LEC9: SCBA Lung Volumes WOB Flashcards
What are the changes in breathing pattern with SCBA during heavy exercise?
- Relatively more time spent exhaling
- Relatively less time spent inhaling
- Reduced tidal volume
- Upward shift for operating lung volumes
- Higher expiratory pressures
Type of air flow for helium
Laminar flow
Lower density, less resistance to flow
Type of air flow for nitrogen
Turbulent flow
higher density, more resistance to flow
Helium has (blank) possible with less respiratory muscle effort
higher flow rate
Pulmonary Physiology Terminology: volume definition
Used to describe a specific component
eg. Residual volume (RV), tidal volume (TV or VT)
Pulmonary Physiology Terminology: capacity definition
Used to describe the sum of several components (volumes)
eg. Total lung capacity (TLC), is the maximum amount of air that can fill the lungs (TLC = TV + IRV + ERV + RV)
What is inspiratory capacity (IC)?
The maximum volume of air that can be inspired after reaching the end of a normal, quiet expiration
The SUM of the TIDAL VOLUME and the INSPIRATORY RESERVE VOLUME
What is the tidal volume (TV)?
Describes the volume of air that is inspired then expired during one uninterrupted breathing cycle.
What is end inspiratory lung volume (EILV)?
The point where inspiration finishes relative to the total lung capacity
What is end expiratory lung volume (EELV)?
The point where expiration finishes relative to the total lung capacity
How to measure the changes in pleural pressure?
Changes in pressure measured in the esophagus reflect changes in pleural pressure
What is respiratory effort determined by?
Changes in pleural pressure
Pleural pressure is the next effect of (blank) and (blank) effort
Resistive, elastic
What is resistive effort (flow)?
Due to airway and airflow resistance
What is elastic effort (recoil)?
Due to resistance due to the elastic recoil of the lung and the chest wall
What is lung compliance?
The more the lung fills, the more pressure is needed to change lung volume
Lung compliance decreases at higher (fuller) lung volumes
Compliance = ΔV / ΔP
What is compliance?
A physical term that relates change in volume to the change in pressure
A lung with high compliance is what?
Easily distended (stretched)
A chest wall with low compliance is what?
Not easily collapsed
How to determine pulmonary compliance?
Change (Δ) in volume per unit of pressure
CL = Δ V (in liters) / Δ P (in cm H2O)
Chest wall compliance is the (blank) of elasticity
opposite
What is elasticity in the lung?
Elasticity is the
tendency of lung tissue to return to its original (or relaxed) position after an applied force has been removed
Therefore Chest Wall compliance is a factor at higher not lower pleural pressures
Changes in internal box pressure reflect changes in (blank)
Chest wall and lung configuration
What is Boyle’s law?
P1V1 = P2V2
Box pressure change is converted to change in lung volume
Reasons that the SCBA could decrease exercise performance
- Load carriage
a. Increased energy requirements
b. Possibly altered biomechanics - Restricted breathing
a. Altered breathing pattern
b. Greater resistance to flow
What does viscosity mean?
Measure of resistance to flow in a liquid or gas (higher viscosity means more resistance to flow)
What does density mean?
Measure of how tightly packed matter is in a solid, liquid, or gas (lower density, less resistance to flow)
How does hyperoxia affect VO2max?
- More oxygen can be carried to working muscle
2, Same cardiac output delivers 8-10% more oxygen
How does helium affect VO2max?
- Flow remains laminar longer, less turbulent flow permits higher ventilation at the same level of respiratory effort
- Peak VE is higher, hence peak VO2 can also increase
How does the combination of helium and hyperoxia provide a “countermeasure” to the detrimental effects of FPE and the SCBA on VO2max?
- This is the “super-mix”
- Peak VO2 is affected in two ways
a. Better O2 transport
b. Higher VE
How does hyperoxia affect responses to submaximal exercise?
- Improved oxygen transport
- Same cardiac output delivers 8-10% more oxygen
- SaO2 is higher (less desaturation)
- HR is lower
- BLac- is lower (could this affect ventilation?)
- VE is lower (think about air conservation)
How does helium affect responses to submaximal exercise?
- Less turbulent flow permits lower respiratory effort at same ventilation
- Reduced respiratory muscle fatigue
