Motion Sickness, characterised by nausea, pallor, cold sweating and vomiting, occurs when humans are exposed to unfamiliar motion stimuli, either real or apparent. The earliest known reference to motion sickness was ‘sea-sickness’ but now this term encompasses symptoms induced by any form of motion or even in the absence of physical motion it is known to occur during simulator rides or while watching movies. As per the motion environment which induces the symptoms, there are diverse names of motion sickness viz. sea sickness, air sickness, simulator sickness, space motion sickness etc. Since motion sickness can afflict any person, without him/her being ‘sick’ or ‘ill’, the word ‘sickness’ here has colloquial connotations.
Hence this malady may more appropriately be called as ‘Motion Maladjustment Disorder’.
Motion Sickness occurs since there is perceived discord in integration of the conflicting positional and motion cues by the integrating centers in the brain. There could be active provocation e.g. Movements of the head to look inside or outside the cockpit; or passive provocation during flight manoeuvres. It is postulated that there is conflict between vision, vestibular apparatus and locomotion. Few psychological factors, like anxiety and poor stress coping, may also precipitate or aggravate this sickness.
The seven cardinal symptoms of Motion Sickness are:-
- Increased salivation
- Feeling warm/hot
The symptoms invariably are known to occur in a fixed order over varying period of time depending on the the individual’s susceptibility, severity and the provocative motion stimulus.
Speaking in specific reference to aviation, it is vital to remember that air sickness is a normal response of humans on exposure to aviation environment. Instead lack of response may be considered abnormal! More importantly, almost everyone adapts to it gradually. Hence, each pilot trainee, while in the air, must remember to avoid making unnecessary movements of the head. So also, focusing on planned sortie as per the briefing, and carrying on the tasks at hand helps alleviate the symptoms. Even when one may vomit during the sortie, (s-)he must not be disheartened, and continue to focus on the remaining sortie. So also it is known that majority of pilot trainees adapt within the first three or four sorties.
In the short term, though, especially during flying training, air sickness may have a bearing on learning and performance, where an air sick pilot trainee may not be able to imbibe the lessons during the sorties while being air sick. This may at times be disheartening in view of the wasted flying effort besides adding to the cost of flying training.
For the military trainee pilots, several nations have evolved ground based Desensitisation Therapy, using Barany’s Chair or similar rotating machines. Indians have included a combination of yogic postures for relaxation and physical exercise therapy for adaptation with success. An important point for the flying instructors is that after successful adaptation to air sickness the pilot trainee must be exposed to the flying task in a graded manner. The training must recommence with straight and level sorties, progressing to gentle manoeuvres and then followed by aerobatics. This is to help the individual retain (her)his adaptation, even if s-/he may sometimes have mild symptoms.
1. Ernsting’s Aviation Medicine. Rainford DJ, Gradwell DP (Editors). 4th Edition. Hodder Arnold, London 2006.
2. Fundamentals of Aerospace Medicine. DeHart RL, Davis JR (Editors). 3rd Edition. Lippincott, Williams & Wilkins, Philadelphia 2002.
Acknowledgement Image courtesy Wikimedia Commons