Clinical Trial The goal of this clinical trial is to learn whether different enteral feeding cycles (18-hour, 20-hour, or standard 24-hour continuous feeding) improve outcomes for critically ill ICU patients who need tube feeding. It will also look at tolerance, nutrition delivery, and safety.

The main questions it aims to answer are:

Do shorter feeding cycles (with fasting windows) reduce ICU length of stay?

Do they lower the risk of infections like ventilator-associated pneumonia?

How do they affect calorie delivery, blood sugar control, and gastrointestinal tolerance?

Researchers will compare:

Continuous 24-hour feeding (standard care)

20-hour feeding with a 4-hour fasting window

18-hour feeding with a 6-hour fasting window

Participants will:

Be critically ill adults in the ICU who require at least 7 days of enteral feeding

Be randomized to one of the three feeding schedules

Receive daily monitoring of calories, protein, blood sugar, and GI tolerance

Have outcomes measured, including ICU length of stay, infections, metabolic control, and feeding tolerance

This randomized controlled trial will compare three enteral feeding regimens in critically ill ICU patients: standard 24-hour continuous feeding, 20-hour cycled feeding with a 4-hour fasting window, and 18-hour cycled feeding with a 6-hour fasting window. The rationale is that continuous feeding may impair metabolic regulation, increase insulin requirements, and contribute to gastrointestinal intolerance, while cycled feeding could better align with circadian rhythms, support metabolic balance, and reduce complications such as ventilator-associated pneumonia.

Approximately 150 adult patients who require enteral nutrition for at least seven days will be enrolled across Hamad Medical Corporation ICUs. Participants will be randomized in a 1:1:1 ratio using block randomization through REDCap to ensure allocation concealment. All groups will receive isocaloric enteral nutrition through nasogastric or orogastric tubes, with caloric and protein targets guided by indirect calorimetry or weight-based calculations.

Feeding plans will be initiated within 24 hours of ICU admission or stabilization. Patients assigned to the 18-hour and 20-hour arms will have structured fasting periods, while the control group will receive uninterrupted feeding. Daily assessments will capture nutritional delivery, gastrointestinal tolerance, and metabolic parameters, along with safety monitoring for adverse events. Data will be collected electronically via REDCap, de-identified, and audited regularly by the Clinical Trial Unit.

The study is designed to generate high-quality evidence on whether incorporating fasting windows into feeding schedules can optimize nutrition therapy, improve tolerance, reduce ICU stays, and minimize complications. Findings are expected to inform future ICU nutrition guidelines and contribute to the global discussion on intermittent versus continuous feeding practices.

Inclusion Criteria

Participants must meet ALL of the following criteria to be eligible for the study:

1. Patients aged ≥ 18 years.

2. Patients expected to require enteral nutrition (EN) for ≥ 7 days.

3. Critically ill, mechanically ventilated patients in the ICU.

4. New patients initiating EN in the critical care unit.

5. Patients receiving EN via:

   • a nasogastric (NG) tube.
   • orogastric (OG) feeding tube.

Exclusion Criteria:

1. Patients with contraindications to enteral feeding or pre-existing gastrointestinal disorders, including:

   • Active GI bleeding.
   • Progressive GI disease.
   • Recent GI tract resection.

2. Indication for a special diet formula.

3. Need for a large volume of feeding (as determined by the clinical team).

4. Pre-existing hepatic failure.

5. Use of a nasojejunal tube, gastrostomy, or jejunostomy.

6. Pregnancy confirmed via β-hCG testing for women of childbearing potential.

7. Insulin-dependent diabetes mellitus.

Data will be collected and de-identified, codes will be used to cover patient identifiers such as Name, HC no., DOB. Any link between code and identifier will be deleted at the end of the data collection and anonymized data will be kept for at least 5 years after study completion. Study participation is documented using a unique study ID (e.g., "EN-001") rather than patient names. Access to identifiers is restricted to the research team and audited by the clinical trial unit (CTU) in HMC. The data that will be collected for this study will remain confidential.

Participants and clinical care teams will be aware of the assigned enteral feeding schedule. Outcome assessors and the statistician performing the final analysis will be blinded to group allocation where feasible.