04 Pulmonary Circulation

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• lower p: doesn't need to go as far

Blood O2 Content

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• fetal: less blood to lungs, not important in womb

Diffusion

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• more pressure difference of O2 in air/blood: more diffusion

• more area: more diffusion

• thickness: less diffusion

• emphysema: alveoli destroyed, low DLCO

• fibrosis: thicker, low DLCO

• diffusion of CO same as DLCO

Diffusion-Perfusion

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• infuse 3 gases into lungs at Pa concentration, ideally reach Pa concentration

• N2O: at length 0, no N2O diffuse into blood; diffusion rises very rapidly along capillary length to max value

• CO: rises slowly, never gets to maximum concentration

• O2: some O2 from veins at length 0, rise relatively rapidly until max value

• gas must diffuse through and get carried away

• N2O: barrier not a factor

• N2O rapidly diffuse through

• only determination for rate of rise of N2O is how fast blood flowing, carrying away molecules, rapid rise in partial pressure

• barrier is major factor for diffusion

• slow rise

• diffusion main factor. Perfusion not a factor

• N2O: only thing slow or speeds up concentration is blood flow rate

• O2: same

• CO: uptake limited by diffusion

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• diffusion limited

• concentration of O2 in blood falls = hypoxemic

• at rest: blood flows slowly, lots of time to pick up O2

• exercise: blood flow faster, gets further before reach maximum, but still does even in patients exercising

• exercise alone should not make someone hypoxemic

Pulmonary Resistance

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• alveolar: blood supplying alveolus

• arteriolar: blood supplying lung parts outside alveoli

• inhale: increase resistance from alveolar vessels

• exhale: increase resistance from arteriolar vessels

• FRC: lowest point of pulmonary vascular resistance

Pulmonary Hypertension

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• right heart cath: cath into PA from heart

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• V: energy needed to drive flow

• I: how fast you want to go

• R: resistance to flow

• Ppa high in pulmonary hypertension, if any of the variables increased

• high CO: increase flow through lungs

• most common cause of PHTN nothing to do with lungs but with left heart

• chronic hypoxia vasoconstrict

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• Epoprostenol: IV, must infuse constantly, cumbersome