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Neonatal Transport Incubator: Vibration Identification, Ranking, and Attenuation—A Novel Approach to Patient Tray Stabilization

Sallee, Wayne MS; Bentley, Anthony BSN, RN; Walding, David BS; Christofi, Costas PhD

doi: 10.1097/JCE.0000000000000156
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The Texas Children’s Hospital (TCH) Biomedical Engineering Department, in conjunction with the Kangaroo Crew and Nursing departments, strive to increase the quality of patient care through research and innovation. The TCH has been engaged in a comprehensive research campaign to characterize the type of mechanical forces that the neonate would experience in a transport incubator on a typical neonatal transport. After several years of measuring vibration forces during in-hospital (J Clin Eng. 2008:74-77), ambulance, and air transportation modalities, it was determined that our core need was to conduct forced vibration tests of the transport incubator in a simulated environment using a large shaker table (Space Act Agreement no. SAA-EA-09-006 with TCH Biomedical Engineering, TCH contract no. NAS-04539, National Aeronautics and Space Administration, Washington, DC). Also, to identify the natural frequencies, mode shapes, and damping ratios of the neonatal incubator system, experimental modal analysis (EMA) and operating deflection shape analysis were performed. In 2009, TCH was awarded a Space Act Agreement with National Aeronautics and Space Administration Johnson Space Center to analyze the transport incubator at Johnson Space Center’s Vibration and Acoustic Test Facility (Houston, Texas). Over the next 2 years (during nonpeak operational times), random and sine sweep excitation tests, EMA, and operating deflection shape analysis tests were performed to aid in the understanding of the dynamics of the TCH incubator and its modal properties (Space Act Agreement no. SAA-EA-09-006 with TCH Biomedical Engineering, TCH contract no. NAS-04539, National Aeronautics and Space Administration, Washington, DC). Sine-sweep and EMA test results point to dominant patient tray natural frequencies of 8 to 10 Hz and a vibration magnification factor of 1.60 and 3.75 at patient tray and at neonatal mannequin, respectively. The EMA results showed the tray first mode (drum mode) with maximum deflection at the tray center. Our goal was to look at ways to stabilize the patient tray and measure vibration attenuation using a common inexpensive measurement device (iPhone 5). The model 20H International Biomedical transport incubator was fitted with an accelerometer at patient tray center and the incubator was pushed over several floor transitions during 4 trials for modified and unmodified incubator. When the patient tray was tethered to a rigid frame, vibration attenuation for Z_min, Z_max, and Z_rms was 78%, 193%, and 65%, respectively.

Corresponding author: David Walding, BS, Department of Biomedical Engineering, Texas Children’s Hospital, 6621 Fannin St, Ste A6685, Houston, Texas 77030. He can be reached at dlwaldin@texaschildrens.org.

David Walding, BS, is a specialist in anesthesia and pulmonary systems in the Department of Biomedical Engineering at Texas Children’s Hospital in Houston.

Wayne Sallee, MS, is a Master’s intern in the Department of Biomedical Engineering at Texas Children’s Hospital in Houston.

Anthony Bentley, BSN, RN, is with the Kangaroo Crew, Innovative Solutions Council, at Texas Children’s Hospital in Houston.

Costas Christofi, PhD, is with Barrios Technology, NASA JSC VATF Lab, in Houston, Texas.

The authors have no conflicts of interest.

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