Respiration Lecture 05: Resistance

Question 0

2 types of resistance

Answer 0

elastic and airways resistance

Question 1

Resistance

Answer 1

The opposition to airflow. THE RATIO OF PRESSURE TO FLOW.

R=(P1-P2)/flow rate

Question 2

elastic resistance

Answer 2

resistance due to moving lung tissue and related to the compliance and tendency of lung to collapse when lung volume is increased above FRC

Question 3

Airways resistance

Answer 3

due to the properties of the tubes which oppose the movement of air through them

Question 4

resistance primarily affects

Answer 4

rate of air flow

Question 5

compliance primarily affects

Answer 5

volume

Question 6

How do radius and length of tube affect resistance?

Answer 6

Radius - 1:16 increase or decrease!

Length - 1:1 increase or decrease

Question 7

5 things airway resistance is dependent on:

Answer 7

1) rate of airflow
2) driving pressure
3) diameter of tube
4) length of tube
5) viscosity or density of the gas

Question 8

Poiseuille’s Law

Answer 8

describes airflow. Airflow = [pie(P1-P2)r^4]/[8nl] where n=density and l=length of tube

Question 9

How does total cross sectional area and resistance change as you move from large to small airways in the lung?

Answer 9

A increases, R decreases

Question 10

Path of trachea to alveolar sacs

Answer 10

Trachea–> primary bronchi–>lobar bronchioles (?)–>terminal bronchioles–>respiratory bronchioles–>alveolar ducts–>alveolar sacs

Question 11

when does cartilage disappear from bronchioles?

Answer 11

past the hilus, between lobus bronchus and terminal bronchioles

Question 12

How does resistance change as a fx of volume?

Answer 12

increasing volume decreases resistance (inverse relationship) due to increased surface area

Question 13

alveolar sacs

Answer 13

terminal endpoints of branching respiratory system

Question 14

alveolar ducts

Answer 14

where alveoli bud off bronchioles

Question 15

turbulence effect on R

Answer 15

increases resistance

Question 16

Turbulent vs. laminar flow

Answer 16

turbulent flow - molecules hit side of airways and produces sound and airway resistance and decreased flow. Occurs at branch points.
laminar flow - nice smooth flow of molecules in airway

Question 17

Why is actual inspiratory Ppl more negative and expiratory Ppl more positive than expected in a direct pressure to compliance relationship?

Answer 17

Due to resistance in tubes, muscle has to generate enough force to stretch AND make air go through tubes (as you breathe in you have to generate enough force to produce change in volume that overcomes compliance AND generates neg. PA) THEREFORE, PLEURAL PRESSURE IS RELATED TO BOTH COMPLIANCE AND RESISTANCE

Question 18

resistive pressure

Answer 18

difference b/w the elastic recoil pressure and the total pleural pressure

Question 19

alveolar pressure is ____when there is no airflow

Answer 19

zero

Question 20

Resistance of airway=

Answer 20

change in PA/change in air flow

Question 21

how does increased smooth muscle contraction (i.e asthma) affect R?

Answer 21

increases R

Question 22

If airway resistance increases, how must alveolar pressure change if flow rate remains constant?

Answer 22

PA must become more negative to maintain the same flow rate with increased resistance

Question 23

3 main things effort independent flow limitation is due to

Answer 23

resistance, compliance, and expiratory driving pressure

Question 24

effort independent flow limitation

Answer 24

linear area on air flow rate vs. % vital capacity where flow rate decreases linearly with volume and increased effort will not increase flow rate. Occurs after about 75% vital capacity during expiration

Question 25

PA is _____ at rest and becomes ______ during inspiration.

Answer 25

zero at rest, neg. during insp.

Question 26

Transpulmonary pressure PTP. How does it change during inspiration?

Answer 26

difference between PA and Ppl. Becomes more positive as you get closer to mouth (less of a difference between PA and Ppl as you move up airway)

Question 27

How are airways kept open for airflow during inspiration?

Answer 27

transpulmonary pressure surrounding airways becomes progressively more positive closer to mouth, and pressure inside airway becomes progressively less negative closer to mouth, resulting in a distending pressure to keep airways open. ???

Question 28

What conditions are required for airway to stay open?

Answer 28

Intra-airway pressure must be greater (more positive) than the Ppl

Question 29

equal pressure point

Answer 29

PTP = 0. Where airway pressure equals plueral pressure. Airway has collapsing force beyond this point because PTP becomes negative

Question 30

How does increased expiratory effort affect Ppl and equal pressure point?

Answer 30

makes Ppl more positive, moving equal pressure point down airway and causing airway collapse

Question 31

Decreasing airway diameter –> airway resistance?

Answer 31

increases airway R

Question 32

Where does equal pressure point normally occur?

Answer 32

In cartilaginous airways (cartilage prevents collapse)

Question 33

Increased compliance –> lung elastic recoil

Answer 33

decreases

Question 34

decreased lung elastic recoil –> difference between Ppl and PA?

Answer 34

decreased difference

Question 35

emphysema –> compliance and elastic recoil

Answer 35

increased C, decreased recoil. Leads to trouble expiring and increased collapsing force on small airways. Gas trap

Question 36

emphysema –> equal pressure point?

Answer 36

moves closer to alveolus

Question 37

asthma –> equal pressure point?

Answer 37

moves towards alveolus b/c of increased resistance and large pressure drop in small airways

Question 38

lung recoil/collapsing force is a fx of

Answer 38

compliance

Question 39

lung recoil produces what kind of force?

Answer 39

inward collapsing force

Question 40

Active P + Recoil P =

Answer 40

Net expiratory P

Question 41

2 ways to generate active force to produce a P gradient:

Answer 41

1) elastic recoil

2) applying expiratory mm. to system and increasing P as a fx of active + passive force