title: Inspiratory resistance improves postural tachycardia: a randomized study.
abstract: BACKGROUND
  The objective of this study was to determine the effect of inspiratory resistance through an impedance threshold device (ITD) on orthostatic tolerance in patients with postural tachycardia syndrome. We hypothesized that the ITD would result in a greater negative intrathoracic pressure to enhance cardiac venous return, improve stroke volume, and reduce heart rate in these patients.
  
  
  RESULTS
  We compared the effect of a sham device (sham, no resistance) versus an ITD (increased inspiratory resistance) in 26 patients with postural tachycardia syndrome in a randomized, single-blind, crossover study. Hemodynamic assessments were performed at baseline while supine and during head-up tilt to 70° for 10 minutes. We did not find differences in baseline hemodynamic parameters between the ITD and the sham devices. After 10 minutes of head-up tilt, the heart rate was lower with the ITD versus sham device (102±4 versus 109±4 beat/min, respectively; P=0.003). The ITD also improved stroke volume compared with the sham device (35±2 versus 26±1 mL; P=0.006).
  
  
  CONCLUSIONS
  These findings suggest that increasing negative intrathoracic pressure with ITD breathing improves heart rate control in patients with postural tachycardia syndrome during upright posture.
  
  
  BACKGROUND
  clinicaltrials.gov; Unique Identifier: NCT00962728.
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.). alfredo.gamboa@vanderbilt.edu.
authors: Alfredo
authors: A
authors: Gamboa
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: Sachin Y
authors: SY
authors: Paranjape
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: Bonnie K
authors: BK
authors: Black
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: Amy C
authors: AC
authors: Arnold
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: Rocío
authors: R
authors: Figueroa
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: Luis E
authors: LE
authors: Okamoto
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: Victor C
authors: VC
authors: Nwazue
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: Andre
authors: A
authors: Diedrich
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: W Dale
authors: WD
authors: Plummer
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: William D
authors: WD
authors: Dupont
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: David
authors: D
authors: Robertson
authors: From the Division of Clinical Pharmacology (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Departments of Medicine (A.G., S.Y.P., B.K.B., A.C.A., R.F., L.E.O., V.C.N., A.D., D.R., S.R.R.), Pharmacology (D.R., S.R.R.), Biostatistics (W.D.P., W.D.D.), and Neurology (D.R.), Vanderbilt University, Nashville, TN; and Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada (W.D.P., W.D.D.).
authors: Satish R
authors: SR
authors: Raj
mesh_terms: D000328:Adult; D000403:Airway Resistance; D018592:Cross-Over Studies; D004867:Equipment Design; D005260:Female; D006339:Heart Rate; D006801:Humans; D001239:Inhalation; D008297:Male; D056888:Patient Positioning; D054972:Postural Orthostatic Tachycardia Syndrome / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D011312:Pressure; D016037:Single-Blind Method; D013318:Stroke Volume; D013396:Suction / Q000295:instrumentation; D016683:Supine Position; D013714:Tennessee; D018667:Tilt-Table Test; D013997:Time Factors; D016896:Treatment Outcome
keywords: autonomic nervous system; postural tachycardia syndrome; stroke volume; tachycardia