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Table 3 Results of physiological measurements (see also Fig. 3)

From: “Low-” versus “high”-frequency oscillation and right ventricular function in ARDS. A randomized crossover study

Variable CV1 4 Hz HFO 4 Hz HFO-TGI 7 Hz HFO CV2 Strategy Effect–p value R2/(%) of variation explained
ES-eccentricity index 1.38 ± 0.21 1.26 ± 0.10 a 1.17 ± 0.13 a 1.42 ± 0.17 b,c 1.27 ± 0.19 d < 0.001 0.77/(77%)
RVEDA (cm2) 14.9 ± 5.7 13.0 ± 4.3 12.4 ± 3.8 14.8 ± 5.3c 13.6 ± 4.7 0.003 0.92/(92%)
LVEDA (cm2) 24.8 ± 7.7 23.4 ± 6.7 24.0 ± 6.6 23.1 ± 7.5 23.1 ± 6.6 0.22 0.91 (91%)
FAC of the RV 0.41 ± 0.08 0.41 ± 0.07 0.44 ± 0.07b 0.35 ± 0.09a,b,c 0.40 ± 0.09c < 0.001 0.78/(78%)
TAPSE (cm) 1.97 ± 0.55 1.88 ± 0.47 2.04 ± 0.55b 1.66 ± 0.48a,b,c 1.96 ± 0.58d < 0.001 0.90/(90%)
PaO2/FiO2 139.1 ± 20.5 249.6 ± 53.6a 246.4 ± 77.6a 248.1 ± 78.0a 155.0 ± 48.2b,c,d < 0.001 0.53/(53%)
ScvO2 (%) 68.4 ± 4.7 74.4 ± 5.1a 74.3 ± 5.1a 74.2 ± 5.8a 70.6 ± 4.2b,c,d < 0.001 0.74 (74%)
Arterial pH 7.39 ± 0.09 7.42 ± 0.14 7.43 ± 0.14 7.29 ± 0.12a,b,c 7.36 ± 0.09d < 0.001 0.75/(75%)
Shunt fraction 0.34 ± 0.07 0.21 ± 0.07a 0.23 ± 0.08a 0.23 ± 0.10a 0.35 ± 0.10b,c,d < 0.001 0.66/(66%)
Oxygenation Index 16.1 ± 5.4 13.1 ± 4.2a 12.7 ± 4.0a 14.4 ± 6.8 14.1 ± 4.0 0.03 0.66/(66%)
End-insp. Pplateau (cmH2O)e 29.9 ± 4.5     27.9 ± 4.5a   
End-exp. Pplateau (cmH2O)e 16.4 ± 2.5     15.9 ± 2.3f   
Driving pressure (cmH2O)e 13.5 ± 3.7     12.0 ± 4.1a   
C,rs (mL/cmH2O)e 35.1 ± 11.5     41.6 ± 17.9a   
MAP (kPa) 10.9 ± 0.9 12.3 ± 1.4a 12.0 ± 1.2a 11.5 ± 1.2 11.4 ± 0.7 0.01 0.62/(62%)
Heart rate (bpm) 89.1 ± 18.8 90.0 ± 18.7 90.0 ± 19.0 99.1 ± 23.7b,c 92.2 ± 21.0 0.002 0.88 (88%)
CVP (kPa) 1.7 ± 0.6 1.8 ± 0.5 1.8 ± 0.5 1.9 ± 0.5 1.7 ± 0.5 0.86g  
Cardiac index (L/min/m2) 3.25 ± 0.38 3.35 ± 0.29 3.43 ± 0.36 3.11 ± 0.40>c 3.33 ± 0.34 0.009 0.61 (61%)
Stroke volume index (mL/m2) 38.3 ± 10.0 39.2 ± 10.8 40.4 ± 12.2 33.5 ± 10.1a,b,c 38.2 ± 10.3d 0.001 0.90 (90%)
DO2I (mL/min/m2) 363.6 ± 64.6 401.6 ± 525a 407.5 ± 49.6a 368.5 ± 74.7,c 373.1 ± 59.1b,c < 0.001 0.83 (83%)
VO2I (mL/min/m2) 103.8 ± 28.5 109.3 ± 26.7 109.3 ± 28.0 98.9 ± 34.6 99.2 ± 30.6 0.11 0.70 (70%)
SVRI (dynes/cm5/s/m2)/ 1744 ± 408 1911 ± 373 1820 ± 364 1905 ± 370 1783 ± 322 0.07 0.82 (82%)
  1. Values are mean ± SD. CV1 first protocol period of conventional ventilation, HFO high-frequency oscillation, TGI tracheal gas insufflation, CV2 second protocol period of conventional ventilation (see also Fig. 1); “Strategy effect—p value” pertains to the level of significance of the fixed factor “ventilatory strategy” as determined by linear mixed model analysis (see also “Statistical Analysis” of the current text and Additional file 1); “R2/(%) variation explained” has been derived by bivariate linear regression between observed and mixed model-predicted values (see also legend of Fig. 3); ES end-systolic, RVEDA right-ventricular end-diastolic area, LVEDA left ventricular end-diastolic area, RV right ventricle, FAC of the RV RV fractional area change between end-diastole and end-systole [calculated as RVEDA-to-RV end-systolic area difference divided by RVEDA), TAPSE tricuspid annular plane systolic excursion, PaO2 arterial oxygen tension, FiO2 inspiratory oxygen fraction, ScvO2 central venous oxygen saturation, End-insp. end-inspiratory, End-exp. end-expiratory, Pplateau plateau pressure, C,rs quasistatic compliance of the respiratory system, MAP mean arterial pressure, bpm beats per min, CVP central venous pressure, DO2I oxygen delivery index, VO2I oxygen consumption index, SVRI systemic vascular resistance index. Primary outcome (i.e., ES-eccentricity index) data are highlighted in italics
  2. ap < 0.05 versus CV1
  3. bp < 0.05 versus 4 Hz HFO
  4. cp < 0.05 versus 4 Hz HFO-TGI
  5. dp < 0.05 versus 7 Hz HFO
  6. eVariables compared between CV1 and CV2 by a paired t-test. Actual p values of pairwise comparisons are reported in Additional file 2
  7. fIn one patient, CV1 external positive end-expiratory pressure (PEEP) was 18 cmH2O and was set at 15 cmH2O during CV2 by error of the attending investigator (see also Fig. 1)
  8. gp value determined by one-way analysis of variance (factor = ventilatory strategy) because convergence was not achieved during the “MIXED procedure” and the validity of mixed-model fit was uncertain