WO2002034129A1

WO2002034129A1 - Capacity stress testing method and apparatus

Info

Publication number: WO2002034129A1
Application number: PCT/SE2001/002322
Authority: WO
Inventors: Christer Jacobsson; Zita Frising
Original assignee: Optovent Ab
Priority date: 2000-10-24
Filing date: 2001-10-23
Publication date: 2002-05-02
Also published as: AU2001296194A1

Abstract

A convenient and time-saving capacity stress test method is made available, comprising the steps of subjecting a person undergoing the test to physical exercise; monitoring and/or register oxygen the saturation of the blood automatically; and monitoring and/or register the pulse rate automatically, wherein the heart function is automatically monitored and/or registered by electrocardiogram and the respiratory rate is automatically monitored and/or registered. Also an apparatus for carrying out the method is available. The inventive method and apparatus ensures validated and quality assured data, gives the physician a reliable basis for evaluating the condition of the patient and diagnosing possible diseases. Additionally, the method gives the personell carrying out the test increased possibilities to observe the well being of the test person.

Description

CAPACITY STRESS TESTING METHOD AND APPARATUS

TECHNICAL FIELD OF THE INVENTION

The present invention concerns a capacity stress testing method and apparatus wherein a person exercises while certain parameters are monitored and/or registered.

BACKGROUND ART

The term "stress test" means a test where a test leader watches a test person who exercises under the influence of increasing load, while certain body functions and parameters are monitored and/or registered. Stress tests are today mainly used for forming a basis for a doctor to evaluate and diagnose coronary heart diseases and to estimate a person's maximum work load in relation to a normal value for the age.

Traditionally, parameters reflecting upon the heart function are registered during a stress test in order to reveal any diseases in the heart, especially in the coronary arteries. These parameters are normally registered by an electrocardiogram, for example the pulse rate and any arrhythmias. Further, the level of exertion ofthe person is monitored manually. Less notice is directed to the respiratory frequency, which according to prior art also is monitored manually by counting the number of breaths per minute. Sometimes the blood pressure is measured, too.

In the Scandinavian countries a cycle exerciser is used for stress tests. Normally the test starts at a level of load of 50 W and will be increased by 10 W/minute. In other countries other gear is used for stress tests, such as step machines and sloping treadmills. Most ofthe times the test is limited by subjective maximum exertion or pain experienced by the tested person, but sometimes the test is limited due to abnormal heart rhythm, severe increase/decrease in blood pressure or signs of widespread hypoxemia (lack of oxygen) in the heart muscle. All these signs give the doctor an indication of significant, underlying heart disease.

US 6 159 130 concerns means for sport training, either professionally or private. The means may measure speed ofthe exercise device (for example a bicycle), ambient temperature and pressure. It may also measure the pulse, blood pressure, temperature, blood glucose and blood oxygen content ofthe training person. The document also shows that the means enables the condition ofthe exercise device to be measured by means of different sensors. In connection with a bicycle, the sensors may measure the brakes (brake wear or brake force), gears (gear shift and gear wear), shaking ofthe bicycle, tightness ofthe chain or the power used. This device is inadequate for medical examinations and thus cannot be used in this field.

SUMMARY OF THE INVENTION

As a basis for the invention is the insight that the heart is not always the limiting factor for the maximum workload, also the lung function has a large significance for the working capacity.

One problem is that a lot of different tests have to be performed before a doctor gets a good basis for the evaluation and diagnosis of possible capacity impairing diseases, such as heart and/or lung diseases.

The object ofthe present invention is to provide a method which gives values of the parameters to be evaluated so that a doctor will obtain from only a single stress test a good basis for the evaluation and diagnose of possible capacity impairing diseases, such as heart and/or lung diseases.

This object is achieved by a capacity stress testing method comprising the following steps:

- subjecting a person undergoing the test to physical exercise,

- monitoring and/or registering the oxygen saturation ofthe blood automatically,

- monitoring and/or registering the pulse rate automatically,

- monitoring and/or registering the heart function by electrocardiogram,

- monitoring and/or registering the respiratory rate automatically, wherein the above steps are performed simultanously.

Using the capacity stress testing method ofthe invention according to claim 1, i.e. a cardiac pulmonary stress testing method, the test person will only have to perform a single stress test for the doctor to obtain a good basis for the evaluation and diagnosis of possible heart and/or lung diseases, for estimation ofthe grade of function impairment and for evaluation ofthe prognosis. Thanks to the provision of this method, it is very convenient and time-saving both for the test person and the health service. If the person is suffering from possible capacity impairing diseases, such as heart and/or lung diseases a stress test can be very painful and frightening and thus it is relieving for the test person to only have to perform one stress test.

The simultaneous monitoring ofthe oxygen saturation ofthe blood gives a synergetic effect which gives a clearer and more apprehensible basis for the doctor when he/she is to diagnose an underlying lung disease as the cause of breast pain or impaired conditions. Another advantage is that since all the values are monitored and registered at one single occasion they all correspond to each other and will not be influenced by any differences in the test person's condition on different test days, or when the tests are carried out on the same day, increasing exertion after each test.

Lung function impairments are seen in a fast increasing respiratory rate at relatively low work loads, which is specially true for restrictive lung diseases, which causes a low respiratory volume. People with overweight or with neuro muscular diseases may also show a similar pattern of abnormally fast increasing respiratory rate at increasing work load. Therefore, a doctor has to evaluate the obtained values and facts.

Another problem is that not all ofthe values ofthe parameters are validated and quality assured. Therefore, also the monitoring and/or register ofthe respiratory rate should preferably be automatic, which gives validated and quality assured values.

Thus, the stress test leader will not have to observe and count the number of respirations per minute manually at the same time as he/she must evaluate the tested person's well being, such as pain and exertion, and signs of problems showing from the automatically monitored and or registered parameters.

Therefore, the test will become more accurate and the leader may focus more on the test person. The leader will be able to assure that the test person really exercise at the top of his/her capacity. For example, the respiratory rate will clearly indicate this. Since the respiratory rate is automatically monitored and/or registered there will not be any differences in counting due to personal and/or objective circumstances. Thus, the values are validated and quality assured and there will neither be any differences inter-individually nor inrra-individually. Preferably also blood pressure is monitored and/or registered and preferably automatically monitored. This will give an even more reliable and objective basis for the doctor's evaluation.

In order to obtain the values ofthe parameters automatically, the pulse rate and oxygen saturation ofthe blood is preferably monitored and/or registered by a pulse oximeter. But of course the pulse rate may separately be monitored and/or registered by an apparatus especially made for this purpose.

In order to obtain the respiratory rate automatically, for example, a thermistor, capnography, transthoracic impedance plethysmography or preferably an optical sensor for sensing a flow of breathing air could be used.

The present applicant have earlier developed a reliable, real-time monitor and a method for monitoring and/or register breathing using an optical sensor. The monitor comprises means for transmitting light and measuring reflecting light and an optical sensor. The optical sensor comprises an optical fibre which at one end is connected to the monitor and at the other end is to be positioned in a breathing air flow of a patient. At the head ofthe fibre, the fibre end is cut preferably perpendicular to the extension ofthe fibre. Light is transmitted through the fibre which reflects at the flat end.

When a person exhale, a humid air flow passes the head ofthe fibre and condenses on the flat end. When the person thereafter inhales, the condensed water on the lens evaporates due to differences in relative humidity. Different amounts of light is reflected by the flat end when it is dry and when it is wet. Therefore, a monitoring can be performed. This is what the applicant call an optical sensor. For further details see patent EP 681 453 ofthe present applicant, incorporated herein by reference.

The invention also concerns a capacity stress testing apparatus comprising

- means for monitoring and/or register the oxygen saturation ofthe blood automatically,

- means for monitoring and/or register the pulse rate automatically,

- means for monitoring and/or register the heart function by electrocardiogram,

- means for monitoring and/or registering the respiratory rate automatically, the above means are adapted to operate simultanously. Preferably the means for monitoring and/or register the respiratory rate is an optical sensor for sensing a breathing air flow and the means for monitoring and/or register the oxygen saturation ofthe blood is a pulse oximeter.

SHORT DESCRIPTION OF DRAWINGS

Fig.1 illustrates a diagram of the performance of a typical patient with

COPD in relation to load.

Fig. 2 illustrates a diagram ofthe performance of one patient with COPD and one normal person in relation to time.

Fig. 3 illustrates a diagram ofthe performance of one patient with COPD and one normal person in relation to degree of exertion.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE LNVENTION

When a person is to be tested according to a first embodiment ofthe method of the present invention the test leader, which could be a nurse or a doctor, for example, will attach or connect electrodes, such as suction electrodes, of an apparatus for electrocardiogram recording at suitable places on the body ofthe test person. Any apparatus for electrocardiogram recording available on the market may be used.

Thereafter a pulse oximeter is attached over a finger tip or ear lobe ofthe test person. The pulse oximeter emits light (red and infrared) through perfused tissue, as in this case the finger tip or ear lobe, and detects the fluctuating signals caused by arterial blood pressure pulses.

Well-oxygenated blood is bright red, while poorly oxygenated blood is dark red. The pulse oximeter determines functional oxygen saturation of arterial haemoglobin from this colour difference by measuring the ratio of absorbed red and infrared light as the blood volume fluctuates with each heart beat. Since steady conditions (steady venous blood flow, skin thickness, bone, finger nails, etc) do not cause fluctuations, the do not affect the saturation reading.

The respiratory rate is automatically monitored and/or registered during the stress test. This is preferably performed by an optical sensor apparatus according to the present applicant's technique described in EP 681 453. An optical fibre is attached to the mouth and nose ofthe test person via a specially designed airway adapter, Airdapter^®.

During expiration, a film of condensation forms on the end ofthe optical fibre. Conversely, during inspiration, the end ofthe optical fibre is dried by the passage of less humid, inhaled air. The optical fibre is coupled to an electronic control unit which sends a light signal through the length ofthe fibre. The majority of this light is reflected back from the end ofthe optical fibre to an optical sensor within the control unit.

However, when the end ofthe optical fibre is covered by a layer of condensation, more light escapes from the end ofthe optical fibre, and less is reflected back to the sensor. The flow of air through the mouth and nose is precisely registered by the variation in the quantity of reflected light, and presented in a LCD display as respiratory rate (number of breaths per minute). For more details, see the patent application WO 99/03395 ofthe present applicant, incorporated herein by reference.

When all the equipment is attached, connected and activated, the test person starts to exercise. Usually a cycle ergometer is used, but of course any other suitable equipment may be used, such as a step machine or a sloping treadmill. As an example the stress test could be performed on a cycle ergometer and start with a load of 50 W. The load will be increased by 10 W per minute.

During the stress test the test leader evaluates the well being ofthe test person and the test person has to describe how he/she feels, like the experienced level of exertion and possible occurring pain.

The test will be stopped when the test person has exercised for a predetermined period of time or when the test person has reached his/her top level of exertion or pain. The stress test will also be stopped if an abnormal heart rhythm occurs or the test person shows signs of widespread hypoxemia in the heart muscle.

The different apparatuses mentioned above may of course be built in together in a capacity stress testing apparatus.

Preferably, according to a second embodiment ofthe present invention, also the blood pressure is automatically monitored and/or registered during the stress test. This may be done by any blood pressure meter apparatus available on the market. Such an apparatus is usually attached to the wrist or upper arm ofthe test person.

According to a fourth embodiment ofthe present invention an apparatus is used comprising both a pulse oximeter and an optical sensor.

After the stress test has been performed all the data registered automatically by the different apparatuses are presented to a doctor, together with any recognitions made by the test leader. The data could either be written down manually or be printouts from the apparatuses.

The method according to the present invention is very helpful for a doctor to give a good basis for the evaluation ofthe parameters as a help when he/she shall correctly diagnose diseases as Chronic Obstructive Pulmonary Disease (COPD), astma, pulmonary emphysema or heart diseases.

COPD is an irreversible disease, which is difficult to diagnose and which is very important to diagnose early to be able to slow it down and keep it under control. Both COPD and asthma is characterised in that the patient has less flow rate of air than normal and especially when exhaling. The patients with asthma have a too high resistance in the bronchial tubes and the patients with COPD have partly a too low alveolar pressure due to an inelastic lung and partly suffers from a dynamic compression ofthe air ways.

When measuring both respiratory rate and blood oxygen saturation together with pulse rate and electrocardiogram (ECG) it is possible to evaluate if the limitation of working capacity is due to respiratory problems or heart problems.

To illustrate the above, tests have been performed both on people in a normal condition and patients with either COPD or a heart disease, the results of these tests are shown below. The table below shows that the patient has a fast increasing respiratory rate and a decreasing blood oxygen saturation but the heart rate increase and the blood pressure increase are normal. This may indicate that the patient suffers from an obstructive lung disease and not a heart disease.

Table 1

The next table shows a patient with good working capacity but during the exercise the heart beats a lot of extra beats, which may indicate that the heart is a limiting factor. The lungs seem to function normally since the increase of respiratory rate and blood oxygen saturation are normal.

Table 2

The next table shows a patient with a normal respiratory increase and a normal blood oxygen saturation. The increase ofthe pulse rate though is rapid and could be an indication of an underlying heart disease.

Table 3

A stress test according to the present invention was performed by a patient with COPD. The patient interrupted the stress test due to shortness of breath after five minutes. The achieved values are presented below in a table.

Table 4

Fig. 1 is a diagram comprising values from table 4 illustrating the respiratory rate and the blood oxygen saturation during a stress test in relation to the load for the patient with COPD.

A corresponding stress test according to the present invention was performed by a healthy person ofthe same sex, age and size. The test person interrupted the stress test due to leg fatigue after ten minutes. The table is shown below.

Table 5

Fig. 2 is a diagram illustrating a comparison between the stress test according to the present invention for the healthy person and the patient with COPD in relation to time. Below is the corresponding table of values.

Table 6

Fig. 3 is a diagram illustrating a comparison between the stress test according to the present invention for the healthy person and the patient with COPD in relation to the degree of exertion. Below is the corresponding table of values.

Table 7

From these stress tests it can be seen that, for this patient with COPD, the respiratory rate reaches a maximum at low load and stays without increasing when the load increases. At the same time the blood oxygen saturation decreases with increased load. If this pattern is shown in other stress tests for other test persons, this could be an indication of an underlying lung disease, such as COPD.

The inventive method gives the doctor an indication of if the impairment ofthe patient is due to a lung disease or a heart disease. Thereafter the doctor may perform other tests to be able to diagnose which type of lung or heart disease it might be.

The inventive method ensures validated and quality assured data, gives the doctor a reliable basis for evaluating the condition ofthe patient and diagnosing possible diseases. Additionally, the method gives the personell carrying out the test increased possibilities to observe the well being ofthe test person.

Although the invention has been described with regard to its preferred embodiments, which constitute the best mode presently known to the inventors, it should be understood that various changes and modifications as would be obvious to one having the ordinary skill in this art may be made without departing from the scope ofthe invention as set forth in the claims appended hereto.

Claims

1. A capacity stress testing method comprising the following steps:

- subjecting a person undergoing the test to physical exercise,

- monitoring and/or registering the pulse rate automatically,

- monitoring and or registering the heart function by electrocardiogram,

2. A capacity stress testing method according to claim 1, comprising the step:

- monitoring and/or registering the blood pressure automatically.

3. A capacity stress testing method according to claim 1 or 2, comprising the step:

- monitoring and/or registering the pulse rate and the oxygen saturation ofthe blood automatically by a pulse oximeter.

4. A capacity stress testing method according to anyone ofthe previous claims, comprising the step:

- monitoring and/or registering the respiratory rate automatically by an optical sensor for sensing a breathing air flow.

5. A capacity stress testing method according to anyone ofthe previous claims, comprising the step:

- monitoring and or registering the respiratory rate and the oxygen saturation of the blood automatically by an apparatus comprising a pulse oximeter and an optical sensor for sensing a breathing air flow.

6. A capacity stress testing method according to anyone ofthe previous claims, comprising the step:

-subjecting a person undergoing the test to physical exercise on a cycle ergometer.

7. A capacity stress testing apparatus comprising

- means for monitoring and/or registering the oxygen saturation ofthe blood automatically,

- means for monitoring and or registering the pulse rate automatically,

- means for monitoring and/or registering the heart function by electrocardiogram,

- means for monitoring and/or registering the respiratory rate automatically, the above means are adapted to operate simultanously.

8. A testing apparatus according to claim 7, wherein the means for momtoring and or registering the respiratory rate is an optical sensor for sensing a breathing air flow and the means for monitoring and/or registering the oxygen saturation of the blood and the heart rate is a pulse oximeter.