title: Detection and quantification of left-to-right shunting using transpulmonary ultrasound dilution (TPUD): a validation study in neonatal lambs.
abstract: OBJECTIVE
  We investigated the accuracy of left-to-right shunt detection using transpulmonary ultrasound dilution (TPUD) and compared the agreement between pulmonary over systemic blood flow (Qp/Qs) ratio measured by TPUD [Qp/Qs(tpud)] and ultrasonic flow probes [Qp/Qs(ufp)].
  
  
  METHODS
  Seven newborn lambs under general anesthesia were connected to the TPUD monitor (COstatus™) after insertion of arterial and central venous catheters. A Gore-Tex® shunt, inserted between the descending aorta and left pulmonary artery, was intermittently opened and closed while cardiac output was varied by blood withdrawals. Flow probes were placed around the main pulmonary artery (Qufp) and the descending aorta proximal (Qpre) and distal (Qpost) to the shunt insertion. Qp/Qs(ufp) was calculated as (Qufp+Qpre-Qpost)/Qufp.
  
  
  RESULTS
  Seventy-two paired measurement sessions were analyzed. Shunts were detected by TPUD with a positive predictive value of 86%, a negative predictive value of 100%, a sensitivity of 100% and a specificity of 83%. The Bland-Altman analysis comparing Qp/Qs(tpud) and Qp/Qs(ufp) showed an overall mean bias (SD) of 0.1 (0.3), limits of agreement (LOA) of ±0.6 and a percentage error of 34.8%.
  
  
  CONCLUSIONS
  The qualitative diagnostic accuracy of TPUD for shunt detection is high. Modification of the algorithm seems required as shunt quantification by TPUD is accurate, but not yet very precise.
authors.forename: Sabine L
authors.initials: SL
authors.lastname: Vrancken
authors.forename: Arno F
authors.initials: AF
authors.lastname: van Heijst
authors.forename: Jeroen C
authors.initials: JC
authors.lastname: Hopman
authors.forename: Kian D
authors.initials: KD
authors.lastname: Liem
authors.forename: Johannes G
authors.initials: JG
authors.lastname: van der Hoeven
authors.forename: Willem P
authors.initials: WP
authors.lastname: de Boode
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002302:Cardiac Output; D004195:Disease Models, Animal; D004374:Ductus Arteriosus, Patent / Q000000981:diagnostic imaging / Q000503:physiopathology; D007201:Indicator Dilution Techniques; D011651:Pulmonary Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D034561:Sheep, Domestic; D014463:Ultrasonography / Q000379:methods*