Important concepts for ventilation facilitation Mx

Concepts for Mx of ventilation

Critical opening pressure

Newtonian Law of Viscosity

Collateral ventilation

Alveolar interdependence

Time constants

Definition of critical opening pressure

Pressure needed to overcome surface tension

Why slow laminar flow + application

Why: 

1. Allow regions w/ long time constraints to fill 

2. Fill lower lung regions 

3. Encourage opening of alveoli

Application:

Inspiration should be: 

1. Slow 

2. Deep 

3. Smooth 

4. From FRC

Description of collateral ventilation

Blockage of bronchiole → distal unit of alveoli at risk of collapse → connecting channels  activate → maintain V/Q match 

• Interbronchiolar channels of Martin

• Bronchiolar-alveolar channels of Lambert

• Alveolar pores of Kohn

Description of alveolar interdependence

→ principle of spreading mechanical stress over a group of alveoli → contributes to elastic recoil of lungs

1. Alveoli interconnected 

2. Alveolus start to collapse 

3. Surface tension from interconnected alveoli pull the collapsing alveolus open

Description of time constants

Time constant: compliance x resistance of alveolar unit  Healthy lung: time constants relatively uniform across all alveoli → same rate + pressure to inflate alveoli  Impaired lung: time constants X uniform across all alveoli  → different rate + pressure needed to inflate alveoli  → Higher resistance/ compliance → more time to inflate  → lower compliance → greater inspiratory effort to inflate → ↑ respiratory rate  → ↓ time for inspiration + expiration  → ↓ ventilation  Techniques: inspiratory hold → accommodate different time constants