A LONGITUDINAL STUDY OF IMPULSE OSCILLOMETRY AND RESPIRATORY MECHANICS IN PREGNANCY: IMPLICATIONS FOR RESPIRATORY DISORDERS

Abstract

TYPE: Late Breaking Abstract TOPIC: Pulmonary Physiology PURPOSE: Examine positional and longitudinal changes in airway resistance and reactance during early and late pregnancy. METHODS: A longitudinal observational study enrolled pregnant women in the first trimester. Impedance oscillometry was performed in the seated, supine, and most comfortable sleeping positions in early and late pregnancy. Airway resistance was measured at 5 and 20Hz, reactance at 5Hz. Lung volumes were simultaneously measured in the seated and supine positions. Progesterone and estradiol were measured at two time points. RESULTS: 242 women (59% White) were enrolled with mean BMI 34.4 Kg/m2, 135 with longitudinal measurements. Airway resistance and reactance significantly increased with the change from the seated to the supine, and to the most comfortable sleeping position, in early and late pregnancy (p<0.00001). Most comfortable sleeping position was associated with lower resistive load than supine position (p<0.0006). Airway resistance significantly increased with pregnancy progression (p<0.004) and related to increased small airway resistance (R5-R20Hz P=0.009). Increased airway resistance did not correlate with changes in serum progesterone. Airway reactance increased with pregnancy progression (P<0.00001). FRC dropped with position change at both time points (p<0.00001) but not with pregnancy progression. ERV dropped (13.3%) with pregnancy progression (p<0.00001). CONCLUSIONS: Resistive and elastic loads increase in the supine position in early and late pregnancy and with pregnancy progression. Resistive load increases with pregnancy progression relate mostly to increased small airway resistance, which may be due to reduced ERV. CLINICAL IMPLICATIONS: Increased resistive loads may contribute to asthma exacerbations, while increased elastic loads may contribute to respiratory complications in women with obesity or chest wall abnormalities. DISCLOSURE: No significant relationships. KEYWORD: airway resistance