SUPPLEMENT
Frequency-Modulated Orocutaneous Stimulation Promotes Non-nutritive Suck Development in Preterm Infants with Respiratory Distress Syndrome or Chronic Lung Disease, and Preterm Infants of Diabetic Mothers
SM Barlow1-4, J Lee5, Jingyan Wang1, Austin Oder1 , Sue Hall6, Kendi Knox6, Kathleen Weatherstone7 and Diane Thompson7
1Department of Speech-Language-Hearing: Sciences and Disorders,
2Programs in Neuroscience, 3Human Biology, and 4Bioengineering, 5Center for Research Methods and Data Analysis, University of Kansas, Lawrence, Kansas USA, 6Stormont-Vail HealthCare, Topeka, Kansas USA, and 7Overland Park Regional Medical Center, Overland Park, Kansas USA.
*Address Editorial Correspondence to:
Dr. Steven M. Barlow
1315 Wakarusa Drive, Suite 120
University of Kansas
Lawrence, KS 66049 USA
Online Supplement
Methods
Patterned orosensory stimulus generation
The orocutaneous stimulation was delivered by a servo-controlled pneumatic amplifier (NTrainer System, Innara Health, Inc., Shawnee, KS USA) specially designed to transmit repeating pneumatic pulse trains to the soft tissues of the infant’s lips-anterior tongue-intraoral mucosa-jaw through a regular (green) Soothie™ silicone pacifier. This 6-cycle orocutaneous stimulus burst was frequency modulated, consisting of sequential cycle periods of 510, 526, 551, 580, and 626 ms with an intertrain interval of 2 seconds (see Figure 1).1 The spatiotemporal features of this somatosensory stimulus mimic the synchronous volleys of afference associated with ororhythmic patterning, and thus constitutes an approximation to a physiologically salient somatosensory experience normally encoded by the trigeminal system. The pressure rise-fall time (10-90% intercepts) of each 50-ms pulse was 31 milliseconds, and the resultant displacement at the pacifier-lip/tongue tissue interface was approximately 400 µm.
Automated NNS digital signal processing and feature extraction
A 2-minute subsample reflecting the most active period of NNS oromotor behavior was automatically extracted from each 3-minute suck assessment data file using a custom designed waveform signal process-feature extraction algorithm coded in Objective C and executed on the NTrainer System®. To prepare the data for NNS identification, a two-stage filtering process is completed which includes (1) a high-pass (fc=0.5 Hz) operation on the raw pressure waveform to remove low frequency (DC) offsets due to tongue/jaw posturing and thermal drift imposed by the infant’s contact on the pacifier bulb, and (2) a first order low pass filter (fc=20 Hz) to remove high-frequency jitter from the pressure waveform. Pressure peaks with amplitudes greater than 1.67 cmH2O were subject to feature extraction criteria, including NNS symmetry (ratio of leading and trailing half-height amplitudes), individual cycle duration, and trailing pressure inflection. Identified NNS events are passed in an array to an NNS burst collector which groups NNS events and sorts them based on peak pressures.
References
- Barlow SM, Urish M, Venkatesan L, Harold M, & Zimmerman E. (2012). Frequency modulation (FM) and spatiotemporal stability of the sCPG in preterm infants with RDS. International Journal Pediatrics, doi: 10.1155/2012/581538.
Figure legend.
Figure 1. Frequency modulated (FM) somatosensory stimulus bursts as presented to the preterm infants through a pneumatically-charged silicone pacifier. Each burst consists of 6 pulses followed by a 2-second pause period. A servo-controlled microprocessor provides the gating function (top panel) to dynamically ‘charge’ the intraluminal pressure of the silicone pacifier (middle panel) resulting in rapid conformational changes in pacifier geometry (bottom panel). The peak-to-peak displacements associated with these pressure changes is approximately 400 microns with a 10-90% rise/fall time of 31 milliseconds.