31. Disorders of the control of breathing. Age-dependent changes. Sleep-apnea syndrome

which processes must work correctly for respiration to be efficient?

Ventilation

Diffusion of gases across the alveolo-capillary membrane

Transport of gases in the blood

Oxygen uptake of cells

where are the neurons that control breathing muscles located?

respiratory centre in the medulla oblongata and pons

from where do the respiratory centre receive input from?

chemoreceptors

mechanoreceptors

cerebral cortex

hypothalamus

which information does chemoreceptors receive?

pH, pCO2 and pO2 levels in the blood

which information does mechanoreceptors receive?

inputs from the respiratory muscles and other skeletal muscles

cerebral cortex function in respiration?

conscious control of respiration

hypothalamus function in respiration?

controls respiration during stress and anxiety

what controls ventilation in physiological conditions?

pCO2 levels

in which condition will pO2 start to influence the breathing?

hypocapnia

describe how CO2-narcosis can occur in a COPD patient

When the pCO2 level has been high for a long time, like in chronic hypercapnia in case of COPD, the CO2-sensitivity of the chemoreceptors will be reduced.

Therefore, the respiratory system won’t react correctly to a hypercapnia and breathing might be driven by pO2 instead.

If the patient then receives oxygen therapy their pO2 become normal → nothing left to drive the respiratory centre!

The patients breathing will slow down → severe hypercapnia → CO2 narcosis

hypopnoea?

reduced tidal volume

(shallow breathing)

apnoea?

respiration stops after expiration → no inspiration

apneusis?

respiration stops after inspiration

Cheyne-stokes breathing?

abnormal breathing pattern:

first is the size of breathing large, then becomes smaller until breathing stops completely. Breathing starts again by itself, and the cycle repeats

seen in

• sleeping neonates, as their respiratory system is not fully developed yet

• adults in high altitudes

• patients with congestive heart failure

Biot-breathing?

frequency and depth of breaths are chaotic

periods of apneusis may occur

often seen in premortal patients

Kussmaul breathing?

characterised by hyperpnoea

occurs when blood pH is decreased, often because of ketoacidosis associated with diabetes

hyperpnoea is induced to try to get rid of the excess CO2 to increase pH

sleep apnoea syndrome?

> 30 periods of apnoea and hypopnoea that lasts more than 10s every night

causes significant changes in blood gas levels

two types: central and obstructive

central sleep apnoea?

• idiopathic

• most severe

• caused by defective autonomic regulation of breathing and is present at birth

• lead to insufficient or absent breathing during sleep

• no movement of chest during apnoeic periods

Obstructive sleep apnoea?

• most common

• caused by partial or complete obstructions of the upper airways

• chest will expand → no air will enter due to loose muscle tone of pharynx and soft palate obstructing the air flow

• air flow stop → arousal in CNS → symp. act + catecholamine release → patient wake up

• daytime sleepiness and fatigue