Saline-filled cuffs help prevent laser-induced polyvinylchloride endotracheal tube fires

To determine whether the filling of tracheal tube cuffs with saline would decrease their combustibility during laser surgery, 20 polyvinylchloride tracheal tubes were studied. The cuffed end of each tracheal tube was inserted into the neck of an empty flask, and the tube and flask were flushed with oxygen for 5 min before cuff inflation. Ten tracheal tubes had their cuffs inflated with air, and 10 were inflated with saline. A Lasersonics LS880 CO2 laser, set to 5 W for five of each of the two types of filled cuffs and to 40 W for the other pair of five tubes, was fired continuously at the cuffs for up to 1 min. No combustion occurred at the 5-W setting. The times to cuff perforation when the laser was set at 5 W were (mean +/- SD) 1.00 +/- 0.83 and 4.21 +/- 3.91 s for the air- and saline-filled cuffs, respectively, a difference that was not statistically significant. The time to deflation of the saline-filled cuff (104.6 +/- 67.5 s) was, however, significantly longer than that of the air-filled cuff (2.59 +/- 1.97 s). When the tracheal tube cuffs were exposed to 40-W laser radiation, the cuff and adjacent tube shaft ignited in all cases when the cuffs were inflated with air, but only in one of five cases when the cuffs were filled with saline (P less than 0.05). The filling of tracheal tube cuffs with saline provides simple, moderately effective partial protection of the cuff of endotracheal tubes during CO2 laser airway surgery.     

In vitro diffusion of lidocaine across endotracheal tube cuffs

PURPOSE: Lidocaine diffuses across endotracheal tube cuffs, which may serve as a reservoir for local anesthetic to assist in the prevention of ETT-induced cough while emerging from general anesthesia. However, the rate of diffusion is slow. Two techniques, alkalization and warming, may increase the proportion of uncharged drug available for diffusion. The purpose of this study is to determine the effectiveness of warming alkalization or warming with alkalization on diffusion. METHODS: Four preparations of lidocaine 4% were studied. Group (Gr) L-lidocaine (24 degrees C), Gr WL--warmed lidocaine (38 degrees C), Gr AL--alkalized lidocaine (24 degrees C), Gr WAL--warmed, alkalized lidocaine (38 degrees C). Twenty-four Mallinckrodt 8.0 ID (Mallinckrodt Critical Care Division of Mallinckrodt, Inc., Glens Falls, New York) endotracheal tube cuffs were filled with 6 ml of one of the four preparations. They were then placed in a 20 ml water bath at 38 degrees C and samples were drawn from the water bath at intervals for up to 360 min. The lidocaine concentration in each sample was determined by gas chromatography. RESULTS: The highest lidocaine concentration was reached in Gr WAL (410.98 +/- 8.53 micrograms.ml-1) after 300 min and then decreased to 376.18 +/- 4.59 micrograms.ml-1 after 360 min. In Gr AL the highest concentration (235.05 +/- 2.99 micrograms.ml-1) was reached after 360 min. Lidocaine concentrations in Gr L and WL after 360 min were 3.19 +/- 1.16 micrograms.ml-1 and 4.32 +/- 2.02 micrograms.ml-1 respectively. CONCLUSION: Alkalization with or without warming, but not warming alone, promotes lidocaine diffusion from endotracheal tube cuff.     

Leakage of fluid around low-pressure tracheal tube cuffs

The aim of the study was to evaluate leakage of liquid past the low-pressure cuffs of tracheal tubes. Ten samples of each of nine different types of tubes were tested in a PVC mock trachea, using intracuff pressures of 20, 30, 40 and 50 cmH₂O. In five types of tubes, 6–10 cuffs allowed profuse leakage (> 20 ml water in 5 min) even at the highest intracuff pressure, i.e. 50 cmH₂O. In the most efficient tube, all the cuffs were leak-proof (leakage < 5 ml in 5 min) at 40 cmH₂O and in the second best type the cuffs were leak-proof at 50 cmH₂O. The leakage of fluid past the tracheal tube remains an unresolved problem with low-pressure cuffs.     

Aspiration beyond endotracheal cuffs

Large-volume low-pressure cuffs have been introduced in an endeavour to reduce the incidence of tracheal mucosal damage. These cuffs when inflated to clinical seal develop folds, which together with low clinical seal pressure may not protect against aspiration. This study compares the incidence of aspiration of dye past a variety of large-volume cuffed tubes and red rubber low-volume cuffs inflated to clinical seal in a group of 30 patients. The incidence of dye tracking past the large-volume cuffs studies was 100 per cent whereas no aspiration of dye was seen past the red rubber tubes. Increasing cuff pressure in the large-volume cuffs beyond clinical seal to 50 cm H₂O did not obliterate the dye-filled cuff folds, despite wide variation in the thickness of the cuff material.     

Prevention of silent aspiration due to leaks around cuffs of endotracheal tubes

Significant aspiration may occur around correctly inflated high volume, low pressure endotracheal tube cuffs. The prevention of silent aspiration due to leaks around cuffs of endotracheal tubes was investigated during general anesthesia for hip replacement in 47 patients. The patients were randomly assigned to one of three groups, in which one of three endotracheal tubes of different designs were used for intubation. The following three tubes were used: the red rubber Rüsch tube with low residual volume cuff, inflated to minimum occluding volume; the Mallinckrodt Hi-Lo tube with high residual volume cuff; the NL tube with high residual volume cuff and automatic cuff pressure regulation. The cuffs on the Mallinckrodt and the NL tubes were inflated to 29-31 cm H2O. One hour before termination of the surgical procedure, 1 ml methylene blue dye was injected into the trachea just above the cuff through a thin channel built into the tubes. At termination of the operation, the trachea below the cuff was inspected with a fiberoptic bronchoscope. Aspiration was found in 12.5% with the Rüsch tube, in 31.2% with the Mallinckrodt tube, and in 0% with the NL tube. Our results show that silent aspiration is still a problem with standard endotracheal tubes, but that it may be minimized by use of appropriate tubes, cuffs, and control of cuff inflation.     

Tracheal pathology following short-term intubation with low- and high-pressure endotracheal tube cuffs

Histologic sections of dog tracheas were taken from 20 dogs anesthetized and intubated for 5 to 7 hours with high-pressure, low-volume Shiley or low-pressure, high-volume Lanz endo-tracheal tubes. Microscopic examination and measurement showed that while the high-pressure, low-volume cuff produced deeper average mucosal erosion, the large-volume, low-pressure cuff resulted in significantly greater lengths of tracheal mucosa-cuff erosion. Maximal depth of penetration throught the basement membrane was similar in both groups. Grooves in the mucosa were seen in 50% of the high-volume-cuff trachea sections but none of the low-volume-cuff tracheal sections. These findings demonstrate that low-pressure, high-volume endotracheal tube cuffs produce different but significant tracheal damage after short-term intubation when compared to high-pressure, low-volume cuffs.     

A management option for leaking endotracheal tube cuffs: use of lidocaine jelly

STUDY OBJECTIVE: To evaluate the effectiveness of methods for sealing a small endotracheal tube cuff perforation. DESIGN: Randomized evaluation in an in vitro model of mechanical ventilation. In addition, two pertinent cases are reported. SETTING: Operative anesthesia service in a large tertiary referral center. INTERVENTIONS: A transparent acrylic "trachea" attached to a rubber breathing bag ("lung") was intubated with an 8.0 mm endotracheal tube. Positive pressure mechanical ventilation was begun and baseline minute ventilation recorded. After equilibrium, the endotracheal tube cuff was perforated in a standard fashion, and one of four "treatments" was applied in random sequence. Group A endotracheal tubes (n = 7) were managed by increasing fresh gas flow and manually injecting air into the cuff. Group B cuffs (n = 8) were insufflated with oxygen to maintain cuff pressure at 25 to 28 mmHg. In Groups C (n = 8) and D (n = 9), an 8 ml mixture of 2% lidocaine hydrochloride jelly (Xylocaine, Astra, Westborough, MA), and saline was injected into the cuff at a dilution of 1:3 and 1:1, respectively. MEASUREMENTS AND MAIN RESULTS: Measurements included minute ventilation, airway pressure, and intracuff pressure. During the 30-minute observation period after cuff perforation, total exhaled ventilation was assessed and wasted ventilation calculated. Group A wasted ventilation (means +/- SD) was significantly greater (112 +/- 20 liters, p less than 0.01) than Groups B, C, and D (12 +/- 12 liters, 10 +/- 5 liters, and 18 +/- 13 liters, respectively). In Group A, it was impossible to maintain adequate minute ventilation. To remain inflated, Group B cuffs required insufflation at a rate of 10 to 80 ml/min. Groups C and D maintained an excellent cuff seal, but 2 of 9 Group D cuffs could not be deflated, while all Group C cuffs were deflatable. Also reported are two cases of persistent intraoperative endotracheal tube cuff leaks refractory to conventional management. Inflation of the endotracheal tube cuff with a lidocaine jelly-saline mixture successfully eliminated the leak, allowing completion of the procedure without reintubation. CONCLUSIONS: The authors' in vitro results, in conjunction with the observations from their two cases, suggest that lidocaine jelly mixed with 1 to 3 parts normal saline may be useful in managing certain types of endotracheal tube cuff incompetence.     

Preventive measure against nitrous oxide induced volume and pressure changes of endotracheal tube cuffs

Endotracheal tube (ETT) cuff volume and pressure changes were studied in patients receiving 70% and 50% nitrous oxide for anaesthesia. ETT cuffs were inflated with either room air or inhalation mixture. There was a significant increase in cuff volumes and pressures in ETT cuffs containing room air compared to insignificant changes in cuffs containing the inhalation mixture during a two hour study period. A simple measure of substitution of air by the inspired anaesthetic gases for ETT cuff inflation is highly beneficial in the prevention of detrimental changes due to excessive increase in cuff volumes and pressure during nitrous oxide administration.     

Technical communication: design and in vitro testing of a pressure-sensing syringe for endotracheal tube cuffs

Endotracheal intubation is a frequently performed procedure in the prehospital setting, intensive care unit, and for patients undergoing surgery. The endotracheal tube cuff must be inflated to a pressure that prevents air leaks without compromising tracheal mucosal blood flow. For simultaneous endotracheal tube cuff inflation and measurement, we designed and tested a novel pressure-sensing syringe in vitro. The prototype was developed using a standard 10-mL polycarbonate syringe body that houses a plunger and a silicone rubber bellows, the pressure-sensing element. Bellow feasibility was determined and modeled using finite element analysis. Repeatability testing at each pressure measurement for each bellows (pressure versus deflection) was within an average standard deviation of 0.3 cm to 1.61 cm (1%-5% error). Using an aneroid manometer for comparison, there was excellent linear correlation with a Spearman rank of 0.99 (P < 0.001), up to 30 cm H(2)O.     

Nitrous oxide diffusion into tracheal tube cuffs: comparison of five different tracheal tube cuffs

BACKGROUND: The aim of this study was to investigate cuff compliance and cuff pressure during nitrous oxide exposure in the recently introduced Microcuff tracheal tube with a polyurethane cuff (Microcuff GmbH, Weinheim, Germany), and to compare it to conventional tracheal tubes with PVC cuffs. METHODS: In an in vitro set up, five cuffed tracheal tubes (ID 7.0 mm) from different manufacturers (Microcuff HVLP, Portex Profile Soft Seal, Mallinckrodt HiLo, Rüsch Super Safety Clear and Sheridan CF) were studied. Pressure-volume curves were assessed and changes of cuff pressure during exposure to nitrous oxide (for 60 min; 66% N(2)O in oxygen) were recorded without and with restriction of the cuff in a trachea model. Each experiment was performed four times using two exemplars of each tube twice. Sixty-minute values of the Microcuff group were compared with the other groups using the Mann- Whitney test (P < 0.05). RESULTS: The Microcuff polyurethane cuff demonstrated an intermediate cuff compliance but the highest cuff pressure increase during nitrous oxide exposure under unrestricted conditions. When inflated within the artificial trachea its cuff compliance became the highest of all tested tracheal tubes. However, exposure to N(2)O, again led to a rapid increase in cuff pressure. CONCLUSION: The ultra-thin polyurethane tube cuff demonstrated higher permeability for nitrous oxide than conventional PVC cuffs and led to a rapid cuff pressure increase when exposed to N(2)O. Routinely checking of cuff-pressure or filling the cuff with nitrous oxide are more important than the brand of tube used.