Cardiovascular and Respiratory Physiology

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Cardiovascular and Respiratory Physiology

• By Amy Wolthoff

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Auscultation of the Heart (245)
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Cardiac Output (245)
During exercise 1. Inc SV inc CO 2.
Inc HR inc CO If HR is too high
incomplete diastolic filling dec
CO ex. V-tach
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Cardiac Output Variables (246)

• Stroke Volume is increased by
• Contractility and Preload
• Afterload
• Anxiety (inc sympathetics)
• Exercise (inc preload)
• Pregnancy (inc blood
• volume inc preload)

Myocardial O2 demand increased by Afterload
(arterial pressure) Contractility Heart
Rate Heart size (increased wall tension)
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Preload and Afterload (246)
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Starling Curve (246)

• As preload increases (amount of blood brought
  back to the heart and allowed to fill the
  ventricles in diastole) cardiac output will
  increase UNLESS the myocardium is unable to
  support the load (either disease or
  iatrogenically)

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Ejection Fraction (246)

• The volume of blood that is pumped out to the
  body proportional to the amount of blood that was
  brought back to the heart
• Measure of contractility
• Normal gt 55, so at least 55 of blood that is
  in the heart at the time of systole should be put
  out into circulation

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Resistance, Pressure, Flow (247)

• Flow goes from high pressure to low pressure
• Resistance
• Directly prop to viscosity
• Indirectly prop to radius4
• Arterials account for the most of
• TPR therefore they regulate
• capillary flow

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Cardiac and vascular function curves (247)
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Cardiac Cycle (247)
2. Systolic ejection
1. Isovolumetric contraction
3. Isovolumetric relaxation
4. Rapid filling
5. Reduced filling
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Cardiac Cycle (247)

• Heart sounds
• S1 mitral and tricuspid closure.
• Loudest at mitral area
• S2 aortic and pulmonary valve closure.
• Loudest at left sternal border
• S3 In early diastole during rapid ventricular
  filling phase
• Associated inc filling pressures and more
  common in dilated ventricles (normal in children)
• S4 (atrial kick) in late diastole
• High atrial pressure
• Associated with ventricular hypertrophy
• Left atrium must push against stiff LV wall

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Cardiac Cycle (247)
Jugular venous pulse (JVP) A wave atrial
contraction C wave RV contraction (tricuspid
valve bulging into atrium) V wave inc atrial
pressure due to filling against closed tricuspid
valve
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Splitting (248)

• Normal splitting
• Inspiration leads to drop in intrathoracic
  pressure which inc
• capacity in pulm circulation
• pulmonic valve closes later to accommodate more
  blood entering lungs
• aortic valve closes earlier because of
  decreased return to the L heart
• Wide splitting
• Anything that delays RV emptying
• (pumonic stenosis, RBBB)
• Delayed pulmonic sounds regardless
• of breath
• Exaggeration of normal splitting
• Fixed splitting
• ASD leads to L to R shunt and therefore
• inc flow through pulmonic valve regardless
  
• of breath
• Pulmonic closure is greatly delayed
• Paradoxical splitting
• Anything that delays LV emptying
• (Aortic stenosis, LBBB)

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Heart Murmurs (250)

• Holosystolic, high-pitched blowing murmur.
• Mitral apex, radiates to axilla
• Ischemic HD, MVP, LV dilation, RF
• Tricuspid radiates to R sternal border
• RV dilation, endocarditis, RF

• Crescendo-decrescendo systolic ejection murmur
  
• followed by ejection click
• LV gtgt aortic pressure during systole
• Radiates to carotids
• Pulsus parvus et tardus pulse weak compared
  to heart sounds (syncope)
• Age related calcific aortic stenosis

• Holosystolic, harsh sounding murmur, loudest at
  tricuspid area

• Late systolic murmur with midsystolic click
• Most frequent valvular lesion
• Loudest at S2
• Usually benign
• Can predispose to infective endocarditis

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Heart Murmurs (250)

• Immediate high-pitched blowing diastolic murmur
• Wide pulse pressure when chronic
• Often due to aortic root dilation, bicuspid
  aortic valve or rheumatic fever

• Follows opening snap
• Delayed rumbling late diastolic murmur
• LAgtgtLV pressure during diastole
• Often occurs 2/2 rheumatic fever

• Continuous machine like murmur
• Loudest at the time of S2

Right sided defect Inc intensity on inspiration
because more blood flows into RA Left sided
defect Inc intensity on expiration because more
blood flows into LA
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Cardiac Myocyte Physiology (251)

• Cardiac muscle contraction needs extracellular
  calcium
• Ca enters cell during action potential which
  stimulates Ca release from
• sarcoplasmic reticulum
• Calcium induced calcium release

• Different than skeletal muscle because
• Cardiac muscle AP has a plateau due to Ca influx
• Cardiac nodal cells spontaneously depolarize
  which leads to automaticity due to If channels
• Cardiac myocytes are electrically coupled to each
  other by gap junctions

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Ventricular Action Potential (251)
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Pacemaker Action Potential (252)

• Occurs in the SA and AV nodes
• Differences from ventricular AP
• Phase 0 upstroke-opening of voltage gated Ca ch
  (they lack fast voltage gated Na ch), this
  results in slow conduction velocity used by AV
  node to prolong transmission from atria to
  ventricles
• Phase 2 plateau is absent
• Phase 3 inactivation of Ca ch and inc activation
  of K ch leads to inc in K efflux
• Phase 4 slow diastolic depolarization- membrane
  potential spontaneously depolzarizes as Na
  conductance increases
• If is different from INa above
• This accounts for automaticity of SA and AV nodes
• The slope of phase 4 determines heart rate
• Ach dec the rate of diastolic depolarization and
  dec HR
• Catecholamines inc depolarization and inc HR
• Sympathetic stimulation inc the chance that If
  channels are open

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Electrocardiogram (253)
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Torsades de pointes (253)

• Ventricular tachycardia
• shifting sinusoidal waveforms on EKG
• can lead to ventricular fibrillation
• anything that prolongs the QT interval can
  predispose

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Wolff Parkinson White Syndrome (253)

• Accessory conduction pathway from atria to
  ventricle (bundle of Kent) bypassing AV node
• Ventricles begin to partially depolarize
  earlier, giving rise to characteristic delta wave
  on EKG
• May result in re-entry circuit leading to
  supraventricular tachycardia
• AKA ventricular pre-excitation syndrome

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EKG Tracings (254)

• Atrial Fibrillation
• Chaotic and erratic baseline
• (irregularly irregular) with
• no discrete P waves in
• between irregularly spaced
• QRS complexes
• Can result in atrial stasis and
• lead to stroke
• Treat with warfarin
• (Coumadin)

• Atrial Flutter
• Rapid succession of identical back to back
  atrial depolarization waves
• Sawtooth appearance of the flutter waves
• Attempt to convert to sinus rhythm
• Use Class IA, IC or III anti-arrhythmics

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EKG Tracings (254)

• AV block
• 1st Degree
• Only abnormality is prolonged PR
• interval!! (gt200msec)
• Asymptomatic

• 2nd Degree
• Mobitz Type I Wenckbach
• Progressive lengthening of PR interval
• until a beat is dropped (a P-wave not
• followed by a QRS complex)
• Usually asymptomatic
• Mobitz Type II
• Dropped beats that are not preceded by a
• change in the length of the PR interval
• Abrupt nonconducted P waves result in
• pathologic condition
• Often found as 21 block, where there are
• 2 Ps to every 1 QRS
• May progress to 3rd degree block

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EKG Tracings (255)

• 3rd degree (complete)
• Atria and ventricles beat independently of each
  other
• Both p waves and QRS complexes are present
• P waves bear NO relation to the QRS complex
• Atrial rate faster than ventricular rate
• Treat with pacemaker
• Lyme disease can result in this

• Ventricular Fibrillation
• Complete erratic rhythm with
• no identifiable waves
• Fatal arrythmia without
• immediate CPR and
• defibrillation

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Maintenance of Mean Arterial Pressure- MAP (256)

• ANP released from atria in response to inc blood
  volume and atrial pressure
• causes generalized vascular relaxation
• constricts efferent renal arterioles, dilates
  afferent arterioles

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Baroreceptors and chemorecptors (256)
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Circulation through organs (256)
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Normal Pressures (257)

• Pumonary capillary wedge pressure (PCWP) left
  atrial pressure
• In mitral stenosis, PCWP gtgt LV diastolic
  pressure
• Measured with Swan-Ganz catheter

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Autoregulation (257)
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Capillary Fluid Exchange (257)
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Important Lung Products (476)

• AKA dipalmiotyl phosphatidylcholine (lecithin)
• Deficient in RDS
• Collapsing pressure 2 tension/ radius
• Tendency to collapse on expiration as radius
  decreases

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Lung Volumes (476)

• Vital capacity everything but the residual
  volume
• A capacity is a sum of 2 or more volumes

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Determination of physiologic dead space (477)
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Lung and chest wall (477)
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Hemoglobin (477)
Fetal hemoglobin has lower affinity for 2,3 BPG
than adult hemoglobin (HbA) and thus has a higher
affinity for O2 When youre released you do
your job better (carry O2)
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Co2 transport in blood (477)
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Co2 Transport (481)
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Hemoglobin Modifications (478)

• METHemoglobinemia can be treated with METHylene
  blue

• CO has 200x greater affinity than O2 for
  hemoglobin

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Oxygen-Hemoglobin Dissociation Curve (478)

• Fetal Hb higher affinity for Oxygen than adult
  Hb so the curve is shifted left
• Sigmoidal shape due to positive cooperativity
  (Hb can bind 4 O2 molecules and has higher
  affinity for each subsequent oxygen molecule
  bound)

• Shift to the right decreased affinity of Hb for
  O2
• (more O2 unloading to tissues)
• Caused by an increase in all factors (except pH)
• Shift to the left increased affinity of Hb for O2
• (less O2 able to unload to tissues)
• Caused by a decrease in all factors (except pH)

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Pulmonary Circulation (479)
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Pulmonary Hypertension (479)

• A consequence of pulmonary HTN is cor pulmonale
  and subsequent RV failure
• S/S jugular venous distention, edema,
  hepatomegaly
• Diffusion Vgas A/T x Dk (P1 P2)
• A is decreased in emphysema
• T is increased in pulmonary fibrosis

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Pulmonary Vascular Resistance (480)
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Oxygen content of blood (480)
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Alveolar gas equation (480)
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Oxygen Deprivation (480)
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V/Q Mismatch (481)
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Response to high altitude (481)
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Response to exercise (481)