A Randomized Controlled Trial Comparing the Cuffed Oropharyngeal Airway and the Laryngeal Mask Airway in Spontaneously Breathing Anesthetized Adults

Background: The cuffed oropharyngeal airway (COPA), a modified Guedel airway, was compared with the laryngeal mask airway (LMA) during spontaneous breathing anesthesia. Specifically examined were ease of use, physiologic tolerance, and the frequency of problems.

Methods: Adult patients consented to random (2:1) assignment to either COPA (n = 302) or LMA (n = 151) for airway management during anesthesia with propofol, nitrous oxide, and oxygen.

Results: Ease of insertion was similar, but the first-time successful insertion rate was higher with the LMA (COPA, 81% compared with LMA, 89%; P = 0.05). More brief manipulations (head tilt, chin lift, jaw thrust) were reported in the COPA group (average total number of manipulations: COPA, 1.1 +/- 1.6 compared with LMA, 0.1 +/- 0.2; P <0.001). Continuous airway support was used more frequently in the COPA group (COPA, 30% compared with LMA, 0%; P < 0.0005). The incidences of aspiration, regurgitation, laryngospasm, wheezing, succinylcholine administration, oxygen saturation (SpO2) < 92%, failed use, and minor intraoperative problems were similar. When the airways were removed, blood was detected on the COPA less frequently than on the LMA (COPA, 5.8% compared with LMA, 15.3%; P = 0.001). The incidence of early and late sore throat was greater with the LMA (early: COPA, 4.7% compared with LMA, 21.9% [P = 0.001]; late: COPA, 8.4% compared with LMA, 16.1%; P = 0.01). The LMA did better than the COPA when anesthetists analyzed the technical aspects of the two devices.     

Cuff filling volumes and pressures in pediatric laryngeal mask airways

BACKGROUND: Hyperinflation of LMA cuffs carries the risk of airway morbidity by exerting pressure on laryngeal and pharyngeal structures. Cuff hyperinflation in LMAs can result from nitrous oxide diffusion into the LMA cuff and from deliberate manual cuff inflation. METHODS: In an in vitro set up, maximum recommended cuff filling volumes for size 1, 1.5, 2, 2.5, 3 disposable LMAs from different manufacturers [SoftSeal LMA (Portex); Unique LMA (Intavent); Marshall LAD, LaryngoSeal (Tyco)] and reusable Classic and ProSeal LMAs (Intavent) were inflated into completely emptied LMA-cuffs and into LMA-cuffs at resting volume. Cuff pressures were measured using a cuff manometer. Experiments were performed eight times using two exemplars of each brand/size. RESULTS: Maximum recommended cuff filling volumes for pediatric LMAs resulted in hyperinflation (cuff pressure >60 cmH(2)O) in almost all LMAs, starting with emptied cuff. Starting from resting cuff volume, the maximum recommended inflation volume resulted in cuff pressures of >120 cmH(2)O in all LMAs and sizes except in the ProSeal size 3 (101 +/- 1 cmH(2)O). CONCLUSIONS: Since the volume of air which is effectively required depends on several factors and varies between patients, the cuffs should be inflated only with the minimum volume of air required to form an effective seal with the respiratory and gastrointestinal tracts and the cuff pressure should be controlled.     

Comparative evaluation of the prolonged use of the cuffed oropharyngeal airway and the laryngeal mask airway in spontaneously breathing anaesthetized patients.

The cuffed oropharyngeal airway (COPA) was compared with the laryngeal mask airway (LMA) with respect to airway quality and respiratory adverse events in 140 spontaneously breathing patients undergoing procedures of duration more than 1 h. Patients were allocated randomly to receive either a COPA (n = 72) or a LMA (n = 68) for airway management during anaesthesia induced with propofol and maintained with sevoflurane, nitrous oxide and oxygen. Groups were similar when comparing the first-time successful insertion rates (COPA: 94.5%, LMA: 95.6%), but airway manipulations (head tilt, chin lift, jaw thrust) were reported more frequently in the COPA group, 27.8% vs. LMA, 4.4%; P = 0.0005. During the post-induction apnoeic period, all patients were ventilated manually and although, mean (SD) leak pressure was lower in the COPA group (18 (4) cm H2O vs. LMA, 22 (3) cm H2O; P < 0.0001), the tidal volumes achieved did not differ in both groups: COPA, 9.5 (4) mL kg-1 vs. LMA, 10.5 (4.5) mL kg-1. The incidences of intra-operative coughing, gagging, laryngospasm, oxygen desaturation and hypercarbia were similar in both groups. Although both devices are equivalent with respect to the overall respiratory problems during spontaneous breathing anaesthesia of intermediate or prolonged duration, the LMA was associated with fewer airway quality problems, suggesting that it is more efficacious in securing the airway.     

Use of cuffed oropharyngealvs laryngeal mask airway in elderly patients

PURPOSE: This study was designed to compare the new cuffed oropharyngeal airway (COPA) to the laryngeal mask airway (LMA) in elderly patients. METHODS: In a randomized, controlled study, 80 patients, age > or = 65, ASA I-III, undergoing urology procedures, were managed with either COPA or LMA. Propofol requirements for insertion of the devices, ease of insertion and removal, airway manipulations, mean arterial pressure, heart rate, P(ET)CO2, SpO2, peak inspiratory pressure, selection of the appropriate size of the device and leaks, fibreoptic visualization of larynx and complications were studied. RESULTS: There were more airway manipulations in the COPA group than in the LMA group (40% and 5% respectively) whereas P(ET)CO2 was higher in the LMA group (P < 0.05). In 60% of COPA patients the vocal cords could not be visualized but ventilation was adequate in all but two cases. Postoperative sore throat occurred in 20% of patients with LMA vs 10% with COPA). Bloody secretions on the device were present in two patients managed with LMA. CONCLUSION: In elderly patients COPA required more airway manipulations than the LMA. Laryngeal mask airway caused more sore throats, but was better for fibreoptic visualisation of the larynx. Both are excellent options when intubation is not indicated/desired.     

A comparison of postoperative sore throat after use of laryngeal mask airway and tracheal tube

Purpose We compared the degree of postoperative sore throat (PST) after use of a laryngeal mask airway (LMA; by two insertion techniques) and a tracheal tube (TT) in adult patients.Methods Eighty-six adult patients undergoing surgery of an extremity were randomized into three groups. The LMAs (size 4 for men, 3 for women) and TTs were lubricated with 2% lidocaine gel. After the induction of anesthesia, an LMA with the cuff deflated was inserted and then the cuff was inflated in group A, an LMA with the cuff inflated was inserted in group B, and the trachea was intubated using vecuronium in group C; staff anesthesiologists performed all these methods. LMA cuffs were inflated with the maximum recommended volume of air. TT cuffs were inflated with the minimum volume of air without gas leakage at 20cmH₂O pressure. The mode of ventilation depended on the individual anesthesiologists. Blood traces on the devices were examined after their removal. PST was rated immediately after anesthesia and on the first postoperative day, using a three-point score and a 100-mm visual analog scale, respectively.Results Most of the patients receiving an LMA breathed spontaneously and those receiving a TT underwent controlled ventilation. The ratio of positive blood traces on devices, as well as the degree of PST immediately after anesthesia, was similar in the three groups; however, on the first postoperative day, the severity of PST was greater in the LMA groups than in the TT group (P = 0.016). The severity of PST was similar with the two LMA insertion techniques.Conclusion In the conditions of our study, LMAs inserted with the cuff either fully inflated or deflated worsened PST compared with TTs.This work was presented in part at the 49th annual meeting of the Japanese Society of Anesthesiologists, Fukuoka, Japan, April 18–20, 2002     

Core temperature measurements through a new airway device, perilaryngeal airway (CobraPLA)

STUDY OBJECTIVE: The aim of this study was to test the hypothesis that the intraoperative pharyngeal temperatures obtained on the perilaryngeal airway (PLA), a novel airway device with a larger pharyngeal cuff (when inflated) than the laryngeal mask airway, are similar to tympanic membrane core temperatures. DESIGN: This study is a prospective, simultaneous device comparison. SETTING: This study was set at a university hospital. PATIENTS: The study patients included 14 adults with American Society of Anesthesiologists physical statuses I and II, scheduled for minor gynecological or orthopedic surgery. INTERVENTIONS: A PLA was inserted into the pharynx after induction of general anesthesia. Thermocouples were positioned at 3 sites on the PLA: (1) posterior portion of the head of the airway (tip), (2) midposterior portion of the cuff, and (3) left and right lateral-posterior portions of the cuff. Tympanic membrane thermocouples were inserted. MEASUREMENTS: Temperature readings from the airway and the tympanic membrane thermocouples were recorded every 15 minutes throughout surgery. MAIN RESULTS: Temperatures recorded from the lateral-posterior cuff were found to be virtually identical to tympanic membrane temperatures, with 97% of the values differing by less than 0.5 degrees C. Readings from the other 2 sites on the cuff differed considerably more from tympanic membrane values. CONCLUSIONS: These data suggest that the PLA can be adapted to monitor core temperature reliably.     

A comparison of the cuffed oropharyngeal airway (COPA) with the laryngeal mask airway (LMA) during manually controlled positive pressure ventilation

STUDY OBJECTIVE: To examine the cuffed oropharyngeal airway (COPA) during positive pressure ventilation (PPV) and to compare its reliability and efficacy with the laryngeal mask airway (LMA). DESIGN: Prospective, randomized, controlled trial. SETTING: University Hospital. PATIENTS: 60 adult ASA physical status I and II patients scheduled for urologic surgery. INTERVENTIONS: Patients were randomly assigned to be ventilated with a COPA (n = 33) or a LMA (n = 27) during a standardized anesthetic procedure. Following preoxygenation and induction with alfentanil and propofol, the respective airways were inserted. Patients were ventilated manually with the reservoir bag of the anesthesia respirator. Inspiratory airway pressure was limited to 20 cm H2O, and the target tidal volume was 7 ml/kg. Respiratory rate was adjusted to achieve an end-tidal pressure of carbon dioxide of 35 mmHg. Anesthesia was maintained with propofol, nitrous oxide in oxygen, and alfentanil, as appropriate. MEASUREMENTS AND MAIN RESULTS: We evaluated ease of insertion (nominal scale: easy, moderate, difficult, or impossible) and recorded the number of maneuvers performed during insertion until an airtight seal of the airway was achieved. Reliability for "hands free" ventilation--defined as ventilation without the need to further augment the position of the airway device manually--was determined (nominal scale: adequate ventilation, adequate ventilation with manual assistance, and inadequate ventilation leading to airway change). Ventilation and oxygenation parameters were derived from the anesthesia respirator and a capillary blood gas sample, respectively. The incidence of laryngopharyngeal discomfort and the amount of salivation were assessed by nominal scales. The COPA was easier to insert than the LMA (p < 0.001), but more positional maneuvers (p < 0.001) were necessary with this device. "Hands free" ventilation was achieved less often with the COPA (p < 0.02). Ventilation and oxygenation were comparable with both devices. The COPA was associated with less salivation (p < 0.01) and laryngopharyngeal discomfort (p < 0.05) than the LMA. CONCLUSION: Although effective ventilation can be accomplished with both devices, the LMA is more reliable for "hands free" ventilation than the COPA. The lower incidence of laryngopharyngeal discomfort and salivation with the COPA may be beneficial for patients at risk for developing laryngospasm.     

Airway management in spontaneously breathing anaesthetized children: comparison of the Laryngeal Mask Airway with the cuffed oropharyngeal airway

BACKGROUND: The efficacy and safety of the smallest size of the cuffed oropharyngeal airway (COPA) for school age, spontaneously breathing children was investigated and compared with the Laryngeal Mask Airway (LMA). METHODS: Seventy children of school age (7-16 years) were divided into two groups: the COPA (n=35) and the LMA (n=35). Induction was with propofol i.v. or halothane, nitrous oxide, oxygen and fentanyl. After depression of laryngopharyngeal reflexes, a COPA size 8 cm or an LMA was inserted. Ventilation was manually assisted until spontaneous breathing was established. For maintenance, propofol i.v. and fentanyl or halothane with nitrous oxide were used. Local anaesthesia or peripheral blocks were also used. RESULTS: Both extratracheal airways had a highly successful insertion rate, but more positional manoeuvres to achieve a satisfactory airway were required with the COPA, 28.6% versus LMA 2.9%. The need to change the method of airway management was higher (8.6%) in the COPA group. After induction, the need for assisted ventilation was higher in the LMA group 54.3% versus 20% in the COPA group. Airway reaction to cuff inflation was higher in the LMA group 14.3% versus COPA 5.7%. Problems during surgery were similar, except continuous chin support to establish an effective airway was more frequent (11.4%) in the COPA group. In the postoperative period, blood on the device and incidence of sore throat were detected less in the COPA group. CONCLUSIONS: The COPA is a good extratracheal airway that provides new possibilities for airway management in school age children with an adequate and well sealed airway, during spontaneous breathing or during short-term assisted manual ventilation.     

“Deep-forehead” temperature correlates well with blood temperature

PURPOSE: To evaluate the accuracy and precision of "deep-forehead" temperature with rectal, esophageal, and tympanic membrane temperatures, compared with blood temperature. METHODS: We studied 41 ASA physical status 1 or 2 patients undergoing abdominal and thoracic surgery scheduled to require at least three hours. "Deep-forehead" temperature was measured using a Coretemp thermometer (Terumo, Tokyo, Japan). Blood temperature was measured with a thermistor of a pulmonary artery. Rectal, tympanic membrane, and distal esophageal temperatures were measured with thermocouples. All temperatures were recorded at 20 min intervals after the induction of anesthesia. We considered blood temperature as the reference value. Temperatures at the other four sites were compared with blood temperature using correlation, regression, and Bland and Altman analyses. We determined accuracy (mean difference between reference and test temperatures) and precision (standard deviation of the difference) of 0.5 degrees C to be clinically acceptable. RESULTS: "Deep-forehead" temperature correlated well with blood temperature as well as other temperatures, the determination coefficients (r2) being 0.85 in each case. The bias for the "deep-forehead" temperature was 0.0 degrees C, which was the same as tympanic membrane temperature and was smaller than rectal and esophageal temperatures. The standard deviation of the differences for the "deep-forehead" temperature was 0.3 degrees C, which was the same as rectal temperature. CONCLUSIONS: We have demonstrated that the "deep-forehead" temperature has excellent accuracy and clinically sufficient precision as well as other three core temperatures, compared with blood temperature.     

A randomised crossover trial comparing a single‐use polyvinyl chloride laryngeal mask airway with a single‐use silicone laryngeal mask airway

We compared insertion rates of single‐use polyvinyl chloride laryngeal mask airways (LMAs) vs single‐use silicone LMAs in 72 anaesthetised patients. Both airways were produced by Flexicare Medical. Laryngeal mask airway insertion was successful on the first attempt in 68/72 (94%) polyvinyl chloride LMAs vs 64/72 (89%) silicone LMAs (p = 0.39). Overall insertion rates were 72/72 (100%) for the polyvinyl chloride LMAs and 71/72 (99%) for the silicone LMAs (p = 1.0). Mean (SD) insertion times were similar for polyvinyl chloride and silicone LMAs: 24.3 (5.1)s vs 24.8 (7.8)s (p = 0.64). Laryngeal mask airway position, as assessed using a fibrescope, was not different (p = 0.077). The median (IQR [range]) leak pressure was 16 (12–20 [6–30]) cmH₂O for the polyvinyl LMA and 18 (13–22 [6–30]) cmH₂O or the silicone LMA (p = 0.037). In conclusion, we did not find any important differences between polyvinyl chloride and silicone laryngeal mask airways.     

The ProSeal has a shorter life-span than the Classic laryngeal mask airway

We tested the hypothesis that the life-span of the ProSeal laryngeal mask airway (LMA) is shorter than the Classic LMA. We also compared residual cuff volumes and changes in elastance and permeability with use. Six new size 4 ProSeal LMAs and 6 new size 4 Classic LMAs were tested. Each LMA underwent a simulated clinical use cycle until it failed the pre-use check tests. The simulated clinical use cycle comprised: i) inflating the cuff to the maximum recommended volume for 1 h; ii) immersion in an enzymatic solution for 3 min; iii) washing the external and internal surfaces; iv) automatic washing for 14 min (< or =85 degrees C); v) drying for 30 min (< or =75 degrees C); and vi) autoclaving at 134 degrees C for 4 min at 206 kPa. Before the first cycle and every 10 subsequent cycles, the cuff was inflated with 40 mL air and the intracuff pressure was measured immediately and 3 h later. The initial intracuff pressure was taken to be an inverse measure of the elastance or resistance to deformation, and the intracuff pressure change were taken as a measure of the permeability. The residual cuff volume was determined for 10 Classic and 10 ProSeal size 4 LMAs using a gas dilution technique. The mean +/- sd (range) longevity for the ProSeal LMA and Classic LMA was 82 +/- 23 (45-109) uses and 133 +/- 35 (76-176) uses, respectively. The ProSeal LMA has a shorter life-span than the Classic LMA (P = 0.01). For the ProSeal LMA, there was no change in elastance or permeability with use. For the Classic LMA, there was a decrease in elastance (P < 0.0001) and an increase in permeability (P < 0.0001) with use. The residual cuff volume was higher for the ProSeal LMA (2.6 +/- 1.3 mL versus 1.5 +/- 0.9, P = 0.04). We conclude that the life-span of the ProSeal LMA is shorter than the Classic LMA, but both exceed the manufacturer's recommendations of 40 uses. We recommend that reusable LMA devices be discarded when they fail the pre-use check tests, rather than after a specific number of uses.     

Changes in the intracuff pressure of the laryngeal masks airway caused by repeated use

PURPOSE: To observe the changes in permeability and elasticity in the cuff of the laryngeal mask airway (LMA) caused by repeated use. METHODS: In vitro use was simulated on six # 4 LMAs on 140 occasions. Ambient air was insufflated into the cuff until a value of 200 mmHg intracuff pressure (ICP) was reached, and this was maintained for 50 min. After each simulation, the LMA was sterilized at 121 degrees C for 20 min. After every 20 simulations insufflation of 40 ml air was carried out to determine the maximum value of ICP (initial ICP), and after three hours, spontaneous deflation (final ICP) was measured. The values of initial and final ICPs throughout the eight tests were attributed to the elastance and the permeability of the cuff respectively. At the end of the study the thickness of the wall of the cuffs was measured using an optical microscope. RESULTS: The initial ICP with the new LMA (first test) was of 191 +/- 4.4 mmHg. This value increased from the fifth test onwards until the end of the study. The value of the final ICP in the first test was 111 +/- 3 mmHg and decreased with successive sterilizations. Between 80 and 100 simulations, initial ICP increased from 186.5 +/- 2.9 to 191.7 +/- 2.3 (P = 0.006). The thickness of the wall (694 +/- 17 microns) was inversely related with the elasticity and the permeability of the cuff. CONCLUSIONS: The "safe" life-span of the cuff of the LMAs, measured by the initial modifications of the physical properties of the silicone during simulations, was estimated to be 80-100 uses and was related to the thickness of its wall.     

The pressor response after laryngeal mask or cuffed oropharyngeal airway insertion

BACKGROUND: Since the cuffed oropharyngeal airway (COPA) has been suggested to cause less pharyngeal trauma than the laryngeal mask airway (LMA), we conducted a prospective, randomised study to compare haemodynamic changes after placing either the COPA or LMA in healthy anaesthetised adults. METHODS: After standard midazolam premedication (0.05 mg kg(-1) IV), general anaesthesia (IV propofol 2 mg kg(-1)) was induced in 60 ASA physical status I-II, 18-65-yr-old patients, who were randomly allocated to receive COPA (n=30) or LMA (n= 30) placement and then mechanically ventilated using a 60% nitrous oxide and 1% isoflurane in oxygen mixture (TV=8 ml kg(-1), RR=12 b.p.m., I/E=1/2). Haemodynamic variables were recorded 20 min after the midazolam premedication (baseline), and then every 1 min until 10 min after general anaesthesia induction. RESULTS: Nine patients of group COPA (30%) required chin lift, jaw thrust or head tilt to maintain adequate ventilation, while no problems were observed in the LMA group (P<0.0005); however, in no case did the designed extratracheal airway have to be removed due to unsuccessful mechanical ventilation, and no signs of gastric insufflation or regurgitation were reported. The maximum mean changes in haemodynamic variables were more marked after LMA placement (SAP: 12%+/-13%; DAP: 11%+/-18%; HR: 13%+/-16%) than COPA placement (SAP: -3%+/-18%; DAP: -5%+/-16%; HR: 4%+/-13%) (P<0.005, P<0.005, and P<0.01 for SAP, DAP and HR, respectively). Group LMA showed higher SAP and DAP values than group COPA only during the first 3 min after airway insertion. CONCLUSION: In healthy, anaesthetised patients, placing a cuffed oropharyngeal airway is associated with smaller cardiovascular changes after airway insertion compared with the laryngeal mask airway.     

The accuracy and precision of body temperature monitoring methods during regional and general anesthesia

We tested the hypotheses that accuracy and precision of available temperature monitoring methods are different between spinal anesthesia (SA) and general anesthesia (GA), and that patients receiving SA are at equal risk for hypothermia as those receiving GA. Patients scheduled for radical retropubic prostatectomy were enrolled. Either GA (n = 16) or SA (n = 16) was given according to patient and clinician preference. Temperatures were monitored with thermocouple probes at the tympanic membrane, axilla, rectum, and forehead skin surface. Tympanic temperatures were also measured with an infrared device, and forehead skin temperatures were monitored with two brands of liquid crystal thermometer strips. Accuracy and precision of these monitoring methods were determined by using tympanic membrane temperature, measured by thermocouple, as the reference core temperature (T(c)). At the end of surgery, T(c) was similar between SA (35.0 +/- 0.1 degrees C) and GA (35.2 +/- 0.1 degrees C) (P = 0.44). Accuracy and precision of each temperature monitoring method were similar between SA and GA. Rectal temperature monitoring offered the greatest combination of accuracy and precision. All other methods underestimated T(c). These findings suggest that patients receiving SA or GA are at equal and significant risk for hypothermia, and should have their temperatures carefully monitored, recognizing that most monitoring methods underestimate T(c). IMPLICATIONS: Body temperature should be monitored during spinal anesthesia because patients are at significant risk for hypothermia. Rectal temperature is a valid method of measuring core temperature, whereas other methods tend to underestimate true core temperature.     

The target plasma concentration of propofol required to place laryngeal mask versus cuffed oropharyngeal airway

To determine the target plasma concentration of propofol required to place either a laryngeal mask airway (LMA) or a cuffed oropharyngeal airway (COPA), we started a continuous target-controlled infusion of propofol in 60 ASA physical status I or II unpremedicated patients scheduled for minor orthopedic surgery with peripheral nerve block. The target plasma concentration of propofol was initially set at 2 microg/mL. When the effect-site calculated concentration of propofol was equal to the plasma concentration according to the computer simulation, the target plasma concentration was increased by 0.5-microg/mL steps until successful placement of either the LMA (n = 30) or the COPA (n = 30). The mean target plasma concentration of propofol required to place a LMA was 4.3 +/- 0.8 microg/mL compared with 3.2 +/- 0.6 microg/mL to place a COPA (P < 0.001). To successfully place the airways in 95% of patients, the target plasma concentration of propofol had to be increased up to 4 microg/mL for the COPA and 6 microg/mL for the LMA. We conclude that placing a LMA in healthy, unpremedicated patients requires target plasma concentrations of propofol higher than those required for placing a COPA. Implications: We evaluated the use of target-controlled infusion of propofol to place extratracheal airways in this prospective, randomized study and demonstrated that the target plasma concentration of propofol required to successfully place a laryngeal mask in >95% of healthy, unpremedicated patients is 6 microg/mL, compared with 4 microg/mL to place a cuffed oropharyngeal airway.     

Water flow between the upper esophagus and pharynx for the LMA and COPA in fresh cadavers

PURPOSE: In this randomised, crossover cadaver study, we determine the esophageal pressure (EP) at which water flow occurs between the upper esophagus and pharynx for the laryngeal mask airway (LMA) and cuffed oropharyngeal airway (COPA). METHODS: Ten male and ten female cadavers were studied. The infusion set of a pressure controlled, continuous flow pump was inserted into the upper esophagus and ligated into place. The EP was increased in 2 cm H2O increments. This was performed without an airway device (controls) and over a range of cuff volumes for the LMA (0-40 ml) and COPA (0-60 ml). Regurgitation pressure (RP) was the EP at which fluid was first seen with a fibreoptic scope in the hypopharynx (controls) and above or below the cuff (LMA and COPA). RESULTS: The RP was higher for the LMA than for the COPA and controls (P<0.0004), and RP was similar for COPA and controls. There was an increase in RP with increasing cuff volume for the LMA from 0 to 10 ml (P<0.0001). There were no increases in RP with increasing cuff volume for the COPA. The EP at which fluid leaked above and below the cuff was similar for the LMA at all cuff volumes. The EP at which fluid leaked above the cuff was higher than below the cuff for the COPA when the cuff volume was 40 ml (P<0.0001). CONCLUSION: In fresh cadavers, the LMA provides better airway protection from fluid in the upper esophagus than the COPA.     

A Novel Modified Laryngeal Mask Airway Allowing Full Separation of the Digestive and Respiratory Tracts,Along With Double-Catheter Ventilation,Diagnosis, and Treatment

The aim of this study was to design a novel, modified, multifunctional, and safe laryngeal mask airway (LMA). We designed an LMA with an internal catheter extending beyond the tip of the cuff. The protruding end of the internal catheter was provided with a catheter cuff, the space between the internal and external catheters was ventilatory, and the inlet ends of the 2 catheters were provided with standard connectors. We found that this design prevented reflux or aspiration of gastric content into the airway, prevented LMA dislocation, allowed ventilation through both the internal and external catheters, and allowed endoscopic examination and treatment of the gastrointestinal and respiratory tracts through both the internal and external catheters. This design overcomes the drawbacks and extends the functions of previous LMAs, offering a new approach to the development of LMAs.Key words: Laryngeal mask airway, Catheter, Ventilation, DesignSince the invention of the first laryngeal mask airway (LMA) in 1982, LMAs have been used worldwide for supraglottic airway management. Although LMAs have shown marked success in clinical anesthesia, the management of difficult airways, and emergency treatment, these devices also have disadvantages.^1–6 For example, an LMA cannot prevent stomach contents from refluxing into the respiratory tract and may move during surgery, affecting normal ventilation. In addition, an LMA may allow air leakage into the gastrointestinal tract during positive pressure ventilation, resulting in serious gastrointestinal distension and corresponding complications. Further, some patients may have difficulty positioning the LMA, thus requiring substitution of other ventilation devices. Finally, use of an LMA prevents an endoscope from entering the digestive tract for examination and treatment.     

Intraoperative temperature monitoring sites in infants and children and the effect of inspired gas warming on esophageal temperature

This study tested the hypotheses that 1) temperatures of "central" sites are similar in infants and children undergoing noncardiac surgery and 2) airway heating and humidification increases distal esophageal temperature. Twenty children were randomly assigned to receive 1) active airway humidification using an airway heater and humidifier set at 37 degrees C (N = 8), 2) passive airway humidification using a heat and moisture exchanger (N = 6), or 3) no airway humidification and/or heating (control, N = 6). There were no statistically significant differences between tympanic membrane, esophageal, rectal, and axillary temperatures. The temperatures of the peripheral skin surface (forearm and fingertip) were significantly lower than tympanic membrane temperature and significantly different from each other. Although esophageal and tympanic membrane temperatures in the entire group were similar, esophageal temperatures in patients receiving active and passive airway humidification were about 0.35 degrees C above tympanic temperatures after induction of anesthesia. In contrast, esophageal temperatures in patients without airway humidification were 0.25 degrees C below tympanic temperatures after induction of anesthesia. Esophageal-tympanic membrane temperature differences in the patients given active and passive humidification differed significantly from the corresponding sum in the control group at all times, but not from each other.     

Environmental monitoring of sevoflurane and nitrous oxide using the cuffed oropharyngeal airway

We compared exposure to sevoflurane (SEV) and nitrous oxide (N(2)O) during ventilation using the cuffed oropharyngeal airway (COPA) with waste gas exposure using a conventional face mask (FM) without any additional airways or face straps and with the laryngeal mask airway (LMA). Trace concentrations of SEV and N(2)O were assessed by using a direct reading spectrometer during 33 surgical procedures under general anesthesia. Measurements were made at the patients' mouths and in the anesthesiologists' breathing zones. Mean +/- SD concentrations of SEV and N(2)O measured at the patients' mouths were comparable in the COPA (SEV, 8.1 +/- 12.2 ppm; N(2)O, 213.3 +/- 289.2 ppm) and LMA (SEV, 18.5 +/- 25.8 ppm; N(2)O, 283.4 +/- 361.0 ppm) groups but differed significantly from the FM group (SEV, 46.5 +/- 19.6 ppm; N(2)O, 750.7 +/- 308.3 ppm). These values resulted in a comparable contamination of the anesthesiologists' breathing zones (SEV, 0.5 +/- 0.2 ppm; N(2)O, 5.7 +/- 4.8 ppm) for the COPA group, compared with the LMA group (SEV, 1.0 +/- 0.9 ppm; N(2)O, 12.2 +/- 14.3 ppm). This differed significantly from the FM group (SEV, 2.2 +/- 0.9 ppm; N(2)O, 37.5 +/- 14.3 ppm). We conclude that the use of the COPA during short surgical interventions has an occupational safety comparable to that of the LMA and that both resulted in less contamination through waste anesthetic gases. Therefore, the COPA may be a valuable alternative to the conventional FM. IMPLICATIONS: In this study, we have shown that the occupational exposure to waste anesthetic gases is comparable when using the cuffed oropharyngeal airway (COPA) and the laryngeal mask airway and is increased when using the face mask. Therefore, the COPA may be a valuable alternative to the conventional face mask during short surgical procedures.