Resp Physiology Flashcards
What are causes of respiratory acidosis?
Life-threatening asthma COPD Obesity hypoventilation syndrome Opiate overdose Neuromuscular disease Benzodiazepines overdose
What are causes of respiratory alkalosis?
Pulmonary embolism Anxiety leading to hyperventilation CNS disorders - stroke, subarachnoid haemorrhage, encephalitis Altitude Pregnancy Salicylate poisoning
Tidal volume
Volume inspired or expired with each breath at rest
Males - 500ml
Females - 350ml
Inspiratory reserve volume
Maximum volume of air that can be inspired at the end of a normal tidal inspiration
2-3L
Inspiratory capacity
Tidal volume + inspiratory reserve volume
Expiratory reserve volume
Maximum volume of air that can be expired at the end of a normal tidal expiration
750ml
Residual volume
Volume of air remaining after maximal expiration
Increases with age
RV = FRC - ERV
Functional residual capacity
The volume in the lungs at the end-expiratory position
FVC = ERV + RV
Vital capacity
Maximum volume of air that can be expired after a maximal inspiration
VC = inspiratory capacity + ERV
5L
Total lung capacity
Vital capacity + residual volume
Type 1 pneumocytes
Simple squamous epithelium, gas exchange
Type 2 pneumocytes
Synthesise surfactant
This reduces surface tension at the alveolar surface
Not involved in gas exchange
What muscles are used for inspiration?
Diaphragm
External intercostals
Sternocleidomastoids
Scalenes
What muscles are used for expiration?
Internal intercostals
Abdominals
What are the normal values for alveolar and arterial gas partial pressures?
Normal alveolar ventilation – 4.2L/min
Normal PO2 – 13.3kPa at 100mmHg (alveolar ventilation)
Normal PCO2 – 5.3kPa at 40mmHg (alveolar ventilation)
What is compliance?
The change in volume relative to a change in pressure ie a measure of the lungs ability to stretch and expand
What is alveolar dead space?
Alveoli that are ventilated but not perfused
What is anatomical dead space?
The air in the conducting zone of the RT that is unable to take part in gas exchange
Central chemoreceptors
Medulla
Responds directly to H+ - directly reflects PCO2
Primary ventilatory drive – the main stimulus for breathing
Peripheral chemoreceptors
Carotid and aortic bodies
Respond primarily to plasma [H+] and PO2 (less so to PCO2)
Second ventilatory drive
