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Biomedical subjects

T J Gardner

Publications and source records attributed to T J Gardner.

At least 19 recordsLinked to original sources
PubMed2003

Experimental support for a model of birdsong production.

In this work we present an experimental validation of a recently proposed model for the production of birdsongs. We have previously observed that driving the model with simple functions of time, which represent tensions in vocal muscles, produces a wide variety of sounds resembling birdsongs. In this work we drive the model with functions whose time dependence comes from recordings of muscle activities and air sac pressure. We simultaneously recorded the birds' songs and compared them with the synthetic songs. The model produces recognizable songs. Beyond finding a qualitative agreement, we also test some predictions of the model concerning the relative levels of activity in the gating muscles at the beginning and end of a syllable.

Air Sacs↗
PubMed2001

Influencing the political process for cardiothoracic surgeons.

Medicare was established by congressional legislation to provide excellent health care for all older US citizens. The economic viability of Medicare is in question, however, and the possibility of reduced services or program curtailments has been raised. To ensure appropriate support for our professional goals, as thoracic surgeons we must articulate our professional needs and expectations for continued medical progress.

Health Policy↗
PubMed2001

New paradigms and improved results for the surgical treatment of acute type A dissection.

OBJECTIVE: To examine the effect of an integrated surgical approach to the treatment of acute type A dissections. SUMMARY BACKGROUND DATA: Acute type A dissection requires surgery to prevent death from proximal aortic rupture or malperfusion. Most series of the past decade have reported a death rate in the range of 15% to 30%. METHODS: From January 1994 to March 2001, 104 consecutive patients underwent repair of acute type A dissection. All had an integrated operative management as follows: intraoperative transesophageal echocardiography; hypothermic circulatory arrest (HCA) with retrograde cerebral perfusion (RCP) to replace the aortic arch; HCA established after 5 minutes of electroencephalographic (EEG) silence in neuromonitored patients (66%) or after 45 minutes of cooling in patients who were not neuromonitored (34%); reinforcement of the residual arch tissue with a Teflon felt "neo-media"; cannulation of the arch graft to reestablish cardiopulmonary bypass at the completion of HCA (antegrade graft perfusion); and remodeling of the sinus of Valsalva segments with Teflon felt "neo-media" and aortic valve resuspension (78%) or replacement with a biologic or mechanical valved conduit (22%). RESULTS: Mean age was 59 +/- 15 (range 22-86) years, with 71% men and 13% redo sternotomy after a previous cardiac procedure. Mean cardiopulmonary bypass time was 196 +/- 50 minutes. Mean HCA with RCP time was 42 +/- 12 minutes (range 19-84). Mean cardiac ischemic time was 140 +/- 45 minutes. Eleven percent of patients presented with a preoperative neurologic deficit, and 5% developed a new cerebrovascular accident after dissection repair. The in-hospital death rate was 9%. Excluding the patients who presented neurologically unresponsive or with ongoing cardiopulmonary resuscitation (n = 5), the death rate was 4%. In six patients adverse cerebral outcomes were potentially avoided when immediate surgical fenestration was prompted by a sudden change in the EEG during cooling. Forty-five percent of neuromonitored patients required greater than 30 minutes to achieve EEG silence. CONCLUSION: The authors have shown that the surgical integration of sinus segment repair or aortic root replacement, the use of EEG monitoring, partial or total arch replacement using RCP, routine antegrade graft perfusion, and the uniform use of transesophageal echocardiography substantially decrease the death and complication rates of acute type A dissection repair.

Adult↗
PubMed2000

Blocking free radical production via adenoviral gene transfer decreases cardiac ischemia-reperfusion injury.

Periods of cardiac ischemia followed by reperfusion can lead to either transient loss of function (stunning) or permanent functional loss stemming from infarction, depending upon the length of the ischemic period. In either case the primary mediator of the injury may by oxygen-derived free radicals generated upon the reestablishment of blood flow. The heart's primary defense against peroxide, glutathione peroxidase, is depleted during ischemia. Thus, the ischemic myocardium might derive significant protection from increased levels of the enzyme, catalase, which can remove hydrogen peroxide in a redox-independent manner. To test these assertions, we studied the ability of adenoviral gene transfer to increase intracellular antioxidant activity via catalase expression. What we observed was that increasing catalase activity in the heart was sufficient to prevent the stunning associated with 15 min of ischemia followed by reperfusion.

Adenoviridae↗
PubMed2000

Cardiothoracic intensive care: operation and administration.

The cardiothoracic surgery intensive care unit (CTICU) has evolved as a separate entity from the general surgical intensive care unit as management for cardiac surgery patients has become streamlined and algorithm driven. Critical care is best managed when the service is designed for a homogeneous population with a circumscribed set of medical and surgical issues. The repetition involved with the subspecialty care allows health care providers such as primary care nurses, nurse practitioners, physician assistants, and other ancillary services to become appropriately focused on issues pertinent to this population. The goals of the CTICU include the attainment of rapid and safe recovery from surgery and anesthesia despite decreasing resources, increasing patient age and comorbidity, and increasing complexity of the operative procedure. The coordinated and systematic approach to the postoperative cardiac surgery patient under the direction of a staff physician offers the most effective opportunity to achieve these expectations at this time. The traditional model of staffing by a physician with responsibilities that conflict temporally with the immediacy often needed for the postoperative care of cardiac patients may expose patients to unnecessary risks. A responsible physician should be available in the CTICU, especially during the immediate postoperative period when physical assessment and direct hands-on involvement are essential. In an era when the operative team (ie, cardiac surgeon and cardiac anesthesiologist) must return to the surgical suite soon after the patient arrives in the intensive care unit, the presence of a physician dedicated to postoperative medical and surgical management becomes mandatory. According to the Joint Commission on Accreditation of Healthcare Organizations, "Each special care unit is properly directed and staffed according to the nature of the special patient care needs anticipated and scope of services provided." The assignment of staff is designed to match experience with patient acuity.

Cardiac Surgical Procedures↗