Week 3 - Ventilation Flashcards
How do alveoli make it easier for gas exchange?
- One cell thick, small distance to travel
- Numerous alveoli (more gas exchange)
- Supplied with many blood capillaries that have a continuous flow of blood across alveoli
- Alveoli have thin film of water to allow gases to dissolve
Explain V / Q ratio
Ventilation / Perfusion ratio is the amount of gas in the alveoli over the amount of blood flow to the alveoli
Ideally what do want the V / Q ratio to be?
1 / 1 = 1.0, but average is 0.8
When does V / Q ratio differ?
- In different parts of the lungs
- In different postures
- When there are problems with ventilation of blood flow
What is the unit of measure for gases
Millimetres of Mercury
Normal aPO2
100mmHg
Normal aPCO2
40mmHg
What lowers ventilation in the alveoli? And what does the body do to combat this?
An obstruction within the airways e.g. inflammation in airway walls or mucus
Low PO2 causes pulmonary capillaries to constrict and shunt blood to other alveoli.
How do we cough?
RARs and SARs (rapid/slowly adapting pulmonary stretch receptors) send signal to medulla through vagus nerve. Medulla sends efferent signal through phrenic, spinomotom and vagus nerve to effector muscles (respiratory, laryngeal and bronchi smooth muscle).
3 phases during a cough
- Inspiratory phase - deep breath, stretch expiratory muscles, pressure increases inside lungs
- Compression phase - glottis closes, respiratory muscles contract, increase pressure even more
- Expiratory phase - glottis opens and air is pushed out because of high pressure in lungs.
What is hypoxaemia?
Decrease in the partial pressure of oxygen in the blood
How could you measure if someone was hypoxaemic?
Pulse oximetry, arterial blood gases
What might cause hypoxaemia?
Reduced PO2 in air, reduced ventilation, ventilation-perfusion mismatch
What is hypoxia?
Reduced level of tissue oxygenation
How could you tell if someone was hypoxic?
Reduced brain function, blue lips, fingers, toes, rapid HR and RR
