Practicals Flashcards
What does the P wave signify?
Atrial depolarization
What does the PR interval signifiy?
AV nodal delay
What does the QRS complex signify?
Ventricular depolarization
(simultaneous atria repolarization)
What does the ST segment signify?
Ventricles contracting and emptying
What does the T wave signify?
Ventricular repolarization
What does the QT interval signify?
Ventricular depolarization and repolarization
What does the TP interval signify?
Ventricle relaxing and filling
How to calculate HR from ECG tracing?
100 / number of big squares in an RR interval
Each small square = 0.04sec
60 / (0.04seconds * small squares) = bpm
Describe the BIPOLAR limb leads degrees and ECG signals
Lead I = left to right arm (0)
Lead II = left arm to ankle (60)
Lead III = right arm to ankle (120)
All positive deflections
Lead II has the largest positive spike
Describe the UNIPOLAR limb leads degrees and ECG signals ***
aVL = BIPHASIC or ISOMETRIC line 30
aVF = Positive 90
aVR = Negative 150
The reference point is the heart
So think about the direction depolarization occurs
Right foot is grounding electrode = doesn’t measure anything
What is the normal range of QRS axis?
-30 to +90 degrees
What can QRS axis deviation diagnose?
Right Axis Deviation (RAD) occurs when the QRS axis is more than +90° or toward the right side of the heart. This deviation can be seen in conditions where the right side of the heart is working harder, causing it to become enlarged or overactive.
Left Axis Deviation (LAD) happens when the QRS axis shifts to less than -30°. This indicates that the electrical activity is moving more toward the left side of the heart.
LAD suggests that the left ventricle is under strain or there is a blockage in the conduction system, changing the direction of electrical impulses
What are causes of right axis deviation?
RV hypertrophy
Chronic lung disease
Pulmonary embolism (blockage)
What are causes of left axis deviation?
LV hypertrophy
Conduction abnormalities
Inferior myocardial infarction
What two leads express a QRS that is 0 degrees and +90 degrees?
Lead I = 0 degrees (moving RIGHT)
aVF = +90 degrees (moving DOWN)
What heart conditions can we see in ECG?
Atrial Premature Beat
Tachycardia
Ventricualr fibrilliaton
Myocardial infarction (STEMI)
Where is V1 chest lead placed?
4th intercostal space on the right side of the sternum
Where is V2 chest lead placed?
4th intercostal space on the left side of sternum
Where is V3 chest lead placed?
Between V2 & V4
Where is V4 chest lead placed?
Mid-clavicular 5th intercostal space
Where is V5 chest lead placed?
Anterior axillary 5th intercostal space
Where is V6 chest lead placed?
Mid-axillary 5th intercostal space
To measure blood pressure, what arteries do we look at?
Brachial artery
Radial artery
What sounds are we listening for?
Korotkoff sounds
When will and won’t we hear Korotkoff sounds?
When artery is fully compressed and there is no blood flow = no sound
Compressed artery to increase velocity of blood = creates vibrations heard as Korotkoff sounds
Flow is uncompressed = no sound
So when do we take note of blodo pressure?
When you first hear Korotkoff sounds = systolic bp
When Kototkoff sounds stop = diasolic bp
How do we estimate systolic pressure?
Inflate cuff until radial pulse disappears
How do we measure blood pressure manually?
Place stethoscope over brachial artery
Inflate cuff to 10-20 mmHg above ESTIMATED systolic bp
Slowly deflate cuff
Listen for Krortkoff sound = systolic bp
Listen until sound disappears = diastolic bp
What happens to bp when we stand from lying down?
What is direct calorimetry?
Measuring energy expenditure by capturing heat produced by the body in calories
What is heat?
Byproduct of metabolic processes
60% of energy from glucose/fat metabolism
What is indirect calorimetry?
Estimates energy expenditure by measuring RER
RER = respiratory exchange ratio
What does RER stand for?
respiratory exchange ratio
How is RER measured?
Volume of O2 consumed (VO2)
Volume of CO2 produced (VCO2)
What are some application of indirect calorimetry?
Estimate energy expenditure
Evaluate substrate utilization
Assess aerobic fitness
Clinical applications
How are VO2 and VCO2 measured?
What is the equation?
VO2 = (fraction of inspired O2 x INSPIRED volume) - (fraction of expired oxygen x EXPIRED volume)
Same for VCO2
How is fraction of INSPIRED O2 measured?
20.93% ~ 21% at sea level
How is fraction of EXPIRED O2/CO2 measured?
Measured by gas analyzer
How is inspired volume of O2/CO2 measured?
Assumed equal to EXPIRED air
How is expired volume of O2/CO2 measured?
Measure by flow meter
Describe the different substrates
Fatty acids = almost unlimited but slower source of energy
Carbohydrate = relatively limited by more efficient source of energy
What happens to substrate utilization as exercise intensity increases and why?
Swaps from using fats more to using carbohydrates more
Carbs = more EFFICIENT source of energy
5.05 kcal/L of oxygen
How to calculate RER and what it tells us
VCO2 / O2
If RER is nearer 0.7 = fatty acids
If RER is nearer 1 = carbohydrates
How do we calculate energy expenditure per min?
Energy correlated to RER x VCO2 = how many kcal expended in 1minute
Why do we need to calibrate the indirect calorimetry tools?
Because need to correlate it to SEA LEVEL and TEMPERATURE in the room
