Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Supine and upright haemodynamic effects of sublingual nitroglycerin and inhaled salbutamol: a double-blind, placebo-controlled, randomized study Anna M. Tahvanainen a , Antti J. Tikkakoski a , Miia H. Leskinen a , Klaus Nordhausen b , Mika Ka ¨ ho ¨ nen a,c , Tiit Ko ¨o ¨ bi c , Jukka T. Mustonen a,d , and Ilkka H. Po ¨ rsti a,d Objectives: Pulse wave analysis is widely applied to measure the haemodynamic effects of nitroglycerin and salbutamol as an endothelium-independent and endothelium-dependent vasodilator, respectively. The recordings are usually performed in supine position from 10 to 20 successive heartbeats without simultaneous measurement of vascular resistance and cardiac function. Our objective was to examine the effects of nitroglycerin and salbutamol on central haemodynamics, arterial stiffness, cardiac function, and vascular resistance in supine and upright positions. Methods: A placebo-controlled, randomized and double- blinded passive head-up tilt protocol was performed after sublingual nitroglycerin (0.25 mg) or inhaled salbutamol (400 mg) in 35 healthy volunteers. Continuous tonometric pulse wave analysis, whole-body impedance cardiography, and plethysmographic finger blood pressure recordings were applied. Results: Nitroglycerin decreased aortic and finger blood pressure, radial DBP, vascular resistance, augmentation index and pulse wave velocity, and increased heart rate, cardiac index, stroke index and aortic reflection time (P < 0.030 for all). Salbutamol moderately decreased radial and aortic blood pressure and finger DBP, augmentation index and vascular resistance, but increased heart rate and cardiac index (P < 0.030 for all). Almost all of the strong haemodynamic effects of nitroglycerin were emphasized during the head-up tilt, whereas the effects of salbutamol on heart rate and cardiac index were more pronounced in the supine position. Conclusion: The haemodynamic changes induced by nitroglycerin and salbutamol were dependent on body position: the effects of nitroglycerin were accentuated during the head-up tilt, whereas those of salbutamol were more evident in the supine position. Keywords: endothelium, haemodynamics, impedance cardiography, pulse wave analysis, tilt-table test Abbreviations: AIx, augmentation index; BP, blood pressure; PWA, pulse wave analysis; PWV, pulse wave velocity; SVRI, systemic vascular resistance index INTRODUCTION P ulse wave analysis (PWA) has been widely applied for the assessment of haemodynamics and endo- thelial function in vivo [1,2]. In particular, changes in the PWA-derived measure of wave reflection and arterial stiffness, the augmentation index (AIx), have been utilized to record the haemodynamic alterations induced by sub- lingual nitroglycerin and inhaled salbutamol. The former has served as an endothelium-independent agent and the latter as a largely endothelium-dependent vasodilator, and the changes induced by these compounds in PWA record- ings have shown good repeatability [1,3]. Being noninva- sive, easily accessible and repeatable, PWA has technical benefits when compared with, for example, flow-mediated dilatation and laborious invasive venous occlusion plethys- mography [4,5]. Normally, the PWA measurements are performed with the participant resting in supine position. Parallel recordings of vascular resistance, pulse wave velocity (PWV) and cardiac function have only seldom been performed [6,7], although this would be important as both nitroglycerin and salbutamol can influence these variables. Limited information about haemodynamics is obtained if the variables are only measured at rest, as humans spend a large part of their time in the upright position. The change in body posture from supine to upright induces significant changes in blood distribution, arterial resistance and auto- nomic nervous system, and orthostatic challenge can thus be regarded as an exercise test addressing cardiovascular reactivity, as discussed in a recent editorial by Avolio and Parati [8]. Previous reports have shown that the changes in haemodynamic variables in response to physical challenge have prognostic value. Enhanced blood pressure (BP) Journal of Hypertension 2012, 30:297–306 a School of Medicine, b School of Health Sciences, University of Tampere, c Department of Clinical Physiology and d Department of Internal Medicine, Tampere University Hospital, Tampere, Finland Correspondence to Anna M. Tahvanainen, MD, Department of Internal Medicine, School of Medicine, University of Tampere, Tampere FIN-33014, Finland. Tel: +358 3 3551 8306; fax: +358 3 3551 6164; e-mail: anna.tahvanainen@uta.fi Received 15 June 2011 Revised 10 August 2011 Accepted 18 October 2011 J Hypertens 30:297–306 ß 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins. DOI:10.1097/HJH.0b013e32834e4b26 Journal of Hypertension www.jhypertension.com 297 Original Article