Jumat, 03 Juli 2015

Some of the physiological changes induced by pregnancy were recently summarized
by Wise and associates (2006):

1. Vital capacity and inspiratory capacity increase by approximately
20 percent by late pregnancy
2. Expiratory reserve volume decreases from 1300 mL to
approximately 1100 mL
3. Tidal volume increases approximately 40 percent as a result
of the respiratory stimulant properties of progesterone
4. Minute ventilation increases about 30 to 40 percent due to
increased tidal volume. Arterial pO2 also increases from 100
to 105 mm Hg
5. Carbon dioxide production increases approximately 30 percent,
but diffusion capacity also increases, and with alveolar
hyperventilation, the pCO2 decreases from 40 to 32 mm Hg
6. Residual volume decreases approximately 20 percent from
1500 mL to approximately 1200 mL
7. The expanding uterus and increased abdominal pressure
cause chest wall compliance to be reduced by a third. Thus,
the functional residual capacity—the sum of expiratory
reserve and residual volumes—decreases by 10 to 25 percent