Lung Physiology 1: General principles Flashcards
What is the requirement of the respiratory pump?
- To move 5 litres / minute of inspired gas
What is the respiration pump doing?
- Negative intra-alveolar pressure draws air in (inspiration) to generate flow
What is involved with the respiratory pump?
Bones, muscles, pleura, peripheral nerves and airways
What muscles are involved in the respiratory pump during inspiration?
- Diaphragm 70% of volume change (phrenic C3-5 innervation)
- External intercostals – lift ribs 2-12, widen thoracic cavity
- Muscles relax to allow passive expiration
- Diaphragm is contracted in this state (flattened so increase volume of thorax)
What muscles are involved in the respiratory pump during expiration?
- Internal intercostals – depresses ribs 1-11
- Rectus abdominis – depresses lower ribs, compresses abdominal organs and diaphragm
- Diaphragm is relaxed in this state (domed so reduced volume of the thorax)
What nerves are involved in respiration?
- Sensory (assessing flow, stretch)
(afferent via vagus nerve - 10th cranial nerve which helps spacial awareness so when our eyes are closed we know where the thorax is for e.g.) - Autonomic; sympathetic and parasympathetic
What is a resting lung volume and how do we change it?
- Chest wall and lungs have elastic properties and a resting (unstressed) volume
- To change this volume requires force
- Release of force leads to a return to the resting volume
What is ventilation?
Flow of O2 in and CO2 out
- Total combined surface area for gas exchange is 50-100 m2
What is perfusion?
When the body delivers blood through the capillary bed into tissue and so it requires an adequate pulmonary blood supply
What is dead space and how many mls do we have?
The volume of air not contributing to ventilation
- some lost to anatomic (nasal, larynx) approx 150mls
- some lost to alveolar approx 25mls
anatomic + alveolar = 175mls dead space
How is the heart supplied with blood?
- Right and left coronary arteries
- Left split into circumflex and anterior inter ventricular branch
How are the bronchioles circulated (blood)?
- Blood supply to the lungs via branches of the bronchial arteries and also supply peri-bronchial tissue and visceral pleura
- Venous drainage via bronchial veins draining ultimately to superior vena cava
How is pulmonary circulation?
- Right and left pulmonary arteries run out of right ventricle
- Much lower pressure 24mm/10mm
- There is 17 orders of branching
What is the broncho-vascular bundle?
- A pulmonary artery and bronchus airway run in parallel with each other
How many capillaries per alveolus?
1000 capillary
At rest when is haemoglobin fully saturated?
25% through the capillary bed
When are capillaries perfused with blood
At the most dependent parts of the lung are preferentially perfused with blood at rest
What does perfusion of capillaries depend on?
- pulmonary artery pressure
- pulmonary venous pressure
- alveolar pressure
What happens if we have a hypoxic pulmonary?
- this is a cut in the lung
- If the lung is damaged, we stop blood going there via vasoconstriction as it is a waste if there is no air getting there anyway
What is PaCO2?
arterial CO2
What is PACO2?
Alveolar CO2
What is PaO2?
arterial O2
What is PAO2?
Alveolar O2
What is PiO2?
Pressure of inspired oxygen
