Identification of Risk Factors Causing Difficulty in Laryngeal Mask Insertion
Condition: Anesthesia
Study type: Observational

Summary: 
      Even if the laryngeal mask (LM) is considered a very safe device with a low incidence of
      complications there may be situations where it is difficult to insert.

      Therefore it seems appropriate to carry out a prospective observational study that will
      identify the risk factors relating to the positioning of LM for the purpose of identification
      and prediction of them.

      From reading the literature and from the opinion of the experts with extensive practice in
      airway management (part of the Working Group "Management of Airway" of the Italian Society of
      Anaesthesia, Analgesia, Resuscitation and Intensive Care) some possible causes of difficulty
      in the insertion of laryngeal mask have been identified; these possible causes were listed in
      a report that will be distributed to the centers enrolled in the conduction of the study.

      1,864 patients will be enrolled in 8 Italian research centers to calculate the relative risk
      of each of the factors analyzed in order to identify those that, in view of the LM
      positioning, must be modified to reduce the risk of failure and, secondly, to identify the
      risk factors whose presence may contraindicate the use of the device and indicate the use of
      alternative methods for airway management.
    

Detailed description: 
      Backgrounds Since its introduction into clinical practice in 1983, the laryngeal mask (LM)
      has found a role in the daily practice of anesthesiologists, including its use as a primary
      device in the airway management in both elective and emergency and as an emergency approach
      to the management of difficult airways.

      Moreover, the insertion of the LM has become a common technique in the management of the
      airway, in particular outpatient surgery, where it is associated with a shorter recovery
      time, faster discharge and thus with a reduction of costs.

      Even if the LM is considered a device very safe with a low incidence of complications, there
      may be situations where it is difficult to insert.

      Aim of the study Some studies have concerned the causes that determine the difficulty in the
      insertion of an LM. They are retrospective studies and/or focused on the analysis of a single
      type of device.

      Therefore, it seems appropriate to carry out a prospective observational study that will
      identify and weight the risk factors relating to the positioning of LM for the purpose of
      identification and prediction of them.

      Methods From reading the literature and from the opinion of the experts with extensive
      practice in airway management (part of the Working Group "Management of Airway" of the
      Italian Society of Anaesthesia, Analgesia, Resuscitation and Intensive Care SIAARTI) some
      possible causes of difficulty in the insertion of laryngeal mask have been identified; these
      possible causes were listed in a report that will be distributed to the centers enrolled in
      the conduction of the study.

      The centers will be selected based on the fact that between the researchers is including an
      anesthesiologist part of the Working Group "Airway management" of SIAARTI to act as
      supervisor.

      Statistic Descriptive: for each quantitative variable will be reported mean, standard
      deviation, first and third quartiles, median, minimum and maximum. For each qualitative
      variable will be reported frequency and percentage of each category.

      Explorative: The association between each risk factor and the proportion of incorrect
      insertion will be evaluated only in a univariate analysis, using the relative risk and its
      confidence interval.

      Sample size: For a hypothesis test on the relative risk so specified H0: RR ≤ 1 H1: RR> 1 and
      considering an expected relative risk of 2, a proportion of 2.9% of the failures in the group
      of experts and a first type error equal to 5%, 832 patients per group are needed to ensure a
      power equal to 90%.

      The limit of significance is set at 5%.

      Expected results To calculate the relative risk of each of the factors analyzed in order to
      identify those that, in view of the LM positioning, can be modified to reduce the risk of
      failure and, secondly, to identify the risk factors whose presence may contraindicate the use
      of the device and indicate the use of alternative methods for airway management.
    

Intervention name(s): laryngeal mask insertion
Intervention type(s): Device
Intervention description(s): airway management with laryngeal mask
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        All consecutive patients submitted to insertion of laryngeal mask collected in 8 Italian
        research centers
      
Keywords: Laryngeal Masks; Ventilation; Risk factors