2- Ventilation Flashcards
Distinguish between pulmonary and alveolar ventilation
Pulmonary is air ventilating the entire airway; alveolar is air ventilating respiratory surfaces
Define the common lung volumes/capacities - 8 of them
TV: volume of air in and out in each breath to meet metabolic demand
RV: least possible air in lungs
VC: total volume of air that can be move in one breath
IRV: volume of reserve if you need to inspire further
ERV: volume of air if you need to expire further
TLC: total maximum lung capacity
FRC: functional residual capacity
IC: inspiratory capacity
Explain what happens to lung capacities in obstructive and restrictive diseases
Obstructive (typical): ↔↑RV; ↔↑TV; ↓↔IRV; ↓↔ERV; ↔↑ TLC; ↔↑FRC; ↓↔VC
•Restrictive (typical): ↓ RV; ↔↓TV; ↓IRV; ↔↓ERV; ↓TLC; ↓FRC; ↓VC;
What is physiological, anatomical and alveolar dead space
Equivalent to the sum of alveolar and anatomical dead space
The capacity of the airways incapable of undertaking gas exchange
Capacity of the airways that should be able to undertake gas exchange but cannot (e.g. hypoperfused alveoli)
What is minute ventilation
The volume of air expired in one minute (VE) or per minute (V̇E)
What is alveolar ventilation
The volume of air reaching the respiratory zone
Explain the mechanical relationship between the chest wall, pleural membranes and the lung
Healthy chest behaves as a single unit; pleural cavity is a partial vacuum
Ventilation can be positive pressure (ventilation/CPR) or negative pressure (normal breathing)
Distinguish the mechanical forces involved in tidal and maximal ventilation
Tidal breathing is predominantly diaphragm-induced (syringe movement)
Maximum ventilation involves full inspiratory muscle recruitment (syringe and bucket handle movement)
Explain the utility of common lung function tests and how the results differ between healthy individuals and patients with obstructive and/or restrictive lung disease
Peak flow – tests airway resistance (how fast can air be expired?)
Time-volume curve – tests airway resistance and FVC
Flow volume loop – tests airway resistance, flow rates, TV, IRV, ERV and FVC
Explain the regional differences in ventilation and perfusion
Gravity favours ventilation and perfusion of the basal lung versus the apical lung; perfusion more variable
Basal lung has ‘wasted perfusion’ and apical lung has ‘wasted ventilation’
What is the tendency of the chest wall and lung
Chest wall springs outwards
Lung recoils inwards
What 2 things can cause a pneumothorax
Perforated lung or chest wall
What is the average intrapleural pressure
-5cmH2O, this decreases to -8 on inspiration
What does a volume time curve allow you to calculate
FEV1/ FVC ratio
What are the steps on the flow volume curve
Patient completes at least one tidal breath (A&B)
Patient inhales steadily to TLC (C)
Patient exhales as hard and fast as possible (D)
Exhalation continues until RV is reached (E)
Patient immediately inhales to TLC (F)
