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Biomedical subjects

A B Lumb

Publications and source records attributed to A B Lumb.

13 recordsLinked to original sources
PubMed2003

New aspects of ventilation in acute lung injury.

Recent recognition that artificial ventilation may cause damage to the acutely injured lung has caused renewed interest in ventilation techniques that minimise this potential harm. Many ventilation techniques have proved beneficial in small trials of very specific patient groups, but most have subsequently failed to translate into improved patient outcome in larger trials. An exception to this is 'protective ventilation' using reduced tidal volumes (to lower airway pressure) and increased PEEP (to reduce pulmonary collapse). Results of trials of protective ventilation have been encouraging, and the technique should now be adopted more widely. High frequency ventilation, inverse ratio ventilation, prone positioning and inhaled nitric oxide are all techniques that may be considered when, in spite of optimal artificial ventilation, the patient's gas exchange remains dangerously poor. Under these circumstances, the choice of technique is dependent on their availability, local expertise and individual patient needs.

Humans↗
PubMed2000

Difficulties with anonymous shortlisting of medical school applications and its effects on candidates with non-European names: prospective cohort study.

OBJECTIVE: To assess the feasibility of anonymous shortlisting of applications for medical school and its effect on those with non-European names. DESIGN: Prospective cohort study. SETTING: Leeds school of medicine, United Kingdom. SUBJECTS: 2047 applications for 1998 entry from the United Kingdom and the European Union. INTERVENTION: Deletion of all references to name and nationality from the application form. MAIN OUTCOME MEASURES: Scoring by two admissions tutors at shortlisting. RESULTS: Deleting names was cumbersome as some were repeated up to 15 times. Anonymising application forms was ineffective as one admissions tutor was able to identify nearly 50% of candidates classed as being from an ethnic minority group. Although scores were lower for applicants with non-European names, anonymity did not improve scores. Applicants with non-European names who were identified as such by tutors were significantly less likely to drop marks in one particular non-academic area (the career insight component) than their European counterparts. CONCLUSIONS: There was no evidence of benefit to candidates with non-European names of attempting to blind assessment. Anonymising application forms cannot be recommended.

Cohort Studies↗
PubMed1997

Applicants to medical school: the value of predicted school leaving grades.

Among school leavers applying to study medicine in the United Kingdom a majority offer General Certificate of Education, Advanced Level (A-level) examinations as part of the assessment of academic ability. At the time of application, up to 9 months before completing A-level studies, schools are requested to predict the final grades likely to be achieved by the applicant. A total of 5054 A-level predictions from 1661 applicants to a single medical school were compared with the results achieved. Predicted and achieved grades were both high with 93% of predicted grades being A or B. Over half the predictions were correct, with 41% of predictions above achieved grades and only 7% below achieved grade. Independent and selective schools predicted higher grades than comprehensive schools and sixth form colleges, and their pupils were more likely to achieve the entrance requirements. A-level predictions for medical school applicants are a strong predictor of achievement and should continue to be regarded as a useful part of the selection process.

Adolescent↗
PubMed1994

Effect of dried ginger on human platelet function.

Eight healthy male volunteers took part in a randomised double blind study of the effects of 2 g dried ginger or placebo capsules on platelet function. Bleeding time, platelet count, thromboelastography and whole blood platelet aggregometry were performed before, 3 h, and 24 h after the capsules. There were no differences between ginger and placebo in any of the variables measured. It is concluded that the effect of ginger on thromboxane synthetase activity is dose dependent, or only occurs with fresh ginger, and that upto 2 g of dried ginger is unlikely to cause platelet dysfunction when used therapeutically.

Adult↗
PubMed1992

The effect of nitrous oxide on laryngeal mask cuff pressure. In vitro and in vivo studies.

We have studied the effect of nitrous oxide on the cuff pressure of a laryngeal mask both in vitro and in vivo. In laboratory tests, we showed that nitrous oxide and carbon dioxide diffuse across the cuff wall much more rapidly than nitrogen and oxygen. Differing partial pressures of these gases across the cuff wall therefore give rise to changes in volume and pressure within the cuff. We then studied 18 patients undergoing general anaesthesia with nitrous oxide, and found a consistent and linear increase in cuff pressure in all patients. After 30 min, the mean pressure had increased by 30 mmHg, and there was approximately 10% nitrous oxide in the cuff. It is difficult to relate these findings to pressure on pharyngeal structures, but methods of limiting the rise in intracuff pressure are discussed.

Adult↗
PubMed1992

Estimation of tidal volume from the reservoir bag. A laboratory study.

The accuracy of 21 anaesthetists in estimating tidal volumes from reservoir bag movements was assessed using a model lung apparatus. The breathing system configuration (Mapleson A or D), the grade of anaesthetist, and the years of anaesthetic experience had no effect on accuracy. Greater precision of tidal volume estimation was observed with larger tidal volumes and lower fresh gas flows. The mean systematic error of 18 of the 21 anaesthetists was greater than zero, indicating a general tendency to overestimate tidal volume. This study therefore strengthens the view that clinical observations should be supplemented with information from continuous monitoring devices.

Anesthesia, Inhalation↗
PubMed1991

Ribcage contribution to CO2 response during rebreathing and steady state methods.

Disagreements exist between previous studies of the contribution of the rib cage (RC) and abdomen-diaphragm (AD) components to CO2-stimulated ventilation. These studies used dissimilar techniques of CO2 stimulation and varying methods of data processing and presentation, thus precluding direct comparisons. We have therefore studied two methods of CO2 stimulation in 12 subjects, using a Read's rebreathing method and a modified steady-state technique. Respiratory inductive plethysmography was used to assess the RC and AD contributions to ventilation. Mean slopes for the ventilatory response to CO2 were the same for both methods (mean 2.56 L.min-1.mmHg-1), and the intercepts were significantly different (43.7 mmHg for rebreathing and 38.0 for modified steady state: P less than 0.001). There was a small, but significant, increase in the percentage RC contribution to ventilation during hypercapnia of 0.97%/mmHg PCO2 for rebreathing and 0.62 for steady state (P less than 0.01 and P less than 0.05, respectively), and these values were not significantly different from each other. Using our data in comparison with other studies, we have been able to show that differences in processing and presentation of data have given rise to wide variations in conclusions.

Adult↗
PubMed1991

Absorption of isoflurane by silica gel.

We have studied the capacity of the drying agent silica gel (SG) to absorb isoflurane from gas samples. When dry, SG was able to absorb 31 times its own volume of isoflurane vapour, which could be recovered almost completely from the SG by displacement with water vapour. However, we were unable to demonstrate any significant absorption of isoflurane by wet SG. Care must be taken, therefore, when using SG as a drying agent in the sampling line of an analyser during research involving volatile anaesthetic agents.

Anesthesiology↗
PubMed1991

Rib cage contribution to resting and carbon dioxide stimulated ventilation during 1 MAC isoflurane anaesthesia.

Using respiratory inductive plethysmography, we have measured rib cage and abdominal motion during isoflurane anaesthesia in 16 healthy day-surgery patients. Anaesthesia was induced with propofol and maintained with 1 MAC isoflurane in air-oxygen via a laryngeal mask. Measurements were taken during both resting ventilation and hyperpnoea induced by rebreathing carbon dioxide. For resting ventilation, the rib cage contributed a mean (SD) of 33 (15)% of the total ventilation whilst awake, and 39 (12)% during anaesthesia (ns). With increasing end-tidal carbon dioxide whilst awake, the subjects showed a mean increase in the percentage rib cage contribution of 7.1 (12.5)%/kPa of carbon dioxide. With isoflurane anaesthesia, there was significant depression of this rib cage recruitment with the mean contribution decreasing by 3.6 (7.4)% kPa-1 (P less than 0.05). These results indicate that 1 MAC of isoflurane does not selectively depress rib cage motion, except during carbon dioxide stimulated hyperpnoea.

Abdominal Muscles↗
PubMed1991

Respiratory function and ribcage contribution to ventilation in body positions commonly used during anesthesia.

Lung function tests are normally performed in the upright position, whereas anesthesia is usually administered with the patient in the supine position, and occasionally in other postures. We therefore compared forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), functional residual capacity (FRC), and ribcage contribution to ventilation by respiratory inductive plethysmography in 13 conscious healthy male volunteers, sitting and in four horizontal positions used during anesthesia. Forced vital capacity and FEV1 were similar in all positions, except for a significant mean increase in FVC of 300 mL (SD 213) when sitting compared with when supine (P less than 0.001). The mean decrease in FRC was 806 mL (SD 293) between the sitting and supine positions (P less than 0.001). A significant increase in FRC occurred (252 mL, SD 329, P less than 0.01) when supine subjects raised their arms above their heads as required for computed tomography. Functional residual capacity in the prone and lateral positions was significantly larger than in the supine position (mean change 350 mL, P less than 0.001), but was still some 450 mL less than in the sitting position. Mean ribcage contribution was similar in all horizontal positions (32%-36%), whereas supine values were significantly different from those of the sitting position (mean 70%, SD 11, P less than 0.001). In conclusion, the various horizontal postures studied have no effect on FVC, FEV1, or ribcage contribution to ventilation. However, FRC in the prone, lateral, and arms-up positions is on average 250 mL larger than in the supine position, an observation that may affect gas exchange during anesthesia in these positions.

Adult↗
PubMed1989

'Cured' myasthenia gravis and neuromuscular blockade.

A symptomless myasthenic patient who played representative squash received 0.1 mg/kg of vecuronium and enflurane as part of a general anaesthetic for elective gynaecological surgery. Neuromuscular block was prolonged. The effect of neuromuscular blocking agents and volatile anaesthetics in symptomless myasthenics is discussed. We conclude that these patients should be assumed to be sensitive to such agents.

Adult↗
PubMed1989

Respiratory arrest after a caudal injection of bupivacaine.

A 3.5-year-old child with Cornelia de Lange syndrome presenting for orchidopexy and herniotomy received general anaesthesia which was supplemented by a caudal injection of bupivacaine. Shortly after this he had a respiratory arrest with fixed dilated pupils. No cardiovascular system instability was observed. Approximately one hour later the child made a rapid and complete recovery. The possible causes of these events are discussed with particular reference to the potential effects of caudal injections on intracranial pressure.

Anesthesia, Epidural↗