title: The effects of prolonged acute hypobaric hypoxia on novel measures of biventricular performance.
abstract: BACKGROUND
  There are limited data on the effects of prolonged acute hypoxia on individual and global measures of biventricular function.
  
  
  OBJECTIVE
  The aim of this study was to assess its effects on conventional and novel measures of biventricular function, including the recently defined E'/(A'×S') (EAS) index, obtained using pulsed-wave tissue Doppler Imaging (PWTDI) and associated blood brain natriuretic peptide (BNP) levels.
  
  
  METHODS
  In this study, 14 healthy subjects aged 30.5 years were assessed at baseline and at >150 minutes following hypobaric hypoxia (HH) to the equivalent altitude of 4800 m for a total of 180 minutes. The combined EAS index (E'/(A' × S')) was calculated at the mitral and tricuspid annulus using data from the peak systolic (S') early (E') and late (A') diastolic filling.
  
  
  RESULTS
  It was seen that HH increased resting heart rate (63.4 ± 8.4 vs. 85.2 ± 10.2/min; P < 0.0001), cardiac output (4.6 ± 0.7 L/min vs. 6.1 ± 1.2 L/min; P < 0.0001), peak pulmonary artery systolic pressure (PASP) (26.3 ± 2.0 mmHg vs. 37.2 ± 6.3 mmHg; P < 0.0001), and reduced SpO2 (98.5 ± 1.1 vs. 72.9 ± 8.1%; P < 0.0001). There was a significant reduction in mitral (0.19 ± 0.06 vs. 0.11 ± 0.03; P < 0.0001) and tricuspid (0.12 ± 0.04 vs. 0.09 ± 0.03; P = 0.03) EAS indices, but no change in left or right ventricular myocardial performance (Tei) indices, global left ventricular (LV) longitudinal systolic strain, BNP levels, or estimated filling pressures (E/E'). Only reducing SpO2 remained as an independent predictor of PASP on multivariate analysis (overall R(2) = 0.77; P < 0.0001). The right and LV EAS indices were significantly correlated (r = 0.45; 95% CI: 0.07-0.7; P = 0.02).
  
  
  CONCLUSIONS
  The conclusion from this study was that acute prolonged HH does not adversely affect resting global biventricular function and there is evidence of linked right and LV responses.
authors.affiliation: Department of Cardiology, Poole Hospital NHS Foundation Trust, Dorset, United Kingdom. christopherboos@hotmail.com
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Boos
authors.forename: Pete D
authors.initials: PD
authors.lastname: Hodkinson
authors.forename: Adrian
authors.initials: A
authors.lastname: Mellor
authors.forename: Nick P
authors.initials: NP
authors.lastname: Green
authors.forename: Daniel
authors.initials: D
authors.lastname: Bradley
authors.forename: Kim
authors.initials: K
authors.lastname: Greaves
authors.forename: David R
authors.initials: DR
authors.lastname: Woods
mesh_terms: D000208:Acute Disease; D000328:Adult; D000532:Altitude Sickness / Q000150:complications*; D002302:Cardiac Output / Q000502:physiology*; D015331:Cohort Studies; D018619:Echocardiography, Doppler, Pulsed; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D015999:Multivariate Analysis; D010092:Oximetry / Q000379:methods; D010101:Oxygen Consumption / Q000502:physiology; D011446:Prospective Studies; D011669:Pulmonary Wedge Pressure; D012016:Reference Values; D013318:Stroke Volume / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*; D016278:Ventricular Function, Right / Q000502:physiology*