Respiratory Flashcards
What is the path of air from trachea?
Trachea bifurcates at T4 - lobar bronchi - segmental bronchi - terminal bronchioles - respiratory bronchioles - alveolar ducts - alveolar sacs
What is the function of pleural fluid?
It allows optimal expansion and contraction of the lungs during breathing. It acts as a lubricant, reducing friction between the parietal and visceral layer.
What is the conducting zone of your respiratory tract?
From nasopharynx to terminal bronchioles
What is the respiratory zone of your respiratory tract?
From respiratory bronchioles to alveolar sacs
Where is the epithelium change in the respiratory tract?
It is respiratory epithelium up till the terminal bronchioles which are lined by simple cuboidal (to columnar) epithelium onwards.
Alveolar ducts are simple squamous epithelium
What is respiratory epithelium?
Pseudostratified ciliated columnar epithelium with goblet cells
What is boyle’s law?
At a fixed temperature, the volume of gas is inversely proportional to the pressure exerted by the gas.
P1V1 = P2V2
What are the pontine and medullary respiratory centres?
Pontine-
Pneumotaxic- smooths transition from inspiration to expiration (inhibits inspiration) –> Acts on VRG to cause expiration
Apneustic- Fine tunes inspiratory signals
Medullary centres-
Ventral respiratory group (VRG) - involved in both inspiratory and expiratory phases of breathing
Dorsal respiratory group (DRG) - mainly responsible for initiating and coordinating inspiration.
Where do the intercostal nerves arise from?
T1-T11
What are the 3 lung receptors?
Slow adapting stretch receptors, rapid adapting stretch receptors and J receptors
What are the slow adapting stretch receptors in the lungs?
Found in smooth muscles in the airway
They respond to distension.
When they are activated (during inspiration), they act to inhibit inspiration (transitioning to expiration) - Hering-Breuer reflex.
Myelinated
What are the rapid adapting stretch receptors (irritant receptors) in the lungs?
Found between the airway epithelium
They respond to irritants
By causing bronchoconstriction (can also cause cough reflex)
Myelinated
What are the J receptors of the lungs?
Located in the alveolar walls, in close proximity to the capillaries
Respond to increased lung interstitial pressure caused by fluid (pulmonary oedema) or alveolar hyperinflation –> they stimulate respiratory centres resulting in rapid and shallow breathing
Non-myelinated
How many more times does CO have an affinity for haemoglobin compared to oxygen?
200
What is V/Q mismatch?
V- ventilation
Q- Perfusion
This can cause hypoxia (oxygen deficiency in tissues)
Occurs when parts of the lungs receive oxygen but there is not enough blood to absorb it.
You can have alveoli that are ventilated- but not perfused (due to pulmonary embolism- a fragment of blood clot is lodged, blocking blood supply to the lungs, forms dead space)
OR
Alveoli that are perfused- but not ventilated (Pulmonary oedema) - blood will be shunted from places with no ventilation to alveoli with oxygen
What happens when dead space is created by a pulmonary embolism?
There will be local bronchoconstriction– to divert air to other sites which are better perfused.
What happens when pulmonary oedema occurs, resulting in alveoli that are perfused not being ventilated?
There will be hypoxic pulmonary vasoconstriction to divert blood to better ventilated areas
What is the bohr effect?
It describes hemoglobin’s lower affinity for oxygen secondary to increases in the partial pressure of CO2, decreased pH, increased temperature and increased 2,3 DPG
What causes the oxygen dissociation curve to shift to the right and what does this mean?
Increased temperature, decreased pH, increased PaCO2, increased 2,3 DPG
These factors decrease the affinity of hemoglobin for oxygen, causing more unloading/dissociation of oxygen into tissues thus leading to less hemoglobin saturation at the same Partial pressure of oxygen compared to normal circumstances.
What shifts the oxygen dissociation curve to the left?
Decreased temperature, increased pH, decreased PaCO2, decreased 2,3 DPG
What is the carbon dioxide distribution in the blood?
10% plasma
23% bound to haemoglobin
65% as bicarbonate (from dissociation equation, via carbonic anhydrase)
What is the normal pH range of the body?
7.35 - 7.45
What is the carbonic anhydrase equation?
H20 + CO2 – (with Carbonic anhydrase forms) H2CO3 – HCO3- + H+. REVERSIBLE REACTIONS
What is the formula for alveolar gas equation?
PAO2 = PiO2 - PaCO2/0.8
big A = alveolar
What is lung compliance and what is it determined by?
Compliance- how easily the lungs will expand
Determined by
Elasticity of lung tissue- increased elasticity, increased compliance
Surface tension (produced by type 2 pneumocytes) - increased surfactant decreases surface tension, increasing compliance
What is hypoxia and what are its causes?
Defined as inadequate oxygen delivery to tissues
Causes include
- Hypoventilation (increased PaCO2)
- Diffusion impairment - (due to thickening of membrane through which diffusion occurs)
- Shunting - perfusing unventilated alveoli
- V/Q mismatch
- Hypoxemia (decrease in partial pressure of oxygen in the blood)
SAME CAUSES AS TYPE 1 RESPIRATORY FAILURE
What is the main constitution of the respiratory drive?
What is the most common cause?
Hypercapnia - high levels of Co2 (high PaCO2)
Hypoventilation is the main cause
Differences between type 1 and type 2 respiratory failure
Type 1 - Low PaO2 and low/normal PaCO2
Type 2- Low PaO2 and high PaCO2
Type 1- The respiratory system is unable to provide an adequate supply of oxygen to the body leading to hypoxemia (pulmonary oedema, pneumonia COPD, asthma, ARDS)
Type 2- The respiratory system is unable to remove sufficient carbon dioxide from the body leading to hypercapnia - impaired ventilation(COPD, severe asthma
Type 1 - Typically caused by V/Q mismatch, shunting, diffusion impairment
Type 2- Typically caused by inadequate alveolar ventilation due to respiratory muscle weakness
Type 1- treatment focuses on improving oxygenation
Type 2- treatment focuses on improving ventilation
Causes of Type 2 respiratory failure
Increased airway resistance
Respiratory muscle weakness
Reduced breathing effort (obesity)
Excess workload
Decrease in area of lung available for gas exchange (chronic bronchitis)
What is FEV1. What is it usually in relation to FVC?
It is the volume of air you can forcibly expire in the first second. FEV1 is About 75-80% of FVC
What is peak expiratory flow?
The maximal flow of air as it is expired with maximum effort after maximum inspiration
What is the difference between airway obstruction and airway restriction?
Obstruction- Flow abnormality, limitation of airflow in and out of the lungs
Restriction- Problem with the volume, a decrease in total volume of air the lungs are able to hold
Obstruction- FEV1/FVC is less than 0.7 (indicates blockage somewhere)
Restriction- FVC is less than 0.8
Obstruction- COPD, Asthma
Restriction- Pulmonary fibrosis
What is the total lung capacity? Definition and volume
The total volume of air the lungs can hold.
5 litres
What is the Inspiratory reserve volume? Definition and volume
Inspiratory reserve volume (IRV)- The amount of air that can be forcibly/maximally inhaled after a normal tidal volume. (used during deep breathing) normal adult value is 2000ml
What is the expiratory reserve volume? Definition and volume
Expiratory reserve volume (ERV)- The amount of air that can be forcibly/maximally exhaled after a normal tidal volume (1250ml) → Reduced with obesity.
What is tidal volume? Definition and volume
Tidal volume (TV)- The amount of air that can be inhaled or exhaled in one respiratory cycle. 500ml
What is residual volume? Definition and volume
Residual volume(RV)- Volume of air remaining in the lungs after forced exhalation. Average 1250ml
What is vital capacity? Definition and volume
Vital capacity(VC)- The amount of air exhaled with maximum effort after maximum inspiration.(ERV+TV+IRV)- assesses strength of thoracic muscles and pulmonary function
3750ml
What is inspiratory capacity? Definition and volume
Inspiratory capacity(IC)- The maximum volume of air that can be inhaled following a normal tidal expiration. Tidal volume + Inspiratory reserve volume
2500ml
What is functional residual capacity? Definition and volume
Function residual capacity(FRC)- Volume of air in the lungs at the end of normal tidal expiration. (bottom of tidal volume)- RV+ERV
2500ml
Qualities of an ageing lung
Decreased compliance due to decreased lung elasticity
Delayed hypercapnea/hypoxia response
Increased V/Q mismatch
Decreased immunity response
Decreased FEV1/FVC ratio
What are the key mediators in innate immunity? Describe them a little
Neutrophils- inflammatory mediators produced in bone marrows
70% of all white blood cells
Macrophages (smaller proportion)
What is the process of innate immunity?
1) When a threat is identified, neutrophils are recruited
2) They are activated by cytokines and adhere at the site of infection (chemotaxis)
3) Phagocytosis and bacterial killing
What is the process of adaptive immunity?
T cells are involved in direct pathogen killing
Cytotoxic T cells (CD-8) - involved in pathogen killing
Helper T cells (CD-4)- induce other cell activation (macrophages, B cells)
B cells differentiate into plasma cells which secrete antibodies. A small proportion develop into memory cells which provide long lasting immunisation.
What are the most common immunoglobuilins?
GAMED
G- IgG - most abundant - bacterial and viral infections
A- IgA- Secreted in breast milk and mucosa (defends mucosal surfaces)
M- IgM- The FIRST antibody produced in response to a foreign pathogen
E- IgE- Antibodies produced in response to allergies
D- IgD- B cell activation
What are the non immune barriers of host defence in the lungs?
Respiratory epithelium- acts as a barrier and goblet cells produce mucus
Mucus- provides lubrication and protection via the mucocilliary escalator
Cough reflex- (During inspiration, epiglottis and vocal cords close, abdominal muscles contract and internal intercostals contract to increase intrathoracic pressure for expulsion of air)
What are the immune barriers of host defence in the lungs?
Alveolar macrophages - 93% of all macrophages in the lung
Phagocytose swiftly.
If pathogen attack is too strong, they respond by recruiting neutrophils. - causes inflammatory response
What are hypersensitive reactions?
An exaggerated immune response to an antigen which would not normally trigger an immune response
Type 1 hypersensitivity
Antibody- IgE mediated
Timing- Immediate (within an hour)
Causes- inflammatory response
Examples- ANAPHYLAXIS, hayfever
- Occurs when an individual is sensitised to a specific allergen. Upon re-exposure to the allergen, IgE antibodies are produced, triggering the release of histamine (from mast cells)
Type 2 hypersensitivity
Antibody- IgM, IgG,
CYTOTOXIC response
Timing - Hours to days
Examples- Goodpasture syndrome
- categorised by the binding of IgM or IgG to antigens on the surface of target cells. It triggers an immune response that results in the destruction of the cell via the complement system. (opsonization, inflammation, phagocytosis, lysis)
- Body can also make antibodies that attack host cells (lungs, kidneys, etc)
Type 3 hypersensitivity
Antibody- IgG
(antigen-antibody complex) IMMUNE COMPLEX FORMATION
Timing- 7-21 days
Examples- farmer’s lung, malt worker’s lung
Immune complex activates complement system (may release oxygen free radicals)
Type 2 involves - membrane bound antigens
Type 3- soluble antigens
but both involve complement system
Type 4 hypersensitivity
T cells
Timing- Days to weeks
DELAYED RESPONSE
Examples- tuberculosis
Upon exposure to the antigen, sensitised T cells release cytokines which activate immune cells such as macrophages. Delayed hypersensitvity
What are the neurotransmitters and receptors involved in parasympathetic stimulus to the bronchioles? What does this cause?
Parasympathetic stimulation via vagus nerve causes bronchoconstriction
At the ganglion, acetylcholine acts on N2 receptors at the target organ,
Ach acts on M3 receptors on smooth muscle (cardiac muscle, glands)
What are the neurotransmitters and receptors involved in sympathetic stimulation to the bronchioles? What does this cause?
Sympathetic stimulation via the sympathetic chain causes bronchodilation
At the ganglion, acetylcholine acts on N2 receptors, at the target organ,
Noradrenaline on b2 receptors on smooth muscle (cardiac muscle, glands)
What are the neurotransmitters and receptors involved in somatic stimulation of skeletal muscles?
Acetylcholine acts directly on N1 receptors on the target organ (skeletal muscles)
What is the atmospheric pressure in kilopascals at sea level?
100 kpa
How to calculate pressure of inspired gas?
Calculate it when altitude is 0m
Pressure of inspired gas = atmospheric pressure (kpa) x fraction of inspired gas
So the pressure of inspired oxygen at 1 atmosphere= 100 Kpa x 0.21 (natural air contains 20-21% oxygen) = 21 Kpa at sea level
Pressure of inspired gas = atmospheric pressure x fraction of inspired gas
How does increasing elevation affect this?
Fraction of inspired gas stays the same (0.21-natural air 21% oxygen)
Pressure of inspired oxygen falls
What is the normal physiological response to an increase in elevation?
Hypoxia → leads to hyperventilation → which increases minute ventilation → causing a decrease in PaCO2 → Initial alkalosis (excess base or acid caused by low level of carbon dioxide in the blood) pH rises → Tachycardia is a result of hyperventilation
Acute mountain sickness- needs to descend
What is decompression sickness?
When a diver ascends too rapidly, tiny bubbles of nitrogen form in the tissues.
1 atmosphere is equivalent to how many bars, millibars, metres of sea water, psi?
1 atmosphere = 1 bar = 1000 millibars =101 kpa =14 psi = 10m of sea water
For every 10m that you dive, how much does the pressure increase?
A 46 year old diver, spent 3 hours diving, using a 30% oxygen system at 130m of depth. What is the pressure of oxygen they were breathing?
1 atmosphere
Pressure of inspired oxygen= 0.3 (percent of oxygen) x 14 (14 atmospheres)= 4.2 atmospheres of oxygen
Where does the trachea start and end?
C6 - T4/5
What is an acinus of the alveoli?
A functional unit running out from the terminal bronchiole that is supplied with air by one terminal bronchiole.
What is dead space? What kind of dead space is there and how much volume is it?
Dead space- Refers to the volume of air that does not participate in gas exchange/ventilation. (it includes the air in the nose, pharynx, trachea and bronchioles)
Anatomic dead space (mentioned above) has approx 150ml and the alveolar dead space has about 25ml (as not every set of alveoli that receive gas are perfused with blood) so in the lungs, there is a total of 175ml of dead space not contributing to ventilation (physiological dead space-total dead space).
What is the most common mutation in cystic fibrosis?
Delta F508
CFTR gene
Laplace’s law
The tension in the wall of a structure is directly proportional to the pressure inside the structure and its radius. (increased pulmonary surfactant, reduces surface tension. Decreased radius reduces surface tension- as it increases surfactant concentration)
P= 2T/r
