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Paper text:
in a previous issue of critical care , nseir and colleagues presented an article regarding continuous control of endotracheal cuff pressure and tracheal wall damage . among the pathogenic mechanisms responsible for ventilator - associated pneumonia ( vap ) , oropharyngeal colonization by potentially pathogenic microorganisms and silent aspiration of subglottic secretions around the tracheal tube cuff
several approaches have been proposed  such as placing patients in the semirecumbent position , continuous aspiration of subglottic secretions ( cass ) above the tracheal tube cuff , oropharyngeal decontamination by antiseptics , and the application of antiseptic - impregnated endotracheal tubes .
the key element of the proposed pathogenesis of vap appears to be aspiration of colonized oropharyngeal and subglottic secretions .
appropriate control of the endotracheal tube cuff pressure ( pcuff ) may therefore serve as a major prevention target .
intubated patients were recommended to be managed with pcuff values between 20 and 30 cmh2o to provide a sufficient seal without compromising mucosal perfusion . the routine management of cuff inflation consists of periodic manual checking of the pcuff , which does not ensure the appropriate maintenance of the pcuff during continuous tracheal intubation .
moreover , the manual checking of the pcuff may cause either overinflation or deflation of the cuff and may cause aspiration of contaminated secretions to the lower airway during the manoeuvre .
leaks and loss of pcuff are frequent in intubated patients , and a persistent pcuff below 20 cmh2o was an independent risk factor for vap in one study . consequently , appropriate maintenance of pressure of the tracheal tube cuff is recommended in recent guidelines . in a previous issue of the journal , nseir and
coworkers describe a pneumatic device for the continuous control of the pcuff in an animal model .
the aim of the study was to assess whether the continuous control of the pcuff results in reduced tracheal ischaemic lesions in mechanically ventilated piglets . for this purpose ,
the authors compared the pneumatic device with the manual control of pcuff in a randomized trial .
the pneumatic device provided effective continuous control of the pcuff , with longer periods of pcuff within the target values than piglets managed with manual control .
this device is therefore potentially useful for clinical practice in order to avoid both excessive inflation and deflation of the cuff .
hyperaemia and haemorrhages in the trachea were observed at the cuff contact area in all animals , however , with no differences between animals with and without the pneumatic device .
several devices that provide an automatic and continuous effective control of the pcuff have been described in the literature .
most of these devices are not automatic , some devices need frequent control by the attending staff , and other devices operating in a more automatic and continuous way are complex , requiring the use of special and expensive equipment that may not be available routinely .
it is probable that these issues concerning complexity and cost could explain the lack of continuous automatic control of cuff inflation in clinical practice .
we have described a simple and cheap device that is very effective for the routine maintenance of adequate cuff inflation during mechanical ventilation that does not require any specific equipment . a recent randomized clinical trial in mechanically ventilated patients comparing this device with the routine manual control of cuff inflation , however , showed no benefits in the prevention of vap .
these findings suggest that other factors than cuff inflation influence the microaspiration of secretions to the lower airways around the tracheal tube cuff . commercially available
high - volume low - pressure tracheal tubes such as those used in the study often form folds around the cuff , hence allowing leakage of secretions pooled above the tube cuff in studies in vitro , even at pcuff levels similar to those used by nseir and colleagues in piglets .
several devices have consequently been recently developed in order to overcome this problem . among those devices ,
the microcuff endotracheal high - volume low - pressure tube features an ultrathin ( 7 m ) poly - urethane cuff membrane around an inner conventional inflatable cuff .
this tube is effective in preventing fluid leakage around the cuff in an in vitro setup .
the combination of this device with cass is effective in preventing both early - onset and late - onset vap in a recent clinical study .
one of the potential concerns of all these devices , particularly cass , is the potential damage of the tracheal wall . in an animal sheep model , berra and
in the study by nseir and colleagues , the tracheal lesions found could be explained , at least in part , by the high inflation pressure they applied eight times daily via 50 ml during 30 min .
this is not the current clinical practice in humans , and after this study it should be completely avoided .
cass = continuous aspiration of subglottic secretions ; pcuff = endotracheal tube cuff pressure ; vap = ventilator - associated pneumonia .
the present study was supported by ciberes ( isciii - cb06/06/0028 ) , fis 02 - 0744 , separ 2001 , and 2005 sgr 00822 .
continuous control of tracheal tube cuff inflation using a pneumatic device resulted in severe tracheal wall damage in ventilated piglets . 
 this damage was similar in piglets managed with manual control of cuff inflation . 
 the periodic hyperinflation of the tube cuff used in both groups of this study may explain these results . 
 this manoeuvre should be avoided in clinical practice .