Inclusion Criteria:  Patients who meet criteria for common variable immune deficiency (CVID) who are on stable IGRT for at least 3 months and who have an FEF25-75% between 50% and 80% of predicted. Patients who are already on Hizentra will be preferred.  Exclusion Criteria:  Age <21 or cannot perform spirometry. Smokers with 20 pack years or more, and active smokers will not be included among the study subjects, but will be considered separately as an ancillary study. Patients with specific antigen-specific antibody deficiencies or X-linked agammaglobulinemia on IGRT will not be included among the 20 study subjects, but will be considered separately in ancillary studies. Patients with heart failure, TB, bronchiolitis, or lymphangioleiomyomatosis.