Will the Taper Shaped Cuff Replace the Conventional High Volume-Low Pressured Cuff on Endotracheal Tube?

Abstract

An effective tracheal seal plays an essential role in precluding aspiration and boosting efficiency with mechanical ventilation when endotracheal tube is inflated. High cuff pressure can cause damage to the tracheal wall and lead to serious complications such as tracheal stenosis. Endotracheal tube (ET) cuff pressures greater than 30 cmH2O may impede capillary blood flow in the tracheal wall, and ET cuff pressures greater than 50 cmH2O is considered high enough to completely block capillary blood flow.[1] Low volume high pressure cuff was used in early ETs but replaced by high volume low pressure (HVLP) cuff because the former causes mucosal injury along the lateral tracheal wall. HVLP cuffs appeared ideal because they are capable of producing a seal with low pressure. However, HVLP's large cuff diameter has emerged as a key issue as it is 1.5 to 2 times larger than the adult trachea. Longitudinal or oblique folds are developed upon inflation within the larger sized HVLP cuffs. The seal then becomes incomplete and allows secretions and air to leak as a result. Pulmonary aspiration of microorganism mass found in the oral cavity is considered one of leading causes of ventilator-associated pneumonia. In addition, over inflation of HVLP cuff can markedly increase cuff pressure, particularly around the folds and result in injury to the tracheal mucosa.[2] Low volume cuff tubes has recently drawn attention again while many researchers explored benefits of modified low volume low pressure (LVLP) cuff tubes. A taper-shaped cuff is designed to fit into the trachea at its narrow end and provides smaller cuff volume. This tapered cuff design is more effective in minimizing longitudinal folds when inflated, improving tracheal seal and preventing leakage of secretions and air even under high airway pressures, compared with conventional HVLP cuffs.[2,3] The transition from HVLP cuffs to taper-shaped cuffs is currently underway in endotracheal tubes. That is, the trend is moving back to low volume cuff tracheal tubes, which exert low pressure, in favor of better outcomes. Then we can have a question: Are tapered cuffs safe from pressure injury that is the most critical complication of low volume high pressure cuffs? While transmission of intracuff pressure to the tracheal wall depends on the cuff material, taper-shaped cuffs can transmit all the intracuff pressure to the tracheal wall.[4] In endoracheal position, the intracuff pressure of LVLP cuffs can be significantly increased by a slight change in inflating volume. In addition, the tapered cuff design provides smaller area of contact with the tracheal wall, compared to cylindrical shaped HVLP cuffs,[2] meaning that the extent of transmitted pressure is higher on the tracheal wall. It is therefore important to examine pressure changes with volume in tracheal tube cuff inflated. Special attention to pressure changes is also crucial in the tracheal tube cuff exposed to nitrous oxide for anesthesia because cuff pressure can significantly increase with increasing volume.[5] In case the taper-shaped cuff is not inflated adequately and develops an asymmetrical shape,