Department of Anaesthesiology, National Defense Medical College, Tokorozawa, Saitama 359-8513, Japan*Corresponding author
Accepted for publication: March 18, 2002
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Abstract |
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Methods. The pressure in an air-filled cuff of the BrandtTM system (Mallinckrodt BrandtTM tracheal tube, n=60) was recorded during anaesthesia with 67% nitrous oxide; gas volume and concentration in cuffs and balloons were measured for up to 12 h from the start of anaesthesia. The volume change of each gas was calculated to assess its contribution to the cuff pressure. We also measured cuff compliance in vitro.
Results. Cuff pressure increased slightly during anaesthesia (P<0.05). The nitrous oxide concentration increased to 47.7 (8.2)% (mean (SD)) in the cuff and to 2.2 (0.9)% in the pilot balloon. The nitrous oxide volume in the cuff and pilot balloon increased by approximately 2 ml during the first 4 h of anaesthesia. The carbon dioxide volume increased slightly, and nitrogen and oxygen did not change significantly. The compliance of the BrandtTM tube cuff was six times greater than that of a standard tube cuff (Mallinckrodt Hi-ContourTM tracheal tube).
Conclusions. The BrandtTM tracheal tube maintains stable cuff pressure during nitrous oxide anaesthesia because of a highly compliant balloon. The concentration gradient of nitrous oxide between the cuff and pilot balloon also contributes to the stable-cuff pressure because the high nitrous oxide concentration in the cuff reduces nitrous oxide influx.
Br J Anaesth 2002; 89: 2716
Keywords: anaesthetics gases, nitrous oxide; equipment, cuffs tracheal; equipment, tubes tracheal
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Introduction |
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Compliance of the cuff determines cuff pressure during anaesthesia because intra-cuff pressure depends on the volume of gases in the cuff and cuff compliance. Highly compliant cuffs limit the increases in cuff pressure during anaesthesia with nitrous oxide.7 Because Brandt and Pokar9 reported that the pilot balloon of the system is thin, we hypothesized that the high compliance of the BrandtTM system contributes to the stable-cuff pressure.
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Methods |
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Experimental procedure
Intra-cuff pressure was measured every 10 min during anaesthesia. Studies were completed at 0.5, 1, 2, 4, 8, and 12 h (group 0.5H, 1H, 2H, 4H, 8H, and 12H; n=10 for each). At the end of the study, the connecting tube was clamped approximately 2 cm from the pilot balloon and the pilot balloon was aspirated as much as possible. The connecting tube was then unclamped and the cuff was aspirated separately from the pilot balloon. Approximately 15 min later, the volume of aspirated gases was measured at room temperature using a calibrated syringe, after the gases had been first compressed and then decompressed. We took the mean value to avoid a possible error due to friction between the barrel and piston of the syringe. The nitrous oxide concentration was assayed using quadropole mass- spectrometry (AMIS 2000, INNVISION A/S, Odense, Denmark), which was calibrated with standard gases.
Data analysis
Correction of gas concentrations
The dead volume of the pilot balloon (Vdead[pb]) was estimated at 1.3 ml (Appendix). Because Vdead[pb] dilutes the concentration of each gas aspirated from the cuff (Casp), the actual concentration of each gas in the cuff should be corrected and was calculated using the following formula:
(CaspxVaspCasp[pb]xVdead[pb])/(VaspVdead[pb])(1)
where Vasp and Casp[pb] denote the volume aspirated from cuffs and gas concentration in the pilot balloon, respectively.
Estimation of volume change of each gas
Because gas concentration in the cuff or pilot balloon is affected by volume changes of other gases, volume change of each gas is required to assess the contribution toward a change in cuff pressure. The injected volume of each gas was calculated using the following formula:
(Vinj+Vdead[cuff]+Vdead[pb])xCair(2)
where Vinj, Vdead[cuff], and Cair denotes injected volume, dead volume of the cuff, and gas concentration in the air, respectively. Vdead[cuff] was estimated at 0.2 ml (Appendix). The aspirated volume of each gas was calculated using the following formula:
(Vasp[cuff]+Vdead[cuff])xCasp[cuff] +(Vasp[pb]+Vdead[pb])xCasp[pb](3)
where Vasp[cuff], Vasp[pb], and Casp[cuff] denote the volume aspirated from the cuff and pilot balloon, and gas concentration in the cuff, respectively. Consequently, the volume change was Equation 2-Equation 3.
Measurement of compliance in vitro
To assess the volumepressure relationship of the BrandtTM system, the pilot balloon and the cuff of the Hi-Contour BrandtTM and the Hi-ContourTM (n=5 for each) tracheal tubes were inflated with air, 2 ml at a time, using a syringe. Then the connection tubes of the BrandtTM tracheal tubes (n=5) were cut 2 cm from the pilot balloon. The pilot balloon and the cuff were inflated separately with air, 0.5 or 1 ml at a time. The inflated volume and the intra-cuff pressure were recorded. The Hi-ContourTM tracheal tube is a standard tracheal tube and has the same type and volume of cuff as the Hi-Contour BrandtTM tracheal tube. In addition, the tracheal tube (n=5) was placed in an 18.2-mm diameter glass tube (approximately the same cross-sectional diameter as an adult female trachea), and the intact BrandtTM system or cuff only was inflated with air to measure the volumepressure relationship in a condition similar to the clinical situation. Compliance of the cuff or balloon was calculated as the reciprocal of the gradient (i.e. elastance) of the relationship at 15 mm Hg.
Statistical analysis
Data were presented as the number of patients or mean (SD). Two-way analysis of variance (ANOVA) for repeated measurements was used to assess changes over time within, as well as between, groups and one-way ANOVA was performed to compare raw data between groups. Post hoc analysis to allow for multiple comparisons was performed using the BonferroniDunn correction. Students t-test was used to make single comparisons of cuff pressure, volume, and concentration of nitrous oxide. Proportional data were evaluated using the chi-square test. A P-value of <0.05 was considered to be statistically significant.
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Results |
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Discussion |
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In this study we measured gas concentrations in both cuff and pilot balloon, separately. Nitrous oxide concentration in the cuff increased during anaesthesia and became greater than 40% after 4 h. This value is similar to the equilibrating concentration in standard tracheal tubes in our previous study (4050%).3 In contrast, nitrous oxide concentration in the pilot balloon was only 2% in the present study. This large concentration gradient between the cuff and pilot balloon might be a result of a narrow connecting tube and slow transfer between the cuff and pilot balloon. Consequently, nitrous oxide concentration in the cuff approached the equilibrating concentration, which would limit nitrous oxide diffusion into the cuff.
Because the BrandtTM system consists of a cuff and balloon in series, total compliance of the system (0.34 ml (mm Hg)1) is approximately equal to the sum of the compliance of the cuff (0.11 ml (min Hg)1) and compliance of the balloon (0.22 ml (mm Hg)1). The total compliance is 3.3 times greater than that of the cuff only. Because the compliance of the balloon is not affected by restricting the tracheal tube cuff, the ratio of total compliance to cuff compliance in a glass tube becomes much higher (8.2 times), which might contribute, in part, to the small changes in cuff pressure with nitrous oxide. The compliance of the BrandtTM tube cuff was 5.7 times higher than that of the Hi-ContourTM tracheal tube when assessed in a glass tube. Therefore, the compliant balloon of the BrandtTM system also appears to contribute to a stable-cuff pressure.
In this study, we assessed the volume change of each gas in the cuff and pilot balloon. The concentration of each gas changes because of the dilution effect from the increased amount of nitrous oxide. Although nitrogen and oxygen concentrations decreased significantly during anaesthesia, the volume changes were not significant (Fig. 2). On the other hand, carbon dioxide concentration in the cuff and pilot significantly balloon increased, and the volume increased significantly.
Tracheal cuff pressure should be maintained below 22 mm Hg and never exceed 37 mm Hg so that ischaemic mucosal damage can be avoided. We assessed the number of patients whose cuff pressure exceeded 22 mm Hg. By controlling cuff pressure, sore throat from tracheal intubation can be reduced by half.3 5 1215 Taken together, the BrandtTM tracheal tube is effective during anaesthesia with nitrous oxide, even with prolonged anaesthesia.
The BrandtTM system preserves stable-cuff pressure because of its highly compliant cuff/balloon rather than because an increase in the cuff volume is emitted. The nitrous oxide concentration gradient between the cuff and pilot balloon is probably another factor that restrains cuff pressure in the BrandtTM tracheal tube because high concentrations of nitrous oxide in the cuff will reduce nitrous oxide diffusion from the airway gases.
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Appendix |
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Vinjx(CaspCinj)/(CairCasp)
where Vinj is the volume (ml) of gas for inflating, and Cinj, Casp, or Cair denote gas concentration (i.e. nitrogen) of the injected or aspirated gases, or air, respectively.
The nitrogen concentration in the gas aspirated from the cuff and pilot balloon are shown in the Table 3. The estimated dead volume of the cuff was 0.2 (0.03) ml; that of the pilot balloon was 1.3 (0.1) ml.
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References |
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2 Al-Shaikh B, Jones M, Baldwin F. Evaluation of pressure changes in a new design tracheal tube cuff, the Portex Soft Seal, during nitrous oxide anaesthesia. Br J Anaesth 1999; 83: 80506
3 Karasawa F, Ohshima T, Takamatsu I, et al. The effect on intracuff pressure of various nitrous oxide concentrations used for inflating an endotracheal tube cuff. Anesth Analg 2000; 91: 70813
4 Kim JM. The tracheal tube cuff pressure stabilizer and its clinical evaluation. Anesth Analg 1980; 59: 29196[ISI][Medline]
5 Mandoe H, Nikolajsen L, Lintrup U, et al. Sore throat after endotracheal intubation. Anesth Analg 1992; 74: 897900[Abstract]
6 Payne KA, Miller DM. The Miller tracheal cuff pressure control valve. Anaesthesia 1993; 48: 32427[ISI][Medline]
7 Umezono Y, Fujita A, Toi T, Sakio H. Usefulness of tracheal tubes with N2O gas-barrier cuff. MASUI-Jpn J Anesthesiol 1999; 48: 125052
8 Karasawa F, Mori T, Okuda T, Satoh T. Profile Soft-Seal Cuff, a new endotracheal tube, effectively inhibits an increase in the cuff pressure through high compliance rather than low diffusion of nitrous oxide. Anesth Analg 2001; 92: 14044
9 Brandt L, Pokar H. The rediffusion system: limitation of nitrous oxide-induced increase of the pressure of endotracheal tube cuffs. Anaesthetist 1983; 32: 45964[ISI][Medline]
10 Fill DM, Dosch MP, Bruni MR. Rediffusion of nitrous oxide prevents increases in endotracheal tube cuff pressure. AANA J 1994; 62: 7781[Medline]
11 Seegobin RD, Hasselt GL. Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs. Br Med J 1984; 288: 96568[ISI][Medline]
12 Capan LM, Bruce DL, Patel KP, Turndorf H. Succinylcholine-induced postoperative sore throat. Anesthesiology 1983; 59: 2026[ISI][Medline]
13 Monroe M, Gravenstein N, Saga-Rumley S. Postoperative sore throat: effect of oropharyngeal airway in orotracheally intubated patients. Anesth Analg 1990; 70: 51226[Abstract]
14 Hakim ME. Beclomethasone prevents postoperative sore throat. Acta Anaesthesiol Scand 1993; 37: 25052[ISI][Medline]
15 Loeser EA, Kaminsky A, Diaz A, et al. The influence of endotracheal tube cuff design and cuff lubricant on postoperative sore throat. Anesthesiology 1983; 58: 37679[ISI][Medline]