respiratory physiology Flashcards
functions of the respiratory system
gaseous exchange that is the alveoli
acid base balance that is the pH in conjunction with the kidney.
communication via speech
protection from infection that is through the lymphoid tissue in the region , as well as the cilia and the mucus in the trachea.
pulmonary circulation
circulation from the heart to the lungs and the lungs to the heart which is mediated by the pulmonary artery and the pulmonary vein.
what is the importance of gaseous exchange
to provide the body with oxygen that is necessary for respiration
to remove excess by product that is carbon dioxide which is harmful to the body ; alters the bodies pH .
what is external respiration
movement of gases along /across respiratory surfaces
between the air and the body`s cells.
pulmonary circulation
it delivers CO2 (to the lungs) and collects O2 (from the lungs)
systemic circulation
systemic circulation delivers O2 to peripheral tissues and collects CO2.
systemic circulation
delivers O2 to peripheral tissues from the heart and collects CO2 from the peripheral tissues to the heart
integration of the cardiovascular system and the respiratory systems
respiratory system is solely for exchange of gases that is oxygen and carbon-dioxide while cardiovascular system is for the transportation of the nutrients and the oxygen to other regions of the body
volume of gases exchanged in the lungs
250 ml/min of oxygen
200 ml/min of carbon-dioxide
normal respiration rate
12-18 breaths per minute
upper respiratory tract
everything above the larynx
lower respiratory tract
trachea , downwards
what is meant by patency of the airway
the airway is open
this is facilitated by semi-rigid tubes, “patency” of airway is maintained by C-shaped rings of cartilage.
compare the width of the bronchi
right bronchi is vertical almost the same width as the trachea
left bronchi is horizontal at an angle with the trachea .
resistance to the flow of air
-resistance is because of the number of particles ( air molecules )
-therefore the resistance is higher in the conducting zone than it is in the non - conducting zone.
increased diameter leads to increased resistance and the vv is true
elastic fibers
small fibers that help to contract the alveoli
type 1 alveoli
gaseous exchange
type 2 alveoli
production of surfactant
what is the anatomical dead space
the space where there is purely conduction of air and no gaseous exchange hence the space is not used in the calculation of the volume of air
total lung volume
6L
tidal volume
total inspiration and expiration volume at each breath
residual volume
the volume of the gas that remains in the lungs at the end of the expiration
expiratory reserve volume
maximum volume of air which can be expelled from the lungs at the end of the normal expiration
inspiratory reserve volume
maximum volume of air which can be drawn into the lungs at the end of normal inspiration
relationship of the pleural membrane
the lungs are stuck with the rib cage through the parietal pleural and to the lungs with the visceral pleura leaving the space for pleural fluid
the visceral pleural sac
surrounds the lungs
parietal pleural sac
outer surrounding of the pleural
pleural cavity
space between the visceral and the parietal pleura
intrapleural pressure
always negative and helps to maintain the recoil between the two that is the lungs and the ribs
muscles of inspiration
external intercostal muscles
diaphragm
boyle`s law application
increase in volume causes a decrease in pressure
volume changes during inspiration
increase in volume ; pressure in the thoracic cavity decreases
volume changes during expiration
decrease in the volume ;pressure increases
expiration muscles used
1.passive expiration is not reliant on any muscles
2.forced expiration uses internal intercostal muscles and abdominal muscles
movement of the thoracic cavity during inspiration
the inferior thoracic aperture increases since the ribcage is moved upwards
the rib cage moves outwards increasing the lateral distance
diaphragm muscle during inspiration
contraction , flattens and moves downwards
intra -pleural pressure
pressure that is inside the pleural cavity and is negative compared to atmospheric pressure ( less than the atmospheric pressure )
intra - thoracic pressure
pressure in the alveoli ;depends on the atmospheric pressure ; maybe negative or positive during inspiration or during expiration
transpulmonary pressure
difference of the alveolar pressure and the intra -pleural pressure
alveolar pressure during inspiration
negative ( lower) than the atmospheric pressure
pressure of air during expiration
positive ( more ) than the atmospheric pressure
pneumothorax
disruption of the pressure of the plural sac in relation to the atmospheric pressure.
pneumothorax
entry of the air in the pleural cavity ; which leads to the recoil of the lung during expiration ;
the lungs pull towards the mediastinal region ; they detach from the ribs
surfactant
reduces surface tension in the alveoli reducing the chances of the alveoli from collapsing
surfactant is more effective in small alveoli than large alveoli
production of surfactant
25 weeks after gestation and is complete by 36 weeks
it is stimulated by thyroid hormones and cortisol which increase full-term towards pregnancy.
saline filled lung equivalent
Less change in pressure required to inflate lung as do not need to overcome surface tension (no air-water interface)
what is compliance of a lung
Definition: change in volume relative to change in pressure
i.e. how much does volume change for any given change in pressure
It represents the stretchability of the lungs (not the elasticity
highly compliant lung
large increase in lung volume for small decrease in ip pressure
normal pulmonary values
6000ml/min
to increase pulmonary respiration
the tidal volume is increased
partial pressure
Dalton’s Law states that the total pressure of a gas mixture is the sum of the pressures of the individual gases.
partial pressure of oxygen
pressure exerted by the oxygen molecules present in the total air mixture.
Atmospheric Pressure = 760mmHg
Pressure of air we breathe therefore = 760mmHg
21% of air we breath = O2
Partial pressure of O2 in air we breath = 21% x 760mmHg
hyperventilation
increased alveolar ventilation ( rising up to 120 mmHg )
hypoventilation
decreased hypoventilation ( decreased alveolar ventilation ) the Po2 falls to 30mmHg and PCO2 rises to 100mmHg .
pressure -volume distribution of ventilation
alveolar ventilation is higher at the base than at the apex
at the base the volume change is greater for a given change in pressure.
compliance of the lung at the apex and at the base
Compliance is lower at the apex due to being more inflated at FRC. At the base the lungs are slightly compressed by the diaphragm hence more compliant on inspiration.
changes in the intrapleural pressure brings a larger change in the volume at the base compared with the apex
blood is supplied to the lungs for ventilation by
pulmonary artery
blood that is oxygen rich is removed from the lungs by
pulmonary vein
nutritive blood supply to the lung tissue
bronchial circulation - supplied by the bronchial arteries that originate from the systemic circulation to supply oxygenated blood
gas exchange circulation
pulmonary circulation
abbreviation A
alveolar
abbreviation a
arterial blood
abbreviation v
venous blood
gas exchange in lungs
through diffusion
solubility of different gases in the blood
oxygen in not very soluble while carbon dioxide is very soluble
factors that affect the rate of diffusion
partial pressure gradient
gas solubility
available surface area
thickness of the membrane
distance to be travelled
partial pressure in the alveoli
100 for oxygen
40 for carbon dioxide
systemic arterial blood
fibrosis
there is a thickened membrane that is brought about by deposits of fibre
there is reduced compliance as it is hard to inflate the alveoli
partial pressure of oxygen in the alveoli and the artery is reduced
to an extent there is reduced ventilation ( that is during inspiration )
emphysema
destruction of the alveoli which leads to reduced surface area
so the partial pressure of oxygen is the same in the alveoli and low in the blood vessel
because of this there is loss of elastic recoil therefore expiration is quite hard
asthma
alveolar partial pressure is low because of increased resistance
obstructive disease
diseases that obstruct the flow of air during expiration example COPD, asthma and emphysema .
restrictive lung disorders
diseases that lead to the restriction of lung expansion there is inevitable air that reaches the lungs ; there is ultimate loss of lung compliance
fibrosis
oedema
pneumothorax
infant respiratory distress syndrome
spirometry
technique used to measure lung function and it measures static and dynamic lung function.
what is static measurement in spirometry
consideration of the volume that is exhaled
what is dynamic measurement
time taken to exhale a certain volume
lung volumes that can be measured by spirometry
tidal volume
expiratory reserve volume
vital capacity
inspiratory capacity
inspiratory reserve volume
forced expiratory volume in one second
4l in a healthy male adult
forced vital capacity
5L in a normal healthy male adult
FEV1/FEV
80%
FEV1/FEV of obstructive lung disease
The rate at which the air is forcefully expelled is low however the forced vital capacity may be reduced but not to a large extent as FEV1
the ratio is also reduced
FEV1/FVC of restrictive diseases
the expiratory volume reduces
the total volume also decreases as there is reduced inspiration
the overall ratio remains unchanged or goes up
therefore spirometry is not a really accurate method for determination of the restrictive diseases.
spirometry in disease
Obstructive: both FEV and FVC fall but FEV more so, so ratio is reduced.
Restrictive: both FEV and FVC fall so ratio remains normal, or may even increase, despite severe compromise of function.
Therefore normal FEV1/FVC ratio not always indicative of health!
pressure - volume relationship and compliance why are the inspiratory and expiratory curves not able to be superimposed ?
Overcome lung inertia during inspiration
Overcome surface tension during inspiration
During expiration compression of the airways means more pressure is required for air to flow along them.
work in respiration
normally expiration is passive does not require effort only require elastic recoil
-in emphysema there is loss of elastic tissue which means expiration will require effort
-in fibrosis the fibrous tissue means there is further increased effort for inspiration.
distribution of blood flow in the lungs
blood flow is highest at the bottom of the lung
blood flow is lowest at the apex of the lung because the alveolar pressure is greater than the rate of blood flow the blood vessels are compressed .
blood flow across different heights of the lungs
both blood flow and ventilation decrease with height across the lung
mismatch in ventilation and perfusion
Perfectly matched Ventilation:Perfusion ratio = 1.0
Mismatch 1 (base) Ventilation<Perfusion < 1.0 Mismatch 2 (apex) Ventilation>Perfusion ratio > 1.0
consequences of the ventilation - perfusion relationship at the base of the lung
blood flow is greater than perfusion of blood
because the blood flow is higher the pCO2 in the alveoli increases and the pO2 in the alveoli decreases the blood in the affected alveoli is diverted to another alveoli .
the blood flowing in the pulmonary artery has increased carbon dioxide levels and it mixes with other blood vessels this is known as a shunt system.
consequences of ventilation perfusion relationship at the apex of the lung
at the apex of the lung there is more ventilation than there is perfusion so there will be excess oxygen in the alveoli , this will result in an alveoli dead space
local control of ventilation and perfusion mismatch
in the case of a shunt ( hypoxic conditions ) there is vasoconstriction of the pulmonary vessels while the systemic will dilate
and bronchial dilation
pathological presentation of alveolar dead space
pulmonary embolism
autoregulation of increased ventilation and less perfusion
pO2 is increased - pulmonary vasodilation
pCO2 is decreased - bronchoconstriction
what is a shunt
Shunt is a term used to describe the passage of blood through areas of the lung that are poorly ventilated (ventilation «_space;perfusion).
alveolar dead space
Alveolar Dead Space refers to alveoli that are ventilated but not perfused.
physiological dead space
Alveolar DS + Anatomical DS
respiratory sinus arrhythmia
RSA ensures ventilation:perfusion ratio remains close to 1 (matched)
activation of the vagus nerve (parasympathetic )
during expiration there is increased vagal activity and vice versa
transportation of oxygen in the blood
3% on the plasma
97% by the red blood cells
saturation of haemoglobin
98% saturation
transport of carbondioxide
as hb bound in the red blood cells
as carbonic acid in the red blood cells
as plasma solution
amount of gas that is transported by the blood at a given minute
200 ml of oxygen and 250 of carbondioxide
amount of oxygen that is extracted by the peripheral tissues at rest
25% of the oxygen hence the systemic venous circulation (deoxygenated) is only 75% of oxygen
red blood cell and haemoglobin
haemoglobin has 2 alpha and 2 beta units
with each containing a haem group and a central iron
4 oxygen molecules can be transported at a time
release of one oxygen molecule leads to a conformational change in the molecule such that the haemoglobin will have less affinity for the other oxygen molecules
movement of oxygen after diffusion
moves to the plasma then diffuses to the red blood cells
time taken for saturation of the haemoglobin
Saturation is complete after 0.25s contact with alveoli (total contact time ~0.75s)
oxygen - haemoglobin dissociation curve
haemoglobin is 98 % bound to oxygen
changes in the partial pressure to a large extent do not lead to a reduction in the binding of the oxygen to haemoglobin
at normal venous pO2 which is 40 there is still haemoglobin saturation of 75%
What would happen to PO2 in anaemia?
Nothing!
PO2 is normal despite total blood O2 content being low
Possible to have normal plasma PO2, while total blood O2 content is low.
Not Possible to have normal plasma PO2, while total blood O2 content is low.
is it possible for red blood cells to be fully saturated with O2 in anaemia?
YES! Red blood cells would still be fully saturated with oxygen as PO2 is normal
(only caveat is iron deficiency where number of O2 binding sites will be reduced, but those present will still be saturated)
factors that cause changes in the affinity of oxygen
pH
PCO2
Temp
DPG
factors that alter the dissociation curve
The affinity of haemoglobin for oxygen is decreased by a decrease in pH, or and increase in PCO2, or temperature. These conditions exist locally in actively metabolising tissues and facilitate the dissociation of oxygen from haemoglobin.
Conversely a rise in pH or a fall in PCO2, or temperature increases the affinity of haemoglobin for oxygen. These conditions make oxygen unloading more difficult but aid collection of oxygen in the pulmonary circulation.
The affinity of haemoglobin for oxygen is decreased by binding 2,3-diphosphoglycerate (2,3-DPG) synthesised by the erythrocytes. 2,3- DPG increases in situations associated with inadequate oxygen supply (heart or lung disease, living at high altitude) and helps maintain oxygen release in the tissues.
carbon monoxide binding with haemoglobin
CO binds to haemoglobin to form carboxyhaemoglobin with an affinity 250 times greater than O2 - binds readily and dissociates very slowly so very problematic once dissolved in circulation.
clinical presentations of carbon monoxide
Characterised by hypoxia, anaemia, nausea, headache, cherry red skin and mucous membranes. Respiration rate unaffected due to normal arterial PCO2. Potential brain damage and death.
treatment of carbon monoxide
treatment involves providing 100% oxygen to increase PaO2
transport of carbon dioxide
When CO2 molecules diffuse from the tissues into the blood, 7% remains dissolved in plasma and erythrocytes,
23% combines in the erythrocytes with deoxyhemoglobin to form carbamino compounds,
70% combines in the erythrocytes with water to form carbonic acid, which then dissociates to yield bicarbonate and H+ ions. Most of the bicarbonate then moves out of the erythrocytes into the plasma in exchange for Cl- ions & the excess H+ ions bind to deoxyhemoglobin. The reverse occurs in the pulmonary capillaries and CO2 moves down its concentration gradient from blood to alveoli.
arterial partial pressure and arterial oxygen content
arterial partial pressure
types of haemoglobin
92% haemoglobin in RBC is in the form HbA (below). Remaining 8% is made up of HbA2 (δ chains replace β), HbF (γ chains replace β), and glycosylated Hb (HbA1a, HbA1b, HbA1c)
myoglobin
myoglobin stores oxygen unlike haemoglobin
oxygen carrier molecule that has one polypeptide instead of 4 in haemoglobin
can also extract oxygen from other haemoglobin molecules
affinity for oxygen by the carrier molecules
bF and myoglobin have a higher affinity for O2 than HbA, this is necessary for extracting O2 from maternal/arterial blood.(the affinity for oxygen is higher in myoglobin then foetal haemoglobin then
affinity for oxygen by the carrier molecules
HbF and myoglobin have a higher affinity for O2 than HbA, this is necessary for extracting O2 from maternal/arterial blood.(the affinity for oxygen is higher in myoglobin then foetal haemoglobin then normal haemoglobin)
What muscles control ventilation
The diaphragm via the phrenic nerve
The external intercostal muscles via the intercostal nerves
Ventilation control in the brain
Through the pons and the medulla
What can cause stop of breathing
Severing the spinal cord above the origin that is c3-c5
Why is pulmonary circulation known as high flow low pressure system
This is because the blood that flows through the entire systemic system in one minute flows through the pulmonary circulation in one minute too , the low pressure is because the blood is at 25 mm Hg at rest while at 120 at rest in systemic circulation
