Hartmut Ocker

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.

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.

Airway management during cardiopulmonary resuscitation--a comparative study of bag-valve-mask, laryngeal mask airway and combitube in a bench model.

Gastric inflation and subsequent regurgitation are a potential risk of ventilation during cardiopulmonary resuscitation (CPR). In respect of recent investigations, principal respiratory components such as respiratory system compliance, resistance and lower esophageal sphincter pressure were adapted according to CPR situations. The purpose of our study was to assess lung ventilation and gastric inflation when performing ventilation with bag-valve-mask, laryngeal mask airway, and combitube in a bench model simulating an unintubated cardiac arrest patient. Twenty-one student nurses, without any experience in basic life support measures, ventilated the bench model with all three devices. Mean ( +/- S.D.) gastric inflation with the laryngeal mask airway (seven cases) was significantly lower than with the bag-valve-mask (0.6 +/- 0.8 vs 3.0 +/- 2.11 min(-1), P < 0.01). There was no gastric inflation when ventilation was performed with the combitube. Only seven of 21 volunteers exceeded 1-min lung volumes of > 5 1 when using the bag-valve-mask, whereas mean (+/-S.D.) 1-min lung volumes with both laryngeal mask airway and combitube were significantly higher (laryngeal mask airway 15.0+/-6.61, combitube 16.6 +/- 6.81 vs bag-valve-mask 4.8 +/- 2.71, P < 0.01). The time for insertion was significantly faster with both bag-valve-mask and laryngeal mask airway compared with the combitube (median: bag valve mask 22 s, laryngeal mask airway 37 s vs combitube 70 s, P < 0.01). This may tip the scales towards using the laryngeal mask airway during basic life support airway management. In conclusion, our data suggests that both laryngeal mask airway and combitube may be appropriate alternatives for airway management in the first few minutes of CPR.

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.

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

Smaller tidal volumes during cardiopulmonary resuscitation: comparison of adult and paediatric self-inflatable bags with three different ventilatory devices

Gastric inflation and subsequent regurgitation of stomach contents is a major hazard of bag-valve-face mask ventilation during the basic life support phase of cardiopulmonary resuscitation (CPR). Recent investigations suggested that use of a paediatric self-inflating bag may reduce stomach inflation while ensuring sufficient lung ventilation. The purpose of our study was to examine whether use of a paediatric self-inflating bag in association with laryngeal mask airway, combitube, and bag-valve-face mask may provide adequate lung ventilation, while reducing the risk of gastric inflation in a bench model simulating the initial phase of CPR. Sixteen intensive care unit registered nurses volunteered for our study. Use of a paediatric versus adult self-inflating bag resulted in a significantly (P < 0.01) lower mean (+/- S.D.) tidal lung volume with both the laryngeal mask airway and combitube (laryngeal mask airway 349 +/- 149 ml versus 725 +/- 266 ml, combitube 389 +/- 113 ml versus 1061 +/- 451 ml). Lung tidal volumes were below the European Resuscitation Council recommendation with both self-inflatable bags in the bag-valve-face mask group (paediatric versus adult self-inflatable bag 256 +/- 77 ml versus 334 +/- 125 ml). Esophageal tidal volumes were significantly (P < 0.05) lower using the paediatric self-inflatable bag in the bag-valve-face mask group; almost no gastric inflation occurred with the laryngeal mask airway, and none with the combitube. In conclusion, use of the paediatric self-inflating bag may reduce gastric inflation, but measured lung tidal volumes are below the European Resuscitation Council recommendation when used with either, the laryngeal mask airway, combitube, or bag-valve-face mask.

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.

Effectiveness of various airway management techniques in a bench model simulating a cardiac arrest patient.

The purpose of this study was to assess the levels of lung and gastric tidal volumes paramedics achieve when performing ventilation with bag-valve-mask, laryngeal mask, and Combitube. Twenty paramedics performed ventilation with a bag-valve mask, laryngeal mask, and Combitube in a bench model simulating an unintubated cardiorespiratory arrest patient. Lung and gastric tidal volumes and lung and gastric peak airway pressures were subsequently measured. The results showed that mean +/- SEM lung tidal volumes were significantly higher with the laryngeal mask and Combitube compared to the bag-valve-mask (701 +/- 264 vs. 742 +/- 311 vs. 353 +/- 110 mL, respectively). No gastric inflation occurred with the Combitube; gastric inflation was significantly lower with the laryngeal mask compared to the bag-valve-mask (25 +/- 15 vs. 230 +/- 25 mL, respectively). Both the laryngeal mask and Combitube proved to be valid alternatives for bag-valve-mask ventilation in our bench model simulating an unintubated patient with cardiorespiratory arrest.

Intubating laryngeal mask airway, laryngeal tube, 1100 ml self-inflating bag-alternatives for basic life support?

Insufficient oxygenation, ventilation and gastric inflation with subsequent regurgitation of stomach contents is a major hazard of bag-valve-face mask ventilation during the basic life support phase of cardiopulmonary resuscitation (CPR). The European Resuscitation Council has recommended smaller tidal volumes of approximately 500 ml as an effort to reduce gastric inflation; furthermore, the intubating laryngeal mask airway and the laryngeal tube have been recently developed in order to provide rapid ventilation and to secure the airway. The purpose of our study was to examine whether usage of a newly developed medium-size self-inflating bag (maximum volume, 1100 ml) in association with the intubating laryngeal mask airway, and laryngeal tube may provide adequate lung ventilation, while reducing the risk of gastric inflation in a bench model simulating the initial phase of CPR. Twenty house officers volunteered for our study. When using the laryngeal tube, and the intubating laryngeal mask airway, respectively, the medium-size (maximum volume, 1100 ml) versus adult (maximum volume, 1500 ml) self-inflating bag resulted in significantly (P<0.05) lower mean+/-S.E.M. lung tidal volumes (605+/-22 vs. 832+/-4 ml, and 666+/-27 vs. 887+/-37 ml, respectively), but comparable peak airway pressures. No gastric inflation occurred when using both devices with either ventilation bag. In conclusion, both the intubating laryngeal mask airway and laryngeal tube in combination with both an 1100 and 1500 ml maximum volume self inflating bag proved to be valid alternatives for emergency airway management in a bench model of a simulated unintubated cardiac arrest victim.