Surgery – Diagnostic testing – Respiratory
Reexamination Certificate
2000-05-24
2002-05-14
Shaver, Kevin (Department: 3736)
Surgery
Diagnostic testing
Respiratory
C600S529000, C600S532000
Reexamination Certificate
active
06387053
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for determining an indicator which is dependent on respiratory data and defines the transition from the aerobic to the anaerobic metabolism of a person, with said person being subjected to physical stress, as well as an apparatus to perform the method,
The physical performance capacity of an organism constitutes an integrative and imprecisely described value which is to quantify the ability to tolerate physical stress. As a result of physical stress several subsystems of the organism are loaded in different forms and intensities depending on the respective state of training. The most important of said subsystems are, in addition to the neuromuscular systems for initiating the sequence of motions, the oxygen transport system (respiration, diffusion of the respiratory gases, oxygen binding to hemoglobin, cardiovascular system) and the metabolic system of the working skeletal muscles.
Since the metabolic system of the skeletal muscle constitutes the performance-limiting system in the healthy person, the muscular metabolism is given primary attention in exercise-resp. work physiology.
In order to perform physical activities it is necessary that the muscle is able to rely on a pool of adenosine triphosphate (ATP) as a direct source of energy (see FIG.
1
). With the exception of short-time work for which only phosphate stores are used, two metabolic ways are available for its resynthesis which are used depending on the respective requirements concerning intensity of work and duration of work. The most important and energetically most favourable way is the aerobic metabolism in which the substrates glycogen and glucose and also free fatty acids are degraded into carbon dioxide and water, provided an adequate supply of oxygen via respiration and circulation.
The aerobic pathway, however, can only provide moderately high energy flow rates, therefore the second metabolic variant, the anaerobic pathway, is additionally activated for performance of higher work load intensities (also at the beginning of physical work). This mechanism of providing energy uses glycogen and glucose as a substrate, but supplies lactate as an end product. It is usually produced more rapidly than it can be degraded and therefore accumulates in the organism. At the same time hydrogen ions are produced, so that termination of the activities occurs by muscular exhaustion due to the local acidosis in connection with the rise in lactate.
Physical stress in which primarily the aerobic metabolic pathway is used is the ideal and desirable form of health training, e.g. endurance training, because an economisation of the cardiovascular system is achieved on the one hand and mobilization of metabolism and the lipocatabolism are promoted on the other hand.
In exercise physiology the idealized assumption as illustrated in
FIG. 2
is frequently made that the energy needs (by taking into account the mechanical efficiency) as predetermined by the exercise protocol are covered by way of the biochemical energy liberation as long as the demanded strain is lower than the individually determined maximum strain. In the exercise protocol illustrated the total expenditure of energy increases according to an approximately quadratic function.
The maximum share to be covered via the aerobic metabolism is illustrated by a straight line whose slope depends on the maximum aerobic capacity of the test person (which among other things is a function of the state of training).
Once the total expenditure exceeds the maximum expenditure that can be provided aerobically, the differential share to the total expenditure must be provided by way of the anaerobic metabolism.
The time T
an
, namely the moment of the transition from aerobic to anaerobic, in which the aerobic provision of energy is exceeded is stated (with a defined exercise protocol) in units of stress (e.g. watts).
When implemented practically, however, the transition from aerobic to anaerobic metabolism cannot be defined precisely by a moment or a stress value, so that frequently a transition area is defined at the lower limit (aerobic threshold) of which the change of the energetic metabolism begins and at the upper limit (anaerobic threshold) of which the same is completed.
Since the intensity of stress at which the organism switches from the energetically more favourable aerobic metabolism to the anaerobic metabolism depends on the respective state of training and thus on the physical work capacity, various indicators are defined within the scope of ergometric tests or performance tests which are based on various physiological indicators or variables of the involved subsystems of the organism and their changes as a consequence of standardized exercise protocols.
Depending on their assignment to the various subsystems the following indicators are known:
Lactate-oriented indicators
Heart-rate-oriented indicators
Indicators dependent on respiratory variables
The lactate concentration in the blood is used as a biological variable in the case of lactate-oriented indicators. In order to obtain a numerical value in terms of physical work, the functional relation between lactate concentration and work load on the ergometer is determined empirically using a standardized protocol with stepwise increasing work load. The work load at two defined lactate concentrations, namely 2 mmol/l and 4 mmol/l is used as a characteristics for the physical performance capacity. The 2 mmol/l value is defined as the aerobic threshold and the 4 mmol/l value as the anaerobic threshold. The intermediate range is designated as aerobic-to-anaerobic transition.
Where heart-rate-oriented criteria are concerned, either absolute values of the heart rate (e.g. 60% of the maximum heart rate) or specifics of the time course of the heart rate (discontinuities or deflection points) in an increasing work load protocol are used as an indicator for the transition from the aerobic to the anaerobic metabolism. The best known example of this test method is the so-called CONCONI test.
Respiratory-oriented criteria are based on the physiological fact that when using the anaerobic metabolism in addition to lactate hydrogen ions are formed which lead to a metabolic acidosis. The hydrogen ions are buffered by the bicarbonate buffer-system of the blood, with CO
2
being liberated. It is expired via the respiratory system. Caused by respiratory control, a compensatory hyperventilation is initiated, so that carbon dioxide is expired more intensively. Therefore one frequently puts the oxygen consumption in relationship with the carbon dioxide output (e.g. by calculating the so-called “respiratory exchange ratio —RER”) and tries this way to derive the indicators for the transition from the aerobic to the anaerobic metabolism.
The indicators used most frequently in performance diagnostics are the lactate-oriented ones, namely the so-called lactate thresholds. Their advantage is the ability to be determined precisely by measurements. Their disadvantage is the necessity to take blood from the hyperemisized ear lobe and the required instrumentation for the chemical analysis.
Heart-rate-oriented indicators are easy to be determined non-invasively. As a result of the indirect representation of muscular metabolism with respect to a cardiovascular variable, they show a lack of precision and reproducibility, however.
Respiratory-oriented indicators have the advantage of a direct relation to the muscular metabolism (metabolic acidosis). Their determination, however, relies on conventional methods of ergospirometry, and on extensive equipment.
DESCRIPTION OF THE PRIOR ART
From U.S. Pat. No. 5,297,558 for example an algorithm is known for the determination of an indicator for the “fat burning point”. This point substantially corresponds to the aforementioned aerobic-to-anaerobic transition and is determined conventionally on the basis of respiratory variables. The so-called respiratory exchange ratio (RER) is determined by means of an ergospirometry system known from U.S. Pat. No. 4,463,7
Dykema Gossett PLLC
F. Hoffmann-La Roche AG
Natnithithadha Navin
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