Abstract:
A method of and an apparatus for monitoring the heart motion of a subject employ a probe which can be coupled to the aortic arch or to the thyroid cartilage of the subject for detecting movements caused by the heart motion and displaying the accelerations and displacement of the heart motion on an acceleration display and a displacement display. A mechanical motion amplifier amplifies the acceleration and an optical amplifier amplifies the displacement to counteract noise.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to methods of and apparatus for non-invasively monitoring heart motion and is useful for the non-invasive monitoring of cardiac functions, in particular, but not exclusively, of human hearts. 
     2. Description of the Related Art 
     In the past, methods for the non-invasive monitoring of cardiac function have included:
         Mechanical methods, for example, pulse recording of the jugular carotid artery or apex cardiography.   Electrical techniques, for example, electrocardiograms (ECGs).   Imaging techniques, including echocardiology, radiography and magnetic resonance imaging (MRI).       

     However, mechanical methods are inaccurate because of physical differences between subjects. For example, the intensity of heart sounds cannot be accurately measured because of the fat thickness layer differences. 
     Some non-invasive mechanical methods do not couple properly to the external movement generated by the heart and are therefore of little use. 
     The electrical techniques cannot correlate to the force of cardiac contraction and are therefore of little use, and imaging techniques are also subject to this problem. For example, an echocardiogram determines a ratio known as the “ejection fraction”, which is a measure of cardiac performance which may or may not be related to the force of the heart&#39;s contraction. In a normally functioning heart, this relationship may hold true, but this finding is unreliable because the head pressure of the cardiovascular system is unknown. 
     None of the above-mentioned prior methods or techniques can accurately measure the isovolumic phase of the heart cycle, which is the most important parameter to measure in identifying coronary artery disease. 
     In U.S. Pat. No. 5,865,759, issued Feb. 2, 1999 to the present inventor, the disclosure of which is incorporated herein by reference, there is disclosed an apparatus and method to assess cardiac function in human being which employ a sensing mechanism positioned on the thyroid cartilage in the neck against the trachea for sensing a response of the thyroid cartilage to heart function. 
     While this prior patent disclosed a restraining system to hold the sensing mechanism in position, it was found that the apparatus is extremely sensitive to gravity because the force resulting from the weight of the sensing mechanism and a sensor restraining system varied in dependence on the vertical and horizontal position of the subject under test. 
     Consequently, a large cardiac force would decouple the sensing mechanism, so that a subsequent low magnitude force would be recorded poorly or not at all. These weak forces were so poorly recorded that very large electronic amplification was used, resulting in a poor signal-to-noise ratio and the recording of mostly noise. The poor coupling resulted in false data, which showed a poor correlation between the isovolumic contraction phase and the ejection phase of the heart cycle in nominal hearts, as shown by a clinical study. Another result was that the diastolic part of the cycle could not be recorded. This is a very important phase in which the passive inflow into the ventricles occurs and data relating to this phase could indicate the elasticity of the ventricular muscle. Furthermore, this prior apparatus was difficult to operate because positioning the sensor on the thyroid cartilage was difficult as elastic members forming parts of the restraining system had to be in tension balance to prevent the sensing mechanism from being moved to one side or another of the thyroid cartilage, causing erroneous data. Also, with this prior apparatus, mechanical interference caused by the sensor restraining system and an accelerometer forming part of the sensing mechanism contacted clothing, pillows, beards, fatty neck tissue, and in the case of a short neck contacted the chest, resulting in huge errors. Because no coupling apparatus was provided in this prior system, the addition of more sensors was not possible nor could reliable data be obtained. Also, this prior system employed wire connections extending directly to a recorder, resulting in stiffness and inertial effects due to interference of the wiring with the motion of the sensor. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the present invention, apparatus for monitoring the heart motion of a subject comprises a probe movable in response to movements of the anatomy of the subject, an accelerometer movable with the probe, an acceleration display indicative of the acceleration of movements of the probe, and a mechanical motion amplifier between the probe and the acceleration display. 
     Preferably, the apparatus includes a displacement display indicative of the displacement of the movement and an optical motion amplifier between the probe and the displacement display. 
     When this apparatus is in use, the acceleration and the displacement of the heart motions are simultaneously displayed in real time and can be observed to detect any irregularities of the heart motion. 
     In a preferred embodiment of the invention, the mechanical motion amplifier comprises a lever supported on a mounting which serves as a fulcrum, the lever and the mounting being pivotable about a pivot axis in response to movements of the probe, which is provided at one end of an effort section of the lever. An accelerometer is provided on a load section of the lever, with the pivot axis between the probe and the accelerometer. Pivotable movement of the accelerometer on the lever in response to the movements of the probe is an amplification of the pivotation of the lever and, therefore, of the movements of the probe, which correspond to the movements of the subject&#39;s anatomy. The pivotal movement of the accelerometer is amplified when the ratio of the load section length divided by the effort section length is greater than one. Electrical amplification of the accelerometer output can be employed as required. 
     The optical motion amplifier, in this embodiment, is an optical device in the form of a mirror supported on the mounting and a laser light source directing light onto the mirror for reflection to the displacement display. 
     These mechanical and optical motion amplifiers have the advantage that they provide the displays with noise levels substantially less than when electronic amplifications alone are utilized. 
     In the preferred embodiment of the invention, the accelerometer is adjustable in position along the load section of the lever in order to correspondingly adjust the magnitude of its motion. This largely eliminates inter-instrument differences, and enables comparison of data results between centres of clinical research as well as greatly reducing the cost of quality control in the manufacturing process. 
     The apparatus also includes a chin rest which can be engaged with the subject&#39;s chin, with the probe adjusted to engage the subject&#39;s thyroid cartilage, and a jaw and head rest which can be engaged with the subject&#39;s jaw and head with the probe adjusted coupled with the arch of the subject&#39;s aorta in the region in the base of the brachiocephalic artery. In this way, the apparatus can be adjusted for engagement with either of these two parts of the anatomy of the subject. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more readily understood from the following description of an embodiment thereof given, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  shows a view in side elevation of a heart monitoring apparatus according to a preferred embodiment of the invention being coupled to the aortic arch of a seated subject; 
         FIG. 2  shows a view in perspective of the apparatus of  FIG. 1  coupled to the aortic arch of a subject in a prone position; 
         FIG. 3  shows a view in side elevation of the apparatus in  FIG. 1  in use on a seated subject with the apparatus coupled to the thyroid cartilage of the subject; 
         FIG. 4  shows a view in side elevation of the apparatus of  FIG. 1  in use on a subject in a prone position with the device again coupled to the thyroid cartilage of the subject; 
         FIG. 5  shows a view in perspective parts of the apparatus of  FIGS. 1-4 ; 
         FIGS. 6 and 7  show plan views of parts of the apparatus of  FIGS. 1-4 , with a chin rest and a jaw and head rest; 
         FIG. 8  shows a broken-away view of a lever and a pivotable support member pivotally supporting the lever: 
         FIG. 8A  shows a view taken in section along the line  8 A- 8 A of  FIG. 8 ; 
         FIG. 9  shows a side view of the components of the apparatus shown in  FIG. 8 , with an aortic arch connected to the effort section of the lever for coupling to the aortic arch; 
         FIG. 10  shows a view corresponding to that of  FIG. 9 , but with the probe replaced by a different probe for coupling to the trachea; 
         FIG. 11  shows a view in side elevation of the aortic arch of  FIG. 9 ; 
         FIG. 12  shows a view in perspective of the aortic arch probe of  FIG. 11  with a protective sheath and a broken-away part of a housing of the apparatus of  FIGS. 6 and 7 ; 
         FIG. 13  shows a view in side elevation of the parts shown in  FIG. 12 ; 
         FIG. 14  shows a broken-away view of an end of the aortic arch probe of  FIGS. 11 and 12  and its protective sheath in coupling contact with the skin of a subject; 
         FIGS. 15 through 17  show a plan view, a view in side elevation and a view in transverse cross-section, respectively, of an overhead carriage and swivel mechanism forming part of the apparatus of  FIGS. 1-4 ; 
         FIG. 18  shows a diagrammatic view of parts of the apparatus of  FIGS. 1-4 , including mechanical and optical motion amplifying devices; 
         FIGS. 19 and 20  diagrammatically illustrate two modifications of an optical motion amplifying device shown in  FIG. 12 ; 
         FIG. 21  shows a view in side elevation of a pivotable support member forming part of the apparatus of  FIG. 1-4 ; 
         FIG. 22  shows a view taken in cross-section through a pivot supporting one end of the support member of  FIG. 21  and electrically connecting the pivot to an analog-to-digital converter; and 
         FIG. 23  shows a block diagram of the components of the apparatus of  FIG. 1  with a system linkage to a computer using a USB multiplexing system. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     To facilitate understanding of the various modes of operation of the apparatus of  FIG. 1 , which is a sensor apparatus indicated generally by reference numeral  10  in  FIG. 1 , the sensor apparatus  10  is shown in coupled relationship to subjects in different positions in  FIGS. 1 to 4  of the accompanying drawings. Accordingly,  FIGS. 1 to 4  will firstly be described below, before a more detailed description of the construction and operation of the sensor apparatus  10 . 
     Measurement of the heart&#39;s motion, such as its acceleration, is important as the motion of the heart is a function of force which arises from a change in momentum of the heart mass and the ejection of blood during the various phases of the heart cycle. When a heart abnormality appears, the pattern and the amplitude of these forces change, thereby yielding diagnostic value. 
     The heart generates both strong and weak forces, which are all of importance in diagnosis. The method and apparatus described below enable the measurement of both systolic and diastolic phases of the heart cycle. As described below, the present apparatus can measure the heart forces generated at the brachiocephalic region of the aortic arch as well as those at the thyroid cartilage region of the trachea. The aortic arch is an ideal point to measure as it provides much information on all of the phases of the heart cycle and provides the most information on atrial contraction. It also is the best method for the operating room as the patient does not have to have his knees elevated close to his body nor does he have to elevate the head and bend it towards his chest. The present method enables coupling of the apparatus to the trachea so strongly that many different sensors can be used simultaneously, for providing displacement and acceleration waveforms in real time and for enabling a variety of sensors, including optic types, to be utilized. The strong coupling enables mechanical and optical amplification, thereby avoiding any need for high electronic amplification and drastically reducing the electronic noise so as to enable the recording of very small but important motions of the heart, e.g. that due to the passive inflow of blood into the ventricles. The shape and magnitude of recording can indicate the degree of elasticity of the left ventricular wall. 
     Using the present apparatus on normal hearts, the isovolumic phase (i.e. the hearts contraction before the valves of the heart are open) is strongly correlated to the ejection phase in magnitude and duration. The value of this is obtained in cases where the force of contraction is large but the ejection is of low magnitude, and allows a conclusion, with assurance, that stenosis of the aortic valve exists. The ejection fraction can be obtained at a fraction of the cost of an echocardiograph by constructing a nomogram. The procedure for effecting this is to firstly derive normal values for the amplitudes of the isovolumic and ejection phases of the heart cycle in a resting healthy adult. These values can then be equated to the value of the ejection fraction as determined by the electrocardiograph, which is known to be 67%. This value is equated to the isovolumetric amplitude and the ejection amplitude. The electrocardiograph identifies subjects with ejection fractions of 17% to 57%, which are equated to the values obtained by the present method and apparatus. The ejection fraction can now be obtained from the values of the isovolumic and ejection phases. Error can be prevented by not using data when there are indications of valve abnormalities, which are indicated when high values of the isovolumetric phase do not occur with high values in the ejection phase and vice versa. 
     There is some difficulty in interpreting the acceleration waveform, even if an ECG had been taken simultaneously. The present method solves this problem by simultaneously and in real time recording the displacement and acceleration waveforms. The direction of the acceleration, especially during the isovolumic phase, can be determined from the displacement, which enables diagnosis of paradoxical left ventricular motion, which is an indicator of cardiac muscle damage. 
     The present apparatus virtually eliminates inter-instrument differences, which are a large problem in acceleration measurements, as accelerometers vary in their outputs. 
     The present method and apparatus produce accurate results independently of the subject&#39;s physical structure, and resist any interference from clothing, beards etc. They are easily operable in an office, an emergency room or an operating room theater. 
     The use of the brachiocephalic area of the aortic arch is also ideal for cardiac research in most mammals. 
     In  FIG. 1 , the sensor apparatus  10  is shown in coupled relationship with the aortic arch of the chest of a subject seated in a chair indicated generally by reference numeral  14 . The sensor apparatus  10  is carried by a support device, indicated generally by reference numeral  16 , from a ceiling  17  by a support plate  18  so that the sensor apparatus  10  can be readily manoeuvred and adjusted in position relative to the subject  12 . 
     The sensor apparatus  10  is moved forward or backward as required to couple an probe of the sensor apparatus  10  directly behind the right-hand side of the manubriurn, substantially parallel to the main axis of the heart, between the jugular and the clavicular notch and angled approximately 45° to the neck. The subject&#39;s head is rotated to the right. The subject is asked to inhale deeply several times to facilitate the movement of the probe to a depth greater than 1.5 inches until the probe reaches the aortic arch and a record is obtained. A jaw and head rest, indicated generally by reference numeral  53  and provided on a housing  32  of the sensor apparatus  10 , is adjusted to contact the jaw and the base of the skull when contact is made with the brachiocephalic region of the arch of the aorta at a point approximately 2 inches below the manubrium, by an aortic arch  54  ( FIG. 9 ) fitted onto an end of a lever  56  projecting from the housing  32 , as described in greater detail below. As also described in greater detail below, correct coupling of the probe  54  with the subject&#39;s aortic arch in the brachiocephalic region will be indicated by a strong pivotal movement of the lever  56 . The lung resistance can influence the motion of the heart and should therefore be measured prior to determining the performance of the heart. In this type of test, the subject is asked to breath fairly rapidly. The higher the amplitude of the displacement is, the higher the resistance of the lung is gauged to be. 
     In  FIG. 2 , the sensor apparatus  10  is shown in use on a subject, indicated generally by reference numeral  18 , who is lying in a prone position, with his head turned to the right, on a trolley indicated generally by reference numeral  20 . The probe  54  is coupled to the aortic arch of the subject  18 , while the jaw and head rest  53  is employed to position the sensor apparatus  10  relative to the subject. 
     In  FIG. 3 , the sensor apparatus  10  is shown coupled to the thyroid cartilage of a subject indicated generally by reference numeral  22 . The subject is seated on a seat  24  with her feet on a foot rest  26 . In this case, the jaw and head rest  53  is not in use, and instead a U-shaped chin rest  46  is engaged with the subject&#39;s chin to position the sensor apparatus  10  relative to the subject. Also, the probe  54  is replaced on the lever  56  by the probe  44  ( FIG. 10 ). 
     In this mode, the subject&#39;s head is bent towards the chest and the feet raised close to the body to raise the pressure in the abdomen. The sensor apparatus  10  is then moved into position so as to exert a force against the trachea on the thyroid cartilage while at the same time the top of the sensor apparatus  10  is adjusted to be parallel to the jaw. 
     In  FIG. 4 , the sensor apparatus  10  is shown coupled by the probe  44  to the thyroid cartilage of a subject, indicated generally by reference numeral  28 , who is in a semi-prone position by a trolley indicated generally by reference numeral  30 . 
     The manner in which the sensor apparatus  10  can be adapted for use in the various positions shown in  FIGS. 1 through 4  will be more readily apparent from the following description of the construction and operation of the sensor apparatus  10 . 
     As shown in  FIG. 5 , a manually engageable handle in the form of a ball  34 , by means of which the sensor apparatus  10  can be manoeuvred in position, is provided on the housing  32 , which is connected to the support device  16  by a ball joint  35 , allowing the housing  323  to be tilted as desired. The ball joint  35  is provided with a lock screw  37  for fixing the housing  32  in position relative to the support device  16 . 
     At one end of the housing  32 , there is provided a displacement display  36  for displaying the waveform of the displacement of a subject&#39;s heart, and a displacement magnitude display  38  for displaying the magnitude of the displacement whose waveform is shown by the display  36 . 
     The sensor apparatus  10  is connected to a laptop computer indicated generally reference numeral  40 , and the housing  32  is provided with three sockets  42  for connecting a digital microphone  194 , a digital ECG apparatus  194  and a digital respiratory belt  196 , which are diagrammatically illustrated in  FIG. 23  and which are associated in known manner with the subject to be monitored when the apparatus is in use. 
     As shown in  FIGS. 6 and 7 , the jaw and head probe  53  has a pair of arms  55  which are each pivotally secured at one end to a shaft  57 . The shaft  57  extends along the interior of a sleeve  59 , which is secured on the housing  32  by lugs  61  extending from the sleeve  59  and secured by screws  62  to the housing  32 . At its opposite, free end  63 , each of the arms  55  is connected by a pivot  65  to a pad  67  which rests on the subject when the jaw and head rest  53  is in use. End caps  69  in threaded engagement with the ends of the shaft  57  retain the shaft  57  in position in the sleeve  59 . 
     By pivoting the shaft  57  and the arms  55  relative to the housing  32 , the jaw and chin rest  53  can be moved between an inoperative position, in which it is shown in  FIG. 6  and in which the arms  55  lie above the housing  32 , and an operative position, in which it is shown in  FIG. 7  and in which the arms  55  and their pads  67  project beyond the end of the housing from which the lever  56  protrudes. 
     The jaw and head rest  53  is shown in use in  FIGS. 1 and 2 . Having the subject in the supine position as shown in  FIG. 2  is an ideal arrangement for the operating room theatre, as the subject can lie flat on his or her back. The head should be turned to the right, as shown. The jaw and head rest  53  is pivoted so as to project forwardly from the housing  32  and the sensor apparatus  10  is manipulated into position and tilted, using the ball  34 , to position the probe  54  just behind the right side of the manubrium, between the jugular and the clavicular notch and angled 45° towards the neck and substantially parallel to the main axis of the heart. The subject is asked to inhale deeply several times to facilitate the movement of the probe to a depth greater than 1.5 inches until the probe reaches the aortic arch and a record is obtained. The jaw and head rest  53  is adjusted for contact with the jaw and the base of the skull of the subject, thereby preventing interference with the motion of the probe  54 . 
     As shown in  FIG. 11 , the probe  54  is in the form of a rod which at one end has a bifurcated end portion indicated generally by reference numeral  71 . A pair of pivot pins  73  in threaded engagement with arms  75  of the bifurcated end portion  71  have pointed ends  77  pressed into opposite longitudinal edges  79  of an end portion  81  of the lever  56 , which projects from the housing  32 , so as to pivotally secure the probe  54  to the lever  56 . 
     In addition to the jaw and head rest  53 , the chin rest  46  ( FIG. 6 ) is provided on the housing  32  is employed when the sensor apparatus  10  is coupled to the thyroid cartilage, as shown in  FIGS. 3 and 4 . 
     By means of plates  48  pivotally connected to opposite sides of the chin rest  48  and adjustment screws  50 , inserted through slots  52  in the plates  48  into threaded engagement with the housing  32 , the chin rest  46  can be adjusted to contact the subject&#39;s chin. The screws  50  can then be tightened, after which the ball  34  is manipulated to move probe  44 , which is fitted on the end portion  81  of the lever  56  as shown in  FIG. 10 , into contact with the brachiocephalic region of the arch of the aorta, which will be indicated by a strong pivotation of the support member  62 . By unscrewing the screws  50 , the chin rest  46 , with its connection plates  48 , can be removed from the housing  32 . 
     By removing the chin rest  46  and pivoting the jaw and head rest  53  from the position in which it is shown in  FIG. 6  to the operative position shown in  FIG. 7 , and by replacing the probe  44  on the lever  56  by the probe  54 , the sensor apparatus  10  can be adapted for coupling to the aortic arch, as indicated above. 
     The lever  56  is mounted, by means of a mounting in the form of a bushing  58  ( FIG. 9 ) and a locking screw  60 , on a pivotal support member  62 , the construction and operation of which are described in greater detail below. The probe  44  or  54 , when the apparatus is in use, is displaced by movements of the relevant part of the subjects anatomy resulting from the subject&#39;s heart motion and these movements cause the lever  56  and the support member  62  to pivot about the longitudinal axis of the support member  62 . 
     An accelerometer  64  ( FIG. 8   a ) is fixed to a U-shaped housing  66 , and a locking screw  68  extends through the housing  66  in threaded engagement with the housing  66  for releasably securing the housing  66  and, therewith, the accelerometer  64  to the lever  56 . The housing  66  and the screw  68  thereby provide an adjustable connection between the accelerometer  64  and the lever  56 , which allows the position of the accelerometer  64  to be adjusted along the length of the lever  56  and, thereby, allows the amplification of the pivotation of the support member  62 , in response to the movements of the probe  54  or  44 , to be correspondingly adjusted. The output of the accelerometer  64  can thereby be calibrated so that the sensor apparatus  10  can be adjusted to take into account variations in the output of the accelerometer  64  and, also, the amplification of the pivotation of the support member  62  by the corresponding pivotation of the lever  56 . 
     As shown in  FIGS. 11 and 12 , a removable protective sheath  83  is fitted over the probe  54  at its free end, opposite from the bifurcated end portion  71 . 
     Referring now to  FIGS. 12-14 , the probe  54  is housed in an elongate protective housing indicated generally by reference numeral  85 , which at its upper end has an annular end portion  87 . By means of screws  89  inserted through the end portion  87  into threaded engagement with a protruding portion  91  of a housing  93 , the housing  85  is releasably secured to the housing  93  The protruding end portion  81  of the lever  56  projects into the housing  93  into pivotal engagement with the pivot pins  73  within the protruding portion  91 . The housing  93  is in turn secured over an end portion  95  of the housing  32  by screws  97  and the end portion  95  is formed with a rectangular opening  99  through which the end portion  81  of the lever  56  projects. 
     As shown in  FIG. 14 , the protective housing  85  has an open lower end portion  101 , through which the tip of the sheath  83  protrudes, and is formed with end protrusions  103  at opposite sides of the open end portion  101 . 
     When the probe  54  is in use, the sensor apparatus  10  instrument is carefully pushed downwardly until the protrusions  103 , as shown in  FIG. 14 , stretch the subject&#39;s skin, indicated by reference numeral  104 , sufficiently to couple the tip of the sheath  83 , and thereby the probe  56 , to the brachiocephalic region of the aortic arch, which is detected by moving the probe  54  and reinserting it until maximum displacement amplitude is observed on the displacement display  36 . A record of the displacement and acceleration of the heart is taken along with a record of the lung resistance to air flow. The subject is asked to breathe rapidly for the lung test and the resultant magnitude of the displacement recorded or observed on the phosphorescent screen of the displacement display  36  at the front of the sensor apparatus  10 . The larger the displacement, the higher is the lung resistance to air flow. 
     The support device  16 , which comprises an overhead carriage and swivel mechanism of a type similar to that employed by dentists to support adjustable overhead lamps, is of a well known construction and will therefore not be described in greater detail herein. However, the support device  16 , instead of being carried by the support plate  18  from the ceiling  17 , may instead be mounted under an overhead carriage and swivel mechanism indicated generally by reference numeral  111  in  FIGS. 15-17 . The mechanism  111  has a pair of parallel rails  113 , which as can be seen from  FIG. 16  have upturned end portions  115  terminating in mounting brackets  117 , by means of which the rails  113  can be secured by screws (not shown) to the ceiling  17 . The rails  113  are braced by cross-bars  119  spaced apart along the rails  113  and a carriage indicated generally by reference numeral  120  is movable along the rails  113  between the cross-bars  119 . The carriage  120  has a housing  122  containing an electric motor  123 , a battery pack  125  for supplying power to the electric motor  123  and two pairs of rollers  126  and  128  in rolling engagement with the rails  113 , one of the rollers  126  being connected through a friction clutch  127  to the electric motor  123  so that on energization of the motor  123  the carriage is driven along the rails  113 . 
     A rotatable support plate  132  is mounted beneath the housing  122 , by means of a threaded retainer, indicated generally by reference numeral  135 , with a ball race  133  between the support plate  132  and the housing  122 . The threaded retainer  135  has a threaded lower end  137  in threaded engagement with a nut  139  recessed in the underside of the support plate  132 , a head  141  seated on a bottom wall  143  of the housing  122  and a cylindrical portion  145  between the threaded lower end  137  and the head  141 . The retainer  135  is rotatable, together with the support plate  132 , relative to the housing  122 . 
     The energization of the motor  124  is controlled by a wireless remote control unit  144  communicating with a control unit  145  in the housing  122 . The support plate  18  ( FIG. 1 ) is secured by screws to the underside of the support plate  132 , so that, after the housing  122  has been suitably positioned along the rails  113 , the sensor apparatus  10  can be manually manoeuvred into position relative to the subject to be monitored. 
     From  FIG. 18 , it can be seen that the support member  62  is an elongate member, one end of which is journalled in a pivotal support  70 . The opposite end of the support member  62 , as shown in  FIG. 22 , is journalled in a pivotal support indicated generally by reference numeral  71 , which is similar to the pivotal support  70 . A pair of electrical conductors  72  and  73  connect the accelerometer  64  to the interior of the support member  62 , as will be described in greater detail below with reference to  FIG. 22 . In addition, the pivotal support member  62  carries two mountings  74  and  76 , on which mirrors  78  and  80  are mounted, and a pulley  82 . The pulley  82  is connected by a cord  84  to one end of a helical tension spring  86 , the opposite end of which is connected to a cord  90 , wound on a pulley  92 . The pulley  92  is mounted on a shaft  100 , which is journalled in a side wall  88  of the housing  32  and which can be rotatably adjusted, by rotation of a manually adjustable detent knob  102  on the shaft  100 , to exert an adjustable bias on the support member  62  and thereby to urge the probe  44  or  54  on the lever  56  towards the subject being monitored so as to assist in coupling the probe to the subject. The adjustment knob  102  can be releasably locked into position by means of a lock screw  104 . 
     A laser light source in the form of a laser  106  directs a light beam  108  onto the mirror  78 , from which the light beam is reflected onto a mirror  110  and a rotating mirror  112  to a display screen  114  forming part of the display  36  of  FIG. 5 . The screen  114  is a phosphorescent screen of high persistence, and the trace of the light beam  108  on the screen  114  represent the waveform of the displacement of the heart function being monitored. 
     A second laser  116  directs a light beam  118  onto the mirror  80 , from which the light beam is reflected onto a photodiode  120  to control the energization of a motor  122  rotating the mirror  112 , so that the rotation of the mirror  112  is synchronized with the pivotation of the pivotable support member  62  and, thus, the probe  44  or  54 . 
     The pivotable support member  62  also carries a mounting  124  ( FIG. 19 ) carrying a mirror  146  for reflecting a light beam  148  from a laser  150  onto a screen  152 , which forms part of the display  38 , and which is a phosphorous screen of long duration for displaying the magnitude of the displacement of the heart function. 
     The screen  152  may be replaced by a position sensing diode array  154  ( FIG. 20 ), which provides a digital output having a magnitude corresponding to the deflection of the beam  148  by the pivotation of the mirror  146 . 
       FIG. 21  shows in greater detail the pivotal support member  62  which is tubular and provided at opposite ends with end caps  156  and  157  from which protrude pivot pins  158 . As illustrated by the pivotal connection  71  of  FIG. 22 , each pivot pins  158  is pivotally received in a threaded grub screw  160  in threaded engagement with a threaded retainer  162  which, in turn, is in threaded engagement with a wall  164  of the housing  32 . The conductor  72  from the accelerometer  64  extends along the interior of the tubular pivotal member  62  to the right-hand end cap  157 , as viewed in  FIG. 21 , which is electrically conductive and which electrically connects the conductor  72  through the grub screw  160  to an electrical conductor  75 , thereby providing an electrical connection without affecting the pivotation of the pivotal member  62 . The electrical conductor  75  is connected to the laptop computer  40 . Similarly, the conductor  73  is connected though the left-hand end cap  158  to the computer  40 . Within the tubular member  62 , the conductors  72  and  73  extend along the interior of a tubular shield  166  which is soldered to the end cap  156  at the left-hand end of the pivotal support member  62 , as viewed in  FIG. 21 . 
       FIG. 22  diagrammatically illustrates the processing of the dat obtained by the above-described apparatus. A computer display  180 , which is the display of the laptop computer  40  ( FIG. 1 ), displays images corresponding to those of the displacement and magnitude displays  36  and  38 . The laptop computer  40  includes a power supply  182  for supplying power to the components of the sensor apparatus  10 . More particularly, the power supply  182  supplies power through a power conditioner  184  to the accelerometer  64 , the output of which is connected through an analog-to-digital converter  185 , a USB module  186 , a USB multiplexor  188  and a USB isolator  190  to the computer  40  to be shown on the display  180 . 
     The lasers  106 ,  116  and  150  are also powered by the power supply  182 . The beam of the laser  106 , deflected by the mirror, and synchronised by the output of the diode  120 , is supplied as a displacement waveform, which corresponds to that displayed on the displacement display  36 , is supplied through the USB multiplex system  188  and the USB isolator  190  to be displayed on the display  180  in the form of a graph similar to that of the displacement display  36 . The beam of the laser  116 , falling on the photodiode  120 , actuates the motor  122  to rotate the mirror  112  and thereby to synchronise the displacement display with the pivotation of the support member  62 . 
     As indicated above, the laser  150  can be employed with the screen  152  or with the position sensing diode array  154 , and is therefore shown twice in  FIG. 23 . When the laser  150  is used with the screen  152 , as illustrated in  FIG. 19 , the beam of the laser  150 , deflected by the mirror  146 , provides an output signal representing the magnitude of the displacement, corresponding to that displayed on the display  38 , which is supplied through the USB multiplex system  188  and the USB isolator to the laptop computer  40  to be shown on the display  180 . 
     When, however, the deflected beam of the laser  154  is applied to the position sensing diode array  154 , as illustrated in  FIG. 20 , the output of the position sensing diode display  154  is supplied through a USB module  192 , the multiplex system  188  and the USB isolator  190  to be shown on the computer display  180 . 
       FIG. 23  also shows the digital microphone  194 , the digital ECG apparatus  194  and the digital respiratory belt  196  connected to respective USB modules  200 ,  202  and  204 , with an analog-to-digital converter  206  connected between the analog respiratory belt  198  and the USB module  204 . The USB modules  200 ,  202  and  204  are connected through the USB multiplex system  188  and the USB isolator  190  to the computer  40  so that their outputs can be displayed on the computer display  180 . 
     It is an advantage of the apparatus described above with reference to the accompanying drawings that at least six cardiac parameters may be simultaneously recorded, i.e. the acceleration, displacement, the ECG, the phonocardiogram, and the respiratory cycle. The above-described apparatus records simultaneously and in real time the acceleration and the displacement waveforms, thereby making it possible to determine the direction of the acceleration at each phase of the heart cycle and enabling the diagnosis of many heart conditions, including paradoxical left ventricular motion which indicates cardiac muscle damage. The present apparatus can utilizes a variety of sensors to measure displacement, e.g. the miniature linear potentiometer, and the optical methods The optical motion amplifier shown in  FIG. 12  can quickly display, without the aid of a computer or any other recording means, a high lung resistance indicative congestive heart failure. The present apparatus maintains its pre-exercise position and can be repositioned by remote control and is therefore suitable for operating theater use. 
     The present invention enables waveforms of cardiac motions to be obtained non-invasively from two different body sites, i.e. from the aortic arch and the trachea, and to be combined into a single resultant waveform, using the ECG as a phase marker, thereby providing more detailed diagnostic information than can be obtained from a single body site. The two waveforms can be independently analyzed and compared with one another and also with the resultant waveform. 
     The present invention may also be applied to animal research to determine the effect of experimental cardiac drugs on the heart. 
     As will be apparent to those skilled in the art, various modifications may be made in the above-described embodiment of the present invention within the scope of the appended claims.