Respiratory System Flashcards by Patrick Enion

What is ventilation?

The movement of air through the airways

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Which of the following species has the most pliable nares: Sheep, Dog, Pig, Horse?

Horse

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What comprises the respiratory portion of the lung?

Respiratory bronchioles, alveolar ducts and sacs

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When does gas exchange occur at the alveolus?

During the whole respiratory cycle

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From which embryonic structure do the lungs develop ?

Foregut

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Why do premature neonates often experience respirator distress after birth?

Not enough surfactants

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Does increased airway diameter increase or reduce airway resistance?

Bronchodilation reduces airway resistance

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What part of the respiratory system is least turbulent

Bronchiole

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Where are peripheral chemoreceptors located?

Carotid and aortic sinuses

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What do central chemoreceptors in the respiratory system detect changes in?

PaCO2

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What is the pH range of mammals ECF?

7.35- 7.45

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What happens to the acid:base balance with respiratory obstruction?

Respiratory acidosis

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What might cause respiratory efficiency decrease during anaesthesia?

Drugs
Recumbancy
Equipment

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How do drugs cause a decrease in respiratory efficiency?

Direct effect on medulla oblongata- reduces inputs to respiratory centre- chemoreceptors, irritant receptors

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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

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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

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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

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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

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How is respiration monitored during anaesthesia?

Pulse oximeter
Capnography
Arterial/venous blood gas measurements

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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

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At what PaO2 does the level of Hb saturation start to decline significantly in the normal animal?

Below 75%

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What could effect the result of pule oximeter?

Vasoconstriction of the region measured
Abnormal haemoglobin
Equipment factors- movement, light

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What does capnography measure?

Measure the concentration/pp of CO2 in expired air via the breathing system

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What results does capnography produce?

Produces a curve

Gives a measurement of end-tidal CO2 (ETCo2)

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What PCO2 would you expect in a normal animal?

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