A pilot study for optimising nutrition delivery using a smart feeding tube in healthy volunteers

Intervention This is a single-arm intervention study that uses an innovative dual pressure sensing nasogastric feeding tube system to measure biofeedback from the gut to optimise the safe delivery of enteral feed. A custom-engineered feeding tube system measures back-propagated pressure and solid-state pressure by employing two pressure sensors attached to a single tube. Back-propagated pressure will be an external measurement of the gut pressure. A pressure transducer is placed between the feeding pump giving set and the feeding tube to measure the intraluminal pressure via back-propagation through the feed filling the feeding tube’s lumen. Solid-state pressure will be an internal measurement of the gut pressure. A microtip pressure sensor will be passed through the lumen of the feeding tube to directly measure intraluminal pressure at the distal end of the feeding tube where the feed exits. Gastric electrophysiology will be mapped by placing an FDA-approved 64-electrode array over the abdomen. Bowel sounds will be recorded by placing two digital stethoscopes on each side of the median plane. Cardiac and respiratory rate measurements will be taken with a three lead ECG. Protocol The study will be conducted at the Clinical Research Centre located at the University of Auckland. 1. Participants will visit the clinic in after an overnight fast (>8hours), nil-by-mouth. 2. Anthropometrics will be measured. 3. Prior to inserting the feeding tube, the solid-state (Millar®) pressure sensor will be incorporated into the nasogastric tube. It will be 2cm less than full insertion, so that the sensor unit is fully within the tube and not exposed in the hole at the end of the tube, to avoid the risk of it being snagged during insertion. 4. The nasogastric feeding tube will then be inserted via the nose into the stomach (without anaesthesia) as per the Auckland City Hospital clinical guidelines for enteral tube management. Participants will sit in an upright position with the head kept straight. The length of the tube will be measured and marked from the tip of the nose to ear lobe and then down to the xiphoid process. The end of the tube will be lubricated with a gel, and the tube inserted from the nose until the marked length is reached. The participant will be offered a glass of water to assist passage of tube through the oro-pharynx. The tube will be strapped and secured at the top of the nose using a plaster. 5. Correct positioning of the feeding tube will be confirmed by testing the pH of the gastric aspirate. 6. The Millar sensing unit will be advanced the final 2cm, to allow the sensor to be exposed within the terminal hole of the tube without extending into the stomach lumen. 7. Following the feeding tube insertion, three standard ECG dots will be applied to the participants chest and abdomen. The ECG dots will be connected to a signal processing unit (ProtoCentral Electronics) and a data acquisition unit to interpret the cardiac and respiration rate measurements. 8. Next, a body surface gastric mapping (BSGM) electrode adhesive array (Alimetry®) will be placed over the skin on the stomach region (as per Alimetry’s protocol) by asking the participants to lie in a supine position. 9. Following the BSGM electrode array placement, two digital stethoscopes (Thinklabs Medical LLC®) will be placed on the participants’ abdomen area for recording bowel sounds. Stethoscopes will be placed one on each side of the median plane, positioned in the mid-clavicular line, and at least one centimetre below the lower edge of the BSGM electrode array. The stethoscopes will be connected to a digital recorder for dual bowel sounds recording from the left and right abdominal quadrants. Measurements Measurements will be done at eight timepoints over approximately 75-90 minutes. The measurements will include intraluminal pressure (via the prototype NG tube), gastric mapping (by BSGM), heart rate and respiratory rate (by three lead electrocardiogram (ECG)), and bowel sounds (via a digital stethoscope). For timepoints 1-3, participants will lie in the supine position to measure the effects of feeding. • Timepoint 1: Once the participant lies on the bed, all the recording devices will be turned on. After a devices ‘warm-up’ period of 15 minutes, fasting baseline measurements will be taken for 10 minutes. • Timepoint 2: The feeding tube will then be adjusted (advanced 5cm and withdrawn 2cm) and measurements repeated for 5 minutes. • Timepoint 3: An enteral feed (Nutricia®) will be given at a rate of 400 mL/hour for 15 minutes (total energy content 150 kcal). After 15 minutes, the feeding pump will be turned off. Measurements will be recorded for 10 minutes. The recordings for timepoints 4-8 will measure the effects of body movement. The feeding pump will be off for the following measurements. • Timepoint 4: Participants will be asked to turn to their side (right side down) from supine position and 5 minutes of measurements recorded. • Timepoint 5: Participants will be sat up (60 - 90 degrees from horizontal) and 5 minutes of measurements recorded. • Timepoint 6: Participants will be asked to cough for 15 seconds, and measurements continued through this period. • Timepoint 7: Participants will be asked to perform Valsalva’s manoeuvre for 30 seconds and measurements continued through this period. • Timepoint 8: Participants will resume supine position (as in Time point 1) and a further 10 minutes of measurements will be taken. After completion of this protocol the feeding tube, BSGM electrode array, and stethoscope attachments will be carefully removed.