Pulmonary 3 Flashcards
What are the two major air flow determinants at a given pressure gradient?
- Pattern of Gas Flow
2. Resistance to air flow by Airways
What is the equation for laminar flow?
Turbulent flow?
V(flow) =
(Pressure r^4pi) / 8Ln
Reynolds Number
R= densityDiameterVelocity/ viscosity
Anything LESS than 2000 = laminar
greater than 2000 = TURBULENT
Where is airflow most turbulent? Where does it become laminar? Where does diffusion occur?
- In the TRACHEA: largest diameter and velocity is high
- Higher Airway becomes laminar
- Diffusion occurs in the RESPIRATORY ZONE –> slow velocity
Where is the highest resistance found? Why does this not follow the usually rules of resistance = 1/r^4 (aka smaller vessels have greater resistance)?
- in Generation 4
(highest in zones 1-6) - Due to the BRANCHING the system is in PARALLEL so the short length & frequent branching area has HIGHEST resistance = TURBULENT FLOW
What is the resistance in the Respiratory zone where the alveoli reside? Where is true laminar found?
Resistance in the Respiratory Zone is
LOW
- True laminar is found in the VERY SMALL
BRONCHIOLES - zones 10-16!!
Large airways = TURBULENT FLOW
then turns into Laminar
in RESPIRATORY ZONE
- FLOWS VIA DIFFUSION
How is conductance related to resistance?
What happens to conductance and Airway Resistance (AWR) during:
- Lung Volume increases
- Sympathetic Stimulation via B2 agonists
C= 1/R
- Conductance Increase
- AWR DECREASES
For BOTH!
- when you expand the lung, the diameter of the airways is enlarged so resistance is decreased
How do the following affect resistance and thus conductance?
- Vagal Stimulation
- Edema
- Viral INfection
ALL INCREASE AWR
- so conductance decreases
- vagal stimulation causes smooth muscle in the airway to CONTRACT
What is FVC? FEV1?
How is this ratio expressed? What is a NORMAL value of this ratio?
FVC = forced vital Capacity
-breating at tidal volume & ask patient to take a full inspiration & forced expiration
(FVC = IRV+VT+ERV)
FEV1 = forced expiratory volume in 1 s
FEV1/FVC
- usually around 75% is NORMAL
What is FEV1 a measure of? What does a smaller FEV1 signify? What is a clinical case of a smaller FEV1?
Airway resistance!
- smaller FEV1 means INCREASED resistance to expiratory airflow!
- ASTHMA! = trapping air in lungs
If the FEV1/FVC ratio is less than 75% what does this mean? Greater than 75?
- OBSTRUCTIVE disease
2. Normal if OVER 75%
What is different about PEFR and PIFR in a flow volume loop?
- PEFR occurs EARLY
2. Flow rates for PEFR decrease as they approach RV due to expiratory flow limitation
What is PEFR and PIFR? What values are they on a Flow-Volume loop (aka which is most positive, most negative)
PEFR = Peak Expiratory FLow Rate (9.5l/sec)
PIFR = Peak Inspiratory Flow Rate (-10 L.sec)
PIFR = NEGATIVE PEFR = POSTIVE
What happens to the following during INSIRATION as lung volume increases:
(increase/decrease)
- Force of inspiratory muscle
- Lung Recoil Pressure
- Airway Resistance
- Max Inspiratory Flow
- Force of inspiratory muscle DECREASES
- Lung recoil pressure INCREASES
- Resistance DECREASES
- Max Inspiratory flow occurs HALFWAY between TLC and RV
What is Expiratory Flow limitation? How is this represented on a Flow-VOlume loop?
- due to the dynamic compression of airways
once the pressure gradient is reduced and the pressure outside is greater than the pressure inside = EXPIRATORY FLOW LIMITATION
slow decline towards RV!
The following describes Expiratory Flow rates at High Volumes or Low volumes?
- Effort Independent
- Flow Limited
LOWER LUNG VOLUMES
When is expiratory flow EFFORT DEPENDENT?
At HIGH volumes
1.What happens at the Equal Pressure Point?
When is this altered?
2.When is airflow resistance highest?
- Airflow becomes INDEPENDENT of total driving pressure
- in normal lungs, this usually occurs at an area of cartilage so that the airway is not compressed
- It is altered in DISEASE (obstruction) leading to premature airway closing (air trapping) - Airflow resistance is greater during EXHALATION
When is FEV1 reduced? When is FVC reduced?
- OBSTRUCTIVE lung disease in Asthma, COPD
2. FVC reduced in RESTRICTIVE lung diseases aka fibrosis
In restrictive disease, what is usually normal?
FEV1/FVC since only FVC is decreasing (total ratio becomes greater than 75%)
When using Albuterol (B2 Agonist) what happens to FEV1/FVC?
FEV1/FVC ratio becomes NORMAL!
w/o albuterol, the FEV1 is very low since this is an OBSTRUCTIVE disease
In obstructive lung disease how is flow affected? In restrictive? What is different in restrictive lung disease?
Obstructive - flow is SIGNIFICANTLY reduced
Restrictive - flow rates appear normal, but vital CAPACITY is reduced
(max amount of air that can be expired with max inhalation)
How are the following changed in OBSTRUCTIVE disorders:
- FEV1/FVC
- FEV1
- FVC
- TLC
- RV
- FEV1/FVC-decreased
- FEV1 - Decreased
- FVC - decreased/normal
- TLC - normal or increased
- RV - normal or increased
How are the following changed in RESTRICTIVE disorders:
- FEV1/FVC
- FEV1
- FVC
- TLC
- RV
- FEV1/FVC - normal/increased
- FEV1 - Decreased/Normal/ or increased
- FVC - DECREASED
- TLC - DECREASED
- RV - DECREASED
What are the 2 main components of respiratory work? (TOTAL WORK)
- Elastic Work
2. Work to Overcome Airflow Resistance
