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© 2001 International Anesthesia Research Society
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Abstract |
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We assessed the nitrous oxide (N2O) gas-barrier properties of a new endotracheal tube cuff, the Profile Soft-Seal Cuff (PSSC) (Sims Portex, Kent, UK). The tracheas of randomly selected patients were intubated with the Trachelon (Terumo, Tokyo, Japan), Profile Cuff (PC) (Sims Portex), or PSSC (n = 15 for each) endotracheal tube. Cuffs were inflated with air, and intracuff pressure was measured during anesthesia with 67% N2O. The concentration of N2O in cuffs was measured at the end of anesthesia. Postoperative sore throat was assessed. The volume-pressure relationship and thickness of the cuff were also measured. Cuff pressure, which increased gradually during anesthesia, was significantly less in the PSSC and PC groups than in the Trachelon group. The PSSC had smaller pressure than the PC 120 min after the start of anesthesia (P <0.05). There were no significant differences in the N2O concentration in cuffs among the groups, although the PSSC had the thinnest cuff with the highest compliance. The incidence of postoperative sore throat in the Trachelon group was significantly higher than in the other two groups. In summary, the PSSC effectively inhibits an increase in cuff pressure during anesthesia with N2O. The underlying mechanism is probably the higher compliance of the thinner cuff, rather than a reduction in N2O diffusion into the cuff.
Implications: A new material with nitrous oxide (N2O) gas barrier properties produces a thin and highly compliant cuff without increasing N2O diffusion, thereby reducing the increase of intracuff pressure and postoperative sore throat. Because the increase in the cuff pressure is time dependent, the Profile Soft-Seal Cuff (Sims Portex, Kent, UK) might be better than the Profile Cuff (Sims Portex) for anesthesia of a long duration.
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Introduction |
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During anesthesia, increases in cuff volume of an endotracheal tube because of diffusion of nitrous oxide (N2O) into the cuff are well documented (1,2). Cuff pressure should be maintained lower than the mean mucosal membrane capillary perfusion pressure (3), otherwise, sore throat is common in surgical patients after anesthesia with endotracheal intubation (2,4–6). The increase in intracuff pressure during anesthesia is dependent on both the volume of gases in the cuff and cuff compliance. Several devices (7–11) have been proposed to control intracuff pressure, and their efficacy has been reported. Some of them are designed to prevent N2O diffusion and/or to improve compliance. A new endotracheal tube with a cuff made of a material with high gas-barrier properties effectively prevents intracuff pressure increases during anesthesia with N2O (11), but this product is not available. Recently, another new endotracheal tube cuff, the Profile Soft-Seal CuffTM (PSSC; Sims Portex, Kent, UK), made of a material impervious to N2O, was developed and the efficacy has been reported (12,13). The N2O gas-barrier property and the cuff complication, however, have not yet been fully examined. Therefore, we designed a randomized study to examine changes in intracuff pressure and N2O concentration, and the volume-pressure relationships were measured to investigate the underlying mechanism and contribution toward reducing an increase in intracuff pressure.
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Methods |
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After obtaining institutional approval and patients’ informed consent, 45 male patients (24–72 yr of age, ASA physical status I or II) undergoing elective surgery were included in the study. Patients with a smoking habit or with symptoms of upper airway irritation were excluded from the study. Patients were randomly allocated to three groups: the trachea was intubated with the Trachelon (Terumo, Tokyo, Japan), the Profile Cuff (PC) (Sims Portex, Kent, UK), or the PSSC endotracheal tube (n = 15 for each). The Trachelon and PC endotracheal tubes were the standard tracheal tubes, and the PSSC endotracheal tube was made of a new material, velvet soft polyvinyl chloride, which reduces diffusion of N2O into the cuff during anesthesia by using N2O (Fig. 1).
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Premedication with hydroxyzine (50 mg) and atropine sulfate (0.5 mg) was administered IM 1 h preoperatively. After patients breathed 100% oxygen, anesthesia was induced with propofol (2–3 mg/kg). Vecuronium (0.1 mg/kg) was then administered to relax the muscles. The trachea was intubated with endotracheal tubes (8.0-mm inner diameter) by skilled anesthetists. Lubricant was not used. Immediately after intubation, the cuff was aspirated as much as possible and then inflated with the smallest volume of air that would not leak when the intraairway pressure was 18 cm H2O. The volume used to fill the cuff and the initial sealing pressure were recorded. Anesthesia was maintained with 67% N2O and 33% oxygen, supplemented with isoflurane or sevoflurane by using a recirculating breathing system. The lungs were ventilated mechanically, and the end-tidal CO2 was maintained within a physiologically normal range. The concentration of the inspired gas mixture was monitored by using a multiple-gas monitor (Capnomac UltimaTM; Datex, Helsinki, Finland). A humidifier was used, but use of a nasogastric tube was avoided. The neuromuscular blockade was reversed with neostigmine and atropine after completion of surgery.
By using a monitor (AS3; Datex), intracuff pressure was measured every 15 min by connecting the pilot balloon of the endotracheal tube to a pressure transducer (UK802; Baxter, Tokyo, Japan) through a three-way stopcock. If the mean intracuff pressure exceeded 40 mm Hg, gas in the cuff was aspirated to reduce the pressure <22 mm Hg and the aspirated volume was recorded, but the pressure data were discarded thereafter. At the end of anesthesia, the cuff was aspirated as much as possible. Approximately 15 min later, the volume of the aspirated gas was measured at room temperature with a calibrated syringe. In patients whose cuff pressure exceeded 40 mm Hg, summation of aspirated gas from cuffs was expressed as the volume aspirated. The N2O concentration was assayed with a multi-gas monitor (Type 1302; Bruel & Kjaer, Denmark). Each patient was interviewed postoperatively by an anesthetist unaware of the group to which the patient was assigned. The patient graded his postoperative sore throat as follows: 0 = none (no sore throat at any time after the operation), 1 = mild (scratchy throat), 2 = moderate (similar to that noted with a cold), and 3 = severe (more severe than with a cold).
Volume-pressure relationships were assessed with an in vitro study. The three types of endotracheal tubes (n = 6 for each) were inflated with air, 1 mL at a time, by using a syringe. The inflated volume and the intracuff pressure were recorded. In another measurement, the tracheal tube (n = 6 for each) was placed in a glass tube of 18.2-mm diameter (approximately the same cross-sectional diameter as an adult female trachea), and the cuff was inflated with air. The inflated volume and pressure in the cuff were measured. The thickness of the cuff (n = 6 for each) was also measured by using a micrometer (CD-15, Mitsutoyo, Japan).
Data are presented as number of patients or mean ± SD. Two-way analysis of variance for repeated measurements was used to assess changes over time within as well as between groups and one-way analysis of variance was performed to compare raw data between groups. Post hoc analysis to allow for multiple comparisons was performed by using a Bonferroni/Dunn correction. Student’s t-test was used to make single comparisons of cuff pressure and volume. For evaluation of verbal rating scores for sore throat, the Friedman test with RIDIT (relative to an identified distribution) analysis (14) allowing for multiple comparisons was performed. Proportional data were evaluated by using the 
2 test. A P value of <0.05 was considered statistically significant.
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Results |
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The three groups of patients were comparable in age, weight, height, and duration of anesthesia (Table 1). The mean cuff pressure of the Trachelon group significantly increased 15 min after the start of anesthesia (P < 0.0001, Figure 2) and continued to increase during anesthesia. Although the increase in the mean cuff pressure was not significant 15 min after anesthesia in the PC and PSSC groups (P = 0.052 and = 0.061, respectively), the increase of the intracuff pressure in both groups was significant after 30 min. There was a significant difference in the increase in cuff pressure among the three groups (P < 0.0001). The cuff pressure of the Trachelon group was significantly different from that in the other two groups during anesthesia (P < 0.01, Figure 2). The cuff pressure of the PSSC group was significantly smaller than in the PC group 120 min after the start of anesthesia (P < 0.05, Figure 2).
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During the course of anesthesia, there were eight patients in the PSSC group whose cuff pressure exceeded 22 mm Hg, which was significantly smaller than in the Trachelon or PC groups (P < 0.01 and 0.05, respectively, Table 2). Cuff pressure exceeded 40 mm Hg in 13 patients in the Trachelon group, which was significantly different from that in the PC or PSSC groups (P < 0.01 or 0.0001, respectively, Table 2). In the Trachelon group, cuff pressure exceeded 40 mm Hg twice in five patients. Although the initial sealing pressure was not significantly different, the inflated volume was significantly different among the three groups (P = 0.0003), with that of the Trachelon group significantly smaller than those of the other two groups (P < 0.01 for each, Table 2). The volume of aspirated gases from the cuffs increased significantly (P < 0.0001 for each, Table 2) and the N2O concentration in the gases aspirated from cuffs at the end of anesthesia was approximately 30% in all groups. There was no significant difference, however, in the increase in the volume or the N2O concentration among the groups.
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The incidence of sore throat on postoperative Day 1 was significantly different among the three groups (P = 0.002, Table 3). The PC and PSSC groups were significantly different from the Trachelon group (P < 0.05 for each, by a RIDIT analysis). The patients with a sore throat improved with each passing day. The incidence of sore throat on postoperative Days 2 or 3 was not significantly different among the three groups.
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The volume-pressure relationships of the three types of tubes are shown in Figure 3. There was a significant difference among the three groups (P < 0.0001). The Trachelon had the hardest cuff and the PSSC had the softest cuff of the three groups. The volume-pressure relationships of the three types of tubes shifted leftward (Figure 4) when the endotracheal tube was placed in a glass tube. There was a significant difference among the three groups (P = 0.0004, Figure 4). Furthermore, there was a small but significant difference between the PC and the PSSC groups (P < 0.05). The thickness of the tracheal cuff was significantly different among the three groups (P = 0.0001). The Trachelon (0.09 ± 0.005 mm) had a thinner cuff than the PC (0.11 ± 0.005 mm, P < 0.0001), and the PSSC (0.06 ± 0.005 mm) had the thinnest cuff of the three groups (P < 0.0001 for each).
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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Compared with the Trachelon group, which is one of the normal endotracheal tubes, the PC and PSSC groups had a smaller increase in the cuff pressure during N2O anesthesia (Figure 2 and Table 2), resulting in a decreased severity of postoperative sore throat (Table 3). Although the intracuff pressure in both the PSSC and PC groups gradually increased during anesthesia, the cuff pressure of the PSSC was smaller than that of the PC. Our results are consistent with those of Umezono et al. (12), who reported that PC and PSSC are effective in controlling the increase in cuff pressure, and that the pressure of the PSSC is slightly smaller than that of the PC from 60 to 120 min after the start of anesthesia. Al-Shaikh et al. (13) also reported that PSSC prevents an increase in intracuff pressure 60 min after the start of anesthesia.
We measured volume and N2O concentration of gases aspirated from the cuff at the end of anesthesia. There are few investigations of N2O gas barrier cuffs, however, in which N2O assay was performed. In the present study, the N2O concentration increased considerably in the three groups during N2O anesthesia but the values were not significantly different among the groups (Table 2), suggesting that N2O gas-barrier properties of the PSSC might not be sufficient to inhibit an increase in N2O concentration in the cuff. Generally, volume of gases in cuffs and cuff compliance are important factors because changes in intracuff pressure are dependent on both. Our results clearly indicated that the PSSC, the tube with the thinnest cuff, had the highest compliance but did not affect changes in volume and N2O concentration of the intracuff gases. This property of PSSC rather than N2O gas-barrier property per se is probably the underlying mechanism of controlling the intracuff pressure during anesthesia with N2O.
The rate of pressure increase is inversely proportional to cuff thickness (15), suggesting that the diffusion rate of N2O is also inversely proportional to cuff thickness. Therefore, the cuff material of the PSSC is considered to possess an N2O gas-barrier property because the PSSC had the thinnest cuff in the present study. Furthermore, the N2O gas-barrier property might contribute to making thinner cuffs without increasing N2O diffusion. The thin PSSC cuff probably contributes to its having the highest cuff compliance of the three endotracheal tubes. Although the PSSC had an extremely high cuff compliance compared with the PC in an in vitro study (Figure 3), the volume-pressure relationship shifted leftward (Figure 4) when the tracheal tube was placed in glass tubes with diameters approximately the same as the cross-sectional diameter of an adult female trachea, resulting in a smaller difference of the relationships between the PC and the PSSC. This might be the reason why the intracuff pressure of the PSSC, the tube with the highest cuff compliance, was only slightly smaller than that of the PC during anesthesia.
The incidence of postoperative sore throat in this study is consistent with previous reports of 35% to 60% in surgical patients (2,4–6,16,17) anesthetized with endotracheal intubation. The PSSC and PC, designed with properties to inhibit an increase in cuff pressure, decreased the severity of postoperative sore throat. However, we assessed the number of patients whose cuff pressure exceeded 22 mm Hg during anesthesia, which is the mean mucosal capillary perfusion pressure of the trachea (2). Although the number of patients whose cuff pressure exceeded 22 mm Hg in the PSSC group (8 of 15) was significantly smaller than in the PC group (14 of 15), there was no significant difference in the severity of sore throat between the two groups. The reason for this discrepancy is not clear. Generally, the severity of postoperative sore throat is dependent on both pressure against the tracheal wall and the duration. Because the number of patients whose cuff pressure exceeded 40 mm Hg in the Trachelon group (13 of 15) was significantly higher than in the PC (4 of 15) or PSSC groups (1 of 15), much higher cuff pressure (i.e., higher than 40 mm Hg) might be necessary to injure the tracheal mucosal membrane. Further study is needed to determine the critical cuff pressure required to injure tracheal mucosal membrane.
In conclusion, our data indicate that the PSSC, a new tracheal tube with N2O gas-barrier properties, inhibits the increase in intracuff pressure during N2O anesthesia, which reduces the severity of postoperative sore throat. Because an increase in the volume of cuff gases and in N2O concentration is not inhibited in PSSC, however, it is suggested that the high compliance of the cuff, rather than the N2O gas-barrier properties of PSSC, is the main mechanism underlying the inhibition of an increase in the cuff pressure.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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- Stanley TH, Kawamura R, Graves C. Effects of nitrous oxide on volume and pressure of endotracheal tube cuffs. Anesthesiology 1974; 41: 256–62.[Web of Science][Medline]
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Karasawa F, Ohshima T, Ehata T, et al. The effect on intracuff pressure of various nitrous oxide concentrations used for inflating an endotracheal tube cuff. Anesth Analg 2000; 91: 708–13.
[Abstract/Free Full Text] - Seegobin RD, Hasselt GL. Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs. BMJ 1984; 288: 965–8.
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Mandfe H, Nikolajsen L, Lintrup U, et al. Sore throat after endotracheal intubation. Anesth Analg 1992; 74: 897–900.
[Abstract/Free Full Text] -
Monroe M, Gravenstein N, Saga-Rumley S. Postoperative sore throat: effect of oropharyngeal airway in orotracheally intubated patients. Anesth Analg 1990; 70: 512–26.
[Abstract/Free Full Text] - Stout DM, Bishop MJ, Dwersteg JF, Cullen BF. Correlation of endotracheal tube size with sore throat and hoarseness following general anesthesia. Anesthesiology 1987; 67: 419–21.[Web of Science][Medline]
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Kim JM. The tracheal tube cuff pressure stabilizer and its clinical evaluation. Anesth Analg 1980; 59: 291–6.
[Free Full Text] - Payne KA, Miller DM. The Miller tracheal cuff pressure control valve. Anaesthesia 1993; 48: 324–7.[Medline]
- Brandt L Pokar H. The rediffusion system: limitation of nitrous oxide-induced increase of the pressure of endotracheal tube cuffs. Anaesthesist 1983; 32: 459–64.[Medline]
- Fill DM, Dosch MP, Bruni MR. Rediffusion of nitrous oxide prevents increases in endotracheal tube cuff pressure. AANA J 1994; 62: 77–81.[Medline]
- Fujikawa M, Mizoguchi H, Kawamura J, et al. A new endotracheal tube with a cuff impervious to nitrous oxide: constancy of cuff pressure and volume. Anesth Analg 1995; 81: 1084–6.[Medline]
- Umezono Y, Fujita A, Toi T, Sakio H. Usefulness of tracheal tubes with N2O gas-barrier cuff. Masui 1999; 48: 1250–2.[Medline]
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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: 805–6.
[Abstract/Free Full Text] - Bross IDJ. How to use ridit analysis. Biometrics 1958; 14: 18–38.
- Chandler M. Pressure changes in tracheal cuffs. Anaesthesia 1986; 41: 287–93.[Medline]
- Hakim ME. Beclomethasone prevents postoperative sore throat. Acta Anaesth Scand 1993; 37: 250–2.[Web of Science][Medline]
- Capan LM, Bruce DL, Patel KP, Turndorf H. Succinylcholine-induced postoperative sore throat. Anesthesiology 1983; 59: 202–6.[Web of Science][Medline]
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