Measuring Diaphragm Electrical Activity in Neonates Using a Smaller Inter-electrode Distance

Neurally Adjusted Ventilatory Assist (NAVA) is a mode of ventilation where the electrical activity of the diaphragm (EDI) - a signal representing the baby's respiratory drive - is used to control the timing and amount of assist provided. NAVA was introduced to the market in 2007 and since has been used in more than 40 countries. In the current clinical practice, the Edi signal from the patient is captured with miniature sensors (the size of a hair) embedded in the wall of a specially designed naso/orogastric feeding tube. This FDA and Health Canada approved, commercially available catheter (Getinge, Solna, Sweden), is 6 Fr in size (outer diameter), 49 cm in length and has 8 pairs of sensors that are placed 6 mm apart (so-called inter electrode distance (IED) is 6 mm). While no obvious side effects have been noted by clinicians, for the smallest of neonates, the currently used commercial catheter (size 6F, 49 cm long) may have 'excessive' post-array catheter length. In these neonates, typically those with weight \< 1000 grams, following the correct placement of catheter as per the electrode array positioning at gastro-esophageal junction, the feeding holes in the catheter may end at the level of distal stomach instead of the desirable mid-stomach location. The changing demographics of the patients in the Neonatal Intensive Care Units (NICU) has created a clinical need to redesign the currently used Edi catheter specifically to suit the smallest of patients, such that following adequate placement the feeding holes sit at the level of mid-stomach. Drs. Christer Sinderby and Jennifer Beck in Toronto, Canada, are the original designers of the 6 mm/49 cm currently used Edi catheter. These investigators (at St-Michael's Hospital, Toronto) in collaboration with their team at Neurovent Research Inc. (NVR) have re-designed and invented a new prototype of the current FDA-approved catheter specifically suited for use in extreme premature neonates. They have done so by reducing the interelectrode distance from the originally set 6 mm to 4 mm, which reduces the overall insertion depth to capture the same signal from the diaphragm. All other parameters are exactly same as the original catheter (6F, 49 cm long). In this small feasibility study the investigators wish to provide a clinical proof of concept for the use of this newly designed prototype in 10 extremely premature neonates who are already receiving NAVA ventilation in the NICU.