Patient Monitoring machine in medical engineering

Patient monitor machine

1. The long-term objective of patient monitoring is generally to decrease mortality and morbidity by: Organizing and displaying information in a form meaningful for improved patient care’ Correlating multiple parameters for clear demonstration of clinical problems. Processing the data to set alarms on the development of abnormal conditions. Providing information, based on automated data, regarding therapy. Ensuring better care with fewer staff members.

2. Cardiac Monitor The most important physiological parameters monitored in the intensive care unit are the heart rate and the morphology or shape of the electrical waveform produced by the heart. A cardiac monitor is specifically useful for monitoring patients with cardiac problems and the special areas in the hospitals where they are generally used are known as cardiac care units or coronary care units (CCU).

3. These instruments are also called ‘ Cardioscopes ’ and comprise of: Disposable type pregelled electrodes to pick up the ECG signal. Amplifier and a cathode ray tube (CRT) for the amplification and display the ECG which enable direct observation of the ECG waveform. A heart rate meter to indicate average heart rate with audible beep or flashing light or both with each beat. An alarm system to produce signal in the event of abnormalities occurring in the heart rate.

4. The following precautions should be taken to achieve good ECG display in the presence of electrosurgery interference (Benders, 1976): The electrosurgery return plate should be directly under the surgical site, as far as possible. The ECG electrodes should be placed at the maximum possible distance away from the surgical site. The electrodes should be equidistant from the surgical site. All monitoring electrodes must be placed either on the frontal surface or on the posterior surface. Only shielded ECG patient cables and electrode leads must be used.

5. Bedside patient monitors Systems They are designed to monitor different parameters but the common feature amongst all is the facility to continuously monitor and provide non-fade display of ECG waveform and heart rate . Some instruments also include pulse, pressure, temperature and respiration rate monitoring facilities.

6. A microprocessor-based bedside patient monitoring. The system basically consists of three circuit blocks: Preamplifier section , Logic boards and Display part . The system is designed to display an electrocardiogram, heart rate with high and low alarms, pulse rate, dynamic pressure or other waveforms received from external preamplifiers. It also gives immediate and historical data on the patient for trend information on heart rate, temperature, and systolic and diastolic blood pressures for periods up to eight hours.

7. Patient monitors are also known as vital sign monitors as they are primarily designed to measure and display vital physiological parameters.

8. Indirect Blood Pressure Measurement - Sphygmomanometer

9. Indirect Blood Pressure Measurement - Sphygmomanometer

10. Indirect Blood Pressure Measurement - Sphygmomanometer

11. Indirect Blood Pressure Measurement - Sphygmomanometer The pressure cuff on the upper arm is first inflated to a pressure well above the systolic pressure. At this point no sound can be heard through the stethoscope, which is placed over the brachial artery, for that artery has been collapsed by the pressure of the cuff. The pressure in the cuff is then gradually reduced.

12. Sphygmomanometery … When the systolic peaks are higher than the occlusive pressure, the blood spurts under that cuff and causes a palpable pulse in the wrist (Riva- Rocci Method) Audible sounds ( Korotkoff (named after Dr. Nikolai Korotkoff ) sounds) generated by the flow of blood and vibrations of the vessel under the cuff are heard through the stethoscope.

13. Sphygmomanometery … The pressure of the cuff that is indicated on the manometer when the first Korotkoff sound is heard is recorded as the systolic blood pressure. As the pressure in the cuff is continues to drop, the Korotkoff sounds continue until the cuff pressure is no longer sufficient to occlude the vessel during any part of the cycle. Below this pressure the Korotkoff sounds disappear , marking the value of the diastolic pressure.

14. Sphygmomanometery … Auscultatory (based on the Korotkoff sounds) technique is simpler and requires a minimum of equipment. Cannot be used in noisy environments. Palpation (based on pulse on the blood vessel) technique doesn’t require a noise free environment. Normal respiration and vasomotor waves modulate the normal blood-pressure levels.

15. Automated Indirect Blood Pressure measurement techniques Involves an automatic sphygmomanometer that inflates and deflates an occlusive cuff at a predetermined rate. A sensitive detector is used to measure the distal pulse or cuff pressure.

16. Automated Auscultatory device Microphone replaces the stethoscope for sensing the Korotkoff sounds. The process begins with a rapid (20-30mm Hg/s) inflation of the occlusive cuff to a preset pressure about 30mm Hg higher that the suspected systolic pressure. The flow of blood beneath the cuff is stopped by the collapse of the vessel.

17. Automated Auscultatory device Cuff pressure is then reduced slowly (2-3 mm Hg/s). The first Korotkoff sound is detected by the microphone, at which time the level of the cuff pressure is stored.

18. Automated Auscultatory device The muffling and silent period of the Korotkoff sound is detected, and the value of the diastolic pressure is also stored. After a few minutes the instrument displays the systolic and diastolic pressure and recycles the operation

19. Ultrasonic Based Blood Pressure Measurement Employs a transcutaneous Doppler sensor that detects the motion of the blood-vessel walls in the various states of occlusion. The Doppler ultrasonic transducer is focused on the vessel wall and the blood. The reflected signal (shifted in frequency) is detected by the receiving crystal and decoded.

20. Ultrasonic Based Blood Pressure Measurement…

21. Ultrasonic Based Blood Pressure Measurement… The difference in frequency, in the range of 40 to 500 Hz, between the transmitted and received signals is proportional to the velocity of the wall motion and the blood velocity.

22. Ultrasonic Based Blood Pressure Measurement… As the applied pressure is further increased, the time between the opening and closing decreases until they coincide. The reading at this point is the systolic pressure. When the pressure is cuff is reduced, the time between the opening and closing increases until the closing signal from one pulse coincides with opening signal from the next. The reading at this point is the diastolic pressure.

23. Ultrasonic Based Blood Pressure Measurement… Advantages: Doesn’t require a noise free environment. Disadvantage: Movement of the subject‘s body cause changes in ultrasonic path between the sensor and the blood vessel.