Volker Dörges

The laryngeal tube: a new simple airway device.

T he face mask, laryngeal mask, and the Combitube (Tyco Healthcare/Sheridan, Argyle, NY) are devices commonly used to ventilate the lungs of nonintubated patients (1,2), but some disadvantages may result in inadvertent ventilation-associated complications. For example, the face mask is associated with large dead space ventilation, leakage, and gastric inflation (3). In contrast, the laryngeal mask is an alternative airway adjunct that is simple to use, resulting in both minimal dead space ventilation and gastric inflation (4,5). Nevertheless, a possible limiting feature of the laryngeal mask may be the risk of aspirating gastric contents (6) because fiberoptic studies have found 6%–9% visualization of the esophagus (7,8). Although the Combitube was developed as an alternative to endotracheal intubation to secure the airway in an emergency setting, its complex structure requires extensive instruction and training to ensure correct placement within an acceptable time (9). The purpose of this study was to assess whether the newly developed Laryngeal Tube (VBM Medizintechnik GmbH, Sulz, Germany), somewhat a single-lumen, shortened Combitube, can provide sufficient ventilation and adequate oxygenation in patients undergoing routine induction of anesthesia.

Management of the predicted difficult airway: a comparison of conventional blade laryngoscopy with video-assisted blade laryngoscopy and the GlideScope

Background and objective We investigated whether the use of two different video laryngoscopes [direct-coupled interface (DCI) video laryngoscope and GlideScope] may improve laryngoscopic view and intubation success compared with the conventional direct Macintosh laryngoscope (direct laryngoscopy) in patients with a predicted difficult airway. Methods One hundred and twenty adult patients undergoing elective minor surgery requiring general anaesthesia and endotracheal intubation presenting with at least one predictor for a difficult airway were enrolled after Institutional Review Board approval and written informed consent was obtained. Repeated laryngoscopy was performed using direct laryngoscope, DCI laryngoscope and GlideScope in a randomized sequence before patients were intubated. Results Both video laryngoscopes showed significantly better laryngoscopic view (according to Cormack and Lehane classification as modified by Yentis and Lee = C&L) than direct laryngoscope. Laryngoscopic view C&L ≥ III was measured in 30% of patients when using direct laryngoscopy, and in only 11% when using the DCI laryngoscope (P < 0.001). The GlideScope enabled significantly better laryngoscopic view (C&L ≥ III: 1.6%) than both direct (P < 0.001) and DCI laryngoscopes (P < 0.05). Clinically relevant improvement in the specific 36 patients with insufficient direct view (C&L ≥ III) could be achieved significantly more often with the GlideScope (94.4%) than with the DCI laryngoscope (63.8%; P < 0.01). Laryngoscopy time did not differ between instruments [median (range): direct laryngoscope, 13 (5–33) s; DCI laryngoscope, 14 (6–40) s; GlideScope, 13 (5–34) s]. In contrast, tracheal intubation needed significantly more time with both video laryngoscopes [DCI laryngoscope, 27 (17–94) s, P < 0.05 and GlideScope, 33 (18–68) s, P < 0.01] than with the direct laryngoscope [22.5 (12–49) s]. Intubation failed in four cases (10%) using the direct laryngoscope and in one case (2.5%) each using the DCI laryngoscope and the GlideScope. Conclusion We conclude that the video laryngoscope and GlideScope in particular may be useful instruments in the management of the predicted difficult airway.

Effects of smaller tidal volumes during basic life support ventilation in patients with respiratory arrest: good ventilation, less risk?

OBJECTIVE When ventilating an unintubated patient in cardiac or respiratory arrest, smaller tidal volumes of 500 ml instead of 800-1200 ml may be beneficial to decrease peak airway pressure, and to minimise stomach inflation. The purpose was to determine the effects of small (approximately 500 ml) versus large (approximately 1000 ml) tidal volumes given with paediatric versus adult self-inflatable bags and approximately 50% oxygen on respiratory parameters in patients during simulated basic life support ventilation. METHODS While undergoing induction of anaesthesia, patients were randomised to three minutes of ventilation with either an adult (n = 40) or paediatric (n = 40) self-inflatable bag. RESULTS When compared with an adult self-inflatable bag, the paediatric bag resulted in significantly lower mean (+/- standard deviation) exhaled tidal volume (365 +/- 55 versus 779 +/- 122 ml; P < 0.0001), peak airway pressure (20 +/- 2 versus 25 +/- 5 cm H2O; P < 0.0001), but comparable oxygen saturation (97 +/- 1% versus 98 +/- 1%; NS (nonsignificant)). Stomach inflation occurred in five of 40 patients ventilated with an adult self-inflatable bag, but in no patients who were ventilated with a paediatric self-inflatable bag (P = 0.054). CONCLUSION Administering smaller tidal volumes with a paediatric instead of an adult self-inflatable bag in unintubated adult patients with respiratory arrest maintains good oxygenation and carbon dioxide elimination while decreasing peak airway pressure, which makes stomach inflation less likely.

The respiratory system during resuscitation: a review of the history, risk of infection during assisted ventilation, respiratory mechanics, and ventilation strategies for patients with an unprotected airway

The fear of acquiring infectious diseases has resulted in reluctance among healthcare professionals and the lay public to perform mouth-to-mouth ventilation. However, the benefit of basic life support for a patient in cardiopulmonary or respiratory arrest greatly outweighs the risk for secondary infection in the rescuer or the patient. The distribution of ventilation volume between lungs and stomach in the unprotected airway depends on patient variables such as lower oesophageal sphincter pressure, airway resistance and respiratory system compliance, and the technique applied while performing basic or advanced airway support, such as head position, inflation flow rate and time, which determine upper airway pressure. The combination of these variables determines gas distribution between the lungs and the oesophagus and subsequently, the stomach. During bag-valve-mask ventilation of patients in respiratory or cardiac arrest with oxygen supplementation (> or = 40% oxygen), a tidal volume of 6-7 ml kg(-1) ( approximately 500 ml) given over 1-2 s until the chest rises is recommended. For bag-valve-mask ventilation with room-air, a tidal volume of 10 ml kg(-1) (700-1000 ml) in an adult given over 2 s until the chest rises clearly is recommended. During mouth-to-mouth ventilation, a breath over 2 s sufficient to make the chest rise clearly (a tidal volume of approximately 10 ml kg(-1) approximately 700-1000 ml in an adult) is recommended.

A Comparison of the Laryngeal Tube with the Laryngeal Mask Airway During Routine Surgical Procedures

The laryngeal mask airway (LMA; Laryngeal Mask Company, Henley-on-Thames, UK) is an established airway device, whereas the laryngeal tube (LT) is relatively new and therefore not as well investigated. Therefore, the purpose of the present prospective, randomized, controlled trial was to compare the LT with the LMA in routine clinical practice. In 50 patients undergoing general anesthesia for minor routine surgery, standardized anesthesia was induced and maintained with alfentanil and propofol. Patients were randomized to controlled ventilation (fraction of inspired oxygen = 0.4; fraction of inspired nitrous oxide = 0.6; tidal volume = 7 mL/kg; respiratory rate = 10 breaths/min) with the LT (n = 25) or the LMA (n = 25). Oxygen saturation was recorded before the induction of anesthesia and after the administration of oxygen. After 2 and 10 min of ventilation with the LT or LMA, oxygen saturation, end-expiratory carbon dioxide, expiratory tidal volume, and peak airway pressure were recorded. Capillary blood gas samples were taken before the induction of anesthesia and after 10 min of ventilation. Time of insertion and airway leak pressure of each device were measured. The time of insertion was comparable with both devices (LT versus LMA, median 21 s versus 19 s;P = not significant). Blood gas samples and ventilation variables revealed sufficient ventilation and oxygenation with either device (P = not significant). Peak airway pressure (LT, 17 ± 3 cm H2O; LMA, 15 ± 3 cm H2O) and airway leak pressure (LT, 36 ± 3 cm H2O; LMA, 22 ± 3 cm H2O) were significantly (P < 0.05) higher when using the LT compared with the LMA. In conclusion, using the LT and LMA resulted in comparable ventilation and oxygenation variables in this model of ASA physical status I and II patients undergoing routine surgical procedures. The newly developed LT may be a simple alternative device to secure the airway.

Smaller tidal volumes with room-air are not sufficient to ensure adequate oxygenation during bag–valve–mask ventilation☆

The European Resuscitation Council has recommended decreasing tidal volume during basic life support ventilation from 800 to 1200 ml, as recommended by the American Heart Association, to 500 ml in order to minimise stomach inflation. However, if oxygen is not available at the scene of an emergency, and small tidal volumes are given during basic life support ventilation with a paediatric self-inflatable bag and room-air (21% oxygen), insufficient oxygenation and/or inadequate ventilation may result. When apnoea occurred after induction of anaesthesia, 40 patients were randomly allocated to room-air ventilation with either an adult (maximum volume, 1500 ml) or paediatric (maximum volume, 700 ml) self-inflatable bag for 5 min before intubation. When using an adult (n=20) versus paediatric (n=20) self-inflatable bag, mean +/-SEM tidal volumes and tidal volumes per kilogram were significantly (P<0.0001) larger (719+/-22 vs. 455+/-23 ml and 10.5+/-0.4 vs. 6.2+/-0.4 ml kg(-1), respectively). Compared with an adult self-inflatable bag, bag-valve-mask ventilation with room-air using a paediatric self-inflatable bag resulted in significantly (P<0.01) lower paO(2) values (73+/-4 vs. 87+/-4 mmHg), but comparable carbon dioxide elimination (40+/-2 vs. 37+/-1 mmHg; NS). In conclusion, our results indicate that smaller tidal volumes of approximately 6 ml kg(-1) ( approximately 500 ml) given with a paediatric self-inflatable bag and room-air maintain adequate carbon dioxide elimination, but do not result in sufficient oxygenation during bag-valve-mask ventilation. Thus, if small (6 ml kg(-1)) tidal volumes are being used during bag-valve-mask ventilation, additional oxygen is necessary. Accordingly, when additional oxygen during bag-valve-mask ventilation is not available, only large tidal volumes of approximately 11 ml kg(-1) were able to maintain both sufficient oxygenation and carbon dioxide elimination.

Comparison of different airway management strategies to ventilate apneic, nonpreoxygenated patients.

ObjectiveEndotracheal intubation is the gold standard for providing emergency ventilation, but acquiring and maintaining intubation skills may be difficult. Recent reports indicate that even in urban emergency medical services with a high call volume, esophageal intubations were observed, requiring either perfect intubation skills or development of alternatives for emergency ventilation. DesignSimulated emergency ventilation in apneic patients employing four different airway devices that used small tidal volumes. SettingUniversity hospital operating room. SubjectsForty-eight ASA I/II patients who signed written informed consent before being enrolled into the study. InterventionsIn healthy adult patients without underlying respiratory or cardiac disease who were breathing room air before undergoing routine induction of surgery, 12 experienced professional paramedics inserted either a laryngeal mask airway (n = 12), Combitube (n = 12), or cuffed oropharyngeal airway (n = 12) or placed a face mask (n = 12) before providing ventilation with a pediatric (maximum volume, 700 mL) self-inflating bag with 100% oxygen for 3 mins. Measurements and Main ResultsIn three of 12 cuffed oropharyngeal airway patients, two of 12 laryngeal mask airway patients, and one of 12 Combitube patients, oxygen saturation fell below 90% during airway device insertion, and the experiment was terminated; no oxygenation failures occurred with the bag-valve-mask. Oxygen saturation decreased significantly (p < .05) during insertion of the Combitube and laryngeal mask but not with the bag-valve-mask and cuffed oropharyngeal airway; however, oxygen saturation increased after 1 min of ventilation with 100% oxygen. No differences in tidal lung volumes were observed between airway devices. ConclusionsParamedics were able to employ the laryngeal mask airway, Combitube, and cuffed oropharyngeal airway in apneic patients with normal lung compliance and airways. In this population, bag-valve-mask ventilation was the most simple and successful strategy. Small tidal volumes applied with a pediatric self-inflating bag and 100% oxygen resulted in adequate oxygenation and ventilation.

The Laryngeal Tube S: a modified simple airway device.

T he recently introduced single-lumen Laryngeal Tube can be inserted without additional equipment, and was proven in bench models (1,2) and preliminary clinical trials, to effectively ventilate and oxygenate patients with respiratory arrest (3,4) undergoing routine induction of anesthesia. Thus, the Laryngeal Tube may be used as an alternative airway device during either routine or emergency airway management. Handling of the Laryngeal Tube was later simplified by blocking two cuffs with one catheter instead of two. This procedure secures inflation of the oropharyngeal cuff first, and then of the esophageal cuff because of the different resistance characteristics of the connected tubing. Unfortunately, because of the design of the Laryngeal Tube, it may not be the best airway device for spontaneously breathing patients (5). As discussed earlier, a second disadvantage of the Laryngeal Tube may be the blind ending in the esophageal inlet, which may provoke esophageal rupture in the case of vomiting (3). Accordingly, the Laryngeal Tube was fitted with a second lumen serving for suctioning and free gastric drainage (Laryngeal Tube S [LTS]), but not for ventilation, as with the Combitube. In the present study, our purpose was to assess whether the LTS could provide sufficient ventilation and adequate oxygenation in patients undergoing routine induction of anesthesia for minor surgery. Methods

A comparison of the proseal laryngeal mask airway, the laryngeal tube S and the oesophageal-tracheal combitube during routine surgical procedures.

Background and objective: This study was performed to compare three supraglottic airway devices: the ProSeal laryngeal mask airway (PLMA), the laryngeal tube S (LTS) and the oesophageal‐tracheal combitube (OTC) during routine surgical procedures. Methods: Ninety American Society of Anesthesiologists (ASA) I‐III patients scheduled for routine minor obstetric surgery were randomly allocated to the PLMA (n = 30), the LTS (n = 30) or the OTC (n = 30) group, respectively. The overall success rate, insertion time, cuff pressures and resulting airway leak pressures were determined as well as a subjective assessment of handling and the incidence of sore throat, dysphagia and hoarseness were performed. Results: Insertion time until the first adequate ventilation was significantly (P < 0.0001) shorter in the PLMA (median 29 s; 25‐75th percentile 25‐48 s; range 10‐161 s; success rate 100%) and in the LTS group (38 s; 30‐44 s; 13‐180 s; 100%) compared to the OTC group (75 s; 48‐98 s; 35‐180 s; 90%). In vivo cuff pressures and airway leak pressures increased with the inflating cuff volume in all devices and were highest in the OTC group. Postoperatively, patients in the PLMA and the LTS group complained significantly less about sore throat (P < 0.001 and 0.05) and dysphagia (P < 0.001 and 0.02) compared to the OTC group, while there was no difference regarding the incidence of hoarseness. Subjective assessment of handling was comparable with the PLMA and the LTS, but inferior with the OTC. Conclusions: In conclusion, both PLMA and LTS proved to be suitable for routine surgical procedures and proved to be superior to the OTC which cannot be recommended for routine use.

Optimisation of tidal volumes given with self-inflatable bags without additional oxygen

The European Resuscitation Council has recommended smaller tidal volumes of 500 ml during basic life support ventilation in order to minimise gastric inflation. One method of delivering these tidal volumes may be to use paediatric instead of adult self-inflatable bags; however, we have demonstrated in other studies that only 350 ml may be delivered, using this technique. The reduced risk of gastric inflation was offset by oxygenation problems, rendering the strategy of attempting to deliver tidal volumes of 500 ml with a paediatric self-inflatable bag questionable, at least when using room-air. In this report, we assessed the effects of a self-inflatable bag with a size between the maximum size of a paediatric (700 ml) and an adult (1500 ml) self-inflatable bag on respiratory variables and blood gases during bag-valve-mask ventilation. After induction of anaesthesia, 50 patients were block-randomised into two groups of 25 each. They were ventilated with room-air with either an adult (maximum volume, 1500 ml) or a newly developed medium-size (maximum volume, 1100 ml; Dräger, Lübeck, Germany) self-inflatable bag for 5 min before intubation. When compared with the adult self-inflatable bag, the medium-size bag resulted in significantly lower exhaled tidal volumes and tidal volumes per kg bodyweight (624 + 24 versus 738 +/- 20 ml, and 8.5 +/- 0.3 versus 10.7 +/- 0.3 ml kg(-1), respectively; P < 0.001), oxygen saturation (95 +/- 0.4 versus 96 +/- 0.3%; P < 0.05), and partial pressure of oxygen (78 +/- 3 versus 87 +/- 3 mmHg; P < 0.05). Carbon dioxide levels were comparable (37 +/- 1 versus 37 +/- 1 mmHg). Our results indicate that smaller tidal volumes of about 8 ml x kg(-1) (approximately 600 ml), given with a new medium-size self-inflatable bag and room-air, maintained adequate carbon dioxide elimination and oxygenation during bag-valve-mask ventilation. Accordingly, the new medium-size self-inflatable bag may combine both adequate ventilatory support and reduced risk of gastric inflation during bag-valve-mask ventilation.