Medical Device Classification Rules

23 Aug 2021
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A medical treadmill, which is also used for ergometry and cardiopulmonary stress test as well as performance diagnostics is always a risk class IIb medical device either when used as stand alone device in a medical environment or when used in connection with an ECG, EMG, Ergospirometry or blood pressure monitoring device.

http://ec.europa.eu/DocsRoom/documents/10337/attachments/1/translations

Medical treadmills are class IIb active therapeutic devices and also active devices for diagnosis.

With their very powerful (3.3 kW = 4.5 HP) electric motor powered drive system treadmills deliver mechanical energy to the human body through the moving running belt of the treadmill. The subject is not changing his horizontal position and is passively moved and forced to catch up with the running belt underneath his feet. The subject can also be fixed in safety harnesses, unweighting systems, various supports or even fixed in and moved with a robotic orthotic system utilizing the treadmill.

Medical treadmills are also active measuring devices. They measure the heart rate of the subject. When connected through interface with ECG or ergospirometry or blood pressure monitor or EMG they become a new medical system (e.g. stress test system or cardiopulmonary rehab system) and measure also the ECG, VO2max, breath volumes, blood pressure, muscle activity and various other vital functions.

Treadmills have a “cardio mode”, where a target heart rate is defined and the speed and elevation (load) is controlled automatically until the subject is in “heart rate steady state”. So the treadmill is delivering mechanical energy to the human body based on the vital function (heart rate) of the subject.

A medical treadmill which is also used for ergometry and cardiopulmonary stress test as well as performance diagnostics is always a class IIb medical device either when used as stand alone device in a medical environment or when used in connection with an ECG, EMG, Ergospirometry or blood pressure monitoring device.

Immediate danger and additional potential risks during the intended use are involved because

(1) During various treadmill applications the subject is unable to communicate discomfort or problems and/or may be unable to press the emergency button by himself. This can be for example because the subject is wearing a mask for VO2max measurement, or the subject is disabled or the subject is fixed to special harnesses or the subject has major physical and/or mental limitations or also because of fatigue. Among others, during normal application and/or also in case of falling, fractures, skin-abrasion, bruises, hematoma, traumatic injuries and cardiovascular disorders or even sudden death may occur during this application.

(2) During various applications such as ergometry and cardiopulmonary stress tests as well as performance diagnosticsthe the intended use is to deliver mechanical energy from the treadmill to the subject. It is the intended use to stress the cardiopulmonary system of the patient to an extremely high level, where for examples heart irregularities or even heart failure occur. This is done under controlled and supervised environment. Medical staff and emergency equipment (defibrillator, ECG, etc.) has to be present at any time. Among others, during normal application and/or also in case of falling, fractures, skin-abrasion, bruises, hematoma, traumatic injuries and cardiovascular disorders or even sudden death may occur during this application.

(3) The subject may have problems at any time to catch up with the speed of the moving running belt and therefore is always in the risk of falling. Falling on a treadmill can result in serious injuries (bruises, skin-abrasions, burns, broken bones, etc.) or even death (e.g. through broken neck, cervical dislocation) Some other potential and technical risks, which are not related to the intended use:

(4) Danger of electric shock through isolation malfunction of the treadmill or ECG involved increases when the treadmill is linked via interface to ECG and so indirectly linked with electrodes to the skin of the subject. Treadmills are usually powered with single phase 110 … 240 volts or even 3-phase 3x400 Volts.

(5) Malfunction of heart rate measurement or wrong target heart rate settings may result in overload to the subject through too high loads (speed and elevation) and therefore can lead to serious health conditions or even death.

(6) Malfunction of speed control of the running belt or the interface communication with ECG and ergospirometry device may result in immediate acceleration of the running belt.

(7) Dangerous capture zones mainly at the running belt re-entry zone (gap between belt and frame at the rear roller zone) or through other moving parts and frame of the treadmill when using the elevation system, adjustable handrails, unweighting systems, etc.

(8) A number of deadly accidents are known with treadmills. Luckily there are no known deadly accidents with h/p/cosmos treadmills so far.

(9) Active therapeutic devices intended to administer or exchange energy in potentially hazardous way.

(10) When used to monitor vital processes where variations could result in immediate danger.

Intended use (specific function / purpose) in medical field

cardiopulmonary stress tests, ergometry, gait analysis, locomotion therapy for neurological patients

Indications

Diagnosis and prognosis of cardiovascular disease, specifically coronary artery disease (CAD), Arthritis in foot ankle, Femoropetrellares Syndrom, knee joint problems, anterior cruciate ligament plastic, gait analysis and gait correction for stroke patients.

Contraindications

  • The following contraindications are from the AHA/ACC guidelines published in 1997.
  • Absolute contraindications
  • Acute myocardial infarction (within 2 d)
  • Unstable angina not previously stabilized by medical therapy: Appropriate timing of tests depends on the level of risk of unstable angina as defined by the Agency for Health Care Policy and Research Unstable Angina Guidelines.
  • Uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise
  • Symptomatic severe aortic stenosis
  • Uncontrolled symptomatic heart failure
  • Acute pulmonary embolus or pulmonary infarction
  • Acute myocarditis or pericarditis
  • Acute aortic dissection

Relative contraindications: Relative contraindications can be superseded if the benefits of exercise outweigh the risks.

  • Left main coronary stenosis
  • Moderate stenotic valvular heart disease
  • Electrolyte abnormalities
  • Severe arterial hypertension: In the absence of definite evidence, the committee suggests an SBP of greater than 200 mm Hg and/or a DBP of greater than 110 mm Hg.
  • Tachyarrhythmias or bradyarrhythmias
  • Hypertrophic cardiomyopathy and any other forms of outflow tract obstruction
  • Mental or physical impairment leading to an inability to exercise adequately
  • High-degree atrioventricular (AV) block

The vast majority of treadmill exercise testing is performed on adults with symptoms of known or probable ischemic heart disease. Candidates for exercise stress testing may have stable symptoms of chest pain, may be stabilized by medical therapy following symptoms of unstable chest pain, or may have already had a myocardial infarction or a vascularization procedure.

The clinical suggestion of CAD based on patient history findings, ECG tracings, and symptoms of chest pain must be established and used as a guide to determine if treadmill exercise testing may be useful according to the Bayes theorem, which states that the diagnostic power of exercise stress testing is maximal when the pretest probability of CAD is intermediate (30-70%) based on age, sex, and the nature of the chest pain.

When the diagnosis of CAD is certain, based on age, sex, description of chest pain, and history of prior myocardial infarction, a clinical need may arise for risk or prognostic assessment to reach a decision regarding possible coronary angiography or revascularization to guide further medical management.

Myocardial infarction is a common first presentation of ischemic heart disease. This subset of patients also may require prognostic and/or risk or assessment.

(source for indications/contraindications for diagnosis and prognosis of cardiovascular disease, specifically coronary artery disease (CAD): http://emedicine.medscape.com/article/1827089-print)

Clinical studies are not required for treadmills, since:

a) performance data are available and fulfilled based on the norms EN 957-1 and EN 957-6 for treadmills;

b) treadmills have been used for more than 50 years worldwide and the clinical benefits are well documented. The clinical benefits exceed the involved risks which are arising in the application. In our risk management system based on EN14971 we have documented the control of all known risks.