Ventilation and gas exchange Flashcards
What is minute ventilation?
The volume of air expired in one minute
What is respiratory rate?
The frequency of breathing per minute.
What is alveolar ventilation?
The volume of air reaching the respiratory zone per minute
what is anatomical dead space?
The capacity of the airways incapable of undertaking gas exchange
What is alveolar dead space?
The capacity of the airways that should be able to undertake gas exchange but cannot (Hypoperfused alveoli).
What is physiological dead space?
Equivalent to the sum of alveolar and anatomical dead space
What is hypoventilation?
Deficient ventilation the lungs, unable to meet metabolic demands (Increased PCO2) - acidosis
What is hyperventilation?
Excessive ventilation of lungs atop of metabolic demand (reduced PCO2) - alkalosis
What is hyperpnoea?
Increased depth of breathing to meet metabolic demand
What is hypopnea?
Decreased depth of breathing (inadequate to meet metabolic demand)
What is apnoea?
Cessation of breathing
What is dyspnoea?
Difficulty in breathing
What is bradypnoea?
Abnormally small breathing rate
What is tachypnoea?
Abnormally fast breathing rate
What is orthopnea?
Position difficulty in breathing (when lying down)
What does respiratory volume mean?
Term used to describe the volume of air moved by or associated with the lungs at a given point within the respiratory cycle
What does tidal volume mean?
Volume of air that occupies the lungs during periods of quiet breathing (500ml)
What does expiratory reserve volume mean (ERV)?
Volume of air that can forcefully be exhaled succeeding normal tidal expiration
What is inspiratory reserve volume?
Produced from deep inhalation, past tidal inspiration. This is the additional volume that is drawn into the lungs through forced inspiration.
What is residual volume?
The volume of air present in lungs upon maximum exhalation. The residual asset with breathing ability by preventing alveoli collapse
What is respiratory capacity?
Combination of 2+ selected volumes
What is total lung capacity?
Sum of all lung volumes (TV, ERV, IRV, and RV), represents the total amount of air that can occupy the lungs upon a forceful inhalation
What is the inspiratory capacity (IV)?
Tidal volume + inspiratory reserve volume
Maximum amount of air that can be inhaled past a normal tidal expiration
What is functional residual capacity?
Amount of air that remains in the lung after normal tidal expiration
FRC = Residual volume + expiratory reserve volume
What is vital capacity?
The amount of air that can be moved into or out of the lungs.
Sum of TV, ERV & IRV
What is the calculation to calculate minute ventilation?
tidal volume x breathing frequency
What is the calculator for alveolar ventilation?
[Tidal volume - dead space] x breathing frequency
What forms the anatomical dead space within the trachea and bronchioles?
The C-shaped cartilaginous rings within the conducting zone do not participate in gas exchange
What is dead space?
The respiratory system also contains anatomical dead space Air is present in the air away however does not reach the alveoli or participate in gas exchange.
How many generations are present within the superficial conducting zone?
16 generations; no gas exchange
150ml at FRC
How many generations form the respiratory zone?
7 generations
What volume of air reaches the respiratory zone?
350ml
What forms the alveolar dead space?
Non-perfused parenchyma - avascular alveoli therefore unable to conduct gas exchange considering that oxygen cannot be transferred to pulmonary circulation
How can dead space be increased? [example]
Anaesthetic circuit snorkelling
How can dead space be decreased? [Example]
Removal of conducting zone structures including: Tracheostomy, cricothyrotomy - interject further down for upper pharynx blockage
What surrounds the lung?
Pleural cavity
What type of membrane forms the pleura?
Serous membrane
What separates the two lungs from each other?
Mediastinum
What two layers form the pleura?
Visceral and parietal pleura
What is the outer layer of pleura?
Parietal pleura
What is the function of parietal pleura terms of connections?
Outer layer connects to the thoracic wall, the mediastinum and the diaphragm
Where do the visceral and parietal pleura connect?
They connect at the hilum
What is the space between the visceral and parietal layers?
Pleural cavity
What membrane surrounds the lungs?
pleural membrane
What is within the pleural cavity?
A foxed volume, and contains protein rich pleural fluid
The chest wall has a tendency to spring___?
Outwards
The lungs has a tendency to recoil____?
Inwards
What forces are in equilibrium at end-tidal expiration (Functional residual capacity)
Chest recoil = lung recoil
What forces result in inspiration in terms of chest recoil and muscles?
inspiratory muscle effort + chest recoil > lung recoil
What forces result in expiration in terms of lung recoil and muscles?
Lung recoil + expiratory muscle effort > chest recoil
Which cells secrete pleural fluid?
Mesothelial cells from both pleural layers
What is the function of pleural fluid?
Lubricates their surfaces to prevent trauma during breathing, surface tension to maintain position of lungs abasing thoracic wall
What is the purpose of adhesive pleural fluid?
Enables the lung to enlarge when the thoracic wall expands during ventilation, allows air filling
Why does the lung collapse I pneumothorax?
The partial vacuum within the pleural cavity is loss, the respiratory musculature is dysfunctional, therefore there is air lost to the thoracic chest, building pressure on the lung.
What does Boyles Law state?
At a constant temperature, the relationship of pressure is inversely proportional to the volume occupied. Therefore, as volume increases the pressure exerted by the same of gas molecules decreases
What unit of measurement expresses atmospheric pressure?
atm or mmHg
What does negative pressure in reference to atm?
Lower than atmospheric pressure
What is the value of pressure that is equal to atmospheric pressure?
Zero
What is intra-alveolar pressure?
The pressure of air within the alveoli - changes during phases of breathing.
Why does the interpulmonary pressure equalises with atmospheric pressure?
The alveoli are connected to the atmosphere through the tracheal system
What is inter pleural pressure?
The presence of air within the pleural cavity between the visceral and parietal pleurae - negative to the intra-alveolar pressure
What is the pressure relationship between inter-pleural pressure and intra-alveolar pressure?
Negative to intra-alveolar pressure.
What generates the inward pull of the lung tissues away from the thoracic wall?
Elastic tissue pulls the lung inwards away from the thoracic wall
What causes inwards alveolar pull?
Alveolar surfactant cohesive forces
How is the inward pull counteracted within the lung and pleura?
The opposing forces from the pleural fluid and thoracic wall
Surface tension within the pleural cavity = outward
What is transpulmonary pressure?
The difference between intrapleural and intra-alveolar pressure
What is transmural pressure?
Pressure inside - pressure outside
How does negative trans-respiratory pressure cause inspiration?
Negative trans-respiratory pressure will result in inspiration considering that the generated pressure potential favours the direction most negative (Atmospheric pressure > Intrapleural)
What is negative pressure breathing?
Alveolar pressure decreases below atmospheric pressure
What is positive pressure breathing?
Patm is increased above Palv (CPR, intrathoracic ventilation)
What is PTT (transthoracic pressure)?
(𝑷𝒑𝒍 −𝒑𝒂𝒕𝒎)
What is transpulmonary pressure (PTP)?
Transpulmonary pressure (𝑷𝒂𝒍𝒗 −𝑷𝒑𝒍)
What is trans-respiratory system pressure?
Trans-respiratory system pressure (𝑷𝒂𝒍𝒗 −𝑷𝒂𝒕𝒎)
What is the forced expiratory volume (FEV1)?
Forced expiratory volume in the first second. The volume of air that is expelled from the lungs within one second. Parameters are dependent on height, gender & age.
How is the FEV1 affected with conditions of obstruct disorders?
Considering there is an obstruction to airflow, this reduces the rate of air being transmitted across the bronchioles and expired
What is the forced vital capacity (FVC)?
Forced vital capacity (FVC): The volume of air that can forcibly be expelled from the lungs after complete inspiration, measured in litres.
In obstructive disorders how is the FEV1/FVC ratio affected?
In obstructive diseases (Asthma, COPD, chronic, chronic bronchitis, emphysema), FEV1 is diminished due to increased airways resistance to expiratory flow. FVC is minimally reduced, therefore the FEV1 is significantly effected resulting in a a reduced ratio.
What is Dalton’s law?
Pressure of a gas mixture is equal to the sum of the partial pressures of gas in that mixture
What is Fick’s law?
Molecules diffuse from regions of high concentrations to low concentrations at a rate proportional to the concentration gradient., the exchange surface, and the diffusion capacity of the gas, and inversely proportion to the thickness of exchange surface
What is Henry’s law?
At a constant temperature, the amount of a given gas that dissolves in a given type and volume is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
What is Charles’s law?
At a constant pressure, the volume of a gas is proportional to the temperature of that gas
Despite a high partial pressure of nitrogen gas, why is the dissolving capacity low?
Low solubility of gas
What is the purpose of humidification of air?
Causing the air present in the alveoli to have a greater volume of water vapour than atmospheric air (Alveolar air cantinas greater proportion of carbon dioxide and less oxygen in comparison to atmospheric air)
Slowed, and mixed as it passes downtime respiratory tree
Which iron is located at the centre of the tetrapyrrole porphyrin ring?
Ferrous Fe2+
How many oxygen molecules can bind to one haemoglobin molecule?
4
How does haemoglobin increase oxygen affinity binding?
Cooperative binding
Haemoglobin increase their affinity to oxygen through conformational change of beta & alpha chains within the quaternary structure, this thus increases the receptive affinity to oxygen by exposing their binding site
Which molecule binds to the centre of haemoglobin to cause oxygen unloading?
2,3-DPG
What type of protein is haemoglobin?
Haemoglobin is an allosteric protein
What does an allosteric protein mean?
Has multiple ligand binding sites, the binding of a ligand affects ability at another site. The allosteric behaviour results in cooperativity
What does cooperativity mean?
Oxygen binding increases oxygen binding ability
What relationship does an oxygen-haemoglobin dissociate curve demonstrate?
Demonstrates the relationship of partial pressure to the binding of oxygen to haem, and it subsequent dissociation
As the partial pressure of oxygen increases, a proportionately greater number of molecules are bound to haem, explain this in terms of affinity?
The affinity of anoxyegen molecule for haem increases as more oxygen molecules are bound
How are low partial pressure environments maintained ?
Highly active tissues e.g muscles increase rate of oxygen consumption to produce ATP - lowering the PPo2. Greater PPo2 within capillaries so more dissociation of o2 from Hb.
Why is there fewer oxygen dissociation within adipose tissue?
Lower metabolic rate, therefore the partial pressure of oxygen is higher
What device is used to measure oxygen saturation?
Pulse oximetry
How does temperature affect the oxygen dissociation curve?
Right shift
Promotes haemoglobin and oxygen to dissociate faster (lower temperature inhibits this dissociation)
How does pH cause the Bohr effect?
The Bohr effect describes the relationship between pH and oxygen affinity. Acidosis (increased carbon dioxide release - increased carbonic acid – hydrogen ions)< acids may occur due to lactic formation thus increasing the need for oxygen unloading to oxidase and satisfy metabolic demands
How does 2,3 DPG influence oxygen dissociation occurs?
Increased 2,3DPG causes grater unloading of oxygen
What chemical pathway produces 2,3 DPG?
Glycolysis
Which four main hormones causes an increase in 2,3 DPG?
Androgens
Adrenaline
Thyroid hormones
growth hormones
How does polycythaemia alter the oxygen-dissociation curve?
Increased oxygen carrying capacity
Causes upwards shift
How does anaemia alter the oxygen dissociation curve?
Impaired oxygen carrying capacity causing a downwards shift
How does carbon monoxide alter the oxygen-distribution curve?
Downwards and leftwards shift
Increases HbCO
Why does CO decreased oxygen carrying capacity?
Carbon monoxide occupies the asme binding site as oxygen behaving as a competitive inhibitor, increasing the affinity for CO rather than oxygen , shifts the maximum saturation
What structure supplies foetal blood ?
Umbilical cord
How is the affinity to oxygen affected for foeal haemoglobin?
Greater affinity for oxygen than maternal haemoglobin
What is the purpose of myoglobin?
Has a greater affinity than adult HbA in order to extract oxygen from circulating blood and storing it within muscle cells (Releasing it at significantly lower pressures, as an oxygen reserve).
What is the oxygen saturation of mixed venous blood?
75%
Why is there a relatively high oxygen saturation in mixed venous blood? (75%)
oxygen is not required during periods of low demand,
How does oxygen diffuse into the interstitial space?
Thus, oxygen diffuses into the interstitial space through into the capillaries, binding onto associated haem groups within erythrocytes, cooperatively.
What is oxygen flux?
The amount of oxygen delivered to peripheral tissue per minute.
Which ions enter into erythrocytes during bicarbonate ion exchange?
Chloride ions
What transport facilitates chloride shift?
AE1 transporter
How is the majority of carbon dioxide transported in the blood?
Transported as bicarbonate
What are the three main ways of carbon dioxide transport?
Bicarbonate
carboaminohaemoglobin
dissolved in plasma
How is carbon dioxide transport in RBCs dependent on oxygen?
Dependent on amount of oxygen bound to haem group, there is allosteric behaviour, gas behaviour changes depending on type and amount of molecule bound.
What is pulmonary transit time?
The amount of time it takes for a molecule to cross the gaseous exchange surface (0.75s), oxygen can equilibrate within length of time.
What affect does increasing cardiac output have on pulmonary transit time?
Decreases pulmonary transit time, improves ability to increase oxygen saturation of haemoglobin , oxygen loading is faster
