Category: RespirAct

Non-invasive Measurement of Cardiac Output Using an Iterative, Respiration-based Method

M Klein, L Minkovich, M Machina, M Selzner, V N Spetzler, J M Knaak, D Roy, J Duffin, J A Fisher. Br J Anaesth. 2015 Mar;114(3):406-13. doi: 10.1093/bja/aeu377. Epub 2014 Dec 8.
Background: Current non-invasive respiratory-based methods of measuring cardiac output [Formula: see text] make doubtful assumptions and encounter significant technical difficulties. We present a new method using an iterative approach [Formula: see text], which overcomes limitations of previous methods.

Read More »

Assessment of Myocardial Reactivity to Controlled Hypercapnia with Free-breathing T2-prepared Cardiac Blood Oxygen Level–Dependent MR Imaging

Hsin-Jung Yang, Roya Yumul, Richard Tang, Ivan Cokic, Michael Klein, Avinash Kali, Olivia Sobczyk, Behzad Sharif, Jun Tang, Xiaoming Bi, Sotirios A. Tsaftaris, Debiao Li, Antonio Hernandez Conte, Joseph A. Fisher, Rohan Dharmakumar.
Cardiac stress testing is the standard of care for diagnosing ischemic heart disease (1). It is performed in nearly 10 million patients each year in the United States alone. It is conventionally initiated with exercise to induce hyperemia, and it is coupled with imaging to identify stress-induced failure to increase perfusion, or frank hypoperfusion in myocardial territories.

Read More »

Measuring Cerebrovascular Reactivity: the Dynamic Response to a Step Hypercapnic Stimulus

Julien Poublanc, Adrian P Crawley, Olivia Sobczyk, Gaspard Montandon, Kevin Sam, Daniel M Mandell, Paul Dufort, Lashmikumar Venkatraghavan, James Duffin, David J Mikulis, Joseph A Fisher. J Cereb Blood Flow Metab. 2015 Nov;35(11):1746-56. doi: 10.1038/jcbfm.2015.114. Epub 2015 Jul 1.
We define cerebral vascular reactivity (CVR) as the ratio of the change in blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal (S) to an increase in blood partial pressure of CO2 (PCO2): % Δ S/Δ PCO2 mm Hg. Our aim was to further characterize CVR into dynamic and static components and then study 46 healthy subjects collated into a reference atlas and 20 patients with unilateral carotid artery stenosis. We applied an abrupt boxcar change in PCO2 and monitored S.

Read More »