Principles EKG 1 Flashcards
What is monitoring?
Monitoring is making repeated or continuous observations or measurements of the patient, their physiologic function, and the function of life supporting equipment, for the purpose of guiding management decisions, including when to make therapeutic interventions and assessments of those interventions
What is electrocardiography?
Source of EMF in a 3-D space that is projected on planer surfaces
What three things do we look at on the ECG for anesthesia?
Rate
rhythm
ST segments
Where does the myocardial electrical activity start?
Initiates at the SA node
What does the SA node stand for and what does it mean?
Sinal atrial node
Means that the activity is sinus in rhythm
What is the electrically conductive tissue inside the body?
Volume conductors
Ie. Blood, pericardial fluid, interstitial fluid
How does air and other gases affect conductivity?
Air acts as a block in conductance
True or false: pores and capacitive coupling provide electrical access to the volume conductors from outside the body.
True
How are the half cell potentials that are produced between the skin and electrodes overcome?
By using amplifiers so that the half cell potentials are canceled out or blocked
Which amplifier is used so that the effects of the two half cell potentials are canceled out
Differential input DC amplifier
Which amplifier is used so that the DC voltage is blocked?
AC coupled amplifier
What type of amplifiers or most used in the OR today?
AC coupled differential amplifiers
Because of their stable half cell potential which electrodes are used in most medical applications
Silver-silver chloride (Ag-AgCl)
What is the most common mechanism that creates artifact signals?(That is signal’s that could possibly obscured the real signal)
Electrode slippage
What is the most common type of electrode used today?
Column electrodes
These keep the electrode at a fixed distance from the skin
What is one of the original type of electrodes used that connects a metallic plate that is held to the skin by rubber strap
Plate electrodes
What is an original type of electrode that is similar to the plate electrodes but most often is used as a chest electrode
Suction cup electrodes
What was the main difference in the plate electrodes and the suction cup electrodes
The plate electrodes went on the extremities
The suction cup most often went to the patient’s chest
EEG electrodes are much more sensitive than ECG electrodes because of what
Because the typical EEG electrodes are either a needle or a concave disk made of either gold or silver that is held by thick paste that is more conductive than what is used on the ECG
The “backpack” electrodes and the MRI electrodes have which side effect
They are not good for ST monitoring
What is the standard range of width of the clinical electrode used today
1 cm
The first electrometer used in 1887 by Agustus Waller used what
A 20 µ glass capillary tube filled with Mercury and was floating in sulfuric acid
What is a transmembrane action potential
A potential across a cell membrane where voltage is changing over time
Waller’s pet bulldog was named what
Jimmie
True or False: Einthoven’s Galvanometer required the patient to be hooked to electrodes and the hands and extremities to be placed in jars of salt solutions
True
Who in 1928 applied electronic amplification to the signal thus replacing the string galvanometer
Ernestine and Levine
Who in 1924 was credited with recognizing the vast potential importance of the ECG as a diagnostic and investigative tool
Einthoven
True or false, when depolarization occurs of a polarized cell, the cell becomes electronegative on the outside and positive on the inside, thus switching polarity
Tue
The magnitude of the electrical potential of a cell is given by what equation
The Nernst equation
EMF = -60ln {ion (out) / ion (in) }
What is the common baseline starting millivolts for most cells
-70 to -90
Look at the transmembrane potential on page 15
Or if someone can add it in I do not know how
At resting state what ions are in the cytoplasm and what ions are in the extracellular fluid
K is in the cytoplasm
Na is majority outside cell
What phase is depolarization of the cell
Phase 0
During phase 0 what is the movement of ions across the cell membrane
Na inside the cell
What is the net movement of ions across the cell membrane in phase 1
K out
Cl in
What is the net movement of ions across the cell membrane in phase 2
Calcium in
K out
What phase does repolarization take place
Phase 3
During phase 3, What is the net movement of ions across the cell membrane
K out
How many total phases are there in the transmembrane potential
4
What phase is most closely resemble to the resting state
Phase 4
True or false electrical activity always precedes mechanical activity in the heart
True is actually about 150 ms
All heart activity we measure should be what kind of action potential
A biphasic action potential
What theory states that the ECG is a result of temporal and spatial summation Of electrical activity of the heart as seen by electrodes placed external to the depolarizing cells of the myocardium
The interference theory
Some tissue repolarize in the opposite direction of the depolarization,what is the most notable tissue that this occurs in
Ventricular myocardium
What are leaky cells?
And where are the leaky cells?
Leaky cells are cells that do not maintain polarity and are also known as the pacemakers.
They are located in the SA node and the AV node
List the order of depolarization as it hits each of the myocardial cells
SA node Atrial muscle AV node Common bundle Bundle branches Purkinje fiber Ventricular muscle
What is known as the hoot owl theory
The dipole theory
What is the ECG measured in
mV
True or false: the farther away from the heart you go, the greater the voltage amplitude you will get
False
True or false electrical activity spreads across the heart via a defined anatomical pathway
True
What is another name for potential lines when the potential is the same everywhere on that line
Equipotential lines
True or false: current and potential lines exist in the limbs and extremities
False they do not exist in the limbs they only move in limbs through cable conduction
What are the surface potentials at any given moment in time in relation to the front and back
There is no symmetry from front to back in in surface potential
As far as myocardial electrical activity is concerned, vector length is equal to what
Length is the magnitude of the gradient
The higher the magnitude the longer the vector
The Lower the magnitude the shorter the vector
Vector direction indicates what
The anatomical pathway of the electrical activity
