PURPOSE: to investigate the normal peak expiratory flow values in healthy pregnant women employing a portable expiratory apparatus (Mini-Wright Peak Flow Meter), and to relate the obtained measurements to each patient's height, body mass index (BMI) and age, along gestation. METHODS: a longitudinal prospective study including 26 pregnant women followed up from the first trimester to the 36th week of gestation and examined every four weeks. On the occasion of seven visits, the pregnant women performed forced exhaling into a portable expiratory apparatus three times, with the highest value being considered the peak expiratory flow. All measurements were made under the same investigator's supervision in order to reduce the margin of error. Pearson coefficient was used to calculate the correlation between flow and BMI, between flow and patient's height, and between flow and patient's age. RESULTS: the variation in flow values during pregnancy can be determined by flow = 328.32 -0.07 x week, with a Pearson coefficient equal to zero. To determine whether there was a difference in the correlation coefficients between BMI and flow, we compared the lowest coefficient (0.47 for week 30, flow = 123.49 + 7.64 x BMI) with the highest coefficient (0.59 for week 34, flow = 87.77 + 9.05 x BMI) of each studied time interval and obtained a value of 0.22, indicating a good correlation between the flow and BMI variables. There was a positive correlation between height and flow (Pearson = 0.61), with flow = -477.47 + 497.38 x height. The correlation coefficient between flow and age was 0.24, with the equation obtained in this case being non-linear. CONCLUSIONS: peak expiratory flow values did not change along gestation. Higher flows were observed in taller women. Pregnant women with a higher BMI before gestation presented higher flows. There was no correlation between flow and maternal age.
Peak expiratory flow; Body mass index; Normal pregnancy
