The investigators propose a home hospital model of care that substitutes for treatment in an acute care hospital. Limited studies of the home hospital model have demonstrated that a sizeable proportion of acute care can be delivered in the home with equal quality and safety, reduced cost, and improved patient experience.

Hospitals are the standard of care for acute illness in the United States, but hospital care is expensive and often unsafe, especially for older individuals. While admitted, 20% suffer delirium, over 5% contract hospital-acquired infections, and most lose functional status that is never regained. Timely access to inpatient care is poor: many hospital wards are typically over 100% capacity, and emergency department waits can be protracted. Moreover, hospital care is increasingly costly: many internal medicine admissions have a negative margin (i.e., expenditures exceed hospital revenues) and incur patient debt.

The investigators propose a home hospital model of care that substitutes for treatment in an acute care hospital. Studies of the home hospital model have demonstrated that a sizeable proportion of acute care can be delivered in the home with equal quality and safety, 20% reduced cost, and 20% improved patient experience. While this is the standard of care in several developed countries, only 2 non-randomized demonstration projects have been conducted in the United States, each with highly local needs. Taken together, home hospital evidence is promising but falls short due to non-robust experimental design, failure to implement modern medical technology, and poor enlistment of community support.

The home hospital module offers most of the same medical components that are standard of care in an acute care hospital. The typical staff (medical doctor [MD], registered nurse [RN], case manager), diagnostics (blood tests, vital signs, telemetry, x-ray, and ultrasound), intravenous therapy, and oxygen/nebulizer therapy will all be available for home hospital. Optional deployment of food services, home health aide, physical therapist, occupational therapist, and social worker will be tailored to patient need. Home hospital improves upon the components of a typical ward's standard of care in several ways:

• Point of care blood diagnostics (results at the bedside in <5 minutes);
• Minimally invasive continuous vital signs, telemetry, activity tracking, and sleep tracking;
• On-demand 24/7 clinician video visits;
• 4 to 1 patient to MD ratio, compared to typical 16 to 1;
• Ambulatory/portable infusion pumps that can be worn on the hip;
• Optional access to a personal home health aide

Should a matter be emergent (that is, requiring in-person assistance in less than 20 minutes), then 9-1-1 will be called and the patient will be returned to the hospital immediately. In previous iterations of home hospital this happens in about 2% of patients.

Clinical parameters measured will be at the discretion of the physician and nurse, who treat the participant following evidence-based practice guidelines, just as in the usual care setting. In addition, the investigators will be tracking a wide variety of measures of quality and safety, including some measures tailored to each primary diagnosis.

Inclusion Criteria:

• Resides within 5-mile radius of emergency room
• English- or Spanish-speaker
• Can identify a potential caregiver who agrees to stay with patient for first 24 hours of admission. Caregiver must be competent to call care team if a problem is evident to her/him.
• This criterion may be waived for highly competent patients at the patient and clinician's discretion.
• >=18 years old
• Primary diagnosis of cellulitis, heart failure, complicated urinary tract infection, or pneumonia that requires inpatient admission as determined by blinded emergency room team.

Exclusion Criteria:

• Undomiciled
• No working heat (October-April), no working air conditioning if forecast > 80°F (June-September), or no running water
• On methadone requiring daily pickup of medication
• In police custody
• Resides in facility that provides on-site medical care (e.g., skilled nursing facility)
• Domestic violence screen positive
• Cared for by a private primary care physician who rounds in the hospital
• Cannot establish peripheral access in emergency department (or access requires ultrasound guidance)
• Secondary condition: active non-melanoma/prostate cancer, end-stage renal disease, acute myocardial infarction, acute cerebral vascular accident, acute hemorrhage
• Primary diagnosis requires narcotics for pain control
• Cannot independently ambulate to bedside commode
• As deemed by on-call medical doctor, patient likely to require any of the following procedures: computed tomography, magnetic resonance imaging, endoscopic procedure, blood transfusion, cardiac stress test, or surgery
• For pneumonia:
• Most recent CURB65 > 3: new confusion, blood urea nitrogen > 19mg/dL, respiratory rate>=30/min, systolic blood pressure<90mmHg, Age>=65
• Most recent SMRTCO > 2: systolic blood pressure < 90mmHg (2pts), multilobar chest xray involvement (1pt), respiratory rate >= 30/min, heart rate >= 125, new confusion, oxygen saturation <= 90%
• Absence of clear infiltrate on imaging
• Cavitary lesion on imaging
• O2 saturation < 90% despite 5L O2
• For heart failure:
• Has a left ventricular assist device or paced rhythm
• Get with the Guidelines - Heart Failure (>10% in-hospital mortality) or The Acute Decompensated Heart Failure National Registry score (high risk or intermediate risk 1)
• Anasarca
• Pulmonary hypertension
• For complicated urinary tract infection:
• Absence of pyuria
• Most recent quick sepsis related organ failure assessment > 1
• Home hospital census is full (maximum 4 patients at any time)