Understanding Intermittent Feeding Volume
Intermittent enteral feeding involves administering a specific amount of nutritional formula over a short period, typically 20 to 60 minutes, several times throughout the day. This approach is often contrasted with continuous feeding, where the formula is delivered at a slow, steady rate over many hours, and bolus feeding, which involves a much faster administration via gravity or syringe. The volume administered during each intermittent feed is not a fixed number but is determined by a patient’s overall daily nutritional needs, their specific health status, and their tolerance level. Proper calculation and careful adjustment are essential to prevent complications such as aspiration, gastric distension, or dehydration.
The Foundational Calculation of Feeding Volume
Determining the correct volume begins with a comprehensive nutritional assessment. This is a multi-step process that a healthcare professional, such as a registered dietitian, typically performs. The fundamental steps include:
- Calculate Total Energy Requirements: The first step is to determine the patient's total daily calorie needs. This is often estimated using predictive equations, like the Mifflin-St Jeor equation for general patients, or simplified ranges based on body weight. For example, a non-critically ill adult may require 25–30 kcal per kilogram of body weight per day.
- Determine Total Daily Volume: Once the total caloric requirement is established, the next step is to select an appropriate enteral formula. Formulas come in various concentrations, such as 1 kcal/mL, 1.2 kcal/mL, or 1.5 kcal/mL. To find the total daily volume, divide the total calories needed by the formula's caloric density.
- Formula: Total Daily Volume (mL) = Total Calories Needed / Caloric Density (kcal/mL)
- Divide into Intermittent Feeds: The final step is to divide the total daily volume by the number of scheduled feedings per day. A typical schedule might involve 4 to 6 intermittent feeds, mimicking a normal meal pattern.
Factors Influencing Intermittent Feeding Volume
While the formula provides a starting point, several patient-specific factors will influence the final volume and schedule. Healthcare providers will make adjustments based on:
- Patient Tolerance: Individual tolerance varies greatly. Some patients may experience gastric distension or diarrhea if the volume is too high or the administration is too fast. The feeding schedule may start with a smaller volume, such as 125 mL every 3 hours, and gradually increase to the target volume as tolerated.
- Type of Feeding Tube: The placement of the feeding tube (e.g., gastric vs. jejunal) is a critical factor. Intermittent feeding, especially at higher volumes, is generally reserved for tubes that end in the stomach, which can accommodate a larger volume of contents. Tubes in the small intestine (jejunal) lack the stomach's reservoir function and typically require slower, continuous feeding to prevent dumping syndrome.
- Clinical Status: A patient's overall health and stability are paramount. Critically ill patients may have impaired gastrointestinal motility and may initially require slower, continuous feeds. As their condition improves, they may transition to an intermittent schedule.
- Hydration Needs: The free water content of the formula needs to be considered. Additional water flushes are often necessary between feedings to meet the patient’s total daily fluid requirements.
Administration Techniques
Intermittent feedings can be administered using one of two primary methods:
- Gravity Drip: A feeding bag and tubing are used to hang the formula, and a roller clamp controls the flow rate. This method can take 20 to 60 minutes for each feeding session.
- Feeding Pump: An electric pump delivers the formula at a programmed rate, ensuring precise and consistent delivery over the specified time. This is particularly useful for patients who require tighter control over their infusion rate.
Comparison: Intermittent vs. Continuous Feeding
| Feature | Intermittent Feeding | Continuous Feeding |
|---|---|---|
| Administration | Scheduled intervals over 20-60 minutes, typically 4-6 times per day. | Constant, hourly rate over a prolonged period (e.g., 24 hours) using an electric pump. |
| Mechanism | Mimics a normal, physiological meal pattern, with periods of feeding and periods of rest. | Non-stop nutrient delivery that can provide a stable supply of calories. |
| Patient Mobility | Significantly higher mobility, as the patient is not connected to a pump continuously. | Restricts mobility, as the patient is tethered to a pump for an extended time. |
| Tolerance | May cause gastric distension or other intolerance issues if volume is too high. | Generally better tolerated in critically ill patients, especially those with delayed gastric emptying. |
| Risk of Aspiration | Potentially higher risk, especially with large volumes or rapid administration. | Lower risk of aspiration, as smaller, more controlled volumes are delivered over time. |
| Metabolic Response | Can result in pulsatile insulin release, similar to a regular diet. | Provides a constant insulin level, which can sometimes lead to insulin resistance. |
Intermittent Feeding Volumes Across Different Populations
Adults
- Typical Volume: A single intermittent feed for an adult can range from 240 mL to 720 mL, depending on the patient's nutritional goals and tolerance.
- Initial Progression: A common protocol is to start with a smaller volume, such as 125 mL every few hours, and gradually increase the volume per feeding every 8-12 hours until the target volume is reached.
- Customization: The final regimen will be highly individualized. For example, a patient may tolerate 300 mL per feeding four times a day, while another may need 500 mL spread across five feeds.
Children and Infants
- Infants: In the first few weeks, feedings are smaller and more frequent, typically 1.5–3 ounces (45–90 mL) every 2–3 hours for formula-fed newborns. Volumes increase with age and weight. By 6 months, an infant may consume 6–8 ounces (180–230 mL) per feeding, 4–5 times a day.
- Children: As children grow, their volumes increase. A retrospective study in children on intermittent bolus feeding found a median feed volume of 150 mL administered 4 times daily. Pediatric feeding plans are always based on body weight and calculated by a healthcare professional.
Conclusion
The volume of intermittent feeding is not a single value but a dynamic calculation based on a patient's total caloric needs, the formula's concentration, and their individual tolerance. For adults, typical volumes range from 240 mL to 720 mL, administered over 20-60 minutes, several times a day. While intermittent feeding offers advantages like increased mobility and a more physiological meal pattern, it also requires careful management to avoid complications like gastric intolerance or aspiration, especially in high-risk patients. The decision on volume and schedule is best made in consultation with a healthcare team to ensure the patient receives safe and adequate nutrition.
Further Reading
For a deeper look into the physiological and clinical comparisons between intermittent and continuous feeding, consult this review:
Final Thoughts
It is imperative that any changes to an intermittent feeding schedule, including volume adjustments, are made under the direct guidance of a medical professional. Self-adjusting feeding protocols can lead to serious health complications.
