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Biomedical subjects

J R Brimacombe

Publications and source records attributed to J R Brimacombe.

At least 19 recordsLinked to original sources
PubMed1999

Laryngeal mask airway intracuff pressure estimation by digital palpation of the pilot balloon: a comparison of reusable and disposable masks.

Digital palpation of the pilot balloon provides information about the intracuff pressure of the laryngeal mask airway. The purpose of this in vitro study was to evaluate this technique for the reusable and disposable laryngeal mask airway. Ten anaesthetists and 10 recovery-unit nurses estimated intracuff pressures from low/high initial pressures before/after training. In the pretraining phase, the mean (95% CI) pressure was 99 (94-105) cmH2O, but this was significantly lower for the reusable laryngeal mask airway (91 vs. 103 cmH2O) and if the initial pressure was low (81 vs. 112 cmH2O). In the post-training phase, there was a significant overall improvement to 75 (66-85) cmH2O, but target pressures remained more accurate if the initial pressure was low. Subjects in the training group could estimate 95% of pressures for both devices to within +/-10 cmH2O of the target if the initial pressure was low. We conclude that anaesthetists and recovery-unit nurses are capable of accurate estimation of intracuff pressures using the digital palpation technique following a brief period of training.

Air Pressure↗
PubMed1999

Comparison of four methods for assessing airway sealing pressure with the laryngeal mask airway in adult patients.

We have compared four tests for assessing airway sealing pressure with the laryngeal mask airway (LMA) to test the hypothesis that airway sealing pressure and inter-observer reliability differ between tests. We studied 80 paralysed, anaesthetized adult patients. Four different airway sealing pressure tests were performed in random order on each patient by two observers blinded to each other's measurements: test 1 involved detection of an audible noise; test 2 was detection of end-tidal carbon dioxide in the oral cavity; test 3 was observation of the aneroid manometer dial as the pressure increased to note the airway pressure at which the dial reached stability; and test 4 was detection of an audible noise by neck auscultation. Mean airway sealing pressure ranged from 19.5 to 21.3 cm H2O and intra-class correlation coefficient was 0.95-0.99. Inter-observer reliability of all tests was classed as excellent. The manometric stability test had a higher mean airway sealing pressure (P < 0.0001) and better inter-observer reliability (P < 0.0001) compared with the three other tests. We conclude that for clinical purposes all four tests are excellent, but that the manometric stability test may be more appropriate for researchers comparing airway sealing pressures.

Adolescent↗
PubMed1999

The influence of the tonsillar gag on efficacy of seal, anatomic position, airway patency, and airway protection with the flexible laryngeal mask airway: a randomized, cross-over study of fresh adult cadavers.

UNLABELLED: We conducted a randomized, controlled, cross-over cadaver study to test the hypothesis that the efficacy of seal for ventilation and airway protection, anatomic position, and airway patency with the flexible laryngeal mask airway (FLMA) are altered by the application of a Boyle Davis (B-D) gag. We also determined the airway sealing pressure (ASP) at which the FLMA prevents aspiration when large volumes of fluid are placed above the cuff. We studied 20 adult cadavers (6-24 h postmortem). Efficacy of seal for ventilation and airway protection, anatomic position, and airway patency were determined with and without a B-D gag (two blade sizes: 8 and 10 cm) for the size 3, 4, and 5 FLMA in random order. Efficacy of seal for ventilation was determined by measuring the ASP at an intracuff pressure of 60 cm H2O. Efficacy of seal for airway protection was determined by flooding the mouth with 55-135 mL of water, reducing intracuff pressure until aspiration was detected fiberoptically and measuring ASP at this intracuff pressure. Anatomic position and airway patency were determined with a fiberoptic scope at an intracuff pressure of 60 cm H2O. In addition, in vivo compliance and ASP for the FLMA were measured in 10 cadavers and 10 paralyzed, anesthetized patients. Efficacy of seal for ventilation and airway protection, anatomic position, and airway patency did not change with the application of a gag for any mask size. The mean (range) ASP at which aspiration occurred when large volumes of fluid were placed above the cuff was 11 (7-15) cm H2O. The ASP for ventilation was always higher than the ASP for airway protection (P<0.0001). The FLMA had similar in vivo compliance and ASP in cadavers and anesthetized patients. We conclude that efficacy of seal for ventilation and airway protection, anatomic position and airway patency for the FLMA are unaffected by the application of a B-D gag in adults. ASP should be >15 cm H2O if there is a maximal risk of aspiration from above the cuff. IMPLICATIONS: The flexible laryngeal mask airway forms an effective seal for ventilation and protection of the airway that is unaffected by the application of a mouth gag that provides surgical access to the oropharynx. The efficacy of the seal should be >15 cm H2O if there is a maximal risk of aspiration from above the cuff.

Aged↗
PubMed1998

Use of the laryngeal mask airway in the ambulatory setting.

STUDY OBJECTIVE: To determine the utility of the laryngeal mask airway (LMA) in an ambulatory surgery practice. DESIGN: Prospective, longitudinal device (survival) study. SETTING: University-based ambulatory surgery center. PATIENTS: 1,831 ASA physical status I, II, and III outpatients undergoing superficial ambulatory surgery procedures. INTERVENTIONS: Twenty LMA devices were entered into service over a 2-year period and the number of uses, as well as the structural integrity, were assessed at the end of this study period. The serial number on each LMA device was used to track the number of times it was autoclaved, as well as the date that the device failed any of the standardized pre-use tests or was lost. MEASUREMENTS AND MAIN RESULTS: During the 2-year survey, 6,430 general anesthetics were administered at the ambulatory surgery center, with 1,831 (28%) using an LMA device for airway management. At the end of the study period, nine devices were still in use, three had been withdrawn for structural analysis by the manufacturer (after > 100 uses), three failed the pre-use test (after 38-82 uses), and five devices were lost (after 21-162 uses). The structural examination revealed that the tubes were 50% weaker; however, the cuffs, pilot balloons, and values were functioning normally. The median (range) number of uses was 92 (21-195). Thus, the 20 LMA devices evaluated tolerated an average of 92 autoclave cycles each over the 2-year observation period. CONCLUSIONS: To optimize the use of the LMA device in the ambulatory setting, it is necessary to increase awareness that it is a nondisposable piece of equipment and to adhere to the manufacturer's instructions for cleaning, sterilization, and insertion.

Ambulatory Surgical Procedures↗
PubMed1998

An evaluation of the factors influencing selection of the optimal size of laryngeal mask airway in normal adults.

The purpose of this randomised single blinded study was to determine the optimal size of laryngeal mask airway in the normal adult population, to test the validity of the current selection criteria and to determine if any externally measured anatomical variable correlated with optimal size. In each of 30 apnoeic anaesthetised adults weighting less than 100 kg, size 3, 4 and 5 laryngeal mask airways were inserted in random order by a skilled user and the cuff inflated to a standard pressure (60 cm H2O). Optimal size was based on four criteria in order of priority: number of attempts at placement, oropharyngeal leak pressure, fiberoptic score and percentage of vocal cords seen. The size 5 laryngeal mask airway was optimal in 19/30 and the size 4 in 11/30. In no patient was the size 3 the optimal fit. Oropharyngeal leak pressure was significantly higher for each progressively large size and the fiberoptic view was significantly better for the size 4 and size 5. There was no significant predictive value in any externally measured anatomical variable, but height was the most useful. The best current selection strategy was to choose a size 5 for males and size 4 for females. Potentially useful new strategies may be to use the size 5 in all adults, or a size 5 > or = 165 cm in height and size 4 for < 165 cm. We conclude that predicting the optimal size of laryngeal mask airway for individual adult patients is complex. The best size selection strategies involve use of the size 4 and 5 laryngeal mask airways in adults.

Adolescent↗
PubMed1998

Positive pressure ventilation with the laryngeal mask airway in non-paralysed patients: comparison of sevoflurane and propofol maintenance techniques.

We have compared anaesthetic maintenance and emergence characteristics of propofol and sevoflurane with the laryngeal mask airway (LMA) at commonly used doses in 185 ASA I-II patients, in a randomized, prospective study. Anaesthesia was induced with propofol 2.5-3.5 mg kg-1 and fentanyl 1-3 micrograms kg-1. Neuromuscular blocking agents were not used. All patients underwent positive pressure ventilation (PPV) with tidal volumes of 6-8 ml kg-1 to maintain normal end-tidal carbon dioxide concentration. Anaesthesia was maintained with 66% nitrous oxide in oxygen and infusion of propofol 6 or 8 mg kg-1 h-1, or 1% or 1.5% end-tidal sevoflurane. There were no failed insertion attempts and adequate ventilation was achieved in all patients. During emergence, there was a greater incidence of excitatory phenomena with 1% and 1.5% sevoflurane (95% confidence intervals (CI) 4-19%) compared with propofol (95% CI 0-4%). Sevoflurane 1.0% (95% CI 37-71%) was associated with the greatest overall incidence of respiratory and haemodynamic problems. This was significantly higher compared with propofol 6 mg kg-1 h-1 (95% CI 19-36%). Shorter times to LMA removal were observed with 1% and 1.5% sevoflurane compared with propofol (P < 0.0002). Postoperative problems did not differ between groups. We conclude that propofol 6-8 mg kg-1 h-1 and 1.5% sevoflurane were suitable for maintenance of anaesthesia for musculoskeletal surgery in non-paralysed ASA I-II patients undergoing PPV with the LMA. Emergence was more rapid with sevoflurane, but was associated with more excitatory phenomena.

Adult↗
PubMed1998

Influence of cuff volume on oropharyngeal leak pressure and fibreoptic position with the laryngeal mask airway.

We studied the size 4 laryngeal mask airway (LMA) to test the hypothesis that oropharyngeal leak pressure and fibreoptic position improves with increasing cuff volume. After LMA insertion, 50 anaesthetized adult patients had the cuff inflated in 5-ml increments to 40 ml. Oropharyngeal leak pressure was optimal at 15 ml and decreased at higher volumes. The fibreoptic position was optimal at 0-20 ml and deteriorated at higher volumes. Gastric insufflation was detected more frequently when the cuff volume exceeded 20 ml. We conclude that inflation of the size 4 LMA to the maximum recommended volume provides suboptimal conditions and that this value should be reduced from 30 to 20 ml.

Adult↗
PubMed1998

A comparison of the laryngeal mask airway and cuffed oropharyngeal airway in anesthetized adult patients.

UNLABELLED: We compared the cuffed oropharyngeal airway (COPA) with the laryngeal mask airway (LMA) in 120 anesthetized adult patients. We compared 1) placement success rates, 2) airway interventional requirements, 3) airway stability in different head/neck positions, 4) cardiorespiratory tolerance, and 5) intra- and postoperative adverse events/symptoms. A standardized anesthesia protocol was followed by four anesthesiologists experienced with both devices. Observational data were validated by independent analysis of continuous video recordings. Postoperative interviews were double-blind to the device used. The LMA had a more frequent success rate than COPA (97% vs 55%, P < 0.00001), an overall higher success rate (100% vs 83%; P = 0.001), a shorter time to achieve an effective airway (49 vs 188 s; P < 0.00001), a higher oropharyngeal leak pressure (21 vs 16 cm H2O; P = 0.003), and a fewer number of chin lift airway interventions required (0.1% vs 42%; P < 0.00001). When comparing mean tidal volumes in different head/neck positions to assess airway stability, the quality of airway was unchanged in 98% patients with the LMA and 54% with the COPA (P < 0.00001). The incidences of intraoperative adverse events were similar. On removal, blood was detected more often on the COPA (3% vs 14%; P = 0.04). In the late postoperative period, more patients complained of adverse symptoms with the COPA than with the LMA (26% vs 57%; P = 0.001). Late postoperative symptoms occurred more frequently with the COPA (0.87 vs 0.34; P = 0.003). There was more late postoperative sore throat (14% vs 36%; P = 0.0003) and more jaw/neck pain (12% vs 26%; P = 0.0008) in patients managed with the COPA. This study demonstrates that the LMA offers advantages over the COPA in most technical aspects of airway management and in terms of postoperative morbidity. IMPLICATIONS: In this randomized, prospective study, we compared the laryngeal mask airway and the cuffed oropharyngeal airway in anesthetized patients. The laryngeal mask airway offers advantages in most technical aspects of airway management and in terms of postoperative morbidity.

Adult↗
PubMed1998

The laryngeal mask airway in emergency medicine, neonatal resuscitation, and intensive care medicine.

In assessing the potential role of the LMA outside the operating room, the risks of a less secure airway must be balanced against the benefits of ease of training, success and speed of insertion, no need for direct visualization of laryngeal structures, and lesser need for ancillary equipment. The LMA has a role as an alternative to FMV in CPR when personnel skilled in tracheal intubation are not available. When skilled intubators are present, it has an important role as an alternative airway when intubation has been impossible. These roles extend to the prehospital setting, with an additional specific indication for its use when access to a patient is limited making tracheal intubation impossible. The LMA is incorporated into advanced life support training and as such should be regarded as a device providing temporary airway support, rather than a replacement for a tracheal tube. The LMA, and possibly also the ILM, should be standard equipment carried by prehospital trauma teams and by all those attending victims in the field.

Adult↗
PubMed1997

Cricoid pressure.

PURPOSE: Although cricoid pressure (CP) is a superficially simple and appropriate mechanical method to protect the patient from regurgitation and gastric insufflation, in practice it is a complex manoeuvre which is difficult to perform optimally. The purpose of this review is to examine and evaluate studies on the application of (CP). It deals with anatomical and physiological considerations, techniques employed, safety and efficacy issues and the impact of CP on airway management with special mention of the laryngeal mask airway. SOURCE OF MATERIAL: Three medical databases (48 Hours, Medline, and Reference Manager Update) were searched for citations containing key words, subject headings and text entries on CP to October 1996. PRINCIPLE FINDINGS: There have been no studies proving that CP is beneficial, yet there is evidence that it is often ineffective and that it may increase the risk of failed intubation and regurgitation. After evaluation of all available data, potential guidelines are suggested for optimal use of CP in routine and complex situations. CONCLUSIONS: If CP is to remain standard practice during induction of anaesthesia, it must be shown to be safe and effective. Meanwhile, further understanding of its advantages and limitations, improved training in its use, and guidelines on optimal force and method of application should lead to better patient care.

Cricoid Cartilage↗
PubMed1997

Positive pressure ventilation with the size 5 laryngeal mask.

STUDY OBJECTIVE: To obtain data about the safety and efficacy of the size 5 laryngeal mask airway (LMA), which is a scaled-up version of the size 4 and is generally recommended for patients over 90 kg, for positive pressure ventilation (PPV), ease of insertion, oropharyngeal and gastric insufflation pressures, fiberoptic positioning, and complication rates. DESIGN: Prospective survey. SETTING: Teaching hospital. PATIENTS: 179 patients undergoing PPV with the size 5 LMA. INTERVENTIONS: The clinical criteria for using the size 5 LMA and the PPV technique were weight above 90 kg or an inadequate seal with a size 4 LMA and surgery estimated to last longer than 45 minutes. Anesthesia was standardized and included fentanyl/propofol for induction, N2O/O2/isoflurane 0.5% to 2% for maintenance, and atracurium for muscle relaxation. Two 20-second attempts were allowed with the standard recommended technique, followed by a single attempt with the Guedel technique. The LMA cuff was then inflated and the airway pressure at which either oropharyngeal leak or gastric insufflation occurred was determined by closure of the expiratory valve and anterior neck followed by epigastric auscultation. MEASUREMENTS AND MAIN RESULTS: The age and weight range were 15 to 82 years and 46 to 153 kg, respectively. 29% of patients had a body mass index (BMI) above 30 kg/m2. On 31 occasions the size 5 was used following an inadequate seal with the size 4. The weight range of this subgroup was 46 to 87 kg. The device was placed within 20 seconds in 94% and there were no failed placements within three attempts. Gastric insufflation was detected before oropharyngeal leak in 17% and oropharyngeal leak was detected first in 73%. In 10% of patients there was no leak at an inspiratory pressure of 45 cm H2O. Mean (range) for gastric insufflation pressure was 31 (range 23-45) cm H2O. Mean (range) for oropharyngeal leak was 33 (range 8-44) cm H2O. The mean (range) airway pressure was 17 (range 13-26) at tidal volumes of 10 ml/kg. At this tidal volume, 97.2% of patients could be ventilated without gastric insufflation and 98.3% without an oropharyngeal leak. At tidal volumes of 8 ml/kg no patient had gastric insufflation and 0.7% had an oropharyngeal leak. Oropharyngeal leak pressure of less than 15 cm H2O occurred in 11 patients. There was no correlation between fiberoptic score or Mallampati score and either gastric insufflation or oropharyngeal leak. The incidence of problems was 3% and the oxygen saturation remained above 94%. There was no correlation between problems, leak pressures, and BMI. CONCLUSIONS: Positive pressure ventilation with the size 5 LMA is safe and effective with a low failure/problem rate using tidal volumes of 8 to 10 ml/kg, even in those patients who are moderately obese. The device is suitable for patients weighing under 90 kg in whom the seal with the size 4 is inadequate.

Adolescent↗