Respiratory System Flashcards
What is ventilation?
The movement of air through the airways
Which of the following species has the most pliable nares: Sheep, Dog, Pig, Horse?
Horse
What comprises the respiratory portion of the lung?
Respiratory bronchioles, alveolar ducts and sacs
When does gas exchange occur at the alveolus?
During the whole respiratory cycle
From which embryonic structure do the lungs develop ?
Foregut
Why do premature neonates often experience respirator distress after birth?
Not enough surfactants
Does increased airway diameter increase or reduce airway resistance?
Bronchodilation reduces airway resistance
What part of the respiratory system is least turbulent
Bronchiole
Where are peripheral chemoreceptors located?
Carotid and aortic sinuses
What do central chemoreceptors in the respiratory system detect changes in?
PaCO2
What is the pH range of mammals ECF?
7.35- 7.45
What happens to the acid:base balance with respiratory obstruction?
Respiratory acidosis
What might cause respiratory efficiency decrease during anaesthesia?
Drugs
Recumbancy
Equipment
How do drugs cause a decrease in respiratory efficiency?
Direct effect on medulla oblongata- reduces inputs to respiratory centre- chemoreceptors, irritant receptors
Why may recumbency be a problem duding anaesthetic respiration?
Lateral recumbancy- atelectasis of dependent lung
Dorsal recumbancy- abdominal contents compromise diaphragm
Build up of mucous
How does equipment effect respiration efficiency during anaesthesia?
Endotracheal tube, connectors, circuit, machine, monitors Increase dead space Increased resistance to airflow Potential rebreathing/inadequate O2 Air not humidified
What is the potential result of reduced respiratory efficiency during anaesthesia?
Va:q ration- the amount of air that reaches alveoli divided by the amount of blood flow in capillaries
High CO2/ Low O2
What are the consequences of deranged respiratory function?
Acidosis- respiratory increases H+, metabolic- anaerobic respiration increases lactic acid
Prolonged hypoxia- irreversible brain damage
Hypercapnia- vasodilation, raised intracranial pressure
How is respiration monitored during anaesthesia?
Pulse oximeter
Capnography
Arterial/venous blood gas measurements
Where is a pulse oximeter attached, how does it work, what does it measure?
Clipped on to a vascular non-pigmented area
Red and inferred light beamed through tissue and differential absorption measured
Measures O2 saturation of haemoglobin/pulse
At what PaO2 does the level of Hb saturation start to decline significantly in the normal animal?
Below 75%
What could effect the result of pule oximeter?
Vasoconstriction of the region measured
Abnormal haemoglobin
Equipment factors- movement, light
What does capnography measure?
Measure the concentration/pp of CO2 in expired air via the breathing system
What results does capnography produce?
Produces a curve
Gives a measurement of end-tidal CO2 (ETCo2)
What PCO2 would you expect in a normal animal?
40
What could cause raised ETCo2?
Inadequate ventilation
Increases metabolic rate
Increased cardiac output
Rebreathing of expired air
What is the gold standard for monitoring respiratory parameters?
Blood gas analysis
What does blood gas analysis measure and what kind od sample does it need?
Measure PO2 and PCo2 directly
Needs either arterial/venous sample
Can also measure- pH, HCO3-, lactate, electrolytes
What PaO2/PCO2 would you expect in an artery and venous samples?
Artery- PaO2- 100, Co2- 40
Vein- PaO2- 70-80, Co2- 45
When should respiratory monitoring stop after anaesthesia?
Once conscious
How are large particles prevented form entry to the respiratory tract?
Nares, nasal cavity, pharynx, larynx
How is inhaled air ‘cleaned’?
Hair and mucous lining the nasal cavity
What is the mucociliary escalator and what does it do?
Constantly moves secretions from submucosal glands and goblet cell cranially towards pharynx, then swallowed or expectorated
What size particles can reach the alveoli and how are they removed?
Under 5um
Phagocytosed by alveolar macrophages
What are the three types of airway receptors?
Rapidly adapting receptors
Slowly adapting receptors
C-fibres
Where are rapidly adapting receptors found, what do they respond to?
Intrapulmonary airways
Respond mainly to changes in airway mechanical properties
What causes RAR to become more active and what is their response?
More active as rate and volume of lung inflation increases during normal inspiration
Can cause bronchoconstriction and mucus secretion via parasympathetic pathways
Where are slowly adapting receptors found, what are they sensitive to, when does their activity increase?
Found- around bronchioles and alveoli
Sensitive- to mechanical forces
Activity increases during respiration, decreases during expiration
What are SARs the afferent fibres for?
Hering-breur reflex
What do C-fibres respond to ?
What activates them?
What does their stimulation cause?
Respond to noxious chemical and mechanical stimuli
Directly activates by bradykinin and capsaicin
Stimulation causes bronchoconstriction, mucus secretion, apnoea
What causes a cough reflex?
A mixture of all three receptor types
Where are the mixture of three receptors which cause the cough reflex found?
Throughout conduction airways
Concentrated at birfurcation of airways
How is a cough stimulated?
Stimulation of cough receptors
Impulses carried via values to cough centre in medulla oblongata and pons
Efferent to diaphragm (phrenic nerve), abdominal muscles/muscles of respiration, larynx
What are the three phases to a cough?
Inspiratory
Compression phase
Expiratory
What happens during the compression phase?
Laynx closes, muscles (abdominal, diaphragm, intercostal) contract, intrathoracic pressure rises
What does the nature of a cough depend on?
Where the stimulus occurs
Where are receptors found which cause a sneeze?
Nasal mucosa- mechanical and chemical stimuli
What is the afferent nerve for sneezing?
Trigeminal (V)
Where is the sneezing centre?
Medulla oblongata
What are the effects of a sneeze being stimulated?
Eye closing, inspiration, closure of glottis, increased intrathroacic pressure, expiration
What effects do sneezes and coughs have on the renal system?
Both involve closure of the external urethral sphincter and contraction of pelvis muscles
What is the nasopulmonary reflex, what is it mediated by?
Not 100%
Stimulation of nasal cavity causes bronchoconstriction
By trigeminal and vagal nerves
What can increased respiratory demand occur?
Exercise, reduces inspired oxygen tension, disease states
What is minute ventilation?
RR x TV
What is alveolar dead space?
A ventilated alveolar that is not perfused
How does hyperventilation lead to hypoxaemia?
Hyperventilation leads to hypercapnia because CO2 is more soluble than oxygen, lowering ventilation
How can hyperventilation lead to respiratory alkalosis?
Excessive loss of CO2 leads to alkalosis due to H+ being removed indirectly
How does increases respiratory rate and tidal volume increase O2 offloading?
Increased workload and metabolic demand on respiratory muscles, increases CO2 and H+ production, this facilitates O2 offload by increasing Hb affinity
What does mouth breathing a common feature of and why?
Dyspnoea
Increased ventilation demand causes demand for low resistance to air flow
How can pressure of breathing and compliance be improved by posture?
Sternal recumbancy with elbows abducted
What is respiratory failure?
The end result of uncontrolled respiratory disease, there are two types
What is type 1 respiratory failure?
Hypoxia with normal or hypocapnia
What is type 2 respiratory failure?
Hypoxia with hypercapnia
What causes type 2 respiratory failure?
Usually obstruction
BAB normal but inadequate ventilation
O2 supplementation can worsen hypercapnia by reducing respiratory drive
What causes type 1 respiratory failure?
Usually disease in lung parenchyma
Alveolar ventilation increased to try and manage hypoxia induced by disease of the gas-exchange portion
Leads to blowing off which can still be exchanged across the compromised BAB
Responds to O2
