Pulmonary Arteriovenous Malformation Unmasked by Pregnancy: A Review of Pulmonary Arteriovenous Malformations and Cardiovascular and Respiratory Changes in Pregnancy
Table 3
Physiological changes of respiratory system during the pregnancy [37, 39–45].
Feature
Change
Week of pregnancy/trimester
Chest compliance
↓
Total lung capacity
↓ By 5%
Vital capacity
=
The functional residual capacity
↓ By 10-25%
Functional residual capacity
↓ By 10-25%
Expiratory reserve volume
↓ By 15-20%
Tidal volume
↑ By 30-50% (from 500 to 700 mL)
Minute volume
↑ By 40%
During 1st trimester
Respiratory rate
↑ By 1-2 breaths more than normal
Minute ventilation
↑ By 20–50% (from 7.5 to 10.5 L/min)
Residual volume
↓ By 20-25%
The expiratory reserve volume
↓ By 15–20% (200-300 mL)
The residual volume
↓ by 20–25% (200-400 mL)
Total lung capacity
↓
Respiratory capacity
↑ By 5-10%
Inspiratory capacity
↑ By 5–10% (200–350 mL)
The total lung capacity
↓ By minimally 5%
By term
Spirometry parameters (FVC, FEV1)
=
Oxygen consumption
↑ By 20-40%
Metabolic rate
↑ By 15%
Oxygen reservoir
↓
PaO2
↑
PaCO2
↓
Bicarbonate levels
↓ To 18–21 mmol/L
Blood pH
↑ To 7.44 (respiratory alkalosis with a compensatory metabolic acidosis)
Abbreviations: FVC: forced vital capacity; FEV1: forced expiratory volume in 1 second; PaO2: partial pressure of oxygen in the arterial blood; PaCO2: partial pressure of carbon dioxide in the arterial blood.
