Week 7- Ventilation and Gas Exchange Flashcards
What is a capacity?
The sum of two or more volumes
What is a volume?
Discrete sections of a lung function graph that dont overlap
What is minute ventilation and what is the formula for calculating it?
Gas entering and leaving the lungs
Tidal volume x breathing frequency
What is alveolar ventilation and what is the formula for calculating it?
Gas entering and leaving the alveoli
(Tidal volume - dead space) x breathing frequency
What is the usual minute ventilation?
6L/min
What is the usual alveolar ventilation?
4.2 L/min
What factors affect lung volumes and capacities?
Body size Fitness Age Disease Sex
What is the conducting zone?
Equivalent to dead space, no gas exchange occours, 16 generation
What is the respiratory zone?
Alveolar ventilation where gas exchange occours, around 7 generations
What are non perfused parenchyma?
Alveolar dead space- alveoli without a blood supply, no gas exchange
How can dead space volume be decreased?
Tracheostomy
Cricothyrocotomy
How can dead space volume be increased?
Aneasthetic circuit
Snorkelling
What membrane are the lungs surrounded by?
Visceral pleural membrane
What is the inner surface of the chest wall covered by?
Parietal pleural membrane
What is negative pressure breathing?
P alv is below P atm
What is positive pressure breathing?
P alv is above P atm
What type of breathing is normal breathing?
Negative pressure breathing
What is the gap between pleural membranes called?
The pleural cavity
Describe the pleural cavity
Has a fixed volume, contains protein rich pleural fluid
What is transmural pressure
Pressure inside membrane - pressure outside the membrane
What is Daltons law?
Pressure of a gas mixture is equal to the sum of the partial pressures of gases in that mixture
What is Ficks law?
Molecules diffuse from a region of high conc to low conc at a rate proportional to the conc gradient, exchange surface area, diffusion capacity of the gas and inversely proportional to the thickness of the exchange surface
What is Henrys 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 the gas in equilibrium with that liquid
What is Boyles law?
At a constant pressure, the volume of a gas is inversely proportional to the pressure of the gas
What is Charles’ law?
At a constant pressure the volume of a gas is proportional to the temperature of that gas
What happens to gas as it moves down the airways?
Air is warmed, humidified, slowed and mixed
What is oxygen delivery at rest?
16 mL/min
What resting volume of oxygen do humans require?
250 mL/min
Describe haemoglobin
Ferrous iron ion (fe2+)
Ion at center of a tetrapyrole porphyrin ring
Protein chain (globin) is covalently bonded at the proximal histamine residue
What type of protein is Hb?
Allosteric
What chemical helps Hb offload oxygen and how?
2,3 DPG, it makes Hb more tense
What triggers more oxygen offloading?
Increased temp
Acidosis
Hypercapnia
Increased 2,3- DPG
What triggers more oxygen loading?
Decreased temperature
Alkalosis
Hypocapnia
Less 2,3- DPG
What is the medical term for difficulty in breathing?
Dyspnoea
What is the medical term for cessation of breathing?
Apnoea
What is the medical term for an abnormally slow breathing rate?
Bradypnoea
What is the medical term for an abnormally fast breathing rate?
Tachypnoea
Define anatomical dead space
The capacity of airways incapable of undertaking gas exchange
What is hyperpnoea?
Increased depth of breathing to meet metabolic demand
What is hypopnoea?
Decreased depth of breathing insufficient of meeting metabolic demand
What is the medical name for positional difficulty in breathing?
Orthopnoea
What 2 volumes added together give inspiratory capacity?
Tidal volume and inspiratory reserve volume
What 3 volumes added together give vital capacity?
Inspiratory reserve volume
Tidal volume
Expiratory reserve volume
What 2 volumes added together give functional residual capacity?
Expiratory reserve volume
Residual volume
What 4 volumes added together give total lung capacity?
Inspiratory reserve volume
Tidal volume
Expiratory reserve volume
Residual volume
During inspiration is chest or lung recoil greater?
Chest recoil
During expiration is chest or lung recoil greater?
Lung recoil
What is pneumothorax?
Perforated chest wall
What does a negative transrespiratory pressure lead to?
Inspiration
What does a positive transmural pressure lead to?
Expiration
What does FEV1 resemble?
The proportion of vital capacity that is exhaled in the first second
Rank the gases from least to most abundant in air out of argon, oxygen, carbon dioxide, nitrogen
Carbon dioxide
Argon
Oxygen
Nitrogen
Describe oxygen binging to haemoglobin
The first O2 molecule has a low affinity to bind but as each O2 molecule binds affinity increases as the haemoglobin becomes more relaxed
What does a high heart rate with saturated arterial blood indicate?
An oxygen delivery problem
What is the Bohr shift?
A rightwards shift of the oxygen dissociation curve
Why may the oxygen dissociation curve shift downwards?
Due to impaired oxygen carrying capacity eg anaemia
What would a downwards and inwards shift of the oxygen dissociation curve suggest?
Decreased capacity and increased affinity eg increased HbCO
How do the affinities of foetal Hb and myoglobin to oxygen differ from normal haemoglobin
Both have a higher affinity
When RBCs reach the lungs how saturated are they?
75%
What do carbon dioxide and water combine to give in blood vessels?
Carbonic acid
In RBCs what enzyme helps form carbonic acid from carbon dioxide and water?
Carbonic anhydrase
When carbonic acid dissociates, what does the H+ help form?
Carboaminohaemoglobin
What is pulmonary transit time?
The time it takes for a molecule of Hb to cross the gas exchange surface
What effect does type 1 diabetes have on the oxygen dissociation curve and why?
Moves it to the right due to ketoacidosis (increased acidity)
What effect dies increased tidal volume have on the conc of oxygen dissolved in the blood?
Increases the conc of oxygen dissolved in the blood