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Table 2 Compression parameters, time related parameters and ventilation parameters

From: Short structured feedback training is equivalent to a mechanical feedback device in two-rescuer BLS: a randomised simulation study

Variables Standard BLS (sCPR) (n = 114) QCPR (mfCPR) (n = 102) Human feedback (hfCPR) (n = 110) P-value sCPR vs QmfCPR P-value sCPR vs hfCPR P-value mfCPR vs hfCPR
Chest compression parameters
 Effective compression ratio (ECR) a 0.27 (0.07–0.36) 0.35 (0.21–0.45) 0.33 (0.10–0.46) 0.018 0.078 0.435
 Effective compressions [%] b 33 (9–44) 43 (24–55) 41 (13–57) 0.023 0.066 0.656
 Compression rate [min-1] 105 ± 9 102 ± 5 109 ± 7 0.004 0.008 <0.001
 Compression depth [mm] 57 ± 4 55 ± 3 58 ± 3 0.012 0.384 <0.001
 Incorrect decompressions [%] 16 (4–45) 33 (15–47) 26 (2–43) 0.023 0.905 0.044
 Incorrect pressure point [%] 0 (0–5) 0 (0–8) 0 (0–3)   ns*  
 Injuries n/% c 3/3 1/1 5/5   ns*  
Time related parameters
 Flow time fraction % 81 ± 3 82 ± 2 80 ± 4 0.003 0.408 0.001
 Flow time/min [s] d 49 + 2 49 + 1 48 + 2 0.003 0.408 0.001
 Absolute hands-off time [s] e 61 ± 17 60 ± 15 67 ± 17 0.731 0.053 0.021
 Time till first chest compression [s] f 3 (2–4) 8 (5–11) 2 (1–3) <0.001 0.172 <0.001
Ventilation parameters
 Minute volume [ml/min] 1478 ± 707 1305 ± 655 1276 ± 632   ns*  
 Ventilation volume [ml] 260 ± 96 240 ± 95 231 ± 92   ns*  
 Ventilation time/min [s] 4 ± 2 3 ± 2 4 ± 2 0.022 0.097 0.517
 Gastric Inflations, n 0 (0–0) 0 (0–0) 0 (0–0)   ns*  
  1. Normally distributed data are presented as mean ± standard deviation; data not following normal distribution are presented as median (IQR). Pairwise comparisons between groups were calculated for significant p-values by the means of ANOVA
  2. *P-value <0.05 for ANOVA comparison between all groups; fonts in bold indicate statistical significance (p<0.05)
  3. aEffective compression ratio was defined as effective compressions [%] multiplied by flow time [%]
  4. bEffective compressions were defined as compressions with correct depth (50–60 mm), correct hand position and complete decompression
  5. cObserved injuries were blisters
  6. dFlow time was defined as the sum of all periods during which chest compressions were performed
  7. eAbsolute hands-off time was defined as the sum of all periods without chest compressions or ventilation
  8. fTime till first chest compression was defined as time from device activation to first chest compression in the mfCPR group and time from beginning of measurement to first chest compression in the sCPR group and the hfCPR group