffed tracheal tubes in children result in fewer tube changes and less sore throat, but no difference in risk of laryngospasm.
Finally word
Using a modern, Microcuff™ or equivalent cuffed ETT that is 0.5 mm smaller in size than an equivalent uncuffed tube, offers functional, ventilation and safety benefits.
Daniel Jolley
Toner notes the rapid adoption of high-flow nasal oxygen for apnoeic oxygenation, particularly in the context of competing alternatives that have not enjoyed the same popularity.
Specifically, it is highlighted that there is a lack of high-quality RCTs confirming the ability of Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) to acceptably clear CO2 with prolonged periods of apnoea. RCT results are awaited.
Daniel Jolley
What is automatic tube compensation? Glad you asked!
"Automatic tube compensation (ATC) is a new option to compensate for the non-linearly flow-dependent pressure drop across an endotracheal or tracheostomy tube (ETT) during inspiration and expiration. ATC is based on a closed-loop working principle. ATC is not a true ventilatory mode but rather a new option which can be combined with all conventional ventilatory modes."
Daniel Jolley
Take me back to the First Part
This study confirmed the well-known observation of the ventral ventilation shift under positive pressure ventilation, and quantified the contribution from the endotrachial tube itself, versus from muscle relaxation and IPPV.
This ventral shift under IPPV has also been shown to occur during pressure support ventilation with an LMA, when compared with spontaneous breathing under GA (Radke 2012).
Using electrical impedance tomography Lumb et al. confirmed this ventral shift in supine IPPV subjects, and demonstrated that this is primarily due to IPPV rather than the ETT itself, – although they found tube presence contributed to ~16% of the change.
"The generally accepted physiological explanation ... is that of greater cephalad movement of the diaphragm in dependent vs. non‐dependent lung regions during anaesthesia, resulting in changes in regional lung compliance."
"...regional ventilation with positive pressure ventilation during anaesthesia, even with no tracheal tube in place, is grossly different when compared with spontaneous ventilation, with greater ventilation of the left lung and ventral regions of both lungs. These effects are exacerbated by ventilation through a tracheal tube, leading to a greater degree of inhomogeneity of overall ventilation compared with when awake.
Take-home message
The authors note that while anaesthetists understand the detrimental effect of inadvertent endobronchial intubation, simply having the ETT tip close to the carina also worsens V/Q mismatch and is not as well appreciated. In these situations, tube withdrawal and/or 90o rotation may improve V/Q match.
Although this may be clinical insignificant for most patients, it should be considered when needing to improve gas exchange, particularly in critical care patients.
Daniel Jolley