Ventilation And Gas Exchange Flashcards
How would you describe human lungs?
Normothermic ex-vivo ventilated perfused lungs
Define the following terms:
- Minute ventilation
- Respiratory rate (RF)
- Alveolar ventilation (Valv)
- Respiration
- Anatomical dead space
- Alveolar dead space
- Physiological dead space
- Minute ventilation - volume of air expired in one minute (VE) or per minute (VE italics)
- Respiratory rate (RF) - frequency of breathing per minute
- Alveolar ventilation (Valv) - volume of air reaching the respiratory zone per minute
- Respiration - the process of generating ATP either w an excess of oxygen (aerobic) and a shortfall (anaerobic)
- Anatomical dead space - the capacity of the airways incapable of undertaking dead space
- Alveolar dead space - capacity of the airways that should be able to undertake gas exchange but cannot
- Physiological dead space - equivalent to the sum of anatomical and alveolar dead space
Define the following terms:
- Hypoventilation
- Hyperventilation
- Hyperpnoea
- Hypopnoea
- Apnoea
- Dyspnoea
- Bradypnoea
- Tachypnoea
- Orthopnoea
- Hypoventilation - deficient ventilation of the lungs; unable to meet metabolic demand (increased PO2- acidosis)
- Hyperventilation - excessive ventilation of the lungs atop of metabolic demand (results in reduced PCO2 - alkalosis)
- Hyperpnoea - increased depth of breathing (to meet metabolic demand)
- Hypopnoea - decreased depth of breathing (inadequate fo meet metabolic demand)
- Apnoea - cessation of breathing (no air movement)
- Dyspnoea - difficult in breathing
- Bradypnoea - abnormally slow breathing rate
- Tachypnoea - abnormally fast breathing rate
- Orthopnoea - positional difficulty in breathing (when lying down)
Lung volumes and capacities:
What are the different categories on a lung volume over time graph and what do they mean
Light respiratory effort
Max inspiratory effort
Max expiratory effort
Tidal volume - Vol of air going in and out w each breath
Inspiratory reserve volume - extra volume of air you could get into the lungs
Expiratory reserve volume - getting towards empty when expire but can’t go all the way
Residual volume
Total lung capacity = adding all the vols together
Vital capacity = sum of all the vols you have access to
Functional residual capacity = everything below your default position
Volumes are discrete sections of the graph and don’t overlap
Capacities = sum or two or more volumes
Quantifying ventilation:
What is minute ventilation? How is it calculated, units?
What is alveolar ventilation? How is it calculated, units?
Minute ventilation (L/min) - gas entering and leaving the lungs:
Minute ventilation (L/min) = tidal volume (L) x breathing frequency (breaths/min) (6 L/min) (0.5 L) (12 breaths/min)
Alveolar ventilation - gas entering and leaving the alveoli
Alveolar ventilation (L/min) (4.2) = tidal volume (L) (0.5 L) - dead space (L) (0.15) x breathing frequency (breaths/min) (12)
List factors affecting lung volume & capacities
Body size (height, shape)
Sex (male, female)
Fitness (innate, training)
Age (chronological, physical)
Disease (pulmonary, neurological)
Dead space:
What is the conducting zone?
What is the respiratory zone?
What are the non-perfused parenchyma?
- how many generations
- gas exchange?
- how many mL in adults?
- other name?
Conducting zone: 16 generations No gas exchange Typically 150 mL in adults at FRC equivalent to anatomical dead space
Respiratory zone: 7 generations Gas exchange Typically 350 mL in adults Air reaching here is equivalent to alveolar ventilation
Non-perfused parenchyma: Alveoli without a blood supply No gas exchange Typically 0 mL in adults Called alveolar dead space
Adjusting dead space:
What are two reversible procedures that can:
Decrease someone’s dead space?
Increase someone’s dead space?
Increase dead space —> tracheostomy, cricothyrocotomy
Reduce dead space —> snorkelling, anaesthetic circuit
Chest wall relationship:
Which forces are in equilibrium at end tidal expiration/functional residual capacity (FRC)?
What is the relationship between inspiratory muscle effort, chest recoil and lung recoil?
What is the relationship between expiratory muscle effort, chest recoil and lung recoil?
Chest wall has tendency to spring outwards, lung has a tendency to recoil inwards
-> these forces are in equilibrium at end tidal expiration (functional residual capacity; FRC), which is the neutral position of the intact chest
At FRC:
Chest recoil = lung recoil
Inspiratory muscle effort + chest recoil > lung recoil
Chest recoil < lung recoil + expiratory muscle effort
Basic chest wall anatomy:
What membrane surrounds the lungs?
What is the inner surface of the chest covered by?
What is the pleural cavity? What does it contain?
What dictates the position, characteristics and behaviour of the intact chest wall?
Lungs are surrounded by a visceral pleural membrane
Inner surface of chest wall is covered by a parietal pleural membrane
Pleural cavity (the gap between pleural membranes) - fixed volume, contains protein rich pleural fluid
Chest wall and lungs each have distinct physical properties that together, dictate the position, characteristics and behaviour of the intact chest wall
Pleural cavity integrity:
What is a haemothorax?
What is a pneumothorax?
Intra pleural bleeding - haemothorax
Perforated chest wall / could also be caused by a punctured lung - pneumothorax
What drives the flow of air?
What are the two types of breathing? Define in terms of alveolar and atmospheric pressure. Give examples of each type of breathing
Pressure gradients drive flow
Air flows from high pressure to low pressure
Negative pressure breathing - Palv < Patm
Positive pressure breathing - Patm > Palv
Normal breathing = negative pressure breathing
Positive pressure breathing : mechanical ventilation, CPR, fighter pilots
Three compartment model:
What do the following stand for?
Patm Ppl Palv PTT PTP PRS
How do you calculate transmural pressures?
What leads to inspiration?
What leads to expiration?
What is the value for Patm?
How do you calculate PRS?
Patm - atmospheric pressure Ppl - intrapleural pressure Palv - alveolar pressure PTT - transthoracic pressure PTP - transpulmonary pressure PRS - transrespiratory system pressure
Transmural pressures = Pinside - Poutside
Negative transrespiratory pressure leads to inspiration
Positive transmural pressure leads to expiration
Patm = 0
PRS = Palv - Patm
Inspiratory muscle forces:
What can the effect of the diaphragm be compared to?
Describe the effect of the other respiratory muscles
Diaphragm: like a syringe. A pulling force in one direction
Other respiratory muscles: like a bucket handle. Upwards and outwards swinging force
Define the following key laws that describe gas behaviour:
Dalton
Fick
Dalton - pressure or a gas mixture is equal to the sum of the partial pressures (P) of gases in that mixture
P gas mixture = total P gas1 + total P gas2 + …. total P gas n
Fick - molecules diffuse from regions of high concentration to low concentration at a rate proportional the conc grad (P1 - P2), the exchange surface area (A) and the diffusion capacity (D) of the gas. And inversely proportional to the thickness of the exchange surface (T)
Vgas = A/T x D x [P1 - P2]
