Flashcards in Lec 26 Congenital Heart DIsease Flow Dynamics Deck (15)

Loading flashcards...

1

## What determines the driving force for systemic flow? what about the pulmonary circulation?

###
systemic = pressure difference between aorta and central venous pressure pushing blood through the heart

pulmonary = pressure difference between pulm artery and LA

2

## What is Ohm's law for flow?

###
delta P = Q * R

pressure drop = mean flow * mean resistance

3

## Why do we measure average rather than instantaneous flow?

###
- easier to conceptualize and measure

limitation: instantaneous behavior of circulation can be obfuscated by these models

4

## What is the equation for systemic resistance?

###
Rs = (Pao - Pra) / CI

[R = delta P/flow]

Rs = systemic resistance

Pao = aortic P

Pra = right atrium P

CI = cardiac index

5

## What is cardiac index?

### CI = cardiac output indexed to body surface area

6

## What happens to PVR after birth?

###
starts out really high and declines to adult level

means there is a rapid decline in pulm/systemic resistance ratio

7

## What is normal mature level of PVR [pulm ascular resistance]?

### 2 woods units

8

## What 3 factors alter resistance to blood flow?

###
1. blood viscosity

2.. vessel length

3. vessel radius [most important]

9

## What determines blood viscosity?

### - high hematocrit [Hct] and protein conc --> high viscosity --> increase resistance

10

## What is poiseulle's equation?

### R = 8 * Ln/pi*r^4

11

## What is relationship relative flow through parallel outlets from single reservoir?

### relative flow rate proportional to relative resistances

12

## What happens to resistance when resistors are added in parallel?

### resistance lowered!

13

## What do we assume if non-restrictive "large" VSD when we are calculations flows/pressures?

### - systolic RV and LV pressures equalize thus aortic and pulmonary artery pressure equal in systole

14

## How do you determine Qp/Qs the pulmonary to systemic flow ratio?

###
Qp/Qs is inversely proportional to resistance ratio Rp/Rs

--> the ratio of resistances determines the amount of shunting through VSD

15