RESPIRATORY PHYSIOLOGY Flashcards
how does pressure gradient alter during inhalation and exhalation?
- inhalation: lung volume increase –> pressure inside lung decrease –> pressure outside greater than inside –> air rushes into lungs
- exhalation: opposite to above
what is intrapulmonary pressure?
pressure inside the lungs
what are the 2 opposing forces that must be overcome to take a breath?
- stiffness of the lungs
- resistance of the airways to the lungs
what does it mean by saying stiff lungs? example?
- stiff lung = lung with low compliance –> need more work to expand the lungs
- pulmonary fibrosis
what causes stiff lungs?
- thickening and scarring of the alveolar membranes
- can arise from chronic inflammation or exposure to industrial chemicals
- lack of surfactant
what is surface tension at the lungs?
- tendency of a fluid surface to occupy the smallest possible surface area
- must overcome surface tension at the lungs to expand it
what causes surface tension at the lungs?
- alveoli are lined with fluid that exert surface tension
- walls of alveoli are very thin –> enhancing the effect of surface tension
what is surfactant? what does surfactant do to the lungs? how does it work?
- surfactant, produced by type II pneumocytes with major constituents is phospholipid
- surfactant helps lungs expand easier by lower surface tension
how does surfactant lower the surface tension?
reduces attractive forces between fluid molecules lining alveoli
what is airway resistance through the respiratory tract?
exert force (friction) on air when air move from outside to the alveoli
where is most of the resistance to airflow arise in?
bronchi
the _____1______ airways like terminal and respiratory bronchioles contribute very little to _____2_______ due to _______3_______ ________4________
1: small
2: airway resistance
3: high
4: cross sectional area
what is the compliance equation?
compliance = difference in V/difference in P
what is used to measures volume inspired/exhale and determine how big a breath you can take?
spirometer
what is tidal volume?
volume of air move in and out during normal quiet breath
what is inspiratory reserve volume?
extra volume that can be inhaled over and above the tidal volume
what is expiratory reserve volume?
extra volume that can be exhaled voluntarily after completion of a normal, quiet respiratory cycle
what is residual volume?
volume remaining in lungs after maximal exhalation
what is minimal volume
volume remaining in lungs if they collapsed
what is vital capacity, what made up vital capacity?
- volume of air that can be move in an out of your lungs
- inspiratory reserve + tidal + expiratory reserve
what is total lung capacity and what made up it?
- total volume in lungs when it is filled to max
- vital capacity + residual volume
what is inspiratory capacity and what made up it?
- total volume of air that can be inspired from rest
- tidal + inspiratory reserve
what is functional residual capacity and what made up it?
- volume remaining in lungs after normal exhalation
- residual + expiratory reserve
what is FEV1 in spirometry trace?
forced expiratory volume in 1 second
what is FVC in spirometry trace?
forced vital capacity
what is a normal number for FEV1/FVC ratio
80% (<0.7 indicates airways obstruction –> increase airway resistance)
what is obstructive lung disease?
- narrowing/obstruction of airway which increase airway resistance
- asthma, chronic bronchitis, emphysema (COPD)
what is restrictive lung disease?
- reduced the ability to expand the lungs due to reduced lung compliance (fibrosis) or insufficient surfactant release
what does PEF mean? what does a low PEF indicates?
- PEF = peak expiratory flow
- low PEF indicates obstructive lungs disease
what is an inhaled bronchodilator and what does it use for?
- helps relax the smooth muscle in airway
- used to determine if any airway narrowing is reversible such as in asthma or not reversible such as with chronic obstructive pulmonary disorder (COPD)
what does low PEF after inhaled bronchodilator indicates?
COPD
what is dead space mean in respiratory?
some of the inhaled air never gets to the alveoli so cannot gas exchange
equation for respiratory minute volume?
Ve = Vt x f
- Ve = respiratory minute volume (L/min)
- Vt = tidal volume (L/breath)
- f = respiratory rate (breaths/min)
why is alveolar ventilation important?
because it show the true amount of air that gets into the alveoli
alveolar ventilation equation?
Va = (Vt - Vd) x f
state Dalton’s Law, what does that mean?
- in a gas mixture (air in this case), each gas exerts its own individual pressure called a partial pressure
- the pressure of a mixture of gas = the sum of the pressures of each individual gas
what are the 2 forms of oxygen transport in blood?
- dissolve in plasma
- bind with RBCs
state Fick’s Law of Diffusion
gases move across the membranes between the alveoli and the capillaries by diffusion
what determines the rate of diffusion?
- surface area of the membrane
- thickness of the membrane
- pressure difference between the 2 sides
Fick’s Law of Diffusion equation?
F = (A/T) x D x (P1 - P2)
- F = amount flowing
- A= surface area
- T = thickness
- D = diffusion constant
- P1 - P2 = pressure difference
what does diffusion constant depend on?
- gas solubility and its molecular weight
- e.g. CO2 diffuse about 20x faster than O2 due to higher solubility of CO2
what is emphysema?
- a disease characterised by dilation of the alveolar spaces and destruction of the alveolar walls
- example of a COPD
- since the surface area is reduced, there is less contact between air and capillaries –> the flow is greatly reduced
to ensure an effective gas exchange, the distance between alveolar air and blood is _______________
very small
how does pulmonary fibrosis affect gas exchange?
- thickening and scarring of the alveolar membranes –> increase thickness –> decrease flux
in the P1 - P2 in Fick’s Law equation, what does P1 indicate and what does P2 indicate?
P1 = pressure alveolar (PA)
P2 = pressure arterial (Pa)
what does PAO2 depends on?
- partial pressure of oxygen in inspired air
- alveolar ventilation
- oxygen consumption - blood oxygen
what happens to oxygen in venous blood during rest and exercise?
- rest - low activity –> reduced oxygen consumption –> higher level of oxygen in venous blood
- exercise = high activity –> increase oxygen consumption –> lower level of oxygen in venous blood
how does the amount of oxygen in venous blood during exercise assist the gas exchange?
body extract more O2 from blood –> when blood came back to lung and contact alveoli, PAO2 much greater than PaO2 –> much greater P difference –> greater flux –> draw more O2
PACO2 depends on?
- partial pressure of CO2 in inspired air
- alveolar ventilation
- carbon dioxide production
what does oxygen-haemoglobin curve show?
the percentage of haem unit bound with oxygen
in the oxygen-haemoglobin saturation curve, what is y-axis and what is x-axis?
y-axis = oxyhaemoglobin (%saturation)
x-axis = PO2 (mmHg)
what is the shape of the oxy-haemoglobin curve?
sigmoidal
what is the value for PO2 and %oxy-saturation for blood entering systemic, blood leaving peripheral tissues, in active muscle and in partial pressure
- blood entering systemic: 98% saturated and around 100mmHg
- blood leaving peripheral tissues: 75% saturated and 40 mmHg
- in active muscle tissue: 20% saturated and below 20mmHg
- partial pressure where O2 is 50% saturated
why is the the upper part of the sigmoidal curve is flat?
buffer/safety zone where we can tolerate a dramatic reduction of partial pressure before haemoglobin begins desaturated
why can we observe a steep part of the curve at lower PO2
helps with loading of Hb in lungs and unloading of O2 to the tissues
_____1______ changes in PO2 result in ____2______ changes in amount of O2 bound to haemoglobin
1: small
2: large
what does Bohr effect mean?
the shifting of the binding curve
what cause left shift of the binding curve?
- O2 decreased affinity for haemoglobin
- lower plasma pH
- higher temperature
- increased in PCO2 (because increase in CO2 means increase in H+ means reduce pH)
- increase in BPG (2,3-biphosphoglycerate)
what is BPG and what does it do?
RBC glycolysis by-product that shift the oxygen-haemoglobin curve to the left
what cause right shift of the binding curve?
- O2 increased affinity for haemoglobin
- higher plasma pH
- decrease in temperature
- decrease in CO2
what does exercise cause to alter the binding curve?
exercise causes pH to drop and temperature to rise in skeletal muscle –> right shift
what are the 3 forms of CO2 transport?
- dissolved in plasma (7%)
- as bicarbonate HCO3- (70%)
- combined with proteins as carbamino compounds (23%)
how much CO2 diffuse into bloodstream?
93%
within the 93% CO2 diffused in the bloodstream, what 2 things can it do?
- 23% of this binds to haemoglobin as HbCO2
- the other 70% is converted to carbonic acid by the activity of enzyme carbonic anhydrase
is the formation of carbonic acid reversible?
yes
what happens to the carbonic acid once it is formed?
immediately dissociate into a hydrogen ion and a bicarbonate ion
what does the H+ from dissociated carbonic acid do?
bind to haemoglobin forming HbH+
what does the bicarbonate ion from dissociated carbonic acid do? what is the process called?
- move into plasma in exchange for chlorine
- chloride shift
where is our respiratory centre located? what are the 3 groups of neurons (from highest to lowest) here? what are the 3 groups referred to as?
- Medulla obloganta
- 3 groups: inspiratory center of the dorsal respiratory group (DRG), ventral respiratory group (VRG), and pre-botzinger complex
- respiratory rhythmicity centers
where does DRG and VRG send signals to?
- DRG: to diaphragm and external intercostal muscles
- VRG: to accessory respiratory muscles
what does the pre-botzinger complex do?
generates respiratory rhythm
briefly describe the control of breathing
sensors send afferent signals –> central controller (medulla) then medulla sends efferent signals to effectors (respiratory muscles)
–> form a cycle to maintain O2 and CO2 exchange at a ‘normal’ rate
central chemoreceptors are located in ____1_______, they are sensitive to _____2_____ but not to _____3_____ of blood and they respond to _______4_______
1: medulla
2: PCO2
3: PO2
4: pH change
peripheral chemoreceptors located in ____1____ and ______2______ bodies, they mainly respond to ____________3____________ and have a limited respond to ________4_____________, especially, they _______5______ responding
1: carotid
2: aortic
3: changes in arterial PO2
4: changes in PCO2
5: rapidly
which receptors are the most important in determining respiratory activity?
carbon dioxide receptors
as the lungs inflate/deflate, they send _______1______ from _______2_______, the brain then send _____3_______ preventing them from stretching too far away
receptors also detect _____4______ for brain to send ______3______ that triggers sneeze or cough
1: afferent input
2: stretch receptors
3: efferent output/signal
4: irritation
