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CHAPTER 12

CHAPTER 12. CARDIOPULMONARY PROCEDURES. PRETEST. True or False. Blood enters the right atrium from the superior and inferior vena cava. The cardiac cycle represents one complete heartbeat. A standard electrocardiogram consists of 10 leads.

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CHAPTER 12

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  1. CHAPTER 12 CARDIOPULMONARY PROCEDURES

  2. PRETEST True or False • Blood enters the right atrium from the superior and inferior vena cava. • The cardiac cycle represents one complete heartbeat. • A standard electrocardiogram consists of 10 leads. • An electrolyte facilitates the transmission of electrical impulses. • Leads V1 through V6 are known as the augmented leads.

  3. PRETEST, CONT. True or False • Electrodes that are too loose can cause an alternating current artifact. • When running an ECG, the medical assistant should work on the left side of the patient. • An ECG that it within normal limits is said to have a normal sinus rhythm. • The most serious cardiac dysrhythmia is atrial fibrillation. • The purpose of a pulmonary function test is to assess cardiac functioning.

  4. Content Outline Introduction to Electrocardiography • Electrocardiograph:instrument used to record the electrical activity of the heart • Electrocardiogram (ECG):graphic representation of the electrical activity of the heart

  5. Introduction to Electrocardiography, cont. • Purpose • Detect an abnormal cardiac rhythm (dysrhythmia) • Help diagnose damage to heart caused by myocardial infarction • Assess the effect on the heart of digitalis or other cardiac drugs • Determine the presence of electrolyte disturbances

  6. Introduction to Electrocardiography, cont. • Assess progress of rheumatic fever • Determine presence of hypertrophy of the heart chambers • Use before surgery to assess cardiac risk during surgery

  7. Introduction to Electrocardiography, cont. • ECG cannot detect all cardiovascular disorders • Cannot always detect impending heart disease • Used to assess cardiac functioning • Along with other diagnostic/laboratory tests

  8. Introduction to Electrocardiography, cont. • MA responsible for running ECG, which includes: • Preparation of patient • Operation of electrocardiograph • Identification and elimination of artifacts • Labeling the completed ECG • Care and maintenance of electrocardiograph

  9. Introduction to Electrocardiography, cont. • ECG machine formats: • Single-channel format: one lead recorded at a time • Three-channel format: three leads recorded at one time • Most offices use

  10. Three-Channel Electrocardiograph

  11. Structure of the Heart • Heart consists of four chambers • Upper chambers • Right atrium • Left atrium • Lower chambers • Right ventricle • Left ventricle

  12. Structure of the Heart

  13. Structure of the Heart, cont. • Pathway of blood through the heart • Blood enters right atrium: from superior and inferior vena cava • Brought back to heart after circulating in body • Deoxygenated: contains very little oxygen and high in carbon dioxide (CO2) • Enters right ventricle

  14. Structure of the Heart, cont. • Pumped to the lungs • By way of pulmonary artery • In lungs: • Picks up oxygen • Gives off CO2

  15. Structure of the Heart, cont. • Returns to the left atrium of heart • By way of pulmonary veins • Enters left ventricle • Most powerful chamber of the heart • Pumps blood to entire body

  16. Structure of the Heart, cont. • Pumped into the aorta to be distributed to the body • Nourishes tissues with oxygen and nutrients

  17. Conduction System of the Heart • Sinoatrial node (SA node) • Located in upper portion of right atrium • Consists of: knot of modified myocardial cells • Able to send out an electrical impulse • Without an external nerve stimulus • Initiates and regulates heartbeat

  18. Conduction System of the Heart

  19. Conduction System of the Heart, cont. • Path of impulse from SA node • Electrical impulse discharged by SA node • Impulse distributed to right and left atria: causes atria to contract • Blood forced through cuspid valves and into ventricles

  20. Conduction System of the Heart, cont. • Impulse picked up by atrioventricular (AV) node • Knot of modified myocardium • Located at base of right atrium • AV node delays impulse momentarily • Gives ventricles a chance to fill with blood

  21. Conduction System of the Heart, cont. • Impulse transmitted to bundle of His • Bundle of His is divided into right and left bundle branches • Bundle branches: relays impulse to the Purkinje fibers

  22. Conduction System of the Heart, cont. • Purkinje fibers: distributes impulse evenly to right and left ventricles • Causes ventricles to contract • Forces blood out of ventricles: into pulmonary artery and aorta • Entire heart relaxes momentarily • New impulse initiated by SA node • Cycle repeats

  23. Conduction System of the Heart

  24. Cardiac Cycle • Represents one complete heartbeat • Consists of: • Contraction of atria • Contraction of ventricles • Relaxation of entire heart

  25. Cardiac Cycle • ECG:records electrical activity that causes cardiac cycle to occur • ECG cycle:graphic representation of cardiac cycle

  26. ECG Cycle

  27. Waves • P wave • Represents electrical activity associated with contraction of atria • Known as: atrial depolarization

  28. 2. QRS complex (consists of Q, R, S waves) • Represents electrical activity associated with contraction of ventricles • Known as: ventricular depolarization

  29. Waves, cont. • T wave • Represents electrical recovery of the ventricles • Muscle cells are recovering in preparation for another impulse • Ventricular repolarization

  30. Waves, cont. • U wave • Occasionally follows T wave • Small wave • May be associated with repolarization

  31. Baseline, Segments, and Intervals • Baseline • Flat, horizontal line that separates various waves • Waves deflect either upward or downward from baseline: • Positive deflection: wave deflects upward • Negative deflection: wave deflects downward

  32. Baseline, Segments, and Intervals, cont. • ECG: divided into segments and intervals • Purpose: Interpretation and analysis of ECG

  33. Baseline, Segments, and Intervals, cont. • Segment: portion of the ECG between two waves • P-R segment: • From the end of atrial depolarization to the beginning of ventricular depolarization • Represents time needed for impulse to be delayed at AV node • S-T segment: • From the end of ventricular depolarization to the beginning of repolarization of ventricles

  34. Segments

  35. Baseline, Segments, and Intervals, cont. • Interval: length of a wave or length of wave with a segment • P-R interval: • From the beginning of atrial depolarization to the beginning of ventricular depolarization • Q-T interval: • From the beginning of ventricular depolarization to the end of repolarization of the ventricles

  36. Baseline, Segments, and Intervals, cont. • Baseline (after T wave or U wave): • Period when entire heart returns to resting or polarized state

  37. Intervals

  38. Electrocardiograph Paper • Paper divided into two sets of squares • Small square: 1 mm high and 1 mm wide • Large square: 5 mm high and 5 mm wide • Each large square made up of 25 small squares

  39. Electrocardiograph Paper

  40. Electrocardiograph Paper, cont. • Physician uses graph to measures waves, intervals, and segments • Determines if ECG is within normal limits • Paper consists of: • Black or blue base with white plastic coating • Black or red graph printed on top of coating

  41. Electrocardiograph Paper, cont. • Heated stylus moves over heat-sensitive paper • Melts away plastic coating • Results in recording of the ECG cycles • Paper is also pressure-sensitive • Handle carefully to avoid making impressions • May interferes with proper reading of ECG

  42. Standardization of the Electrocardiograph • Electrocardiograph must be standardized for every recording • Quality control measure • Ensures an accurate and reliable recording • Means ECG run on one electrocardiograph: compares in accuracy with a recording run on another machine

  43. Standardization of the Electrocardiograph, cont. • Normal standardization mark: • Height: 10 mm (10 small squares) • Width: approximately 2 mm wide (2 small squares)

  44. Standardization of the Electrocardiograph, cont. • Three-channel machine: automatically records standardization marks on recording • If standardization mark is more or less than 10 mm high: • Machine must be adjusted • Consult operating manual for adjustment info

  45. Electrocardiograph Leads • Consists of 12 leads • Each lead • Provides an electrical "photograph" of heart's activity from a different angle • Results in 12 "photographs" of the heart • Facilitates thorough interpretation of heart's activity

  46. Electrocardiograph Leads, cont. • Electrode • Made of a substance that is a good conductor of electricity • Picks up electrical impulses given off by the heart • Conducts impulse into machine by lead wires

  47. Electrode

  48. Electrocardiograph Leads, cont. • Amplifier: device located in machine that amplifies the electrical impulses • Electrical impulses given off by the heart: very small • Must be made larger (amplified)

  49. Electrocardiograph Leads, cont. • Galvanometer: changes amplified voltages into mechanical motion • Stylus (heated): • Records heart tracing on ECG paper • By melting plastic coating on ECG paper

  50. Electrocardiograph Components

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