17 Pulmonary: Airflow And Resistance

Front 1

conducting zone

Back 1

- all bronchi and bronchioles to terminal bronchioles
- no alveoli so no gas exchange
- air movement by bulk flow

Front 2

respiratory zone

Back 2

- distal to terminal bronchiole --> Acinus
- largest volume (2.5 - 3 L)
- movement: diffusion b/c of large cross sectional area

Front 3

air flow

Back 3

- due to differences in pressure across airway
- rate: proportional to driving pressure, inverse to airway resistance
- V(. flowrate) = ΔP/R
- valid under laminar flow

Front 4

Poiseuille's Law

Back 4

R = 8nl/pi r^4

flowrate and pressure under laminar flow
- R = resistance
- n = viscosity of gas
- l = length of tube
- decrease in radius by half increases resistance by 16 fold

Front 5

reynold's number

Back 5

- effect of radius on resistance greater if flow is turbulent
- determines if laminar or turbulent
- Re= (vrd/n)
v = average velocity
d = density
r = radius
n = viscosity

Less than 2000 --> laminar

Front 6

Airway tone

Back 6

- airway antomy:
- brochi are airways til 9th generation, contain cartilage
- bronchioles at 10-15 generation no cartilage, airway maintained by surrounding tissue and smooth muscle tone

Front 7

Parasympathetic

Back 7

- stimulation (Ach, metacholine) --> bronchoconstriction
- atropine, ipatropium and bromide cause bronchodilation

Front 8

Sympathetic

Back 8

- circulating catecholamines --> bronchodilation by stimulating β2 receptors on bronchial smooth muscle

Front 9

Vital capacity maneuver

Back 9

- performed under maximum expiratory flow (FVC)
- maximum inspiration followed by maximum expiration
- spirometer measures volume and flow

Front 10

flow volume graphs

Back 10

- beings exhaling at TLC and continues until RV is reached
- instantaneous maximum flow (peak expiratory flow) ↓ in conditions of increased Air resistance
- distinct patterns for dx compared to normal
- width of flow-volume graph = FVC
- height and shape of expiratory limb of loop = flow capabilities

Front 11

Effort dependence

Back 11

- expiratory flow through early airways effort and volume dependent
- through small airways, effort independent

Front 12

dynamic airway compression

Back 12

- closure of airways due to ↑ PIP
- in normal: PIP less than PB , PA starts higher than PB then --> 0
- PTM is + and acts on airway wall to keep it open
-on forced expiration:
- PIP > PB and PA>PB
- as long as pressure in airway > PIP airways remain open
- when airway pressure =PIP = Equal pressure point PTM= 0
- downstream from EPP, airway pressure < than PIP airway collapses

Front 13

FVC maneuver tracings

Back 13

- FEV1 (O-1 second) lowered means airway obstruction
- FEV1/FVC - ratio of amount expired in 1 sec to total expired (to peak of maximal inspiration to where graph peters out)
- FEF(25-75%) measured airflow through small to middle sized airways
- airflow reduction can be detected here, steeper slope in normal FVC x .25

Front 14

Restrictive Dx

Back 14

- volumes reduced
- "obstructive to flow, restrictive to volume"

Front 15

Obstructive Dx

Back 15

- flows are reduced
- "obstructive to flow, restrictive to volume"

Front 16

Values in Flow/volume graphs

FVC

Back 16

decreased in obstructive and restrictive

Front 17

FEV1

Back 17

decreased in obstructive and restrictive

Front 18

FEV1/FVC

Back 18

- decreased in obstructive
- normal or high in restrictive