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Week 43 > Pulmonary Circulation > Flashcards

Flashcards in Pulmonary Circulation Deck (58)
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1

what are the 2 sources of blood flow to the lungs?

  • Bronchial Circulation
  • Pulmonary Circulation

2

Bronchial Circulation

  • aka Normal Anatomical Shunt
    • 3-4% of total circulation
  • Supplies conducting airways
  • Unoxygenated blood empties into pulmonary vein- Left Atrium
    • PaO2

3

Pulmonary Artery BP vs Systemic Artery BP

why?

  • Pulmonary Artery:
    • MAP=14
    • BP: 24/9
  • Systemic Artery:
    • MAP: 90
    • BP: 120/80
  • Why?
    • Pulmonary Lower bc PVR is 8-10x less than systemic resistance

4

Pulmonary Vascular Resistance

  • 8-10x less than systemic vascular resistance
  • CO(or flow)=MPAP-LAP/PVR
    • MPAP
      • mean pulmonary arterial pressure
      • SBP+(2*DBP)/3
    • LAP
      • Left atrial pressure
    • PVR
      • pulmonary vascular resistance

5

Measuring Pulmonary BP:

Problems associated

  • Catheter entered peripheral vein to:
    • Right Atrium
      • Tricuspid valve
      • Right ventricle emptying
    • Right Ventricle
      • Pulmonic valve
    • Pulmonary Artery
      • Arterial resistance and compliance
      • Capillary resistance and compliance
    • Pulmonary Artery Wedge
      • Left Heart Valve and emptying

6

Pulmonary Artery wedge

  • Mean pressure: 5-7
  • measures pulmonary venous pressure

7

Regulation of PVR:

  • Passive:
    • Vessel Distention and recruitment (pulmonary vessels compliant)
      • CO
      • Pulmonary Artery pressure
      • Gravity-dependent regions
    • Vessels compression
      • lung volume
      • pressures external to blood vessel
    • Blood Viscosity
  • Active: manipulated with drugs
    • Neural
    • Hormonal
    • Endothelial & Inflammatory mediators

8

Passive Regulation: Distention and Recruitment

  • CO increases and maintains:
    • low PVR
    • Low Pulmonary BP

9

Passive Regulation: Lung volume

  • Lowest total PVR @ lung volumes near FRC
    • easiest blood flow occurs b/w breathes 

10

Zones of Lung

  • Zones are pressure conditions not anatomic regions
  • Pressure conditions made by:
    • gravity effects on blood flow
    • air distribution
  • Normal Lung: No Zone 1
    • Zone 2:
      • intermittent blood flow
      • due to Pa>PA>Pv
    • Zone 3
      • Constant flow
        • Pa>PA>Pv
  • Zone 1 due to:
    • increased alveolar pressure
      • mechanical ventilation
    • Decreased Cardiac Output
      • Shock
    • Both

11

Posture effects on Perfusion zones

  • If patient has zone 1
    • do not want them upright bc heart needs to generate more pressure to pump blood to apex
    • lay down=lung horizontal
      • no zone 1

12

Active Regulation of Blood flow: 

Vasodilators vs Vasoconstrictors

  • Vasoconstrictors
    • Low PAo2
      • hypoxic vasoconstriction
    • High PAco2
    • Sympathetic NE--alpha 1
  • Vasodilators:
    • High PAo2
    • Nitric Oxide
    • Symapthetic:
      • EPI; alpha 2, beta 2 adrenergic

13

Pulmonary Hypertension affect on lungs

  • Can lead to Pulmonary edema and eventually Right Heart Failure
  • causes increased Hydrostatic pressure=Greater net filtration
  • can result in:
    • Interstitium edema
    • Alveolar Filling

14

Causes of Pulmonary Edema

  1. Increased Capillary Hyddrostatic pressure
    1. caused by left heart failure
  2. Decreased capillary colloid osmotic pressure
  3. increased capillary permeability 
    1. lung injury
  4. Decreased interstitial pressure
  5. lymphatic insufficiency 

15

Pulmonary edema formation:

Left Atrial pressure

normal range 

Safety Factor Range 

  • Due to:
    • capillary hydrostatic pressure exceeds Oncotic pressure and lymphatic capacity
  • Normal Range:
    • 0-9 Left atrial pressure
  • Safety Factor: 10-25
    • increased lymph flow with increased fluid filtration
    • decreased interstitial oncotic pressure: increased filtration dilutes proteins in interstitial fluid, assumig capillary endothelium is intact
    • high interstitial compliance, but once capacity is reach-alveolar flooding
    • Sufficient surfactant

16

Airflow

  • Ventilation (V)=Pressure Gradient/Resistance
  • depends on:
    • pressure gradient
      • PA-Pb
    • Resistance

17

Resistance:

  • property of conducting airways
  • R=8nL/r^4
  • Radius
    • main determinant of resistance
    • Increase r=Decrease Resistance
    • same in all paralel generations

18

Factors that affect radius:

  • smooth muscle tone
    • does not surround alveoli
  • Lung volume/interdependence
    • @high lung volumes=stretched=pulls out on airways/alveoli=Bigger radius
  • External Pressures
    • if tube is collapsible, Pex can determine flow
    • Depends on location:
      • Extrathoracic: Pb
        • inspiration
      • Intrathoracic, extrapulmonary=Ppl
        • forced expiration
      • Intrathoracic, intrapulmonary
        • Alveolar pressure
        • Lung elastic recoil
  • Patholog conditions
    • Airway wall inflammation (narrow airway)
    • Mucus 
    • foreign bodies
    • destroy alveoli walls=no interdependence

19

Extrathoracic Airways

  • Upper trachea, larynx, pharynx, nasal cavity
  • surrounded by tissue
  • 50% of respiratory system resistance
  • all air thru one tube-High Velocity of airflow (Turbulence)

20

Large Proximal Airways

  • Bronchi
  • semi-rigid=cartilage
  • smooth muscle controls diameter(radius)
  • High velocity of airflow (turbulence)

21

Small Distal Airways

  • Bronchioles
  • non-rigid (no cartilage)
  • surrounded by alveoli so stretch of lung and alveolar pressure impact diameter (Radius)

22

Patterns of Airflow

  • Laminar Flow
  • Turbulant flow
  • Transitional Flow

23

Laminar Flow

  • Distal to terminal bronchioles
    • respiratory bronchioles
    • Aleolar ducts
    • Alveoli 
  • No turbulence=Sildent Airflow
    • slow velocity
  • R<2000 (Reynolds number)

24

Turbulent Flow

  • Increases resistance
  • requires greater driving pressures and more work
  • R>3000 (reynolds number)
  • Conducting airways
  • MAKE noise

25

Transitional Flow

  • What occurs in the lungs
  • occurs in most airways
  • Branching Increases Turbulence
  • R=2000-3000

26

Reynolds number (R)

  • predicts turbulence:

27

Turbulence

  • Increased by:
    • increased airflow
    • increased individual airway diameter
  • Turbulant flow makes noise
  • Clinically:
    • pt takes deep breathe->Increase airflow and diameter
    • Increase in turbulence
    • Lung sounds easier to heart
    • HELPS detect small airway disease

28

Resistance: Lung Volumes

  • Interdependence:
    • Increase Resistance=Decrease Lung Volume

29

Active Control of Airway diameter

  • Bronchoconstrictors:
    • Parasympathetic stimulations
    • Acetylcholine--->M3
    • Histamine
    • Decreased Pco2 in small airways
  • Bronchodilators
    • Symapthetic stimulation
    • Epinephrine
    • Beta-2 adrenergic agonists
    • Nitric oxide
    • Decreased Po2 in small airways
    • Increased Pco2 in Small airways

Matches V to Q

    •  

30

Atmosphere AIr: partial Pressures of gases

  • N2=78%
  • O2=21%
  • CO2=0.03%