Maternal Adaption of the Respiratory System Flashcards Preview

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Flashcards in Maternal Adaption of the Respiratory System Deck (17):

Why do respiratory adaptions take place during pregnancy?

Occur to meet increasing metabolic demands during pregnancy.

Increased requirements of the placenta and therefore fetus.

Changes are instigated due to the effect of bio-chemicals, hormones and mechanics.


How do rising levels of progesterone affect the homeostatic controls in the respiratory centre in the brain?

The medulla becomes more sensitive to changing levels of CO2 (carbon dioxide). Therefore increases in PaCO2 (partial pressure of carbon dioxide) result in exaggerated respiratory effort.


What changes do the altering hormone levels result in for the mucosal vasculature of the respiratory tract?

Engorgement and swelling of the lining of the nose, oropharynx, larynx and trachea.


By what percentage does the tidal volume of the lungs increase during pregnancy?

Almost 50%


What effect does the enlargement of the uterus later in pregnancy have?

Exerts pressure upon the diaphragm causing an increase in resting oxygen requirements and work needed for breathing


Describe the status of the following from the middle of the 2nd trimester:
Expiratory reserve volume
Residual volume
Functional residual volume

They decrease progressively by 20%


What is minute ventilation?

Minute ventilation is the entire lung ventilation process per minute. This is the product of tidal volume and respiration rate.


What percentage does minute ventilation increase by above normal levels around the second trimester?



By what percentage do tidal volume and respiratory rate increase by during pregnancy?

Tidal volume: 40%
Respiratory rate: 15% (an extra 2-3 breaths)


What is respiratory alkalosis?

A medical condition in which increased respiration (hyperventilation) elevates the blood pH


Only CO2 tensions below what mmHg will lead to respiratory alkalosis?



Describe in detail, the SEVEN adaptions which take place during pregnancy

The diaphragm rises by 4cm

Changes in the diameters of the chest – lower ribs flare

Chemoreceptors detect increase in PaCO2 which results in increased ventilation of the lungs

The subcostal angles increase from 68 to 103 degrees in late gestation

Relaxation of the muscles and cartilage of the thorax occurs.

The volume of air inspired in 1 minute increases by 50%

Mild respiratory alkalosis is created assisting gaseous exchange across the placenta.


What are the FOUR symptoms of respiratory alkolosis?

Tingling of extremities


Deep, rapid breathing



What two reactions may occur in labour if there is insufficient time for uterine relaxation after a contraction?

Myometrial hypoxia

Metabolic acidosis


What effect does inadequate oxygenation and maternal acidosis have on the fetus?

Fetal PaCO2 rises


By what percentage is oxygen consumption increased by in labour?

Up to and over 60%


How many weeks on average does it take the ventilatory and anatomical respiratory changes to return to pre-pregnancy state?

1-3 weeks