back to top arrow back to top arrow back to top arrow back to top arrow back to top arrow back to top arrow back to top arrow back to top arrow back to top arrow back to top arrow
Dizziness and Balance Disorders-Motion Sickness

Motion Sickness

(Air Sickness; Car Sickness; Sea Sickness)

Definition
Incidence
Risk factors
Symptoms
Treatment
Prevention of symptoms with behavior modification
Prevention of symptoms with medication
Prognosis and complications
Spatial disorientation in aviation
Incidence of spatial disorientation
Setups for spatial disorientation
Current modalities to prevent spatial disorientation

Definition

Motion sickness has plagued people for hundreds of years.  This sensation is felt to be caused by a sensory conflict between the two inner ears or between the ears and what the eyes, or our proprioception, senses around us.  Motion sickness can be induced by either physical motion or stimuli that result in perceived motion, such as computer displays or a car moving next to you in a parking lot.  Changes in pitch (up and down or vertical motion), roll (turning over) and yaw (angular motion about a vertical axis) can all cause motion sickness.  Low frequency oscillation can provoke motion sickness in land vehicles, ships and aircraft. 
Back to Top

Incidence

The incidence of motion sickness is common.  People in aircraft, on cruise ships or other vessels, in vehicles, as well as patients, or people who work at computer displays or in other visually provocative situations are exposed to conditions known to induce motion sickness. 

  • 40-60% of the normal population is motion intolerant
  • 50-80% of passengers on boats have reported motion sickness, depending on the roughness of the seas
  • 43% of passengers had susceptibility to motion sickness during road transport on coaches (the incidence is three times higher if they were not able to visualize the road)
  • 60-80% of inexperienced sailors reported motion sickness
  • 20-50% of experienced sailors have had motion sickness
  • 60% of pilots have had motion sickness after simulator exposure
  • 75% of astronauts report having motion sickness

Risk factors

A risk factor is something that increases your chance of getting a disease or condition.  Risk factors for motion sickness include:

  • Any motion provocative environment with lack of visual cues or complicated visual stimuli
  • Riding in a car, boat, airplane, train, or amusement park ride
  • Heightened level of fear or anxiety
  • Exposure to unpleasant odors
  • Poor ventilation

Back to Top

Symptoms

The most common symptoms associated with motion sickness include:

  • Visual and postural instability
  • Dizziness
  • Nausea and vomiting

Other symptoms include:
  • Sweating and excess salivation
  • Anxiety
  • Loss of color, especially in the face
  • Disorientation
  • Decreased cognitive function
  • Decline in performance of attention and concentration
  • Decreased motor skills

Back to Top

Treatment

Use of visual information may reduce motion sickness by 70-90%.  Symptoms of motion sickness usually subside soon after the motion stops.  However, in some people, the symptoms can last a day or more.  When oral medications are prescribed, they should be started 24 hours before experiencing a provocative situation.  For severe symptoms of nausea or vomiting, mediation may be given rectally or intravenously.  Back to Top

Prevention of symptoms with behavior modification

The following general measures may be taken to help avoid the discomfort caused by motion sickness:

  • Reduce anxiety and fears, particularly through methods such as cognitive-behavioral therapy and biofeedback
  • Use head and back rests to minimize movements and enhance proprioception
  • Maintain proper ventilation to decrease foul odors that may cause nausea
  • Stay occupied to distract the mind from thinking about motion sickness
  • Reading may worsen symptoms
  • Particular exercises, such as tumbling or jumping on a trampoline, may desensitize an individual prior to being in a situation that causes motion sickness

Individuals who commonly experience motion sickness on a plane should take the following preventive measures:

  • Avoid bulky, greasy meals and overindulgence in alcoholic beverages the night before air travel
  • Eat light meals or snacks that are low in calories in the 24 hours before air travel
  • Avoid salty foods and dairy products before air travel
  • Sit toward the front of the aircraft to lessen the visual mismatch
  • Sit in a seat near the wing because the ride is smoother in this location
  • Eat foods high in carbohydrates before air travel

Individuals with a tendency toward motion sickness on a boat should take the following preventive measures:

  • Passengers below the deck should keep their eyes closed – or consider going up to the front deck
  • Passengers on the deck should keep their eyes fixed on the horizon, visible land or a fixed stable horizontal line

Prevention of symptoms with medications

Medications that prevent motion sickness should preferable be started 24 hours before being placed in the provocative environment, but can still be effective taken 1 hour before travel.  Often for boat travel they should be used at least 2-3 days at the beginning of the trip, and therereafter as necessary, depending on the roughness of the seas.  The use of medication may however, cause drowsiness, decrease in alertness, a loss of performance on cognitive tasks, and decreased performance in motor skills.  These medications cause a decrease in labyrinthine function, decrease in the normal vestibular ocular reflex, and may result in impaired focusing and visual acuity. 

Medications frequently used include:

  • Transderm Scopolamine – a patch worn behind the ear.  It should be placed 1-2 hours before travel.  The drug effects last up to 3 days.  There is an oral form of scopolamine called Scopace.  Both forms require prescriptions. 
  • Promethazine (Phenergan) also requires a prescription.  The drug effects last between 6-8 hours
  • Cyclizine (Marezine) is an over-the-counter medication
  • Dimenhydrinate (Dramamine) is an over-the-counter medication
  • Meclizine (Antivert, Bonine) is an over-the-counter medication
  • Diazepam (Valium) is a prescription drug and can be very effective once the motion sensation has begun

In the past, the treatment was primarily drug therapy to prevent or lessen the symptoms of motion sickness.  With the new technology using an eye display and software technology (refer to www.Advitech.net), motion sickness can be prevented, lessened, or aborted in motion provocative environments.  This technology can benefit any industry where motion sensitivity affects human performance.  Back to Top

Prognosis and complications

While motion sickness has no long-term complications, the condition may be devastating for those in occupation s that involve constant movement, such as a flight attendant, astronaut or a ship crew member. 

The symptoms of motion sickness generally disappear quickly once the journey is over.  People who travel may also become accustomed to movement during a trip lasting several days.  Even those who travel often may improve from repeated exposures to the same type of stimulation.  However, people who become anxious before a journey often experience worsened symptoms of motion sickness and tend to require more formal interventions, such as behavior modification or mediation. 

Often when one has been on a cruise or in a motion provocative environment for a period of time and returns to stable ground, a sensation of motions, as if they were still on the boat is noted.  This is referred to as Mal de Debarkment, and is due to prolonged stimulation of the inner ear.  It is usually treated with labyrinthine suppressant medications, such as Valium and vestibular rehabilitation therapy.  Back to Top

Spatial disorientation in aviation

Spatial disorientation has been described as a failure of the pilot, or aircrew to sense correctly the position, motion or attitude (how the aircraft relates to the ground) of the aircraft or of themselves within the fixed coordinate system provided by the surface of the earth and the gravitational vertical.  During this time, they cannot perceive their own position, motion or attitude with respect to the aircraft, or the aircraft relative to other aircraft. 

We have the ability to perceive orientation in a 3-D space and this correct orientation occurs from sensory input from our vision, the vestibular apparatus of the inner ear, and receptors in the joints, skin, muscles and soft tissue (i.e. proprioceptive system).  The inner ear is sensitive to both linear and angular (rotational) acceleration.  Linear forces are like the gravitational forces of going up or down in an elevator, or accelerating in a vehicle.  The angular forces refer to turning the head or body rapidly in any direction.  The inner ear vestibular apparatus contains two principal sets of structures: the otolithic organs that detect linear acceleration (utricle – for horizontal motion and saccule – for vertical movement) and the semicircular canals that detect angular acceleration.  There are three paired canals in each inner ear (anterior, posterior and horizontal), oriented perpendicular to each other to sense head movement in three dimensions.  Back to Top

Incidence of spatial disorientation

  • The reported career incidence of spatial disorientation in aircrew is 90%
  • A report in 2003 reported 8% of surveyed pilots had experienced a severe episode of spatial disorientation adversely affective flight safety
  • 75% of astronauts experienced motion sickness
  • Up to 90% of astronauts experience spatial disorientation during re-entry and landing of the shuttle
  • There is one fatal spatial disorientation accident every 11 days
  • 5-10% of all general aviation accidents can be attributed to spatial disorientation; 91% are fatal
  • A FAA report stated that spatial disorientations causes 15-17% of fatal general aviation crashes annually
  • A USAF 15 year survey found that spatial disorientation resulted in 11% of crashes with a fatality rate of 69%

Back to Top

Setups for spatial disorientation

There are numerous factors for disorientation in aviation including those associated with the flight environment, flight maneuver issues, aircraft and crew factors.  Flying in low-light levels, in changing atmospheres and confusion of starlight and ground lights can cause in-flight illusions as well as lack of visual reference (i.e. clouds).  Vibrations (in 2-12 Hz range) decrease sensory-motor performance.  In-flight maneuvers contributing to disorientation include prolonged turning at constant rate, head movements under the above conditions or under increased G-loading, and sustained linear accelerations.  Aircraft factors such as inoperative instruments, inadequate instrumentation, use of night vision devices and lack of visibility of instruments for orientation, will also contribute to in-flight illusions.  Crew factors (i.e. fatigue, alcohol, drugs, experience, training and physical health) can be related to potential problems with spatial disorientation because of the effects on vestibular apparatus and the potential of inadequate central compensation. 

Most in-flight illusions are primarily either visual or non-visual.  Non-visual illusions constitute 41% of all spatial disorientation incidents.  Among non-visual factors, vestibular illusions predominate (i.e. otolithic and/or semicircular canal origin).  The most frequency spatial disorientation episodes were generally the “leans”. Back to Top

Current modalities to prevent spatial disorientation

  • Drug therapy – which can cause performance decrement
  • Instrument training
  • Standard Heads Up Display – provides attitude of aircraft only
  • Simulator training

Emerging technology provides pilot orientation relative to the aircraft and the ground with three axial orientation, an artificial horizon, and color directional indicators (www.Advitech.net).  It helps determine head and body position in space and thus aids in otolith/ssc stimulation stabilization.  It also aids in cervical proprioception, by providing visual input about the head position.  By providing stable artificial horizon and other visual information to the pilot or aircrew, the optokinetic reflexes can be stabilized.  The technology can assist in scenarios of motion hypersensitivities when conflicts arise between eyes, ears, and head position.  It has the capacity of working synergistically with the standard “Heads Up Display” instruments to prevent many of the in-flight illusions.  It can function separately from the aircraft computer system should a system failure occur.  The visual input information also provides faster information about spatial orientation than tactile data.  It also has an ability to provide faster recovery for “space re-adaptation” and rehabilitation of the dysfunctional vestibular system.

Back to Top