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Table 1 Tested strategies of high-frequency oscillation (HFO)

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

HFO strategy

4-Hz HFO

4-Hz HFO-TGI

7-Hz HFO

mPaw (cmH2O)a

+ 10 cmH2Ob

+ 7–8 cmH2Ob

+ 10 cmH2Ob

FiO2

FiO2 of preceding CVc

FiO2 of preceding CVc

FiO2 of preceding CVc

ΔP (cmH2O)d

80–90

80–90

80–90

Bias flow (L/min)

60

60

60

I/E ratio

1/2

1/2

1/2

Cuff leak (cmH2O)

3–5

3–5

NA

TGI (L/min)e

NA

50% of MV of preceding CV

NA

Estimated Vt (mL)f

181.2 ± 6.5

190.0 ± 6.5

118.5 ± 4.1

RMg

CPAP of 45 cmH2O for 40 s

  1. mPaw mean airway pressure, TGI tracheal gas insufflation, FiO2 inspired oxygen fraction, CV conventional ventilation, ΔP oscillatory pressure amplitude, I/E ratio inspiratory-to-expiratory time ratio, TGI tracheal gas insufflation, MV minute ventilation, Vt tidal volume, RM recruitment maneuver, CPAP continuous positive airway pressure, NA not applicable
  2. 1 cmH2O = 0.098 kPa
  3. aValues correspond to the initial setting of the HFO mPaw and are referred to the mPaw of the pre-HFO CV (see also text and Fig. 1)
  4. bDuring HFO-TGI, the mPaw was set at 2–3 cmH2O lower than the mPaw of standard HFO to counterbalance the estimated, TGI-induced increase in tracheal pressure [15]; the maximum allowable upper limit of HFO mPaw was 40 cmH2O
  5. cProvided that peripheral oxygen saturation could be maintained above 90%
  6. dCorresponds to actual ventilator-displayed values after the setting of the “Power” within 80–90% of its maximal value
  7. eTGI FiO2 was equal to the FiO2 of the preceding CV; see also Supplement to Methods in Additional file 1
  8. fValues are mean ± SD; estimates were based on previously published data on Vt delivery during HFO [1], and a previously published Vt estimate of ~ 200 mL for a specific combination of HFO frequency (i.e., 3.5 Hz), ΔP (i.e., 90 cmH2O), bias flow (i.e., 40 L/min), tracheal tube internal diameter (i.e., 8.5 mm), mPaw level (i.e., 30 cmH2O), and respiratory compliance (i.e., ~ 31 cmH2O) [15]; further details (including a calculated possible bias and other limitations of these estimates) are reported in Additional file 1
  9. gEach HFO strategy was to be preceded by an RM, provided that RM abort criteria were not met; see also text, Fig. 1, and Additional file 1
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Journal of Intensive Care

ISSN: 2052-0492