Peter Baskett

The incidence of regurgitation during cardiopulmonary resuscitation: a comparison between the bag valve mask and laryngeal mask airway

The risk of gastric regurgitation and subsequent pulmonary aspiration is a recognised complication of cardiac arrest--a risk which may be further increased by the resuscitative procedure itself. The purpose of this study was to compare the incidence of gastric regurgitation between the bag valve mask (BVM) and laryngeal mask airway (LMA). The resuscitation data collection forms of 996 patients who underwent in-hospital cardiopulmonary resuscitation over a 3.5 year period were reviewed. Of these, 199 patients were excluded from the study because there was no airway management involving a BVM or LMA. The incidence and timing of regurgitation was studied in the remaining 797 patients. Regurgitation was recorded to have occurred at some stage in 180 of these patients (22.6%). However, 84 regurgitated prior to CPR (46.7% of those patients who regurgitated). These patients were excluded from further analysis as regurgitation could not have been affected by any form of ventilation. Of the remaining 713 patients, BVM ventilation was used in 636 cases. In 170 of these the LMA was also used following the BVM. Where the patient was ventilated with the BVM alone or BVM followed by ETT the incidence of regurgitation during CPR was 12.4%. The LMA was used during resuscitation in 256 cases of which 170 had BVM ventilation prior to the LMA. Where the patient was ventilated with the LMA alone or LMA followed by ETT the incidence of regurgitation during CPR was 3.5%. The study confirms experience reported in earlier studies that when an LMA is used as a first line airway device, regurgitation is relatively uncommon.

The intubating laryngeal mask. Results of a multicentre trial with experience of 500 cases.

A multicentre trial of the use of the intubating laryngeal mask was carried out at seven centres in the United Kingdom using the same agreed protocol. Lung ventilation followed by blind tracheal intubation through the intubating laryngeal mask was attempted on 500 ASA grade 1 and 2 patients. It was possible to insert the intubating laryngeal mask in all 500 cases. Ventilation via the intubating laryngeal mask was described as satisfactory in 475 (95%) cases, difficult in 20 (4%) cases and unsatisfactory in 5 (1%) cases. Blind tracheal intubation through the intubating laryngeal mask was possible in 481 (96.2%) cases within three attempts. Intubation was successful at the first attempt in 399 (79.8%) cases, at the second attempt in 62 (12.4%) cases and at the third attempt in 20 (4%) cases. The tracheas of 19 (3.8%) patients were not successfully intubated within the three attempts. Ventilation via the intubating laryngeal mask was described as unsatisfactory during two of these cases but oxygenation remained satisfactory in spite of this. Seventeen of the 19 failures occurred during the individual operators first 20 attempts. The intubating laryngeal mask provides a successful method for blind tracheal intubation in a large proportion of cases and appears to be superior to the standard laryngeal mask airway for this purpose. The intubating laryngeal mask may be of use when tracheal intubation has failed using conventional methods.

The intubating laryngeal mask. Use in failed and difficult intubation.

The use of the intubating laryngeal mask in three patients is described. In two patients for whom tracheal intubation using traditional techniques had failed, the intubating laryngeal mask was used to achieve successful tracheal intubation. The trachea of one of these patients was subsequently re‐intubated for a second procedure using the same technique. A third patient with a cervical spine fracture whose trachea was electively intubated using the intubating laryngeal mask is also presented.

Guidelines for the basic management of the airway and ventilation during resuscitation

Writing Subcommittee: P.J.F. Baskett ** (UK), L. Bossaert (Belgium), P. Carli (France), D. Chamberlain (UK), W. Dick (Germany), J.P. Nolan (UK), M.J.A. Parr (UK), D. Scheidegger (Switzerland), D. Zideman (UK) With contributions from: W. Blancke (Belgium), H. Delooz (Belgium), A. Handley (UK), D. Kettler (Germany), W. Kloeck (South Africa), E. Kramer (South Africa), L. Quan (USA), W. Studer (Switzerland), A. Van Drenth (The Netherlands)

Tidal volumes which are perceived to be adequate for resuscitation

Observers trained in basic life support assessed chest rise in 34 patients who were anaesthetised and paralysed and whose lungs were being mechanically ventilated prior to routine surgery. Making 67 independent assessments, the observers indicated the tidal volume that they considered produced adequate chest rise for resuscitation. The mean tidal volume perceived to be adequate was 384 ml with 95% confidence limits of 362-406 ml. The perceived volumes correlated with the Body Mass Index. Guidelines by various authorities recommend that tidal volumes sufficient to make the chest rise normally should be used during resuscitation. The volumes perceived as adequate by the observers are much lower than the numerical values recommended by the American Heart Association (800-1200 ml). High tidal volumes are associated with an increased risk of gastric regurgitation in patients with an unprotected airway, CO2 delivery to the lungs is likely to be low during cardiac arrest obviating the need for high tidal volumes. In the light of present knowledge and the findings in this study, we would recommend that resuscitation training manikins are recalibrated to indicate satisfactory ventilation at tidal volumes of 400-600 ml. These volumes should reduce the risk of gastric inflation and permit more chest compressions to be carried out in a minute because the ventilation fraction of the CPR sequence is shorter. Adequate CO2 elimination should still be assured.

Recommendations for uniform reporting of data following major trauma--the Utstein style. A report of a working party of the International Trauma Anaesthesia and Critical Care Society (ITACCS).

Members: W.F. Dick (Co-Chairman) (Germany); P.J.F. Baskett (Co-Chairman) (UK); C.M. Grande (USA); H. Delooz (Belgium); W. Kloeck (South Africa); C. Lackner (Austria); M. Lipp (Germany); W. Mauritz (Austria); M. Nerlich (Germany); J. Nicholl (UK); J.P. Nolan (UK); P. Oakley (UK); M.J.A. Parr (UK), A. Seekamp (Belgium); E. Soreide (Norway); P.A. Steen (Norway); Luc van Camp (Belgium); B. Wolcke (Germany); D. Yates (UK).

The respiratory system during resuscitation: a review of the history, risk of infection during assisted ventilation, respiratory mechanics, and ventilation strategies for patients with an unprotected airway

The fear of acquiring infectious diseases has resulted in reluctance among healthcare professionals and the lay public to perform mouth-to-mouth ventilation. However, the benefit of basic life support for a patient in cardiopulmonary or respiratory arrest greatly outweighs the risk for secondary infection in the rescuer or the patient. The distribution of ventilation volume between lungs and stomach in the unprotected airway depends on patient variables such as lower oesophageal sphincter pressure, airway resistance and respiratory system compliance, and the technique applied while performing basic or advanced airway support, such as head position, inflation flow rate and time, which determine upper airway pressure. The combination of these variables determines gas distribution between the lungs and the oesophagus and subsequently, the stomach. During bag-valve-mask ventilation of patients in respiratory or cardiac arrest with oxygen supplementation (> or = 40% oxygen), a tidal volume of 6-7 ml kg(-1) ( approximately 500 ml) given over 1-2 s until the chest rises is recommended. For bag-valve-mask ventilation with room-air, a tidal volume of 10 ml kg(-1) (700-1000 ml) in an adult given over 2 s until the chest rises clearly is recommended. During mouth-to-mouth ventilation, a breath over 2 s sufficient to make the chest rise clearly (a tidal volume of approximately 10 ml kg(-1) approximately 700-1000 ml in an adult) is recommended.

Use of Entonox in the Ambulance Service

An analgesic mixture of nitrous oxide and oxygen (Entonox) has been used in nine ambulances in Gloucestershire for self-administration by patients in severe pain. Over a period of three and a half months 66 patients have been treated. In all cases the pain was wholly or partially relieved, and in no instance was the patients condition worsened. No undesirable side-effects attributable to Entonox were produced. It is recommended that other ambulance authorities should consider the use of Entonox in this context.

The United Kingdom pre-hospital study of active compression-decompression resuscitation

This prospective, controlled trial with crossover group design compares the effectiveness of active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) and standard CPR on the outcomes of victims of prehospital cardiac arrest. In three UK cities, victims of non-traumatic, out of hospital cardiac arrest, over the age of 8 years received either standard or ACD-CPR on arrival of ambulance personnel. Main outcome measures were return of spontaneous circulation, survival to be admitted to the intensive care unit, survival to hospital discharge, and neurological outcome. A total of 576 patients (STD-CPR, n=309; ACD-CPR, n=267) were analysed. The treatment groups were similar with respect to age, gender, proportion of witnessed arrests, initial cardiac rhythm, and call to advanced life support interval. The proportion of patients receiving bystander CPR was higher in the ACD group (37.1% vs. 28.5%; P=0.028). The interval between collapse and defibrillation was longer in the ACD group (12.3 min vs. 10.4 min; P=0.028). There was no difference between the STD-CPR and ACD-CPR groups in survival to admission to the intensive care unit (13.6% vs. 13.8%; P=0.93) or hospital discharge (4.8% vs. 6.0%; P=0.67). There was no difference between the groups with respect to the neurological outcome of those patients surviving to hospital discharge. Analysis of important subgroups also showed no benefit for ACD-CPR. We conclude that there was no improvement in outcome with ACD-CPR when used by ambulance personnel in Cardiff and Portsmouth.

Nitrous oxide in pre-hospital care.

Nitrous oxide was first introduced into pre-hospital care in the United Kingdom in 1970 (1, 2) to fill the analgesic gap in the management of patients suffering from trauma, myocardial infarction and other painful conditions. Hitherto, because of the strongest legal constrictions applied to administration of the opiates, members of the ambulance service had been unable to provide any form of analgesia at all. As a consequence, pain relief was delayed until the patient reached the care of a physician usually in hospital. Nitrous oxide analgesia was able to be introduced because of the development of a relatively stable mixture of nitrous oxide and oxygen in equal proportions in a single cylinder known as Entonox. This gas mixture had been introduced initially in 1961 for the relief of pain in childbirth by Tunstall (3). In collaboration with scientists at the British Oxygen Company, he had found that a 50/50 mixture of nitrous oxide and oxygen compressed to 1890 lbs per square inch (135 Kg/sq in) would remain stable at temperatures above -5°C without any tendency towards liquidification of the nitrous oxide fraction. A few years later Parbrook & Kennedy (4) demonstrated the value of premixed nitrous oxide and oxygen in postoperative pain relief and Parbrook et al. (5) , also showed that the analgesic power of the mixture was comparable to 15 mg morphine sulphate given intramuscularly. Alongside the development of the gas mixture came the design and manufacture of a suitable device for administration. The original Entonox apparatus designed by BOC worked on the demand principle and was designed for patient self-administration. A pin index system was featured as a safety mechanism so that the device could only be used with an Entonox gas mixture cylinder. Since the introduction of the original inhalational unit, improvements in design have been made by BOC and by Pneupac Ltd., but the basic principles of the system are retained. The self-administration demand system is ideal for use in pre-hospital care with supervision by ambulance personnel. Should a patient with a particular sensitivity to the gas mixture become drowsy then hidher grip on the mask relaxes, the airtight seal at the mask/patient interface is lost and the gas flow ceases. The features of Entonox self-administered with a demand apparatus may be listed in comparison with the ideal analgesic for pre-hospital care: Effectiveness The gas mixture is equivalent to at least 15 mg of morphine given intramuscularly (5). There is a rapid onset (2 minutes) and recovery occurs in a similar time after withdrawal. S d e p There is no significant depression of respiration or the protective reflexes. There is little, if any, depression of the circulation when used for analgesia in the pre-hospital setting. There is no effect on the pupillary reaactions. There is no incompatibility with other drugs which might be included in the patients’ previous medication or used in pre-hospital care. Comfort Neither nausea nor vomiting is a feature of Entonox used in pre-hospital care. Ease of administration The self-administration technique can be safely supervised by basic Emergency medical technicians and trained first aiders. Nevertheless, there are some limitations to the safe use of nitrous oxide/oxygen mixtures in pre-hospital care. The contraindications include: Patients with head injuries and reduced level of con-