Table 2

Comparison of ventilator parameters during periods of low and high vibration

Minute with lowest vibrationMinute with largest vibration
All transfers (n=109)
Group mean (SD) Group mean (SD) P value*
Vibration (m/s2) †0.40 (0.07)1.09 (0.19)<0.0001
VTemand (mL/kg)5.23 (1.79)5.28 (1.86)0.55
MV (mL/kg/min)0.28 (0.11)0.29 (0.11)0.07
PIP (cmH2O)18.2 (6.7)18.0 (6.7)0.49
FiO2 (%)37.3 (22.6)37.0 (21.6)0.64
Volume guarantee ventilation (n=97)‡
Group mean (SD) Group mean (SD) P value*
Vibration (m/s2) †0.41 (0.08)1.09 (0.19)<0.0001
VTemand (mL/kg)5.19 (1.54)5.29 (1.73)0.27
PIP (cm H2O)18.0 (7.1)17.8 (7.0)0.57
Group median (range) Group median (range) P value§
VTdiff (mL/kg)0.54 (0.03–6.76)0.51 (0.03–5.05)0.63
Pdiff (cm H2O)12.5 (0.2–32.9)11.8 (0.1–30.8)0.60
Pressure limited ventilation (n=17)‡
Group mean (SD) Group mean (SD) P value*
Vibration (m/s2) †0.44 (0.12)1.04 (0.21)<0.0001
VTemand (mL/kg)5.54 (2.74)5.33 (2.36)0.45
PIP (cm H2O)18.6 (3.6)18.7 (3.3)0.75
Group median (range) Group median (range) P value§
Pdiff (cm H2O)0.3 (0.2–1.7)0.5 (0.2–0.6)0.58
SIPPV mode (n=34)
Group mean (SD) Group mean (SD) P value*
Vibration (m/s2) †0.4 (0.07)1.14 (0.22)<0.0001
RR (1 /min)58.6 (16.2)60.3 (14.0)0.21
Group median (range) Group median (range) P value§
RRdiff (1 /min)13.3 (0–56.5)16.5 (0–50)0.29
SIMV mode (n=63)
Group mean (SD) Group mean (SD) P value*
Vibration (m/sec 2 ) †0.40 (0.07)1.06 (0.16)<0.0001
VTemand (mL/kg)5.53 (2.14)5.57 (2.21)0.69
VTespon (mL/kg)2.43 (2.47)2.54 (2.68)0.53
  • For each minute of recording, the median acceleration and the mean of the ventilator parameters were calculated. For each recording, the 1 min periods with lowest and highest vibration were chosen. Group statistics of these data are shown in table.

  • *Two-tailed paired Student T-test.

  • †Euclidean length of acceleration vector (see Methods section).

  • ‡During some transfers volume guarantee was turned on only for part of the transfer.

  • §Wilcoxon signed rank test

  • FiO2, fraction of inspired oxygen; MV, minute ventilation; Pdiff, absolute difference between the set and actual PIP (during pressure limited ventilation) or the maximum allowed inflating pressure and actual PIP (during volume guarantee ventilation); PIP, peak inflating pressure; RR, ventilator rate; RRdiff, the difference between the ventilator rate and the set minimum backup rate during SIPPV mode; SD, standard deviation; SIMV, synchronised intermittent mandatory ventilation; SIPPV, synchronised intermittent positive pressure ventilation; VTdiff, absolute difference between the target and actual expired tidal volume during volume guarantee ventilation; VTemand, expired tidal volume of ventilator inflations; VTespon, the tidal volume of spontaneous breaths during SIMV mode.