We read with interest the paper by Sudhir et al. [1] who evaluated the performance of various Miller laryngoscope blades (11 disposable and one re-useable). Their primary outcome measures were forces developed during laryngoscopy with concurrent assessment of the laryngoscopic view. The blades were ranked in the paper by each measure. We have an interest in laryngoscopic force and believe force to be an important factor in difficult laryngoscopy. Hastings et al. [2] measured torque during laryngoscopy in adults and considered it close to the maximum the human wrist could generate. Our personal experience of the extra effort necessary to perform the manoeuvre in the presence of cricoid pressure would support this view [3]. We have reanalysed Sudhir’s data to examine the relationship between force and view. This analysis demonstrates a remarkable association between force generated by the blade and the laryngoscopic view. In the Sudhir study 50 anaesthetists performed laryngoscopy with 12 blades in random sequence on an intubating manikin. They measured both horizontal force (Fx) and vertical force (Fy) applied during laryngoscopy and assessed the resultant ‘field of view’ (FOV) by visual analogue score (0– 100 mm). We have examined the relationship by linear regression analysis between the mean values presented given for each blade for force (Fx and Fy) and FOV. We also calculated the magnitude of the directional force (Fv) from the component forces Fx and Fy and its direction as an angle from horizontal (Av) and subjected this to the same analysis. We found a strong correlation between FOV and both horizontal (Fx) and vertical force (Fy) (r = 0.89 and 0.91, respectively); the blades producing a better ‘view’ generating lower force. When the components Fx and Fy are resolved into a single vector Fv its correlation with FOV becomes almost perfect (r = 0.98). Figure 1 shows the relationship between FOV and Fv for each blade. Each point on the graph represents an individual Miller blade. (The values are the mean of 50 independent observations for each parameter). The direction (Av) of the vector Fv correlates poorly with view (r = 0.13). However, Av varied between blades in the study by only 3 . It is difficult to assess the clinical significance of a manikin study, particularly when the validity of the model is unknown. Only information in adults about vertical forces in laryngoscopy is available in the literature [4, 5]. We are unaware of any studies of horizontal force in adults or of either force in children. It is impossible to blind the operator to the blade in this type of study, and this may have introduced bias. Two other assessments of the blade in the Sudhir study show an equally high correlation with Fv: ‘build quality’ (VAS 0-100) r = 0.96; and ‘willingness to use in an emergency situation’ (VAS 0-100) r = 0.97. It is possible that all three assessments, entirely subjective in nature, may have been influenced by the operator’s prior experience of the relative effort required to achieve a grade 1 view, the set endpoint of the study, with each blade. Despite these limitations, we find it remarkable that force and ‘view’ are so closely associated in the Sudhir data. It suggests that the force required to perform the manoeuvre was the determining factor in the operator’s assessment of the laryngoscopic ‘view’ and quality of the blade. The relationship between force and the difficulty experienced by the operator when performing laryngoscopy would seem to be worthy of further study. The magnitude of directional force in the sagittal plane appears to be the best measure, although this requires the simultaneous measurement of vertical and horizontal force. If a strong relationship exists in humans between force and view then we may have a simple, quantifiable and objective means to assess the relative difficulty of laryngoscopy.

The impact of cricoid pressure on laryngoscopy is unknown. We have developed a quantitative method of recording the laryngoscopic view using a rigid, zero-degree endoscope. We found that an image matching the laryngoscopist's view could be obtained by positioning the endoscope along the laryngoscopist's 'line of sight'. Photographing this image allowed us to measure laryngeal exposure. We set out to define the effect of cricoid pressure on laryngoscopy using this method. In 40 patients undergoing elective surgery, laryngoscopy was performed with cricoid pressures of 0-60 N, increasing by increments of 10 N. We photographed the laryngoscopic view at each force and recorded dynamic images as cricoid pressure was released. The change in laryngoscopic view with increasing cricoid pressure fell into one of four broad patterns: little change (11 subjects); gradual deterioration (10 subjects); improvement at low force (< 20 N) followed by deterioration (9 subjects); improvement at high force (> 30 N) (10 subjects). We identified five subjects with a good initial view (anteroposterior length of the rima glottidis > 5 mm) who showed a marked deterioration in laryngoscopic view as cricoid pressure increased; in three of these subjects this progressed to obscure the larynx completely at a force of 30 N, 40 N and 60 N, respectively. We conclude that the effect of cricoid pressure on laryngoscopy is complex. However, in some individuals, a force close to that currently recommended (30 N) may cause a complete loss of the glottic view.

Objectives Invasive meningococcal disease (IMD) is an urgent notifiable disease and its early notification is essential to prevent cases. The objective of the study was to assess the sensitivity of two independent surveillance systems and to estimate the incidence of IMD. Design We used capture–recapture model based on two independent surveillance systems, the statutory disease reporting (SDR) system and the microbiological reporting system (MRS) of the Public Health Agency of Catalonia, between 2011 and 2015. The capture–recapture analysis and 95% CIs were calculated using the Chapman formula. Multivariate vector generalised linear model was performed for adjusted estimation. Measures The variables collected were age, sex, year of report, size of municipality (<10 000 and ≥10 000), clinical form, death, serogroup, country of birth and type of reporting centre (private and public). Results The sensitivity of the two combined surveillance systems was 88.5% (85.0–92.0). SDR had greater sensitivity than the MRS (67.9%; 62.7–73.1 vs 64.7%; 59.4–70.0). In 2014–2015, the sensitivity of both systems was higher (80.6%; 73.2–87.9 vs 73.4%; 65.2–81.6) than in 2011–2013 (59.3%; 52.6–66.0 vs 58.3%; 51.6–65.1). In private centres, the sensitivity was higher for SDR than for MRS (100%; 100–100 vs 4.8%; −4.4–13.9). The adjusted estimate of IMD cases was lower than that obtained using the Chapman formula (279; 266–296 vs 313; 295–330). The estimated adjusted incidence of IMD was 0.7/100 000 persons-year. Conclusions The sensitivity of enhanced surveillance through the combination of two complementary sources was higher than for the sources individually. Factors associated with under-reporting in different systems should be analysed to improve IMD surveillance.

The laryngeal mask airway has revolutionised airway management in anaesthesia and seems set to do so for resuscitation. Its appeal is based largely on less need for skill and training than with either facemask or an endotracheal tube.1 All paramedic crews and emergency departments have the laryngeal mask as standard equipment, and its popularity in hospital resuscitation is growing. Gas leak and gastric inflation are well recognised complications of positive pressure ventilation with the laryngeal mask.2 3 We present a case in which the use of a laryngeal mask during an out of hospital cardiac arrest led to massive gastric dilation, gastric rupture, and a tension pneumoperitoneum. A 71 year old man with a history of angina and hypertension developed chest pain and collapsed in a shopping centre. A bystander performed cardiopulmonary resuscitation for about seven minutes until a paramedic unit arrived. A paramedic inserted a laryngeal mask airway and started hand ventilation at a rate of 12 breaths/min with a 1600 ml self inflating resuscitation bag with reservoir and oxygen supply set to 12 litres per minute. Normal chest movement and auscultation of the chest confirmed correct placement of the mask. The paramedic then resumed chest compression at a rate of 100 per minute synchronous with ventilation. Three lead electrocardiography showed ventricular fibrillation. A single DC shock of 200 J restored sinus rhythm, with a good cardiac output after about five minutes of the paramedic starting cardiopulmonary resuscitation. The patient was then transferred to our emergency department; although some respiratory effort was noted, this was considered inadequate by the paramedic, who ventilated the patient by hand throughout the 25 minute journey to hospital. The paramedic saw no episodes of retching, coughing, or vomiting. On the patient's arrival in the emergency department, doctors noted the following in the …

Cricoid pressure is frequently used to protect the anaesthetised and paralysed patient from passive regurgitation. Although intragastric pressure (Pga) drives regurgitation, its relevance in the setting of protective cricoid force has been largely ignored. We sought to define the likely range of Pga encountered in the population at risk. We studied 100 consecutive patients presenting for surgery requiring mechanical ventilation. We measured respiratory swings in Pga during mechanical ventilation in the paralysed state following rapid sequence induction (n = 24) and routine induction of anaesthesia (n = 76). Pga (mmHg) in the whole group recorded at end-inspiration (Pga-In) and end-expiration (Pga-Ex) was [mean (SD)]: Pga-In 6.48 (2.60) mmHg and Pga-Ex 3.23 (2.24) mmHg. We found no correlation between Pga and body mass index (r2 = 0.018). These findings have implications for the level of cricoid force required to protect a patient during the induction of anaesthesia.

We investigated the cricoid pressure technique of 135 anaesthetic assistants attending the annual conference of the British Association of Operating Department Assistants in May 1997. Their knowledge and training were assessed using a structured interview. Technique was assessed using a simulator measuring applied force during sham cricoid pressure. Our additional aims were to see whether a knowledge of the required force and practical training in the application of a target force would affect performance. Our results highlight a lack of knowledge relating to the manoeuvre. Only about one-third of subjects could quote an appropriate force and fewer than half could give a single contraindication to its use. Very few subjects had been trained on a model before practising the technique on a patient. Technique was poor and we observed a large variation in the force actually applied. Performance, as assessed by the variability of forces applied and proportion of subjects applying force within our target range (30-44 N), was improved markedly by providing simple instruction about the required force in an understandable form. Performance was further improved by practical training in the application of target force on a simulator.

We studied six operating department assistants performing simulated cricoid pressure on a model of the larynx with the arm either flexed to 90 degrees (flexed position) or fully extended with the elbow locked (extended position). Subjects were asked to maintain forces of 20, 30 and 40 Newtons (N) for a target time of 20 min. Subjects rated pain during each assessment on a four-point verbal rating scale (VRS): 1 = uncomfortable; 2 = hurting; 3 = hurting a lot; and 4 = agony. Times to onset of pain were short and mean times to VRS 3 at each force studied were: 40 N, flexed position 2.3 min, extended position 5.4 min; 30 N, flexed position 4.0 min, extended position 7.5 min; and 20 N, flexed position 9.6 min, extended position 12.5 min. None of our subjects was able to sustain 40 N for the target time. Mean times to release at 40 N were: flexed position 3.7 min, extended position 7.6 min. Only one subject was able to sustain 30 N and then only using the extended arm. Mean times to release at 30 N were: flexed position 6.4 min, extended position (five subjects) 10.8 min. Two subjects with the arm flexed and five with the arm extended achieved the target time at 20 N. Mean times to release at 20 N were: flexed position (four subjects) 13.2 min, extended position (one subject) 14.6 min. Use of the extended arm consistently prolonged times to pain and fatigue. These findings are relevant to the management of cricoid pressure during failed intubation.

A single i.v. bolus dose of propofol 3 mg kg-1 was compared with methohexitone 2 mg kg-1 as the sole anaesthetic agent for simple dental extraction in outpatients. Induction of anaesthesia was smoother with propofol, with a lower incidence of excitatory phenomena. Pain on injection was a common complication of both drugs and related to the site of injection. The Leeds Psychomotor Tester was used to assess psychomotor performance during the recovery. Rate of recovery from anaesthesia was similar with both agents, and there was little residual impairment of psychomotor function 40 min after induction.