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.     

Tracheal Mucus Velocity Remains Normal in Healthy Sheep Intubated with a New Endotracheal Tube with a Novel Laryngeal Seal

Background: Tracheal mucus velocity (TMV), an index of mucociliary clearance, is reduced markedly in patients intubated with standard endotracheal tubes (ETTs) with high-compliance low-pressure (hi-lo) cuffs. The authors developed a new ultra-thin walled ETT in which the inflatable cuff is replaced with a no-pressure seal, positioned at the level of the larynx. The seal consists of 12 to 20 toroidal layers of thin polyurethane film ("gills") at the level of the vocal cords and prevents both air leak and fluid aspiration. The authors hypothesized that ETTs with the new laryngeal seal may impair TMV less than ETTs with inflated hi-lo cuffs do.

Methods: The TMV was measured in seven healthy female sheep by radiographically tracking the motion of small discs of tantalum inserted into the trachea through a bronchoscope. The TMV was measured in spontaneously breathing sheep before intubation (baseline) and after intubation with either a hi-lo ETT (control group) or after intubation with a new ETT with gills (study group). Four to six weeks later, the studies were repeated, but the sheep that were previously in the control group served as the study group, and those in the study group served as controls.

Results: Baseline TMV did not differ in the two groups. In the control group, TMV decreased significantly (by 67%) from baseline. In the study group, TMV did not differ significantly from baseline and remained steady during 3 h of intubation.     

Flammability of endotracheal tubes in oxygen and nitrous oxide enriched atmosphere

Endotracheal tube (ETT) fire has been reported secondary to laser and electrocautery ignition. The flammability of polyvinylchloride (PVC), silicone (Si), and red rubber (RR) ETTs in oxygen (O2) and/or nitrous oxide (N2O) in nitrogen was determined and compared by means of the O2 and N2O indices of flammability. The O2 index of flammability is the minimum O2 fraction in nitrogen that will support candle-like flame using a standard ignition source. The O2 index of flammability for PVC ETTs is 0.263, for Si 0.189, and for RR 0.176. The N2O index of flammability is the minimum N2O fraction in N2 that will support candle-like flame using a standard ignition source. The N2O index of flammability for PVC ETTs is 0.456, for Si ETTs 0.414, and for RR ETTs 0.374. The indices are additive. Flammability is a valid method of comparing safety of various endotracheal tube materials. There is a need for new endotracheal tube material with a higher index of flammability. The significance of these findings and the clinical applications are discussed.     

Predictors of postoperative sore throat in intubated children

Background: The incidence of postoperative sore throat (POST) following intubation is not well defined in the pediatric population. The etiology is multifactorial and includes impairment of subglottic mucosal perfusion and edema as a result of the pressures exerted by cuffed or uncuffed tubes. Aim: To determine the incidence of, and risk factors for, POST in intubated children undergoing elective day‐case surgery. Methods: Five hundred patients aged 3–16 years were studied prospectively. Endotracheal tube (ETT) choice (cuffed or uncuffed) was left to the anesthetist. The cuff was inflated either until loss of audible leak or to a determined pressure using a cuff manometer. The research team then measured the cuff pressure (CP). POST incidence and intensity was determined by interviewing patients prior to discharge from the same day procedure unit. Chi‐square testing and stepwise logistic regression were used to determine the predictors of POST. Results: Of the 111 (22%) children developed a sore throat, 19 (3.8%) a sore neck, and 5 (1%) a sore jaw. 19% of patients with cuffed ETTs complained of sore throat compared with 37% of those intubated with an uncuffed ETT. The incidence of POST increased with CP; 0–10% at 0 cmH₂O, 4% at 11–20 cmH₂O, 20% at 21–30 cmH₂O, 68% at CP 31–40 cmH₂O, and 96% at CP >40 cmH₂O. The ETT CP and use of uncuffed ETTs were univariate predictors of POST. Conclusions: Children intubated with uncuffed ETTs are more likely to have POST. ETT CP is positively correlated with the incidence of POST. When using cuffed ETTs, CP should be routinely measured intraoperatively.     

Value of endotracheal tube safety in laryngeal laser surgery

BACKGROUND AND OBJECTIVES: Due to the increased popularity of laryngeal laser therapy, surgeons and anesthesiologists are inevitably confronted with questions concerning the choice of the most efficient endotracheal tube (ETT) for laryngeal laser surgery, especially with regard to possible endolaryngeal tube fires, or combustions. The purpose of this study was to determine the current practice in endolaryngeal laser surgery in Germany. STUDY DESIGN/MATERIALS AND METHODS: A questionnaire was sent to 152 ENT Departments in Germany, care was taken that the responders could send back the questionnaire anonymously. Among other questions the participants were asked for the number of lasersurgical treatments of the larynx performed in the past, the usual type of ETTs in use, whether other safety precautions were taken during CO2 laser surgery of the larynx and for intraoperative complications like tube ignition, fires or combustions. RESULTS: Eighty six of the 152 addressed ENT departments replied. In laryngeal laser surgery, 59/86 departments regularly use special laser tubes in daily routine (74.5%). In about 20,000 lasersurgical procedures, 15 incidents of ETT fire have been reported. In six of the reported 15 cases a tube fire occurred despite the fact that special laser tubes had been utilized. CONCLUSIONS: The present study could demonstrate that the use of special laser tubes does not necessarily protect against ETT fire. Thus, even when using special laser tubes other safety measures should be taken. In view of the maximum safety for the patient it has to be stated, that the safety during surgery correlates definitely with the experience of the surgeon. The weakest point of ETTs is usually situated in the cuff region.     

Endotracheal tubes coated with antiseptics decrease bacterial colonization of the ventilator circuits, lungs, and endotracheal tube

BACKGROUND: Formation of a bacterial biofilm within the endotracheal tube (ETT) after tracheal intubation is rapid and represents a ready source of lung bacterial colonization. The authors investigated bacterial colonization of the ventilator circuit, the ETT, and the lungs when the ETT was coated with silver-sulfadiazine and chlorhexidine in polyurethane, using no bacterial/viral filter attached to the ETT. METHODS: Sixteen sheep were randomized into two groups. Eight sheep were intubated with a standard ETT (control group), and eight were intubated with a coated ETT (study group). Animals were mechanically ventilated for 24 h. At autopsy, the authors sampled the trachea, bronchi, lobar parenchyma, and ETT for quantitative bacterial cultures. Qualitative bacterial cultures were obtained from the filter, humidifier, inspiratory and expiratory lines, and water trap. ETTs were analyzed with light microscopy, scanning electron microscopy, and laser scanning confocal microscopy. RESULTS: In the control group, all eight ETTs were heavily colonized (10(5)-10(8) colony-forming units [cfu]/g), forming a thick biofilm. The ventilator circuit was always colonized. Pathogenic bacteria colonized the trachea and the lungs in five of eight sheep (up to 10(9) cfu/g). In the study group, seven of eight ETTs and their ventilator circuits showed no growth, with absence of a biofilm; one ETT and the respective ventilator circuit showed low bacterial growth (10(3)-10(4) cfu/g). The trachea was colonized in three sheep, although lungs and bronchi showed no bacterial growth, except for one bronchus in one sheep. CONCLUSIONS: Coated ETTs induced a nonsignificant reduction of the tracheal colonization, eliminated (seven of eight) or reduced (one of eight) bacterial colonization of the ETT and ventilator circuits, and prevented lung bacterial colonization.     

The effect of different lidocaine application methods on postoperative cough and sore throat

STUDY OBJECTIVE: To evaluate the efficacy of various ways of lidocaine application in reducing postoperative cough and sore throat. DESIGN: Double-blind, randomized study. SETTING: University-affiliated hospital. PATIENTS: 204 ASA physical status I and II patients scheduled for cataract surgery with general anesthesia. INTERVENTIONS: Patients were randomized to six groups (G1, G2, G3, G4, G5, and G6), according to lidocaine application method. Before endotracheal intubation, in the G1 and G2 groups, 10% lidocaine was sprayed on the distal end of the endotracheal tubes (ETTs; G1) and laryngopharyngeal structures (G2). In the G3 group, the distal ends of the ETTs were lubricated with 2% lidocaine jelly. Intravenous (IV) lidocaine was administered to the G4 group at the conclusion of surgery. Intracuff lidocaine was used in the G5 group; in the G6 group, the terminal end of the ETTs were lubricated with normal saline. MEASUREMENTS: At the end of surgery and after extubation, patients were observed to record the number of coughs. At 1 hour and at 24 hours following extubation, sore throat was evaluated. MAIN RESULTS: In the recovery room, 64.4% of the patients experienced cough, with greatest frequency in the G3, G6, and G2 groups, and the least in the G5 and G4 groups. The frequency of sore throat was significantly different among the six groups at 1 hour and at 24 hours, with greater frequency in the G3, G2, and G6 groups. CONCLUSIONS: Using lidocaine to inflate the ETT cuff or IV lidocaine at the end of surgery decreases the frequency of postoperative cough and sore throat and would provide better outcome for patients and the physician.     

The Self-inflating Bulb to Detect Esophageal Intubation during Emergency Airway Management

Background: The negative-pressure test using a self-inflating bulb (SIB) during emergency intubation was studied to determine its reliability and predictive value in this setting.

Methods: The endotracheal tube (ETT) position was tested in 300 consecutive patients undergoing in-hospital emergency endotracheal intubation. Immediately after intubation and before ETT cuff inflation, the following protocol was strictly followed: (1) an SIB was compressed, connected to the ETT, and released. A 10-s period was allowed for the bulb to inflate. (2) The ETT cuff was inflated, and the ETT position was confirmed using colorimetric or infrared carbon dioxide detection, or both, combined with clinical evaluation.

Results: There were 19 esophageal intubations (6% incidence). The SIB correctly identified all patients with esophageal intubation (sensitivity, 100%) and correctly identified all but three ETTs placed in the trachea (specificity, 99%). The three tracheally placed tubes that were misidentified by the bulb syringe occurred during one case each of chronic obstructive pulmonary disease, copious secretions, and obesity; of note were three tracheally placed tubes that were misidentified by the carbon dioxide analyzers during cardiopulmonary resuscitation.     

The future of the cuffed endotracheal tube

It has been traditionally taught that only uncuffed endotracheal tubes (ETTs) should be used for intubation in children younger than 8, or even 10, years old. However, recent literature suggests that the advantages of using uncuffed ETTs in children may be just another myth of paediatric anaesthesia. Using an uncuffed ETT does allow a tube of larger internal diameter to be used, minimizing resistance to airflow and the work of breathing in the patient who is breathing spontaneously. However, this advantage does not hold for ventilated patients, for whom ventilator settings can be adjusted to provide optimal airflow. Longer duration of intubation and a poorly fitted ETT are risk factors for mucosal damage, whether the ETT is cuffed or uncuffed. Furthermore, a properly sized, positioned, and inflated modern (low-pressure, high-volume) cuffed ETT can offer many advantages over an uncuffed ETT, including greater ease of intubation, better control of air leakage, lower rate and better control of flow of anaesthetic gases, and decreased risk of aspiration and infection.     

Use of cuffed endotracheal tubes in infants less than 5 kilograms: A retrospective cohort study

BackgroundImproved understanding of airway anatomy and refinement of equipment have led to the increased use of cuffed endotracheal tubes (ETTs) in infants and children. Despite expanded evidence on the potential advantages of cuffed ETTs in pediatric patients, there remains limited data on their use in infants less than 5 kilograms (kg). The current study retrospectively evaluates the perioperative use of cuffed ETTs in infants weighing 2–5 kg.MethodsThis is a retrospective study from a tertiary care children's hospital involving a 3-year period. Data regarding anesthetic care, airway management, and postoperative course were retrospectively retrieved from the electronic medical record.ResultsThe study cohort included 1162 patients, 1086 of whom had their tracheas intubated with a cuffed ETT and 76 with an uncuffed ETT. Patients were divided into two groups for analysis: 2 to <3 kg and 3 to 5 kg. In both weight groups, cuffed ETTs resulted in a decreased need for more than one laryngoscopy and a change in ETT size with no increase in postoperative airway effects including stridor.ConclusionsThese data provide additional information regarding the efficacy and safety of cuffed ETTs in neonates and infants.     

New Ultrathin-walled Endotracheal Tube with a Novel Laryngeal Seal Design: Long-term Evaluation in Sheep

Background: A new endotracheal tube (ETT) was fabricated and tested in sheep. It had no tracheal cuff; airway seal was achieved at the level of the glottis through a no-pressure seal made of "gills"; the laryngeal portion was oval-shaped; and the wall thickness was reduced to 0.2 mm.

Methods: Sheep were tracheally intubated either with a standard tube or with the new tube, and their lungs were mechanically ventilated for 1 or 3 days. Air leak was recorded at different peak inspiratory pressures (PIPs). Liquid seepage into the trachea was assessed using an indicator dye. Tracheolaryngeal lesions were scored grossly and histologically.

Results: There was no air leak up to 40 cmH2 O of PIP, in either group, in short- and long-term studies. Methylene blue leaked across the cuff in two sheep with standard ETTs. No dye leaked across the gills with the new ETTs. In the new ETT group, the trachea appeared better preserved, grossly and histologically, than in the standard ETT group at both 1 and 3 days (P < 0.05). At day 1, the larynx and vocal cords appeared grossly less injured in the new ETT group (P < 0.05), whereas there was no difference at day 3. Histology did not show significant difference on vocal cords, epiglottis, and larynx between the two groups at any time.     

Endotracheal Tubes Coated with Antiseptics Decrease Bacterial Colonization of the Ventilator Circuits, Lungs, and Endotracheal Tube

Background: Formation of a bacterial biofilm within the endotracheal tube (ETT) after tracheal intubation is rapid and represents a ready source of lung bacterial colonization. The authors investigated bacterial colonization of the ventilator circuit, the ETT, and the lungs when the ETT was coated with silver-sulfadiazine and chlorhexidine in polyurethane, using no bacterial/viral filter attached to the ETT.

Methods: Sixteen sheep were randomized into two groups. Eight sheep were intubated with a standard ETT (control group), and eight were intubated with a coated ETT (study group). Animals were mechanically ventilated for 24 h. At autopsy, the authors sampled the trachea, bronchi, lobar parenchyma, and ETT for quantitative bacterial cultures. Qualitative bacterial cultures were obtained from the filter, humidifier, inspiratory and expiratory lines, and water trap. ETTs were analyzed with light microscopy, scanning electron microscopy, and laser scanning confocal microscopy.

Results: In the control group, all eight ETTs were heavily colonized (105-108 colony-forming units [cfu]/g), forming a thick biofilm. The ventilator circuit was always colonized. Pathogenic bacteria colonized the trachea and the lungs in five of eight sheep (up to 109 cfu/g). In the study group, seven of eight ETTs and their ventilator circuits showed no growth, with absence of a biofilm; one ETT and the respective ventilator circuit showed low bacterial growth (103-104 cfu/g). The trachea was colonized in three sheep, although lungs and bronchi showed no bacterial growth, except for one bronchus in one sheep.     

Gamma irradiation and ethylene oxide in the sterilization of native reindeer bone morphogenetic protein extract.

BACKGROUND AND AIMS: For human use, it is necessary to sterilize bone morphogenetic proteins (BMPs), in order to reduce the risk of infections and associated complications. We compared the effects of ethylene oxide and gamma irradiation in the sterilization of native reindeer BMP extract with regard to bone induction in the Balb/C mouse thigh muscle pouch model. MATERIALS AND METHODS: BMP extract, sterilized with ethylene oxide gas (Steri-Vac 4XL, temperature 29 degrees C, exposure time 4 h, ethylene oxide concentration 860 mg/l), or gamma irradiation at doses of 3.15 MRad was administered in implants containing 5 or 10 mg of BMP extract with collagen carrier. Non-sterilized collagen implants served as controls. New bone formation was evaluated based on the incorporation of Ca45 and radiographically three weeks after implantation. RESULTS: The collagen was not able to induce new bone visible in radiographs. The mean Ca45 incorporation in the gamma sterilized group containing 5 mg of BMP extract was 30% (p = 0.04) and that containing 10 mg of BMP extract was 60% (p = 0.02) higher than seen in the corresponding ethylene oxide sterilized groups. The mean new bone areas were 45% higher in the gamma sterilized groups than in the corresponding ethylene oxide sterilized groups, but the differences were not significant. The mean optical density of new bone in the gamma sterilized group containing 5 mg of BMP extract was 75% (p = 0.00) and in that containing 10 mg of BMP extract was 70% (p = 0.00) higher than seen in the corresponding ethylene oxide sterilized groups. CONCLUSION: Native reindeer BMP extract is more sensitive to the effects of ethylene oxide gas sterilization than gamma irradiation. These results suggest that gamma irradiation is recommendable for the sterilization of BMP extracts.     

Alkalinization of intra-cuff lidocaine and use of gel lubrication protect against tracheal tube-induced emergence phenomena

Background. We sought to determine the benefits of using alkalinizedlidocaine 40 mg to fill the cuff of a tracheal tube (ETT) incombination with water-soluble gel lubrication to prevent post-intubationsore throat. Methods. The work included an in vitro study of the diffusionof alkalinized lidocaine solution through the low-pressure,high-volume cuff of an ETT. We also performed a randomized controlledstudy (n=20 patients in each group) that included a group whoreceived an alkalinized lidocaine-filled ETT cuff with lubricationof the tube using water-soluble gel (Group G), and two controlgroups who received an alkalinized lidocaine-filled cuff withETT lubrication with water (Group W) or an air-filled cuff withETT lubrication with water (Group C). Results. Water-soluble gel lubrication (Group G) produced alower incidence of sore throat during the 24-h post-extubationperiod than lubrication with water alone in the cuffs filledwith alkalinized lidocaine (Group W), and compared with theair control group. The ability of lidocaine to pass throughthe cuff of an ETT when water-soluble gel and/or water alonewas used as a lubricant was similar, as determined by lidocaineplasma concentrations (C_max 45 ng ml^–1). Cough andrestlessness before tracheal extubation were decreased in patientswith the alkalinized lidocaine-filled cuffs compared with theair-filled cuffs. After extubation, nausea, vomiting, dysphoniaand hoarseness were greater for patients with air-filled cuffscompared with the lidocaine-filled cuffs. No significant differencebetween the groups was recorded in arterial blood pressure andheart rate. In vitro data suggest that the lower the NaHCO₃injection volume, the greater the release of lidocaine acrossa low-pressure, high-volume cuff. Conclusions. These data show benefits of using an alkalinizedlidocaine-filled ETT cuff in combination with water-solublegel lubrication in preventing post-intubation sore throat. Br J Anaesth 2004; 92: 361–6     

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.     

Endotracheal intubation: the role of sterility

BACKGROUND: There is a paucity of data regarding whether sterile handling of endotracheal tubes (ETTs) impacts the incidence and prevalence of pneumonia in the emergency, urgent, or elective clinical scenarios. Intensive care units employ infection control and reduction schemes to reduce pneumonia rates. METHODS: A MEDLINE search of the English-language literature for the last 30 years was performed using the keywords "endotracheal intubation," "intubation," "pneumonia," "sinusitis," "tracheobronchitis," "nosocomial infection," and "infection." Data were limited to those papers addressing the role of sterile handling or passage of ETTs, infection with antibiotic-resistant micro-organisms, antibiotic prophylaxis, and the role of virulence determinants in supporting invasive infection. Also, a convenience sample of a single author's patients requiring tracheal intubation was undertaken. Data were acquired on tube handling, success of insertion, and subsequent occurrence of pneumonia. RESULTS: Virtually no data exist on the impact of sterile ETT handling, but unsterile manipulation of the ETT prior to insertion is common (112 of 154 intubation events). Within the limited patient sample, no conclusions may be drawn regarding the impact of unsterile handling on pneumonia rates, although sinusitis after nasotracheal intubation clearly increases the incidence of pneumonia. Biofilm generation as a facilitator of bacterial colonization of artificial airway surfaces is a ubiquitous virulence determinant that is not ameliorated by antibiotic administration. CONCLUSIONS: Unsterile ETT handling and insertion techniques are not clearly associated with pneumonia induction, but physiologically sound approaches that retard biofilm production may decrease pneumonia rates.     

Detection of oesophageal intubations using cuff pressures in a pig trachea oesophagus model

BACKGROUND: The cuff pressures may be different in oesophageal and tracheal intubations. We conducted a study to evaluate if cuff pressures of endotracheal tubes (ETTs) could provide information to distinguish tracheal or oesophageal intubations in a pig trachea-oesophagus model. METHODS: In each preparation of pig trachea-oesophagus model, the trachea and the oesophagus were intubated separately with a cuffed ETT, and the cuff pressures were measured after each 1 ml increment of air (1-10 ml) during inflation. The cuff pressures and the pressure-volume relationships in both intubations were compared. RESULTS: The cuff pressures of oesophageal intubations were significantly higher than those of tracheal intubations in all comparisons from 1 to 10 ml of cuff volumes (P < 0.05). The cuff pressure-volume curve was steeper in the oesophageal intubation group, and the difference between the two curves was the largest when the cuff volume was 4-5 ml. CONCLUSIONS: We conclude that the cuff pressures may be useful in detecting oesophageal intubations. This method is faster than other confirmation measures as it can detect inadvertent oesophageal intubations at the time of inflating the cuffs.     

Endotracheal tube cuff pressure. Monitoring during general anesthesia

BACKGROUND: To value changes of endotracheal tube cuff pressure during anaesthesia with N2O, using standard tubes or Brandt-system tubes. METHODS: Endotracheal cuff pressure during anaesthesia in three groups of patients has been monitored: Group 1 (n. 41): endotracheal tube with low-pressure cuff using N2O/O2 (2:1 or 1:1); Group 2 (n. 55): Brandt's double cuff-tubes using N2O/O2 (2:1 or 1:1); Group 3 (n. 20-control group): tubes with low-pressure cuff using O2/air. Values of pressure (M +/- DS: p < 0.05) have been compared with ANOVA, Bonferroni's method (p < 0.017). RESULTS AND CONCLUSIONS: Brandt's double cuff-tubes (G2) succeed in avoiding uncontrolled increase of cuff-pressure during anaesthesia with N2O. Standard low-pressure tubes (G1) shown increase of cuff pressure during anaesthesia with N2O which is absent using no N2O (G3).     

Laryngeal Resistance before and after Minor Surgery: Endotracheal Tube versus Laryngeal Mask Airway™

Background: The placement of an endotracheal tube (ETT) may promote laryngeal swelling, which is an important cause of upper airway obstruction after extubation. The authors hypothesized that laryngeal swelling after ETT placement increases laryngeal resistance and tested that hypothesis by comparing postoperative laryngeal patency between patients with ETT placement and those with a Laryngeal Mask Airway(TM) (LMA(TM)).

Methods: Fourteen adult patients who underwent elective minor surgeries were randomly allocated to two groups whose airway would be managed through ETTs (the ETT group) or LMAs(TM) (the LMA(TM) group) during the surgery. While maintaining at sevoflurane 1 minimum alveolar concentration, the authors measured laryngeal resistance before and after surgery, during both spontaneous breathing and mechanical ventilation under complete paralysis. In addition, they endoscopically measured the vocal cord angle under complete paralysis.

Results: In association with marked swelling of the vocal cords, the vocal cord angle significantly decreased after surgery in the ETT group, whereas the angle did not change in the LMA group. Laryngeal resistance during mechanical ventilation significantly increased only in the ETT group. Laryngeal resistance during spontaneous breathing significantly increased after surgeries in both groups.