Clinical Practice Guideline

for

MOTION SICKNESS

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

 

Overview: Motion sickness is a common, even normal response to un-adapted or unfamiliar movement.  The term ‘motion sickness’ includes airsickness, seasickness, car sickness, space motion sickness, and other related entities.  It is not typically considered a medical disorder and can be induced in anyone with an intact vestibular system given the right type and duration of provocative stimuli.  The effects of motion sickness range from subtle performance deficit and distraction all the way to incapacitation.  Motion sickness is thought to occur as a result of conflicting inputs to the brain from visual, vestibular, proprioceptive, and rarely, auditory systems.  The term motion sickness is somewhat a misnomer, since it is possible to experience characteristic symptoms in the absence of unfamiliar motion, as in the case of “simulator-sickness,” “virtual-reality-sickness,” or “visually induced motion sickness.”  The terms ‘airsickness’ and ‘motion sickness’ will be used interchangeably during this discussion.

 

Signs and symptoms of motion sickness can include pallor, cold sweats, epigastric discomfort, nausea, vomiting, apprehension, hyperventilation, lightheadedness, drowsiness and apathy.  Nausea is typically the cardinal symptom.  Significant variability in susceptibility and adaptation exists in different individuals.  The affected individual may become distracted by the symptoms, leading to decreased situational awareness and performance decrements.  Some individuals experience significant amelioration after vomiting, while others may continue to experience symptoms for hours after the motion has stopped.  Most often, the brain is able to adapt to these mismatched sensations, and symptoms tend to decline or disappear with adaptation.  Most aviators become asymptomatic after repeated exposures to the flying environment.

 

Reportedly 0.6% of civilian airline passengers experience airsickness and more than 75% of troops on military air transports have become motion sick under extreme conditions.  US Navy studies determined that 63% of student pilots were sick on their first flight while only 15-30% did not experience motion sickness at all during training.  Non-pilot flight crews experienced symptoms on 14% of flights with vomiting occurring in 6%.  Females are almost twice as likely to suffer motion sickness as males, and the incidence declines with increasing age.  While most flyers accommodate to unusual attitudes, accelerations, etc., after repeated exposures, some will remain symptomatic.

 

In the U.S. Air Force, motion sickness is most commonly encountered among personnel in flight training.  Airsickness occasionally occurs in more experienced aircrew as they switch aircraft types, particularly in higher physical stress aircraft (heat, low level, limited visibility, etc).  Airsickness may also occur when a previously adapted individual returns to duty after a period of non-flying.  The USAF has defined two types of airsickness, active and passive, though it is recognized the phenomenon occurs along a continuum.  Active airsickness includes vomiting; passive airsickness does not include vomiting, but because of discomfort or nausea, results in significant deviation in the lesson profile or the student’s ability to complete tasks.

 

Prevention education and early intervention through the Airsickness Management Program (AMP) have proven to be effective in helping undergraduate pilot training (UPT) and undergraduate navigator training (UNT) students to overcome motion sickness (Table 1).  Prevention education includes instructing students during initial physiological training prior to participation in flying about the causes of airsickness and strategies to prevent, manage, and treat symptoms.  Prevention strategies include avoiding high-fat meals prior to flight, maintaining adequate hydration, limiting head motion during flight, watching the horizon, blowing cool air across the face, and performing slow diaphragmatic breathing.5, 8  Ginseng has been shown to be of some benefit for decreasing motion sickness symptoms, though clinical evidence is lacking.  In cases of intractable airsickness, desensitization training via progressive relaxation techniques coupled with incremental exposure to Coriolis stimulation (in a Barany chair or while flying) has been effective in up to 93% of affected individuals.  Some UPT/UNT students find more benefit from early desensitization with the Barany chair while others prefer the medication protocol to improve adaptation to the flying environment.

 

The role for pharmacologic intervention is limited in flyers.  Transdermal scopolamine or antihistamines such as promethazine and dimenhydrinate (Dramamine® and others) have been used to prevent/treat symptoms of airsickness.  Unfortunately, these agents are prone to sedation, impaired cognition, and short-term memory loss at therapeutic dosages.5, 7  Non-sedating antihistamines are unfortunately ineffective, probably due to their lack of central nervous system action.  Dextroamphetamine or ephedrine have been combined with either scopolamine or promethazine to limit side effects during USAF and USN military flight training but are authorized only for a total of three flights and only when the student is accompanied by a flight instructor.  Modafinil was thought to reduce motion sickness symptoms until a recent study found no benefit when used alone.  Newer agents are being studied, such as betahistine, but thus far have not shown significant efficacy.

 

Table 1 – Airsickness Management Program (AMP)

 

Phase

Airsickness Episode

Evaluations

Required Actions

 

0

None

AP

Pre-flight prevention education

 

I

1

FS

Assess compliance with Phase 0;

rule out medical cause; consider adjunctive pharmacologic therapy*

 

II

2

FS and consider AP or LSCC

Assess compliance with Phase I;

Progressive relaxation training**

 

III

3+

FS and AP, consider LSSC

Assess compliance with Phase II;

Physiologic adaptation training*** (Barany chair); Assess motivation to fly

Key:  FS:  Flight Surgeon.  AP:  Aerospace Physiology Personnel.  LSSC:  Life Skills Support Center.

Note:  Pilots undergoing any phase of treatment for airsickness will not fly solo.

 

*Pharmacologic intervention options:  transdermal scopolamine 0.5mg/ dextroamphetamine sulfate 5mg (Scop/Dex patch), given 1-2 hours prior to flight for 3 consecutive flights, 1 flight per day.  Alternative:  Scopolamine HBR 0.45mg in 15ml of elixir with dextroamphetamine sulfate 7.5mg, or other approved medication.

**Progressive relaxation techniques include diaphragmatic breathing, biofeedback, cognitive restructuring and imagery skills.

***Barany chair refresher spin recommended with any additional (>3) airsickness episodes.

 

 

Aeromedical Concerns: The effects of motion sickness can range from distraction to near-incapacitation.  The corresponding degradation of situational awareness and performance is incompatible with flying duties.  Most affected aircrew will adapt with repeated exposures to the flying environment.  Flying personnel who experience their first episode of airsickness should be evaluated by the flight surgeon to rule out organic or psychiatric etiology.  If no such etiology is found, the affected individual, if military, should be enrolled in the AMP (see Table 1) prior to determining a final aeromedical disposition.

 

Medical Work-up: Medical evaluation for aviators with motion sickness should include a history to include childhood and adolescent history of any type of motion sickness, history of vestibular disorders, motion sickness risk factors, previous experience with motion sickness and treatments attempted with results (to include any and all medications used).  How do symptoms affect mission and/or training?  The exam should focus on the CNS and ENT systems.  If military, discussion is needed about results of any desensitization treatment such as AMP training.  Also, if military, a statement from an aerospace physiologist is required to discuss training and conditioning.

 

Aeromedical Disposition:

 

Air Force: History of motion sickness experienced in aircraft, automobiles or watercraft after age 12 with any significant frequency in applicants for UPT and UNT (FC I/IA) requires a waiver.  Those with a history only BEFORE age 12 do not specifically require a waiver, but any history of motion sickness does need to be explored (per AFI 48-123).  Complete and thorough history of motion sickness should be submitted in the aeromedical summary.

 

Motion sickness in flying personnel is not cause for medical disqualification unless there is medical evidence of organic or psychiatric pathology.  UPT (FC I) and UNT (FC IA) trainees who have intractable airsickness after completing AMP are usually handled administratively because they are unable to meet syllabus requirements; they demonstrated “lack of adaptability” to the flying environment.  However, non-rated student fliers (FC III) enrolled in flying courses, who have intractable airsickness after completing the AMP, are usually medically disqualified and generally are not eligible for waiver.  Final determination of medical qualification in these cases is made by the MAJCOM/SG.

 

Rated aircrew (FC II) with intractable airsickness who do not become asymptomatic after repeated exposures to the flying environment and who fail desensitization training are dealt with administratively through a Flying Evaluation Board (FEB).  Prior to convening a board, these cases are typically reviewed by the MAJCOM/SG to rule out an organic or psychiatric etiology.  Many times these individuals are reassigned to their previous platform.  Airsickness requiring pharmacologic therapy beyond the AMP is disqualifying and not eligible for waiver.

 

Army: Army regulations stipulate that a history of motion sickness (994.6) resulting in recurrent incapacitating symptoms or of such a severity to require pre-medication in the previous 3 years is disqualifying.  Aircrew members with intractable motion sickness are considered disqualified and are normally terminated from aviation duties.  That said, promethazine (Phenergan) 25 mg. combined with ephedrine 25 mg. or L-scopolamine hydrobromide alone or in combination with dextroamphetamine (Scop/Dex) taken 1 hour prior to flight is permitted for up to 3 flights during training or for reacclimation of a rated aviator provided the patient is accompanied in flight by an instructor pilot.  Also, aviators who successfully complete a course combining desensitization, biofeedback training, relaxation training and psychological counseling either offered locally or through a sister service will be considered for waiver.

 

Navy: Aircrew with intractable airsickness are not physically qualified (NPQ), no waiver.  However, there is a Self-Paced Airsickness Desensitization (SPAD) program available at the Naval Aerospace Medical Institute (NAMI) which is an option prior to permanent grounding.  If the airsickness interferes with performance in flight, the patient will be evaluated by the flight surgeon to rule out medical causes (neurovestibular) and then referred to NAMI if appropriate.  The majority of aircrew become habituated to the stimuli and do not require treatment other than regular flying.  Others may benefit from a combination of desensitization, biofeedback training, relaxation training and psychological counseling.  Promethazine (Phenergan) 25 mg combined with dextroamphetamine (Dexedrine) 5 mg taken one hour prior to flight is permitted for up to three flights during training, provided the patient is accompanied in flight by an instructor pilot.  If symptoms recur following discontinuation of medication, this is the appropriate time for referral to the SPAD program at NAMI.

 

Civilian: sickness in the civilian flying environment may not be disqualifying if the airman can become desensitized to the symptoms.  There isn't a formal program like in the military services so the person will need to discuss remedies with their flight instructor.  Transderm scopolamine and the sedating antihistamines are unacceptable in the civil sector.  So, unless the airman can desensitze themselves they will need to be denied medical certification. 

 

Waiver Experience:

 

Air Force: Of 365 USAF aircrew members who were previously referred to the Aeromedical Consultation Service (ACS) between 1955 and 2001 with a diagnosis of motion sickness, 199 were recommended for return to flying status.  Five cases with a diagnosis of motion sickness have been evaluated by the ACS since 2001, four of which were found medically disqualified (one granted waiver) and one found medically qualified.

 

Review of AIMWTS showed 158 cases of motion sickness; 17 were FC I/IA, 31 were FC II, 1 was FC IIU, and 109 were FC III.  In the FC I/IA category,11 were deemed medically qualified and six were medically disqualified; for FC II 7 were returned (five with an associated diagnosis of esophageal reflux), 6 were medically disqualified, and 25 were found medically qualified and recommended for Flying Evaluation Board; and in the FC III category, 97 were medically disqualified.  The one FC IIU individual was an aerial gunner who was having significant motion sickness symptoms and asked to cross-train into the UAS career field and received a waiver to do so.

 

Army: Motion sickness is seen most often in the training environment and handled locally.  However, of the 16,852 rated aircrew who had a current flight physical in 2010, 34 carried this diagnosis.  Six of these were granted waiver after desensitization training and two had to be suspended.

 

Navy: The USN experience is that 13.5% of all flights will lead to airsickness in non-pilot aircrew with vomiting occurring in 5.9%.  Up to 63% of students were sick on their first flight, with only 15-30% not experiencing airsickness at all during their training.  Females are almost twice as likely to suffer as males and the incidence declines with age.  Treatment by biofeedback training, relaxation and psychological counseling achieves a success rate of 40%; when exposure to incremental  Coriolis effect and flying is included, the success rate rises to 85%.

 

Civilian: Statistical data is not maintained for this condition.

 

ICD 9 code for Motion Sickness

994.6

Motion Sickness, Airsickness

 

References:

 

AETC Instruction 48-102, Chapter 11, 16 Nov 2009.

 

AETC Instruction 36-2205, Vol 3 Chapter 3, 9 Dec 2009 and AETC Instruction 36-2205, Vol 6 Chapter 4, 14 Feb 2008.

 

AFI 48-123, G6 6.44.30.1.5 Airsickness in flying personnel, 24 Sep 2009.

 

Parmet AJ and Ercoline WR.  Fundamentals of Aerospace Medicine, 4th ed.  Ed. Davis JR, Johnson R, Stepanek J, Fogarty JA. Philadelphia, Williams and Wilkins, 2008:  195-203.

 

Golding JF and Gresty MA. Motion sickness. Curr Opin Neurol, 2005; 8(1):29-34.

 

Hoyt RE, Lawson BD, McGee HA, et al . Modafinil as a potential motion sickness countermeasure.  Aviat Space Environ Med, 2009; 80:709-15.

 

Benson AJ, Rollin Stott, JR.  Ernsting's Aviation Medicine. 4th ed. Ed. Rainford D, Gradwell DP, Ernsting J. London, Hodder Arnold,  2006: 459-475.

 

Yen Pik Sang FD, Billar JP, Golding JF, and Gresty MA.  Behavioral methods of alleviating motion sickness: effectiveness of controlled breathing and a music audiotape.  J Travel Med, 2003; 10:108-11.

 

 

 

Prepared by Drs. David Rogers and Dan Van Syoc

 

November 14, 2011