Device for recording the movement of parts of the body

Abstract: A recording device for movement of parts of the body, in particular respiratory movements, which device comprises an elastic hollow tube stretched over a part of the subjects body, such as the chest, through which tube sound pulses are sent while the frequency is being kept inversely equal to the length of the tube. The frequency and rate of variation thereof provides information on the movements.

Description: The invention relates to a recording device for the recordal of movement of parts of a body, where the recording device comprises an elastic tube adapted to be stretched over part of the user's body. Such a recording device is known in the state of the art. US 2,194,809 describes an air-filled tube which, upon elongation caused by inhalation, causes the pressure inside the tube to rise, and pressure changes are measured. Thus a physician can be provided with data on the respiratory behaviour of the subject. It is also known to record movements of a body part by encircling a user with an elastic hollow tube filled with a conductive fluid. By measuring the impedance at both ends of the elastic tube, movement of the body can be monitored. Such a device is for example known from WO-A-91/07760. The object of the invention is to provide an alternative recording device according to the preamble, enabling accurate measurement of respiratory parameters. To this end the recording device according to the invention is characterized in that the elastic tube is an elastic hollow tube having a first end attached to an electro-acoustic transducer capable of generating a sound pulse and a second end attached to an electro-acoustic transducer capable of receiving said sound pulse, the electro-acoustic transducer being capable of adjusting the frequency of said sound pulse through said elastic hollow tube to maintain the frequency inversely proportional to the length of said elastic hollow tube. Thus a recording device is provided which is convenient to wear and allowing accurate measurements. The French patent application 2,273,259 describes measuring the transit time of acoustic surface wave signals through an elastic body. This body is solid, and not hollow. The recording device according to the invention will be described by using of example referring to the accompanying drawing. Fig. 1 is a block diagram of the recording device. Fig. 2 is a schematic frontal view of the recording device. Fig. 3 is an illustration of a recording device applied to a user's chest. According to fig. 1, the recording device 2 comprises an elastic hollow tube 14, stretched around the chest or abdomen of the user, forming the measuring distance of the recording device 2. At the two ends of the tube 14 electro-acoustic transducers 15, 16 are mounted to generate, respectively receive, sound impulses transmitted through the tube 14. The sound impulse sender 15 transduces electrical signals 18 emitted by an impulse generator 17 into sound impulses which in a certain transit time pass through the length of tube 14 and are subsequently received by the receiver 16. Said receiver then transduces the sound impulses into electrical signals 19, which are fed back preferably via a frequency regulation device 20 to the impulse generator 17. This feed back, preferably in the form of a phase-locked loop, occurs such that the repeat frequency f of the sound impulses is inversely proportional to the length L of the tube 14. Thus the length of the tube 14 can be directly deduced from this sound impulse frequency and consequently also the changes therein caused by the respiratory movements of the user. The transit time of the sound impulses is determined by the length of the tube 14, which will vary due to the respiratory movements. During one inhalation and exhalation the length of the tube will increase, respectively decrease and consequently a sound impulse will be received at a relatively earlier, respectively later moment in time. The moment of reception is compared with a reference impulse signal 21 issued simultaneously by the impulse generator 17. The time and phase difference with respect thereto is determined by a phase difference detector 22, determining the extent of the phase difference as well as its character, that is to say, it will determine whether the impulse signal 19 received lags behind the reference pulse signal 21 (inhalation) or runs ahead of it (exhalation). In order to guarantee a stable phase relation between the reference impulse signal 21 and the received pulse signal 19, in other words in order to maintain the relation f~1/L, the repeat frequency f of the pulse signal produced by the pulse generator 17 must be adjusted after each pulse cycle. This is preferably done - as already mentioned - by means of a phase-locked loop, to which end the frequency regulation device 20 is among other things equipped with a filter, an integrator and a voltage-controlled oscillator, which, however, for the sake of simplicity are not shown in the block diagram of Fig. 1. In this way the pulse frequency f of the electrical pulse signal generated by the generator 17 is regulated such that in case of a longer or shorter length of tube 14 the pulse frequency f is lowered, respectively raised by means of said regulation loop. In this manner the phase relation between the received signals and the reference pulse signals 19 respectively 21 at the beginning of each pulse cycle are stabilized, irrespective of the extent to which the tube 14 is stretched. In order to also keep the sound pulses, weakened by transmission losses in the tube 14, at a constant intensity, independent of the length of the tube 14, the received pulse signal 19 is at the same time fed back into the pulse generator 17 via an amplitude regulation device 23, effectuating a constant amplitude of the pulse signal. It will be understood that the recording device 2 is completely self adjusting so that it can be equipped with, for instance a removable and easily deformable tube 14 of any length which does not need to be adapted to the chest circumference of the user. The tube 14 can therefore easily be applied by the user himself, without any aids such as adhesive, adhesive tape or adhesive electrodes, if desired even over the clothing of the user. Exchange of the recording device 2 between users, female or male, is also no problem. The electro-acoustic transducers 15, 16 can, for instance be housed in a housing which can serve as coupling piece for connecting the ends of the tube 14 and the necessary electric wiring. The signal issued by the phase difference detector 22 is fed into a respiratory pattern analyzer 24 which by means of the phase difference signal analyses the recorded respiratory pattern, passing the same in the form of a respiratory signal 3, for instance in digital form, to a processing device. More information on what can be done with such a signal is described in the application, of which the present application is a divisional. The unit schematically shown in Fig. 2 comprises the housing 53 in which the electro-acoustic transducers 15, 16 are housed. One of these electro-acoustic transducers 15, 16 functions as source, the other as receiver unit. The electro-acoustic transducers 15, 16 are connected with each other via the elastic tube 14, which is made, for instance from silicone polymers. The connection between the tube 14 and the electro-acoustic transducers 15, 16 can be made by means of the tube connectors 54, 55 mounted in the housing. For securing to chest or abdomen with the aid of the tube 14, the housing can be provided with a fastening notch 56, extending for example over 180° or more over the circumference of the housing. As mentioned above, the electro-acoustic transducers 15, 16 may be housed in a housing. This housing may have the form of a clasp, whereby the tube 14 is formed into a single large loop and is stretched double around the chest and/or abdomen. This is shown in Fig. 3, whereby the tube 14 is stretched in a double loop around a person's chest and the housing 53 functions as clasp. The tube 14 is brought over an operable distance into the fastening notch 56. The connecting lead 58 leads from the housing to the processing device 4 (not shown). The recording device according to the invention can be used in an interactive respiratory regulator offering a wide range of applicability not only for hyperventilation, but in principle with any non-optimal respiratory behaviour.

Claims: A recording device for the recordal of movement of parts of a body, where the recording device comprises an elastic hollow tube (14) adapted to be stretched over part of the user's body, characterized by the elastic hollow tube (14) having a first end attached to an electro-acoustic transducer (15) capable of generating a sound pulse and a second end attached to an electro-acoustic transducer (16) capable of receiving said sound pulse, the recording device comprising a frequency regulating device for adjusting the frequency of said sound pulse through said elastic hollow tube (14) to maintain the frequency inversely proportional to the length of said elastic hollow tube (14). A device according to claim 1, characterized in that the recording device (2) is provided with means capable of determining, from frequency changes of the sound pulses occurring during each cycle of movement, parameter values of the pattern of movement. A device according to claim 2, characterized in that the recording device (2) is provided with a phase difference detector (22) capable of measuring the phase difference between received sound pulses (19) and a reference pulse signal (21). A device according to claim 2 or 3, characterized in that the frequency regulation device (20) is capable of effectuating a stable phase difference of the received sound pulses (19) at the start of each sound pulse cycle, with regard to the reference pulse signal (21). A device according to claim 4, characterized in that the frequency regulating device (20), together with the phase difference detector (22) forms a phase-locked loop. A device according to any of the preceding claims, characterized in that the recording device (2) comprises an amplitude regulating device (23), which allows for guaranteeing that irrespective of the length of the tube (14), the received sound pulses (19) have a constant intensity.

Inventors: DE WILLIGEN CORNELIS ADRIAAN, DEFARES PETER BERNARD, VERVEEN EDUARD THEODORUS, DE WILLIGEN, CORNELIS ADRIAAN, DEFARES, PETER BERNARD, VERVEEN, EDUARD THEODORUS
Applicants: DEFARES PETER BERNARD, VERVEEN EDUARD THEODORUS, WILLIGEN CORNELIS ADRIAAN DE, DE WILLIGEN, CORNELIS ADRIAAN, DEFARES, PETER BERNARD, VERVEEN, EDUARD THEODORUS
Application year: 1993
Main classification: A61B5
IPC codes: A61B5