resp physiology Flashcards
What is the residual volume
A volume of gas always present in the body to keep the alveoli partially inflated so they are partially stretched which makes them easier to fill - the volume of gas in the lungs at the end of a maximal expiration
What is the vital capacity
the maximum capacity of air that can be voluntarily moved
What is dead space volume
The air sitting in the upper respiratory conducting airways - not viable for gas exchange
What is the tidal volume
The volume of air breathed in and out of the lungs every breath
What is the expiratory reserve volume
The maximum volume of air which can be expelled from the lungs at the end of a normal expiration
What is the inspiratory reserve volume
The maximum amount of air which can be drawn into the lungs at the end of a normal inspiration
What is the vital capacity
Tidal volume + inspiratory reserve volume + expiratory reserve volume
What is the total lung capacity
Vital capacity + the residual volume
What is the inspiratory capacity
Tidal volume + inspiratory reserve volume
What is the functional residual capacity
Expiratory reserve volume + residual volume
What is FEV1
Forced expiratory volume in one second
What is FVC
Forced vital capacity - forced expiratory volume in one breath
What is the parietal pleura attached to
The rib cage
What is the visceral pleura attached to
The lungs
What is the function of the pleural fluid
It allows the two membranes to glide across each other while preventing them from separating
What are the muscles of inspiration
Diaphragm
External intercostals
Sternocleidomastoid
Scalene
What are the muscles of expiration
Internal intercostals
Abdominal muscles
Expiration is a passive process but if we want to force expiration, these muscles are used
Describe breathing with regards to the diaphragm during inspiration
The diaphragm contracts which pushes it down and increases the thoracic volume which therefore reduces the pressure
Describe expiration with regards to the diaphragm
The diaphragm relaxes which pushes it up, therefore decreasing the volume of the thoracic cavity
What nerve innervates the motor function of the diaphragm
The phrenic nerve
What way do the external intercostal muscle fibres run
as you go proximally the fibres run inferiorly
Imagine putting hands into pockets
What way do internal intercostal muscle fibres run
As you go proximally, the fibres run superiorly
What is the intra-thoracic (alveolar) pressure
Pressure inside thoracic cavity - essentially in lungs
What is the intra-pleural plessure
Pressure inside the pleural cavity - usually negative compared to the atmospheric pressure
What is the transpulmonary pressure
Difference between alveolar pressure and intra-pleural pressure - usually positive since the intra-pleural pressure is negative
What is the function of type 1 alveolar cells
Gas exchange
What is the function of type II alveolar cells
Produces surfactant
What is the function of surfactant
Reduces surface tension on the alveolar surface membrane which reduces the risk for alveoli collapsing
Explain surface tension with regards to alveoli
The air needs to be in solution before it can leave the alveoli - the water droplets are attracted to other droplets outside the alveoli which creates a force around the alveoli which can cause it to collapse - surfactants block this effect by getting between the water droplets
What is a high compliance in the lungs
Large increase in lung volume for small change in intra-pleural pressure
What is pulmonary ventilation
Total air movement in or out of the lungs
What is alveolar ventilation
Fresh air getting to alveoli which means that it is available for gas exchange
How to calculate Pulmonary ventilation
Tidal volume x resp rate
How to calculate alveolar ventilation
(Tidal volume - dead space) x resp rate
Why are alveoli at the vase of the lung better for ventilation
The alveoli at the base are crushed by the weight of the lung and more compressed which means that they can expand more
What is the normal alveolar partial pressure of oxygen and CO2
O2 - 100mmHg
CO2 - 40mmHg
What is the function of the pulmonary artery
Carries deoxygenated blood away from the heart to the lungs
What is the function of the pulmonary vein
Carries oxygenated blood towards the heart from the lungs
Why are type 1 alveolar cells good for gas exchange
They have a large surface are and a thin membrane which allows for a short diffusion distance
What happens to the partial pressure O2 in emphysema
Emphysema - destruction of alveoli which reduces surface area for gas exchange so the blood does not get O2 from the alveoli so the partial pressure O2 decreases
Why does fibrotic lung disease reduce PO2 in the blood
The alveolar membrane is thickened which slows gas exchange
Why does pulmonary oedema decrease the partial pressure O2 in blood
Oxygen is not very water soluble and the increased fluid makes a further diffusion distance which slows gas exchange
What is the partial pressure of O2 in asthma
It is low in the alveoli and therefore low in the blood due to less oxygen being able to be taken into the alveoi
What is ventilation
The amount of air getting to the alveoli
What is perfusion
The local blood flow to tissues
Where is the blood flow higher than ventilation within the lung
The base of the lung because the arterial pressure exceeds alveolar pressure - this leads to the alveoli being compressed
What is the trend with blood flow and ventilation as you go from the base to the apex
Both decline but blood flow declines faster than ventilation meaning that the blood flow is higher than ventilation at the base and ventilation is higher than blood flow at the apex
What happens when there is decreased PO2 in tissues around an under ventilated alveoli
The arterioles constrict causing blood to go to other better ventilated alveoli
What do peripheral chemoreceptors monitor
Decreases in PO2
What do central chemoreceptors monitor
Increase in PCO2
What is a shunt
Passage of blood through areas of lung that are poorly ventilated
What is alveolar dead space
Alveoli that are ventilated but not perfused
What is anatomical dead space
Air in the conducting zone that is unable to take part in gas exchange
How is oxygen transported around the body
Either dissolved in plasma or bound to haemoglobin in red blood cells
Is oxygen mainly transported in plasma or bound to haemoglobin
Water is not very soluble so the majority of oxygen travels bound to haemoglobin
How is the majority of CO2 transported in the body
In solution in plasma and less is transported bound to haemoglobin
How much of the arterial O2 is extracted by peripheral tissues at rest
25%
How many oxygen molecules does each haemoglobin bind
4
What determines how saturated the haemoglobin is with oxygen
The partial pressure of Oxygen in the alveoli and therefore in plasma
How does the oxygen bind to the haemoglobin
The oxygen essentially sequesters oxygen from the plasma which therefore continuously gathers oxygen from the alveoli
How much of our haemoglobin is saturated during normal PO2 and also at venous PO2
nearly fully saturated (97/98)% at normal PO2
75% saturated at venous PO2
What is anaemia
Any condition where the oxygen carrying capacity of blood is compromised
What happens to the partial pressure O2 in anaemia
Nothing - the amount of oxygen decreases but the PO2 is normal
What causes oxygen to be perfused to the tissues off the haemoglobin
When there is low haemoglobin affinity for oxygen
What is the affect of PH on oxygen haemoglobin affinity
More oxygen affinity for haemoglobin when PH increases
What is the effect of PCO2 on haemoglobin oxygen affinity
If PCO2 increases, acidity increases which therefore causes the PH to increase and increase the affinity
What is the effect of temperature on oxygen haemoglobin affinity
Lower temperature increases affinity
What is the affect of DPG on oxygen haemoglobin affinity
It reduces the affinity - it is an allosteric enzyme which reduces the affinity between oxygen and haemoglobin
What are the symptoms of someone who has carboxyhaemoglobin formation - Carbon monoxide binding with haemoglobin
hypoxia, anaemia, nausea, headache , Cherry red skin and mucous membranes
Treat with 100% O2
What are the types of hypoxia
M - metabolic hypoxia
A - anaemic hypoxia
S - stagnant hypoxia
H - histotoxic hypoxia
H - hypoxaemic hypoxia
What nerves control the muscles of inspiration
Phrenic - diaphragm
intercostal nerves - external intercostal muscles
Where are the respiratory centres in the brain
Pons and the medulla
What are the central chemoreceptors
Medulla
What are the peripheral chemoreceptors
Carotid and aortic bodies
What do central chemoreceptors in the brain detect
Changes in protons in the CSF around the brain and then increase ventilation if too many protons to get rid of carbon dioxide
What happens to people with chronic lung disease who have a chronically elevated PCO2
They become desensitised to PCO2 do rely on PO2 and the peripheral chemoreceptors
What happens to respiration during swallowing
Respiration is inhibited to prevent food or fluids getting into the airway and swallowing is followed by an expiration to dislodge any particles that may have made their way to the respiratory system
