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
What is Elastic Work?(3 types)
What is it proportional to?
- Work to overcome Elastic Recoil of lungs
- To Expand Thoracic Cage
- Work to Dispace abdominal organs
Proportional to TIDAL VOLUME
What is non elastic work? What is this proportional to?
Work to overcome airflow resistance
Proportional to BREATHING FREQUENCY
When is work increased? (4)
- Pulmonary compliance is reduced
- Airway resistance is increased
- Elastic recoil is decreased
- Exercise, however total energy is also increased,
proportion remains at ~5%
What type of increased work are the following:
- Pulmonary Fibrosis
- COPD
How does breathing change in both of this conditions?
- Fibrosis = Increased elastic Work
- breathing is shallow & rapid - Increased Flow Resistive Work = breathing becomes slow & deep
What is the Equal Pressure Point? When is this point closer to the alveolus?
Pressure inside =Pressure outside
During COPD equal pressure point is closer so the flow is reduced
How is dynamic compression determined? What does it limit & when specifically? (expiration/inspiration)
- Determined by Alveolar - Pleural Pressure (PA - Ppl)
2. Limits the AIRFLOW during FORCED EXPIRATION
When is work of breathing MINIMAL?
Normal Tidal Volume Ventilation
How do patients with lung disease minimize work of breathing?
Change the breathing patterns & frequency
