1. Basics of Medical Equipment Lecture 6

2. I. Chemical sensors
A chemical sensor is a device that transforms chemical information, ranging from the concentration of a specific sample component to total composition analysis, into an analytically useful signal. The chemical information, mentioned above, may originate from a chemical reaction of the analyte or from a physical property of the system investigated.

4. An arterial blood gas (ABG) is a test that measures the oxygen tension (PaO2), Carbon dioxide tension (PaCo2), acidity (pH), oxyhemoglobin saturation (SaO2), and bicarbonate (HCO3) concentration in arterial blood.

8. II. Surgical diathermy
Electrosurgical units (diathermy machines) were first introduced during the early twentieth century to facilitate haemostasis and/or the cutting of tissue during surgical procedures.
This is achieved by passing normal electrical current via the diathermy machine and converting it into a high frequency alternating current (HFAC). The HFAC produces heat within body tissues to coagulate bleeding vessels and cut through tissue. At this high frequency of over 300,000 Hz, the nervous system and muscles are not affected when the current passes through the body.

10. Types
There are two different types of electrosurgery: monopolar and bipolar.
Monopolar electrosurgery is the emitance of the HFAC from the diathermy via an active electrode through the patients body tissues and returned back to the diathermy machine via a return electrode or patient return pad. It works because radio frequency energy is concentrated by the surgical instrument's small surface area. The electrical circuit is completed by passing current through the patient's body to a conductive pad that is connectd to the radio frequency generator. Because the pad's surface area is large relative to the instrument's tip, energy density across the pad is reliably low enough that no tissue injury occurs at the pad site. Electrical shocks and burns are possible, however, if the circuit is interrupted or energy is concentrated in some way. This can happen if the pad surface in contact is small, e.g. if the pad's electrolytic gel is dry, if the pad becomes disconnected from the radio frequency generator, or via a metal implant

11. Bipolar electrosurgery is the passage of the HFAC from the diathermy machine using only the patient's tissue grasped between a pair of bipolar forceps, to form a complete electrical circuit within the patient. Bipolar diathermy does not require a patient return pad as both active and return electrodes are combined within the forceps. Advantage of bipolar electrosurgery is that it prevents the flow of current through other tissues of the body and focuses only on the tissue in contact. This is useful in microsurgery and in patients with cardiac pacemaker.

12. III. Dialysis
Kidney dialysis is a procedure that is a substitute for many of the normal functions of the kidneys.
Dialysis allows patients with kidney failure a chance to live productive lives.
There are two types of dialysis: hemodialysis and peritoneal dialysis.
There are two major blood chemical levels that are measured are the "creatinine level" and the "blood urea nitrogen" (BUN) level. As these two levels rise, they are indicators of the decreasing ability of the kidneys to cleanse the body of waste products.

14. There are two main types of dialysis: "hemodialysis" and "peritoneal dialysis." Hemodialysis uses a special type of filter to remove excess waste products and water from the blood. Peritoneal dialysis uses a fluid that is placed into the patient's abdominal cavity through a special plastic tube to remove excess waste products and fluid from the body.
Treatments last from 2 ½ to 4 ½ hours. During this time, the dialysis staff checks the patient's blood pressure frequently and adjusts the dialysis machine to ensure that the proper amount of fluid is being removed from the patients body.

15. Cardiopulmonary bypass (CPB)
Cardiopulmonary bypass (CPB) is a technique that temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and the oxygen content of the body. The CPB pump itself is often referred to as a heart–lung machine or "the pump", and does the work of the heart and lungs during the operation.

16. The heart-lung machine consists of a chamber that receives the blood from the body, which is normally the responsibility of the heart’s right atrium. This blood is then pumped by the machine through an oxygenator, a function normally the responsibility of the right ventricle. The oxygenator removes the CO2 and adds oxygen, which is normally the work of the lungs. The pump then pumps this newly oxygenated blood back to the body, which is normally the work of the left heart. The heart-lung machine is connected to the patient by a series of tubes that the surgical team places. At the end of the operation, the surgeon gradually allows the patient’s heart to resume its normal function, and the heart-lung machine is "weaned off".

19. V. Pacemaker
A permanent pacemaker, a small device that is implanted under the skin (most often in the shoulder area just under the collarbone), sends electrical signals to start or regulate a slow heartbeat. A permanent pacemaker may be used to make the heart beat if the heart's natural pacemaker (the SA node) is not functioning properly and has developed an abnormally slow heart rate or rhythm, or if the electrical pathways are blocked.

20. Types of pacemaker
Single-chamber pacing, either the right atrium (upper chamber) or the right ventricle (lower chamber) is paced. Only one pacing lead is used.
Dual-chamber pacing, both the right atrium and right ventricle are paced. This requires two pacing leads. One lead is placed in the right atrium, and the other lead is placed in the right ventricle. Advisa MRI and Revo MRI are dual-chamber pacemakers.

21. Implantable converter defibrillator (ICD)
An implantable cardioverter defibrillator (ICD) looks very similar to a pacemaker, except that it is slightly larger. It has a generator, one or more leads, and an electrode for each lead. These components work very much like a pacemaker. However, the ICD is designed to deliver two levels of electrical energy: a low energy shock that can convert a beating heart that is in an abnormal rhythm back to a normal heartbeat, and a high energy shock that is delivered only if the arrhythmia is so severe that the heart is only quivering instead of beating.

22. A permanent pacemaker or ICD has three main components:
A pulse generator which has a sealed lithium battery and an electronic circuitry package. The pulse generator produces the electrical signals that make the heart beat. Most pulse generators also have the capability to receive and respond to signals that are sent by the heart itself.
Electrodes, which are found on each lead.

23. One or more wires (also called leads)
One or more wires (also called leads). Leads are insulated flexible wires that conduct electrical signals to the heart from the pulse generator. The leads also relay signals from the heart to the pulse generator. One end of the lead is attached to the pulse generator and the electrode end of the lead is positioned in the atrium (the upper chamber of the heart) or in the right ventricle (the lower chamber of the heart). In the case of a biventricular pacemaker, leads are placed in both ventricles.

24. VI.Defibrillator
It is medical equipment which is used to counteract fibrillation of the heart muscle and restore normal heartbeat by applying a brief electric shock. It can be used to treat defibrillation and tachycardia.

25. Types :
1. ASYNCHRONIZED
Turn the power on the patient without electrocardiogram
2. SYNCHRONIZED CARDIOVERSION (Synchronize with Cardiogram)

26. Operation 1: Place the paddles on the patient.
 Place the left (STERNUM) paddle on the right side of sternum and below the clavicle.
 Place the right (APEX) paddle on the level of 5th intercostal space and midaxillary line.

27. 2: When the patient needs defibrillation, press the CHARGE button on the APEX paddle or CHARGE/AED button on the front panel to start
When defibrillation becomes unnecessary after charging is completed
Turn the Energy/Mode Select Control to the DISARM or OFF position.
The defibrillator internally discharges charged energy
3: Check the skin-paddle contact impedance.
4: Discharge the energy to the patient.

28. WARNING: (to avoid an electrical shock)
1. When charging or discharging, do not touch anything other than the handles.
2. Do not move the defibrillator when any charged energy remains in the defibrillator.
3. Before defibrillation, all persons must keep clear of the bed and must not touch the patient or any equipment