Use of the Cuffed Oropharyngeal Airway as an Alternative to the Laryngeal Mask Airway with Positive-pressure Ventilation

Background: The cuffed oropharyngeal airway is a modified Guedel-type oral airway with a cuff at its distal end. The objectives of this study were to compare the ability of the cuffed oropharyngeal airway and the laryngeal mask airway to provide positive-pressure ventilation during general anesthesia, and to assess their relative ease of use and ability to reduce total fresh gas flow rates.

Methods: In this prospective, randomized study, a cuffed oropharyngeal airway (n = 25) or a laryngeal mask airway (n = 25) device was inserted after induction of anesthesia intravenously using 2 mg/kg propofol. While anesthesia was maintained with sevoflurane and nitrous oxide, the leak pressure, leak fraction (the fractional difference between the inspired and expired tidal volume), minimum fresh gas flow rate, and need for airway manipulations were determined. The anesthesia provider who inserted the device completed an evaluation form at the end of the 15-min study period.

Results: Positive-pressure ventilation was established successfully on the first attempt in 92% of the patients when the cuffed oropharyngeal airway was used and in 88% of the patients when the laryngeal mask airway device was used. However, manipulations of the airway device were necessary more frequently (8 vs. 1 patients; P < 0.05) and the leak pressure was less (22 +/- 6 cm water vs. 26 +/- 5 cm water; P < 0.05) with the cuffed oropharyngeal airway than with the laryngeal mask airway. In addition, the leak fraction (0.19 +/- 0.18 vs. 0.31 +/- 0.22; P < 0.05) and the minimum fresh gas flow rate (1.3 +/- 1.5 vs. 2.4 +/- 2.5; P = 0.12) were less in the laryngeal mask airway group.     

The ProSeal Laryngeal Mask Airway: A Randomized, Crossover Study with the Standard Laryngeal Mask Airway in Paralyzed, Anesthetized Patients

Background: The ProSeal laryngeal mask airway (PLMA) is a new laryngeal mask device with a modified cuff to improve seal and a drainage tube to provide a channel for regurgitated fluid and gastric tube placement. In the present randomized, crossover study, the authors tested the hypothesis that ease of insertion, airway sealing pressure, and fiberoptic position differ between the PLMA and the standard laryngeal mask airway (LMA). For the PLMA, we also assess ease of gastric tube placement and the efficacy of an introducer tool.

Methods: Sixty paralyzed, anesthetized adult patients were studied. Both devices (only size 4) were inserted into each patient in random order. Airway sealing pressure and fiberoptic position were determined during cuff inflation from 0 to 40 ml in 10-ml increments. Gastric tube insertion was attempted with the PLMA if there was no gas leak from the drainage tube. In 60 additional patients, ease of insertion for the PLMA was compared with and without an introducer.

Results: First-time success rates were higher (60 of 60 vs. 52 of 60;P = 0.003) and the effective airway time shorter (9 +/- 3 s vs 20 +/- 18 s;P < 0.0001) for the LMA. There were no failed uses of either device within three attempts. Airway sealing pressure was 8-11 cm H2O higher for the PLMA at all cuff volumes (P < 0.00001) and was higher in females for both devices. Fiberoptic position was better with the LMA at all cuff volumes (P < 0.00001), but vocal cord visibility was similar (LMA, 59 of 60; PLMA, 56 of 60). For the PLMA, gastric tube placement was successful in 58 of 58 patients and took 9 +/- 5 s. First-time success rates were higher (59 of 60 vs 53/60;P = 0.03) and the effective airway time shorter (15 +/- 13 s vs 23 +/- 18 s;P = 0.008) with the introducer.     

A Randomized Controlled Trial Comparing the ProSeal™ Laryngeal Mask Airway with the Laryngeal Tube Suction in Mechanically Ventilated Patients

Background: The ProSeal(TM) Laryngeal Mask Airway (PLMA) (Laryngeal Mask Company, Henley-on-Thames, United Kingdom) is a new laryngeal mask with a modified cuff designed to improve its seal and a drain tube for gastric tube placement. Similarly, the Laryngeal Tube Suction (LTS) (VBM Medizintechnik Gmbh, Sulz a.N, Germany) is a new laryngeal tube that also has an additional channel for gastric tube placement. This study compared the placement and functions of these two devices.

Methods: One hundred fifty patients undergoing general anesthesia for elective surgery were randomly allocated to the PLMA (n = 75) or LTS (n = 75). Oxygenation and ventilation, ease of insertion, fiberoptic view, oropharyngeal leak pressure, ventilatory data, ease of gastric tube insertion, and postoperative airway morbidity were determined.

Results: After successful insertion of the devices in 96% of patients with the PLMA and in 94.4% with the LTS it was possible to maintain oxygenation, ventilation, and respiratory mechanics during the entire duration of surgery. Successful first and second attempt insertion rates were 57 patients (76%) and 15 patients (20%), respectively, for the PLMA and 60 patients (80%) and 11 patients (14.6%), respectively, for the LTS. Airway placement was unsuccessful with the PLMA in three patients and with the LTS in four patients. Time to achieve an effective airway was 36 +/- 24 s with the PLMA versus 34 +/- 25 s with the LTS. Gastric tube insertion was possible in 97.3% of patients with the PLMA and in 96% with the LTS.     

Pulmonary Airway Resistance with the Endotracheal Tube versus Laryngeal Mask Airway in Paralyzed Anesthetized Adult Patients

Background: The hypothesis that airway resistance is less with the laryngeal mask airway than with the endotracheal tube was tested.

Methods: Thirty-six paralyzed, anesthetized adult patients with no respiratory disease (American Society of Anesthesiologists physical status 1-3; age, 18-80 yr) were randomly allocated (9 men, 9 women in each group) to receive either a size-4 laryngeal mask airway or an endotracheal tube (men, 9-mm ID; women, 8-mm ID). A pulmonary monitor with flow transducer and esophageal balloon was used to measure peak airway pressure and mean airway resistance (device resistance plus pulmonary airway resistance) at three different tidal volumes (5, 10, and 15 ml/kg). Device resistance was measured in vitro with the distal end of the endotracheal tube or laryngeal mask airway open to the atmosphere and using the same ventilator settings. Pulmonary airway resistance was derived by subtracting the mean device resistance from the mean airway resistance.

Results: Peak airway pressure, mean airway resistance, device resistance, and pulmonary airway resistance were greater for the endotracheal tube (all P < 0.0001).     

Fiberoptic Intubation and Laryngeal Morbidity: A Randomized Controlled Trial

Background: Tracheal intubation with neuromuscular blocking agents is associated with a low incidence of minor vocal cord sequelae (8%). The aim of this noninferiority trial was to demonstrate that the frequency of vocal cord sequelae after fiberoptic intubation with a flexible silicone tube without neuromuscular blocking agents was less than 25% (maximum tolerable inferiority).

Methods: Two-hundred seventy patients were prospectively randomized to two groups. All intubations were performed by anesthesiologists with extensive experience in fiberoptic and conventional techniques. Fiberoptic nasotracheal intubation consisted of a bolus dose of 2 [mu]g/kg fentanyl; 0.25 ml cocaine instillation, 10%, into nasal canals; cricothyroid injection of 2 ml lidocaine, 1%; bronchoscopy; administration of 0.3 mg/kg etomidate; and advancing a flexible silicone tube after loss of consciousness. Orotracheal intubation was performed with a polyvinyl chloride tube after induction with 2 [mu]g/kg fentanyl, 2 mg/kg propofol, and 0.6 mg/kg rocuronium. Patients were examined by laryngoscopy before surgery, 24 h after surgery, and daily until complete restitution. Postoperative hoarseness was assessed by a standardized interview.

Results: The incidence of vocal cord sequelae was 11 out of 130 (8.5%) in the fiberoptic group versus 12 out of 129 (9.3%) in the control group (chi-square = 0.057, df = 1, P = 0.81; upper limit of the one-sided 95% confidence interval for the difference: +5.1%). There were no persistent injuries. The incidence of postoperative hoarseness was 4% in both groups.     

喉罩气道的临床研究与应用

总结４２例择期整形外科手术病人应用喉罩气道（ＬＭＡ）的临床体会。重点观察了喉罩的置入情况，置入时的循环反应，不同诱导方法时置入条件以及用纤维喉罩的到位和喉罩内声门和会厌的情况。作者体会：（１）ＬＭＡ操作简单，置入容易，损伤小，置入时对循环系统明显影响；（２）吸入和静吸复合诱导均可获得好置入条件，其中吸入诱导效果最好，是小儿诱导的首选方法；（３）解决ＬＭＡ置入中咽后壁受阻的最有效方法是借助于直接喉镜     

Pharyngeal Mucosal Pressure and Perfusion: A Fiberoptic Evaluation of the Posterior Pharynx in Anesthetized Adult Patients with a Modified Cuffed Oropharyngeal Airway

Background: Pharyngeal airway devices can exert substantial pressures against the pharyngeal mucosa. The authors assess the relation between pharyngeal mucosal perfusion and directly measured mucosal pressure (MP) in the posterior pharynx using a fiberoptic technique with a modified cuffed oropharyngeal airway (COPA). The authors also measure in vivo intracuff pressure (CP), airway sealing pressure and MP at four locations using an unmodified COPA.

Methods: Twenty adult patients, American Society of Anesthesiologists status I or II, undergoing general anesthesia were allocated randomly to receive either (1) a COPA with a millimeter microchip sensor fixed on the external cuff surface to record distal posterior pharyngeal MP or (2) a COPA with a fiberoptic scope inserted inside the cuff to record digitized images of the distal posterior pharyngeal mucosa. MP and digitized images were obtained at the same location over an in vivo CP range of 10-160 cm H2O in 10- to 20-cm H2O increments. The digitized images were scored according to blood vessel caliber and mucosal color by two investigators blinded to MP and CP. In an additional 20 matched patients, in vivo CP, airway sealing pressure, and MP was measured at four different cuff locations (corresponding to the anterior, lateral, and posterior pharynx and the distal oropharynx) with increasing cuff volume.

Results: Blood vessel caliber and mucosal color was normal in all patients when the mean mucosal pressure was 17 cm H2O. Blood vessel caliber was first reduced when the mean mucosal pressure was 34 cm H2O. There was a progressive incremental reduction in blood vessel caliber and mucosal color when the mean mucosal pressure increased from 34 to 80 cm H2O (P<= 0.05). Complete blood vessel collapse and mucosal paling first occurred with the mean mucosal pressure was 73 cm H2O and was present in 90% of patients when the mean mucosal pressure was 80 cm H2O. Mean MP was always higher in the posterior pharynx compared with the other locations when the cuff volume was 20 ml or greater (P< 0.001). In vivo CP is an excellent predictor of mucosal pressure. Mean (95% confidence interval [CI]) MP in the posterior pharynx was 35 (5-67) and 78 (50-109) cm H2O when the airway sealing pressure was 10 (6-16) and 17 (13-21) cm H2O respectively.     

Comparison of Three Disposable Extraglottic Airway Devices in Spontaneously Breathing Adults: The LMA-Unique ™, the Soft Seal Laryngeal Mask, and the Cobra Perilaryngeal Airway

Background: The authors compared three disposable extraglottic airway devices in spontaneously breathing anesthetized adults: the LMA-Unique (TM) (LMA-U; The Laryngeal Mask Company, San Diego, CA), the Soft Seal(R) laryngeal mask (SS-LM; Portex Ltd., Hythe, United Kingdom), and the Cobra perilaryngeal airway (Cobra-PLA (TM); Engineered Medical Systems, Inc. Indianapolis, IN).

Methods: Three hundred twenty consecutive adults (American Society of Anesthesiologists physical status I-III; aged 18-80 yr) were randomly allocated for airway management with one of the three devices. Anesthesia was with fentanyl-propofol for induction and a sevoflurane-nitrous oxide-oxygen-fentanyl mixture for maintenance. Intraoperative data were collected by an unblinded observer about ease of insertion, effective airway time, oropharyngeal leak pressure, anatomical position (determined with a rigid endoscope), intracuff pressure changes, and airway trauma. Data were collected by a blinded observer about sore throat, dysphagia, and dysphonia 2 h after surgery.

Results: Insertion was easier with the LMA-U and SS-LM than with the Cobra-PLA (P < 0.02), but the overall failure rates were similar. Effective airway times were similar among groups. Oropharyngeal leak pressure was lower with the LMA-U than with the SS-LM and Cobra-PLA (P < 0.001). Intracuff pressure increased during surgery with all extraglottic airway devices. Anatomical position was better with the Cobra-PLA than with the SS-LMA (P < 0.001) and better with the SS-LM than with LMA-U (P < 0.001). Blood staining was detected more frequently with the Cobra-PLA than with the LMA-U and SS-LM (P < 0.001), but there were no differences in airway morbidity.     

Prospective Randomized Controlled Trial on the Use of Flexible Reinforced Laryngeal Mask Airway (LMA) During Total Thyroidectomy: Effects on Postoperative Laryngopharyngeal Symptoms

Background

Sore throat, hoarseness, dysphagia, and cough are common laryngopharyngeal discomforts after thyroidectomy. The incidence and severity of laryngopharyngeal symptoms after the use of a flexible reinforced laryngeal mask airway (LMA) were compared with those that occur after the use of a plain endotracheal tube in patients after thyroidectomy.

Methods

Seventy-six patients scheduled for total thyroidectomy were randomized into a plain endotracheal tube group (group E) or a flexible reinforced LMA group (group L). Total intravenous anesthesia (propofol and remifentanil) was used for maintenance of anesthesia. Hemodynamic variables were recorded during induction of anesthesia. The incidence and severity (100-point numerical rating scales) of laryngopharyngeal symptoms, including sore throat, hoarseness, dysphagia, and cough, were assessed at 1, 24, and 48 h after surgery.

Results

All patients were placed successfully with an endotracheal tube or a flexible reinforced LMA. The postoperative incidence and severity of sore throat (25 vs. 33 at 24 h, p = 0.035, 17 vs. 28 at 48 h, p = 0.017; 50 [0–100] vs. 80 [20–100] at 1 h, p = 0.002; 30 [0–80] vs. 50 [0–100] at 24 h, p < 0.001; 0 [0–40] vs. 30 [0–90] at 48 h, p < 0.001) and hoarseness were lower in group L than in group E. At 48 h postoperatively, dysphagia (p = 0.005) and cough (p = 0.028) occurred less frequently in group L than in group E patients.

Conclusion

A flexible reinforced LMA placed during surgery decreases the incidence and severity of laryngopharyngeal symptoms and is a feasible anesthetic tool compared with a conventional endotracheal tube for thyroidectomy.     

Pressure Support Ventilation versus Continuous Positive Airway Pressure with the Laryngeal Mask Airway: A Randomized Crossover Study of Anesthetized Adult Patients

Background: The authors tested the hypothesis that pressure support ventilation (PSV) provides more effective gas exchange than does unassisted ventilation with continuous positive airway pressure (CPAP) in anesthetized adult patients treated using the laryngeal mask airway.

Methods: Forty patients were randomized to two equal-sized crossover groups, and data were collected before surgery. In group 1, patients underwent CPAP, PSV, and CPAP in sequence. In group 2, patients underwent PSV, CPAP, and PSV in sequence. PSV comprised positive end expiratory pressure set at 5 cm H2O and inspiratory pressure support set at 5 cm H2O above positive end expiratory pressure. CPAP was set at 5 cm H2O. Each ventilatory mode was maintained for 10 min. The following data were recorded every minute for the last 5 min of each ventilatory mode and the average reading taken: end tidal carbon dioxide, oxygen saturation, expired tidal volume, leak fraction, respiratory rate, noninvasive mean arterial pressure, and heart rate.

Results: In both groups, PSV showed lower end tidal carbon dioxide (P < 0.001), higher oxygen saturation, (P < 0.001), and higher expired tidal volume (P < 0.001) compared with CPAP. In both groups, PSV had similar leak fraction, respiratory rate, mean arterial pressure, and heart rate compared with CPAP. In group 1, measurements for CPAP were similar before and after PSV. In group 2, measurements for PSV were similar before and after CPAP.     

Laryngeal Morbidity and Quality of Tracheal Intubation: A Randomized Controlled Trial

Background: Vocal cord sequelae and postoperative hoarseness during general anesthesia are a significant source of morbidity for patients and a source of liability for anesthesiologists. Several risk factors leading to laryngeal injury have been identified in the past. However, whether the quality of tracheal intubation affects their incidence or severity is still unclear.

Methods: Eighty patients were randomized in two groups (n = 40 for each) to receive a propofol-fentanyl induction regimen with or without atracurium. Intubation conditions were evaluated with the Copenhagen Score; postoperative hoarseness was assessed at 24, 48, and 72 h by a standardized interview; and vocal cords were examined by stroboscopy before and 24 and 72 h after surgery. If postoperative hoarseness or vocal cord sequelae persisted, follow-up examination was performed until complete restitution.

Results: Without atracurium, postoperative hoarseness occurred more often (16 vs. 6 patients;P = 0.02). The number of days with postoperative hoarseness was higher when atracurium was omitted (25 vs. 6 patients;P < 0.001). Similar findings were observed for vocal cord sequelae (incidence of vocal cord sequelae: 15 vs. 3 patients, respectively, P = 0.002; days with vocal cord sequelae: 50 vs. 5 patients, respectively, P < 0.001). Excellent intubating conditions were less frequently associated with postoperative hoarseness compared to good or poor conditions (11, 29, and 57% of patients, respectively; excellent vs. poor:P = 0.008). Similar findings were observed for vocal cord sequelae (11, 22, and 50% of patients, respectively; excellent vs. poor:P = 0.02).