Physiology Respiratory Sukowski 2 Flashcards
What are the dynamic properties of ventilation (3)
- Elastic recoil of lungs and chest wall
- Resistance to air flow
- Three patterns of airflow through tubes (laminar, transitional, turbulent)
Factors that determine airway resistance (3)
- Viscosity
- Lung volume
- State of contraction of bronchial smooth muscle
Elastic recoil
(1/compliance) of lung and chest wall (due to ST and tissue elastic elements). Also involved in static recoil at FRC
Where was Resistance to airflow come from?
4/5 (80%)- airway resisstance due to MEDIUM SIZED BRONCHI
20% due to airways <2 mm in diamter
1/5 Tissue resistance
When is air flow laminar
very small airways ,
Pressure upstream> Pressure downstream
Slow rate,
flow rate higher at center of tube than elsewehre, flow is proprotional to difference
When is air flow Turbulent
IN very large airways with high velocity
Re number >2000
Re# = 2rvd/n
movement of gas i random
flatter velocity profile?
When is air flow TransitionalI
In most airways esp at branch points
where tue divdies
faster rate than lamina,
Flow is proportional to square of pressure difference
What does astham do to flow rate?
Poiusellies law! Decrease in radius –> Increas resistnae!!!
What is flow like in trachea?
Problby turbulent during exercise
Hihg density gas vs high viscocity flow
High density - turbulent
High viscosit = laminar
Which airway part has most resistance?
medium sized bronchi
Viscoscity and AWR
increase in viscosicty elevates AWR for laminar flow but
REDUCES AWR for Turbulent flow (Re=2rd/n)
Lung volume and AWR
- Bronchi are pulled open by radial traction (interdependence) as lung expands to large volume (AWR decreases due to increased radius)
- 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
- Considerable small airway disease can be prsent but remain undetected by usual AWR measurements bc medium-sized airways contribuet the predominate AWR
- 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
State of contraction of bronchial SM
- Bronchoconstrcition
- PS (Ach)
- Effrent reflexes provoked by irritants
- Decrease PACO2 –> Vasocconstriction
- Histamine constricts SM of alveolar ducts
2. Bronchodilation Symp NE E Isoproteneralol
What are two reasons why IP falls during inspriation
- increase lung volume, and increases static recoil
- Fall in IP pressure necessary for inspriation to occur
Also needsto overcome AWR + Static recoil
Do pts with severe COPD brathe with high lung voluem or low?
HIGH! –> to have low resistance, otherwise will be too hight and cannot stay alive
Flow rate
limited and effort independent
Compression, nost closure of larger airwasy
Transmural PRessure= Pinside- Poutside
Pressure holding champber of airwayopen
Why does max flow rate decerase with decreaasing lung volume
- difference between alveolar P and intrapleural P lessens causing a decreased driving pressure
DF decreases, decrease elastic recoil - As the volume decreases, there is less radial traction on the airways causing a progressive increase in AWR
Forced INSPIRATion and flow rate
the harder you inspire, the lower hte IP pressure, the higher the flow rate
Mechanism of Dynamic Compression of Larger Airways with Forced Expiration
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
What happens to large airways during forced expriation
they will COMPReSSS not close
This causes a linear diminution of the flow rate that is effort independent
What happens to equal pressure point (iintrapleurla P) as forced expiration continues
Equal pessure point will move inwards towards teh lung
Whawt happens to small airways during gentle expiration towards RV
dependent small airways are closed, witha gentle expiration toward RV
Traps air int eh distal avleoli
What are factors that exaggerate the Flow-Limiting Mechanism
Any condition that would increase AWR or Decrease Lung Recoil or both
- Increase of Peripheral airwasy (magnifies the presure drop and decreases intrabronchial P during expiration; emphysema with dec. radila traction on airways)
- Low lung volume –> Increase AWR and Decrease Lung recoil (reducing driving pressure - alveolar P - Intrap P)
- Inc lugn compliance (decrease recoil)
Why is it harder to inflate and defate empysemic lung
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)
What are three causes of Uneven Ventilation in Different Lung Units at any given vertical level
- decreased cmpliance
- increased AWR
- Incompeltel diffusion in airways of respriatory zone 9enlarged space as in emphysema)
Uneven ventilation with restrictive disease
B- decrease comlaince (stiff lugn with high recoil) = rapid but small chagne in volume
C- Obstructuve disease and uneven ventilation
increase AWR= slow to fill and empty; may not complete filing, small volume due to long tie cosntant
what diseases ahve increases in AWR in larger airways with lon time constants
Obstructive disease of emphysema, bronchitis, and asthma
What diseases have increase in AWR in small airways and alveoli with logn time constants
fibrosis in small airways
alveoli with unequal ventiatliona dn tehrefore, long tiem constraits
Normal, parallel, series (semphysema) collagteral
Work done on lung equation
Pressure x volume
What does work of lugn need to overcome
- Elastic forces (lugn recoil; collagen/elastin and ST)
Static: at FRC, before brething
Dynamic: during breathign
- Viscious forces
- 80% due to AWR (medium-sized pulmoanry airways)
- 20% due to tissue resistance (friction)
total work of breathing
restful vs exercise
Restrictve lung work
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
Obstructive Lung Work
less negative IP Pat FRC
Requires mroe work than normal (esp. during expriation), b/c of high AWR (emphysema, bronchitis)
Slow, deep breaths
