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Physiology Winter 2012 > Physiology Respiratory Sukowski 2 > Flashcards

Physiology Respiratory Sukowski 2 Flashcards

1
Q

What are the dynamic properties of ventilation (3)

A
  1. Elastic recoil of lungs and chest wall
  2. Resistance to air flow
  3. Three patterns of airflow through tubes (laminar, transitional, turbulent)
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2
Q

Factors that determine airway resistance (3)

A
  1. Viscosity
  2. Lung volume
  3. State of contraction of bronchial smooth muscle
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3
Q

Elastic recoil

A

(1/compliance) of lung and chest wall (due to ST and tissue elastic elements). Also involved in static recoil at FRC

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4
Q

Where was Resistance to airflow come from?

A

4/5 (80%)- airway resisstance due to MEDIUM SIZED BRONCHI

20% due to airways <2 mm in diamter

1/5 Tissue resistance

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5
Q

When is air flow laminar

A

very small airways ,

Pressure upstream> Pressure downstream

Slow rate,
flow rate higher at center of tube than elsewehre, flow is proprotional to difference

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6
Q

When is air flow Turbulent

A

IN very large airways with high velocity

Re number >2000
Re# = 2rvd/n

movement of gas i random

flatter velocity profile?

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7
Q

When is air flow TransitionalI

A

In most airways esp at branch points

where tue divdies

faster rate than lamina,
Flow is proportional to square of pressure difference

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8
Q

What does astham do to flow rate?

A

Poiusellies law! Decrease in radius –> Increas resistnae!!!

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9
Q

What is flow like in trachea?

A

Problby turbulent during exercise

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10
Q

Hihg density gas vs high viscocity flow

A

High density - turbulent

High viscosit = laminar

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11
Q

Which airway part has most resistance?

A

medium sized bronchi

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12
Q

Viscoscity and AWR

A

increase in viscosicty elevates AWR for laminar flow but

REDUCES AWR for Turbulent flow (Re=2rd/n)

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13
Q

Lung volume and AWR

A
  1. Bronchi are pulled open by radial traction (interdependence) as lung expands to large volume (AWR decreases due to increased radius)
  2. At low lung volums, small airways at base of lung close and trap air. These small airways are “silent zone” - contribute littel to overall AWR
  3. Considerable small airway disease can be prsent but remain undetected by usual AWR measurements bc medium-sized airways contribuet the predominate AWR
  4. Patients with inc. AWR (emphysema or asthma= OBSTRUCTIVE DISEASE) breathe at large lung volume (top of ung) to minimize AWR and reduce work of breahting
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14
Q

State of contraction of bronchial SM

A
  1. Bronchoconstrcition
    - PS (Ach)
    - Effrent reflexes provoked by irritants
    - Decrease PACO2 –> Vasocconstriction
    - Histamine constricts SM of alveolar ducts
2. Bronchodilation
Symp
NE
E
Isoproteneralol
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15
Q

What are two reasons why IP falls during inspriation

A
  1. increase lung volume, and increases static recoil
  2. Fall in IP pressure necessary for inspriation to occur

Also needsto overcome AWR + Static recoil

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16
Q

Do pts with severe COPD brathe with high lung voluem or low?

A

HIGH! –> to have low resistance, otherwise will be too hight and cannot stay alive

17
Q

Flow rate

A

limited and effort independent

18
Q

Compression, nost closure of larger airwasy

A

Transmural PRessure= Pinside- Poutside

Pressure holding champber of airwayopen

19
Q

Why does max flow rate decerase with decreaasing lung volume

A
  1. difference between alveolar P and intrapleural P lessens causing a decreased driving pressure
    DF decreases, decrease elastic recoil
  2. As the volume decreases, there is less radial traction on the airways causing a progressive increase in AWR
20
Q

Forced INSPIRATion and flow rate

A

the harder you inspire, the lower hte IP pressure, the higher the flow rate

21
Q

Mechanism of Dynamic Compression of Larger Airways with Forced Expiration

A

Compressino of larger airways duing forced expriation. When Transmural P (pressure difference across airway) beomes negative (inside-outside) airways will collapse

As forced expriation contineus, equal presure poitn will move inwards (towards lungs) b/c you are exhaling air and airway pressue rapidly falls due to AWR increaseing as lung ovlume decreases

22
Q

What happens to large airways during forced expriation

A

they will COMPReSSS not close

This causes a linear diminution of the flow rate that is effort independent

23
Q

What happens to equal pressure point (iintrapleurla P) as forced expiration continues

A

Equal pessure point will move inwards towards teh lung

24
Q

Whawt happens to small airways during gentle expiration towards RV

A

dependent small airways are closed, witha gentle expiration toward RV

Traps air int eh distal avleoli

25
Q

What are factors that exaggerate the Flow-Limiting Mechanism

A

Any condition that would increase AWR or Decrease Lung Recoil or both

  1. Increase of Peripheral airwasy (magnifies the presure drop and decreases intrabronchial P during expiration; emphysema with dec. radila traction on airways)
  2. Low lung volume –> Increase AWR and Decrease Lung recoil (reducing driving pressure - alveolar P - Intrap P)
  3. Inc lugn compliance (decrease recoil)
26
Q

Why is it harder to inflate and defate empysemic lung

A

increase ARD

Total lung volume is larger than for normal (eg 9.5 L vs 7L)

while Vital capacity is less than for normal (3.5 vs 4.5 L)

27
Q

What are three causes of Uneven Ventilation in Different Lung Units at any given vertical level

A
  1. decreased cmpliance
  2. increased AWR
  3. Incompeltel diffusion in airways of respriatory zone 9enlarged space as in emphysema)
28
Q

Uneven ventilation with restrictive disease

A

B- decrease comlaince (stiff lugn with high recoil) = rapid but small chagne in volume

29
Q

C- Obstructuve disease and uneven ventilation

A

increase AWR= slow to fill and empty; may not complete filing, small volume due to long tie cosntant

30
Q

what diseases ahve increases in AWR in larger airways with lon time constants

A

Obstructive disease of emphysema, bronchitis, and asthma

31
Q

What diseases have increase in AWR in small airways and alveoli with logn time constants

A

fibrosis in small airways

alveoli with unequal ventiatliona dn tehrefore, long tiem constraits

Normal, parallel, series (semphysema) collagteral

32
Q

Work done on lung equation

A

Pressure x volume

33
Q

What does work of lugn need to overcome

A
  1. Elastic forces (lugn recoil; collagen/elastin and ST)

Static: at FRC, before brething
Dynamic: during breathign

  1. Viscious forces
    - 80% due to AWR (medium-sized pulmoanry airways)
    - 20% due to tissue resistance (friction)

total work of breathing

restful vs exercise

34
Q

Restrictve lung work

A

mroe negative IP P at FRC

Requires more qork than normalt o move the same volume of air due to STIFFNESS of lung (fibrosis

RAPID, SHALLOW BREATHS

35
Q

Obstructive Lung Work

A

less negative IP Pat FRC
Requires mroe work than normal (esp. during expriation), b/c of high AWR (emphysema, bronchitis)

Slow, deep breaths

Physiology Winter 2012 (10 decks)

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