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Background: Aspiration past the tracheal tube cuff has been recognized to be a risk factor for the development of ventilator-associated pneumonia (VAP). This study investigated the effect of closed tracheal suctioning on aspiration of fluid past the tracheal tube cuff in an in vitro benchtop model., Methods: High-volume low pressure tube cuffs of 7.5 mm internal diameter (ID) were placed in a 22 mm ID artificial trachea connected to a test lung. Positive pressure ventilation (PPV) with 15 cm H₂O peak inspiratory pressure and 5 cm H₂O positive end-expiratory pressure (PEEP) was used. A closed tracheal suction system (CTSS) catheter (size 14Fr) was attached to the tracheal tube and suction was performed for 5, 10, 15, or 20 seconds under 200 or 300 cm H₂O suction pressures. Amount of fluid (mL) aspirated along the tube cuff and the airway pressure changes were recorded for each suction procedure. Fluid aspiration during different suction conditions was compared using Kruskal-Wallis and Mann-Whitney test (Bonferroni correction [α = .01])., Results: During 10, 15, and 20 seconds suction, airway pressure consistently dropped down to -8 to -13 cm H₂O (P < .001) from the preset level. Fluid aspiration was never observed under PPV + PEEP but occurred always during suctioning. Aspiration along the tube cuff was higher with -300 cm H₂O than with -200 cm H₂O suction pressure (P < .001) and was much more during 15 and 20 seconds suction time as compared to 5 seconds (P < .001)., Conclusion: Massive aspiration of fluid occurs along the tracheal tube cuff during suction with the closed tracheal suction system., (© SAGE Publications 2011.)

Purpose: Longitudinal folds in tracheal tube (TT) cuffs cause leakage of pooled secretions past the tube cuff, and the most common in vitro method to test the efficacy of a new tube is a benchtop model using an artificial rigid trachea. This study compared the potential of a static and dynamic ventilation benchtop model and cuff lubrication in testing the tracheal sealing properties of a given TT cuff., Methods: Static trial Six brands of 7.5 mm internal diameter (ID) cuffed TT (n = 8) with high volume-low pressure cuffs were inflated in an artificial trachea (18 mm ID) without and with lubrication. Dynamic trial The same tube cuffs, without lubrication, were subjected to positive pressure ventilation (PPV) + positive end-expiratory pressure (PEEP) of 5cmH(2)O or to PPV alone (without PEEP) or to PEEP alone (without PPV). Clear water (5 ml) was placed above the tube cuff, and fluid leakage (ml) was measured up to 60 min., Results: Gel lubrication, PEEP alone and PPV + PEEP completely prevented fluid leakage across the tube cuffs in all six TT brands tested within 60 min when compared to the static unlubricated model (0% leak versus 100% leak; P < 0.01). Fluid leakage in the static unlubricated model and the PPV group was 1.38-4.76 ml and 0.23-4.47 ml, respectively., Conclusion: Gel lubrication, PEEP alone, and PPV + PEEP in the benchtop model had a much stronger protective effect than PPV alone on fluid leakage. Studies testing the fluid sealing efficiency of tube cuffs might be more conclusive in a static benchtop model without lubrication than in a dynamic model.

Background: Origin of electrocardiographic (ECG) alterations during intravascular injection of local anaesthetic solutions is controversial. The aim of this study was to elucidate whether epinephrine, bupivacaine or their combination is responsible for ECG alteration., Methods: Forty-five piglets were randomized into three groups. After induction of general anaesthesia using sevoflurane and peripheral venous cannulation, the trachea was intubated, the lungs were artificially ventilated, and anaesthesia was maintained by sevoflurane. Under steady state 0.2 ml kg(-1) and after 10 min 0.4 ml kg(-1) of one of the following three test solutions was administered i.v.: bupivacaine 0.125% (Group 1), bupivacaine 0.125%+epinephrine 1:200 000 (Group 2), and plain epinephrine 1:200,000 (Group 3). The ECG was analysed for alterations in heart rate and T-elevation., Results: After injection of 0.2 or 0.4 ml kg(-1) test solution, an increase in heart rate of at least 10% was found in none of Group 1 and in all of Groups 2 and 3. After application of 0.2 ml kg(-1) test solution, T-elevation was found in 7% of Group 1 and in 93% of Groups 2 and 3. The injection of 0.4 ml kg(-1) revealed a T-elevation in 27%, 100%, and 100%, respectively, in Groups 1, 2, and 3., Conclusions: This animal model demonstrated that increases in heart rate and T-elevation in the ECG during i.v. application of a common test dose (0.2 ml kg(-1)) of bupivacaine are caused by epinephrine addition. Whether higher doses of bupivacaine alone can cause similar ECG changes or not requires further studies.

Background: Cyclic redistribution of air within the cuff during respiratory pressure changes creates a self-sealing mechanism which allows tracheal sealing, despite tracheal airway pressure being above baseline cuff inflation pressure. The aim of the present study was to investigate the effect of continuous automated cuff pressure regulation on tracheal sealing during cyclic respiratory pressure changes., Methods: In vitro tracheal sealing was studied in four different high volume-low pressure (HVLP) tracheal tube cuffs size internal diameter 8.0 and 5.0 mm in combination with a conventional pressure manometer and two different automated pressure controllers (VBM Cuff Controller; Cuff Pressure Control Tracoe). Experiments were performed at 10, 15, 20, and 25 cm H(2)O cuff pressure during intermittent positive pressure ventilation with peak inspiratory pressures of 20 and 25 cm H(2)O. Air leakage was assessed spirometrically. Experiments were performed four times with each tube brand and size with two exemplars of each of the three cuff pressure controllers., Results: Owing to immediate cuff pressure correction, tracheal sealing at cuff pressure below inspiratory pressure was reduced in most of the tracheal tube cuffs, except in those with reduced sealing characteristics when using the Pressure Control Tracoe compared with the conventional pressure manometer and the VBM Cuff Controller. Tracheal sealing with the Pressure Control Tracoe comparable with the other two devices was only achieved at cuff pressures of 20 and 25 cm H(2)O., Conclusions: Automated cuff pressure controllers with rapid pressure correction interfere with the self-sealing mechanism of high sealing HVLP tube cuffs and reduce their improved sealing characteristics.