“…The current mainstay of pulmonary vascular imaging for PE, computed tomography (CT) angiography, carries several risks to the postsurgical patient, including the indirect risk of patient transport, contrast allergy, contrast nephropathy, radiation exposure and economic cost when the CT angiography shows no treatable condition (Brenner et al, 2003;Hunold et al, 2003;Cochran, 2005;Josephson et al, 2005;Lin & Bonventre, 2005;Mitchell & Kline, 2007). Because of its high false-positive rate, the D-dimer has little utility as a screening tool in the immediate postsurgical period (Noda et al, 2000;Boncinelli et al, 2001;Arnesen et al, 2003;Karnani et al, 2005). Likewise, measurement of the arterial blood partial pressures of oxygen (PaO 2 ) and carbon dioxide (PaCO 2 ) seldom affects clinical decisionmaking in the evaluation of PE (Kline et al, 2000).…”