Respiratory System Flashcards
How is the respiratory system organised?
The respiratory system can be divided into the upper and lower respiratory tract
The upper tract consists of the nose, pharynx and larynx
The lower tract consists of the trachea, bronchi, lungs and the alveoli
What is the fundamental role of the resp system in the body?
Our body is too large to rely on diffusion of gases from atmosphere to tissues to cope with metabolic demand.
The resp system maintains homeostasis of respiratory gases in the blood by moving O2 and CO2 between the atmosphere and blood at a sufficient rate.
How does oxygen get from the atmosphere to tissues? How does C02 get from tissues to the atmosphere?
O2 inhaled from atmosphere into alveoli within lungs
O2 diffuses from alveoli into blood within pulmonary capillaries.
O2 is transported in blood (>98% bound to haemoglobin)
O2 unbinds from Hb and diffuses into cells/tissues for use in aerobic respiration.
CO2 diffuses from respiring tissues into blood
CO2 diffuses from capillaries to alveoli, then expired into atmosphere.
State the meaning of VA:
Alveolar ventilation (VA): The amount of gas that reaches the alveoli and becomes involved in gas exch per min. VA=(Tidal Vol−Dead Space Vol)×Respiratory Rate
What is Pa02 and PaC02?
PaO2 = the alveolar partial pressure of oxygen in arterial blood. Also measures how well oxygen is able to move from the airspace of the lungs into the blood.
As Pa02 increases, ventilation increases
PaCO2 = the alveolar partial pressure of carbon dioxide in arterial blood. Also measures how well C02 can move out of the body.
As PaC02 increases ventilation decreases
What happens if ventilation is increased?
↑ventilation = ↑partial pressure gradient (between alveoli and blood) = ↑gas exchange
How can respiratory function be assessed clinically?
What is resp faliure?
Respiratory failure: The lungs inadequately oxygenate blood relative to the metabolic demands of the body (technical clinical definition ≈ ≤ 8kPa)
Inadequate 02 supply causes organ dysfunction/injury. Insufficient removal of CO2 leads to acidosis as it reacts with H2O to form carbonic acid.
Depending on T1/T2 failure, C02 removal from the body may or may not be affected.
Draw a table explaining T1 vs T2 resp failure. Include the Cause, PaO2, PaCO2 and Clinical examples
What is ventilation?
Ventilation is movement of air between the atmosphere & alveoli.
Ventilating the alveoli w fresh atmospheric air maintains the O2 & CO2 pressure gradients between alveoli & blood.
This is necessary for effective gas exchange.
What is Type 1 and 2 respiratory failure?
Type 1 resp failure is when hay a problem getting 02 from the alveoli into the blood
Type 2 resp failure is a ventilation problem which then causes reduced gas exchange
If ventilation rate is impaired, more CO2 is produced than expired by the body. O2 inspiration is insufficient relative to metabolic demand. CO2 accumulates and O2 levels fall, first in the alveoli, then in the blood.
How does asthma cause resp failure?
Asthma causes airways to constrict, affecting ventilation. Therefore asthma is a type 2 resp failure
If ventilation is inadequate, alveolar CO2 will increase. O2 will decrease, which then impacts on pressure gradients between alveoli and blood.
Por eso, hay reduced gas ex between alveoli & blood.
Describe Type 1 resp failure in a collapsed lung
The functional lung tissue post collapse increases su tidal vol and breathing Hz to bring ventilation back to normal.
The compensatory increase in ventilation is effective at eliminating excess CO2, BUT it’s much less effective at increasing blood oxygenation (resolving hypoxaemia)
Why can PaO2 sometimes be low but PaCO2 is normal (almost low) – how is this possible?
O2 transport relies on Hb, which has minimal extra 02 carrying capacity and is finite in each unit of blood.
This means effective diffusion of 02 between alveoli and blood requires good partial pressure gradient AND precise coupling of ventilation to perfusion.
In contrast, CO2 transport in the blood relies much less on Hb. CO2 diffusion from blood to alveoli is determined only by the partial pressure gradient. Therefore CO2 levels in the blood is only impacted by changes in ventilation. (T2 resp failure)
Outline some broad causes of respiratory failure
Insufficient ventilation: Obstruction of airways (e.g. choking, asthma, COPD), failure to breathe adequately (stroke, MND)
Insufficient gas exchange: Exchange surface dysfunction (pulmonary fibrosis thickens the boundary entre the alveoli and blood. This increases diff distance which decreases gas ex) VQ mismatch (when part of your lung receives 02 sin blood flow or blood flow sin 02 in eg atelectasis, pneumonia)
Insufficient oxygen carrying capacity(anaemia)
Insufficient oxygen in atmosphere (altitude)
