Balloon Cuff Research Articles

Evaluating the Effects of a 532‐nm Fiber‐Based KTP Laser on Transoral Laser Surgery Supplies

The KTP laser has become commonplace in transoral head and neck surgery. The interactions of this laser with commonly used supplies in transoral surgery have not been formally examined. This study evaluates the effects of the KTP laser on surgical supplies. Experimental study. The study was conducted in an empty operating room at a university-affiliated medical center. An Aura XP 532-nm KTP laser with a 600-nm fiber was used in pulsed and continuous modes. The beam was focused at the shaft and balloon of 3 "laser-safe" endotracheal tubes (ETTs), a polyvinyl chloride (PVC) ETT, and a Codman surgical patty. Time to penetrate was recorded. Results The KTP laser beam was unable to penetrate any of the laser-resistant ETTs. It did react with the black number markings on the PVC ETT by producing sparks but was unable to penetrate the shaft of the ETT. The KTP laser was nonreactive with all ETT cuffs except in 1 of 3 trials with the outer balloon cuff of a Rusch Lasertubus ETT when the laser was used in a continuous mode. The KTP laser caused the production of a flame upon contact with the blue radiopaque strip of the surgical patty, even when the patty was wet. This study demonstrates that a number of safe ETT options may be used during transoral laser microsurgery with a KTP laser. In addition, Codman surgical patties are shown to be a significant fire risk in KTP laser surgery.

Effects of a KTP Laser on Commonly Used Endotracheal Tubes in Head and Neck Surgery

Objectives: The effects of modern KTP lasers on endotracheal tubes (ETTs) have not been formally examined. In this study we investigated the interaction of the Aura XP 532 nm KTP and commonly used ETTs. Methods: An Aura XP 532 nm KTP laser with a 600 nm fiber was used in pulsed and continuous modes. The laser beam was focused at a distance of 0.5 cm from the shaft and balloon of three laser safe ETTs and a standard polyvinylcholoride (PVC) ETT. Time to penetrate through the ETT and cuff was recorded in seconds (s). Results: The KTP laser did not penetrate any of the laser resistant ETTs or standard PVC ETTs within 90s of contact in either mode. The beam did react with the black markings on the PVC ETT by producing smoke. The KTP laser was nonreactive with all cuffs except in one of three trials with the outer balloon cuff of a Rusch Lasertubus ETT in continuous mode. Conclusions: This is the first report documenting the effects of a KTP laser on ETTs. The bodies of all ETTs were found to be resistant to the KTP laser, while only the black markings on the shaft of a PVC ETT reacted with the laser beam. This study demonstrates that there are a number of options that may be used safely during transoral laser microsurgery with a KTP laser.

Safety Concerns of the CO2 Laser in Traditional and Hand‐Held Modes in Transoral Laser Microsurgery

Objectives:Comparisons between line‐of‐sight and fiber‐optic carbon dioxide (CO2) lasers have not been previously reported in regards to interactions with commonly used products in transoral laser microsurgery. In this study we sought to address this gap.Methods:The beams of a traditional and an Omniguide fiber‐based laser were focused on commonly used materials in transoral laser microsurgery. Three laser resistant endotracheal tubes (ETTs), a standard polyvinylcholoride (PVC) ETT, and cottonoids were evaluated. The time to penetrate through the material was recorded.Results:Neither laser beam completely penetrated any of the laser resistant ETTs within 90s of contact. However, both instantaneously perforated the absorbent coating of the laser resistant tubes, immediately exposing the underlying metal tape. The traditional laser perforated the PVC endotracheal tube at 0s, and the Omniguide laser did so within 3s. The Rusch Lasertubus ETT balloon cuff was the most resistant material to both lasers. Both laser beams perforated dry cottonoids instantaneously but were unable to penetrate excessively saturated cottonoids.Conclusions:In general the time to penetrate materials was longer for a traditional CO2 laser when used at the same power. The absorbent outer coating of all ETTs was easily penetrated with the laser, revealing highly reflective metallic tape. While supersaturated cottonoids were resistant to both lasers, dry pledgets could be penetrated. Of all ETTs tested, the Rusch Lasertubus ETT appears to be the most resistant to both lasers.

Predicting laryngeal edema in intubated patients by portable intensive care unit ultrasound

PurposeThe purpose of this study is to determine the diagnostic accuracy of portable ultrasound for detection of laryngeal edema (LE) in intubated patients. Materials and MethodsWe conducted a prospective, observational study from December 2010 to September 2011. We measured air column width differences (ACWD) in planned extubation patients admitted in intensive care unit by ultrasound. The primary outcome was the diagnostic accuracy of ACWD to predict the presence of LE. ResultsA total of 101 patients were enrolled. The prevalence of LE was 16.8%. Baseline characteristics were similar between intubated patients with and without LE. The mean difference of increasing of air column width in patients without LE was higher than in LE group (1.9 vs 1.08 mm, P < .001). The sensitivity and specificity at ACWD higher or equal to 1.6 mm were 0.706 and 0.702, respectively. The positive predictive value and negative predictive value were 0.324 and 0.922, respectively. The area under the receiver operating characteristic curve of laryngeal ultrasound was 0.823 (95% confidence interval, 0.698-0.947) and that of cuff leak test was 0.840 (95% confidence interval, 0.715-0.964). ConclusionPortable intensive care unit ultrasound visualizing ACWD between predeflation and postdeflation cuff balloon is a promising objective tool, which aids in prediction of successful extubation regarding LE.

Study of contrast enhanced ultrasound on muscle crush injury to extremity

Objective To explore imaging feature of muscle crush injury of extremity on contrast enhanced ultrasound (CEUS) by an animal experiment.Methods Twenty-eight New Zealand rabbits were anesthetized by intramuscular pentobarbital sodium (30 mg/kg).A special balloon cuff device was used to create left hind leg crush injury with a force of (18.6 kPa).23 of the 28 rabbits had crush injury of extremity and survived for 72 hours.CEUS evaluated infusion model and contrast intensity in crush region of hind leg at the 0.5,2,6,24 and 72 hour after the release of the crushing pressure.Peak intensity (PI) was analyzed by comparing with serum creatinekinase (CK) and myoglobin (MYO).Results Twenty-three rabbits presented that the area of crushed region in left hind leg was 60 cm2,accounting for 2.6％-3.0％ of body surface area.In different time after decompression,the crushed regions showed rapid enhancement and the intensity was higher than that of no-crushed region.The time-intensity curves of crushed regions all appeared as fast wash-in and slow wash-out.PIs of rushed regions were higher obviously than those of nocrushed regions (P ＜0.001).ROC curves were employed in diagnosis value of PI for crushed region.And PIs showed positive correlation with CK and MYO and the correlation coefficient was 0.833-0.996.Conclusions CEUS presents that the micro-circulation perfusion of the crushed muscle increased obviously after the release of the crush pressure.PIs evaluated quantitatively the micro-circulation perfusion changes.It suggests a potential alternative for evaluating micro-circulation abnormality and ischemia reperfusion injury of the muscle crush injury to extremities. Key words: Ultrasonography ; Microbubble ; Extremities; Crush injury

Contrast-enhanced ultrasound assessment of muscle blood perfusion of extremities that underwent crush injury

This research aimed to study the assessment of local muscle microcirculation perfusion of extremities that underwent crush injuries by using contrast-enhanced ultrasonography (CEUS). A total of 28 New Zealand rabbits were anesthetized by using intramuscular pentobarbital sodium (30 mg/kg). A balloon cuff device was used to create crush injuries to the left hind leg of each rabbit with a force of 18.6 kPa. CEUS was performed at the 0.5th, 2nd, 6th,24th, and 72nd hour after the release of the crush pressure. Peak intensity (PI) of the crushed regions was compared with those of the uncrushed regions and before the creation of crush injury. Receiver operating characteristic analysis was used to determine the diagnostic value of PI for the crushed region. During the 72nd hour after the release of the crush pressure, 5 of the 28 rabbits died, and thus, their statistics were eliminated from the experiment. At different time points after the release of the crush pressure, the crushed regions in all 23 survivals showed quick and high enhancement, and their intensities were higher than those of the un crushed region in the arterial phase. The time-intensity curves of the crushed regions all appeared as rapid lift-gradual drop. PIs were obviously higher in the crushed regions than in the uncrushed regions and than those before the creation of crush injury ( p G 0.001). Receiver operating characteristic curves showed that extremity crush injury was diagnosed by using PI value. CEUS presents that the microcirculation perfusion of the crushed muscle increased obviously after the release of the crush pressure.PIs evaluated quantitatively the microcirculation perfusion changes. It may suggest a potential alternative for evaluating microcirculation abnormality of the muscle crush injury to the extremities.

Tracheoesophageal Fistula: A Fatal Complication of Endotracheal Intubation

Tracheoesophageal fistula (TEF) is a rare disease which develops as a result of congenital or acquired causes. We report on two TEF female stroke patients with associated endotracheal intubation. Endotracheal intubation was kept for 13-14 days because of decreased mentality by intracranial hemorrhage. Recurrent pneumonia was a predominant symptom. Computed tomography and bronchoscopy were used to diagnose TEF. Both patients expired by sepsis and recurrent pneumonia before definite TEF treatment. The excessive dilatation of the cuff balloon of the endotracheal tube was considered one of the main causes of TEF. Prevention is most important and early treatment is required in this fatal disease. (Korean J Neurotrauma 2013;9:146-149)

Muscle Crush Injury of Extremity: Quantitative Elastography with Supersonic Shear Imaging

The aim of this study was to determine the characteristic of muscle crush injury at quantitative ultrasonographic elastography using supersonic shear imaging (SSI). Twenty-three New Zealand rabbits underwent crush injury to left hind leg caused by a special balloon cuff device. Conventional ultrasonography and SSI quantitative elastography were performed at both crushed and uncrushed regions of the left hind legs. Quantitative lesion elasticity was measured using the Young’s modulus (in kilopascals) at 0.5 h, 2 h, 6 h, 24 h and 72 h after the release of the crushing pressure. Compared with those from the uncrushed regions, both the maximum and mean elasticity values at these time points from the crushed regions were significantly higher (p < 0.001). A receiver operating characteristic (ROC) analysis was employed to assess diagnostic performance. ROC curves showed that extremity crush injury was diagnosed using elasticity value and the greater the elasticity value, the greater the diagnostic value. SSI provides quantitative elasticity measurements, thus, adding complementary information that potentially could help in crush injury characterization with conventional ultrasonography.

Laparo-endoscopic Assisted Percutaneous Drainage Gastrostomy and Feeding Jejunostomy

Acquired tracheo-esophageal Fistula (TEF) is a rare but serious complication of prolonged endotracheal intubation. Patients of TEF are usually very critically ill and prone to repeated aspiration and pneumonia. The first stage of treatment involves the diversion of salivary and gastric contents away from the fistula site, improving the nutritional status and control of sepsis. A drainage gastrostomy and feeding jejunostomy is often required to divert the gastric contents away from the fistula and for nutrition. There are several methods of diversion of gastric contents and for creating feeding jejunostomy including percutaneous, endoscopic, radiological, laparoscopy and laparotomy, tailored according to the clinical situation and the available expertise. In this patient, percutaneous approach alone was not possible due to past and present abdominal surgery and obesity. A combined laparoscopic and endoscopic technique was used to create a drainage gastrostomy and feeding jejunostomy. TEF was repaired three months later. A 35 year old full term multipara female was referred from a neighboring country with a history of obstructed labor for the last three days. On examination, the patient was toxic, febrile, dyspnoic. Her abdomen was tense, tender, and had a scar from previous caesarian section and yet no fetal heart sounds were audible. The chest was full of bilateral crepitations. The initial diagnosis on admission was pre-eclampsia, intrauterine death of child, pneumonia and septicemia. An urgent U/S of the abdomen showed a full term uterus and no fetal movements. The chest X-ray and CT scan of the chest were suggestive of aspiration pneumonia. The patient was resuscitated. The dead fetus and placenta were delivered by emergency caesarian section. Her postoperative recovery was stormy. A tracheotomy was performed to assist in the ventilator. She was weaned from parental nutrition and was fed through the nasogastric tube. Four weeks after her tracheostomy, contents of nasogastric tube feeding were seen coming through the tracheotomy tube. A tracheo-esophageal fistula was suspected and confirmed by imaging studies and endoscopy. On Endoscopy the inflated cuff balloon of the tracheostomy tube was seen through the esophagus The TEF was of more than 2 cm in size, (Fig. 1). The case was discussed in a multidisciplinary meeting and in the view of extreme obesity with the history of past and recent surgery, percutaneous endoscopic gastrostomy (PEG) was considered unsafe.

Tracheal rupture after emergency endotracheal intubation

A 60-year-old woman presented to the emergency department (ED) of a suburban hospital with complaints of cough, fever, and dyspnea. She had a history of chronic obstructive pulmonary disease (COPD) and chronic steroid therapy. At presentation, she was in severe respiratory distress. Orotracheal intubation was decided due to persistence of severe hypoxia and hypercapnia with deterioration of consciousness despite a first attempt at noninvasive ventilation. The intubation was performed in rapid sequence using a 7.5-mm diameter single lumen tube without stylet. The patient had a regular and anatomically intact airway. The maneuver itself was reported to be an easy procedure and was considered successful after the first attempt. After about an hour of invasive ventilation, a subcutaneous emphysema appeared on the neck and anterior chest wall, respiratory failure worsened, and a slight hemoptysis occurred. The chest radiograph showed subcutaneous emphysema and protrusion of the cuff outside the tracheal lumen (Fig. 1). A computed tomography (CT) scan visualized the injury of the posterior tracheal wall due to the rupture of the pars membranacea (Fig. 2). The patient was then referred to our hospital to undergo a bronchoscopy, which revealed a longitudinal hole with sharp margins at the posterior part of the membranous portion, extending up to 2 cm from the carina with a total length of 5 cm. The lesion was surgically repaired via right thoracotomy. Fig. 1 a Chest radiograph in the anteroposterior view of the patient with tracheal rupture, showing subcutaneous and mediastinal emphysema. b Detailed view shows the protrusion of the cuff of the tube outside the tracheal lumen (white arrows) Fig. 2 a–c Corresponding CT axial scans corroborating the diagnosis of subcutaneous and mediastinal emphysema. d The lumen of the tracheal tube appears enlarged and deformed after the herniation of the cuff Mechanisms that may determine tracheal laceration are mechanical and anatomical [1]. An over-distended balloon cuff coupled with fragility of the tracheal wall due to chronic lung diseases and steroid therapy may be crucial [2]. The appearance of specific symptoms after intubation, like subcutaneous emphysema, hemoptysis, and persistence of hypoxia despite adequate ventilation, are consistent with a possible tracheal rupture [1–4]. Radiology may confirm the clinical suspicion.

A Servo-controlled Canine Model of Stable Severe Ischemic Left Ventricular Failure

Reversible left ventricular failure was produced in conscious dogs by compromise of the coronary circulation. In animals with prior left anterior descending coronary artery occlusion, mean left atrial pressure (LAP) was incorporated into an automatic feedback control system used to inflate a balloon cuff on the circumflex (Cfx) coronary artery. The system could produce stable increases in LAP to 15-20 mm Hg. The dominating system transfer function was the ratio of LAP to balloon volume (BV), which was characterized by a fixed delay (5 s), with LAP/BV = (8e(-jomegatau ))/(0.02 + jomega). The system was stabilized by a phase lead network to reduce oscillations of LAP. A total of seven experiments were conducted in three dogs, and testing of inotropic agents was possible in three experiments under stable conditions with the pump off after an hour or more of operation. Problems encountered were 0.003-0.008 Hz oscillations in LAP in three experiments, which could usually be controlled by reducing the system gain. Late stage ventricular fibrillation occurred in all three animals, but defibrillation was easily accomplished after deflating the Cfx balloon. This system produces reversible left ventricular failure solely due to ischemia, thus closely simulating clinical heart failure due to coronary insufficiency.

Laryngeal Tube® pilot balloon kinking in the presence of a bite block

To the Editor, Supraglottic airway devices are being developed with increasing frequency following the overwhelming success of the Laryngeal Mask Airway (LMA). The LMA, the ProSeal Laryngeal Mask Airway (PLMA), the Laryngeal Tube (LT), the Laryngeal Tube with integrated suctioning (LTS) and the Esophageal Tracheal Combitube (OTC) are currently the most evaluated and widespread supraglottic airway devices. The Laryngeal Tube (VBM Medizintechnik, Sulz, Germany) is a relatively new supraglottic device designed to secure a patent airway during either spontaneous breathing or controlled ventilation. The manufacturer’s standard LT has since been redesigned and modified to incorporate a suction port. The standard LT consists of an airway tube with a small distal cuff attached at the tip and a larger balloon proximal cuff located at the middle part of the tube (Fig. 1). The cuffs are inflated through a single pilot tube and balloon through which inflation pressure can be monitored. There are three black lines on the tube close to a standard 15 mm connector to indicate adequate depth of insertion when aligned with the teeth. The device is inserted while the patient’s head and neck are placed either in the sniffing position or in a neutral position. The tip of a well-lubricated LT is placed against the patient’s hard palate behind the upper incisors. The device is then advanced through the centre of the mouth until either resistance is felt or the device is almost fully inserted. The LT is inserted properly when the second bold black line on the tube has just passed between the upper and lower incisors. A bite block is inserted when ventilation is adequate, and the LT is secured in its wedge. Both are fixed in place with an elastic strap supplied with the device set. Once it is correctly placed with the bite block and the provided elastic strap, the LT will maintain its intended position after insertion. We have used the LT extensively for 3 years in at least 250 cases conducted under general anesthesia in all age groups. The device is used routinely to maintain the patient’s airway, either during spontaneous breathing or controlled ventilation. Although the cuff deflator is applied correctly, we have noted each time that the pilot balloon cuff is not deflated immediately before the LT is removed. We have observed that the pilot balloon tube continually slips and tightens in the groove between the LT shaft and the M. Singh, MD (&) Government Medical College Hospital, Chandigarh, India e-mail: manpreetdawar@hotmail.com

Dairy calf pneumonia: Effective treatment depends on early and accurate diagnosis

Dairy calf pneumonia is one of the most economically important diseases of calves. A delayed diagnosis could result endemic herd problem, prolonged use of antibiotics, high recurrence rate, pulmonary abscessation and ear infections. The key for effective control is the early detection of pneumonia and the accurate diagnosis of the etiologic factor. For the early detection, a respiratory disease score was assigned based on rectal temperature, character of nasal discharge, eye discharge or ear appearance, and presence of a cough. Each clinical sign has a point scale from 0 (normal) to 4 (severe). The respiratory disease score is the sum of points from the 4 categories of clinical signs, with increasing values representing progressive severity. The scoring system results in a minimum score of 0 and a maximum score of 12. Calves with score 5 or higher, having at least 2 clinical signs of respiratory disease, are considered sick and have to be treated. For the accurate diagnosis of the etiological agent the best tool in a live calf is bronchoalveolar lavage (BAL) fluid collection. Sampling of severely affected animals should be avoided. New acute cases are ideal. BAL is performed in sedated calves using a sterilized, flexible catheter with a 5-cc balloon cuff. The fresh BAL fluid sample is processed within 2 hours of collection or refrigerated until analysis. Part of the sample is used for microbiology and the remaining is submitted for cytology. BAL fluid that yields homogenous (&gt;106 CFU/ml) bacterial or positive Mycoplasma bovis culture is considered abnormal. A disproportionate lowering of macrophages (&lt;61%) or elevation of neutrophils (&gt;39%) provides evidence of an inflammatory response with or without a positive culture. The ideal antibiotic selection would be based on the antibiotic susceptibility pattern of lung pathogens after BAL fluid culture.

A New Liver Explant Fixation Technique

To the Editor.—Surgical intervention, including orthotopic liver transplantation, is a common modality used in the treatment of hepatocellular carcinoma. Accurate pathologic information is important to clinicians for appropriate staging and prognostication of such patients, particularly the identification of tumor multifocality. To identify all potentially neoplastic nodules, a meticulous gross examination is necessary.The gross examination of liver explants typically involves “bread-loafing” the specimen into slices as thin as practicably possible, ideally 0.5 cm or less in thickness. However, obtaining thin, uniform slices may be challenging in large unfixed hepatectomy specimens. In clinical practice, irregular slices thicker than 0.5 cm are frequently obtained, which increases the frequency of missed lesions, particularly small lesions. In addition, correlation with preoperative imaging studies becomes increasingly difficult in specimens cut irregularly.Formalin fixation firms the gross liver texture and improves the cutting process, making possible more uniform slices as compared with unfixed liver specimens. Ideally, formalin fixation should occur evenly throughout the entire liver parenchyma. Immersing intact specimens in formalin is generally inadequate for this purpose as formalin permeates through tissue slowly, resulting in a thin rind of fixed liver surrounding an unfixed core. To achieve uniform fixation, a group at Mayo Clinic (Rochester, Minn) developed a perfusion process that delivers formalin throughout the vasculature of the entire specimen1 via a continuous-perfusion pump for 3 days. This process is slow, labor intensive, and requires specialized equipment.An alternative technique that is quick, easy to use, inexpensive, and effective is herein described. It involves the use of an appropriately sized Foley catheter to cannulate the large vessels of the explanted liver (Figure 1). Once cannulated, the balloon cuff is inflated to prevent backflow. A catheter tip 60-mL syringe is then used to perfuse formalin into the hepatic vasculature. The entire process can be performed in less than 30 minutes. Because high pressures can easily be produced during perfusion that may inadvertently produce artifactual damage it is recommended that the force of only one hand be used. Good fixation results have been achieved with as little as 200 mL of formalin per large vessel (Figure 2). Following formalin perfusion, the intact specimen is floated in a bath of formalin overnight.In our experience, cannulation and perfusion of only the hepatic veins suffices to achieve adequate fixation. Portal vein cannulation is generally unnecessary but may be performed if anatomy permits. Hepatic artery cannulation is technically challenging and is of negligible added value.This technique results in a well-fixed, firm specimen that is easily sliced at the requisite 0.5-cm intervals, making possible a meticulous gross examination that aids in the identification of even small liver nodules.

The renal medullary circulation and nitric oxide in hyperinsulinemic-hypertensive rats

1. Insulin resistance may play a role in hypertensive patients. The renal medullary blood flow (MBF) is thought to be an important component of blood pressure and sodium balance. Nitric oxide (NO) activity within the renal medulla is the primary characterized factor in the maintenance of MBF and plays an important role in the pressure-natriuresis response. Because MBF, which is strongly influenced by the NO system, is thought to be an important component of blood pressure and sodium balance, we focused on MBF in hypertension being secondary in the development of insulin resistance. This study was designed to test the hypotheses that the MBF will be decreased and to determine the gene expression of three nitric oxide synthases (eNOS, nNOS, iNOS) in obese zucker rats (OZ). 2. 8–9 weeks male OZ and lean zucker rats (LZ) were divided into two group: Group1; OZ (n=7). Group2; LZ (n=7). Renal hemodynamic study; Each rat was instrumented with indwelling arterial and venous catheters. The tip of the arterial catheter was advanced to just below the level of left renal artery to permit continuous measurement of renal arterial pressure (RAP). For measurement of changes in renal cortical blood flow (CBF) and MBF in rats by laser-Doppler flowmetry, the optical fibers were implanted 2mm beneath the surface of the renal cortex to measure the net flux of red blood cells in the cortex and 6mm deep to monitor changes in the outer medulla. The RAP was adjusted from 160 to 80 mmHg with the use of balloon cuff. Gene expression study; We developed real-time RT-PCR that allows to absolutely quantify the gene expression of eNOS, nNOS, and iNOS in cortex and medulla of rat kidney using the standard curve and delta CT methods. 3. MAP was significantly increased in OZ. MBF was also significantly lower in OZ across a wide range of RAP without the significant change of CBF. The mRNA expression of eNOS and nNOS in renal medulla, which were significantly increased to a greater extent compared in renal cortex, were decreased in OZ compared in LZ. 4. MBF plays an important role in the development of hypertension in OZ. It seems reasonable to suppose that an impaired NO system could contribute to reduced MBF and sodium excretion, which would result in the development of hypertension in insulin resistance.

Comparison of ETT and LMA on Respiratory Mechanics during the Induction of General Anesthesia in Children

Background: Laryngeal mask airway (LMA) has recently been introduced as an alternative for the endotracheal tube. The respiratory mechanics and respiratory parameters during positive pressure ventilation (PPV) via the laryngeal mask airway (LMA) are not well known in children. So, we compared the effects of the endotracheal tube and the laryngeal mask airway on respiratory mechanics during the induction of general anesthesia in children. Methods: We studied sixty ASA physical status I and II healthy children undergoing general anesthesia. Anesthesia was induced with sleep dose ketamine 1.0 mg/kg i.v., supplemented with propofol 2 mg/kg, Rocuronium 1.0 mg/kg i.v and maintained with 50% nitrous oxide and 2.0 Vol% sevoflurane. After inserting the laryngeal mask airway, its cuff was inflated using a balloon cuff gauge until the intracuff pressure reached approximately 60 cmH2O. Adequacy of ventilation was assessed by observing the end tidal carbon dioxide wave form, chest wall movement, and by stethoscope auscultation. Data were collected with lung mechanics recorders (Ventcheck, Novametrix Medical System, U.S.) at 5 and 10 minutes after intubation or LMA insertion. The data included Peak Inspiratory Pressure (PIP), Mean Airway Pressure (MAP), Peak End Expiratory Pressure (PEEP), Inspired Tidal Volume (VTins), Expired Tidal Volume (VTexp), Airway resistance (Raw), and Compliance (Cdyn). Results: No significant difference was observed between the airway pressures, tidal volumes and gas leak fractions of the ETT and LMA groups. In terms of airway resistance and compliance, significant differences were observed between the two groups at 5 and 10 minutes. Conclusions: We conclude that the laryngeal mask airway is superior to endotracheal intubation in terms of airway resistance and compliance. The laryngeal mask airway offer an alternative for the children needing to avoid intubation under general anesthesia.

Efficacy of the Laryngeal Tube in General Anesthesia

Background: A prototype airway management device, a laryngeal tube, has been recently introduced in Korea. This study was designed to assess the efficacy of the laryngeal tube for airway management under general anesthesia. Methods: We studied thirty-six ASA physical status I and II patients undergoing general anesthesia. Anesthesia was induced with sleep dose propofol 2.0 mg/kg i.v., supplemented with fentanyl 1/kg, and maintained with 50% nitrous oxide and propofol. After inserting the laryngeal tube, its cuff was inflated using a balloon cuff gauge until the intracuff pressure reached approximately 65 cm. Adequacy of ventilation was assessed by observing the end tidal carbon dioxide wave form, chest wall movement and by stethoscope auscultation. Oropharyngeal leak pressure was also measured. Changes in heart rate, blood pressure, end-tidal carbon dioxide, airway pressure and oxygen saturation before induction, before insertion, 2, 5 and 10 minutes after insertion and 5 minutes after incision were recorded. Results: The first time success rate at achieving an effective airway was 30 in 36 (83%). The mean leak pressure was 22.9 4.6 mmHg. Heart rate, blood pressure, oxygen saturation, end-tidal carbon dioxide and airway pressure values remained stable during laryngeal tube insertion and during the surgical procedure. Conclusions: We conclude that the laryngeal tube is easy to place, allows adequate ventilation and has a lower incidence of complications. It may offer an alternative device for the oxygenation of non-intubated patients undergoing general anesthesia.

Post-extubation stridor in intensive care unit patients

To evaluate the incidence and identify factors associated with the occurrence of post-extubation stridor and to evaluate the performance of the cuff-leak test in detecting this complication. Prospective, clinical investigation. Intensive care unit of a university hospital. Hundred twelve extubations were analyzed in 112 patients during a 14-month period. A cuff-leak test before each extubation. The incidence of stridor was 12%. When we chose the thresholds of 130 ml and 12% to quantify the cuff-leak volume, the sensitivity and the specificity of the test were, respectively, 85% and 95%. The patients who developed stridor had a cuff leak significantly lower than the others, expressed in absolute values (372+/-170 vs 59+/-92 ml, p<0.001) or in relative values (56+/-20 vs 9+/-13%, p<0.001). Stridor was associated with an elevated Simplified Acute Physiology Score (SAPS II), a medical reason for admission, a traumatic or difficult intubation, a history of self-extubation, an over-inflated balloon cuff at admission to ICU and a prolonged period of intubation. These results provide a framework with which to identify patients at risk of developing a stridor after extubation. A low cuff-leak volume (<130 ml or 12%) around the endotracheal tube prior to extubation is useful in identifying patients at risk for post-extubation stridor.

Efficacy of the laryngeal tube

EDITOR: Dr Miller and colleagues reported that insertion of the laryngeal tube and ventilation through it were frequently difficult or unsatisfactory, particularly when they were inexperienced with its use [1]. They also reported that airway obstruction often occurred during anaesthesia in patients who were breathing spontaneously [1]. The laryngeal tube, which is designed to provide a patent airway during either spontaneous breathing or controlled ventilation, consists of an airway tube with a balloon cuff (proximal cuff) at the middle part of the tube and a smaller balloon (distal) cuff attached to the tip. The proximal cuff provides a seal by forming a plug in the upper pharynx and the distal cuff seals the oesophageal inlet [2]. The design of the laryngeal tube has been changed a few times to improve its effectiveness: the original device (Type 1) had two pilot tubes to inflate the two cuffs. Several improvements had been added to the next version (Type 2), and the major change was that the two cuffs could be inflated via a single pilot tube. Finally, the current device has a longer distal airway aperture. Miller and colleagues used the Type 1 device. There have been two other clinical reports of the use of the Type 1 laryngeal tube [2,3]. In one study, insertion of the laryngeal tube was successful at the first attempt and a patent airway was obtained in all of 30 patients [3], and in the other study insertion and ventilation of the lungs were successful at the first attempt in 47 of 50 patients [2]. Later, we reported a preliminary use of the Type 2 laryngeal tube in 10 patients in whom controlled ventilation was used [4]. In all 10 patients, the laryngeal tube provided a patent airway during the entire course of anaesthesia without necessitating adjusting the position of the device or the patient's head and neck [4]. These results contradict those of Miller and colleagues, in which even controlled ventilation was often unsatisfactory. Miller and colleagues cast doubt on the efficacy of the laryngeal tube by stating that '(is) it ethically justifiable to use a device such as the laryngeal tube that requires more extensive training than is shown here?' and that 'the point of the sequential analysis is to limit the extent of investigations, which are obviously not beneficial to patients' [1]. Our impression is contradictory, and we have found that insertion of the laryngeal tube is generally easy even for inexperienced personnel. To prove this point, we asked five anaesthetists to insert the device and attempt to ventilate patients' lungs through it. Each anaesthetist, who had had no experience of its use and to whom one of us demonstrated the method of insertion once before the trial, attempted to place the device in five patients. In 23 of 25 patients, it was possible to insert the laryngeal tube and to ventilate through it adequately at the first attempt. At the moment, there have been no reports of the use of the laryngeal tube during spontaneous breathing other than that of Miller and colleagues. Nevertheless, in patients in whom lung ventilation was controlled, placement of and ventilation through the laryngeal tube were usually successful in three papers [2-4], but often unsatisfactory in Miller and colleagues' study. Therefore, it seems too early to conclude that the device is not satisfactory for management of the airway during spontaneous breathing. T. Asai I. Hidaka T. Kubota S. Kawachi Department of Anaesthesia; Matsue Red Cross Hospital; Shimane, Japan

The Changes of Cuff Pressure from Endotracheal Intubation for Long-term Mechanical Ventilation

Background: A tracheal stenosis is caused by mucosal ischemic injury related to a high cuff pressure () of the endotracheal tube. In contrast, aspiration of the upper airway secretion and impaired gas exchange due to cuff leakage is related to a low . To prevent these complications, the should be kept appropriately because the appropriate appears to change according to the patient's daily respiratory mechanics. However, the constant cuff volume() has frequently been instilled to the cuff balloon on a daily basis to maintain the optimal instead of monitoring the directly at the patients' bedside. To address the necessity of continuous monitoring, the change in the was evaluated at various levels on a daily basis in patients with long-term mechanical ventilation. The utility of mercury column sphygmomanometer for the continuous monitoring was also investigated. Method: The change in according to the increase in was observed in 17 patients with prolonged endotracheal intubation for mechanical ventilation for 2 week or more. This maneuver measured the change in daily during the mechanical ventilation days. In addition, the measured by mercury column sphygmomanometer was compared with the measured by an automatic cuff pressure manager. Results : There were no statistically significant changes of during more than 14 days of intubation for mechanical ventilation. However the required to maintain the appropriate varied from 1.9 cc to 9.6 cc. In addition, the intra-individual variation of the was observed from 10 to 46 at constant 3 cc . The measured by the bedside mercury column sphygmomanometer is well coincident with that measured by the automatic cuff pressure manager. Conclusion: Continuous monitoring and management of the to maintain the appropriate level in order to prevent cuff related problems during long-term mechanical ventilation is recommended. For this purpose, mercury column sphygmomanometer may replace the specific cuff pressure monitoring equipment.