|Respiratory System Changes During Pregnancy|
Respiratory Tract . Hormonal
changes to the mucosal vasculature of the respiratory tract lead to capillary
engorgement and swelling of the lining in the nose, oropharynx, larynx,
and trachea. Symptoms of nasal congestion, voice change and upper respiratory
tract infection may prevail throughout gestation. These symptoms can be
exacerbated by fluid overload or oedema associated with (PIH) or .
In such cases, manipulation of the airway can result in profuse bleeding
from the nose or oropharynx; endotracheal intubation can be difficult;
and only a smaller than usual endotracheal tube may fit through the larynx.
Airway resistance is reduced, probably due to the progesterone-mediated
relaxation of the bronchial musculature.
Lung Volumes . Upward displacement
by the uterus causes a 4 cm elevation of the diaphragm, but total
lung capacity decreases only slightly because of compensatory increases
in the diameters of the chest, as well as flaring of the ribs. These changes
are brought about by hormonal effects that loosen ligaments.
From the middle of the second trimester, expiratory reserve volume, residual
volume and functional residual volume are progressively decreased, by
approximately 20% at term.
Oxygen consumption increases
gradually in response to the needs of the growing foetus, culminating
in a rise of at least 20% at term. During labour, oxygen consumption is
further increased (up to and over 60%) as a result of the exaggerated
cardiac and respiratory work load.
The information in this page is presented in summarised form and has been taken
from the following source(s):
World Anaesthesia & the World Federation of Societies of Anaesthesiologists :
(def;articles & more)