Cardiopulmonary Flashcards
Cardiac Output/Blood Flow Equation
HR x Stroke Volume
What type of blood is found in fetal circulation?
Mixed Blood (both oxygenated and deoxygenated)
Fetal Circulation Anatomy
1) Ductus Venosus: shunts oxygenated blood from liver to inferior vena cava
2) Foramen Ovale: mixed blood travels from right to left atrium
3) Ductus Arteriosus: mixed blood shunted from pulmonary artery to aorta to send out to body
4) Umbilical Arteries: bring oxygenated blood back to placenta
Cardiac Muscle Anatomy/Physiology
1) Intercalated discs (increase closeness of fibers for transmitting excitation quickly)
2) Syncytial (“all or nothing” function, all fibers twitch at same time)
3) Larger T-tubules (propogate action potentials)
4) Calcium induced calcium release ( unique bc K+ drives skeletal muscle)
5) Less work required vs skeletal muscle
6) Twitches generate output
7) Never fatigues or rests
Tissue Layers of Heart (Superficial to Deep)
1) Pericardium (fibrous layer)
2) Myocardium (contractile layer)
3) Endocardium (endothelial layer)
Landmarks for
1) Listening to HR
2) Apex location
1) Listening to HR: second intercostal space
2) Apex location: midclavicular line of 5th intercostal space
Right vs Left Side of Heart
· Left Side: receives oxygenated blood from lungs and pumps to body
· Right Side: Receives deoxygenated blood from body and pumps to lungs
Systemic vs Pulmonary Circulation
· Systemic:
- delivers oxygenated blood to organs and muscles
- returns deoxygenated blood to heart
· Pulmonary:
- delivers deoxygenated blood to lungs
- returns oxygenated blood to heart
Opening and Closing of Valves (passively)
· Open: upstream pressure > downstream
· Close: downstream pressure > upstream
Chordae Tendinae Function
Provide tension for AV Valves (Tricuspid and Mitral) to prevent prolapse
Clinical Relevance of Heart Valve Sounds
·S1 (Lub): End of Diastole/ventricular filling
- Tricuspid and Mitral Valves close
·S2 (Dub): End of blood ejection
- Pulmonary and Aortic Valves close
Cardiac Cycle Events
1) AV Valves Open (Diastole)
- ventricles fill
2) AV Valces Close (Systole)
- Isovolumetric Ventricular Contraction (all valves close)
3) Semilunar Valves Open (Systole)
- ventricular ejection
4) Semilunar Valves Close (Diastole)
- Isovolumetric Ventricular Relaxation (all valves closed)
Cardiac Performance Factors
1) Volume
2) Pressure
3) Flow
Starling’s Law/ Length- Tension Relationship
↑ Volume (Preload/EDV) then ↑ Stretch
Contractility
· Intrinsic property of cardiac muscle and therefor NOT effected by volume or pressure
· Does effect preload/EDV
· Can change based on preload and what is needed to reach a certain SV
- ex: If contractility is ↓ then preload must be ↑ to achieve a certain SV
* Usually assumed as a constant measure but realistically functions to help balance what is needed
Hydrostatic Pressure
Change in Pressure relative to gravity
Transmural Pressure
· Difference in pressure between the inside and outside of a vessel
· Pressure must be greater inside > outside or else vessel would collapse
Type of relationship between cross-sectional area and velocity?
· Inverse relationship
· Ex: If ↑ CSA then ↓ Velocity (in capillaries)
Relationship between Flow and Driving Pressure, Radius, Viscosity, and Length
· Flow is directly proportional to driving pressure and radius but inversely proportional to viscosity and length
· Ex: ↑ Flow :
- ↑ Driving Pressure
- ↑ Radius
- ↓ Viscosity
- ↓ Length
Is pressure greater in systemic or pulmonary circulation?
· Systemic (left side of heart) > Pulmonary (right side of heart)
Relationship between Resistance to Blood Flow and Radius
· Resistance is directly proportional to viscosity and length but inversely proportional to (fourth power) radius
· Ex: ↑ Resistance :
- ↑ Viscosity
- ↑ Length
- ↓ radius ^4
·
STEMI vs. NSTEMI
1) STEMI (ST Elevation Myocardial Infarction): transmural, full thickness ischemia
* Myocardial injury more severe usually
2) Non-ST Elevation Myocardial Infarction: subendocardial, partial ischemia
What can happen during the super-normal refractory period?
Another impulse can cause ventricles to depolarize again
What happens if QT Interval is greater than half the R-R Interval?
Another Heartbeat can happen before ventricles have repolarized which can lead to lethal arrhythmias
What part of the EKG would reflect damage to the atria conduction system?
P-wave
What dysfunction would a widened QRS complx represent?
His-Purkinje network
Normal Capillary Pressure Factors
Maintained when pre-capillary resistance> post-capillary resistance
How do you increase capillary pressure?
Decrease pre-capillary resistance which leads to more flow and thus an increase in pressure
· What happens to pre-capillary resistance during Arteriole Dilation (or venular constriciton)
· Arteriole Constriction?
· Arteriole Dilation: ↓ Pre-capillary Resistance
· Arteriole Constriction: ↑ pre-capillary resistance thus decreasing flow and decreasing pressure in the capillary
Distensibility
Describes the change in volume for a given change in pressure
Convection
· Capillary exchange of water
· Dependent upon the balance of pressures between capillary and interstitial
Cardiac Action Potentials
· Na+ Current: rapid depolarization
· Ca2+: triggers cardiac contraction
· K+ Current: repolarization
Nitroglycerin (Cardiac Medication)
· Powerful vasodialator that decreases afterload thus decreasing the work of the heart
How do pacemakers decrease heart rate? (3 ways)
1) Decrease rate of depolarization
2) Shift maximum daistolic potential to start out more negative
3) Increase threshold (thus more time required to reach a positive threshold)
Inotropic Agents (Cardiac Medications)
· Modify contractility independent of pre/afterload and by raising/lowering Ca+ levels
· Positive Inotropic Agent: ↑ contractility and work of the heart by ↑ Ca+
· Negative Inotropic Agent: ↓ contractility and work of the heart by ↓ Ca+
Where does gas exchange occur?
· Blood-air barrier (due to vessels lining the alveoli)
· Type 1 Cells
· Lung parenchyma
Visceral vs Parietal Pleura and Plueral Space
· Visceral Pleura: covers surface of lung and is inseperable from lung tissue
· Parietal Pleura: covers inner surface of chest wall and exposed part of diapragm
· Pleural Space: thin serous film that separates the 2 pleura and has an airtight seal to enhance lung expansion
Bohr’s Method
· Expired CO2 comes from alveolar gas not dead space
· Ex: Increase dead space means decreased expired CO2
How to decrease pulmonary vascular resistance (PVR)
· 2 Methods
1) Recruitment- opening of previously closed vessels
2) Distention- increase in the caliber of vessels that were already open
Alveolar Hypoxia
· Constriction of small pulmonary arteries as a way to direct blood flow away from poorly ventilated areas of the lungs
Hypoxemia
Drop in partial pressure of O2 in arterial blood
What can change ventilation or perfusion?
1) Intrapulmonary Shunt- no ventilation occurs
2) Alveolar Dead Space- no perfusion occurs
Respiratory Alkalosis
· Result of Hyperventilation causing a decrease in CO2 and thus an increase in pH
Compliance
· Ability to generate a certain volume at a certain pressure
Hysteresis
· Amount of pressure generated for a given volume
· At a given pressure, volume during expiration > inspiration
What does surfactant affect?
· Reduces Surface tension to equalize pressure
· Produced by Type 2 Pneumocytes
· Decreased surfactannt can lead to difficulty inflating the lungs and potential of atelectasis (alveolar collapse)
Regulated variables in breathing?
Arterial blood gases (O2 and CO2) and pH
What has a greater influence of changing breathing- CO2 or O2?
CO2> O2
Obstructive vs Restrictive Patterns
1) Obstructive: decrease in expiratory airflow
- decreased elastic recoil results in air trapping in lungs
2) Restrictive: decrease in lung volume
COPD Characteristics and 2 Main Types
Characteristics
· ↓ elasticity
· ↑ airway resistance
· Air trapping
2 Main Types:
1) Chronic Bronchitis
2) Emphysema
Atherosclerosis
· Progressive hardening and narrowing of the arteries, occurs within the arterial walls
* Cause of most heart and vascular diesases
Orthostatic Hypotension Diagnostic Requirements
· Drop in SBP >20 mm Hg
· Drop in DBP >10 mm Hg
· Increase in HR > 15bpm
Composition of Whole Blood
· Plasma (liquid) (47-64%)
· Red Blood Cells (formed elements)
· WBCs and platelets (buffy coat)
Hemoglobin vs Hemotocrit
· Hemoglobin: O2 carrying protein
· Hemotocrit: % of whole blood that is composed of RBCs
Thrombocytopenia vs Thrombocytosis
· Thrombocytopenia: decrease in platelet count below 70,000
- increased risk for bruising
· Thrombocytosis: increase in platelet count
- due to hemostasis problem
Erythrocyte Function
1) Carry O2 to tissues
2) Carry CO2 to lungs
3) Buffer to maintain pH balance
* Key factor is Hb
Oxygen Saturation
· Amount of Hb actually bound to O2
· Females: ~ 14.0 g/dL
· Males: ~ 15.5g/dL
Screening for a DVT (Wells Clinical Decision Rules:DVT)
· Scored based on clinical liklihood of a DVT
· Score of 0 or less = DVT unlikely
· Score of 3+ = DVT highly likely
Normal Hb Ranges, Hematocrit, pH, PaCO2, PaO2
· Male: 14-18 g/dL
· Female: 12-16 g/dL
Hematocrit:
· Males: 42-52%
· Females: 37-47%
pH:
· 7.35-7.45
PaCO2:
· 35-45 mm Hg
PaO2:
· 80-100 mg Hg
