WO2001028420A1

WO2001028420A1 - Apparatus and method for assessing pulmonary ventilation

Info

Publication number: WO2001028420A1
Application number: PCT/US2000/028704
Authority: WO
Inventors: F. Dennis Mccool; John C. Niple; Richard N. Iriye; Thomas P. Sullivan
Original assignee: Electric Power Research Institute, Inc.
Priority date: 1999-10-18
Filing date: 2000-10-17
Publication date: 2001-04-26
Also published as: AU1210301A

Abstract

An apparatus (20) for assessing pulmonary ventilation includes data acquisition circuitry (21) with a first transmission coil, a second transmission coil, a first receive coil, and a second receive coil to generate pulmonary ventilition data defining three degrees of motion of an ambulatory patient. A portable data processing unit worn by the patient is connected to the data acquisition circuitry (21) and process the pulmonary ventilation data to produce calculated parameters, such as breathing frequency, total pulmonary ventilation, inspiratory breathing time, expiratory breathing time, and total breathing time.

Description

APPARATUS AND METHOD FOR ASSESSING PULMONARY VENTILATION

This application claims priority to the U.S. Provisional Patent Application entitled "Apparatus and Method for Assessing Pulmonary Ventilation", Serial Number 60/160,298, filed October 18, 1999.

BRIEF DESCRIPTION OF THE INVENTION

This invention relates generally to techniques for analyzing pulmonary ventilation. More particularly, this invention relates to a portable pulmonary ventilation analysis device.

BACKGROUND OF THE INVENTION Measurement of pulmonary ventilation typically requires the use of devices, such as masks or mouthpieces. These devices alter pulmonary ventilation and are also impractical and inconvenient for continual monitoring of pulmonary ventilation. Thus, it is desirable to have a device for continuous measurements of pulmonary ventilation that is both non-invasive and non-encumbering. Devices that sense respiratory excursions of the chest wall are both non-invasive and non-encumbering. Different types of devices for measuring chest wall respiratory excursions have been developed. One type of system relies upon magnetometers to measure two degrees of breathing freedom. Such systems rely upon respiratory magnetometers with tuned pairs of electromagnetic coils, one transmitting and the other receiving a specific high- frequency AC electro-magnetic field. To measure the anteroposterior diameter of the rib cage, one coil is usually placed over the sternum at the level of the 4^th intercostal space and the other over the spine at the same level. To measure the anteroposterior diameter of the abdomen, another pair is usually placed on the abdomen at the level of the umbilicus, and over the spine at the same level. Over the operational range of distances, the output voltage is a function of the distance between the pair, provided the axes of the magnetometers remain parallel to each other. As rotation of the axes may change the voltage, the transducer and receiver coils must be secured to the skin in a parallel fashion and rotation due to motion of underlying soft tissue must be minimized.

Also known in the art are systems that rely upon magnetometers to measure three degrees of breathing freedom. Such systems use magnetometers positioned as in the two degree systems, plus magnetometers to sense changes in the axial displacement of the chest wall due to postural movements of the spine and pelvis. The signals from the magnetometers are processed to obtain improved tidal breathing volume data for a patient.

The problem with present magnetometer based systems is that they are relatively large. Consequently, they can only be used in a lab or other controlled setting. In other words, present magnetometer based systems are not portable and therefore cannot be easily used in field testing or for monitoring other types of activity where unencumbered motion is desirable.

Devices other than magnetometers have also been used to measure motion of the rib cage and abdomen. In particular, respiratory inductive pleysthemograph (RIP) belts have been used to measure rib cage and abdomen motion. RIP belts consist of two loops of wire, which are coiled and sewed into an elastic belt. To measure changes in cross-sectional areas of the rib cage and abdomen, one belt is secured around the mid-thorax and a second belt is placed around the mid-abdomen. The voltage change from the belts is linearly related to changes of the enclosed cross- sectional area. The volume of air inhaled and exhaled is then calculated from the sum of these signals. The output parameters include the volume inhaled and exhaled, breathing frequency, and the changes in chest wall dimensions during breathing. The problems with RIP belts include: (1) they rely upon a two degree of freedom model, which is inaccurate when body position changes, (2) axial displacements cannot be measured, (3) the RIP belts tend to slip on the rib cage and abdomen, thereby changing their calibration, and (4) they are not portable.

In sum, there are a number of problems associated with existing pulmonary ventilation analysis systems. A primary shortcoming of these systems is that they are not portable. Thus, they cannot be used in a variety of potentially important applications, including the epidemiologic study of air toxins on pulmonary and cardiovascular health, the study of respiratory muscle dysfunction, and exercise testing. In view of the foregoing, it would be highly desirable to provide a pulmonary ventilation monitor with high accuracy. Ideally, such a system would be portable to facilitate pulmonary ventilation analyses in new medical realms.

SUMMARY OF THE INVENTION

An apparatus for assessing pulmonary ventilation includes data acquisition circuitry with a first transmission coil, a second transmission coil, a first receive coil, and a second receive coil to generate pulmonary ventilation data defining three degrees of motion of an ambulatory patient. A portable data processing unit worn by the patient is connected to the data acquisition circuitry and processes the pulmonary ventilation data to produce calculated parameters, such as breathing frequency, total pulmonary ventilation, inspiratory breathing time, expiratory breathing time, and changes in end-expiratory volume.

The invention provides a compact, lightweight, low-power device that can be used to non-invasively measure the quantity of air an individual inhales and exhales. The compact, lightweight, low-power device of the invention allows pulmonary ventilation analyses to be performed in new contexts. In addition, due to its advantageous size, the device of the invention can analyze data representing three degrees of motion, while minimizing motion artifacts due to non-respiratory events, such as vibration of soft tissue that occurs while running or walking. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which: FIGURE 1 illustrates a pulmonary ventilation analysis device in accordance with an embodiment of the invention.

FIGURE 2 illustrates data processing circuitry constructed in accordance with an embodiment of the invention.

FIGURE 3 illustrates the positioning of the data acquisition circuitry in accordance with an embodiment of the invention.

FIGURE 4 is a more detailed representation of selected components of the data processing circuitry of Figure 2.

FIGURE 5 illustrates a pulmonary ventilation analysis device in accordance with an alternate embodiment of the invention. FIGURE 6 illustrates an apparatus corresponding to the device of Figure 5.

FIGURE 7 is a side view of a first end of the data processing circuitry of Figure 6.

FIGURE 8 is a side view of a second end of the data processing circuitry of Figure 6. Like reference numerals refer to corresponding parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 illustrates a pulmonary ventilation analysis device 20 constructed in accordance with an embodiment of the invention. The pulmonary ventilation analysis device 20 includes data acquisition circuitry 21 and data processing circuitry 22. In one embodiment of the invention, the data processing circuitry 22 includes data input interface circuitry 24 to receive data from the data acquisition circuitry 21. As its name implies, the data input interface circuitry 24 operates as an interface that insures that the input data from the data acquisition circuitry 21 is in a format that allows it to be processed by the remainder of the data processing circuitry 22. In addition, the data input interface circuitry 24 preferably includes a data input mechanism, such as a keypad. In the embodiment of Figure 1, the data input interface circuitry 24 applies digital signals to system buses 23 and 26. A central processing unit 28 is connected to the buses 23 and 26. The bus 26 is connected to a memory 30, which stores a set of executable programs, including: a calibration routine 32, digital band pass filters 34, a Finite Element Analysis module 36, a parameter calculator 38, and a display engine 40. The central processing unit 28 executes the programs stored in the memory 30; the data produced by the executed programs may be stored in the memory 30 as accumulated pulmonary ventilation data 42.

The calibration routine 32 operates to calibrate the data acquisition circuitry 21. Advantageously, this operation is performed by the calibration routine 32 in a single step. As demonstrated below, the data acquisition circuitry 21 includes a flow meter.

The digital band pass filters 34 are utilized to eliminate artifacts due to soft tissue motion. The filters are assigned to eliminate selected frequencies associated with soft tissue motion. This allows the elimination of most extraneous noise from the magnetometer signals. These clean signals are subsequently summed to provide a measure of tidal volume, even when the individual is performing ambulatory activities.

The Finite Element Analysis module 36 executes finite element analyses on acquired data, resulting in noise reduction. The inclusion of Fourier analyses and band pass filtering in the software facilitates the use of the device 20 in ambulatory activities.

The parameter calculator 38 uses known equations to define parameters, such as: end-expiratory lung volume, breathing frequency, total pulmonary ventilation, inspiratory breathing time, and expiratory breathing time. A display engine 40 is used to facilitate the visual display of acquired data, which may be displayed on an output device 46, which interacts with the CPU 28 through data output interface circuitry 44. The output device 46, for instance a liquid crystal display, is optional to the data processing circuitry 22. The invention may be implemented simply with a data output interface 44, which operates to interact with external output devices, such as a personal computer, a printer, a monitor, and the like. Figure 1 also illustrates an autonomous power source 50, which may be a battery.

The invention has been implemented in a compact and light weight configuration that can be easily attached or carried by an individual being monitored. As used herein, a portable or light weight device refers to a device that is less than five pounds, preferably between 1 and 3 pounds.

In one implementation of the invention, the output device 46 included a two- line, eight-character liquid crystal display. The CPU 28 was implemented as a Motorola 68332 micro-controller with a 256K program memory and a 256K SRAM. A 15 MB flash non-volatile memory was used as the memory 30.

The data input interface circuitry 24 was implemented to include an on/off slide switch and a nine-button keypad to control and select menu functions. In addition, the data input interface circuitry 24 included four 9-pin connectors, a 3.5 mm stereo (3-conductor) serial port jack, and a 4-position locking connector for the flow meter. The connectors may be used for attachment to the transmit coils, the receive coils, an external power source, and test equipment.

In one implementation, the device 22 operated on a 100 mA current from a +/- 8.0V to +/-12.0V autonomous power source 50. The three sensor channels are measured at 20 samples per second.

With respect to the data acquisition circuitry 21, an 8.97 kHz transmitter coil, a 7 kHz transmitter coil, an 8.97 kHz receiver coil, and a 7/8.97 kHz receiver coil were used.

Figure 2 illustrates an embodiment of the data acquisition circuitry 21. Those skilled in the art will appreciate that the distinction between the data acquisition circuitry 21 and the data processing circuitry 22 is somewhat arbitrary since many of the functions of the data acquisition circuitry 21 may be incorporated into the data processing circuitry 22. Indeed, in embodiments of the invention, most of the functional elements, except for the coils 60-63 have been incorporated into the data processing circuitry 22. The functional elements of Figure 2 are shown as part of the data acquisition circuitry 21 for illustrative purposes.

As shown in Figure 2, the data acquisition circuitry 21 includes a first transmission coil 60 and a second transmission coil 62. As indicated above, the invention has been implemented with an 8.97 kHz transmitter coil and a 7 kHz transmitter coil. Figure 2 also shows a first receive coil 61 and a second receive coil 63. The first receive coil is an 8.97 kHz receive coil, while the second receive coil 63 is a 7/8.97 kHz receive coil. The dual functionality of the second receive coil reduces the number of receive coils, thereby reducing the number of attachments to a patient, simplifying system design, and reducing power requirements.

Figure 3 illustrates the coils 60-63 attached to a patient 51. Figure 3 also illustrates the data processing circuitry 22 attached to the patient 51 via a belt 52. The first transmitter coil 60 (e.g., operating at 8.97 kHz) is positioned at the umbilicus of the patient 51. The first receive coil 61 is positioned at the same axial location, but on the back of the patient. The second receive coil 63 is positioned at the base of the sternum of the patient 51. The second transmission coil 62 (e.g., operating at 7 kHz) is located at the same axial position, but on the back of the patient 51. The second receive coil 63 processes signals from both the first transmission coil 60 and the second transmission coil 62, reducing the number of coils needed to calculate volume using the three degrees of freedom model from six to four. This simplifies the instrumentation attached to the individual, and reduces power requirements by eliminating one transmitter coil. Preferably, the coils 60-63 are attached to the exterior chest wall and abdomen of the patient 51 using medical tape. Flexible wire leads (not shown) connect the coils 60-63 to the data processing circuitry 22.

Arrow 64 of Figure 3 illustrates the Xi or Xiphi -umbilical distance. Arrow 65 illustrates the rib cage-anteroposterior (RC-AP) distance, while arrow 66 illustrates the abdomen-anteroposterior (Ab-AP) distance. Thus, Figure 3 illustrates the three degrees of motion (Xi, RC-AP, Ab-AP) that are measured in accordance with the invention. As the patient breathes, the change in distance between the coils in each pair is sensed. This change in distance corresponds to a change in voltage that is a function of changes in the anteroposterior distance of both the rib cage (RC-AP) and the abdomen (Ab-AP). In addition, the axial displacement of the chest wall (Xiphi- umbilical distances: Xi) is measured and is a function of the distance between the two pairs of sensors. The volume of air inhaled and exhaled is determined using these signals. The breathing characteristics, which are derived from this data, include the volume of air inhaled and exhaled, breathing frequency, and changes in chest wall dimensions during breathing. These values are calculated by the parameter calculator 38, as discussed below. Returning to Figure 2, a first transmission signal pre-processor 70 applies a signal to the first transmission coil 60. Similarly, a second transmission signal preprocessor 72 applies a signal to the second transmission coil 62. Figure 2 also illustrates that a first received signal pre-processor processes a signal from the first receive coil 61, while a second received signal pre-processor processes a signal from the second receive coil 63. The received signals are then processed by three channels, including a first detection circuitry channel 80, a second detection circuitry channel 82, and a third detection circuitry channel 84. The output of the individual channels is applied to the data input interface circuitry 24 for subsequent processing and storage by the CPU 28 in accordance with the executable programs stored in memory 30.

The data acquisition circuitry 21 also includes a flow meter 86, whose output is processed by a low pass filter 88 before being applied to the data input interface circuitry 24. The data produced by the flow meter 86 is used during the calibration step, as discussed below. Figure 4 is a more detailed view of selected components of the data acquisition circuitry 21. In particular, Figure 4 illustrates that the first transmission signal preprocessor 70 includes a first oscillator 94, for example set to 8.97 kHz. The oscillator signal is applied to a first transmission channel variable gain circuit 92, which allows an optimal gain value to be set. The gain for the first transmission channel variable gain circuit 92 may be set through the data input interface circuitry 24. The gain adjusted signal is then applied to a differential signal driver 90, and is then applied to the first transmission coil 60. Observe in Figure 4 that the output from the differential signal driver 90 is also applied to the first channel detection circuitry 80 and the second channel detection circuitry 82, as will be discussed further below. The second transmission signal-preprocessor 72 operates in a similar manner.

The second oscillator 100 oscillates at a pre-determined frequency, for example 7 kHz. The oscillator signal is applied to a second transmission channel variable gain circuit 98, which is independently set for an optimal gain value. The gain adjusted signal is then applied to a differential signal driver 96, and is then applied to the second transmission coil 62. The output of the differential signal driver 96 is also applied to the third channel detection circuitry 84, as will be discussed further below. The signal from the first transmission coil 60 is processed by the first receive coil 61 and is then passed to the first received signal pre-processor 74. Figure 4 illustrates that the first signal pre-processor 74 may be implemented with an input stage 102, a first receive channel variable gain 104, and a band pass filter 106. The variable gain 104 may be set through the data input interface circuitry 24. The variable gain circuitry 104 is set to optimize the signal-to-noise ratio. The band pass filter 106 is set to reduce noise above and below 8.97 KHz.

The second received signal pre-processor 76 operates in a similar manner, however, recall that the second receive coil 63 preferably processes two signals. Thus, the second received signal pre-processor 76 processes two signals. A single input stage 108 processes both signals and feeds the output to the two channels that follow. Each channel includes a variable gain circuit 110/116 and a band pass filter 112/118. The separate gain controls 92, 98, 104, 110, and 116 are optimized to increase the signal-to-noise ratio. In addition, the gain controls 92 and 98 for the transmitted signal can be optimized to minimize power requirements. Since the gain for the transmitted signal can be changed independently of the gain of the receiver channel, the signal to noise ratio can be improved while minimizing the magnetic field exposure at the skin surface of the patient.

The band pass filters 106, 112, and 118 minimize interference from extraneous magnetic fields and noise sources. The output from the first received signal preprocessor 74 is applied to the first channel detection circuitry 80. As shown in Figure 4, this circuitry 80 includes a first detector 120, which is set to the frequency established by the first oscillator 94. The output of the first detector is applied to a low pass filter 122 and an absolute value circuit 124. The signal is then passed to the data input interface circuitry 24 so that it may be processed by the CPU 28.

The second channel detection circuitry 82 operates in a similar manner. The second detector 128 is set to the frequency established by the first oscillator 94 and processes the signal from the second receive channel band pass filter 112. The second channel detection circuitry 82 includes a low pass filter 130 and an absolute value circuit 132 to produce a data signal that is directed to the CPU 28 for processing in accordance with the executable programs stored in memory 30. The third channel detection circuitry 84 is set to the frequency established by the second oscillator 100, while processing the signal from the third receive channel band pass filter 118. The third channel detection circuitry 84 also includes a low pass filter 138 and an absolute value circuit 140.

A commercially available coil may be used in accordance with the invention. The invention has been implemented with an RF coil sold by J.W. Miller, Co. This coil minimizes the magnetic field exposure to the individual wearing the instrumentation. Further, the magnetic and mechanical design of the coil is optimized to reduce the sensitivity of the coil to rotation and positioning on the body. Preferably, the abdominal coil is stabilized to reduce soft tissue movement noise artifacts. The data acquisition circuitry 21 has been fully described. Attention now turns to the processing associated with the executable programs stored in memory 30. In particular, the following discussion details the operation of the calibration routine 32, the digital band pass filters 34, and the Finite Element Analysis module 36. Subsequently, attention turns to the calculations performed by the parameter calculator 38.

The calibration routine 32 provides calibration coefficients throughout a range of body positions and activities. The calibration coefficients can be calculated for specific activities or body postures. These different sets of calibration coefficients are applied to selected regions of the acquired data set. The ability to apply activity or posture specific calibration coefficients to specified areas of the data set enhances the accuracy of the device.

The calibration routine 32 is also used to adjust the variable gain elements 92, 98, 104, 110, and 116 for optimum signal levels. The calibration routine 32 allows for the calculation of the volume of air inhaled and exhaled. This volume is calculated from the sum of three signals (the changes in the anteroposterior diameter of the rib cage (RC) and abdomen (Ab) and the changes in the axial dimensions of the anterior chest wall (Xiphi-umbilical distance:Xi)). Volume may be defined as: Volume = aRC + bAb + cXi, where a, b, c are coefficients determined by multiple linear regression analysis during a calibration maneuver where the subject breathes through a flow meter for 1-2 minutes at varied tidal volumes and body positions. The calibration process is preferably a one step routine wherein the results of the routine are displayed to the user for quality control prior to data analysis. If the calibration routine is inadequate it can then be repeated until acceptable coefficients are determined. The calibration routine also allows the user to derive coefficients from different segments of the data set (e.g., sitting, standing, walking ...) and label them as such. These coefficients can then be applied to the data set to construct spirograms of volume over time.

The initial step in the calibration routine is to adjust the gain levels for components 92, 98, 104, 110, and 116 of Figure 4. The gain for each channel is adjusted until the signal begins to saturate. The gain may be manually adjusted through manipulation of buttons on the data input interface circuitry 24 or may be automatically adjusted at the direction of the calibration routine 32. The calibration routine 32 identifies when the signal becomes saturated. The signal is then set for one increment below the saturation value. Preferably, a signal is generated on an output device 46 when saturation is reached. In the case of manual gain adjustment, this signal is used to prompt the user to proceed to the next channel. In the case of the automated gain adjustment, calibration of the next channel automatically commences. After the gain levels are adjusted, a flow meter 86 (shown in Figure 2) is attached to the device and the human subject breathes into the flow meter 86. A low pass filter 88 filters the output from the flow meter 86. The flow meter data is correlated with body ventilation volume changes measured with the receive coils 61 and 63. This results in correlation data, which is described below. At this point, the flow meter 86 is removed and the device is operated in a post-calibration mode wherein data is received from the first and second receive coils 61 and 63.

The digital band pass filters 34 are utilized to eliminate artifacts due to soft tissue and other noise sources. The filters 34 are configured to eliminate high frequency and low frequency sources of non-respiratory noise. The filters 34 facilitate measurements of inhaled volume during activities, such as walking or running. Band pass filtering may be combined with finite element analysis to enhance the accuracy of the device, thereby allowing practical application to ambulatory individuals.

The Finite Element Analysis module 36 executes Fourier analyses on acquired data, resulting in simplified signal processing. The inclusion of Fourier analyses and band pass filtering in the software facilitates the use of the device 20 in ambulatory activities. The parameter calculator 38 correlates the three degrees of motion data with the flow meter data collected during the calibration step. The parameter calculator 38 uses these data to create correlation parameters for calculating the end-expiratory, lung volume, breathing frequency, total pulmonary ventilation, inspiratory breathing time, expiratory breathing time, and total breathing time. These parameters may be displayed on a visual output device of the output devices 46.

Figure 5 illustrates an alternate embodiment of the pulmonary ventilation analysis device 20 of the invention. The device 20 of Figure 5 generally corresponds with the device of Figure 1, however, the autonomous power source 50 is external to the data processing circuitry 22. In addition, the pulmonary ventilation analysis device 20 of Figure 5 includes a removable memory 160 (e.g., a flash memory card, floppy diskette, or the like) which is used to store the accumulated data 42. The accumulated data 42 is then transferred to a personal computer 162. The personal computer 162 includes a central processing unit 164 and a set of input/output devices 166 which communicate via a system bus 168. A memory 170 is also attached to the system bus 168. The memory stores the previously described digital band pass filters 34, Finite Element Analysis module 36, and parameter calculator 38. Thus, in this embodiment, the accumulated data 42 is processed with a separate device.

Figure 6 illustrates an apparatus corresponding to the device of Figure 5. In particular, Figure 6 illustrates data processing circuitry 22, including data input interface circuitry 24 and an output device 46 in the form of a liquid crystal display. Figure 6 also illustrates data acquisition circuitry 21, including a flow meter 86, a first transmission coil 60, a second transmission coil 62, a first receive coil 61 and a second receive coil 63. Figure 6 also illustrates an autonomous power source 50. Figure 7 is a side view of a first end 172 of the data processing circuitry 22 of

Figure 6. In particular, the figure illustrates a removable memory 160 in the form of a flash memory card 160. The data input interface circuitry 24 shown in Figure 7 includes a test connector 180, an ON/OFF button 182, a power connector 184, and a communication port 186. Figure 8 is a side view of a second end 174 of the data processing circuitry 22 of Figure 6. In particular, the figure illustrates a flow meter port 190, a transmitter coil connector 192, and a receiver coil connector 194. Those skilled in the art will appreciate that the calculated parameters of breathing frequency, total pulmonary ventilation, inspiratory breathing time, expiratory breathing time, and total breathing time can be used to identify normal breathing patterns, at rest, with activity, during speech, with changes in posture, with exposure to pollutants, during sleep, and with coughs or to identify abnormal breathing patterns, such as those seen with respiratory dyskinesia, impending respiratory failure, exacerbations of emphysema, asthma and other forms of lung disease. In addition, normal and abnormal changes that occur with changes in posture, activity, with disease, or during exposure to pollutants can be assessed. These parameters can also be applied to characterize both obstructive and central apneic episodes in adults and infants during sleep, calculate flow volume loops during exercise and sleep, characterize breathing patterns in individuals with undiagnosed causes of episodic dyspnea, study the effect of air toxins on pulmonary and cardiovascular health, monitor respiratory patterns in of individuals in acute and chronic respiratory care units.

The compact structure of the invention allows for data gathering during ambulatory activities, thereby facilitating new analyses of pulmonary ventilation during typical daily activity. The circuitry and signal processing associated with the invention establishes excellent accumulated data, notwithstanding the compact structure of the invention.

The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. In other instances, well known circuits and devices are shown in block diagram form in order to avoid unnecessary distraction from the underlying invention. Thus, the foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for assessing pulmonary ventilation, comprising: data acquisition circuitry consisting of a first transmission coil, a second transmission coil, a first receive coil, and a second receive coil to generate pulmonary ventilation data defining three degrees of motion; and a portable data processing unit connected to said data acquisition circuitry to process said pulmonary ventilation data.

2. The apparatus of claim 1 wherein said data acquisition circuitry further comprises a first transmission signal pre-processor connected to said first transmission coil and a second transmission signal pre-processor connected to said second transmission coil, said first transmission signal pre-processor and said second transmission signal pre-processor each including an independently adjustable variable gain circuit.

3. The apparatus of claim 2 wherein said first transmission signal pre-processor and said second transmission signal pre-processor each includes an oscillator connected to the input of said independently adjustable variable gain circuit and a differential signal driver connected to the output of said independently adjustable variable gain circuit.

4. The apparatus of claim 1 wherein said data acquisition circuitry further comprises a first received signal pre-processor connected to said first receive coil and a second received signal pre-processor connected to said second receive coil.

5. The apparatus of claim 4 wherein said first received signal pre-processor includes an input stage and an independently adjustable variable gain circuit.

6. The apparatus of claim 4 wherein said second received signal pre-processor includes two signal channels, each signal channel including an input stage, an independently adjustable variable gain circuit, and a band pass filter.

7. The apparatus of claim 1 wherein said data acquisition circuitry further comprises first channel detection circuitry to process a data signal from said first receive coil in accordance with an oscillation frequency corresponding to the oscillation frequency of said first transmission coil.

8. The apparatus of claim 7 wherein said data acquisition circuitry further comprises second channel detection circuitry to process a data signal from said second receive coil in accordance with an oscillation frequency corresponding to the oscillation frequency of said first transmission coil.

9. The apparatus of claim 8 wherein said data acquisition circuitry further comprises third channel detection circuitry to process a data signal from said second receive coil in accordance with an oscillation frequency corresponding to the oscillation frequency of said second transmission coil.

10. The apparatus of claim 9 wherein said first channel detection circuitry, said second channel detection circuitry, and said third channel detection circuitry each include a detector, a low pass filter, and an absolute value circuit.

11. The apparatus of claim 1 wherein said data acquisition circuitry further comprises a ventilation flow meter.

12. The apparatus of claim 1 wherein said data processing circuitry includes a central processing unit and a memory storing a set of executable programs.

13. The apparatus of claim 12 wherein said memory stores a calibration routine to automatically calibrate said data processing unit.

14. The apparatus of claim 12 wherein said memory stores a parameter calculator to generate a parameter value selected from the group comprising: a lung volume value, a breathing frequency value, a total pulmonary ventilation value, an inspiratory breathing time value, and an expiratory breathing time value.

15. The apparatus of claim 12 wherein said memory stores a finite element module o execute a Fourier analysis on said pulmonary ventilation data.

16. The apparatus of claim 1 further comprising an autonomous power source.