Ventilation Flashcards
What are the two components of the chest-wall?
Independent Lung
Independent rib cage and muscles
What is Functional Residual Capacity?
FRC = ERV + RV
It is the volume of air remaining in the lungs at the end of a tidal breath. At FRC, the recoil inwards of the lungs and the recoil outwards of the chest wall are in equilibrium.
Describe how the pleural cavity allows the chest wall and the lungs to move in unison.
The pleural cavity has a fixed volume and is at negative pressure. This means that when the chest wall expands, the lung gets pulled with it.
How may the fixed volume of the pleural cavity be compromised?
The pleural lining could get punctured in the case of a haemothorax or pneumothorax.
Which volumes make up each of the following capacities: Total Lung Capacity Vital Capacity Functional Residual Capacity Inspiratory Capacity
Total Lung Capacity - all the volumes together
Vital Capacity - expiratory reserve volume, inspiratory reserve volume + tidal volume
Functional Residual Capacity - (ERV + RV)
Inspiratory Capacity - (TV + IRV)
Define Tidal Volume.
The amount of inspiration and expiration that meets metabolic demands.
Why can’t we totally expel all air from our lungs?
The surfactant in the alveoli prevent the alveoli from collapsing and so you can’t expel all the air from the lungs.
What unit is commonly used when describing lung pressures?
Unit: cm H2O
What are the three main lung pressures involved in respiratory mechanics? Define them.
Transmural Pressure = pressure across a tissue: inside -outside
Transpulmonary Pressure = difference between alveolar and intrapleural pressure
Transrespiratory Pressure = tells us the direction of airflow in the airways
If transrepsiratory pressure is positive air will flow in. If it is negative it will flow out.
Give two examples of positive pressure breathing.
CPR and Ventilators
What is the difference in alveolar pressure between the end of a tidal expiration and the end of tidal inspiration? Explain your answer.
NO DIFFERENCE - during inspiration, the thoracic cavity expands and so the alveoli expand and the pressure decreases. Air is drawn in to the alveoli and the pressure becomes the same as it was at the end of expiration.
Define Dead Space.
Parts of the airways and lungs that do not participate in gas exchange.
What are the two different types of dead space?
Anatomical Dead Space and Alveolar Dead Space
What is the normal physiological dead space of a healthy individual?
150 mL - physiological dead space is usually equivalent to anatomical dead space because normal healthy people don’t have alveolar dead space
State two reversible procedures that can change dead space.
- Decrease: - Tracheostomy or Cricothyroidotomy
2. Increase: Ventilators