Force and Pressure Distribution Using Macintosh and GlideScope Laryngoscopes in Normal Airway: an in Vivo Study

Not Applicable

Completed

Brief Summary: Forces applied on soft upper tissues by different laryngoscope blades during direct laryngoscopy and intubation are considered to be major stimuli to cause serious damages to the patients. The aim of this study is to compare the force and pressure applied to soft tissue in order to achieve the same glottis view comparing direct laryngoscopy and videolaryngoscopy in vivo.

Detailed Description: Forces applied on soft upper tissues by different laryngoscope blades during direct laryngoscopy and intubation are considered to be major stimuli to cause serious damages to the patients, such as local injures to incisors, larynx and spinal column, or hemodynamic changes in heart rate and/or blood pressure due to autonomic nervous system stimulation.

In order to reduce risk of such injures, indirect videolaryngoscopy provides the advantage of an easier laryngeal visualization with less need for the mouth-pharyngeal-laryngeal axes alignment, thereby reducing the detrimental effects above mentioned.

The aim of this study is to measure the minimal force exertion to achieve not only glottis view but also a successful intubation, comparing GlideScope and Macintosh laryngoscope, in patients with normal airway conditions. Furthermore, The investigators measured the following parameters: pressure distribution upon the blade; time required to visualize the glottis; time required to complete oro-tracheal intubation.

Recruitment & Eligibility

Inclusion Criteria

Patients classified as American Society of Anesthesiologists physical status (ASA-PS) class 1 or 2
Patients whose intubation was associated with a Cormack-Lehane grade 1

Exclusion Criteria

younger than 18 yrs
older than 65 yrs
body-mass index (BMI) between 18 and 30
predicted difficult intubation according to SIAARTI (Italian Society Anaesthesia, Analgesia, Resuscitation and Intensive Care)

Arm && Interventions

Group	Intervention	Description
Indirect laryngoscope	Forces applied by laryngoscope	Includes cases in which the forces applied by GlideScope indirect laryngoscope onto soft tissue of the pharynx during glottis visualization and intubation were measured.
Direct laryngoscope	Forces applied by laryngoscope	Includes cases in which the forces applied by Macintosh direct laryngoscope onto soft tissue of the pharynx during glottis visualization and intubation were measured.

Primary Outcome Measures

Name	Time	Method
Force Applied and Pressure Distribution Upon the Blade of Laryngoscopes During Tracheal Intubation.	Force measurement is referred to an average of 45 seconds in patients scheduled to undergo elective surgery under general anaesthesia	The pressure distribution exerted upon the tissues by the blade was measured (in Newton)through pressure film transducers put on the blade of both direct and indirect laryngoscopes, in order to compare the two devices.

Secondary Outcome Measures

Name	Time	Method
Time Required to Visualize the Glottis and Complete Oro-tracheal Intubation	On average 20 seconds	Since the time needed for laryngoscopy and intubation could represent one of the major contributors to the stress response during these procedures, times to achieve the glottis visualization and to perform the entire intubation were recorded.