Respiratory related content Flashcards
What is ventilation and perfusion?
-Ventilation (V) = the amount of air travelling into your alveoli ready for gas exchange
-Perfusion (Q) = the amount of blood flow travelling next to your alveoli ready for gas exchange
What is the average V:Q ratio?
0.8= there is more perfusion to the lungs then there is ventilation
Explain what the V:Q ratio is at the apex of the lungs and why?
-due to gravity, there is less perfusion at the top of the lungs
-this means there is wasted ventilation as the gas isn’t exchanged efficiently
-therefore V:Q ratio is higher at the apex
Explain what the V:Q ratio is at the base of the lungs and why?
-due to gravity, there is a high level of perfusion, but not as much ventilation at the base of the lungs
-this means there is wasted perfusion
-therefore V:Q ratio is lower at the base
What is a ventilation- perfusion mismatch?
-if a person has an obstruction in the air passages air is unable to get past to the alveoli so blood passing the alveoli doesn’t receive oxygen
OR
-areas of the lungs where there are circulatory issues preventing blood flow can be well oxygenated.
=ventilation: perfusion mismatch
Explain how different respiratory diseases may affect the ventilation: perfusion ratio
-pneumonia= decrease of ventilation therefore low V:Q ratio
-COPD= mucus thickening and build up along airways decreases ventilation therefore low V:Q ratio
-pulmonary oedema= fluid overload in lungs decreases ventilation therefore V:Q ratio decreases
-absolute physiological shunt= perfusion without any ventilation V:Q=0
-pulmonary embolism= clot occludes the pulmonary capillary or artery, perfusion is reduced so V:Q ratio increases
What is absolute dead space?
-when perfusion is zero to an area of the lungs
-gas still enters the alveoli but it does not participate in gas exchange
What is hypoxic drive theory?
states that giving COPD patients oxygen decreases their drive to breathe, thus raising carbon dioxide levels dangerously high, which can lead to death
What are the 3 factors that causes hypercarbia in COPD patients?
- hypoxic drive
- Haldane effect- haemoglobin can either hold a lot of O2 or CO2, not both
- V:Q mismatch
these 3 factors result in decreased respiration rate, altered level of consciousness, and coma/ death
What is the definition of a cough?
A short explosive expulsion of air
What chemical and mechanical things can initiate coughing?
Chemical:
-sensory nerve fibres e.g cytokines and histamine
Mechanical:
-foreign bodies
-growth cancer
How does a chemical or mechanical trigger lead to the body coughing?
- trigger stimulates sensory nerve fibres
- these travel through the vagus nerve which brings the information to the NTS in the medulla
- this causes a synapse with other neurons which trigger a cough reflex
- vagus nerve synapses with efferent nerve fibres, phrenic spine motor, recurrent laryngeal and vagus
- efferent nerve fibres bring the information to effector muscles which are the respiratory muscles, laryngeal muscles and bronchial smooth muscles
=cough reflex
What are the 3 main phases of a cough?
- inspiratory phase
-take a deep breath in it’ll stretch our expiratory muscles and we’ll increase the pressure within our lungs - compression phase
-our glottis closes (lung opening) but respiratory muscles contract which results in pressure increasing even more in the lungs - expiratory phase
-glottis opens and the air is pushed out because of the high pressure inside the lungs so we expel air out
What are the 6 different types of cough?
- barking= croup, habit
- honking= most likely psychogenic
- paroxysmal= sign of pertussis (whooping cough)
- productive= asthma
- wet= suppurative lung disease (produces phlegm or mucus)
- voluntary= volitional control sends signals to medulla to trigger cough response
What is the parietal and visceral pleura layer of the lungs?
Parietal= outer layer that attaches to chest wall
Visceral= inner layer that covers lungs, blood vessels, nerves and bronchi
What is a pleura membrane?
a sac that consists of a continuous serous membrane
What is pleuritis?
inflammation of the parietal pleura mainly due to infection
What is pleural effusion?
accumulation of fluid in the pleural, usually as a result of inflammation of the pleura
What is pneumothorax? and a tension pneumothorax?
-accumulation of air in the pleural space mechanism. can be spontaneous pneumothorax or open pneumothorax from trauma
-tension pneumothorax= over accumulation of air in the pleura usually as a result of a valve mechanism. air enters and can’t leave causing pleura pressure to build up, which is life threatening
What is empyema?
a collection of pus in the pleural cavity, usually associated with pneumonia
What is haemothorax?
a serious condition where blood collects in your pleural space
What is chylothorax?
the accumulation of chyle in the pleural cavity. this is the milky bodily fluid formed in the lacteal system of the intestine, which can result from trauma or surgical complications
What are the 5 stages of respiratory development and what structures develop at each stage?
- embryonic (3-6 weeks)= trachea, lung buds and R and L main bronchi
- Pseudoglandular (6-16)= bronchial tree to terminal bronchioles
=formation of major airways (organogenesis)
- canicular (16-26)= terminal bronchioles, type 1 and 2 pneumocytes.
Air blood barrier formed - saccular (26-36)= bronchioles, smooth walled sacculi
Surfactant detectable in amniotic fluid - alveolar (36-maturity)= alveoli
What happens in the transition to extra-uterine circulation?
-lungs open with first breath
-intra-pulmonary pressure fall
-gas exchange between alveolus and blood
-placental connection no longer needed
-foramen ovale, ductus arterioles and ductus venous able to close
Describe the foetal blood flow through the umbilical vein
-blood flows through from the placenta through the umbilical vein to the liver
-at the liver blood flow splits between the hepatic and portal system and the remained through the ductus venosus
Describe the foetal blood flow through the ductus venous
-blood flows through the ductus venous to the inferior vena cava then into the right ventricle
-in the right ventricle the blood flow divides between the foramen ovale and pulmonary artery
Describe the foetal blood flow through the foramen ovale
-blood flowing through the foramen ovale flows into the left atrium, joins a small amount of blood returning from the pulmonary veins, then passes through the mitral valve to the left ventricle and ascending aorta
Describe the foetal blood flow through the pulmonary artery
-blood flowing through the pulmonary artery passes through the ductus arterioles into the descending aorta
Why is the returning venous blood from the inferior and superior vena cava to the right ventricle streamed?
-better oxygenated blood from the umbilical vein to flow across the right atrium through the foramen ovale into the left atrium
-less saturated blood from the lower body via inferior vena cava, upper body via the superior vena cava, flows into right atria and ventricle
How does the foramen ovale respond to normal respiration?
-increased pulmonary blood flow returns to the heart into the left atrium
-an increase in the blood volume returning increases the pressure of blood entering the left atrium so the foramen ovale closes
How does the ductus arteriosus respond to normal respiration?
Ductus arteriosus closes as oxygen saturation incresaes and there is a reduction in blood flow due to vasodilation of the pulmonary vascular system.
How does the ductus venous respond to normal respiration?
Reduced pressure in the right atrium supports closure of the ductus venosus as blood doesn’t now need to bypass the liver. So the duct can close.
How does the umbilical vessels respond to normal respiration?
-Cord is clamped (placental blood flow stops)
-Clamping of the cord and disconnection of the placenta increases systemic vascular resistance (SVR). Halting the blood return from the placenta to the right atrium closes the ductus venous.
What are the differences in children’s respiratory system?
-infants under 6 months are obligatory nasal breathers, blockage of nasal passages can lead to respiratory distress
-large amounts of lymphoid tissue can obstruct the airway during periods of infection
-size of airway predisposes to increased airway resistance with any reduction in diameter
-epiglottis is longer and floppier in infants and positioned at a more acute angle making it less effective in occluding the airway
-in a full term infant lung volume doubles by 6 months of age and triples by 1
-trachea is shorter with more compliant cartilage, contributing to airway occlusion if the neck is hyperextended or flexed
-size of tongue relative to oral cavity
