Cardiopulm 14 - Ventilation/perfusion

1

100

T/F: The lungs you are laying on are getting the most perfusion 

True 

200

- Oxygen tension in the arterial blood reflects adequacy of ventilation and perfusion matching (V/Q) in the lungs
- Overall V/Q average = 4L/min/ 5L/min = 0.8
- Arterial blood blood oxygenation is measured by blood draw (usually using radial artery) and called arterial blood gas (ABG test)
   - Checks (in mmHg) PaO2 and PaCO2 as well as pH
   - Calculates bicarbonate (HCO3)
   - Can measure electrolytes and standard CBC blood tests as well 

Principles of ventilation/perfusion 

300

- Ventilation and perfusion are gravity dependent
- Increased V and Q both at:
   - Bases vs apices (standing upright)
   - Lung down (ipsilateral) vs. lung up (sidelying)
        - As well as lowest most lateral segments (each lung) in sidelye
   - Posterior vs. anterior most segments (supine)
   - Anterior vs. posterior most segments (prone) 

Rule #1

400

Which zone of ventilation: 

4L/minute
Reason: intermittent size of alveoli 

Zone 2 

500

Which zone of perfusion: 

Perfusion is constant 

Zone 3 

2

100

Peripheral O2 = SpO2 = % = 

Hypoxic 

200

- Ventilation and perfusion both increase independently from the apex to base of the lungs
   - Zone 1: top ; least amount of air
   - Zone 2: middle
   - Zone 3: Bottom ; most amount of air; perfusing the most 

Rule #3

300

- Ventilation and perfusion are not equally distributed
- For example, in upright sitting or standing position:
   - Ventilation (air) at bases is about 2.5x greater than at apices BUT
   - Perfusion (blood) at bases is 6x greater than at apices 

Rule #2 

400

Which zone of perfusion:

Perfusion is absent  

Zone 1

500

T/F: V/Q ratio increases from apex to base (in upright lung) 

False... V/Q decreases from apex to base 

3

100

Decreased O2 in the blood 

Hypoxemic (in the blood gas) 

200

T/F: Perfusion increases disproportionately to ventilation, apex to base 

True 

300

Which zone of ventilation:

1.92L/minute
Reason: increase size of alveoli 

Zone 1

400

Which zone of ventilation: 

6/5L.minute
Reason: decrease size of alveoli 

Zone 3 

500

Which zone of perfusion: 

Perfusion is sporadic 

Zone 2 

4

100

V=Q
Ratio is 1
Ideal zone due to pulmonary vasculature at level of heart for optimal perfusion and ventilation both 

Zone II (mid lungs) 

200

V < Q
Ratio is < 1
V is high, but Q is very high (because of gravitational pressure), so V < Q
Hypoxemic; hypo ventilatory 

Zone III (bases) 

300

V>Q
Ratio is > 1
V is low, but Q is almost non-existent, so V > Q
Hyperventilation  

Zone 1 (apices) 

400

Zone II is at which % of V/Q ratio? 

100% *** 

500

Ideally, we would like to reside in equal amount of V and Q but gravity wins and average healthy person stays about ____

0.8 *** (zone III) 

5

100

- Head/neck tilt (extension vs. flexion)
- Facilitators voice/command
- Ambiance and lighting of room 

Other considerations to help facilitate ventilation 

200

1. Hgb Affinity
2. Oxyhemoglobin dissociation curve
3. Intrapleural pressure
   - Pressure outside lung/within pleural cavity
   - Highest at base
4. Intrapulmonary pressure
   - Pressure within ling/in alveoli
   - Highest at base
5. Atmospheric pressure vs. PA and PP to influence ventilation 

Additional rules (ventilation also depends on..) 

300

Extension, eyes up and moving out of/against gravity is which breathing movement 

Inhalation 

400

Pulmonary vascular resistance (constriction/dilation)
Ejection timing (cardiac output)

The position of optimal physiological function:
- Upright
- Moving/staying active 

Perfusion is also influenced by: 

500

Flexion, eccentric or concentric contraction, eyes down and coming back into/towards gravity is which type of breathing movement 

Exhalation