Spirometric Changes during Pregnancy in Cystic Fibrosis Patients

Rationale: Survival and longevity in patients with cystic fibrosis (CF) have improved with new treatments, so that pregnancy can be safely undertaken despite physiologic limitations. Dyspnea still develops in the latter stages of pregnancy. To explain this symptom, we evaluated the effect of pregnancy on lung function before and after delivery. Methods: Records of 23 pregnant patients with CF were retrospectively reviewed for data analysis. Spirometry was recorded prior to pregnancy, at first and third trimesters, and every three months following delivery up to one year. Comparisons between time points were adjusted for age and pre-gestational BMI by analysis of variance (ANOVA). Results: Complete clinical and spirometric data were available for eleven of these patients (13 pregnancies total), obtained between 2009 and 2017. FEV1 and FVC declined significantly from baseline to third trimester (by 8.1%, p < 0.043 and 9.3%, p < 0.013, respectively). No statistically significant differences amongst spirometric values were observed, however, when adjusted for BMI and age over the entire time course. FEV1 and FVC recovered to baseline six months and one year following delivery, respectively. Conclusions: The changes in FEV1 and FVC occur as a result of increases in intravascular blood volume and lung water during the third trimester. At the same time, FEV1/FVC increases as there is reversal of bronchiolar constriction with elimination of extracellular fluid and lung water. Furthermore, restoration of end-expiratory lung volume post-partum counteracts reversal of air trapping with resolution of peribronchiolar edema, with FVC remaining unchanged. These changes would explain decrease in dyspnea following delivery in CF patients.

Lung Hyperinflation Is Associated with Pulmonary Exacerbations in Adults with Cystic Fibrosis

Background: Forced expiratory volume 1 second (FEV1) has traditionally been used as a readily available marker of health in adult cystic fibrosis (CF). However, due to the obstructive nature of this disease, it is possible that lung hyperinflation could be more closely related to disease severity than is FEV1. The purpose of this study was to determine if hyperinflation is more closely associated with quality of life, functional status, and pulmonary exacerbations than FEV1 in patients with CF. Methods: Sixty-eight adult patients with CF were evaluated in this retrospective study. We used IC and functional residual capacity (FRC) and their ratios to total lung capacity (TLC) as measures of lung hyperinflation. We used bivariate correlations and backwards regression analysis to assess possible associations between FEV1, lung hyperinflation, and measures of disease severity including questionnaire based quality of life, pulmonary exacerbation frequency, and mortality. The respiratory component of the Cystic Fibrosis Questionnaire–Revised (CRQ-R-Respiratory) was used as a measure of quality of life. Results: Both FEV1 and IC were negatively correlated with pulmonary exacerbations over a 3 year period (p = 0.004, r2 = 0.127;p < 0.001, r2 = 0.307, respectively), while FRC/TLC correlated positively with exacerbations (p = 0.007). Backwards regression analysis showed that among pulmonary function variables, IC had the strongest relationship with exacerbations over 3 years. A lower CFQ-R-Respiratory score was associated with greater mortality (p = 0.005). However, no statistically significant relationships were found between lung function and mortality. Conclusions: FEV1 and lung hyperinflation-as measured by IC and FRC/TLC-are both associated with pulmonary exacerbation frequency. This suggests that chronic dynamic hyperinflation contributes significantly to disease severity in adult cystic fibrosis.