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Interrupting gel layer between Double cuffs prevents fluid leakage past tracheal tube cuffs
British Journal of Anaesthesia 111 (3): 496–504 (2013) Advance Access publication 13 May 2013 . doi:10.1093/bja/aet152
RESPIRATION AND THE AIRWAY
Interrupting gel layer between Double cuffs prevents fluid leakage past tracheal tube cuffs J. Y. Hwang 1†, S. H. Han2†, S. H. Park2, S. J. Park 2, S. Park 2, S. H. Oh3 and J. H. Kim2* 1
Department of Anesthesiology and Pain Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, Gyeonggido, Republic of Korea 3 Department of Biostatistics, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea 2
* Corresponding author: Department of Anesthesiology, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707, Republic of Korea. E-mail: [email protected]
Editor’s key points
† Silent aspiration of upper airway secretions is a cause of ventilatorassociated pneumonia in intensive care patients. † This study describes a prototype tracheal tube with double cuffs (Double cuffs) and a gel layer between the Double cuffs to prevent fluid leakage.
Methods. In vitro fluid leakage tests were performed using the Double cuff with or without a gel layer between the two cuffs and four commercially available TTs (Euromedical Standard TT, Mallinckrodt Hi-LoTM , Microcuff, and Mallinckrodt TaperGuardTM ) when placed in artificial tracheas with three-different internal diameters (ID; 16, 20, and 22 mm). Blue-dyed water (5 ml) was placed above the cuff, and the extent of fluid leakage was observed for 48 h. Each test was repeated five times with new tubes at six different intracuff pressures (15, 20, 25, 30, 40, and 50 cm H2O). Results. In all of the conventional TTs and the Double cuff without a gel layer, fluid leakage was observed even at clinically acceptable intracuff pressures (25 –30 cm H2O). However, in the Double cuff with a gel layer, no fluid leakage was observed for 48 h at all intracuff pressures in three-different sized artificial tracheas. At an intracuff pressure of 20 cm H2O in a 20 mm ID trachea, the average volume of injected gel was 2.0 ml. After removal of the TT, the mean volume of the remaining gel in the trachea was 0.10 ml. Conclusions. A prototype TT with gel-layered Double cuffs completely blocked fluid leakage past the cuffs for 48 h in a bench-top model. Clinical studies are required to determine whether this TT reduces the risk of ventilator-associated pneumonia. Keywords: cuffs tracheal, complications; equipment; respiratory aspiration Accepted for publication: 7 March 2013
Ventilator-associated pneumonia is a leading cause of prolonged hospital stay, mortality and morbidity during the postoperative period and in the ICU.1 2 It occurs in 9–27% of intubated patients, and the incidence increases with the duration of ventilation.3 4 Silent aspiration of upper airway secretions, a major cause of ventilator-associated pneumonia, mainly occurs through the longitudinal folds of the high-volume and low-pressure (HVLP) tracheal tube (TT) cuffs, which are inevitably formed upon inflation within the trachea because the cuff diameter is greater than the tracheal diameter.5 6 Several strategies have been considered to prevent aspiration along the longitudinal folds of the cuff, including gel lubrication of TT cuffs7 and modification of cuff designs8 9 or materials.10 11 However, these strategies were not designed †
to prevent the formation of longitudinal folds, a passage of fluids, and therefore they were not able to block aspiration or fluid leakage. The application of positive end-expiratory pressure has been reported to be effective in delaying the passage of fluid around the cuffs as it reduces the pressure gradient across the cuffs.8 12 However, this method also could not completely prevent fluid leakage around cuffs. With HVLP cuffs, interrupting longitudinal folds might be another strategy to fluid leakage around cuffs. We have designed a prototype Double cuff and a small hole in the tube between the two cuffs (Double cuff, Fig. 1). The hole is connected to an external gel port through a secured microtube that enables water-soluble gel to be interposed between the two cuffs. The hypothesis of the present study is
These two authors contributed equally as co-first authors.
& The Author [2013]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: [email protected]
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† Gastric and other fluid can leak around a tracheal tube (TT) cuff, despite appropriate levels of cuff inflation.
Background. Current tracheal tubes (TTs) cannot guarantee a perfect seal against pulmonary aspiration of upper airway secretions. The purpose of this study was to investigate whether a gel layer between the tracheal tube with double cuffs (Double cuffs) prevents fluid leakage past TT cuffs.
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Gel between Double cuffs against fluid leakage
Cuff balloon line Gel line
Hole
that a gel layer between Double cuffs will completely prevent fluid leakage past the cuffs. To verify our hypothesis, we investigated the efficacy of the Double cuff with gel in preventing fluid leakage using a bench-top model and compared it with various TTs from different manufacturers.
Methods Tube modifications We obtained two cuffs from conventionald TTs (Euromedical, Malaysia) and attached them to a tube [8.0 mm internal diameter (ID)]. The cuffs were placed 5 mm apart, making the full length of the attached cuffs 45 mm (Fig. 1). Each cuff is cylindrical in shape (28 mm diameter) and made of polyvinylchloride (PVC). Between the cuffs, the tube has a small hole (1 mm diameter), which is connected to an external gel port through a microtube for importing water-soluble gel (Viasysw electrolyte gel, MVAP Medical Supplies, Inc., UK).
Experimental materials We tested fluid leakage around the cuffs using the Double cuff and four commercially available TTs (8.0 mm ID): Standard TT (Euromedical, Malaysia), Hi-LoTM (Mallinckrodt, Athlone, Ireland), TaperGuardTM (Mallinckrodt, Athlone, Ireland), and Microcuff (Kimberly Clark, GA, USA). The geometric characteristics of the cuffs are presented in Table 1. For the Double cuff, leakage tests were performed with gel (Double cuff with gel) or without gel (Double cuff without gel) between the cuffs.
Table 1 Characteristics of the TT cuffs (ID 8.0 mm). TT, tracheal tube; Double cuff, tracheal tube with double cuffs; PVC, polyvinylchloride; PU, polyurethane Type of TTs
Material
Shape
Diameter (mm)
Length (mm)
Conventional TT (Euromedical, Malaysia)
PVC
Cylindrical
28.0
35.0
Hi-LoTM (Mallinckrodt, Athlone, Ireland)
PVC
Cylindrical
33.0
45.0
TaperGuardTM (Mallinckrodt, Athlone, Ireland)
PVC
Conical
25.4
40.0
Microcuff (Kimberly Clark, GA, USA)
PU
Cylindrical
24.0
47.0
Double cuff prototype
PVC
Cylindrical
28.0
45.0
Fluid leakage test PVC tracheas with three IDs (16, 20, and 22 mm) corresponding to the range of human tracheal size13 were intubated with each type of TT. The leakage tests were performed at intracuff pressures of 15, 20, 25, 30, 40, and 50 cm H2O. The test pressures were supplied and measured by a handheld aneroid
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Fig 1 A prototype Double cuff. Between the two cuffs, there is a small hole (1 mm diameter), which is connected to a gel line for importing watersoluble gel (dotted circle).
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different tubes were compared using Kruskal– Wallis tests followed by the post hoc Mann –Whitney U-test. For multiple comparisons, we compared data in the Double cuff with gel to those in each group, and then compared data in the conventional TT to those in each group. The number of comparisons in each set was five. Bonferroni-adjusted P-values were obtained by multiplying the unadjusted P-value by the number of comparisons (i.e. 5) and was denoted by ‘corrected P’. A corrected P-value ,0.05 was considered to be significant.
Results
manometer (VBM, Germany) connected to a pilot balloon. For the Double cuff with gel, the cuffs were inflated to an initial pressure that was 5 cm H2O lower than the test pressure using the manometer: next, water-soluble gel was injected through the gel port until the intracuff pressure reached the test pressure. The lower border of each cuff was placed 2.5 cm above the lower tracheal edge, and a water trap was positioned below the model trachea to collect water leakage. Bluedyed water (5 ml) was placed above the cuff. The fluid leakage test in the Double cuff with gel is shown in Figure 2. The volume of fluid leakage was measured at 0, 1, 2, 3, 4, 5, 10, 15, 30, and 60 min until all of the water was collected or until the 48 h test period had ended. The experiment was repeated five times with new TTs of each type. The average flow across the cuffs was calculated by dividing the volume of water collected by either 60 min or the time at which all 5 ml of water had leaked. Additionally, a fluid leakage test for 5 days was performed with the Double cuff with gel in a 20 mm ID artificial trachea while maintaining the intracuff pressure at 20 cm H2O to verify its long-term sealing effect. For the fluid leakage test at an intracuff pressure of 20 cm H2O in the 20 mm ID artificial trachea, the injected gel volume and the amount of remnant gel after removal of TT were recorded.
Statistical analysis SPSS software (version 15) was used for statistical analysis. Data were expressed as mean (SD) or amount. The rate and amount of fluid leakage at each intracuff pressure in the
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Bench-top tests We performed two additional bench-top tests using (i) the subglottic suction TT (Hi-LoTM EVAC, Mallinckrodt, USA) with or without gel and (ii) saline as an inflating material with Conventional TT, Double cuff without gel, and Double cuff with gel. Details about the additional experiments are given as a Supplementary data file.
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Fig 2 Fluid leakage test in the Double cuff with gel at an intracuff pressure of 20 cm H2O in a 20 mm ID artificial trachea.
The rate of fluid leakage past TT cuffs for 60 min at each intracuff pressure is presented in Table 2. The Double cuff without gel showed a significantly lower leakage rate compared with the Standard TT mainly at high intracuff pressures (.30 cm H2O), but the leakage rate was significantly higher than that of the Double cuff with gel at all intracuff pressures (15 –50 cm H2O) and in all artificial trachea sizes. The leakage rates of TaperGuard and Microcuff were lower than those of the conventional TT, but were higher than those of the Double cuff with gel at low-intracuff pressures (15–30 cm H2O) (Table 2, Fig. 3). The volume of fluid leaked over 48 h is given in Table 3. For the conventional TT, the loaded fluid (5 ml) leaked completely, regardless of intracuff pressures in all of the artificial tracheas. In terms of leakage amounts, there was no difference among the conventional TT, Double cuff without gel and Hi-Lo. TaperGuard and Microcuff showed significantly smaller leakage volumes compared with the conventional TT at higher intracuff pressures (.30 cm H2O) but not at lower pressures (,25 cm H2O). On the other hand, the Double cuff with gel showed no fluid leakage for 48 h at all intracuff pressures in all artificial trachea sizes. Moreover, there was no leakage over the course of 5 days in the Double cuff with gel at an intracuff pressure of 20 cm H2O in the 20 mm ID artificial trachea. The injected gel volume for the Double cuff was 2.0 (0.4) ml to achieve an intracuff pressure of 20 cm H2O in the 20 mm ID artificial trachea. During the gel injection, the intracuff pressure did not change until the intercuff space was filled with the gel. After the intercuff space was filled, the gel started to fill several of the longitudinal folds, resulting in both a conformational change in the cuff shape and an increase in intracuff pressure (Fig. 4). After the Double cuff was removed from the trachea, most of the gel remained on the intercuff portion of the Double cuff, and the amount of remnant gel in the trachea was 0.10 (0.04) ml, which was 4.96 (1.83) % of the injected volume.
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Gel between Double cuffs against fluid leakage
Table 2 The rate of fluid leakage (ml min21) past the TTcuffs for 60 min at intracuff pressures of 15, 20, 25, 30, 40, or 50 cm H2O in artificial tracheas with ID of 16, 20, or 22 mm. Values are means (SD). Double cuff, tracheal tube with double cuffs; Corrected P a, compared with Double cuff with gel; Corrected P b, compared with Standard TT Intracuff pressure (cm H2O)
Conventional TT
Double cuff without gel
Hi-LoTM
TaperGuardTM
Microcuff
Double cuff with gel
0.00 (0.00)
16 mm 15 Corrected Pa
21.85 (3.14)
8.15 (5.41)
6.77 (3.44)
18.26 (14.37)
0.06 (0.02)
0.040
0.040
0.040
0.040
0.040
Corrected P b 20 Corrected Pa
0.040
0.040
0.755
0.040
0.040
13.13 (3.74)
4.90 (5.28)
2.26 (0.84)
2.04 (1.16)
0.04 (0.01)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
Corrected P b 25 Corrected Pa
0.160
0.040
0.040
0.040
0.040
10.32 (4.09)
3.32 (3.03)
1.86 (0.97)
1.00 (0.84)
0.02 (0.01)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
Corrected P b 30 Corrected Pa
0.080
0.040
0.040
0.040
0.040
8.55 (5.21)
1.67 (1.40)
1.38 (0.72)
0.03 (0.02)
0.01 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
Corrected P b Corrected Pa
0.080
0.080
0.040
0.040
0.040
5.30 (2.85)
1.85 (1.73)
0.76 (0.57)
(0.00)
0.01 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.160
0.160
Corrected P b 50 Corrected Pa
0.160
0.080
0.040
0.040
0.040
3.72 (2.20)
1.27 (0.86)
0.52 (0.33)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
0.040
0.040
0.040
0.040
0.040
21.86 (9.23)
6.73 (5.45)
6.03 (2.31)
13.04 (12.34)
0.21 (0.17)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
Corrected P b
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40
20 mm 15 Corrected Pa Corrected P b 20 Corrected Pa
0.160
0.080
1.000
0.040
0.040
14.07 (8.34)
2.67 (2.56)
2.11 (0.29)
0.47 (0.59)
0.02 (0.01)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.160
Corrected P b 25 Corrected Pa
0.040
0.080
0.040
0.040
0.040
7.12 (8.03)
2.77 (0.75)
1.79 (0.40)
(0.01)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
1.000
Corrected P b 30 Corrected Pa
0.475
0.040
0.040
0.040
0.040
4.42 (3.50)
0.83 (0.77)
1.38 (0.72)
0.01 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
Corrected P b 40 Corrected Pa
0.160
0.475
0.040
0.040
0.040
3.47 (3.50)
0.20 (0.13)
0.31 (0.26)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
Corrected P b 50 Corrected Pa
0.040
0.040
0.040
0.040
0.040
2.46 (3.34)
0.12 (0.10)
0.24 (0.32)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
0.040
0.040
0.040
0.040
0.040 0.00 (0.00)
Corrected P b 22 mm 15 Corrected Pa
45.18 (19.37)
13.45 (9.95)
8.83 (4.28)
1.35 (0.84)
0.08 (0.03)
0.04
0.040
0.040
0.040
0.040
Corrected P b 20 Corrected Pa
0.160
0.040
0.040
0.040
0.040
27.95 (10.37)
5.56 (5.18)
2.74 (2.01)
0.32 (0.28)
0.08 (0.06)
0 .00 (0.00)
0.04
0.040
0.040
0.040
0.040
Corrected P b 25 Corrected Pa
0.080
0.040
0.040
0.040
0.040
16.13 (3.52)
2.00 (2.24)
1.27 (1.06)
0.05 (0.8)
0.00 (0.00)
0 .00 (0.00)
0.04
0.040
0.040
0.040
1.000
0.040
0.040
0.040
0.040
0.040
1.08 (1.20)
1.08 (1.03)
0.03 (0.04)
0.00 (0.00)
0.00 (0.00)
Corrected P b 30
11.62 (2.93)
Continued
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Table 2 Continued Intracuff pressure (cm H2O) Corrected P
a
Conventional TT 0.040
Corrected P b 40
6.99 (4.17)
Corrected Pa
0.04
Corrected P b 50
5.28 (2.89)
Corrected Pa
0.04
Corrected P b
Volume of leakage (ml)
Double cuff with gel
0.040
0.040
0.160
1.000
0.040
0.040
0.040
0.040
0.41 (0.62)
0.42 (0.52)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
1.000
1.000
0.040
0.040
0.040
0.040
0.040
0.26 (0.47)
0.16 (0.26)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
1.000
1.000
0.040
0.080
0.040
0.040
*
Standard TT Double cuff without gel
Hi-LoTM TaperGuardTM
Microcuff
Double cuff with gel
*
*
0.040
*
*
*
*
*
*
*
*
*
*
* 4
Microcuff
* *
* *
*
3
* *† *†
2 *† *†
1
0
†
† †
1 min
2 min
†
†
†
†
3 min
4 min
† †
† 5 min
†
†
†
†
†
†
†
10 min 15 min 30 min 60 min
† 48 h
Time Fig 3 Fluid leakage past the TT cuff over time in a 20 mm ID artificial trachea at an intracuff pressure of 20 cm H2O. Values are presented as means (SD). *Corrected P,0.05 compared with Double cuff with gel. †Corrected P,0.05 compared with Standard TT.
Discussion We designed a prototype Double cuff, and compared the sealing characteristics of the Double cuff without gel, the Double cuff with gel and other commercially available TTs. The main finding in this in vitro study was that the fluid leakage rate for 60 min at low-intracuff pressures was significantly lower in the Double cuff with gel compared with all other TTs. In addition, the Double cuff with gel was the only one that completely prevented fluid leakage over the 48-h observation period at all intracuff pressures (15–50 cm H2O) in three-different-sized artificial tracheas. In the present study, conventional or cylindrical-shaped PVC cuffs (Standard TT and Hi-LoTM ) showed multiple longitudinal folds when inflated within the trachea and they did not
500
prevent fluid leakage, even at an intracuff pressure of 50 cm H2O. The taper-shaped PVC cuff (TaperGuardTM ) is designed to offer a sealing zone in which the outer diameter of the cuff corresponds to the ID of the trachea.9 14 Although the tapershaped PVC cuff presented a significantly improved sealing effect compared with the conventional PVC cuffs, it could not completely block leakage past the cuff during 48 h at an intracuff pressure of 15 –30 cm H2O in any of the trachea sizes. The Microcuff HVLP cuff made from ultrathin (7 mm) polyurethane has been reported to prevent fluid leakage for 60 min within an acceptable intracuff pressure range (25 –30 cm H2O).11 According to their findings, when the Microcuff TT cuff was inflated within the trachea, fewer longitudinal folds occurred on the cuff, which resulted in a prominent sealing
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*
*
TaperGuardTM
0.040
6
5
Hi-LoTM
Double cuff without gel
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Gel between Double cuffs against fluid leakage
Table 3 The volume of fluid leakage (ml) after 48 h. Values are means (SD). Double cuff, tracheal tube with double cuffs; Corrected Pa, compared with Double cuff with gel; Corrected P b, compared with Standard TT Intracuff pressure (cm H2O)
Standard TT
Double cuff without gel
Hi-LoTM
TaperGuardTM
Microcuff
Double cuff with gel
0.00 (0.00)
16 mm 15 Corrected Pa
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
4.90 (0.22)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
3.90 (1.52)
2.34 (0.24)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
3.20 (1.89)
1.18 (0.20)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
0.755
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
1.60 (0.99)
0.30 (0.28)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.755
1.000
1.000
0.040
0.040
0.040 0.00 (0.00)
Corrected P b 20 Corrected Pa Corrected P b 25 Corrected Pa Corrected P b 30 Corrected Pa Corrected P b 40 Corrected Pa Corrected P b 50 Corrected Pa Corrected P b
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5.00 (0.00) 0.040
20 mm 15 Corrected Pa
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
3.30 (1.85)
1.52 (1.99)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.160
1.000
1.000
0.755
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
2.96 (1.90)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
2.16 (1.82)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.20 (0.27)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
4.20 (1.10)
5.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
4.70 (0.67)
4.10 (1.24)
3.80 (1.15)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
0.755
0.040
5.00 (0.00)
5.00 (0.00)
4.64 (0.80)
3.52 (1.56)
2.74 (2.07)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
0.755
0.755
0.040
5.00 (0.00)
5.00 (0.00)
4.60 (0.65)
3.18 (1.71)
0.80 (0.76)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.160
Corrected P b 20 Corrected Pa Corrected P b 25 Corrected Pa Corrected P b 30 Corrected Pa Corrected P b 40 Corrected Pa Corrected P b 50 Corrected Pa Corrected Pb
0.00 (0.00)†
22 mm 15 Corrected Pa Corrected P b 20 Corrected Pa Corrected P b 25 Corrected Pa Corrected P b 30 Corrected Pa
Continued
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Table 3 Continued Intracuff pressure (cm H2O) Corrected P 40 Corrected Pa
Corrected Pa Corrected P b
A
TaperGuardTM
Double cuff without gel 1.000
1.000
0.755
0.040
0.040
5.00 (0.00)
5.00 (0.00)
4.32 (1.00)
0.76 (0.83)
0.30 (0.45)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
4.06 (1.52)
3.76 (1.33)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
1.000
0.755
0.040
0.040
Corrected P b 50
Hi-LoTM
Standard TT
b
Microcuff
Double cuff with gel
0.040
B
characteristic. However, Dave and colleagues9 performed in vitro fluid leakage tests with various TTs in different-sized tracheas (16, 20, and 22 mm ID) for 60 min and demonstrated that the Microcuff TTcuff sealed well in 16 and 20 mm tracheas but the sealing effect was not satisfactory especially in the 22 mm trachea. In the present study, we observed the fluid leakage for 48 h and the Microcuff TT cuff sealed effectively in 20 mm ID trachea, but not in the 16 and 22 mm tracheas at intracuff pressures of 25 and 30 cm H2O. Thus, modifications of the cuff design or changes in the material could reduce, but not completely block, the leakage of fluid around the cuffs. We designed the prototype TT (Double cuff) with two PVC cuffs used for the conventional TT, and placed them 5 mm apart to make a space between the cuffs. This space was intended to be filled with gel and to block the connection between the longitudinal folds of the two cuffs. In this experiment, the Double cuff without gel was not free from leaks, even when the intracuff pressure increased to 50 cm H2O but the Double cuff with gel did not allow any leaks for 48 h, irrespective of the tracheal size. Moreover, the Double cuff with gel completely prevented leakage for 5 days, even at an intracuff
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pressure of 20 cm H2O. These results support our hypothesis that interruption of the longitudinal folds can block the leakage past the cuff. The water-soluble gel was chosen as a filling material between the cuffs based on its pliability, durability, and lack of chemical reactivity. Although there is no precise explanation of the role the gel played between the two cuffs, we believe that by interrupting the longitudinal folds, the gel interposed in the intercuff space plays a major role in preventing leaks. In addition, some portion of gel infiltrating the folds might contribute directly by blocking up channels. There are factors associated with the gel injection into the intercuff space that must be considered. First, the space should be filled completely without leaving empty space such that the gel blocks all of the connections from the upper to the lower folds formed in the cuffs. Detecting the complete filling of the space, however, is not easy, unless the trachea is transparent. Secondly, the volume of the injected gel needs to be minimized to prevent the production of detrimentally high trans-tracheal pressure. In this study, we observed that the intracuff pressure rose only after the filling was complete. Therefore, we filled the space with the gel until the intracuff
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Fig 4 Intercuff gel with Double cuff in an artificial trachea and the gel after removal of the Double cuff from the trachea. (A) After filling the intercuff space, the gel started to fill some of the longitudinal folds. (B) After removal of the Double cuff, most of the gel remained on the intercuff portion of the Double cuff.
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Gel between Double cuffs against fluid leakage
Supplementary material Supplementary material is available at British Journal of Anaesthesia online.
Authors’ contributions J.Y.H. helped to design the study, conduct the study, analyse the data, write the manuscript, prepare the revision letter, and revise the manuscript. S.H.H. helped to design the study, conduct the study, analyse the data, write the manuscript, and revise the manuscript. S.H.P. helped design the study, and analyse the data. S.J.P. helped conduct the study. S.P. helped conduct the study. S.H.O. helped to analyse the data. J.H.K. helped to design the study, conduct the study, analyse the data, write the manuscript, prepare the revision letter, and revise the manuscript.
Declaration of interest None of the authors have any competing interest to declare.
Funding This work was supported by grant 02 –2011 –035 from the SNUBH Research Fund.
References 1 Jacobs R, Wiener-Kronish J. Endotracheal tubes: the conduit for oral and nasal microbial communities to the lungs. Anesthesiology 2006; 104: 224– 5 2 Kollef MH. Prevention of hospital-associated pneumonia and ventilator-associated pneumonia. Crit Care Med 2004; 32: 1396– 405 3 Chastre J, Fagon JY. Ventilator-associated pneumonia. Am J Respir Crit Care Med 2002; 165: 867– 903 4 Pneumatikos IA, Dragoumanis CK, Bouros DE. Ventilator-associated pneumonia or endotracheal tube-associated pneumonia? An approach to the pathogenesis and preventive strategies emphasizing the importance of endotracheal tube. Anesthesiology 2009; 110: 673– 80 5 Pavlin EG, VanNimwegan D, Hornbein TF. Failure of a highcompliance low-pressure cuff to prevent aspiration. Anesthesiology 1975; 42: 216– 9 6 Young PJ, Blunt MC. Improving the shape and compliance characteristics of a high-volume, low-pressure cuff improves tracheal seal. Br J Anaesth 1999; 83: 887– 9 7 Blunt MC, Young PJ, Patil A, Haddock A. Gel lubrication of the tracheal tube cuff reduces pulmonary aspiration. Anesthesiology 2001; 95: 377– 81 8 Lucangelo U, Zin WA, Antonaglia V, et al. Effect of positive expiratory pressure and type of tracheal cuff on the incidence of aspiration in mechanically ventilated patients in an intensive care unit. Crit Care Med 2008; 36: 409– 13 9 Dave MH, Frotzler A, Spielmann N, Madjdpour C, Weiss M. Effect of tracheal tube cuff shape on fluid leakage across the cuff: an in vitro study. Br J Anaesth 2010; 105: 538–43 10 Poelaert J, Depuydt P, De Wolf A, Van de Velde S, Herck I, Blot S. Polyurethane cuffed endotracheal tubes to prevent early postoperative pneumonia after cardiac surgery: a pilot study. J Thorac Cardiovasc Surg 2008; 135: 771–6
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pressure reached a target level by adding 5 cm H2O to the initial level, which was monitored with a monometer. Based on Pascal’s principle, a pressure exerted anywhere in a confined fluid is transmitted equally in all directions throughout the fluid. In addition, the intercuff pressure might equilibrate with the intracuff pressure. Therefore, we believe that the pressure on the tracheal wall resulting from the gel injection could be checked by monitoring the pressure added to the two cuffs, and gel filling completion. This study has several limitations. First, we performed the fluid leakage test in a vertical bench-top model. Within a human trachea in a semirecumbent position, which is a common posture in the ICU, the sealing characteristics of the gel layer between Double cuffs might be altered under physiological conditions including prolonged exposure to body temperature, friction with the tracheal wall, or tracheal mucus. Although the gel layer is wedged and stabilized between the two pressurized cuffs and can be replenished from outside, maintenance of the gel between the two cuffs in the clinical setting would be a main issue in a future study. Secondly, we used water-soluble gel with a modest viscosity to avoid airway complications. However, there are no data on the safety or toxicity of this gel in the airway. Moreover, microbial colonization in the gel layer could be another potential risk. A new antimicrobial gel material or antibiotic-containing gel can be considered. Using this gel could prevent the gel layer from working as a reservoir or conduit for lower respiratory tract infection. In addition, the antibiotic gel layer could delay or prevent the occurrence of pneumonia via subglottic decontamination. Therefore, development of a nontoxic and water-soluble gel that is resistant to microorganisms in the airway is warranted. In addition, determining a range of viscosities that are effective in leakage prevention is necessary. Thirdly, in the present study, we performed the fluid leakage tests without positive pressure ventilation (PPV). In some benchtop studies, PPV has been used to simulate the real situations of tracheal intubation by taking into consideration the up-and-down movement of the TT within the trachea and the effect of PPV on the sealing capacity of TT cuffs.6 15 16 However, in vitro studies on a new TT cuff’s sealing effect should be performed without PPV. During PPV, the pneumatic effect on the distal cuff tip results in an air column that fills the longitudinal folds, which can prevent fluid leakage past the cuffs, despite the use of a less protective TT.15 Finally, the present leak test was not performed under negative pressure, either. When it comes to negative pressure (inspiration of the patient triggering the ventilator), the risk of aspiration would be more likely than positive pressure. Therefore, a future study with TT cuffs with a gel layer should include an in vivo aspiration test under negative pressure ventilation. In conclusion, our prototype TTcuff with a gel layer can completely block fluid leakage for 48 h. For clinical applications, further modifications and in vivo testing are required. Clinical studies are required to determine whether this TT reduces the risk of ventilator-associated pneumonia.
BJA 11 Dullenkopf A, Gerber A, Weiss M. Fluid leakage past tracheal tube cuffs: evaluation of the new Microcuff endotracheal tube. Intensive Care Med 2003; 29: 1849– 53 12 Ouanes I, Lyazidi A, Danin PE, et al. Mechanical influences on fluid leakage past the tracheal tube cuff in a benchtop model. Intensive Care Med 2011; 37: 695– 700 13 Breatnach E, Abbott GC, Fraser RG. Dimensions of the normal human trachea. Am J Roentgenol 1984; 142: 903– 6 14 Zanella A, Scaravilli V, Isgro S, et al. Fluid leakage across tracheal tube cuff, effect of different cuff material, shape, and positive
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expiratory pressure: a bench-top study. Intensive Care Med 2011; 37: 343– 7 15 Dave MH, Koepfer N, Madjdpour C, Frotzler A, Weiss M. Tracheal fluid leakage in benchtop trials: comparison of static versus dynamic ventilation model with and without lubrication. J Anesth 2010; 24: 247– 52 16 Asai T, Shingu K. Leakage of fluid around high-volume, low-pressure cuffs apparatus A comparison of four tracheal tubes. Anaesthesia 2001; 56: 38–42
Handling editor: P. S. Myles
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504
RESPIRATION AND THE AIRWAY
Interrupting gel layer between Double cuffs prevents fluid leakage past tracheal tube cuffs J. Y. Hwang 1†, S. H. Han2†, S. H. Park2, S. J. Park 2, S. Park 2, S. H. Oh3 and J. H. Kim2* 1
Department of Anesthesiology and Pain Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, Gyeonggido, Republic of Korea 3 Department of Biostatistics, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea 2
* Corresponding author: Department of Anesthesiology, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707, Republic of Korea. E-mail: [email protected]
Editor’s key points
† Silent aspiration of upper airway secretions is a cause of ventilatorassociated pneumonia in intensive care patients. † This study describes a prototype tracheal tube with double cuffs (Double cuffs) and a gel layer between the Double cuffs to prevent fluid leakage.
Methods. In vitro fluid leakage tests were performed using the Double cuff with or without a gel layer between the two cuffs and four commercially available TTs (Euromedical Standard TT, Mallinckrodt Hi-LoTM , Microcuff, and Mallinckrodt TaperGuardTM ) when placed in artificial tracheas with three-different internal diameters (ID; 16, 20, and 22 mm). Blue-dyed water (5 ml) was placed above the cuff, and the extent of fluid leakage was observed for 48 h. Each test was repeated five times with new tubes at six different intracuff pressures (15, 20, 25, 30, 40, and 50 cm H2O). Results. In all of the conventional TTs and the Double cuff without a gel layer, fluid leakage was observed even at clinically acceptable intracuff pressures (25 –30 cm H2O). However, in the Double cuff with a gel layer, no fluid leakage was observed for 48 h at all intracuff pressures in three-different sized artificial tracheas. At an intracuff pressure of 20 cm H2O in a 20 mm ID trachea, the average volume of injected gel was 2.0 ml. After removal of the TT, the mean volume of the remaining gel in the trachea was 0.10 ml. Conclusions. A prototype TT with gel-layered Double cuffs completely blocked fluid leakage past the cuffs for 48 h in a bench-top model. Clinical studies are required to determine whether this TT reduces the risk of ventilator-associated pneumonia. Keywords: cuffs tracheal, complications; equipment; respiratory aspiration Accepted for publication: 7 March 2013
Ventilator-associated pneumonia is a leading cause of prolonged hospital stay, mortality and morbidity during the postoperative period and in the ICU.1 2 It occurs in 9–27% of intubated patients, and the incidence increases with the duration of ventilation.3 4 Silent aspiration of upper airway secretions, a major cause of ventilator-associated pneumonia, mainly occurs through the longitudinal folds of the high-volume and low-pressure (HVLP) tracheal tube (TT) cuffs, which are inevitably formed upon inflation within the trachea because the cuff diameter is greater than the tracheal diameter.5 6 Several strategies have been considered to prevent aspiration along the longitudinal folds of the cuff, including gel lubrication of TT cuffs7 and modification of cuff designs8 9 or materials.10 11 However, these strategies were not designed †
to prevent the formation of longitudinal folds, a passage of fluids, and therefore they were not able to block aspiration or fluid leakage. The application of positive end-expiratory pressure has been reported to be effective in delaying the passage of fluid around the cuffs as it reduces the pressure gradient across the cuffs.8 12 However, this method also could not completely prevent fluid leakage around cuffs. With HVLP cuffs, interrupting longitudinal folds might be another strategy to fluid leakage around cuffs. We have designed a prototype Double cuff and a small hole in the tube between the two cuffs (Double cuff, Fig. 1). The hole is connected to an external gel port through a secured microtube that enables water-soluble gel to be interposed between the two cuffs. The hypothesis of the present study is
These two authors contributed equally as co-first authors.
& The Author [2013]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: [email protected]
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† Gastric and other fluid can leak around a tracheal tube (TT) cuff, despite appropriate levels of cuff inflation.
Background. Current tracheal tubes (TTs) cannot guarantee a perfect seal against pulmonary aspiration of upper airway secretions. The purpose of this study was to investigate whether a gel layer between the tracheal tube with double cuffs (Double cuffs) prevents fluid leakage past TT cuffs.
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Gel between Double cuffs against fluid leakage
Cuff balloon line Gel line
Hole
that a gel layer between Double cuffs will completely prevent fluid leakage past the cuffs. To verify our hypothesis, we investigated the efficacy of the Double cuff with gel in preventing fluid leakage using a bench-top model and compared it with various TTs from different manufacturers.
Methods Tube modifications We obtained two cuffs from conventionald TTs (Euromedical, Malaysia) and attached them to a tube [8.0 mm internal diameter (ID)]. The cuffs were placed 5 mm apart, making the full length of the attached cuffs 45 mm (Fig. 1). Each cuff is cylindrical in shape (28 mm diameter) and made of polyvinylchloride (PVC). Between the cuffs, the tube has a small hole (1 mm diameter), which is connected to an external gel port through a microtube for importing water-soluble gel (Viasysw electrolyte gel, MVAP Medical Supplies, Inc., UK).
Experimental materials We tested fluid leakage around the cuffs using the Double cuff and four commercially available TTs (8.0 mm ID): Standard TT (Euromedical, Malaysia), Hi-LoTM (Mallinckrodt, Athlone, Ireland), TaperGuardTM (Mallinckrodt, Athlone, Ireland), and Microcuff (Kimberly Clark, GA, USA). The geometric characteristics of the cuffs are presented in Table 1. For the Double cuff, leakage tests were performed with gel (Double cuff with gel) or without gel (Double cuff without gel) between the cuffs.
Table 1 Characteristics of the TT cuffs (ID 8.0 mm). TT, tracheal tube; Double cuff, tracheal tube with double cuffs; PVC, polyvinylchloride; PU, polyurethane Type of TTs
Material
Shape
Diameter (mm)
Length (mm)
Conventional TT (Euromedical, Malaysia)
PVC
Cylindrical
28.0
35.0
Hi-LoTM (Mallinckrodt, Athlone, Ireland)
PVC
Cylindrical
33.0
45.0
TaperGuardTM (Mallinckrodt, Athlone, Ireland)
PVC
Conical
25.4
40.0
Microcuff (Kimberly Clark, GA, USA)
PU
Cylindrical
24.0
47.0
Double cuff prototype
PVC
Cylindrical
28.0
45.0
Fluid leakage test PVC tracheas with three IDs (16, 20, and 22 mm) corresponding to the range of human tracheal size13 were intubated with each type of TT. The leakage tests were performed at intracuff pressures of 15, 20, 25, 30, 40, and 50 cm H2O. The test pressures were supplied and measured by a handheld aneroid
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Fig 1 A prototype Double cuff. Between the two cuffs, there is a small hole (1 mm diameter), which is connected to a gel line for importing watersoluble gel (dotted circle).
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different tubes were compared using Kruskal– Wallis tests followed by the post hoc Mann –Whitney U-test. For multiple comparisons, we compared data in the Double cuff with gel to those in each group, and then compared data in the conventional TT to those in each group. The number of comparisons in each set was five. Bonferroni-adjusted P-values were obtained by multiplying the unadjusted P-value by the number of comparisons (i.e. 5) and was denoted by ‘corrected P’. A corrected P-value ,0.05 was considered to be significant.
Results
manometer (VBM, Germany) connected to a pilot balloon. For the Double cuff with gel, the cuffs were inflated to an initial pressure that was 5 cm H2O lower than the test pressure using the manometer: next, water-soluble gel was injected through the gel port until the intracuff pressure reached the test pressure. The lower border of each cuff was placed 2.5 cm above the lower tracheal edge, and a water trap was positioned below the model trachea to collect water leakage. Bluedyed water (5 ml) was placed above the cuff. The fluid leakage test in the Double cuff with gel is shown in Figure 2. The volume of fluid leakage was measured at 0, 1, 2, 3, 4, 5, 10, 15, 30, and 60 min until all of the water was collected or until the 48 h test period had ended. The experiment was repeated five times with new TTs of each type. The average flow across the cuffs was calculated by dividing the volume of water collected by either 60 min or the time at which all 5 ml of water had leaked. Additionally, a fluid leakage test for 5 days was performed with the Double cuff with gel in a 20 mm ID artificial trachea while maintaining the intracuff pressure at 20 cm H2O to verify its long-term sealing effect. For the fluid leakage test at an intracuff pressure of 20 cm H2O in the 20 mm ID artificial trachea, the injected gel volume and the amount of remnant gel after removal of TT were recorded.
Statistical analysis SPSS software (version 15) was used for statistical analysis. Data were expressed as mean (SD) or amount. The rate and amount of fluid leakage at each intracuff pressure in the
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Bench-top tests We performed two additional bench-top tests using (i) the subglottic suction TT (Hi-LoTM EVAC, Mallinckrodt, USA) with or without gel and (ii) saline as an inflating material with Conventional TT, Double cuff without gel, and Double cuff with gel. Details about the additional experiments are given as a Supplementary data file.
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Fig 2 Fluid leakage test in the Double cuff with gel at an intracuff pressure of 20 cm H2O in a 20 mm ID artificial trachea.
The rate of fluid leakage past TT cuffs for 60 min at each intracuff pressure is presented in Table 2. The Double cuff without gel showed a significantly lower leakage rate compared with the Standard TT mainly at high intracuff pressures (.30 cm H2O), but the leakage rate was significantly higher than that of the Double cuff with gel at all intracuff pressures (15 –50 cm H2O) and in all artificial trachea sizes. The leakage rates of TaperGuard and Microcuff were lower than those of the conventional TT, but were higher than those of the Double cuff with gel at low-intracuff pressures (15–30 cm H2O) (Table 2, Fig. 3). The volume of fluid leaked over 48 h is given in Table 3. For the conventional TT, the loaded fluid (5 ml) leaked completely, regardless of intracuff pressures in all of the artificial tracheas. In terms of leakage amounts, there was no difference among the conventional TT, Double cuff without gel and Hi-Lo. TaperGuard and Microcuff showed significantly smaller leakage volumes compared with the conventional TT at higher intracuff pressures (.30 cm H2O) but not at lower pressures (,25 cm H2O). On the other hand, the Double cuff with gel showed no fluid leakage for 48 h at all intracuff pressures in all artificial trachea sizes. Moreover, there was no leakage over the course of 5 days in the Double cuff with gel at an intracuff pressure of 20 cm H2O in the 20 mm ID artificial trachea. The injected gel volume for the Double cuff was 2.0 (0.4) ml to achieve an intracuff pressure of 20 cm H2O in the 20 mm ID artificial trachea. During the gel injection, the intracuff pressure did not change until the intercuff space was filled with the gel. After the intercuff space was filled, the gel started to fill several of the longitudinal folds, resulting in both a conformational change in the cuff shape and an increase in intracuff pressure (Fig. 4). After the Double cuff was removed from the trachea, most of the gel remained on the intercuff portion of the Double cuff, and the amount of remnant gel in the trachea was 0.10 (0.04) ml, which was 4.96 (1.83) % of the injected volume.
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Gel between Double cuffs against fluid leakage
Table 2 The rate of fluid leakage (ml min21) past the TTcuffs for 60 min at intracuff pressures of 15, 20, 25, 30, 40, or 50 cm H2O in artificial tracheas with ID of 16, 20, or 22 mm. Values are means (SD). Double cuff, tracheal tube with double cuffs; Corrected P a, compared with Double cuff with gel; Corrected P b, compared with Standard TT Intracuff pressure (cm H2O)
Conventional TT
Double cuff without gel
Hi-LoTM
TaperGuardTM
Microcuff
Double cuff with gel
0.00 (0.00)
16 mm 15 Corrected Pa
21.85 (3.14)
8.15 (5.41)
6.77 (3.44)
18.26 (14.37)
0.06 (0.02)
0.040
0.040
0.040
0.040
0.040
Corrected P b 20 Corrected Pa
0.040
0.040
0.755
0.040
0.040
13.13 (3.74)
4.90 (5.28)
2.26 (0.84)
2.04 (1.16)
0.04 (0.01)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
Corrected P b 25 Corrected Pa
0.160
0.040
0.040
0.040
0.040
10.32 (4.09)
3.32 (3.03)
1.86 (0.97)
1.00 (0.84)
0.02 (0.01)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
Corrected P b 30 Corrected Pa
0.080
0.040
0.040
0.040
0.040
8.55 (5.21)
1.67 (1.40)
1.38 (0.72)
0.03 (0.02)
0.01 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
Corrected P b Corrected Pa
0.080
0.080
0.040
0.040
0.040
5.30 (2.85)
1.85 (1.73)
0.76 (0.57)
(0.00)
0.01 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.160
0.160
Corrected P b 50 Corrected Pa
0.160
0.080
0.040
0.040
0.040
3.72 (2.20)
1.27 (0.86)
0.52 (0.33)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
0.040
0.040
0.040
0.040
0.040
21.86 (9.23)
6.73 (5.45)
6.03 (2.31)
13.04 (12.34)
0.21 (0.17)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
Corrected P b
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40
20 mm 15 Corrected Pa Corrected P b 20 Corrected Pa
0.160
0.080
1.000
0.040
0.040
14.07 (8.34)
2.67 (2.56)
2.11 (0.29)
0.47 (0.59)
0.02 (0.01)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.160
Corrected P b 25 Corrected Pa
0.040
0.080
0.040
0.040
0.040
7.12 (8.03)
2.77 (0.75)
1.79 (0.40)
(0.01)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
1.000
Corrected P b 30 Corrected Pa
0.475
0.040
0.040
0.040
0.040
4.42 (3.50)
0.83 (0.77)
1.38 (0.72)
0.01 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
Corrected P b 40 Corrected Pa
0.160
0.475
0.040
0.040
0.040
3.47 (3.50)
0.20 (0.13)
0.31 (0.26)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
Corrected P b 50 Corrected Pa
0.040
0.040
0.040
0.040
0.040
2.46 (3.34)
0.12 (0.10)
0.24 (0.32)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
0.040
0.040
0.040
0.040
0.040 0.00 (0.00)
Corrected P b 22 mm 15 Corrected Pa
45.18 (19.37)
13.45 (9.95)
8.83 (4.28)
1.35 (0.84)
0.08 (0.03)
0.04
0.040
0.040
0.040
0.040
Corrected P b 20 Corrected Pa
0.160
0.040
0.040
0.040
0.040
27.95 (10.37)
5.56 (5.18)
2.74 (2.01)
0.32 (0.28)
0.08 (0.06)
0 .00 (0.00)
0.04
0.040
0.040
0.040
0.040
Corrected P b 25 Corrected Pa
0.080
0.040
0.040
0.040
0.040
16.13 (3.52)
2.00 (2.24)
1.27 (1.06)
0.05 (0.8)
0.00 (0.00)
0 .00 (0.00)
0.04
0.040
0.040
0.040
1.000
0.040
0.040
0.040
0.040
0.040
1.08 (1.20)
1.08 (1.03)
0.03 (0.04)
0.00 (0.00)
0.00 (0.00)
Corrected P b 30
11.62 (2.93)
Continued
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Table 2 Continued Intracuff pressure (cm H2O) Corrected P
a
Conventional TT 0.040
Corrected P b 40
6.99 (4.17)
Corrected Pa
0.04
Corrected P b 50
5.28 (2.89)
Corrected Pa
0.04
Corrected P b
Volume of leakage (ml)
Double cuff with gel
0.040
0.040
0.160
1.000
0.040
0.040
0.040
0.040
0.41 (0.62)
0.42 (0.52)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
1.000
1.000
0.040
0.040
0.040
0.040
0.040
0.26 (0.47)
0.16 (0.26)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
1.000
1.000
0.040
0.080
0.040
0.040
*
Standard TT Double cuff without gel
Hi-LoTM TaperGuardTM
Microcuff
Double cuff with gel
*
*
0.040
*
*
*
*
*
*
*
*
*
*
* 4
Microcuff
* *
* *
*
3
* *† *†
2 *† *†
1
0
†
† †
1 min
2 min
†
†
†
†
3 min
4 min
† †
† 5 min
†
†
†
†
†
†
†
10 min 15 min 30 min 60 min
† 48 h
Time Fig 3 Fluid leakage past the TT cuff over time in a 20 mm ID artificial trachea at an intracuff pressure of 20 cm H2O. Values are presented as means (SD). *Corrected P,0.05 compared with Double cuff with gel. †Corrected P,0.05 compared with Standard TT.
Discussion We designed a prototype Double cuff, and compared the sealing characteristics of the Double cuff without gel, the Double cuff with gel and other commercially available TTs. The main finding in this in vitro study was that the fluid leakage rate for 60 min at low-intracuff pressures was significantly lower in the Double cuff with gel compared with all other TTs. In addition, the Double cuff with gel was the only one that completely prevented fluid leakage over the 48-h observation period at all intracuff pressures (15–50 cm H2O) in three-different-sized artificial tracheas. In the present study, conventional or cylindrical-shaped PVC cuffs (Standard TT and Hi-LoTM ) showed multiple longitudinal folds when inflated within the trachea and they did not
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prevent fluid leakage, even at an intracuff pressure of 50 cm H2O. The taper-shaped PVC cuff (TaperGuardTM ) is designed to offer a sealing zone in which the outer diameter of the cuff corresponds to the ID of the trachea.9 14 Although the tapershaped PVC cuff presented a significantly improved sealing effect compared with the conventional PVC cuffs, it could not completely block leakage past the cuff during 48 h at an intracuff pressure of 15 –30 cm H2O in any of the trachea sizes. The Microcuff HVLP cuff made from ultrathin (7 mm) polyurethane has been reported to prevent fluid leakage for 60 min within an acceptable intracuff pressure range (25 –30 cm H2O).11 According to their findings, when the Microcuff TT cuff was inflated within the trachea, fewer longitudinal folds occurred on the cuff, which resulted in a prominent sealing
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*
*
TaperGuardTM
0.040
6
5
Hi-LoTM
Double cuff without gel
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Gel between Double cuffs against fluid leakage
Table 3 The volume of fluid leakage (ml) after 48 h. Values are means (SD). Double cuff, tracheal tube with double cuffs; Corrected Pa, compared with Double cuff with gel; Corrected P b, compared with Standard TT Intracuff pressure (cm H2O)
Standard TT
Double cuff without gel
Hi-LoTM
TaperGuardTM
Microcuff
Double cuff with gel
0.00 (0.00)
16 mm 15 Corrected Pa
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
4.90 (0.22)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
3.90 (1.52)
2.34 (0.24)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
3.20 (1.89)
1.18 (0.20)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
0.755
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
1.60 (0.99)
0.30 (0.28)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.755
1.000
1.000
0.040
0.040
0.040 0.00 (0.00)
Corrected P b 20 Corrected Pa Corrected P b 25 Corrected Pa Corrected P b 30 Corrected Pa Corrected P b 40 Corrected Pa Corrected P b 50 Corrected Pa Corrected P b
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5.00 (0.00) 0.040
20 mm 15 Corrected Pa
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
3.30 (1.85)
1.52 (1.99)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.160
1.000
1.000
0.755
1.000
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
2.96 (1.90)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
2.16 (1.82)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.20 (0.27)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
4.20 (1.10)
5.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
5.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
5.00 (0.00)
5.00 (0.00)
4.70 (0.67)
4.10 (1.24)
3.80 (1.15)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
1.000
0.755
0.040
5.00 (0.00)
5.00 (0.00)
4.64 (0.80)
3.52 (1.56)
2.74 (2.07)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.040
1.000
1.000
0.755
0.755
0.040
5.00 (0.00)
5.00 (0.00)
4.60 (0.65)
3.18 (1.71)
0.80 (0.76)
0.00 (0.00)
0.040
0.040
0.040
0.040
0.160
Corrected P b 20 Corrected Pa Corrected P b 25 Corrected Pa Corrected P b 30 Corrected Pa Corrected P b 40 Corrected Pa Corrected P b 50 Corrected Pa Corrected Pb
0.00 (0.00)†
22 mm 15 Corrected Pa Corrected P b 20 Corrected Pa Corrected P b 25 Corrected Pa Corrected P b 30 Corrected Pa
Continued
501
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Hwang et al.
Table 3 Continued Intracuff pressure (cm H2O) Corrected P 40 Corrected Pa
Corrected Pa Corrected P b
A
TaperGuardTM
Double cuff without gel 1.000
1.000
0.755
0.040
0.040
5.00 (0.00)
5.00 (0.00)
4.32 (1.00)
0.76 (0.83)
0.30 (0.45)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
1.000
1.000
0.040
0.040
0.040
5.00 (0.00)
4.06 (1.52)
3.76 (1.33)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.040
0.040
0.040
1.000
1.000
1.000
0.755
0.040
0.040
Corrected P b 50
Hi-LoTM
Standard TT
b
Microcuff
Double cuff with gel
0.040
B
characteristic. However, Dave and colleagues9 performed in vitro fluid leakage tests with various TTs in different-sized tracheas (16, 20, and 22 mm ID) for 60 min and demonstrated that the Microcuff TTcuff sealed well in 16 and 20 mm tracheas but the sealing effect was not satisfactory especially in the 22 mm trachea. In the present study, we observed the fluid leakage for 48 h and the Microcuff TT cuff sealed effectively in 20 mm ID trachea, but not in the 16 and 22 mm tracheas at intracuff pressures of 25 and 30 cm H2O. Thus, modifications of the cuff design or changes in the material could reduce, but not completely block, the leakage of fluid around the cuffs. We designed the prototype TT (Double cuff) with two PVC cuffs used for the conventional TT, and placed them 5 mm apart to make a space between the cuffs. This space was intended to be filled with gel and to block the connection between the longitudinal folds of the two cuffs. In this experiment, the Double cuff without gel was not free from leaks, even when the intracuff pressure increased to 50 cm H2O but the Double cuff with gel did not allow any leaks for 48 h, irrespective of the tracheal size. Moreover, the Double cuff with gel completely prevented leakage for 5 days, even at an intracuff
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pressure of 20 cm H2O. These results support our hypothesis that interruption of the longitudinal folds can block the leakage past the cuff. The water-soluble gel was chosen as a filling material between the cuffs based on its pliability, durability, and lack of chemical reactivity. Although there is no precise explanation of the role the gel played between the two cuffs, we believe that by interrupting the longitudinal folds, the gel interposed in the intercuff space plays a major role in preventing leaks. In addition, some portion of gel infiltrating the folds might contribute directly by blocking up channels. There are factors associated with the gel injection into the intercuff space that must be considered. First, the space should be filled completely without leaving empty space such that the gel blocks all of the connections from the upper to the lower folds formed in the cuffs. Detecting the complete filling of the space, however, is not easy, unless the trachea is transparent. Secondly, the volume of the injected gel needs to be minimized to prevent the production of detrimentally high trans-tracheal pressure. In this study, we observed that the intracuff pressure rose only after the filling was complete. Therefore, we filled the space with the gel until the intracuff
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Fig 4 Intercuff gel with Double cuff in an artificial trachea and the gel after removal of the Double cuff from the trachea. (A) After filling the intercuff space, the gel started to fill some of the longitudinal folds. (B) After removal of the Double cuff, most of the gel remained on the intercuff portion of the Double cuff.
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Gel between Double cuffs against fluid leakage
Supplementary material Supplementary material is available at British Journal of Anaesthesia online.
Authors’ contributions J.Y.H. helped to design the study, conduct the study, analyse the data, write the manuscript, prepare the revision letter, and revise the manuscript. S.H.H. helped to design the study, conduct the study, analyse the data, write the manuscript, and revise the manuscript. S.H.P. helped design the study, and analyse the data. S.J.P. helped conduct the study. S.P. helped conduct the study. S.H.O. helped to analyse the data. J.H.K. helped to design the study, conduct the study, analyse the data, write the manuscript, prepare the revision letter, and revise the manuscript.
Declaration of interest None of the authors have any competing interest to declare.
Funding This work was supported by grant 02 –2011 –035 from the SNUBH Research Fund.
References 1 Jacobs R, Wiener-Kronish J. Endotracheal tubes: the conduit for oral and nasal microbial communities to the lungs. Anesthesiology 2006; 104: 224– 5 2 Kollef MH. Prevention of hospital-associated pneumonia and ventilator-associated pneumonia. Crit Care Med 2004; 32: 1396– 405 3 Chastre J, Fagon JY. Ventilator-associated pneumonia. Am J Respir Crit Care Med 2002; 165: 867– 903 4 Pneumatikos IA, Dragoumanis CK, Bouros DE. Ventilator-associated pneumonia or endotracheal tube-associated pneumonia? An approach to the pathogenesis and preventive strategies emphasizing the importance of endotracheal tube. Anesthesiology 2009; 110: 673– 80 5 Pavlin EG, VanNimwegan D, Hornbein TF. Failure of a highcompliance low-pressure cuff to prevent aspiration. Anesthesiology 1975; 42: 216– 9 6 Young PJ, Blunt MC. Improving the shape and compliance characteristics of a high-volume, low-pressure cuff improves tracheal seal. Br J Anaesth 1999; 83: 887– 9 7 Blunt MC, Young PJ, Patil A, Haddock A. Gel lubrication of the tracheal tube cuff reduces pulmonary aspiration. Anesthesiology 2001; 95: 377– 81 8 Lucangelo U, Zin WA, Antonaglia V, et al. Effect of positive expiratory pressure and type of tracheal cuff on the incidence of aspiration in mechanically ventilated patients in an intensive care unit. Crit Care Med 2008; 36: 409– 13 9 Dave MH, Frotzler A, Spielmann N, Madjdpour C, Weiss M. Effect of tracheal tube cuff shape on fluid leakage across the cuff: an in vitro study. Br J Anaesth 2010; 105: 538–43 10 Poelaert J, Depuydt P, De Wolf A, Van de Velde S, Herck I, Blot S. Polyurethane cuffed endotracheal tubes to prevent early postoperative pneumonia after cardiac surgery: a pilot study. J Thorac Cardiovasc Surg 2008; 135: 771–6
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pressure reached a target level by adding 5 cm H2O to the initial level, which was monitored with a monometer. Based on Pascal’s principle, a pressure exerted anywhere in a confined fluid is transmitted equally in all directions throughout the fluid. In addition, the intercuff pressure might equilibrate with the intracuff pressure. Therefore, we believe that the pressure on the tracheal wall resulting from the gel injection could be checked by monitoring the pressure added to the two cuffs, and gel filling completion. This study has several limitations. First, we performed the fluid leakage test in a vertical bench-top model. Within a human trachea in a semirecumbent position, which is a common posture in the ICU, the sealing characteristics of the gel layer between Double cuffs might be altered under physiological conditions including prolonged exposure to body temperature, friction with the tracheal wall, or tracheal mucus. Although the gel layer is wedged and stabilized between the two pressurized cuffs and can be replenished from outside, maintenance of the gel between the two cuffs in the clinical setting would be a main issue in a future study. Secondly, we used water-soluble gel with a modest viscosity to avoid airway complications. However, there are no data on the safety or toxicity of this gel in the airway. Moreover, microbial colonization in the gel layer could be another potential risk. A new antimicrobial gel material or antibiotic-containing gel can be considered. Using this gel could prevent the gel layer from working as a reservoir or conduit for lower respiratory tract infection. In addition, the antibiotic gel layer could delay or prevent the occurrence of pneumonia via subglottic decontamination. Therefore, development of a nontoxic and water-soluble gel that is resistant to microorganisms in the airway is warranted. In addition, determining a range of viscosities that are effective in leakage prevention is necessary. Thirdly, in the present study, we performed the fluid leakage tests without positive pressure ventilation (PPV). In some benchtop studies, PPV has been used to simulate the real situations of tracheal intubation by taking into consideration the up-and-down movement of the TT within the trachea and the effect of PPV on the sealing capacity of TT cuffs.6 15 16 However, in vitro studies on a new TT cuff’s sealing effect should be performed without PPV. During PPV, the pneumatic effect on the distal cuff tip results in an air column that fills the longitudinal folds, which can prevent fluid leakage past the cuffs, despite the use of a less protective TT.15 Finally, the present leak test was not performed under negative pressure, either. When it comes to negative pressure (inspiration of the patient triggering the ventilator), the risk of aspiration would be more likely than positive pressure. Therefore, a future study with TT cuffs with a gel layer should include an in vivo aspiration test under negative pressure ventilation. In conclusion, our prototype TTcuff with a gel layer can completely block fluid leakage for 48 h. For clinical applications, further modifications and in vivo testing are required. Clinical studies are required to determine whether this TT reduces the risk of ventilator-associated pneumonia.
BJA 11 Dullenkopf A, Gerber A, Weiss M. Fluid leakage past tracheal tube cuffs: evaluation of the new Microcuff endotracheal tube. Intensive Care Med 2003; 29: 1849– 53 12 Ouanes I, Lyazidi A, Danin PE, et al. Mechanical influences on fluid leakage past the tracheal tube cuff in a benchtop model. Intensive Care Med 2011; 37: 695– 700 13 Breatnach E, Abbott GC, Fraser RG. Dimensions of the normal human trachea. Am J Roentgenol 1984; 142: 903– 6 14 Zanella A, Scaravilli V, Isgro S, et al. Fluid leakage across tracheal tube cuff, effect of different cuff material, shape, and positive
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expiratory pressure: a bench-top study. Intensive Care Med 2011; 37: 343– 7 15 Dave MH, Koepfer N, Madjdpour C, Frotzler A, Weiss M. Tracheal fluid leakage in benchtop trials: comparison of static versus dynamic ventilation model with and without lubrication. J Anesth 2010; 24: 247– 52 16 Asai T, Shingu K. Leakage of fluid around high-volume, low-pressure cuffs apparatus A comparison of four tracheal tubes. Anaesthesia 2001; 56: 38–42
Handling editor: P. S. Myles
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