Search
Many changes in pulmonary physiology occur during pregnancy. These changes are generally well tolerated but can become problematic when pathologic states arise.
Here are a few examples of the normal changes and potential consequences:
Progesterone increases tidal volume and respiratory rate.
-
“Normally" a mild respiratory alkalosis pH 7.4-7.47, PaCO2 28-32, and bicarbonate 17-22 (renal compensation).
-
Low metabolic reserve with systemic illness.
Weight gain, anasarca, and breast size reduces chest wall elasticity.
-
Potential for restrictive physiology and reduced lung volumes.
-
Can be challenging to to mechanically ventilate due to decreased compliance and intra-thoracic pressure
Mechanical displacement of abdominal and thoracic contents by growing uterus.
-
Reduced lung volumes leading to reduced oxygen reserve and decreased apnea time.
-
Aim higher if placing chest tube (avoid abdominal contents)
-
Uterine pressure on stomach can increase aspiration risk and pulmonary injury.
References
Chestnutt, A. Physiology of Normal Pregnancy. Crit Care Clinic 20 (2004) 609-615