Respiratory function in pregnancy at sea level and at high altitude

Objective To determine the effect of pregnancy on respiratory function in a non-Caucasian group and determine whether there was an interaction between pregnancy and altitude of residence. Design Prospective cross sectional study. Setting Antenatal clinics in Peru, at sea level in Lima and at high altitude in Cerro de Pasco. Sample Peruvian women with singleton pregnancies; 122 living at sea level and 192 living at 4300 in altitude in the Peruvian Andes. At each location, 19 non-pregnant women were also studied. Methods Respiratory function was measured in pregnant and non-pregnant women living at sea level and at 4300 in. Main outcome measures Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEFR), total lung capacity (TLC), inspiratory capacity (IC), residual volume (RV), expiratory residual volume (ERV) and functional residual capacity (FRC). Results At sea level, RV and TLC were higher in the third compared with the first trimester (P < 10.05). At high altitude, FEVI (P < 0.01), ERV (P < 0.01) and FRC (P < 0.01) were lower in the third compared with the first trimester. Pregnant and non-pregnant women at high altitude were 4 cm shorter (P < 0.0001) and had larger lung volumes (P < 0.01); their total lung capacities were approximately 1 L greater than women living at sea level (P < 0.0001). Conclusion These results suggest that the effect of pregnancy on the respiratory function of healthy women is influenced by altitude of residence.