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PubMed1992

Cardiovascular responses to insertion of the laryngeal mask.

We have compared, in 40 healthy patients, the cardiovascular responses induced by laryngoscopy and intubation with those produced by insertion of a laryngeal mask. Anaesthesia was induced with thiopentone and maintained with enflurane and nitrous oxide in oxygen; vecuronium was used for muscle relaxation. Arterial pressure was measured with a Finapres monitor. The mean maximum increase in systolic arterial pressure after laryngoscopy and tracheal intubation was 51.3% compared with 22.9% for laryngeal mask insertion (p less than 0.01). Increases in maximum heart rate were similar, (26.6% v 25.7%) although heart rate remained elevated for longer after tracheal intubation. We conclude that insertion of the laryngeal mask airway is accompanied by smaller cardiovascular responses than those after laryngoscopy and intubation and that its use may be indicated in those patients in whom a marked pressor response would be deleterious.

Adult↗
PubMed1992

Resistance and additional inspiratory work imposed by the laryngeal mask airway. A comparison with tracheal tubes.

Laryngeal mask airways and tracheal tubes were studied to determine both their resistance to constant gas flows and additional inspiratory work during simulated inspiration. Laryngeal mask airways imposed less resistance and required lower additional inspiratory work compared with the corresponding sized tracheal tubes. If inspiratory loading during anaesthesia is an important consideration, then the laryngeal mask airway may be preferable to a tracheal tube.

Airway Resistance↗
PubMed1992

The Laerdal pocket mask: effects of increasing supplementary oxygen flow.

To determine the effect of increasing supplementary oxygen flow during ventilation with the Laerdal pocket mask 24 subjects ventilated a modified recording mannikin for four 90 s periods using the mask with oxygen flows of 5 l, 10 l, 15 l and 20 l.min-1. Oxygen concentration increased and carbon dioxide concentration decreased with increasing oxygen flow. Tidal volume also increased with oxygen flow. The delivered oxygen concentrations were lower than previously reported at all four rates; however, mask function improved with increasing flow up to 20 l.

Adult↗
PubMed1992

Pre-oxygenation: the Hudson mask as an alternative technique.

The use of a simple oxygen facemask (Hudson) with high oxygen inflow (48 l.min-1) was investigated as a technique for pre-oxygenation, comparing it with the Magill system (oxygen flow: 100 ml.kg-1.min-1). One hundred and thirty-eight patients scheduled for elective gynaecological and orthopaedic surgery were studied: group 1, Hudson mask and group 2, Magill system (ASA 1-2, n = 107); group 3, Hudson mask and group 4, Magill system (ASA 3, n = 30). Pre-oxygenation was assessed by measuring the times to 97%, 95% and 93% arterial desaturation (finger pulse oximetry) following 3 min of pre-oxygenation. The times taken to achieve these end-points in all the study groups suggest that the Hudson mask offers an alternative technique for pre-oxygenation.

Adult↗
PubMed1992

Intermittent positive pressure ventilation through a laryngeal mask airway. Is a nasogastric tube useful?

A nasogastric tube was used to aspirate air insufflated into the stomach during intermittent positive pressure ventilation through a laryngeal mask airway and a tracheal tube. No difference was found in the amount aspirated between patients with a tracheal tube, a laryngeal mask airway with the nasogastric tube closed or a laryngeal mask airway with the nasogastric tube open, when the nasogastric tube was aspirated at 15 min intervals for the first hour of anaesthesia.

Adult↗
PubMed1993

A split laryngeal mask as an aid to training in fibreoptic tracheal intubation. A comparison with the Berman II intubating airway.

Thirty patients were randomly allocated to one of two groups in order to compare the use of a split laryngeal mask airway with the Berman II airway as aids to training in fibreoptic laryngoscopy. In both groups anaesthesia was induced with propofol and maintained with isoflurane in N2O/O2 (FIO2 = 0.5). The fibreoptic laryngoscope was guided towards the larynx using the split laryngeal mask airway in group 1 and the Berman airway in group 2. The tracheas of all patients were successfully intubated at the first attempt and no patient's peripheral oxygen saturation decreased below 92%. Two min after intubation mean heart rate was significantly greater in group 1 (101 beat.min-1) than in group 2 (84 beat.min-1) (P < 0.05). The split laryngeal mask is a useful aid to training in fibreoptic intubation and may allow better airway control than the Berman II intubating airway.

Adolescent↗
PubMed1994

A comparison of three types of tracheal tube for use in laryngeal mask assisted blind orotracheal intubation.

Laryngeal mask assisted blind orotracheal intubation is a technique that is best mastered under controlled circumstances. The influence of the type of tracheal tube, and positioning of the head, on the success rate of this procedure was evaluated in 90 gynaecological patients presenting for elective procedures under general anaesthesia. After induction, a laryngeal mask was introduced and its position was confirmed. Up to three attempts at blind orotracheal intubation using one of three tracheal tubes (Argyle, Portex or Kendall Curity) passed through the laryngeal mask were permitted in each patient. The success rates after a single attempt at blind oral intubation were 3.3%, 70.0% and 30.0% respectively (p < 0.001 and p < 0.05 when Portex was compared to Argyle and Kendall Curity types). After a maximum of three attempts, success rates were 30.0% (Argyle), 93.3% (Portex) and 76.7% (Kendall Curity). The first attempt at tracheal intubation was performed in the 'sniffing the morning air position' and this was successful in 52% of successful intubations; the second attempt using extension at the atlanto-occipital joint was successful in a further 35% of successful intubations; the third attempt used varying degrees of neck flexion and extension at the atlanto-occipital joint and this permitted successful placement of the tracheal tube in the remaining 13% of patients in whom tracheal intubation was possible.

Female↗
PubMed1994

Unilateral hypoglossal nerve paralysis following the use of the laryngeal mask airway.

We report a unilateral hypoglossal nerve paralysis following the use of a laryngeal mask airway in a 62-year-old woman with rheumatoid arthritis undergoing a shoulder joint replacement. Cervical epidural anaesthesia was combined with general anaesthesia using nitrous oxide administered via a laryngeal mask airway with the patient in the right lateral decubitus position. The next morning, the patient was noted to have a right hypoglossal nerve palsy. Compression of the nerve between the laryngeal mask airway cuff, distended with nitrous oxide, and the hyoid bone, was considered to be the cause of the nerve paralysis.

Constriction↗
PubMed1995

Correct positioning of the epiglottis for application of the Brain laryngeal mask airway.

Positioning of the epiglottis when the Brain laryngeal mask airway is in place was studied in 20 adult patients, using a new technique of insertion. The laryngeal mask was inserted when the anterior displacement of the mandible extended the epiglottis, thereby the providing an excellent airway in all patients. In 10 out of these 20 patients, the conventional technique of insertion revealed an incomplete extension of the epiglottis, and inadequate opening of the laryngeal inlet. It was concluded that the anterior displacement of the mandible during insertion of the laryngeal mask enhances the opening of the larynx, the result being an excellent airway.

Adolescent↗
PubMed1995

Changes in intra-ocular pressure during general anaesthesia. A comparison of spontaneous breathing through a laryngeal mask with positive pressure ventilation through a tracheal tube.

Changes in-intra-ocular pressure during spontaneous ventilation with a laryngeal mask were compared with controlled ventilation using a tracheal tube in 40 patients undergoing intra-ocular surgery under general anaesthesia. Intra-ocular pressure was measured before induction, after establishing the airway, at the end of the operation and after removal of the airway device. Anaesthesia was induced with propofol and maintained with enflurane and nitrous oxide in oxygen. Mean end-tidal carbon dioxide tension was significantly higher during spontaneous ventilation than during controlled ventilation 5 min after establishing the airway (5.7 versus 4.5) and at the end of surgery (6.1 versus 4.2) (p < 0.001). Despite this, intra-ocular pressures were lower than baseline and similar in the two groups throughout anaesthesia. At the end of surgery, intra-ocular pressure (mmHg) was 11.2 and 8.6 during spontaneous or controlled ventilation respectively. One min after removal of the device, mean intra-ocular pressure (mmHg) in the tracheal tube group (16.0) was slightly higher than baseline (15.3) and was significantly higher than the laryngeal mask group (10.9) (p < 0.01). Spontaneous ventilation with a laryngeal mask is an acceptable alternative to controlled ventilation with tracheal intubation in elective intra-ocular surgery.

Adolescent↗
PubMed1996

Optimal shape of the laryngeal mask cuff: the influence of three deflation techniques.

A randomised, single-blinded, controlled trial was conducted to determine if a new laryngeal mask deflation tool offered any advantages over manual or free deflation. Ten laryngeal mask airways were tested and the deflation tool provided a significantly superior and more consistent shape than either hand manipulation or the free deflation, but did not offer any benefits in terms of residual volume. The deflator tool should encourage wider use of the standard recommended insertion technique. It can be used as a backup when manual deflation cannot provide the correct shape and may be useful for researchers studying laryngeal mask airway placement.

Anesthesiology↗
PubMed1996

Safety and efficacy of the laryngeal mask airway. A prospective survey of 1400 children.

A survey of laryngeal mask airway usage in 1400 infants and children by ten trainee anaesthetists was undertaken to provide information about insertion and complication rates using the standard insertion technique and a limited range of standardised anaesthetic techniques. Placement was successful in 90% (1258/1400) at the first attempt, 8% (112/1400) at the second attempt and 2% (29/1400) required an alternative technique of insertion. One patient vomited during insertion and the procedure was abandoned, but aspiration did not occur. The overall problem rate was 11.5% and there were significantly more problems during induction of anaesthesia (p < 0.02). Oxygen saturation decreased below 90% briefly on 23 occasions (1.7%). The incidence of problems was unrelated to the mode of ventilation, or whether isoflurane or total intravenous anaesthesia with propofol was used for maintenance. Most problems came with use of the size 1 laryngeal mask (p < 0.001). The subspecialty with the highest problem rate was ear, nose and throat surgery (p < 0.001). There was a significant decrease in problems with increasing experience (p < 0.001). There was no major morbidity associated with use of the device. We conclude that the laryngeal mask provides a safe and effective form of airway management for infants and children in the hands of supervised anaesthesia trainees both for spontaneous and controlled ventilation using either isoflurane or total intravenous anaesthesia.

Adolescent↗
PubMed1996

The view of the glottis at laryngoscopy after unexpectedly difficult placement of the laryngeal mask.

In 12 patients to whom a non-depolarising neuromuscular relaxant had been given and in whom placement of the laryngeal mask had failed unexpectedly, the view of the larynx at laryngoscopy and the ease of tracheal intubation were examined. The glottis was only partially seen at laryngoscopy in three patients and was not seen at all in another three patients. Tracheal intubation was difficult in three of them. It would appear that in some patients both placement of the laryngeal mask and tracheal intubation are difficult. It is thus inadvisable to paralyse patients electively and rely on the laryngeal mask to secure a clear airway when tracheal intubation is predicted to be difficult.

Adult↗
PubMed1997

Ease of insertion of the laryngeal mask airway by inexperienced personnel when using an introducer.

The Portex introducer for the laryngeal mask airway was designed as an aid to successful insertion, acting as an idealised 'artificial hard palate' to guide the tip of the laryngeal mask into the correct position. A number of authors have investigated laryngeal mask insertion by unskilled personnel in certain situations, one example being nurses during in-hospital cardiopulmonary resuscitation. We investigated whether the introducer had any effect on the incidence of first-time successful LMA placement by unskilled personnel. These were nonanaesthetist doctors, randomly assigned to have one attempt at LMA insertion in an anaesthetised patient, with and without the introducer. In 44 patients with the LMA being inserted according to the manufacturer's instructions, there was a 68% success rate (14 failures). In 45 patients with the LMA being inserted with the aid of a Portex introducer, there was a 96% success rate (two failures). This was a highly significant improvement (p < 0.001).

Adolescent↗
PubMed1997

Oxygen enrichment during emergence with the laryngeal mask--the 'T-bag' versus the T-piece.

We have compared the performance of a new oxygen enrichment device, the 'T-bag', with a T-piece during emergence from spontaneous breathing anaesthesia with the laryngeal mask airway. Thirty patients were randomly allocated to each group. Inspired and end-tidal gases were sampled from the proximal end of the laryngeal mask airway. Cardiorespiratory variables were recorded immediately prior to discontinuation of anaesthesia, 2 min later and then at 5-min intervals until removal of the laryngeal mask airway. The mean inspired oxygen concentration was greater than 70% and the inspired carbon dioxide was less than 2 mmHg in both groups throughout emergence. There were no episodes of hypoxia (oxygen saturation < 92%). Both devices performed well, but the 'T-bag' offered advantages in terms of respiratory monitoring and ventilatory capability.

Adult↗
PubMed1997

Co-induction and laryngeal mask insertion. A comparison of thiopentone versus propofol.

Conditions for insertion of the laryngeal mask airway were assessed in 70 unpremedicated patients comparing the co-induction with midazolam-alfentanil-thiopentone and midazolam-alfentanil-propofol. Following pre-induction doses of midazolam 0.04 mg.kg-1 and alfentanil 10 micrograms.kg-1, patients received equipotent doses of either thiopentone or propofol. Whilst jaw relaxation and ease of laryngeal mask insertion were similar between the two groups, patients receiving propofol were less likely to have undesired responses requiring additional boluses of induction agent (p < 0.05). We conclude that, using these doses, propofol is superior to thiopentone for laryngeal mask airway insertion when using a co-induction technique.

Adolescent↗
PubMed2004

A comparison of the intubating laryngeal mask airway and the Bonfils intubation fibrescope in patients with predicted difficult airways.

Tracheal intubation with the intubating laryngeal mask airway or the Bonfils intubation fibrescope was performed in 80 patients with predicted difficult airways. Mallampati score, thyromental distance, mouth opening and mobility of the atlanto-occipital joint were used to predict difficult airways. The overall success rate, time to the first adequate lung ventilation and time taken for the successful placement of the tracheal tube were recorded, as well as a subjective assessment of the handling of the device and the incidence of postoperative sore throat and hoarseness. The median [range] time to the first adequate ventilation was significantly shorter with the intubating laryngeal mask airway than with the Bonfils intubation fibrescope (28 [6-85] s vs. 40 [23-77] s, p < 0.005). Tracheal intubation was significantly slower with the intubating laryngeal mask airway than with the Bonfils intubation fibrescope (76 [45-155] s vs. 40 [23-77] s, p < 0.0001. Patients in the Bonfils group suffered less sore throat and hoarseness than those in the other group.

Adolescent↗
PubMed2006

Awake insertion of the laryngeal mask airway using topical lidocaine and intravenous remifentanil.

We assessed the use of intravenous remifentanil for the insertion of the laryngeal mask airway in 10 healthy awake volunteers, a technique primarily developed to facilitate functional magnetic resonance imaging studies of anaesthesia. Each volunteer received 200 microg glycopyrronium intravenously. Topical airway anaesthesia was effected by 4 ml nebulised lidocaine 4%, followed by 12 sprays of lidocaine 10%. Remifentanil was subsequently infused to achieve an initial target effect-site concentration of 2 ng.ml(-1); increments of 1 ng.ml(-1) were allowed with the maximum effect-site concentration limited to 6 ng.ml(-1). Insertion of the laryngeal mask airway was successful on the first attempt in all cases. The median (IQR [range]) target effect-site remifentanil concentration at insertion was 2.5 (2-3 [2-4]) ng.ml(-1). All volunteers were co-operative during the procedure and only one reported discomfort. Sore throat was a complication in all volunteers. We conclude that the technique allows successful insertion of the laryngeal mask airway in healthy awake volunteers under conditions that were safe and reproducible.

Adult↗