Comparison of air-sealing characteristics of tapered- vs. cylindrical-shaped high-volume, low-pressure tube cuffs.

BACKGROUND: This study aimed at comparing air-sealing characteristics of the new tapered-shaped tracheal tube cuffs with cylindrical tube cuffs. METHODS: Tracheal tubes with tapered-shaped polyurethane (PU) and polyvinyl chloride (PVC) cuffs as well as standard cylindrical-shaped cuffs made of PU and PVC (Covidien, Athlone, Ireland) were investigated. A tracheal model attached to a test lung was intubated, and cuffs were inflated to 10, 15, 20, 25 and 30 cm H(2)O. The test lung was ventilated with intermittent positive pressure ventilation at peak inspiratory pressures (PIPs) of 20 and 25 cm H(2)O. Air leakage was assessed by spirometry and measurement of sevoflurane concentration passing the cuff at the upper cuff border using an anaesthetic gas analyser. Experiments were repeated four times with new tracheal tubes for each run. Statistical comparisons were done using Mann-Whitney U-test with level of significance at P < 0.05. RESULTS: The tapered-shaped PVC tube cuff demonstrated a significantly lower air leakage determined by spirometry than the cylindrical-shaped cuff at both PIPs (20 and 25 cm H(2)O). Similarly, sevoflurane leakage was less with the tapered PVC cuff particularly at higher cuff pressures. With the PU cuff, reduction in air leakage by a tapered-shaped compared with a cylindrical-shaped tube cuff was not significant. CONCLUSIONS: A tapered-shaped tube cuff considerably improves air-sealing characteristics of PVC tube cuffs and allows thereby reducing cuff pressure required for sufficient ventilation. In tube cuffs made of PU that exhibits superior sealing characteristics compared with PVC, a tapered shape failed to result in a further reduction of air leakage.

Closed tracheal suction and fluid aspiration past the tracheal tube. Impact of tube cuff and airway pressure.

BACKGROUND: This study investigated the effect of different tube cuff types and airway pressures on fluid leakage past the tracheal tube cuff during suction with a closed tracheal suction system (CTSS). METHODS: Unlubricated high-volume, low-pressure tracheal tube cuffs made from polyvinylchloride (PVC) and polyurethane (PU) with a size 7.5 mm internal diameter (ID) were placed in a 22 mm ID artificial trachea connected to a test lung and inflated to 25 or 50 cmH2O of cuff pressure. Positive pressure ventilation (PPV) with peak inspiratory pressures of 15, 20 or 25 cmH2O and positive end expiratory pressures (PEEP) of 5 or 10 cmH2O were used. A CTSS catheter (14 Fr) was attached to the tracheal tube and suction was performed for 5, 10, 15 or 20 s with 200 or 300 cmH2O of negative suction pressures. The volume of fluid leaking across the tube cuff at the end of the suction procedure was measured (mL), and the airway pressure was simultaneously recorded. Fluid leakage and airway pressures during different suction conditions were compared using a Kruskal Wallis test and Mann Whitney test (P<0.05). RESULTS: The airway pressure drop during suction was similar for both tube cuffs. The PU tube cuff resulted in significantly less fluid leakage (range 0.00-0.12 mL) than the PVC tube cuff (P<0.001). For the PVC tube cuff, fluid leakage at higher cuff pressures was significantly less (P<0.01).Varying PEEP and PIP did not change the fluid leakage or the drop in airway pressure. CONCLUSION: The use of PU tube cuffs and intermittent transient increases in cuff pressure during suction can effectively reduce fluid leakage past the tracheal tube during closed tracheal suctioning.

Effect of tracheal tube cuff shape on fluid leakage across the cuff: an in vitro study.

BACKGROUND: This study compared the fluid leakage in the new 'tapered' shaped against the classic 'cylindrical' shaped tracheal tube cuffs when placed in different sized tracheas. METHODS: The 7.5 mm internal diameter (ID) tracheal tube cuffs-Tapered Seal Guard (TSG), Standard Seal Guard (SSG), Hi-Lo, Microcuff, Ruesch, and Portex Profile-were compared in an in vitro apparatus. Vertical artificial tracheas with 16, 20, and 22 mm ID were intubated, 5 ml clear water was applied above the unlubricated tube cuffs, and fluid leakage was measured up to 60 min. Data of tapered vs non-tapered tube cuffs (16 observations) were compared for each tracheal diameter using the Mann-Whitney test. RESULTS: Median (range) fluid leakage (ml) at 60 min was 2.14 (0.05-4.88), 1.14 (0.00-4.84), and 0.13 (0.00-1.32), respectively, for 16, 20, and 22 mm tracheas in the TSG tube studies when compared with 4.58 (0.44-4.88), 2.21 (0.00-4.81), and 0.00 (0.00-4.81) in the SSG tube and 4.54 (1.54-4.82), 0.90 (0.00-4.49), and 4.85 (4.40-4.99) in the Microcuff tube studies. Leakage in all polyvinylchloride (PVC) tube cuffs was almost complete (5 ml) within 5 min (P<0.001). CONCLUSIONS: The tapered PU tube cuff was as effective as the cylindrical PU cuffs in smaller tracheal diameters and was more efficient than the cylindrical Microcuff PU tube cuff in larger tracheal diameter in preventing subglottic fluid leakage across the tube cuff tested in this in vitro study. PVC tube cuffs leaked much more and faster than PU cuffs.