Inspection of Medical Devices

Electrocardiographs are nowadays standard part of diagnostic procedure in healthcare systems since they have high significance in diagnosis of large number of diseases and disorders. Due to development of technology, especially electronics, these devices have been revolutionized since the first prototype was invented. Nowadays, these devices are able to perform automated diagnosis and measure multiple parameters at once. Multiple international standards define device life circle, from production to disposal. However, this sophistication of ECG devices raises numerous questions regarding safety and accuracy. This chapter describes basic principles of electrocardiography and ECG devices as well as gives overview of requirements in area of safety and performance inspection of these devices.

The main purpose of the present chapter is to provide an overview of noninvasive blood pressure measuring devices and their inspection and testing. The chapter first introduces systematic classification of methods for blood pressure measurement. Moreover strengths and weaknesses of each method are discussed. Devices for noninvasive blood pressure measurement are described. Several international standards for evaluating the accuracy of blood pressure monitors (AAMI/ANSI SP10, BHS, DIN, IEC, etc.) are compared. After that a section on the inspection and testing of noninvasive blood pressure measuring devices as recommended by the International Organization of Legal Metrology (OIML) is presented. At the end of this chapter a short summary is given emphasizing the importance of accuracy testing of noninvasive blood pressure measuring devices.

This chapter provides an overview of the safety aspects of application of ultrasound in medicine. It starts with the short history of ultrasound methods and devices as well as basic principles of ultrasound imaging systems. The application of ultrasound in medicine greatly evolved and nowadays it can be divided into two main areas: imaging and therapy. In order to assure a safe and responsible application of ultrasound in medicine one should be aware of physical processes which can be produced in tissue by ultrasound such as temperature rise, cavitation and acoustic streaming. The importance of understanding how these processes can affect the human cell is self-explanatory. In order to better understand the guidelines for testing and quality control of ultrasonic devices it is necessary to give an overview of basic output parameters. Only the most important parameters from the point of safe use of ultrasound are described, e.g. acoustic pressure, acoustic power and intensity. In order to protect the public against inappropriate exposure when ultrasound is used for medical applications, international standards and national regulations are developed. Diagnostic ultrasound imaging is very often the basis for diagnostic decision; therefore it is also necessary to include such systems into a comprehensive quality assurance programme. Ultrasound systems used for therapy have larger intensities though there are additional safety requirements compared to diagnostic systems. The ultrasound intensity, effective radiation area and beam non-uniformity ratio and are parameters which should be monitored.

The chapter deals with the inspection of neurodiagnostic equipment based on measurement of electrophysiological signals in order to detect eventual problems and prevent them from becoming serious safety risks. In the first section of the text a brief description of the human neuromuscular system is given, followed by description and short historical overview of considered neurodiagnostic methods: electroencephalography (EEG) including evoked potentials (EP), electromyography (EMG) and nerve conduction study (NCS). Operating principle of computer-controlled neurodiagnostic instrument is explained using generic block diagram. The next sections discuss potential harms and hazards associated with the use of neurodiagnostic equipment as well as standards and regulations concerning basic safety and essential performance requirements for mentioned equipment. The last section describes inspection procedure for periodical testing of modern computer-based nerodiagnostic instruments in the field.

Over the last 50 years of use, defibrillation has been proved to be safe and efficient method to terminate lethal arrhythmias like ventricular fibrillation and ventricular tachycardia without pulse. However, in order to ensure safety and efficacy of this therapy, it is necessary to have a defibrillator which has been tested and proved to be fully functional. Preventive maintenance of all medical devices is highly important to ensure correct diagnosis and therapy, but for defibrillators it is even more important, because a defibrillator is a life-saving device and it is used in the case when a patient life is in danger. Any failure or partial failure of a defibrillator functionality may result in death of a patient. Therefore, there is a zero-tolerance on discrepancies between full functionality of defibrillator, as described in device documentation and actual functionality of defibrillator. Preventive maintenance of defibrillator consists of series of tests which need to be done on the device, with use of special measuring equipment. The most important tests include measurement of output energy which is being delivered from a defibrillator, at all energy levels, to a certain testing impedance. It is also possible to repeat this testing on variable impedance values, and that is highly recommended, because actual patient impedance values will also vary. The documentation for each defibrillator defines tolerance of the delivered energy value, so the actual value must be within prescribed tolerance values, in order to declare the device fully functional. In this chapter, the principles of operation are described too, as well as related standards and the simplest to use kind of defibrillators, called automatic external defibrillators (AEDs).

Respirators are used in intensive care units and in operating rooms. It consists of filtering, air compression, and humidifying control board units. A respirator is a device that combines the patient’s respiratory tract to assist the respiratory system in conditions where the patient has difficulty in breathing or after operations. The device supplies controlled air to the patient by the inner compressor. The breakdown of the oxygen sensor and the heating of the circuit boards (if the filter is not cleaned) are the most common problems in respirators. They may not stabilize with required values over time and the tester is used to maintain stability. The device must be calibrated regularly or if the gauge of the test device does not match the standard values of gas flow, volume, pressure and oxygen parameters. The anaesthesia machine delivers pressurised medical gases like air, oxygen, nitrous oxide, heliox etc. and controls the gas flow individually. It composes a known and controlled gas mixture at a known flow rate and then delivers it to the gas outlet of the machine. Therefore, the fresh gas flow is serviced to the anaesthesia circle breathing system in order to make artificial respiration in the patient and monitor vital functions closely. For patient safety, the most important thing is to check out the system regularly and in pre-use and to ensure that there exists a ready and functioning alternative solution for ventilating the patient’s lungs.

Dialysis machines act as artificial kidney performing extracorporeal blood purification to remove excess water, detoxify the blood and balance the blood composition. The chapter presents development of dialysis from experiments to regular life-saving clinical practice, leading to modern dialysis machine organization and functionality. Function deterioration of a hemodialysis device, as a potential harm for a patient safety, is discussed. Further on, overview of standards related to hemodialysis machines safety and risk management is presented. The chapter concludes with a description of a procedure for safety performance inspection focused on key dialysis parameters: temperature and conductivity of dialysate, and blood pressure.

Infant incubators revolutionized the way medical care is provided to prematurely born infants or infants born with different kind of diseases and health problems. Due to development of technology infant incubators have been significantly improved from the time they were invented, but the main functions remained the same. Infant incubators provide optimal environmental conditions for infants to recover. This is achieved by controlling parameters such as temperature, relative humidity, air flow rate, oxygen concentration, suitable for medical treatment of certain conditions. Increased sophistication of medical devices, including infant incubators raises numerous questions regarding safety of device and reliability of controlled parameters within medical device. Regulatory bodies define requirements for infant incubators in manufacturing process, distribution and disposal. However, questions on requirements and methods for inspection of safety and performance of these devices are addressed more frequently. These inspections are most usually performed by trained clinical professionals who use specialized devices, analysers (phantoms). Using these calibrated analysers, traceability to international (SI) units of medical device measurement is ensured, which raises reliability of medical device treatment. This chapter describes types of infant incubators that are used in today’s healthcare system, as well as requirements on infant incubators stated in international standards and medical device directives. Description of infant incubator analysers is given at the end of this chapter.

Infusion pumps are ME (Medical Electrical) devices intended to regulate the intravenous flow of liquids through a positive pressure generated by the pump itself. Infusion pumps are used in all those wards where patients need life support and a proper nutrition. Even if infusion pumps became almost totally automated devices, a proper training of users is still necessary. In order to reduce the number of errors reported, the first step to do is to teach to all users how to prevent serious problems to patients. It is necessary to identify what are the potential risks that may be encountered in using these devices and especially the sources from which they derive. For each kind of hazard a protection system must be available. Maintenance tasks and accuracy tests are described in this chapter. Also critical issues in management and safety are described and analysed. The designers of smart infusion pumps must make sure to create products with functions that can be easily understood and used by the operators. Only thanks to the collaboration between manufacturers, technicians, doctors and nurses it becomes possible to organize the maintenance of any device, infusion pumps included.

Appropriate treatment of patients largely depends on the correct and accurate diagnosis of medical experts. When diagnosing diseases and treating patients, medical personnel rely on results from tests received using various medical devices. Medical devices are classified as products of special importance for retaining the health of many people, and as such are subject to numerous regulatory investigations that determine the entire life-cycle of the devices, from production, sales, use and disposal. The aspect of safety, accuracy and precision, that is, the functionality of medical devices, is becoming increasingly important given that during the use of medical devices various factors lead to the degradation of performance. In this case, a strict, professional and independent inspection of the functionality of medical devices is of the utmost importance for ensuring precise diagnostics and treatment of the patient. The safety aspect of medical devices in health care is regulated worldwide by various agencies or by the application of international standards in healthcare facilities that ensure that the functionality of medical devices is checked at least once a year. Also, the introduction of medical devices into legal metrology in all countries of the world has made great strides in increasing safety, accuracy and quality of medical services, resulting in optimization of maintenance costs for medical devices. The aim of this study, with the help of statistical and economic methods, is to analyse the connections between a number of medical devices over which periodic inspection was initiated with increasing accuracy and safety of them, and to present and quantify the cause-effect reaction in the form of cost reduction for medical institutions.