Jeffrey Lewis | Pennsylvania State University (original) (raw)
Papers by Jeffrey Lewis
The Journal of Heart and Lung Transplantation, 2005
Aims: Transplantation of the lung in humans has been marred both by technical problems related to... more Aims: Transplantation of the lung in humans has been marred both by technical problems related to the bronchial anastomosis and by immunological disorders. The objective of this study was to investigate the function of bronchial mucociliary system in transplanted rat lungs with and without the influence of immunosuppression. Methods: Thirty-six rats underwent single-lung transplantation and were divided into two groups which received or not cyclosporin treatment. Cyclosporin was given subcutaneously in doses of 10 mg/kg daily. The rats were sacrificed 2, 15 or 30 days after transplantation. In situ bronchial mucociliary transport (MCT) and ciliary beat frequency (CBF) were determined proximal and distal to the bronchial anastomosis. In vitro mucus transportability and mucus contact angle evaluations were performed to analize the physical properties of the mucus. Results: Oxygenation was significantly better in animals receiving cyclosporin when compared to the no treatment group 15 and 30 days after transplant (pϽ0.001). Significant progressive improvement on MCT, proximal and distal to the anastomotic site, was also found in the cyclosporin treated group at 15 and 30 days. No significant chance in MCT was found in the no treatment group. CBF behavior in the two groups and the physical properties of mucus were similar. As expected histological analysis showed that rejection was significantly higher in the no treatment group (pϽ0.05).
Journal of Biomaterials Applications, 2000
In the present study, we investigate the in vivo and in vitro stability of modified poly(urethane... more In the present study, we investigate the in vivo and in vitro stability of modified poly(urethaneurea) (BioSpan MS/0.4) blood sacs. Blood sacs were utilized primarily in left ventricular assist devices that were implanted in calves for times ranging from 5 to 160 days. Cyclic testing in vitro was also conducted on similar sacs. Various analytical methods were employed to characterize the sacs after in vivo or in vitro service and corresponding retained "control" sacs. These methods included ATR-FTIR spectroscopy, scanning electron microscopy and gel permeation chromatography. In general, the characteristics of implanted and in vitro cycled sacs were similar to their control sacs. Thermal and microtensile properties were unchanged after testing. The same was true for the ATR-FTIR spectra, indicating relative chemical stability for the time frames explored here. The only significant changes occurred in molecular weight and gross surface morphology. A modest increase in weight average molecular weight was observed for most implanted blood sacs, indicating some type of chain extension or branching reaction in vivo. Although the surface morphologies of implanted blood sacs were often similar to their control sacs, we sometimes observed limited pitting on the nonblood contacting surfaces in regions of the sac that experience maximum bending during service.
ASAIO Journal, 2005
In vitro durability testing was conducted on the Penn State/3M electric total artificial heart (E... more In vitro durability testing was conducted on the Penn State/3M electric total artificial heart (ETAH) to determine device durability and to evaluate device failures. A specialized mock circulatory loop was developed for this testing. Customized software continuously acquired data during the test period, and failures were analyzed using FMEA (failure modes and effects analysis) and FMECA (failure modes, effects, and criticality analysis) principles. Redesigns were implemented when appropriate. Reliability growth principles were then applied to calculate the 1 and 2 year reliability. The 1 and 2 year reliability of the Penn State/3M ETAH was shown to be 96.1% and 59.9%, respectively, at 80% confidence.
The Annals of Thoracic Surgery, 1998
long-term, mechanical circulatory support systems. The recommendation includes a definition of sy... more long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.
The Annals of Thoracic Surgery, 2001
Management of patients with end-stage cardiac disease remains a vexing problem. Limitations in me... more Management of patients with end-stage cardiac disease remains a vexing problem. Limitations in medical management and a fixed supply of donor organs for cardiac transplant have a continued impact on this growing population of patients. Mechanical circulatory support has proved very successful as a means of bridging patients to cardiac transplant when all medical options have been exhausted. The development of a chronic system of circulatory support has been underway at the Pennsylvania State University for nearly 30 years. These efforts have been recently merged with the industrial partnership with Arrow International toward the development of the LionHeart LVD-2000 (Arrow International, Reading, PA) completely implanted left ventricular support system. We present an overview of the system, details of implantation, a review of preclinical studies, and a synopsis of the first European implants. Early results have demonstrated the system to be safe, effective, and reliable. Transcutaneous energy transmission and the compliance chamber have been validated.
The Journal of Heart and Lung Transplantation, 2005
Aims: Transplantation of the lung in humans has been marred both by technical problems related to... more Aims: Transplantation of the lung in humans has been marred both by technical problems related to the bronchial anastomosis and by immunological disorders. The objective of this study was to investigate the function of bronchial mucociliary system in transplanted rat lungs with and without the influence of immunosuppression. Methods: Thirty-six rats underwent single-lung transplantation and were divided into two groups which received or not cyclosporin treatment. Cyclosporin was given subcutaneously in doses of 10 mg/kg daily. The rats were sacrificed 2, 15 or 30 days after transplantation. In situ bronchial mucociliary transport (MCT) and ciliary beat frequency (CBF) were determined proximal and distal to the bronchial anastomosis. In vitro mucus transportability and mucus contact angle evaluations were performed to analize the physical properties of the mucus. Results: Oxygenation was significantly better in animals receiving cyclosporin when compared to the no treatment group 15 and 30 days after transplant (pϽ0.001). Significant progressive improvement on MCT, proximal and distal to the anastomotic site, was also found in the cyclosporin treated group at 15 and 30 days. No significant chance in MCT was found in the no treatment group. CBF behavior in the two groups and the physical properties of mucus were similar. As expected histological analysis showed that rejection was significantly higher in the no treatment group (pϽ0.05).
Journal of Biomaterials Applications, 2000
In the present study, we investigate the in vivo and in vitro stability of modified poly(urethane... more In the present study, we investigate the in vivo and in vitro stability of modified poly(urethaneurea) (BioSpan MS/0.4) blood sacs. Blood sacs were utilized primarily in left ventricular assist devices that were implanted in calves for times ranging from 5 to 160 days. Cyclic testing in vitro was also conducted on similar sacs. Various analytical methods were employed to characterize the sacs after in vivo or in vitro service and corresponding retained "control" sacs. These methods included ATR-FTIR spectroscopy, scanning electron microscopy and gel permeation chromatography. In general, the characteristics of implanted and in vitro cycled sacs were similar to their control sacs. Thermal and microtensile properties were unchanged after testing. The same was true for the ATR-FTIR spectra, indicating relative chemical stability for the time frames explored here. The only significant changes occurred in molecular weight and gross surface morphology. A modest increase in weight average molecular weight was observed for most implanted blood sacs, indicating some type of chain extension or branching reaction in vivo. Although the surface morphologies of implanted blood sacs were often similar to their control sacs, we sometimes observed limited pitting on the nonblood contacting surfaces in regions of the sac that experience maximum bending during service.
ASAIO Journal, 2005
In vitro durability testing was conducted on the Penn State/3M electric total artificial heart (E... more In vitro durability testing was conducted on the Penn State/3M electric total artificial heart (ETAH) to determine device durability and to evaluate device failures. A specialized mock circulatory loop was developed for this testing. Customized software continuously acquired data during the test period, and failures were analyzed using FMEA (failure modes and effects analysis) and FMECA (failure modes, effects, and criticality analysis) principles. Redesigns were implemented when appropriate. Reliability growth principles were then applied to calculate the 1 and 2 year reliability. The 1 and 2 year reliability of the Penn State/3M ETAH was shown to be 96.1% and 59.9%, respectively, at 80% confidence.
The Annals of Thoracic Surgery, 1998
long-term, mechanical circulatory support systems. The recommendation includes a definition of sy... more long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.
The Annals of Thoracic Surgery, 2001
Management of patients with end-stage cardiac disease remains a vexing problem. Limitations in me... more Management of patients with end-stage cardiac disease remains a vexing problem. Limitations in medical management and a fixed supply of donor organs for cardiac transplant have a continued impact on this growing population of patients. Mechanical circulatory support has proved very successful as a means of bridging patients to cardiac transplant when all medical options have been exhausted. The development of a chronic system of circulatory support has been underway at the Pennsylvania State University for nearly 30 years. These efforts have been recently merged with the industrial partnership with Arrow International toward the development of the LionHeart LVD-2000 (Arrow International, Reading, PA) completely implanted left ventricular support system. We present an overview of the system, details of implantation, a review of preclinical studies, and a synopsis of the first European implants. Early results have demonstrated the system to be safe, effective, and reliable. Transcutaneous energy transmission and the compliance chamber have been validated.