Cardiorespiratory Physiology Flashcards by Julie Ng

Tidal volume

1) Definition
2) Normal value

1) volume of normal inspiration and expiration
2) 7ml/kg

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Minute ventilation

1) Definition
2) Normal value

1) volume of air inspired in 1 minute
2) Tidal volume x RR

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Physiological dead space

1) Definition
2) Normal value

1) Total volume of gas not involved in gas exchange
2) Anatomical dead space + alveolar dead space

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Anatomical dead space

1) Definition
2) Normal value

1) Volume of conducting airways not involved in gast exchange
2) 150ml

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Lung compliance

Unit change in lung volume per unit change in pressure

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Factors that lead to increase lung compliance

Emphysema

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Factors leading to decrease lung compliance

Age
Supine
Increase ACS
Restrictive lung disease
Hydro/pneumothorax

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Central chemoreceptors

1) location
2) mechanism

1) ventral surface of medulla
2) increase PaCO2 -> decrease pH of CSF -> increase ventilation

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Peripheral chemoreceptors

1) location
2) mechanism

1) carotid body
2) stimulated to increaes ventilation when decrease PaO2/pH/increase PacO2

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Oxygen Hb dissociation curve

1) x-axis
2) y-axis
3) Shape and why

1) Oxygen tension (PO2, mmHg)
2) Oxyhemoglobin (% saturation)
3) sigmoid, positive cooperativity of Hb

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What shifts oxygen Hb dissociation curve to left?

increase pH
decrease temp
decrease DPG

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What shifts oxygen Hb dissociation curve to the right?

decrease pH
increase temp
increase DPG

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In pulse oximetry, absorption wavelength of

1) deoxyHb
2) oxyHb

1) 660nm
2) 940nm

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Beer’s law

the concentration of a given solute in a solvent is determined by the amount of light that is absorbed by the solute at a specific wavelength

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Lambert’s law

equal parts in the same absorbing medium absorb equal fractions of the light that enters them.

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How is oxygen saturation calculated via pulse oximetry

Ratio of max/min absorption of infrared and red light

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False readings

bilirubin (low)
carboxyHb (high)
MetHb (static 85%)
Nail varnish
Flickering light
Diathermy
Patient movement

Name the phases of the cardiac cycle

Phase 1: Isovolumetric relaxation
Phase 2: Inflow
Phase 3: Isovolumetric contraction
Phase 4: Ejection

Equation for Cardiac Output

CO = Stroke Volume x Heart Rate

Starling’s Law

Force of contraction is proportional to initial length of muscle fibers

What factors does stroke volume depend on?

Preload
Afterload
Contractility

What is cardiac index?

Cardiac Output / Body surface area

2.2-2.5 L/min/m2

Describe the important features of arterial waveform

Anacrotic and dicrotic limb
Systolic uptake
Peak systolic pressure
Dicrotic notch
Pulse pressure
MAP (area under curve)

Draw the arterial waveform

How is arterial pressure different from the aortic root?

SBP is 10mmHg higher DBP is 10mmHg lower MAP is 5 mmHg lower

Pulsus paradoxus

exaggerated (\>10 mmHg) reduction of the arterial pressure brought on by inspiration, and may be seen in **cardiac tamponade**

Pulsus alternans

random variation in the amplitude of the arterial pressure tracing with each cardiac cycle, and is seen with left ventricular failure / **congestive heart failure**

Draw the CVP waveform

Explain the components of the CVP waveform

* a : atrial contraction * c: upward movement of tricuspid valve in isovolumetric contraction * x: atrial relaxation and downward movement of tricuspid * v: venous return filling atrium * y: ventricular filling in early diastole

Causes of widening pulse pressure

Aortic regurgitation

Causes of narrowing pulse pressure

* Low output states: * Cardiac tamponade * Massive PE * Severe cardiogenic shock * Tension pneumothorax

Kussmaul sign

Paradoxical rise in JVP during inspiration, indicates right heart failure or constrictive pericarditis

Fick's principle

Total uptake or release of any substance by an organ is the product of blood flow to the organ and the arteriovenous concentration difference of that substance (aka. oxygen used =oxygen in - oxygen out) Used to measure cardiac output

Equation for cardiac output based on Fick's principle

CO = Oxygen consumption / ([O2]pulmonary vein - [O2] pulmonary artery)

Types of BP monitoring

* Non-invasive * Sphygmomanometer * Invasive * A-line

Types of cardiac output monitoring

* Non-invasive * LidCo * PiCCo * Thoracic impedance techniques * Echocardiography * Invasive * Swan-Ganz catheter * Transesophageal echocardiography

Types of narrow complex tachcyardia

* Regular * Sinus tachycardia * pSVT * Irregular * Atrial fibrillation * Atrial flutter

Types of broad complex tachycardia

* Ventricular tachycardia * Ventricular fibrillation * SVT with abberant conduction * PVC

Management of SVT

* ABC * Vagal maneuver, if. fail * Push IV 10mg ATP, if fail * Push IV 20mg ATP * Check BP, if normal * IV Verapamil 5-10mg over 2 min * If BP low or adverse signs (chest pain, HF, altered mental status) * Synchronized DC cardioversion (start at 50 J, with 50J increments)

Management of bradycardia

* ABC * Secure airway, IV lines * Give O2 * Close monitoring * ECG * Portal CXR * Bloods x electrolytes * If stable: atropine 0.5-1mg + transcutaneous pacing * If unstable: Transcutaneous pacing

Types of bradycardia

* Sinus * Sinus bradycardia * Sinoatrial block * Sinus arrest * AV block * 1st degree: prolonged PR * 2nd * type 1: gradual failure * type 2: intermittent failure * 3rd: complete heart block