title: Effect of positive end-expiratory pressure on porcine right ventricle function assessed by speckle tracking echocardiography.
abstract: BACKGROUND
  Right ventricle (RV) dysfunction and hypotension can be induced by high levels of positive end-expiratory pressure (PEEP). We sought to determine in an animal model if a novel ultrasound analysis technique: speckle tracking echocardiography (STE), could determine deterioration in RV function induced by PEEP and to compare this to a conventional method of RV analysis: fractional area change (FAC). STE is a sensitive, angle-independent method for describing cardiac deformation ('strain') and is particularly useful in analyzing RV function as has been shown in pulmonary hypertension cohorts.
  
  
  METHODS
  Ten pigs, 40-90 kg, anaesthetized, fully mechanically ventilated at 6 ml/kg were subject to step-wise escalating levels of PEEP at two-minute intervals (0, 5, 10, 15, 20, 25 and 30 cmH20). Intracardiac echocardiography was used to image the RV as transthoracic and transesophageal echocardiography did not give sufficient image quality or flexibility. Off-line STE analysis was performed using Syngo Velocity Vector Imaging (Seimens Medical Solutions Inc., USA). STE systolic parameters are RV free wall strain (RVfwS) and strain rate (RVfwSR) and the diastolic parameter RV free wall strain rate early relaxation (RVfwSRe).
  
  
  RESULTS
  With escalating levels of PEEP there was a clear trend of reduction in STE parameters (RVfwS, RVfwSR, RVfwSRe) and FAC. Significant hypotension (fall in mean arterial blood pressure of 20 mmHg) occurred at approximately PEEP 15 cmH2O. Comparing RVfwS, RVfwSR and RVfwSRe values at different PEEP levels showed a significant difference at PEEP 0 cmH2O vs PEEP 10 cmH2O and above. FAC only showed a significant difference at PEEP 0 cmH2O vs PEEP 20 cmH2O and above. 30% of pigs displayed dyssychronous RV free wall contraction at the highest PEEP level reached.
  
  
  CONCLUSIONS
  STE is a sensitive method for determining RV dysfunction induced by PEEP and deteriorated ahead of a conventional assessment method: FAC. RVfwS decreased to greater extent compared to baseline than FAC, earlier in the PEEP escalation process and showed a significant decrease before there was a clinical relevant decrease in mean arterial blood pressure. Studies in ICU patients using transthoracic echocardiography are warranted to further investigate the most sensitive echocardiography method for detecting RV dysfunction induced by mechanical ventilation.
authors: Division of Cardiovascular Diseases, Mayo Clinic, 200 First St SW, Rochester, MN 55905 USA ; Intensive Care Unit, Nepean Hospital, Kingswood, Sydney, 2749 NSW Australia.
authors: Sam R
authors: SR
authors: Orde
authors: Division of Cardiovascular Diseases, Mayo Clinic, 200 First St SW, Rochester, MN 55905 USA.
authors: Atta
authors: A
authors: Behfar
authors: Division of Cardiovascular Diseases, Mayo Clinic, 200 First St SW, Rochester, MN 55905 USA.
authors: Paul G
authors: PG
authors: Stalboerger
authors: Division of Cardiovascular Diseases, Mayo Clinic, 200 First St SW, Rochester, MN 55905 USA.
authors: Sergio
authors: S
authors: Barros-Gomes
authors: Division of Cardiovascular Diseases, Mayo Clinic, 200 First St SW, Rochester, MN 55905 USA.
authors: Garvan C
authors: GC
authors: Kane
authors: Division of Cardiovascular Diseases, Mayo Clinic, 200 First St SW, Rochester, MN 55905 USA.
authors: Jae K
authors: JK
authors: Oh
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D004452:Echocardiography / Q000379:methods; D005260:Female; D015588:Observer Variation; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011175:Positive-Pressure Respiration / Q000009:adverse effects*; D013312:Stress, Physiological / Q000502:physiology; D034421:Sus scrofa; D018497:Ventricular Dysfunction, Right / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D016278:Ventricular Function, Right / Q000502:physiology
chemical_list: D010100:Oxygen
keywords: Mechanical ventilation; PEEP; Right ventricle; Right ventricle strain; Speckle tracking echocardiography