Cardiopulmonary Procedures



Cardiopulmonary Procedures



Key Terms






























































LEARNING OBJECTIVES PROCEDURES
Electrocardiography

 Record a 12-lead, three-channel ECG.
Holter Monitor Electrocardiography

  
Cardiac Dysrhythmias

 Identify cardiac dysrhythmias on a 12-lead ECG.
Pulmonary Function Testing

  
Peak Flow Measurement

 Measure a patient’s peak flow rate.
Home Oxygen Therapy

  


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Introduction to Electrocardiography


The electrocardiograph is an instrument used to record the electrical activity of the heart. The electrocardiogram (ECG) is the graphic representation of this activity. The ECG exhibits the amount of electrical activity produced by the heart and the time required for the impulse to travel through the heart.


Cardiovascular disorders can cause abnormal changes to occur on the ECG. Because of this, electrocardiography is used for the following purposes:



• To evaluate the following symptoms: chest pain, shortness of breath, dizziness, or heart palpitations


• To detect an abnormality in the heart’s rate or rhythm (dysrhythmia)


• To detect the presence of impaired blood flow to the heart muscle (cardiac ischemia)


• To help diagnose damage to the heart caused by a myocardial infarction


• To determine the presence of hypertrophy (enlargement) of the heart


• To detect inflammation of the heart muscle (myocarditis) or the lining of the heart (pericarditis)


• To assess the effect on the heart of digitalis and other cardiac drugs


• To determine the presence of electrolyte disturbances


• To assess the progress of rheumatic fever


• To detect congenital heart defects


• Performed before surgery to assess cardiac risk during surgery


• As part of a complete physical examination


A 12-lead resting ECG cannot detect all cardiovascular disorders nor can it always detect impending heart disease such as a myocardial infarction. An ECG is taken with the patient in a resting state and records only about 10 seconds of the heart’s electrical activity. If a patient has a dysrhythmia that occurs intermittently, the abnormal heartbeat may not occur during this brief time period. A patient who experiences angina pectoris does not typically have symptoms while in a resting state, and an ECG run on such a patient may appear normal. Because of this, an ECG must be used in combination with the patient’s symptoms, health history, physical examination, and other diagnostic and laboratory tests to obtain a complete assessment of cardiac functioning.


The medical assistant is frequently responsible for recording ECGs in the medical office. The medical assistant must acquire knowledge, and skill must be acquired in the following aspects of electrocardiography: preparation of the patient, operation of the electrocardiograph, identification and elimination of artifacts, and care and maintenance of the electrocardiograph.


Electrocardiographs are available in single-channel and three-channel recording formats. Because most medical offices use a three-channel ECG, the information in this chapter focuses on the three-channel electrocardiograph (Figure 27-1).


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Figure 27-1 A three-channel electrocardiograph.


Putting It All into Practice


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My name is Janet Canterbury, and I work in the medical laboratory of an internal medicine office. I also run electrocardiograms, apply and remove Holter monitors, perform pulmonary function tests, and assist with cardiac stress testing.


One of my most rewarding experiences was when a young woman came into the office with severe chest pain. I immediately helped her back to an examining room. I ran an electrocardiogram, as ordered by the physician. After the physician read the electrocardiogram, he indicated the results did not look good and that the patient would have to be transported to the hospital. I went into the patient’s room to comfort her. She asked me if she was going to have to go to the hospital. I replied, “Possibly.” She immediately said, “No!” Then I began to explain to her how important it was to have more tests to make sure she would be alright. She finally agreed to go. After being taken to the hospital by an ambulance, she was later transferred to another hospital for a heart catheterization. A few weeks passed, and she came into the office. She hugged me and thanked me for possibly saving her life. It felt so good that I could help make a difference in a patient’s life. image



Cardiac Cycle


The cardiac cycle represents one complete heartbeat. It consists of the contraction of the atria, the contraction of the ventricles, and the relaxation of the entire heart (as described previously). The electrocardiograph records the electrical activity that causes these events in the cardiac cycle. The ECG cycle is the graphic representation of the cardiac cycle (Figure 27-2).


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Figure 27-2 ECG cycle.


Waves


The normal ECG cycle consists of a P wave; the Q, R, and S waves (known as the QRS complex); and a T wave. The ECG cycle is recorded from left to right, beginning with the P wave.



P wave The P wave represents the electrical activity associated with the contraction of the atria, or atrial depolarization.


QRS complex The QRS complex represents the electrical activity associated with the contraction of the ventricles, or ventricular depolarization, and consists of the Q wave, the R wave, and the S wave. The ventricles are larger than the atria and therefore require a stronger electrical stimulus to depolarize the ventricles. That is why the R wave is taller than the P wave on the ECG graph cycle.


T wave The T wave represents the electrical recovery of the ventricles, or ventricular repolarization. The muscle cells are recovering in preparation for another impulse. (NOTE: Electrical recovery, known as atrial repolarization, occurs following the P wave. This repolarization occurs at the same time as ventricular depolarization [QRS complex]. Because of this, atrial repolarization is masked or hidden by the QRS complex and does not appear as a separate wave on the ECG cycle.)


U wave Occasionally, a U wave follows a T wave. It is a small wave that is associated in some as yet undefined way with repolarization of the Purkinje fibers or repolarization of the papillary muscles of the heart.



Baseline, Segments, and Intervals


The flat, horizontal line that separates the various waves is known as the baseline. Following the U wave, the heart is at rest or polarized. Because no electrical activity is occurring in the heart during this time, the electrocardiograph does not have anything to record, which is why the baseline is flat.


The waves deflect either upward (positive deflection) or downward (negative deflection) from the baseline. The ECG cycle between the P wave and the T wave is divided into segments and intervals for the purpose of interpretation and analysis of the ECG by the physician. A segment is the portion of the ECG between two waves, and an interval is the length of a wave or the length of a wave with a segment.





Electrocardiograph Paper


Electrocardiograph paper is divided into two sets of squares for the accurate and convenient manual measurement of the waves, intervals, and segments (Figure 27-3). Each small square is 1 mm high and 1 mm wide. Each large square (made up of 25 small squares) is 5 mm high and 5 mm wide. By manually measuring the various waves, intervals, and segments of the ECG graph cycle with ECG calipers or an ECG ruler, the physician is able to determine whether the electrical activity of the heart falls within normal limits. Heart disease can trigger abnormal changes in the ECG cycle, causing the results to fall outside of normal limits. For example, cardiac ischemia (often due to coronary artery disease) can cause a depressed S-T segment and an inverted T wave. A myocardial infarction can cause a larger than normal Q wave and an elevated S-T segment.


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Figure 27-3 Diagram of ECG paper with a section enlarged to indicate the sizes of the large and small squares.

Electrocardiograph paper contains a thermosensitive coating. A black or red graph is printed on top of this coating. The electrocardiograph uses a thermal print head to produce the ECG tracing. The print head has the ability to generate heat in a prescribed pattern. When the thermosensitive paper comes in contact with the heated print head, the coating turns black in the areas where it is heated, producing the ECG tracing. In addition to being heat sensitive, ECG paper is pressure sensitive and should be handled carefully to avoid making impressions that would interfere with proper reading of the ECG.



Standardization of the Electrocardiograph


The electrocardiograph machine must be standardized, or calibrated, when an ECG is recorded. This is a quality control measure that ensures an accurate and reliable recording. It also means that an ECG run on one electrocardiograph compares in accuracy with a recording run on another machine. An ECG run on a properly calibrated electrocardiograph results in an accurate and reliable representation of the electrical activity of the patient’s heart.


By international agreement, 1 millivolt (mV) of electricity should cause the stylus to move 10 mm high in amplitude (10 small squares). During the recording, the machine allows 1 mV to enter the electrocardiograph machine, which should result in an upward deflection of 10 mm. The marking that occurs on the ECG paper is known as a standardization mark (Figure 27-4). The width of the mark made by the machine is approximately 2 mm (two small squares). A three-channel electrocardiograph automatically records standardization marks on the ECG; a standardization mark is recorded at the beginning and end of each of the ECG strips included in the three-channel recording (see Figure 27-9). If the standardization mark is more or less than 10 mm in amplitude, it must be adjusted; otherwise, the ECG recording may not be accurate. The manufacturer’s operating manual must be consulted for proper adjustment information. An electrocardiograph must never be adjusted without use of the operating manual.


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Figure 27-4 Standardization mark.


Electrocardiograph Leads


The standard ECG consists of 12 leads. A lead is a tracing of the electrical activity of the heart between two electrodes. Each lead provides an electrical “photograph” of the heart’s activity from a different angle. Together, the 12 leads, or “photographs,” facilitate a thorough interpretation of the heart’s activity.


The electrical impulses given off by the heart are picked up by electrodes and conducted into the machine through lead wires. Electrodes are composed of a substance that is a good conductor of electricity. The electrical impulses given off by the heart are very small (0.0001 to 0.003 volt). To produce a readable ECG, they must be made larger, or amplified, by a device known as an amplifier, located within the electrocardiograph. The amplified voltages are changed into mechanical motion by the galvanometer and recorded on the electrocardiograph paper by a thermal print head (Figure 27-5).


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Figure 27-5 Diagram of the basic components of the electrocardiograph. The limb electrodes are attached to the fleshy parts of the limbs, and the lead wires are arranged to follow body contour. The patient cable is not dangling, and the power cord points away from the electrocardiograph.

Ten lead wires are attached to the patient and are used to take the 12 electrical “photographs” of the heart. There are four limb lead wires: the right arm lead wire (RA), the left arm lead wire (LA), the right leg lead wire (RL), and the left leg lead wire (LL). The right leg lead wire is known as the ground. It is not used for the actual recording, but serves as an electrical reference point. The chest lead wires are abbreviated with a “V” and use six chest lead wires.



Electrodes


Disposable electrodes are used to record a resting 12-lead electrocardiogram. The electrode contains a thin layer of a metallic substance; this metallic substance is a good conductor of electricity. The electrode is square in shape and has a tab extending from one end (Figure 27-6, A). The tab allows for the firm attachment of an alligator clip (Figure 27-6, B).


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Figure 27-6 Resting 12-lead ECG electrodes. A, Disposable resting 12-lead electrode. B, The tab allows for attachment of the alligator clip. C, The back of the electrode contains an electrolyte gel combined with an adhesive. D, Disposable 12-lead electrodes are packaged in a foil-lined pouch and come on a card that contains 10 electrodes.

The back of the electrode contains an electrolyte gel combined with an adhesive (Figure 27-6, C). An electrolyte is a substance that facilitates the transmission of the heart’s electrical impulse. Skin is a poor conductor of electricity; therefore, an electrolyte must be used when recording an ECG. The adhesive allows for firm adherence of the electrode to the patient’s skin. There is no adhesive on the tab of the electrode to allow for attachment of the alligator clip. The electrode is applied to the skin and held in place with its adhesive backing; it is thrown away after use.


Disposable 12-lead electrodes come on a card containing 10 electrodes (Figure 27-6, D). A foil-lined pouch is used to hold 10 cards of electrodes (or 100 electrodes per pouch). The foil-lined pouch preserves moisture to prevent the electrolyte from drying out.


Each electrode pouch (and the box containing the pouches) is stamped with an expiration date. The medical assistant must always check the expiration date of the electrodes before applying them. The electrolyte gel on outdated electrodes may be dried out; a dried out electrolyte is unable to transmit a good ECG signal.


Electrodes are sensitive to environmental conditions and must be stored properly to prevent electrolyte drying. Electrodes should be stored in a cool area (less than 75° F or 24° C) away from sources of heat. When an electrode pouch is opened, the medical assistant should seal the pouch by folding over the end of it and then place the pouch (containing the remaining electrode cards) in a zipper-lock plastic bag to preserve moisture.




Augmented Leads


The next three leads are the augmented leads: aVR (augmented voltage—right arm), aVL (augmented voltage—left arm), and aVF (augmented voltage—left leg or foot). Lead aVR records the electrical current traveling between the right arm electrode and a central point between the left arm and left leg. Lead aVL records the electrical current traveling between the left arm electrode and a central point between the right arm and left leg. Lead aVF records the electrical current traveling between the left leg electrode and a central point between the right and left arms. Leads I, II, III, aVR, aVL, and aVF provide an electrical “photograph” of the heart’s activity from side to side and from the top to the bottom of the heart (see Figure 27-7).



Highlight on Cardiac Stress Testing




Purpose


The purpose of cardiac stress testing is as follows:



1. To evaluate symptoms of ischemic heart disease that cannot be assessed by a resting electrocardiogram. Ischemic heart disease occurs as a result of inadequate blood supply to the myocardium, which is most commonly caused by atherosclerosis. Atherosclerosis is a condition in which fibrous plaques of fatty deposits and cholesterol build up on the inner walls of arteries. This causes narrowing and partial blockage of the lumen of these arteries, along with hardening of the arterial wall. Atherosclerosis in the coronary arteries is called coronary artery disease (CAD). During rest, the myocardium supplied by the partially blocked artery may receive an adequate blood supply. If the individual exercises, however, the artery may not be able to supply enough blood to the myocardium, resulting in myocardial ischemia. Myocardial ischemia can cause chest discomfort and certain abnormal changes on the ECG.


2. To assist in evaluating symptoms indicating the presence of cardiac dysrhythmias.


3. To assess the effectiveness of cardiac drug therapy.


4. To follow the course of rehabilitation after a myocardial infarction or a cardiac surgical procedure, such as a coronary bypass operation or a coronary stent placement.


5. To determine an individual’s fitness level for a strenuous exercise program, such as jogging.




How the Test Works




• Cardiac stress testing involves the continuous electrocardiographic monitoring of an individual during physical exercise. During exercise, the body’s need for oxygen places added demands or “stress” on the heart, making it work harder. A cardiac stress test evaluates the response of the heart to maximum or near-maximum exertion.


• A resting 12-lead ECG is usually performed before a cardiac stress test, and the results of the resting ECG are compared with the results of the cardiac stress test.


• The stress test is accomplished by having the patient use a treadmill while connected to an electrocardiograph machine through lead wires and electrodes (see illustration).


• The intensity of the physical exertion starts with a slow “warm-up” walk on the treadmill. The speed and incline of the treadmill are gradually increased every 3 minutes until the patient’s target heart rate is reached. During this time, the ECG is continuously displayed on a computer screen. The patient’s blood pressure, heart rate, and physical symptoms are also monitored during the test.


• If the signs and symptoms of cardiac ischemia appear, the test is stopped. These symptoms include severe dyspnea, chest discomfort or pain, pallor, weakness, and dizziness. The test is also stopped if the ECG shows abnormal changes, if a serious, irregular heartbeat occurs, or if there is an abnormal change in blood pressure.


• Once the exercising is complete, the patient’s blood pressure, heart rate, and ECG are monitored until they return to normal.




Chest Leads


The last six leads are the chest, or precordial, leads: V1, V2, V3, V4, V5, and V6. These leads record the heart’s voltage from front to back. The electrical current traveling through the heart is recorded from a central point “inside” the heart to a point on the chest wall where the electrode is placed. These points correspond to the chest electrode placement sites. Figure 27-8 shows the proper location of the electrodes for the six chest leads. To ensure an accurate and reliable recording, the medical assistant must be able to locate these electrode placement sites accurately (by palpating the patient’s chest). For example, if V1 and V2 are placed in the third intercostal spaces (instead of the fourth intercostal spaces), changes can occur to the P and T waves, which can falsely indicate heart disease. When first learning to locate the electrode sites for each chest lead, it helps to mark their locations on the patient’s chest with a felt-tipped pen.


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Figure 27-8 Recommended positions for ECG chest electrodes:



What Would You Do? What Would You Not Do?



Case Study 1


Camilla Rossi is 22 years old and works at a Waffle House during the day and goes to business school at night. She comes to the office because she has been experiencing some heart problems. Over the past month, she has had three episodes of tachycardia, palpitations, trouble breathing, and profuse sweating. She is really scared that she has heart disease. Her grandfather just died from a heart attack, and she is afraid she will die next. The physician orders an ECG, but Camilla is reluctant to have the procedure. She is embarrassed about having to disrobe from the waist up, and she is worried that she will get shocked by all the wires coming out of the machine. She says that she does not have health insurance, and she does not know how she would pay for such a fancy test. She wants to know whether there is a less expensive way to find out what is wrong with her. image





Maintenance of the Electrocardiograph


Electrocardiographs require periodic maintenance. The casing of the electrocardiograph should be cleaned frequently with a soft cloth, slightly dampened with a mild detergent, to remove dust and dirt. Commercial solvents and abrasives should not be used because they can damage the finish of the casing.


The patient’s cables, lead wires, and power cord should be cleaned periodically with a cloth moistened with a disinfectant cleaner. The cables should never be immersed in the cleaning solution because this could damage them. Inspect the cables frequently for cracks or fraying, and replace them if needed. Check the metal tip of each lead wire for adhesive/electrolyte gel residue, which can interfere with the transmission of a good ECG signal from the electrode. Remove any residue with an alcohol wipe using pressure and friction.


The reusable alligator clips should be cleaned thoroughly with an alcohol wipe after patient use. Check the alligator clips periodically to make sure they fit snugly on the metal tip of each lead wire.



Electrocardiographic Capabilities


Electrocardiographs have a variety of capabilities that permit specific recording and transmittal options.



Three-Channel Recording Capability


An electrocardiograph with a three-channel recording capability can record the electrical activity of the heart through three leads simultaneously. This is in contrast to a single-channel electrocardiograph, which records only one lead at a time. The advantage of a three-channel electrocardiograph is that an ECG can be produced in less time than would be required if each lead were recorded separately.


The leads that are recorded simultaneously are leads I, II, and III; followed by aVR, aVL, and aVF; followed by V1, V2, and V3; followed by V4, V5, and V6. Each lead is automatically labeled by the electrocardiograph with its appropriate abbreviation.


Recording three leads at one time requires three-channel recording paper, which is designed in a standard image × 11-inch format. This size printout fits easily into a paper-based medical record (PPR). Most three-channel electrocardiographs have a copy capability that quickly produces a duplicate copy of an ECG that has just been recorded. Some three-channel electrocardiographs have a memory storage capability in which a specified number of ECGs can be stored in the machine for later retrieval. In this way, an ECG that has been misplaced can be retrieved from the electrocardiograph’s memory and printed out again. Figure 27-9 is an example of a three-channel ECG recording that also includes a rhythm strip. Procedure 27-1 describes how to run a 12-lead three-channel ECG.



image Procedure 27-1   Running a 12-Lead, Three-Channel Electrocardiogram  image


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Apr 16, 2017 | Posted by in NURSING | Comments Off on Cardiopulmonary Procedures

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