Babies who are born prematurely often develop a chronic lung disease called bronchopulmonary dysplasia (BPD). BPD puts babies at higher risk for problems with growth and development. Diuretics, such as furosemide, are frequently used in the management of early BPD). Many clinicians use informal trials of therapy to see if a baby responds to diuretics in the short-term before starting chronic diuretic therapy. Despite frequent use of diuretics, it is unclear how many babies truly respond to therapy and if there are long-term benefits of diuretic treatment. Designing research studies to figure this out has been challenging. The Pragmatic Research on Diuretic Management in Early BPD (PRIMED) study is a feasibility pilot study to help us get information to design a larger trial of diuretic management for BPD. Key questions this study will answer include: (1) Can we use an N-of-1 trial to determine whether a particular baby responds to furosemide? In an N-of-1 trial, a baby is switched between furosemide and placebo to compare that particular infant's response on and off diuretics. It is a more rigorous approach to the informal trials of therapy that are often conducted in clinical care. We hope to learn how many babies have a short-term response to furosemide ("responders"); (2) how many babies will still be on respiratory support at the end of the N-of-1 trial? This will help us determine how many patients would be eligible to randomize to chronic diuretic therapy in the second phase of the larger trail, and (3) if a baby is identified as a short-term responder, how many parents and physicians would be willing to randomize the baby to chronic diuretics (3 months) versus placebo in the longer trial?

Inclusion Criteria:

1. <28 weeks gestation at birth
2. Post-Menstrual Age (PMA) of 29-32 weeks gestation
3. Requiring invasive positive pressure respiratory support or NIPPV/NIMV and FiO2 ≥ 25% or requiring non-invasive positive pressure respiratory support (NCPAP≥ 5 cm H20, BiPhasic CPAP) and FiO2 ≥ 30%.
4. Receiving enteral feedings of 120 mL/kg/day or greater
5. Expected to be hospitalized for at least 28 days after enrollment

Exclusion Criteria:

1. Major congenital anomalies (e.g., known renal anomalies, congenital heart disease, congenital diaphragmatic hernia, or chromosomal anomalies)
2. In infants who had electrolyte testing in the week prior to enrollment, those with a serum creatinine > 1.7 mg/dL, BUN >50 mg/dL, Na <125 mmoL/L, K ≤ 2.5 mmol/L, or Ca ≤ 6 mg/dL. Not having electrolyte testing in the week prior to enrollment is not an exclusion criterion.
3. Current treatment with Dexamethasone or hydrocortisone for respiratory failure. Treatment with chronic steroids for history of adrenal insufficiency or cardiovascular instability is not an exclusion criterion.
4. Treatment with any longer-acting diuretic (e.g., chlorothiazide, hydrochlorothiazide, acetazolamide) within 5 days of enrollment where exposure may result in carryover effects that confound the N-of-1 trial
5. Active order for standing, regularly scheduled diuretics (e.g., chronic diuretics)
6. Non-English speaking
7. Current treatment with ibuprofen or indocin

Participant, care provider, investigator, outcomes assessor learn the order of furosemide and placebo administration at the end of their N-of-1 trial.