Abstract:
A fitness for duty (FFD) testing device and method for determining fitness for duty using a testing unit that is held in two hands by a human test subject. Two handles are provided for holding the unit which includes a video screen with an image of a moving shape on a surface. The position of the shape on the screen is determined by the orientation of the hand-held unit. Tilting the unit by the test subject results in the shape moving on the screen. The device computes a score which can be compared to historical results for the test subject, and to results from a larger population base. The FFD device may be programmed to present increasing levels of difficulty as test subject learning occurs, and can receive and provide data to external computing, printing, display, network, or storage devices.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to devices for measurement of human impairment, which might occur as the result of low-level alcohol or drug exposure and hangovers among other physiological factors, and more particularly to a handheld fitness for duty (FFD) tester which adapts for human learning during the test and determines a test score which may be used to determine the test subject&#39;s fitness for duty. 
     The definition of FFD tests are well-documented by Burns and Hiller-Sturmhofel (“Alcohol&#39;s Effect on Cognition”, Alcohol World Health &amp; Research, Vol. 19, No. 2, 1995), but to date, no suitable instrument has been available to accomplish these tasks. The performance criteria for such an instrument include sensitivity to small changes in blood alcohol concentration (BAC), detection of concentrations of BAC below 0.05 percent, reliable and repeatable results, ease and simplicity of test administration, reasonable price, adjustment for learning when a test subject uses the device on a routine basis, establishment of a baseline for each person tested, providing a comparison against a database of similar individuals, updating each individual&#39;s baseline to account for learning, and measurement of job or safety-related skills. 
     Significant work has been carried out by Jonathan Howland, et al. at Boston University School of Public Health which indicates significant performance effects for low-level alcohol exposure (0.04 gm % BAC) for persons performing on diesel engine and ship bridge control simulators (“A Random Trial on the Effects of Alcohol on Safety Sensitive Occupational Performance: Simulated Merchant Ship Handling” (Draft), Jul. 6, 1998). Howland&#39;s preliminary findings tend to confirm earlier Boston University survey data from the workplace drinking study (“Employee Attitudes Towards Work-Site Alcohol Testing”, JOEM, Vol. 38, No. 10, October 1996) which indicate an association between drinking alcohol at lunch (low-level exposure) and workplace performance impairment or safety problems. Studies using flight simulators, automobile simulators, and industrial task simulation also indicate impairment due to low-level intoxication or hangovers. Furthermore, research appears to indicate that neither the exposed subjects nor their co-workers are aware of this impairment. 
     From a safety management perspective, these findings pose problems because the effects of low-level alcohol exposure and hangovers are difficult to detect for at least two reasons. First, detection is difficult because affected workers and their co-workers are unable to discern impairment at low-levels of exposure, and secondly, alcohol may have residual impairing effects even when BAC is zero. 
     Managers in industry, commerce, and government are very much in need of a system that will effectively and efficiently evaluate an employee&#39;s fitness for duty without intrusive testing, and regardless of cause (e.g. alcohol, illegal drugs, lack of sleep, or side-effects of prescribed medication). Such an FFD testing system would have application to a broad range of industrial settings involving safety-sensitive work such as aircraft pilots and mechanics, nuclear power plant workers, train engineers, truck drivers, aircraft controllers, ship bridge or engineering personnel, or surgeons. 
     Finding a rapid and simple FFD device or test would potentially have broad application in these safety-sensitive industries, and could solve the problem of detection and confirmation with employees of any low-level impairment without unduly exposing either the employer or employee to legal liability for the testing procedure or accidents resulting the low-level impairment. Such a system could possibly facilitate self-imposed behavior modifications or seeking of substance abuse counseling by employees who repeatedly fail to pass the FFD test. 
     The commercial applications of such a FFD test are very large, and present a significant market in response to high, pent-up demand for such a device by the airlines, railroads, trucking companies, and ship operators, among other industries and commercial or governmental organizations. 
     2. Description of the Related Art 
     The use of a pressure plate was considered to determine neuromuscular responses. U.S. Pat. No. 4,195,643 discloses a pressure plate for testing lameness of horses suffering from arthritis, septic tendinitis, and hair-line fractures. The device uses time and frequency-domain analysis to determine physiological conditions of the animal under test. A block diagram of this approach is shown in FIG.  1 . 
     U.S. Pat. No. 5,388,591 expands the application of the pressure plate to the analysis of the human postural control system by employing statistical analysis of the random displacement of the center of pressure of the subject while standing on the pressure plate, as depicted in FIG.  2 . 
     Although use of a pressure plate may initially appear useful for FFD testing, there are drawbacks to its use. From a safety perspective, requiring a subject to stand on a platform 40 cm by 40 cm which is several centimeters high may create a potentially unsafe condition, particularly if the individual under test has poor balance due to drug or alcohol impairment, poor health, or other physiological factors. This problem may be exacerbated if the subject is asked to balance on one foot to perform a test having the greatest sensitivity to balance. In addition, the pressure plate does not have a means to “push” the subject to higher levels of work effort; the pressure plate test is simply a measure of balance. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     With these limitations of the prior art in mind, it is an object of the present invention to provide a novel, non-intrusive, practical, and relatively inexpensive FFD testing device and method. 
     It is also an objective of the present invention to provide a testing device which requires conscious effort beyond balance alone, which uses visual inputs and requires two hands for execution, and a test method which uses this device that is easy to administer. 
     It is further an object of the present invention to provide a testing device and method which uses neuromuscular, vestibular, visual, and cognitive skills, like the demands of tasks in the workplace, and which provides repeatable and easily measurable results. 
     It is still further an objective of the present invention to allow the test subject to work in its most advantageous mode to carry out the test and to eliminate any concern over left or right-handedness of the test subject. 
     It is yet further an object of the present invention to adapt to human learning during conduct of the test and to increase difficulty of the test in response to the learning by the test subject. 
     It is another objective of the present invention to store and compare test results of the individual test subject and of a larger population base of test subjects. 
     It is further another object of the present invention to be able to uniquely identify each test subject. 
     It is still further another objective of the present invention to be able to program initial test conditions and dynamic characteristics of the test. 
     It is yet further another object of the present invention to provide output to external devices or databases, and to receive input from external devices or databases. 
     It is an additional objective of the present invention to utilize existing, commercially available processing electronics, and to use software algorithms based on basic physical principals. 
     In accordance with the claimed invention, a FFD testing device and method is thus provided which can meet the foregoing objectives. 
     The FFD test device and method are used to determine the fitness for duty of employees in industry, commerce, government, research, and medical professions. The device includes a hand-held unit which is used in an upright, standing position and is held by the person being tested with both hands in front of their body. The hand-held unit contains electronic sensors for determining the orientation of the hand-held unit in space or in the earth&#39;s gravitational field. Upon initializing the device, an image of a ball or other shape, a “virtual” image, appears on a screen in the hand-held unit. The goal of the test is to maintain the position of the ball at a target position, such as in the center of the screen, by tilting the hand-held unit. The ball appears to “roll” on a “virtual” surface in simulated response to gravity, depending on the unit&#39;s orientation. Any tilting of the device from this plane by the human test subject results in the ball moving from the target position as if gravity were acting on the ball. 
     The FFD testing device computes a test score based on the test subject&#39;s ability to maintain the ball in close proximity to the target position, and the device establishes a baseline of historical test results of the test subject and test results of a larger population, both of which may be compared to the test subject&#39;s score. In addition, the FFD testing device can dynamically adapt the difficulty of the test as the test is being conducted in order to account for learning and increased familiarization with the device by the test subject. Such “pushing” of the test subject to higher levels of work effort is accomplished by introduction of sudden transients of ball position, or virtual surface characteristics which would act to stress the test subject beyond the typical 32 millisecond (31.25 Hz) neural response of the human muscular system. 
     These and other objects and advantages of the present invention will be apparent to those with skill in the art from a reading of the detailed description of the preferred embodiments, which is given with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a prior art device in block diagram form for measuring and analyzing input forces using a force plate system as the transducer. 
     FIG. 2 shows a prior art apparatus in block diagram form for analyzing the human postural control system. 
     FIGS. 3A and 3B are top and side exterior views of an embodiment of the present invention. 
     FIG. 4 shows a block diagram of the first embodiment of the present invention. 
     FIG. 5 shows a block diagram of a further embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 3A-3B, a first embodiment of a hand-held FFD testing device for determining the fitness for duty of a human test subject may include a hand-held enclosure  10  having a top and at least one exterior side surface  12  to which are attached at least two handles  14  on generally opposite radial sides of the enclosure  10  and that are each to be held by a different hand of the human test subject. However, these handles may be adjustable in a variety of ways, i.e. either into or away from, fore and aft, or up and down relative to the enclosure to accommodate an individual test subject&#39;s grip, as depicted by the arrows in FIGS. 3A and 3B. A main power switch  16  may be provided to activate the device by providing power to internal electronic processing and display components discussed below, and a push-button test initiation switch  18  may also be provided for use by the human test subject to initiate the FFD test. The top of the enclosure  10  includes a display screen  20  discussed below. 
     The enclosure  10  houses an accelerometer  22  (FIG. 4) having at least two independent outputs  24  representing acceleration components along at least two perpendicular axes, and preferably having three independent outputs representing acceleration components along three orthogonal axes. The outputs  24  are provided to an analog-to-digital converter (ADC)  26 . Outputs  24  include data indicative of the orientation of the enclosure  10  relative to a frame of reference, such as the earth&#39;s gravitational field. 
     The accelerometer  22  may be of any commercially available type, such as potentiometric, reluctive, strain-gage, servo, piezoelectric, mechanical gyro, fiber-optic gyro, and ring-laser gyro type, however it preferably is a Crossbow Technology, Inc. Model CXL02LF3 Triaxial Accelerometer, having a range of +/−2 g in each axis with an analog output of 0 to +4 volts for each axis, and a bandwidth of 0-125 Hz. in all three axes. The digital outputs from ADC  26  provide data which represent the acceleration seen by the accelerometer  22  that are preferably digitized to a 12-bit resolution at 250 Hz., and provided as inputs to a processor  28 , which is preferably a digital microprocessor housed in the enclosure  10 , or in an external system. 
     Processor  28  receives and analyzes the accelerometer data and provides fitness for duty test results based on this information by using software algorithms implementing well-known integration techniques to derive positional information from the acceleration data. By using standard equations of motion for velocity and displacement using calculated acceleration, i.e. v=v 0 +at, and x=x 0 +v 0 t+½at 2 , the processor determines the position of an image of a moveable shape  30 , preferably a standard geometric figure such as a ball, on the screen  20 . 
     The screen  20  is preferably a liquid crystal display (LCD), however, it may be a thin-film electroluminescent display, a cathode ray tube, or a plasma or gas panel type display mounted on the handheld unit or an external unit. 
     Preferably, the shape  30  is on a surface  34  which can be varied, e.g. rough or smooth, or of differing contours, e.g. flat, conic section, undulating, or spherical, so as to allow the shape  30  to have different movement responses. Movement of shape  30  may be subjected to viscous damping or programmed with non-linear characteristics, and a simulated gravitational constant may be changed. Processor  28  simulates movement of the shape  30  in a plane parallel to the surface  34 , and may simulate movement of shape  30  in a direction perpendicular to the surface  34  so as to provide a three-dimensional visual effect on a two-dimensional display  20 . 
     The surface  34  may be bounded by a peripheral boundary wall  36  that may have various interior contours including arcuate and linear. The shape may “bounce” off the wall  36 , or off of the exterior edges of screen  20 . In the latter event, the wall  36  may merely be a measuring line for evaluating performance. The peripheral boundary wall  36  preferably is equidistant from the center of screen  20 , however the placement of the boundary wall  36  may be varied by the test administrator. 
     These factors are accounted for by the processor software in calculating the vector components of acceleration due to gravity “virtually” acting on the shape  30  as the enclosure  10  is moved by the test subject. These acceleration components are then used in the equations of motion to determine velocity and displacement of the shape  30  on the surface  34 . The calculated acceleration components are dependent on the acceleration due to gravity, the tilt of the enclosure  10 , the position of the shape  30  on the surface  34 , and the type of surface  34  used for the test. 
     The processor  28  may also determine a test score which may be displayed on the screen  20 . The test score may be determined by statistical evaluation of the movement of shape  30  about a target position  38  on the surface  34 , or movement of the shape along a defined path shown on the screen  20 . Other measures of movement of shape  30  may be used, including average straight path length, maximum extent of movement, percent within a defined limit, time without movement, and the like. Preferably, the target position  38  is the center of the screen  20 . For example, the statistics used in the evaluation may include the mean distance of the shape  30  from the target position  38  or from the defined path, as well as other parameters such as the standard deviation, kurtosis, and skew of these measures of movement of the shape  30 . These additional statistical parameters provide a fine, detailed analysis of the FFD test subject&#39;s performance. 
     The indicators for target position  38  and the shape  30  may be similar or dissimilar figures that visually facilitate placement of the shape  30  relative to the target position  38 . Shape  30  may include a directional arrow indicative of the direction of movement of shape  30  that may be determined by processor  28 . A more sophisticated FFD test may include two shapes  30  on surface  34 . 
     The processor  28  preferably employs frequency-domain techniques, such as Fast Fourier Transform (FFT) techniques for further evaluation of the test subject&#39;s response, although other suitable algorithms may be used to compute frequency domain characteristics. This evaluation preferably would include spectral and cross-spectral analysis of the data from the accelerometer  20 , or positional data derived from the accelerometer data. 
     With reference to FIG. 4, the invention may also include a communication port  40  that allows an output from the processor  28  to be provided to external devices or a computer network, or to provide data to the processor  28  from any suitable peripheral device. The communication port may be of RS-232 serial, parallel, infra-red (IR), radio frequency (RF), universal series bus (USB), or small computer systems interface (SCSI) type, but preferably the communication port is of RS-232 serial type. 
     The invention may also include an initialization unit  42  connected to the processor  28  to establish desired initial test conditions and desired dynamic test parameters for the device, and to uniquely identify the human test subject. 
     The desired initial test conditions could include test duration, elasticity of the shape  30 , size and shape of the shape  30 , shape of the surface  34 , shape of the peripheral boundary wall  36 , dynamic reflection characteristics of the peripheral boundary wall  36 , and simulated friction effects between the shape  30  and the surface  34 . To change the difficulty of the FFD test, dynamic test parameters could be pre-programmed to include random transient changes in position of the shape  30 , periodic changes in position of the shape  30 , changes to the shape and size of the wall  36 , changes to the value used for the simulated gravitational constant, and changes to the surface  34 . 
     The initialization unit  42  may comprise a magnetic identification card swipe device, or a keyboard for entry of test subject identification data and a password, or a fingerprint identification device for additional security. The initialization unit  42  may be integral with the enclosure  10 , or separate therefrom and communicating with the processor  28  through the communication port  40 . 
     Preferably, the accelerometer  20 , the ADC  26 , the processor  28 , the power switch  16 , the push-button test initiation switch  18 , and the communications port  40  are all located within the hand-held enclosure  10 . 
     In an alternative embodiment shown in FIG. 5, the accelerometer  22  may be replaced with a level sensing unit  44  within enclosure  10  for determining the level of enclosure  10  with respect to a plane tangent to the earth&#39;s surface. The level sensing unit  44  may be a mechanical gyroscope, fiber-optic gyroscope, ring-laser gyroscope, liquid potentiometer, or preferably, an electric output, two-axis spirit-level type device. 
     Output from the level sensing unit  44  is provided to an analysis unit  46 , also within the enclosure  10 , which receives and analyzes the level-sensing data and provides fitness for duty test results based on analysis of this information as in the first embodiment. 
     The initialization unit  42 , in concert with the analysis unit  46 , may further adjust the test difficulty in response to learning by the human test subject as the test progresses. The test difficulty is partially determined by the desired initial test conditions and the desired dynamic test parameters which are established by the test administrator or test subject. Learning by the test subject may be indicated by an improving trend of test results. Ideally, for the device to provide meaningful results, one test subject should have relatively consistent results, assuming the test subject is fit for duty each time the test is taken. Of course, some learning is to be expected and thus, in response to an improving trend, the analysis unit  46  may take steps to make the test more difficult, such as speeding up the shape movement, changing surface contours, etc. in order to compensate for learning so that the computed test score may be adjusted to be a relatively consistent number before and after learning has taken place. 
     A storage unit  48 , located within the enclosure  10  and preferably a semiconductor memory type, may be connected to the analysis unit  46  to provide historical test data and level-sensing data storage. Preferably, the storage unit  48  stores current test results and historically achieved results for future comparison of test results for the particular individual under test, or for test comparison among a wider population of test subjects. 
     The communication port  40  may be connected to an auxiliary test support unit  50 , such as a general purpose computer, printer, plotter, or memory storage device, a network, or the internet for further manipulation and presentation of test results. 
     In addition, to minimize “cheating”, a proximity detector  32  (FIGS. 3A,  3 B, and  5 ) may be located on the surface of the device enclosure to ensure the test device does not contact the test subject&#39;s body, except at the handles. The proximity detector indicates when the test subject attempts to stabilize the device by resting it on the torso, legs, etc. The proximity detector may be a sonic, capacitive, RF or other appropriate type of detector which provides a signal to the processor  28  in the first embodiment, or to the analysis unit  46  in the second embodiment. The proximity detector may trigger an aural or visual alarm, and the test may be restarted or stopped when “cheating” is detected. 
     Experimental Results 
     The FFD device, in prototype form, has been used at the Maine Marine Academy in conjunction with tests using an automated ship&#39;s bridge simulator. The objectives of the bridge simulator tests are to determine the effects of alcohol dosing of subjects to determine a safe maximum limit of alcohol concentration in the blood stream. The tests were conducted in March, 1999 under protocols established by the National Institute of Health. 
     Half of the subjects (five individuals) were dosed to an alcohol blood concentration of 0.04% by body weight (“alcohol group”). The other five subjects (“placebo group”) were told they were dosed, but did not receive alcohol. 
     The test series lasted two evenings. During the first evening, all the subjects received instructions concerning the FFD operation and testing. All subjects had previously received instruction on the bridge simulator and were proficient in its use. Each subject carried out three, one minute tests with the FFD instrument. Test subject scores were determined for the average distance from the center target. 
     The subjects were each given a drink with an additive to mask the presence of alcohol, however, there was no alcohol in this first drink. After one half hour, the test subjects were given a bridge simulator test which lasted approximately one half hour. At the end of this test, each subject again carried out another set of three, one minute tests with the FFD device. 
     During the next evening, the same protocol was used, except the drink was dosed with alcohol for the alcohol group. All test subjects carried out FFD tests before and after the bridge simulator test. 
     Since there can be considerable learning during the first use of the FFD device, the first night&#39;s scores were not used for this analysis. During the second night, the average score for the test before the simulator test was subtracted from the average score for each subject after the bridge simulator test. 
     The average distances of placebo and alcohol-dosed subjects were averaged together for the placebo and dosed groups. A T-test was used to compare the average distances for pre and post-test scores. The means were found to be statistically significant. The placebo mean difference was −0.536, and the dosed alcohol mean change was +0.518, P=0.045. The following table summarizes the experimental results. 
     
       
         
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Pre- 
                 Post- 
                   
               
               
                   
                 Group 
                 simulator 
                 simulator 
                 Difference 
               
               
                   
                   
               
             
             
               
                   
                 Alcohol 
                 5.9 
                 6.5 
                 +0.518 
               
               
                   
                 Placebo 
                 2.6 
                 2.1 
                 −0.536 
               
               
                   
                   
               
               
                   
                 T-test comparing pre and post-test score changes for 3-trial means scores by experimental group: P = 0.045  
               
               
                   
                 Regression Model: Post-test 3-trial mean scores = pre-test 3-trial mean scores + alcohol status.  
               
               
                   
                 P = 0.069 for alcohol status  
               
               
                   
                 P = 0.003 for pretest score  
               
               
                   
                 R 2  for model = 0.95  
               
               
                   
                 Correlation between post-test mean scores and simulator performance score: R = 0.74  
               
             
          
         
       
     
     Alternative applications of this device are also available outside the fitness for duty testing area. For example, with software modifications, the present invention could be used for entertainment purposes as a video game for one or more persons to play individually or as a team, either by standing, or being seated with the device being hand-held, or mounted to the floor or a table in a resilient fashion, with an objective of the game being to maintain the shape at a predetermined position, or to deny opposing players the ability to maintain the shape at the desired position. Additional handles could be provided for team games in which each team has its own shape  30  of unique color or shape. 
     While the present invention has been described in connection with certain preferred embodiments, it is to be understood that the invention is defined by the following claims, when read in light of this description and the accompanying drawings, and equivalents thereof.