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Biomedical subjects

P Charters

Publications and source records attributed to P Charters.

At least 19 recordsLinked to original sources
PubMed2006

A randomised, crossover study of the Dorges, McCoy and Macintosh laryngoscope blades in a simulated difficult intubation scenario.

The use of alternative adult laryngoscope blades in an unexpected difficult intubation was evaluated with a human patient simulator manikin. Twenty anaesthetists of varying experience attempted to intubate the trachea of a high fidelity simulator in both its normal and difficult intubation settings using Macintosh, Dorges and McCoy laryngoscopes in a randomised order. The time taken to intubate, Cormack and Lehane scores, percentage of glottic opening visible, failure rate, number of attempts and subjective ease of use were recorded. The Dorges and McCoy blades did not perform any better than the standard Macintosh blade in either the easy or difficult tracheal intubation settings. Guidelines recommending the use of an alternative blade in an unexpected difficult intubation scenario have limited supporting evidence. This study does not support this recommendation.

Cross-Over Studies↗
PubMed2006

Acoustic parameters of snoring sound to compare natural snores with snores during 'steady-state' propofol sedation.

OBJECTIVES: To investigate the acoustic similarity between natural and sedation-induced snores. DESIGN: Prospective observational study. SETTING: University Hospital Aintree, Liverpool, UK. PARTICIPANTS: Twenty-one patients, who had already had overnight snore recordings, completed a pre-operative sleep nasendoscopic examination. Endoscopic examination of the upper aero-digestive tract was performed at sequentially increasing, steady-state sedation levels, using intravenous propofol administered according to a weight/time-based algorithm to predict blood and effect site (tissue) concentrations. At each sedation level at which snoring occurred, snoring sound was recorded. From these samples, snore files, comprising the inspiratory sound of each snore were created. Similarly, from natural snores recorded pre-operatively, snore files, comprising the inspiratory sounds of the first 100 snores with the patient sleeping in a supine position, were also created. MAIN OUTCOME MEASURES: Snore duration (s), loudness (dBA), periodicity (%) and energy ratios for the frequency sub-bands 0-200, 0-250 and 0-400 Hz. RESULTS: Snore loudness increased significantly (P < 0.0001), whilst energy ratios for frequency bands 0-200, 0-250 and 0-400 Hz all decreased significantly as sedation level increased (P < 0.001). A significant difference between natural snoring and snoring induced at the lowest sedation level was shown (P < 0.0001). Endoscopic examination was not tolerated at this sedation level. CONCLUSIONS: The acoustic characteristics of sedation-induced and natural snores are sufficiently different to recommend the need for further research to determine whether the technique of sleep nasendoscopy is, in fact, a valid predictor of outcome of snoring surgery.

Acoustics↗
PubMed2005

Survival after massive bleeding into the airway in a patient at risk from "can't intubate, can't ventilate".

A patient survived massive bleeding into the airway due to blowout of the right internal jugular vein associated with a failed free-flap graft for pharyngeal malignancy. A recently decannulated "covering tracheostomy" could not be easily re-established. Direct laryngoscopy and mask ventilation were inappropriate because the pharyngeal mucosal wound opened spontaneously and progressively and bleeding was dramatic. Positive pressure ventilation via a facemask risked widespread surgical emphysema and further wound disruption and because bleeding was from the internal jugular vein, there would also have been a risk of air embolism. The clinical situation evolved rapidly so time management and consideration of hierarchy of mortality risks was critical. It was eventually possible to re-establish the previous tracheostomy site as a result of close co-operation between the surgical and anaesthetic teams. In difficult intubation where the problems are anticipated, the notion of responsive contingency planning is suggested to be of more general relevance than the current standard of considering alternative fallback options. The limitations of conventional capnography in this situation are also noteworthy.

Contraindications↗
PubMed2003

A clinical evaluation of the Bonfils Intubation Fibrescope.

The Bonfils Intubation Fibrescope is a rigid optical instrument for performing orotracheal intubation. We describe its introduction into our clinical practice in 60 patients with normal airways who required orotracheal intubation for elective surgery. Two anaesthetists each performed 30 attempts to intubate, in turn, in patients who received a standard general anaesthetic with neuromuscular blockade. Intubation was successful in 59 out of 60 cases. The median (IQR [range]) time to intubation was 33 s (24-50 [13-180] s). Median (IQR [range]) verbal rating score for difficulty was 2 (1-3 [0-10]). There was a significant correlation between the intubation times and the verbal rating score (p < 0.01). There was evidence of airway trauma in the single patient in whom intubation failed. The Bonfils Intubation Fibrescope is an effective instrument for orotracheal intubation in normal subjects.

Adult↗
PubMed2001

A biomechanical model of the upper airways for simulating laryngoscopy.

This paper describes a three-dimensional finite element model of the human upper airways during rigid laryngoscopy. In this procedure, an anaesthetist uses a rigid blade to displace and compress the tongue of the patient, and then inserts a tube into the larynx to allow controlled ventilation of the lungs during an operation. A realistic model of the main biomechanical aspects involved would help anaesthetists in training and in predicting difficult cases in advance. For this purpose, the finite element method was used to model structures such as the tongue, ligaments, larynx, vocal cords, bony landmarks, laryngoscope blade, and their inter-relationships, based on data extracted from X-ray, MRI, and photographic records. The model has been used to investigate how the tongue tissue behaves in response to the insertion of the laryngoscope blade, when it is subjected to a variety of loading conditions. In particular, the mechanical behaviour of the soft tissue of the tongue was simulated, from simple linear elastic material to complex non-linear viscoelastic material. The results show that, within a specific set of tongue material parameters, the simulated outcome can be successfully related to the view of the vocal cords achieved during real laryngoscopies on normal subjects, and on artificially induced difficult laryngoscopy, created by extending the upper incisors teeth experimentally.

Biomechanical Phenomena↗
PubMed2000

Severe carbon monoxide poisoning: outcome after hyperbaric oxygen therapy.

This paper reports the outcome after carbon monoxide poisoning in 31 consecutive patients treated with mechanical ventilation and hyperbaric oxygen therapy, compared with another study of mechanically ventilated patients treated with normobaric oxygen. We found 16.1% hospital mortality and 3.8% severe short-term memory loss, compared with 30% hospital mortality and 20% incidence of serious neurological deficit after treatment with normobaric oxygen; outcome was poor in 19.4% and 44.3% of those treated with hyperbaric and normobaric oxygen, respectively (P < 0.05). Cerebral oedema caused three of five deaths despite hyperbaric therapy, occurring at 24-48 h after poisoning. Intracranial pressure monitoring and CT scan of the head before wakening should be considered in any severely poisoned patient.

Adolescent↗
PubMed1999

The 'dedicated airway': a review of the concept and an update of current practice.

The term 'dedicated airway' was first used in connection with nasal fibreoptic intubations using the cuffed nasopharyngeal airway. Since that time, the concept has developed and the term has been extended to include fibreoptic intubation techniques involving both the laryngeal mask airway and cuffed oropharyngeal airway. 'Dedicated airway' can now be defined as: 'An upper airway device dedicated to the maintenance of airway patency while other major airway interventions are anticipated or are in progress. The device should be compatible with spontaneous and controlled ventilation. 'Dedicated airway techniques allow planned fibreoptic intubations in difficult cases and provide an emergency airway option in an unexpected difficult intubation when the alternative may be to wake the patient. As well as promoting safe conditions for training fibreoptic intubation in general, there is the particular advantage of being able to train using these techniques in patients known to be difficult to intubate. The authors' evolved clinical experiences in promoting the concept and the relevant literature are reviewed.

Fiber Optic Technology↗
PubMed1998

Monoclonal antibodies against vascular endothelial antigens expressed in normal human brain.

A panel of monoclonal antibodies reactive with human-brain vessels was raised by immunizing BALB/c mice with homogenate of whole human brain, obtained from temporal lobectomies. Hybridoma supernates were screened by immunohistochemical methods on frozen sections of human brain, liver and spleen and 16 clones were isolated. The pattern of immunoreactivity varied with respect to the type of brain blood vessels predominantly labelled and to tissue specificity. Some antibodies cross-reacted with cow or squirrel monkey forebrain microvessels with an intensity equal to that shown by human brain. The immunoreactivity patterns reflected antigenic heterogeneity among different subsets of vascular endothelial cells in human brain.

Animals↗
PubMed1998

Fibreoptic intubation using the cuffed oropharyngeal airway and Aintree intubation catheter.

A cuffed oropharyngeal airway has recently been introduced which has larger internal dimensions than a comparable Guedel airway. This allows a ventilation/exchange bougie, the Aintree Intubation Catheter, mounted on a fibreoptic laryngoscope to pass through it. Its 15-mm connector and pharyngeal cuff suggested the possibility of using a Rüsch sealed-port angle piece to allow ventilation through the oropharyngeal airway during fibreoptic laryngoscopy. This study investigated using this equipment to intubate the trachea through the cuffed oropharyngeal airway in paralysed patients, whilst maintaining ventilation manually with a Bain system. In 20 patients, airway control was satisfactory throughout and tracheal intubation was accomplished without complications. The cuffed oropharyngeal airway was easy to manipulate to improve a suboptimal fibreoptic view of the larynx. This may give it an advantage over the laryngeal mask airway when used as a ventilation/intubation conduit.

Adolescent↗
PubMed1996

A ventilation-exchange bougie for fibreoptic intubations with the laryngeal mask airway.

The ventilation-exchange bougie is a new airway device which can be mounted on a fibreoptic laryngoscope for passage through the larynx into the trachea via a laryngeal mask airway. Subsequent removal of the fibreoptic laryngoscope and laryngeal mask airway allows a tracheal tube to be railroaded into position over the ventilation-exchange bougie. This study described the use of this technique for elective tracheal intubation in two groups of 12 subjects in whom difficulty with intubation was not expected. All the subjects were successfully intubated by one of two anaesthetists, one experienced and the other inexperienced with fibreoptic intubation techniques. Neither had had prior experience with the ventilation-exchange bougie. Because ventilation was maintained throughout the procedure, intubation did not need to be hurried. Cusum analysis confirmed the impression of a learning curve and the technique could be considered learnt after four and six intubations for the experienced and inexperienced fibreoptic laryngoscopists respectively. No difficulty was found either in intubating the larynx with the fibreoptic laryngoscope and ventilation-exchange bougie or when railroading the tracheal tube over the ventilation-exchange bougie. It is suggested that this new device could have an important role in teaching fibreoptic techniques, management of the difficult airway and failed intubations.

Adult↗
PubMed1995

Acute airway obstruction due to ruptured aneurysmal arterio-venous fistula: common carotid artery to internal jugular vein.

Fistulae between major vessels in the head and neck are uncommon. In both civilian and wartime reports, the total number of traumatic arterio-venous fistulae in head and neck region account for less than four per cent of all arterial injuries. Fourteen cases of congenital communication between the external carotid artery and external or internal jugular vein have been reported. We report and discuss the management of a case of ruptured carotico-jugular fistula secondary to infection which presented as acute upper airway obstruction. This appears to be the first description of such a case in the literature.

Aged↗
PubMed1994

Analysis of mathematical model for osseous factors in difficult intubation.

A two-dimensional model of the factors relevant to difficult laryngoscopy was analysed mathematically to determine clinical implications and limitations. The model describes the space into which the "inevitable residual volume" of the tongue (that part remaining anterior to the blade at laryngoscopy) can be displaced to permit a view of the larynx. Four points are used: the tip of the upper incisors; a point on the anterior airway just above the larynx; the mid-point between the mandibular condyles and the internal mid-point of the symphysis. The number, F, was defined by a formula developed from their spacial relationships. Decreasing F values imply an increasing likelihood of difficult laryngoscopy. The analysis investigated the effects of: translation of individual points; plotting individual point positions for specified F-values; translating adjacent pairs of points; treating any three points as a triangle which rotates about each of its apices; and lastly, translating three points independently. During manipulations the model behaved well mathematically. Single point analysis implied that jaw recession and a non-protruding mandible were comparable in effect. Closing the mouth around the laryngoscope blade maximised F-values. Prominence of the maxilla required greater forward displacement than backward movement of the symphysis for equivalent F-value change. One particular triangular rotation suggested an entirely novel mechanism for difficulty (the "hi-slung mandible") where the condyles are positioned more rostral than normal. An otherwise normal jaw with this configuration recedes markedly on opening. Further studies are required to validate the model. Accurate quantification of individual factors in difficult laryngoscopy may then be feasible.

Adult↗
PubMed1994

Cuffed nasopharyngeal tube as 'dedicated airway' in difficult intubation.

A cuffed nasopharyngeal airway was used in five cases of difficult intubation, initially to maintain anaesthesia, and subsequently to act as a landmark for the passage of a fibreoptic laryngoscope loaded with a tracheal tube. In all cases, airway patency was well preserved with the device and there were no significant problems with its use. The notion of a 'dedicated airway' for difficult intubation cases is developed. A trouble-free airway will permit time to consider solutions for difficult cases and time for the novice to learn fibreoptic laryngoscopy technique.

Anesthesia, General↗