@article {Vilozni981, author = {Daphna Vilozni and Adi Dagan and Moran Lavie and Ifat Sarouk and Bat-El Bar-Aluma and Moshe Ashkenazi and Sarina Levy Mendelovich and Yael Betzalel and Ori Efrati}, title = {The Value of Measuring Inspiratory Capacity in Subjects With Cystic Fibrosis}, volume = {63}, number = {8}, pages = {981--987}, year = {2018}, doi = {10.4187/respcare.05920}, publisher = {Respiratory Care}, abstract = {BACKGROUND: Inspiratory capacity (IC) is often overlooked as an important measured index of spirometry in patients with cystic fibrosis (CF). Abnormally low IC may indicate the onset of static/dynamic hyperinflation, which may be accompanied by dyspnea and an increase in the work of breathing. This cross-sectional study sought to determine whether measuring IC during spirometry, may add clinical value to FEV1 measurements in CF subjects.METHODS: Anthropometric, clinical, spirometry, and static lung volume data were gathered retrospectively from 98 of 165 subjects with CF (mean {\textpm} SD age 26.8 {\textpm} 11.0 y) registered in The Edmond and Lily Safra Children{\textquoteright}s Hospital, Sheba Medical Centre, Israel. We compared the IC (\% predicted) to FEV1, static lung volumes, and hospitalization days/year.RESULTS: IC decreased alongside FEV1 decline but at a slower pace (r2 = 0.32). Incremental trapped air, as measured by residual volume (RV), and a rapid elevation in the ratio of RV to total lung capacity occurred when IC deteriorated below 60\% predicted values. The unique combination of IC \< 50\% predicted and FEV1 \> 40\% predicted induced an increase of up to 125 hospitalization days/year compared to subjects having IC \> 50\% predicted (up to 73 d/y, P \< .001).CONCLUSIONS: Measuring IC in CF subjects may reveal silent worsening of lung function as indicated by a decline in IC \< 50\% predicted while FEV1 is still \> 40\% predicted. This condition may lead to inefficient breathing at high lung volumes, which may explain a subjective sensation of breathlessness and lead to an increase in hospitalization days/year.}, issn = {0020-1324}, URL = {https://rc.rcjournal.com/content/63/8/981}, eprint = {https://rc.rcjournal.com/content/63/8/981.full.pdf}, journal = {Respiratory Care} }