Respiratory Mechanics IV Flashcards
What are the 2 components that make up the work of breathing
- Elastic -> stretching the lungs
- Nonelastic -> moving air through the airways
T or F: Chest expansion during inspiration is not resisted by the lungs
F, it is and the amount of resistance determines how much force is needed
What are the 3 components of elastic resistance
What are 2 characteristics of elastic resistance
2 characteristics of the bronchi and bronchioles
What are 3 components of nonelastic resistance
What are 2 characteristics of nonelastic resistance
What is the pleural pressure gradient
Regional variations in intrapleural pressure in resting position (due to gravity) which causes not all parts of the lungs to expand equally
Where is pressure greatest in the lung and what happens
Pressure is greatest at top (apex) of the lungs and is at lowest when at base of the lungs. This causes the expanding pressure to be much greater at the top of the lungs resulting in less lung expansion at the apex compared to the base.
Explain the slinky affect
Gravity causes the lungs to be more stretched at apex and more compressed at base resulting in greater expansion and ventilation (compliance) at the base
Elastic work of breathing depends on
1) Elastic properties of lung tissue (elastin, collagen)
2) Surface tension (tracheobronchial tree line d with fluid film)
What is lung compliance
The ease to which something can be stretched
What is the difference between lung compliance and elastisity
Elasticity is the ability to oppose stretch and return to its original shape after distortion whereas compliance is the ability to be stretched
Hysteresis
Difference between inflation and deflation of lungs usually caused by surface not decreasing surface tension as well in inspiration and due to collapsed alveoli being recruited which is wasteful energy and inspiration has increased resistance due to elastic and air restive properties whereas expiration is just airway resistance
Explain this graph
The slope of the curve = compliance
-The slope is higher at lower lung volumes meaning that at lower lung volumes the lungs can more easily expand because they have increased compliance
When does lung compliance decrease
1) At high lung volumes (elastin and collagen almost fully stretched (cant move anywhere))
2) At very low lung volumes (increased surface tension because of airway closures (derecruitment))
The ease of expansion (Ventilation) depends on
Volume of air already present
T or F: All parts of the lung are not equally expanded at rest
T: Regional differences in Ppl
What happens at normal resting volumes in terms of ventilation and compliance
What happens at residual volume in terms of ventilation and compliance
Compare lung compliance between normal, emphysema (obstructive) and lung fibrosis (restrictive)
Are inflation and deflation the same
No, the difference between the two is called hysteresis
Where along the curve is inflation easier and most difficult
Easier at low lung volumes and more difficult at high lung volumes
Is the lung ever completely empty?
No, there is always going to be residual volume
What is the pressure required to obtain given lung volumes for inflation and deflation
More pressure is required for given volume during inflation compared to deflation
What are 3 characteristics of surface tension
What are 2 contributions of surface tension in the lungs
Is the lung more compliant when filled with saline or air
More compliant when filled with saline because there is no surface tension with saline as it is a liquid. Surface tension only occurs between gas and liquid therefore lungs have no forces acting on it with a saline solution and are more easily stretched
Is the hysteresis the same in a lung filled with saline vs air
Almost no hysteresis when the lung is filled with saline
Name 3 characteristics of surfactant
Where is surfactant produce
What is the function of Type I alveoli
Form the structure of the alveoli
What is important about surfactant embryology
Type II alveolar cells take about 36 weeks to reach gestation so the lung collapses if born at 28-32 weeks and infants are at high risk of Respiratory Distress Syndrome if born before 36 weeks
Name 3 other characteristics of surfactants
What are 5 clinical importance’s of surfactant
Compare alveolar stability with and without surfactant
What is the relationship between surfactant and surface tension
Surfactant impacts surface tension and surface tension impacts lung compliance which determines the amount of elastic work required for breathing
The driving pressure required to overcome friction (airway resistance) depends on (2)
1) Rate of airflow (V)
-Pattern of airflow
What are the 3 types of lung airflow patterns
- Laminar
- Transitional
- Turbulent
Describe a laminar airflow pattern
Describe a turbulent airflow pattern
Describe a transitional airflow pattern
Compare the laminar, turbulent and transitional airways in terms of their location, airflow, characteristics, resistance, and driving pressure
What does cross-sectional area of airways determine
Overall resistance to flow
Explain the changes of airway resistance in terms of lung volumes
The airways caliber (diameter) increases as the lung expands (increased volume) therefore decreasing resistance and increasing conductance of air. Therefore airway resistance decreases on inspiration and increases on expiration
Where is the most resistance along different sites (eg. trachea, bronchus, bronchial, terminal bronchiole)
The reason there is more resistance in larger areas is because the air is not streamline vs in the smaller airways its more streamline
What are 5 clinical importance about airway resistance
What are the 2 roles of lung elastin
What are 2 ways to regulate airway caliber
What happens in bronchoconstriction in terms of airway caliber and resistance
What happens in bronchodilation in terms of airway caliber and resistance
How does the ANS regulate constriction and dilation
Describe the cough reflex
How does noradrenergic cholinergic nervous system impact the bronchial smooth muscle
How do inflammatory mediators impact the bronchial smooth muscle
Describe how bronchodilation/constriction are caused on a molecular level
Differences between a restrictive and obstructive disease
Compare inspiration vs expiration
