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Home > What's Next > Impedance Threshold Device (ITD) Research and Information:

Impedance Threshold Device (ITD) Research and Information

Introduction

A researcher, Dr. Victor Convertino, for g-suits and Orthostatic Intolerance (OI) has been studying something called an Impedance Threshold Device (ITD). He says, "It works on the principle that breathing against a small resistance during inspiration produces greater negative pressure within the thorax, which in turn acts as an effective vacuum to return blood to the heart and brain." It is an interesting concept. It is a small hand-held breathing device. Maybe it will become like an asthma inhaler for OI. I think it may be the Orthostatic Intolerance treatment of the future.

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An ITD Restores Circulation

The ResQPOD® Circulatory Enhancer [also known as an Impedance Threshold Device (ITD)] restores circulation, naturally. The non-invasive device treats low blood pressure [hypotension] and enhances circulation. It increases blood flow to the heart each time a person inspires (breathes) through the device by offering a small, but tolerable, amount of resistance. This resistance creates a small vacuum within the chest, which draws more blood back to the heart. The new device has been used to increase blood pressure in patients who develop hypotension from a number of different causes, including renal dialysis, orthostatic hypotension, blood loss, and dehydration.

Copyright © 2007, Advanced Circulatory Systems, Inc.

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An ITD was Developed for Cardiac Arrest/CPR

The ResQPOD is manufactured by Advanced Circulatory Systems Inc. (Minneapolis, MN). The company began developing the ResQPOD technology in 1997. The company's founder, Dr. Keith Lurie, a cardiologist, originally developed the ResQPOD for use with cardiac arrest patients to improve circulation during the administration of cardiopulmonary resuscitation (CPR). Several clinical studies have been performed to demonstrate that the ResQPOD's ability to help increase circulation during the administration of CPR results in higher survival rates for cardiac arrest patients. Over 500 hospitals and emergency medical systems in the United States use the device for use with cardiac arrest patients.

Copyright © 2007, Advanced Circulatory Systems, Inc.

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An Impedance Threshold Device is Used for Orthostatic Intolerance

During the development of the ResQPOD for use with cardiac arrest patients, the company discovered that there were many spontaneously breathing patients that might benefit from the same technology. This led to the company's research with dialysis patients, orthostatic hypotension patients, and other patients with poor circulation resulting from a variety of other clinical conditions. Several of the company's studies have been performed with NASA. Astronauts routinely suffer from low blood pressure when they return to earth and are reintroduced to gravity. This causes light-headedness, difficulty walking and sometimes fainting. Based on the research performed with NASA, NASA's medical team has added the ResQPOD to the list of therapies available for use with the astronauts upon their return to earth.

Copyright © 2007, Advanced Circulatory Systems, Inc.

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How I Use an Impedance Threshold Device for Orthostatic Intolerance

Shortly before I launched this website, I had the opportunity to try the ITD. It seems to work for me, too. I started by trying to keep an eye on myself and use the ITD all day based on how I was feeling. I have since changed to using it every 10 to 15 minutes and during Orthostatic Intolerance (OI) moments and that is much easier for me. I bought a watch with a repeating timer to remind me to use the ITD regularly throughout the day. I take slow, deep breaths. I try to inhale for about 2.5 seconds. Each time, I take about 5-7 breaths to total 30 seconds. I also bought a pouch that hooks to the waist of my g-suit so that I can have the ITD with me and easy to get to at all times. I think I am seeing improvements already because of the ITD, but I still have to figure out what combination of the g-suit, Impedance Threshold Device, and other treatments for Orthostatic Intolerance (OI) will work best for me.

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Picture of ITD

Impedance Threshold Device (ITD) with facemask

Impedance Threshold Device (ITD) with a clear facemask

ITD Circulatory Enhancer sheet by Advanced Circulatory Systems, Inc.
This is in PDF/Adobe Acrobat format. (987 KB)
The picture of the ITD with a facemask is on the left side of the page.
The ITD (orange part) can be used with a small mouthpiece instead of a facemask or by itself without either.

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Newspaper Article about ITD

Brain-Blood Booster by Brady Averill
Minneapolis Star Tribune - September 21, 2006
This is in PDF/Adobe Acrobat format. (393 KB)

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Where to Buy an Impedance Threshold Device (ITD)

Links in this section will open in a new window.

Advanced Circulatory Systems, Inc. -

  • Invented, develops, designs, researches, manufactures, and markets ITDs.
  • For product inquiries and ordering information, please contact them through their website:
    www.advancedcirculatory.com

Note: A doctor's prescription for an ITD is required to place an order. Contact Advanced Circulatory Systems, if you need assistance in getting a prescription.

The product used for Orthostatic Intolerance (OI) is now called a ResQGARD.

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Research Articles about Impedance Threshold Device (ITD)

These are in PDF/Adobe Acrobat format.

  • Restoration of central blood volume: application of a simple concept and simple device to counteract cardiovascular instability in syncope and hemorrhage (283 KB)

    Victor A. Convertino, William H. Cooke, and Keith G. Lurie

    INTRODUCTION The inability to tolerate upright standing posture due to development of severe orthostatic hypotension and syncope is a clinical problem that has plagued astronauts and military personnel in their austere operational environments as well as millions of people worldwide. More critically, hemorrhagic shock remains a leading cause of death in both civilian and battlefield trauma. Central hypovolemia and cardiovascular collapse (insufficiency) are the common features shared by syncope and hemorrhagic shock. It is therefore clear that the development of an effective countermeasure against the onset of syncope or hemorrhagic shock should focus on the simple concept of functionally restoring central blood volume. Although replacing blood or fluids may be beneficial in a clinical setting, it can prove impossible in operational settings such as a spacecraft and battlefields.

    One of the primary mechanisms that contribute to syncope or hemorrhagic shock is the reduction in cardiac filling and stroke volume (SV). Therefore, any therapeutic approach that is designed to increase venous return and SV should be an effective countermeasure against cardiovascular collapse. Increased negative intrathoracic pressure during spontaneous inspiration represents a natural mechanism for enhancing venous return and cardiac filling. Taking advantage of this simple concept, the development and application of a resistance device applied during spontaneous inspiration has been shown to cause an immediate increase in arterial blood pressure when applied in different animal and clinical models associated with significant life-threatening hypotension [12-16]. This device has been named the impedance threshold device (ITD; Fig. 1). With its design, the inspiratory resistance induced by the ITD results in a greater vacuum within the thorax during each inspiration, and subsequently enhances venous return and preload to the heart [12,14-16].

    The purpose of this paper is to review observations made from a series of experiments in our laboratory that focus on affecting hemodynamic responses by application of an ITD during conditions of central normovolemia and hypovolemia in human subjects. Specifically, results from human subjects exposed to supine rest, orthostatic challenge, and central hypovoleniia will be used to provide insight into relationships between regulation of blood pressure and flow, and functional performance. . .

    . . . In summary, the ITD is FDA-approved as a circulatory enhancer intended for the treatment of relative hypovolemia and hypotension suffered by people as a result of reduced central blood volume. The ITD is lightweight, easy to use, durable, relatively inexpensive, and well tolerated. It could be easily carried by an astronaut, added to a civilian or combat medic's bag, or could travel easily onto the battlefield with every soldier. As such, use of the ITD may "buy time" by providing a critical bridge to more definitive repair of the primary injury and ultimate survival.
    Read more.

    From the U.S. Army Institute of Surgical Research, Fort Sam Houston, TX 78234 (V.A. Convertino and W.H. Cooke); Advanced Circulatory Systems, Inc., and University of Minnesota, Minneapolis, MN 44455 (K.G. Lurie).

    Copyright © 2005, Victor A. Convertino, PhD.
     
  • Inspiratory Resistance as a Potential Treatment for Orthostatic Intolerance and Hemorrhagic Shock (3.1 MB)

    Victor A. Convertino, William H. Cooke, and Keith G. Lurie

    Aviation, Space, and Environmental Medicine - Vol. 76, No. 4 - April 2005 pages 319-325

    Loss of consciousness due to central hypovolemia can occur due to sudden cardiovascular decompensation in normal individuals or hypovolemic shock in wounded patients. A variety of devices have been developed to sustain perfusion to the brain including anti-G suits worn by pilots and returning astronauts and applied to patients as "shock trousers." However, all countermeasures developed to date suffer from problems that limit their utility in the field. An "impedance threshold device" (ITD) has recently been developed that acutely increases central blood volume by forcing the thoracic muscles to develop increased negative pressure, thus drawing venous blood from extrathoracic cavities into the heart and lungs. We review here a series of experiments that demonstrate the application of the ITD to a variety of experimental conditions, including its use to: 1) increase heart rate, stroke volume, and arterial BP in normovolemia and hypovolemia; 2) increase cerebral blood flow velocity; 3) reset cardiac baroreflex function to a higher operating range for BP; 4) lower intracranial pressure; and 5) reduce orthostatic symptoms. In this brief review, we present evidence which supports further consideration of using inspiratory resistance as a countermeasure against circulatory collapse associated with orthostatic instability and hemorrhagic shock.
    Read more.

    From the U.S. Army Institute of Surgical Research, Fort Sam Houston, TX (V.A. Convertino and W.H. Cooke); Advanced Circulatory Systems, Inc., and University of Minnesota, Minneapolis, MN (K.G. Lurie).

    Copyright © 2005 by Aerospace Medical Association, Alexandria, VA.
     
  • Effects of inspiratory impedance on hemodynamic responses to a squat-stand test in human volunteers: implications for treatment of orthostatic hypotension (276 KB)

    Victor A. Convertino, Duane A. Ratliff, Jacqueline Crissey, Donald F. Doerr, Ahamed H. Idris, and Keith G. Lurie

    Eur J Appl Physiol 2005 Jul;94(4): 392-399. Epub 2005 Apr 28.

    Recent studies in our laboratory demonstrated that spontaneous breathing through an inspiratory impedance threshold device (ITD) increased heart rate (HR), stroke volume (SV), cardiac output (Q), and mean arterial blood pressure (MAP) in supine human subjects. In this study, we tested the effectiveness of an ITD as a countermeasure against development of orthostatic hypotension, provoked using a squat-to-stand test (SST). Using a prospective, randomized blinded protocol, 18 healthy, normotensive volunteers (9 males, 9 females) completed two-counterbalanced 6-min SST protocols with and without (sham) an ITD set to open at 0.7 kPa (7-cm H2O) pressure. HR, SV, Q, total peripheral resistance (TPR), and MAP were assessed noninvasively with infrared finger photoplethysmography. Symptoms were recorded on a 5-point scale (1 = normal; 5 = faint) of subject perceived rating (SPR). The reduction in TPR produced by SST (-355 %) was not affected by the ITD. Reduction in MAP with ITD during the transient phase of the SST (-3.60.5 kPa or -274 mmHg) was less (P = 0.03) than that measured while breathing through a sham device (-4.80.4 kPa or -363 mmHg) despite similar (P < 0.926) elevations in HR of 152 bpm. SV (+24 %) and Q (+225 %) with the ITD were higher (P < 0.04) than SV (-84 %) and Q (+106 %) without the ITD. SPR was 1.40.1 with ITD compared to 2.00.2 with the sham device (P < 0.04). This reduction in orthostatic symptoms with application of an ITD during the SST was associated with higher MAP, SV and Q. Our results demonstrate the potential application of an ITD as a countermeasure against orthostatic hypotension.
    Read more.

    From the U.S. Army Institute of Surgical Research, Fort Sam Houston, TX (V.A. Convertino); Bionetics Corporation, NASA, Kennedy Space Center, FL (D.A. Ratliff); Spaceflight and Life Sciences Training Program, NASA, Kennedy Space Center, FL (J. Crissey); Technology Implementation Branch, NASA, Kennedy Space Center, FL (D.F. Doerr); Department of Surgery and Emergency Medicine, University of Texas Southwestern Medical Center, Dallas, TX (A.H. Idris); and Advanced Circulatory Systems, Inc., and the Department of Emergency Medicine, University of Minnesota, Minneapolis, MN (K.G. Lurie).

    Copyright © Springer-Verlag 2005
     
  • Hemodynamics associated with breathing through an inspiratory impedance threshold device in human volunteers (387 KB)

    Victor A. Convertino, PhD; Duane A. Ratliff, MS; Kathy L. Ryan, PhD; Donald F. Doerr, BSEE; David A. Ludwig, PhD; Gary W. Muniz; Deanna L. Britton; Savran D. Clah; Kathleen B. Fernald; Alicia F. Ruiz; Keith G. Lurie, MD; and Ahamed H. Idris, MD

    Crit Care Med 2004 Sep; Vol. 32, No. 9 (Suppl.) pages S381-S386

    Objective: Increased negative intrathoracic pressure during spontaneous inspiration through an impedance threshold device (ITD) causes elevated arterial blood pressure in humans. This study was performed to determine whether the acute increase in blood pressure induced by breathing through an ITD is associated with increased stroke volume and cardiac output. Design: Randomized, blinded, controlled trial. Setting: Laboratory. Subjects: Ten women and ten men. Interventions: We measured hemodynamic and respiratory responses during two separate ITD conditions: 1) breathing through a face mask with an ITD (impedance of 6 cm H2O [0.59 kPa]) and 2) breathing through the same face mask with a sham ITD (control). Stroke volume was measured by thoracic bioimpedance. Measurements and Main Conclusions: Compared with the control condition, ITD produced higher stroke volume (124 3 vs. 137 3 mL; p = .013), heart rate (63 3 vs. 68 3 beats/min; p = .049), cardiac output (7.69 vs. 9.34 L/min; p = .001), and systolic blood pressure (115 2 to 122 2 mm Hg [15.33 0.3 to 16.26 0.3 kPa]; p = .005) without affecting expired minute ventilation (6.2 0.4 to 6.5 0.4 L/min; p = .609). Conclusions: Breathing with an ITD at relatively low impedance increases systolic blood pressure by increasing stroke volume and cardiac output. The ITD may provide short-term protection against cardiovascular collapse induced by orthostatic stress or hemorrhage.
    Read more.

    From the U.S. Army Institute of Surgical Research, Fort Sam Houston, TX (V.A. Convertino and K.L. Ryan); Bionetics Corporation, NASA, Kennedy Space Center, FL (D.A. Ratliff); Technology Implementation Branch, NASA, Kennedy Space Center, FL (D.F. Doerr); Spaceflight and Life Sciences Training Program, NASA, Kennedy Space Center, FL (D.L. Britton, S.D. Clah, K.B. Fernald, and A.F. Ruiz); Georgia Prevention Institute, Department of Pediatrics, Medical College of Georgia, Augusta, GA (D.A. Ludwig); Professional Performance Development Group, San Antonio, TX (G.W. Muniz); Advanced Circulatory Systems, Inc., and Department of Emergency Medicine, University of Minnesota, Minneapolis, MN (K.G. Lurie); and Department of Surgery and Emergency Medicine, University of Texas Southwestern Medical Center, Dallas, TX (A.H. Idris).

    Copyright © 2004 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins
     
  • Effects of inspiratory impedance on the carotid-cardiac baroreflex response in humans (466 KB)

    Victor A. Convertino, Duane A. Ratliff, Kathy L. Ryan, William H. Cooke, Donald F. Doerr, David A. Ludwig, Gary W. Muniz, Deanna L. Britton, Savran D. Clah, Kathleen B. Fernald, Alicia F. Ruiz, Ahamed H. Idris, and Keith G. Lurie

    Clin Auton Res (2004) Aug;14(4):240-248

    Comment in: Clin Auton Res 2004 Aug;14(4):217-9

    We were interested in a therapeutic device designed to increase carotid-cardiac baroreflex sensitivity (BRS) since high BRS is associated with a lower risk for development of hypotension in humans with experimentally-induced central hypovolemia. We hypothesized that spontaneous breathing through an impedance threshold device (ITD) designed to increase negative intrathoracic pressure during inspiration and elevate arterial blood pressure would acutely increase BRS in humans. We tested this hypothesis by measuring heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures, and carotid-cardiac BRS in 10 female and 10 male subjects breathing through a face mask at three separate ITD conditions: (a) 6 cm H2O; (b) 12 cm H2O; and (c) a control (0 cm H2O). HR was increased (P = 0. 013) from 643 bpm during control to 683 bpm at 6 cm H2O ITD and 714 bpm at 12 cm H2O ITD breathing conditions. During ITD breathing, BRS was not altered but responses were shifted to higher arterial pressures. However, SBP and DBP were elevated for both the 6 and 12 cm H2O conditions compared to the 0 cm H2O condition, but returned to control (sham) levels by 30 minutes after cessation of ITD breathing. There were no gender effects for BRS or any hemodynamic responses to breathing through the ITD. We conclude that breathing with inspiratory impedance at relatively low pressures can increase baseline arterial blood pressure, i. e., reset the operational point for SBP on the baroreflex stimulus-response relationship, in healthy subjects. This resetting of the cardiac baroreflex may represent a mechanism that allows blood pressure to increase without a reflex-mediated reduction in HR.
    Read more.

    From the U.S. Army Institute of Surgical Research, Fort Sam Houston, TX (V.A. Convertino, K.L. Ryan, and W.H. Cooke); Bionetics Corporation, NASA, Kennedy Space Center, FL (D.A. Ratliff); Biological & Chemical Laboratories Branch, NASA, Kennedy Space Center, FL (D.F. Doerr); Department of Pediatrics, Georgia Prevention Institute, Medical College of Georgia, Augusta, GA (D.A. Ludwig); Professional Performance Development Group, Inc., San Antonio, TX (G.W. Muniz); Spaceflight and Life Sciences Training Program, NASA, Kennedy Space Center, FL (D.L. Britton, S.D. Clah, K.B. Fernald, and A.F. Ruiz); Department of Emergency Medicine, Anesthesiology & Medicine, University of Florida, Gainesville, FL (A.H. Idris); and Advanced Circulatory Systems, Inc., and Department of Emergency Medicine, University of Minnesota, Minneapolis, MN (K.G. Lurie).

    Copyright © 2004, Victor A. Convertino, Ph.D.
     
  • Increased impedance to inspiration ameliorates hemodynamic changes associated with movement to upright posture in orthostatic hypotension: A randomized blinded pilot study.

    Daniel P. Melby, MD, Fie Lu, MD, Scott Sakaguchi, MD, Maureen Zook, BA, David G. Benditt, MD.

    Heart Rhythm. 2007 Feb;4(2):128-35. Epub 2006 Oct 19.

    BACKGROUND: Movement to upright posture may result in marked drop of blood pressure with susceptibility to injury from syncope and falls in patients with orthostatic hypotension. OBJECTIVE: The purpose of this study was to determine if increasing negative intrathoracic pressure by using an inspiratory impedance threshold device before change of posture diminishes blood pressure fall by enhancing venous return. METHODS: Eighteen healthy subjects and 22 orthostatic hypotension patients were randomized to either an active (impedance 7 cm H2O) or sham (no inspiratory impedance) impedance threshold device. Arterial blood pressure, heart rate, and estimated stroke volume and total peripheral resistance were recorded in the supine and upright postures using a noninvasive finger arterial blood pressure monitor. After a rest period, the alternate impedance threshold device (sham or active) was tested in each individual. RESULTS: Compared with the sham impedance threshold device test, the active impedance threshold device resulted in significant reduction in the magnitude of upright posture-induced fall in blood pressure and a greater increase of total peripheral resistance after standing in both healthy subjects and orthostatic hypotension patients. Stroke volume was not measurably altered. Among all subjects who exhibited a postural blood pressure drop >10 mmHg on the day of study, active impedance threshold device treatment consistently blunted blood pressure fall during the initial 100 seconds after standing (<0.04). Induced orthostatic symptoms were less severe with the active impedance threshold device both at onset of upright posture and during 30 seconds of standing. CONCLUSION: Enhancing impedance to inspiration may prove useful as adjunctive therapy for diminishing symptoms associated with movement to upright posture in individuals with orthostatic hypotension.

    From the Cardiac Arrhythmia Center and Syncope Center, Cardiovascular Division, Department of Medicine, University of Minnesota, Minneapolis, Minnesota.

    Copyright © 2007, David G. Benditt, MD.

Posted with permission from the authors.

Information in brackets has been added. This note does not apply to the above research abstracts.

Note: These are PubMed abstracts.

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