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- 1. Evaluation of mild motion sickness nauseogenic space and comparison with current standards: Should we go forward? ACCeSS Meeting 2008 The Atlantic Center for the Innovative Design and Control of Small Ships By LCDR P. Matsangas, M.Sc., Hellenic Navy [email_address]
- 3. Why?
- 6. HFR model (1974-1976) Model Characteristics Vertical Acceleration Only true motion MSI: % of people who vomit Two-hour nauseogenic period Nauseogenic frequency range 0.1 – 0.7 [Hz] Central nauseogenic frequency 0.167 [Hz]
- 7. Motion Sickness Adaptation example
- 13. Predicted MSI Proposed Model Characteristics Vertical Acceleration MSI: % of people who vomit Two-hour nauseogenic period Nauseogenic frequency range 0.05 – 0.6 [Hz] Central nauseogenic frequency 0.17 [Hz]
- 14. Model Validation True Motion Settings Proposed model HFR model MSI Comparison between Proposed and HFR models 1 2 3
- 15. MSI Accumulation Characteristics Vertical Acceleration MSI: % of people who vomit Two-hour nauseogenic period Nauseogenic frequency range 0.05 – 0.6 [Hz] Central nauseogenic frequency 0.17 [Hz]
- 16. MSI Habituation
- 17. MSI Habituation and Retention
- 25. Normalization & Linear Combination of 2 Sources of Error = MSI
- 26. Current Model (2008) in Detail
Notes de l'éditeur
- Motion sickness is a general term that describes a number of symptoms related to discomfort and associated emesis (vomiting) induced by numerous kinds of motions. Symptoms of motion sickness may be: Discomfort Headache Pallor Unwillingness to continue working Vomiting. A problem with nausea is that there exists a large inter-subject variability in the degree to which a person feels sick when sensing a provocative motion. Some people will be severely sick, others will feel sick but not to the extent of stopping their task. Some vomit once and then they feel OK, others continue vomiting until the provocative motion ceases. Finally, almost 5% never feel motion sick. Unfortunately, motion sickness effects are evident in numerous provocative motion environments, such as ships, aircraft, automobiles, and air-cushioned vehicles. The term “Motion Sickness” is a misnomer: “Sickness” implies that it is a type of disease, when in fact it is a perfectly normal response of a healthy individual without any functional disorders ; and it can be induced in simulators and Virtual Environments where there is no actual motion . Motion sickness occurs in environments with either actual or implied motion such as seasickness, airsickness, space sickness, and simulator sickness.
- The model used for the validation of the proposed work will be the HFR model. In a number of Human Factors Research (HFR) experiments (O’Hanlon & McCauley, 1974; McCauley, Royal, Wylie, O’Hanlon & Mackie, 1976) a regression model was proposed for MSI estimation. The alternative would be to use the observation data from large passenger ferries reported by Griffin (1990). We chose the first data because the latter are derived from environmental conditions and corresponding ships’ motions not precisely defined. The HFR model, although useful, has two drawbacks: Is not etiologic, and It refers only to vertical oscillation (only real motion, not vection) During the 2-hour nauseogenic period, the subject is seated inside a closed, lighted compartment (sea motion simulator), without being able to receive visual or auditory information, from the outside environment. Furthermore, the subject is assumed to be passive and stationary while exposed to externally induced motion.
- The model inputs are a) the external motion sensed by the vestibular system. Obviously we assume whole body motion, and b) motion of the visual surroundings sensed by the subject. ROF is the residual optical flow, which refers to the retinal slip due to less-than-perfect compensation of external motion Wr is the angular velocity of the visual surroundings (in space referenced frame)
- Evidence of habituation in a nauseogenic environment is considered to be a decline in MSI (the probability of emesis) (McCauley et al., 1976). The shown plot depicts the close correlation between the habituation process found in the HFR experimental data and the MSI predicted by the proposed model. The habituation procedure is a set of five daily two-hour exposures to the same motion stimuli. Proposed model output linearly adjusted for comparison purposes. HFR data parameters: ARMS=0.22 [g], f=0.25 [Hz] It is obvious that the two curves look identical, which is a promising result for more “tuning” of the model to experimental data.
- The retention process refers to the subject’s re-adaptation to the “normal” environment motion characteristics. In the presented slide you can see the predicted MSI when five daily two-hour exposures to the same motion are given to the subjects. The “retention” two-hour exposure is given to the subjects one week after the final day of the habituation exposures.
- The modeled independent parameters of MSI prediction are implemented parametrically, thus the model can be easily extended to include multiple nausiogenic combinations of environmental conditions The model’s predicted MSI as presented in this work, is derived without adjustment to the experimental data. We chose acceptable values for the parameters leading to a simplified and stable model (e.g. +1 or -1). Thus, the predicted precision may be easily increased. The timeline of MSI and the adaptation process is adequately approximated and the corresponding results are following the ones given by the HFR experiments. The error region (+ or – 5%) is small compared to other models on this topic. It is etiologic. Takes into account main human physiology subsystems which are known to contribute to motion sickness incidence. Therefore, it The HFR model is a regression approximation It’s linear and time invariant, thus it is easily analyzed. Of course, human physiology processes are non-linear, but in this work the linearity assumption has led to acceptable precision.
- Include motion in 6 degrees of freedom Implementation of all physiological systems contributing to motion sickness development For example, proprioception CNS non-linear characteristics time delays Non-linear detection of motion amplitude implemented at the sensor Ecological validity is a form of validity in an experiment. In order for an experiment to possess ecological validity, the methods, materials and setting of the experiment must approximate the real-life situation that is under study E xternal validity is the ability of a study's results to generalize.
- A convenient index of motion sickness severity is the Motion Sickness Incidence (MSI), which is the percentage of people who vomit when exposed to nauseogenic environment. Positive aspects of MSI metric Easily and objectively identifiable. Measures of the number and severity of symptoms during the progression of the syndrome are varialble and idiosyncratic, whereas emesis is an observable, behavioural marker. Negative aspects Does not take into account the numerous symptoms of motion sickness It is not related, in a straight-forward manner, to human performance
- The combined error, which is used to derive the estimation of the MSI, is the linear combination of the absolute values of the “gravity estimation” normalized error and the “residual optical flow” normalized error.