Ventilation And Gas Exchange Flashcards
(25 cards)
What is hyperventilation and how does it differ from tachypnoea
Excessive ventilation or lungs atop of metabolic demand (reduced PCO2, alkalosis)
Tachypnoea is abnormally fast breathing rate
After max inspirtsoty effort, why is there a plateauing then sudden drop of the chart
Requires too much muscular effort from respiratory muscles to maintain the abnormal pressure
What volume of air is measured during,ignition respiratory effort
Tidal volume
What are
Vital capacity
Inspiratory/expiratory reserve volume
Residual volume
Difference between max and min air that you can have in your lungs
Extra Volume that can be breathed in/out above/below tidal volume during a forceful breath in/out
Vol of air that remains in lungs after max expir effort
What is functional residual capacity (FRC)
Vol remaining in lungs after normal passive exhalation, point where lung tissue elastic recoil and chest wall outwards expansion are balanced and equal
What is the difference between volumes and capacities
Volumes are discrete sections and don’t overlap
Capacities are sums of 2 or more volumes
How do you calculate minute ventilation
How do you calculate alveolar ventilation
Tidal volume (L) x breathing frequency (breaths/min) Unit is L/min
(Tidal volume (L) - dead space (L)) x breathing frequency
What affects lung volumes and capacities
Body size Sex Disease (pulmonary or neurological) (COPD increases total lung capacity and residual volume, vital capacity shrunk down) Age Fitness
What are the differences between anatomical and alveolar dead space
What do they add to produce
Anatomical is in conducting zone; no gas exchange, 16 generations, typically 150mL
Alveolar is non perfumed parenchyma, alveoli without blood supply, no gas exchange, should be 0mL in adults
Physiological dead space
Which zone has 7 generations, gas exchange and air reaching it is equivalent to alveolar ventilation?
What volume is this typically in adults
Respiratory zone
Typically 350mL
What two reversible procedures could you do to
Decrease
Increase
Someone’s dead space?
Decrease: tracheostomy (get past upper airway, shortens airway, go to where cartilaginous tracheal support is as wont collapse), cricothyrocotomy
Increase: anaesthetic circuit, snorkelling
What is the chest wall relationship, and when is it at equilibrium
How are inspiration and expiration brought about (using equations)
Chest wall has tendency to spring outwards, lung has tendency to recoil inwards
Equilibrium at end tidal expiration (FRC), which is neutral position of intact chest
Inspiratory muscle effort + chest recoil > lung recoil
Chest recoil < lung recoil + expiratory muscle effort
Distort pressure equilibrium!
What can ruin pleural cavity integrity
Haemothorax (intrapleural bleeding)
Pneumothrorax (collapsed lung caused by perforated chest wall or punctured lung)
What type of breathing is
Negative pressure
Positive pressure
Normal breathing
CPR, Mechanical ventilation, fighter pilots
What laws describe gas behaviour
Dalton = total partial pressures = pressure of mixture Fick = molecules diffuse high to low proportionally to conc grad, surface area, diffusion capacity, inverse proportional to thickness of surface Henry = solubility proportional to partial pres Boyle = vol inversely proportional to pres Charles = vol proportional to temp
What gases would be present in the following situations :
Oxygen therapy
Smoke ( house fire)
High altitude
More O2
Less O2, more CO2 and COs
Percentages remain the same, pressure lower
How is inspired air modified in the airways
Conducting airways increases humidity, small decrease in pO2
Respiratory airways decrease in pO2, increase in pCO2
Air warmed, humidified, slowed and mixed down respiratory tree
What binding site is created in the middle of the relaxed Haemoglobin molecule, and what is its function
2,3-DPG (glycolytic byproduct),
facilitates unloading;
as 2,3-DPG increases, usually proportional to metabolic demand, need to deliver more oxygen
What is the pO2 of the systemic vs pulmonary circulation
Systemic 1.5-5.5
Pulmonary 9.5-13.5
How would you interpret a pulse oxidiser reading of 99%
Normal binding of O2 to Hb
HOWEVER
If there is less Hb, patient may still be ischaemic
Be cautious
Check cog function, pallor, FBC
What may cause the oxygen dissociation curve to shift to the
Left
Right
Left = lower temp, alkalosis, hypocapnia, lower 2,3 DPG
Right (Bohr shift)= higher temp, acidosis, hypercapnia (high CO2), higher 2,3 DPG
Occurs during EXERCISE
What may cause a downwards or upwards shift of the oxygen dissociation curve
Downwards = anaemia (impairs oxygen carrying capacity)
Upwards = polycythaemia
What may cause a downwards and leftwards shift in the oxygen saturation curve
Carbon monoxide poisoning - decreased capacity, increased affinity for CO, reduced affinity for O2
What gas binding proteins shift the Oxygen dissociation curve to the left
Foetal Hb left, extracts O2 from mother’s blood in placenta
Myoglobin even more left, extracts O2 from circulating blood and store it
