Respiratory Engineering Flashcards
What are the two types of respiration?
Internal - Gas exchange between blood and cells.
External - Gas exchange between external environment & body.
Name the six stages of the airways?
- Pharynx/Throat
- Larynx
- Trachea
- Bronchi
- Bronchioles
- Alveoli
Outline the mechanics of breathing for inspiration/expiration.
Inspiration - Intercostals + diaphragm contract to expand chest cavity (reduced plural pressure, lungs expand)
Expiration - Muscles relax, reduce volume
What are the two ways in which the chest cavity is expanded?
Contraction of diaphragm - lengthen cavity.
Contraction of external intercostal muscles - lift rib cage, increase anterior, posterior size.
What are the two ways in which the chest cavity is contracted?
Contraction of abdominals - pulls rib cage down.
Contraction of internal intercostal muscles - reduce anterior, posterior size.
Name the four main pulmonary volumes.
- Tidal Volume (volume inspired)
- Inspiratory Reserve Volume (extra volume above tidal inspiring at full force)
- Expiratory Reserve Volume (extra volume above tidal expiring at full force)
- Residual Volume (air remaining after most forceful expiration)
Name the four pulmonary capacities.
- Total lung capacity
- Inspiratory capacity
- Functional residual capacity
- Vital capacity
What are the two types of dead space?
Anatomical - Volume of conducing airways
Physiological - Volume of gas that doesn’t eliminate CO2
How is O2 carried in the blood and what effects its uptake.
O2 binds to haemoglobin in RBCs to form oxyhaemoglobin.
Uptake effected by partial pressure of O2 and CO2.
How is CO2 carried in the blood?
Physical solution
Bicarbonate
Carbamino compound
Explain the relationship between O2 partial pressure and haemoglobin saturation?
Low O2 partial pressure - readily binds to haemoglobin. When exposed to lower PO2 oxygen is released. (steep curve)
High O2 partial pressure - smaller amounts absorbed - plateau. Little change in saturation for change in PO2.
What are the two types of mechanical ventilation?
Negative Pressure - Negative pressure around chest for expansion.
Positive Pressure - Air pushed in through nose.
What are the two options for delivering air in a positive pressure system?
Volume Generator - Use known volume.
Pressure Generator - Use known pressure.
State the advantages and disadvantages of a volume generator for ventilation.
Advantages - Correct amount of air received for proper ventilation.
Disadvantages - High pressure may be required if airways constricted. Risk of barotrauma.
State the advantages and disadvantages of a pressure generator for ventilation.
Advantages - Avoids risk of barotrauma.
Disadvantages - Volume delivered depends on resistance of airways and lung compliance. May not receive correct volume for ventilation or over-inflate (volutrauma).
What are the five main ventilation parameters?
- Tidal Volume (Vt)
- Fraction of inspired oxygen (FiO2)
- Airway pressure (Paw)
- Respiration rate (breaths/min)
- Inspiration to expiration ration (I:E).
State and describe the four main airway pressures.
- Positive end expiratory pressure (PEEP).
- Peak inspiratory pressure (PIP).
- Plateau pressure (Pplat).
- delta P (Pplat - PEEP).
Explain the four main ventilation induced injuries.
Barotrauma - Excessive dP between alveoli and abdomen. Air embolism in interstitial tissue.
Volutrauma - Excessive volume causes lungs to stretch. Pulmonary edema, damage to alveoli etc.
Atelectrauma - Repeated low volume/pressure causes cyclic opening and closing of damaged alveoli.
Biotrauma - Injuries due to biological response.
What is continuous positive airway pressure?
Less invasive form of mechanical ventilation. Low but continuous pressure of O2 applied to nose. Patient still controls breathing/
What are the tree elements of anaesthesia?
- Pain relief
- Paralysis/immobility
- Unconciousness
What is Minimum Alveolar Concentration (MAC) in the context of anaesthesia?
Minimum concentration which prevents movement in 50% of population.
How does Henry’s law apply to anaesthetic drug concentration?
C_blood = partition coefficient (blood:gas) * C_gas
How do inhaled anaesthetic drugs reach the brain?
Drug diffuses from alveoli into blood, circulates around body and diffuses into tissue including the brain.
Partial pressure drives the equilibrium processes.
