Case Report

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, 3945].

FeatureChangeWeek 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.