guidelines have endorsed the position that a tracheostomy tube with an inner cannula and a low - pressure cuff is inherently safer than a single cannula tube with a low - volume cuff . for patients who undergo tracheostomy for failure to wean from mechanical ventilation , however , design features intended to make tracheostomy tubes safer may complicate subsequent efforts to liberate them from the ventilator . since prolonged mechanical ventilation also increases risk , it is uncertain that tubes of the first type afford these patients an overall safety advantage in an intensive care setting . a dual - cannulae tracheostomy tube , such as the shiley lpc ( covidien - nellcor , boulder , co , usa ) , occupies a relatively large amount of space within the trachea when the cuff is deflated during ventilator weaning . because of resistance to flow around this type of tube , patients so equipped often can not tolerate having the tube capped with either a speaking valve or a solid cap . early spontaneous breathing trials must then be conducted while the patient breathes through an open tube . an open tube short - circuits speech , and impairs the natural airway defenses of coughing   and swallowing . moreover , bypassing the upper airway may diminish the patient 's ability to sustain spontaneous breathing , leading caregivers to overestimate ventilator dependence . exchanging to a smaller or cuffless tube can remedy this problem , but is delayed until caregivers are confident the stomal tract is stable and the patient can either breathe spontaneously or be adequately ventilated through the new tube . with an aim to facilitate more timely rehabilitation of ventilated patients , london ontario 's university hospital has been percutaneously inserting the bivona tts tube ( smtih medical , st paul , mn , usa ) . because of this tube 's single lumen design and cuffless profile , even a size 8 tube ( outer diameter 11 mm ) can usually be capped during spontaneous breathing trials , thereby allowing caregivers to assess readiness for decannulation with the initial tube in place . when provided with a tube that has sufficient space around it , patients who had been struggling with a prolonged weaning process there are a number of reasons why restoring access to the upper airway can have such a dramatic effect . malposition of a tracheostomy tube , where the distal end is partly occluded by the tracheal wall , has been identified as an often overlooked cause of weaning failure . if , from the outset , the patient was fitted with a tube that provided an optional airway around it , as well as through it , then malposition would not be as likely to obscure the patient 's ability to resume spontaneous breathing . moreover , partial closure of the larynx   and pursed lip breathing   mitigate airway obstruction , which may help the emphysematous patient breathe more easily through the upper airway , when the tube is capped , than through an open tube . in most cases , the importance of speech is often discounted by intensive care personnel accustomed to caring for patients who have been rendered mute , but the ability to speak reduces patient stress and the need for sedation . both benefits can help avoid serious complications , and may improve the rate of recovery . studies have demonstrated a high incidence of tracheal damage from translaryngeal tubes ( endotracheal tubes ) equipped with high - pressure cuffs , so some caregivers express concern with the bivona tts 's water - filled cuff . an endotracheal tube disables glottic function , however , while a tracheostomy tube preserves it . there is thus no requirement to maintain an occlusive cuff seal with a tracheostomy tube as there is with an endotracheal tube . a slight leak around the cuff can easily be compensated for by the ventilator , and , contrary to popular belief , a fully inflated tracheostomy cuff may increase the risk of aspiration . if there is potential for a leak around the cuff , the patient can use flow from the ventilator to expel secretions from the airway . in any case , cuff inflation is under our control , and a water - filled cuff need not be inflated to the point where excessive pressure is transmitted to the tracheal wall . cuff type is not the only factor to consider if we are to minimize injury to the trachea . a polyvinyl - chloride shiley lpc tube may conform poorly to the patient 's anatomy , especially with those who have thick necks , so high cuff pressure is sometimes required to make a seal sufficient for ventilation . in those instances , the cuff on a rigid curved tube like the shiley lpc does not sit midline within the trachea , and either the arc or tip of this tube may be pressing against the tracheal wall . in contrast , flexible silicone tubes like the bivona tts accommodate to a wider range of anatomies . with careful inflation , a hard cuff on a flexible shaft may make more even and gentle contact with the trachea than a low - pressure style cuff on a rigid tube . suprastomal damage may occur during percutaneous tracheostomy and result in severe stenosis , but its incidence may be reduced if smaller tubes , and less force , are used during the procedure . it seems likely that a size 8 bivona tts tube could be inserted with less trauma than a size 8 shiley lpc , given that the shiley presents a 50% larger cross - sectional area than the bivona ( as calculated from circumferences measured around the compressed deflated cuffs ) . prolonged mechanical ventilation increases risk to the patient , and there is no evidence that the use of trachestomy tubes with inner cannulae and large - volume cuffs reduce overall mortality or morbidity . since inserting such tubes during tracheostomy has the potential to delay rehabilitation of the ventilated patient , a review of this practice is in order . researchers will hopefully be motivated to conduct clinical studies to determine how the choice of initial tracheostomy tube can affect the rehabilitation strategy and important patient outcomes .
dual - cannulae tracheostomy tubes with low - pressure cuffs , such as the shiley lpc , are widely regarded as inherently safer than single lumen tubes with low - volume cuffs . for 
 the patient who undergoes tracheostomy for failure to wean from mechanical ventilation , however , the insertion of a tube that occupies a large amount of space within the trachea can delay subsequent efforts to liberate him from the ventilator . with an aim to promote more timely rehabilitation of ventilated patients , 
 london ontario 's university hospital has been inserting the bivona tts , a single lumen tube with an elastic cuff , during tracheostomy . 
 this allows caregivers to better exploit the benefits of a functional upper airway early during the weaning process , which may reduce complications associated with prolonged mechanical ventilation . 
 we urge clinical studies to determine how the choice of initial tracheostomy tube can affect rehabilitation strategies and important patient outcomes .