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University of Pittsburgh Senior Design – BioE 1160. Pressure Sensing Transseptal Cannula for use with TandemHeart ™ PTVA System. Project Advisors: David H.J. Wang, Ph.D. Douglas E. Smith, Ph.D. Dennis Kopilec Marlin H. Mickle, Ph.D.
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University of Pittsburgh Senior Design – BioE 1160 Pressure Sensing Transseptal Cannula for use with TandemHeart™ PTVA System Project Advisors:David H.J. Wang, Ph.D.Douglas E. Smith, Ph.D.Dennis KopilecMarlin H. Mickle, Ph.D. Team Members:Mihoko HashimotoLauren KokaiNitin NarayanaKatie O’Callaghan February 17, 2004
Overview Problem: Unmonitored changes in LA pressure of patients on the TandemHeart™ PTVA System (below a certain pressure threshold) may pose a threat to the patient due to a potential “suck down” of tissue (overdrainage of LA). This causes tissue damage and reduced blood flow. Solution: Real time pressure readings in the LA can possibly prevent the tissue “suck down”. • Incorporate a pressure sensor into the tip of the Transseptal Cannula along with the use of either RF-technology or wire attachment for signal transmission. • Effectively determine an appropriate pump speed depending on patient’s conditions without further invasive processes.
Original Goals The ultimate goal is to enable real-time measurements of Left Atrial Pressure (LAP) with TandemHeart use, by placing an absolute pressure sensor chip at the tip of the cannula. + Study the feasibility of the incorporation of RF transmitter complex to transmit the real-time measurements without need for wiring. High Level Timing Goals • Analysis of pressure sensor properties & manufacturing limitations • Establish that device redesign meets PDS under simulated clinical use conditions
Original Personal Responsibilities Project Criteria: Milestone 1 (30%) Milestone 2 (30%) Milestone 3 (10%) Milestone 4 (10%) Milestone 5 (5%) Milestone 6 (7.5%) Milestone 7 (7.5%)
Updated Schedule / Goals • Feasibility • Pressure sensor comparison report • Summaries of regulatory considerations • Preliminary Prototype Design • Assemble preliminary prototype sketch/drawing of cannula redesign • Design circuit; assess power source options circuit diagram • Preliminary Prototype Testing • Test sensor accuracy for intended range of use • Test for quick response time • Simulate suction conditions & characterize sensor response
Deliverables • Pressure sensor comparison chart • Summary of regulatory considerations • Drawing of preliminary prototype • Circuit diagram • Test Protocols & Test Reports for all tests conducted on prototype • DHF • SBIR application • 510(k) application?
Completed Tasks • Pressure Sensor Product Summary Comparison Chart • FDA regulations regarding pressure sensing catheter • 21 CFR § 870.2870 – Catheter tip pressure transducer • 21 CFR § 870.2850 – Extravascular blood pressure transducer • 21 CFR § 870.2060 – Transducer signal amplifier and conditioner • 21 CFR § 870.1110 – Blood pressure computer • FCC regulations regarding intentional emission of RF • “Regulations pertaining to intentional emitters for the purpose of energy harvesting” • “Passive E-Field Telemetry: A new wireless transmission principle in minimally Invasive Medicine” Neukomm et al. • 47 CFR § 2.1093 – Radio frequency radiation exposure evaluation: portable devices • OET Bulletin No.65, Evaluating Compliance with FCC Guidelines for Human Exposure to Radio frequency Electromagnetic Fields • EMC (Electromagnetic Compatibility) considerations • “Electromagnetic Compatibility in Medical Equipment: A Guide for Designers and Installers” (Kimmel and Gerke)
FCC Regulatory Summary The FCC limits the maximum permissible exposure limits for the maximum rate at which energy can be transferred to a square cm of a person’s body over a period of time. • For occupational/controlled exposure (100 kHZ – 6 GHz) • Average limit for occupational/controlled exposure is 0.4 W/kg over the whole-body and spatial peak specific absorption rate not exceeding 8 W/kg as averaged over any 1 gram of tissue (defined as a tissue volume in the shape of a cube). (47 CFR § 2.1093) • Predicted calculations for RF field strength (PG) and power density adhere to the following equations (single radiating antenna/worst-case prediction): • S = PG / πR2 (S = power density; P = power input to antenna; G = power gain of antenna; R = distance to the center of radiation)
Further Information Needed Re: RF • Identify RF transmitter supplier • Determine sampling frequency (.1 – 2 Hz) • Determine required signal strength for signal transmission through chest cavity
Project Successes to Date • Identified fiber optics pressure transducer (FISO FOP-MIV) and contacted company for sample • Comparison evaluation of several other possible pressure sensors • Obtained Motorola chip and transducer testing circuit • Progress on regulatory considerations (FCC, FDA, EMF) • Updated DHF documents
Wrenches in the Works • Communication: slow response from companies regarding system elements • Budget