Ventilation + Gas Exchange Flashcards
What is minute ventilation?
volume of air expired in 1 minute or per minute
What is respiratory rate?
frequency of breathing per minute
What is alveolar ventilation?
volume of air reaching the respiratory zone per minute
What is respiration?
process of generating ATP either with or without O2
What is anatomical dead space?
capacity of the airways incapable of undertaking gas exchange
What is alveolar dead space?
capacity of the airways that should be bale to undertake gas exchange but can’t
What is physiological dead space?
equivalent to the sum of anatomical + alveolar dead space
What is hypoventilation?
deficient ventilation of the lungs, unable to meet metabolic demands
What is hyperventilation?
excessive ventilation of the lungs atop of metabolic demands
What is hyperpnoea?
increased depth of breathing (to meet metabolic demand)
What is hypopnoea?
decreased depth of breathing (no air movement)
What is apnoea?
cessation of breathing (no air movement)
What is dyspnoea?
difficulty in breathing
What is bradypnoea?
abnormally slow breathing rate
What is tachypnoea?
abnormally fast breathing rate
What is orthopnoea?
positional difficulty in breathing (when lying down)
What is minute ventilation?
gas entering + leaving the lungs
What is alveolar ventilation?
gas entering + leaving the alveoli
How is minute ventilation calculated?
tidal volume (L) x breathing frequency (breaths/min)
What are the units of minute + alveolar ventilation?
L/min
How is alveolar ventilation calculated?
( tidal volume (L) - dead space (L) ) x breathing frequency (breaths/min)
What 5 factors affect lung volumes + capacities?
body size, fitness, sex, disease, age
What is tidal volume?
Normal inspiration + expiration
What is inspiratory reserve volume?
Inspiration above tidal volume
What is inspiratory capacity?
Inspiratory reserve volume + tidal volume
What is expiratory reserve volume?
Expiration below tidal volume
What is residual volume?
Lung volume left after expiration
What is functional residual capacity?
Expiratory reserve capacity + residual capacity
What is vital capacity?
Expiration after max inhalation
What is non-perfused parenchyma?
- Alveoli without a blood supply
- No gas exchange
- Typically 0 mL in adults
- Called alveolar dead space
What is the respiratory zone?
- 7 generations
- Gas exchange
- Typically 350 mL in adults
- Air reaching here is equivalent to alveolar ventilation
What is the conducting zone?
- 16 generations
- No gas exchange
- Typically 150 mL in adults at FRC
- Equivalent to anatomical dead space
What zone is equivalent to anatomical dead space?
conducting zone
What zone is equivalent alveolar ventilation?
respiratory zone
What zone is equivalent alveolar dead space?
non-perfused parenchyma
How can you reversibly decrease dead space?
- Tracheostomy
* Cricothyrocotomy
How can you reversibly increase dead space?
- Anaesthetic
* Circuit snorkelling
What is the chest wall’s main tendency?
tendency to spring outward
What is the lung tissue’s main tendency?
tendency to recoil inwards
When are chest wall and lung tissue forces in equilibrium?
end-tidal expiration or functional residual capacity (FRC) - the neutral position of the chest
When does inspiration of the lungs + chest occur?
inspiratory muscle effort + chest recoil > lung recoil
When does expiration of the lungs + chest occur?
Expiratory muscle effort + lung recoil > chest recoil
What membrane are the lungs surrounded by?
visceral pleural membrane
What is the inner surface of the chest wall covered in?
parietal pleural membrane
What is the pleural cavity?
the gap between the pleural membranes
What does the pleural cavity contain?
protein-rich pleural fluid + fixed volume
What is the haemothorax?
accumulation of blood within the pleural cavity
What is the pneumothorax?
presence of air or gas in the pleural cavity - causes collapse of lung
What can cause pneumothorax?
perforated chest wall, punctured lung
What can cause haemothorax?
intrapleural bleeding
What drives flow of air in + out of lungs in terms of pressure?
pressure gradients
What is negative pressure breathing?
alveolar pressure reduced below atmospheric pressure
What is positive pressure breathing?
atmospheric pressure increased above alveolar pressure
What is an example of negative pressure breathing?
normal breathing
What are 3 examples of positive pressure breathing?
- mechanical ventilation
- CPR
- fighter pilots
What are transmural pressure?
pressure difference between the inside and outside of the lungs
What is the result of negative transrespiratory pressure?
inspiration
What is the result of positive transrespiratory pressure?
expiration
What kind of force does the diaphragm have?
pulling force in one direction
What kind of force does the other respiratory muscles have?
upwards + outwards swinging force
What is spirometry?
common test to assess lungs - measures how much air is inhaled + exhaled and how quickly
What does P stand for?
partial pressure (kPa or mmHg)
What does F stand for?
fraction (%)
What does S stand for?
Hb saturation (%)
What does C stand for?
content (mL)
What does Hb stand for?
Volume bound to Hb (mL)
What does I stand for?
inspired
What does E stand for?
expired
What does A stand for?
alveolar
What does a stand for?
arterial
What does v stand for?
mixed venous
What does P stand for?
peripheral
What does D stand for?
dissolved
What is the Dalton law?
pressure of a gas mixture = sum (Σ) of partial pressures(P) of gases in that mixture
What is the Fick law?
molecules diffuse from rhigh conc to low conc at a rate proportional to the
concentration gradient (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)
or
Vgas = (A/T)D(P1-P2)
What is Henry’s law?
at a constant temp, the amount of a given gas that dissolves in a given type and volume of
liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid
What is Boyle’s law?
at constant temp, volume of gas is inversely proportional to pressure of gas
What is Charles’ law?
at a constant pressure, volume of gas is proportional to temp of gas
What 4 processes happen to air as it passes down the respiratory tract?
- warmed
- humidified
- slowed
- mixed
What is total O2 delivery at reast?
16 mL/min
What is the resting volume of O2?
250 mL/min
What problems does the difference in total O2 delivery and resting volume of O2 cause?
body can’t rely on dissolved oxygen alone - therefore body needs more effective transport mechanism
What is the structure of haemoglobin monomers?
tetrapyyrole porphyrin ring w/ ferrous iron ion in the centre covalently bonded at the proximal histamine residue to a protein chain
What happens when oxygen binds to one of Hb’s 4 binding sites?
the affinity to oxygen for the remaining available binding sites increases
What is cooperative binding?
when one of the binding sites is full, the affinity at the others increases
Why is Hb an allosteric protein?
binding of oxygen to Hb causes a conformational change in the protein structure
Why is Hb’s cooperative binding useful?
- in oxygen-rich areas = higher oxygen affinity = more oxygen loading
- in oxygen-starved areas = lower oxygen affinity = more oxygen unloading
What does an oxygen-dissociation curve look like?
sigmoidal curve
x-axis = oxygen partial pressure
y-axis = oxygen saturation
What does a leftward shift in the oxygen-dissociation curve mean?
INCREASED affinity • Lower temperature • Alkalosis • Hypocapnia ( ↓ CO2 ) • Decreased 2,3-DPG
What does a rightward shift in the oxygen-dissociation curve mean?
DECREASED affinity • Higher temperature • Acidosis (Bohr effect) • Hypercapnia ( ↑ CO2 ) • Increased 2,3-DPG
What does a downward shift in the oxygen-dissociation curve mean?
DECREASED oxygen carrying capacity
• Anaemia
What does a upward shift in the oxygen-dissociation curve mean?
INCREASED oxygen carrying capacity
• Polycythaemia
What is the difference between HbA and HbF in terms of O2 affinity?
HbF has greater affinity for O2 to extract oxygen from mothers blood in placenta
What is the difference between HbA and myoglobin in terms of O2 affinity?
myoglobin has higher affinity than HbA to extract oxygen from circulating blood + store it
What makes gas exchange in the lungs so efficient?
- alveoli have high SA:V ratio
- alveoli covered in high density of capillaries
- walls of alveoli are v thin
- covered in fluid extra-cellular matrix that provides surface for gas exchange
- partial pressure gradients allow for loading of O2 + unloading of CO2
