Gas Supply, Demand and Middle Ear Gas Balance -- Fly/Dive Simulation
Condition: Middle-ear Barotrauma
MeSH terms: Barotrauma
Study type: Interventional

Summary: 
      This study will determine if newly developed and more standard tests of Eustachian tube
      function can identify those persons who have ear pain (barotrauma) or develop middle-ear
      inflammation and/or fluid (barotitis) when they are exposed to rapid changes in air pressure
      as, for example, during airplane flights or scuba diving. Up to 150 adults and children
      (10-50 years old) who fly or dive at least 1-2 times and experience ear pain or develop
      middle-ear fluid during those activities and approximately 60 adults and children who fly or
      dive but do not experience these problems will undergo Eustachian tube function testing
      during simulated flight and diving.
    

Detailed description: 
      Subjects will be recruited who only experience symptoms or present signs interpretable as
      Eustachian (ET) dysfunction (ETD) when exposed to rapid changes in ambient pressure as, for
      example, during flights in airplanes (in the absence of a concurrent cold/active nasal
      allergy) or during free and tanked diving. In general, subjects presenting to physicians with
      these conditions are diagnosed with poor ET function (ETF) based solely on symptom/sign
      presentation. However, it is not known how to identify those persons who will experience
      these symptoms/signs at a future time which is the goal of this study or how to prevent those
      presentations in susceptible individuals. To calibrate the test protocol, 20 subjects/age
      ranges of 10-19, 20-29 and 30-50 years (total=60 control subjects) who are in good health,
      fly and/or dive frequently but report no ear-related problems on ascent or descent, will be
      recruited. One hundred fifty symptomatic subjects in general good health aged 10 to 50 years
      with the lower age limit chosen to assure good communication between the subject and
      investigators, will also be recruited. These and the control subjects will have intact
      tympanic membranes since subjects with non-intact tympanic membranes do not experience
      barotrauma but maintain ambient middle-ear (ME) pressures throughout a flight.

      A general history with a focus on the specific symptomatic complaints and the maneuvers
      performed in attempting to relieve any otologic symptoms during airplane flight/diving will
      be taken, an ear, nose and throat (ENT) exam, including tympanometry, done to confirm intact
      tympanic membranes and a disease-free ME and nasal exam done to rule out concurrent nasal
      inflammation. Then, sonotubometry, the 9-step test, tubomanometry and the "sniffing",
      Valsalva and Toynbee maneuvers will be done to establish baseline ETF. If a patulous (by
      observation of synchronized breathing and tympanic membrane movements) or physically
      obstructed ET (by an inability to transfer gas through the ET at normal driving pressures) is
      suggested by the results of these tests, the subject will be dismissed from further ETF
      testing and will be referred to their ENT physician or to the ETD clinic at Children's
      Hospital of Pittsburgh if they want to pursue a more complete workup to evaluate the
      underlying cause of the condition and possible treatment options. Those who are able to
      continue will have the ET stress test. Briefly, the presence/absence of ET openings by
      swallowing will be assessed by sonotubometry at stepped decreases from 2500 daPa (ref.
      ambient) to local ambient to determine the relative efficiency of muscle-assisted ET opening.
      The highest applied pressure at which the ET can be opened will be the outcome variable. If
      the individual completes the applied pressure sequence without experiencing a problem in
      opening their ET by swallowing or other maneuvers typically used by him/her to open their ET,
      the subject will have a simulated flight/dive relevant to their expected exposure.

      Flight Simulation: The standard flight simulation parameters are based on those for a Boeing
      747 but can be modified to simulate other, including personal, aircraft. For the simulations,
      we assume that the airport is at sea level, the maximum cabin pressurization is equal to the
      atmospheric pressure at 7000 feet and the ascent/descent rate is 350 ft/min (for the cabin
      altitude). With the subject seated comfortably in the pressure-chamber, chamber pressure is
      decreased from ambient to ambient minus 2280 daPa (gauge pressure=-2280 daPa) over a 15
      minute period, maintained at ambient-2280 daPa for 15 minutes (cruising) and then increased
      to ambient over a 15 minute period. The subject reports symptoms throughout and middle-ear
      pressure is measured bilaterally by tympanometry periodically.

      Diving Simulation: The standard dive simulation assumes sea level ambient pressure and, to
      avoid the possibility of the bends, is limited to a simulated maximum depth of 20 feet and a
      maximum "dive" duration of 1 hour. We make a first assumption that the diver rapidly descends
      to 5 feet at which point they attempt to equalize ME-ambient pressure and then proceed to the
      maximum depth of 20 feet within 5 minutes (These parameters can be modified depending on the
      diver's experience and the chamber pressure can be increased to simulate a dive to 30 feet).
      We also assume that the return to the surface is approximately 10 feet per minute. With the
      subject seated comfortably in the chamber, pressure is increased to 1500 daPa+ambient (gauge
      pressure =1500 daPa, approximately depth of 5 feet), the subjects middle-ear pressures are
      measured by tympanometry and any symptoms/signs evaluated. If these assessments are normal,
      the chamber pressure is increased to 6100 daPa+ambient (approximate depth of 20 feet for sea
      and fresh water), maintained at that pressure for 20 minutes and then decreased to ambient
      (ascent to surface). The rate of change in depth is set at 5 ft/minute. The subject reports
      symptoms throughout and middle-ear pressure is measured bilaterally by tympanometry
      periodically.

      The simulations will be interrupted at the first report of an inability to "clear" their ears
      by swallowing or other maneuvers typically used for that purpose. At that pressure, the
      subjects will again attempt to equalize the ME-chamber pressure by swallowing, and if
      unsuccessful, will attempt to open the ET using a Valsalva maneuver, jaw movements/rotations
      and voluntary yawning. If these maneuvers are unsuccessful, instrumented nasopharyngeal
      overpressures using the "ear popper"® or Otovent® devices will be tried. If successful, the
      simulation will be continued, else the chamber pressure will be reduced to atmospheric and ME
      pressure equalized with ambient pressure. Then, only in subjects entered as symptomatic
      subjects, a video-nasoendoscopic exam of the nasopharynx will be performed to diagnose nasal
      and nasopharyngeal pathologies and physical obstruction of the ET orifice.

      All subjects in the symptomatic group who pass the simulation without symptoms/signs of
      barotrauma will be retested using the appropriate simulation on a second day to confirm
      "symptom-free" flights/dives. For those subjects who fail this test and/or cannot complete
      the simulation without otologic symptoms/signs, we will refer them to their physician or to
      the ETD clinic if they want to pursue further work-up and treatment. We expect that all of
      the control subjects will successfully complete both the test protocol and simulation while
      the majority of subjects reporting flight/diving related symptoms will fail the stepped ETF
      test and not be able to complete the simulation without symptoms/signs of ME barotrauma. The
      sensitivities, specificities and accuracies of the ET stress test and the simple ETF tests
      done at baseline with respect to predicting a failed/successful simulation will be
      calculated.
    

Intervention name(s): flight/diving simulation; ET function testing at ambient pressure; nasal video-endoscopy
Intervention type(s): Other; Other; Other
Intervention description(s): measurement of ET function during simulated flight/diving in pressure chamber; ET function testing at ambient pressure using sonometry, tubomonometry, 9-step test, maneuver sequence; examination of nose, nasopharynx,and Eustachian tube orifice
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: barotrauma; barotitis; middle ear; flying; diving; Eustachian tube