Physiological Consequences of Respiratory Centre Depression Flashcards Preview

Respiratory > Physiological Consequences of Respiratory Centre Depression > Flashcards

Flashcards in Physiological Consequences of Respiratory Centre Depression Deck (31)

What is the purpose of the respiratory system?

To keep blood oxygen at 100mmHg, carbon dioxide at 40mmHg and pH at 7.40


How is the respiratory system controlled?

By controlling the respiratory muscles, chest wall and airways to alter ventilation


Can gas exchange be controlled?

No - because it is a passive process but it is altered indirectly via ventilation


Where is the central controller of the respiratory system?

The brain stem (pons and medulla) and the cortex


What is the role of the neurons in the brain stem?

To generate a an automatic rhythm of inspiration


What is the major output of the respiratory centre?

The phrenic nerves


What is the role of the cortex in the respiratory centre?

To give voluntary control to alter the output of the brainstem


What receptors feed in to the central controller?

Central chemoreceptors, peripheral chemoreceptors, stretch receptors in the lung, irritant receptors in the lung, stretch receptors in the muscle, joint position receptors in the muscle, receptors for touch, temperature and pain, emotional stimuli acting through the limbic system


Where are the central chemoreceptors located?

on the ventral surface of the medulla where they are in contact with the CSF


What do central chemoreceptors respond to?



Where are the peripheral chemoreceptors located?

in the carotid bodies at the bifurcation of the common carotid and in the aortic bodies at the arch of the aorta


What do peripheral chemoreceptors respond to?

H+, CO2 and O2


What is the result of a small increase in CO2?

Rapid increase in ventilation


What is the result of a small fall in O2?

No change in ventilation


What O2 pressure is required to influence ventilation?



What is the relationship between work and minute ventilation?

Linear - match ventilation with oxygen consumption


What is the relationship between PaO2, PaCO2 and pH with work?

Blood gases remain constant while work increases


What happens at high levels of work?

There is anaerobic metabolism which generates extra acid, so to compensate there is a further increase in ventilation - this leads to a decrease in CO2 and an increase in O2 to allow pH to return to just below normal


What happens to breathing in anxiety?

There is excessive ventilation for oxygen consumption and CO2 production so the result is respiratory alkalosis


What is hypoventilation?

When ventilation is not meeting the metabolic requirements for oxygen consumption and carbon dioxide production


What is the result of acute hypoventilation?

respiratory acidosis


What is the result of chronic hypoventilation

metabolic alkalosis?


What are the causes of hypoventilation?

Reduced respiratory centre activity, neuromuscular disease, chest wall deformity, gross obesity, sleep disordered breathing


What are the 3 types of sleep disordered breathing?

obstructive sleep apnoea, central sleep apnoea, obesity hypoventilation syndrome


What is obstructive sleep apnoea?

A transient obstruction to the throat during sleep which prevents breathing


Why does the obstruction occur in OSA?

airway muscles relax in sleep, the throat is already narrowed e.g. by obesity and the tongue falls backward if supine


What makes you wake up in OSA?

Reduced O2 and increased CO2


What is the management for OSA?

weight loss, CPAP, lying on side, mandibular advancement splint, surgery


What is the long term consequence of sleep disordered breathing?

The brainstem will start to accept higher levels of CO2 and lower levels of O2 so that sleep can continue without being disrupted - leads to chronic hypercapnea with normal pH and high bicarbonate (compensated respiratory acidosis)


What will happen to respiratory drive in long term sleep disordered breathing?

Will become dependent on hypoxic drive - more dependent on PaO2


What will happen if you give someone with hypoxic drive supplementary oxygen?

They will develop acute hypoventilation