AN EVALUATION OF USING THE LARYNGEAL MASK AIRWAY FOR MOUTH TO MOUTH VENTILATION

Abstract

S114 INTRODUCTION: Mouth to mouth ventilation (MMV) is a technique recommended by the A.H.A. for basic life support. However a reluctance to perform MMV by healthcare professionals due to fear of transmission of HIV has been reported [1-2]. Skin contact may also be aesthetically unacceptable. The laryngeal mask airway (LMA) is now included in airway algorithms. It has been shown to be more effective than a bag and facemask for ventilation by nursing staff [3]. However it has not been assessed as an aid for MMV. We have undertaken a study to see if patients can be ventilated by MMV using the LMA when inserted by nursing stuff with trained in only basic airway management skills. METHODS: Five nurses with no previous experience of using an LMA volunteered to participate as resuscitators. They were first instructed on the manufacturers' technique of insertion of the LMA with a standardized lecture and then allowed to practice on a mannequin until proficient. Each resuscitator trained on two anaesthetized patients, with advice if required. They then performed MMV on ten successive patients each (n=50) as part of the study. Following IRB approval 50 ASA physical status I or II patients aged 18-80 yr, scheduled for general anesthesia, gave written informed consent. Patients with obesity, gastro-esophageal reflux or a suspected difficult airway were excluded. Anaesthesia was induced with fentanyl 2-3 mcg kg-1 and propofol 2 mg kg-1 rendering the patient apnoeic, and maintained with a propofol and fentanyl infusion. Once anaesthetized the investigator ventilated the patient with room air using a bag and facemask. When the SaO2 was 97% or greater with cardiovascular stability, the resuscitator attempted insertion and inflation of the LMA and then attached a bacterial/viral filter. They then gave MMV for three minutes. Oxygen was insufflated via a t-piece at 500 ml min-1 to compensate for the resuscitator's oxygen consumption. Expired air ventilation was judged successful if the chest visibly expanded and the SaO2 did not fall below 93% throughout the three-minute period. The time from picking up the apparatus to the first visible chest expansion was also measured. If the patient's SaO2 fell below 93% the investigator took over ventilation and the technique was deemed a failure. RESULTS: The range of patients' age and weight were 19-80 yr. and 38-105 kg respectively. There were 37 males and 13 females. Ventilation was successful in 48 patients. The LMA was inserted on first and second attempt in 42 and 6 patients respectively. The mean time for first successful ventilation with the LMA was 24.2 sec (range 13-32 sec). DISCUSSION: The skill of inserting the LMA proved to be easy to attain with a very high success rate of insertion. Mouth to mouth ventilation was correspondingly very successful. All the resuscitators expressed a preference of using the LMA for MMV compared with possible skin contact if not using it. We conclude from this pilot study that the laryngeal mask airway maybe a suitable aid for mouth to mouth ventilation to avoid skin contact and reduce the risk of transmission of infection. Further comparative studies with other equipment for MMV are warranted.