Kornilova L.N., Ekimovskiy G.A., Glukhikh D.O., Naumov I.A., Khabarova E.V.
It is well known that spaceflight in weightlessness is accompanied by the occurrence of illusions of spatial position or displacements of the body, vertigo, dizziness, disruption of coordination, and difficulty fixating on and tracking visual objects [Graybiel A. 1967-1980; Kornilova L.N. et al. 1983-2013]. Frequently this condition is perceived as uncomfortable, particularly with the presence of additional vegetative symptoms (increased sweating, nausea, vomiting, etc.) [Yuganov Ye.М. et al. 1968; Bryanov I.I. et al. 1979-1984; Thornton W. et al. 2012]. The disturbances that occur, referred to as space motion sickness, negatively affect both the health of crewmembers and the quality of their work performance in flight.
At the present time, medications are typically used to eliminate the symptoms of space motion sickness.
Pharmacological substances have a number of contraindications and side effects which can have a negative effect on various types of professional activity. The effect of their action lasts a limited amount of time and stops after the medication is eliminated from the system.
Thus the need is obvious to develop non-pharmacological methods of preventing and treating space motion sickness, since such methods does would have the aforementioned shortcomings. An important advantage to the non-pharmacological approach is its universality when applied to decreasing or eliminating the unfavorable symptoms of space motion sickness.
It is well known that people in extreme professions, such as mountain climbers, athletes, acrobats, and ballet dancers develop the capability to suppress unfavorable vestibular reactions at the moment high accelerations act on them, by developing a fixation reflex.
Attempts have been made by many clinicians to train patients with congenital or acquired vestibulopathies to suppress paroxysmal vertigo and vegetative episodes using a fixation reflex [Cawthorne T., Cooksey F., 1945; Dix M., Hood J., 1987; Hood J., Korries S., 1999; Blagoveschenskaya N.S., 1990; Likhachov S.А., Skliut I.А., 2000, 2008; Brandt T., 2014 et al.].
The existing approaches do not enable the development of the sensory-motor skill (fixation reflex) under conditions induced by vestibular and visual stimulation of vertigo. Therefore, specialists from the laboratory of VESTIBULAR PHYSIOLOGY at the Institute of Biomedical Problems developed and patented a “COMPUTERIZED METHOD OF PREVENTING AND CORRECTING OF UNFAVORABLE PERCEPTION AND SENSORY-MOTOR REACTIONS” (Russian Federation patent #2301622 dated 06/27/2007, Kornilova L. N. et al. – Fig. 1)
Fig. 1. Russian Federation patent #2301622, 2007
The innovation of this method is in creating a differentiated approach to the training of patients depending on their disease (type of vestibulopathy) and selecting the most effective means of training (visual, vestibular, or combined) for them using biofeedback.
During patient training, depending on the nature of the vertigo, dizziness or equilibrium disorder and of his/her disease (type of vestibulopathy), a series of training sessions is conducted to develop a fixation reflex using biofeedback, provided by the computerized using this method to record eye and head movements.
The computerized method of non-pharmacological training is based on:
- inducing unfavorable illusions and self-rotations (vertigo) and sensory-motor (nystagmus and equilibrium disturbance) reactions in the individual;
- training to correct or mitigate the induced negative reactions using a fixation reflex on an actual (visible on a screen) and imagined (invisible) target;
- using biofeedback to assess the effectiveness of the efforts applied (self-monitoring of training results) by the individual.
The method involves three types of training:
- visual method – to develop a fixation reflex against a background of moving visual interferences (diffuse spots/ellipses) to “irritate” the peripheral vision (Fig. 2);
Fig. 2. Visual method of training
- vestibular method – to develop a fixation reflex with active head movements;
- combined method – to develop a fixation reflex against a background of moving visual interferences and head movement.
Training is conducted until the negative reactions (vertigo, dizziness and equilibrium disturbances) the patient suffers from in daily life or during professional activity disappear or are significantly reduced. The therapeutic effect of the training is assessed through a follow-up clinical/neurological examination and the use of the computerized method of comprehensively assessing the state of vestibular function and visual tracking (Russian Federation patent #2307575 dated 10/10/07, Kornilova L. N. et al.). The indicator of training success is the suppression of experimentally induced negative reactions (full or partial) during the action of visual and vestibular stimuli while fixing the gaze on an imagined target.
Fig. 3. Russian Federation patent #2307575, 2007
The non-pharmacological computerized method for treating and preventing of vertigo, dizziness and equilibrium disturbances was tested in clinical conditions jointly with specialists from the Nervous Diseases Department of the I.M. Sechenov First Moscow State Medical University, the Academician Alexander Vein Clinic for the Treatment of Headaches and Vegetative Disorders, and the Federal Scientific Clinical Center of Otorhinolaryngology.
The results of the clinical work demonstrated that patients acquired the capacity to fixate on and hold the gaze on both real and imagined targets, thus suppressing (fully or partially) vertigo, dizziness, nystagmus, and equilibrium disturbances. It was shown that training effectiveness depended not only on the disorder (type of vestibulopathy), but also on the type of training selected. For patients with peripheral vestibulopathies, the most effective was visual training; for patients with central (cerebral) vestibulopathies, the vestibular method was best; and for patients with psychogenic vestibulopathies, the combined method was preferred.
Results of the clinical studies showed that patients acquired the skill to fixate and hold gaze equally on a real and imaginary target thus suppressing fully or partially vertigo, dizzines, nystagmus and equilibrium disturbances. It was shown that training success depended both on type of vestibulopathy and a selected method of training. Visual training appeared to be particularly effective for patients with peripheral vestibulopathies, vestibular training was good for patients with central (cerebral) vestibulopathies; combined, for patients with psychogenic vestibulopathies.
Fig. Training efficiency depending on the type of vestibulopathy:
A – peripheral, Б – cerebral, В – cerebral-peripheral , Г – psychogenic vestibulopathy
I – the visual method of training, II – the vestibular method of training, III – the combined method (mixed visual&vestibular)
Analysis of special questionnaires demonstrated that all patients with psychogenic vestibulopathies, 91% patients with peripheral vestibulopathies, and 80% of patients with central vestibulopathies subjectively noted “good suppression of vertigo/dizziness in everyday conditions” and “improvement in general adaptation to real life conditions.”
The effectiveness of the non-pharmacological computerized method has made it a good candidate for use both during the pre-flight training of ISS Russian crewmembers, and during spaceflight, to suppress the symptoms of space motion sickness. The suppression of negative reactions during flight using the fixation reflex has been successfully applied by crewmembers on board the ISS since 2013.