UMOX™: A New Device for Preoxygenation
Condition: Healthy
Study type: Interventional

Summary: 
      Background - Preoxygenation is performed before general anesthesia to increase the oxygen
      reserves of the body and prolong the safe period of apnea without hypoxia. However, it is
      often impossible to obtain a perfect face mask fit, and optimal end-tidal fractional oxygen
      concentration (EtO2) are not attained. The investigators designed a new oropharyngeal
      preoxygenation device, UMOX™, to avoid leaks during preoxygenation. In this study, the
      investigators compared the efficacy of UMOX™ with that of a conventional face mask.

      Methods - In 50 healthy volunteers breathing 100% oxygen from a circle absorber system for a
      5 minute-period, the investigators compared preoxygenation using the 1) a conventional mask;
      2) UMOX™ without any instruction; 3) UMOX™ with instruction on mouth breathing; and 4) UMOX™
      with a nose clip, in random order. Each subject underwent all steps with a 10-minute rest
      period of room air breathing between each step. Inspired and end-tidal respiratory gases were
      measured every 10 seconds. EtO2 variation was analyzed using Anova.
    

Detailed description: 
      This study was as a single center, crossover, randomized trial. Following approval from
      research and ethics committee from our hospital and written consent from healthy subjects
      recruited, 50 consenting volunteers were enrolled over a three-month period, from: September
      29, 2008 to November 5, 2008.

      Subjects enrolled were of both genders, smokers and non-smokers, American Society of
      Anesthesiologists (ASA) physical status I or II, 18 to 65 years old. Nonrecruitment depended
      on the presence of any craniofacial abnormality, facial hair (beard or moustache) or absence
      of teeth. Well-controlled non-severe asthma was not a criterion for exclusion.

      The trial was conducted in an operating room, using the Dräger Fabius GS (Dräger, Canada),
      anesthesia machine in a usual set up with the operating table. The investigators used a,
      patient circuit system consists of 1.5-L lime soda absorber connected to disposable
      corrugated tubing and a 2-L breathing bag. Gases were analyzed through a Marquette Medical
      Systems™ SAM module (GE Healthcare), volumes monitored with a GE Respirator Mechanics-M (GE
      Healthcare) and SpO2 measured with a Nellcor™ (Covidien) pulse oximetry positioned on a
      finger. Preoxygenation procedures were explained to the subjects and ample time was allowed
      so they could become familiar with the mask and mouth piece. Set up for the measure was
      conducted by the same experimenter. Subjects laid supine and preoxygenation was performed
      with fresh gas flow: 100% oxygen (O2) 10L/minute, administered trough facemask or mouth piece
      sequentially in a random order. Randomization was established with a random assignment table
      (ww.randomization.com). The envelope was open as the subject entered the operating room (OR).
      At the beginning and between each step, the anesthesia circuit was flushed with 100% (O2).
      Each subject went through all steps in random order, each requiring a 5-min period of: 1)
      tidal breathing using the facemask (TVFM); 2) tidal volume breathing with the UMOXTM
      mouthpiece (TVMP); 3) tidal volume breathing with the UMOXTM mouthpiece and verbal
      instructions to favor mouth breathing (TVMPMB); (4) tidal volume breathing with the UMOXTM
      mouthpiece and a nose clip (TVMPNC). The experimenter conducting the steps instructed
      participants to create a seal with their lips around the mouthpiece and readjusted the
      facemask when the subject signalled a discernable leak. Each step was interrupted by 10
      minutes of breathing normal room air to allow for return to original respiratory status.
      Continuous recording of experimental measures, displayed on the anesthesia monitoring system,
      was done on digital films (Canon PowershotS5 IS™). For the purpose of our trial, 10 seconds
      intervals were considered adequate for following preoxygenation trends. End-tidal O2 was
      measured continuously for 5 min. We have also evaluated the level of satisfaction of the
      subject with each technique using a 1-4 scale.Participants were asked to asses their comfort
      by showing the associated number with their fingers. Finally we described the performance of
      the facemask ventilation technique as reported by the experimenter on a scale of 1 to
      4.Primary outcome was the end-tidal O2 at the end of the 5-minutes preoxygenation period.
      Secondary outcomes included endtidal O2 as a function of time, the number of subjects
      reaching at least 87% EtO2, subject satisfaction and ease of ventilation.

      Based on the few studies available on different preoxygenation technques, the end-tidal
      oxygen fraction standard deviation can range from 5% to about 20% depending on the device
      used for preoxygenation3,4,14,15. Assuming a 12% value for standard deviation, sample size
      calculations were made for Type I and Type II errors of 5% and 20%, respectively (power of
      80%). From these numbers and taking account that we would rely on multiple comparisons, the
      power analysis suggested that 50 subjects would allow us to find a difference between groups
      around 9%. The 9nvestigators analyzed the EtO2 final value with one-way ANOVA followed by the
      Tukey's Multiple Comparisons test. Percentage of participants reaching at least 87% EtO2 are
      described with survival curves compared with Kaplan-Meier log rank test. Tolerance is
      presented using Kruskal-Wallis with Dunn's Multiple Comparisons test.
    

Intervention name(s): Mouthpiece (Umox); facemask
Intervention type(s): Device; Device
Intervention description(s): Device used to perform preoxygenation in the operating room context
Other intervention name(s): Umox
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Preoxygenation; Device; Tolerability; Efficacy