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Effect of lung recruitment on oxygenation in patients with acute lung injury ventilated in CPAP/pressure support mode

Introduction

One of the aims of lung recruitment is to improve oxygenation [1], but it has not yet been investigated in spontaneously breathing patients. Our objective was to evaluate the effects of recruitment maneuvers on oxygenation in patients ventilated in CPAP/ pressure support (CPAP/PS) mode.

Methods

In a prospective, observational study, 30 patients with a Lung Injury Score ≥2 were recruited. Following baseline measurements (t0) PEEP was increased by 5 cmH2O (t1). Recruitment maneuver was applied for 40 seconds with 40 cmH2O PS. Measurements were taken immediately after recruitment (t2) then 15 minutes (t3) and 30 minutes later (t4).

Results

According to the difference of PaO2/FiO2 between t2 and t0, three groups were defined: nonresponders (NR: difference of PaO2/FiO2 ≤0%, n = 8), low responders (LR: difference of PaO2/FiO2 = 0 to 50%, n = 11) and high responders (HR: difference of PaO2/FiO2 >50%, n = 11). In the NR-group, PaO2/FiO2 decreased significantly: median (interquartile), PaO2/FiO2 = 178 (159 to 240) versus 165 (118 to 210) mmHg; in the LR-group and in the HR-group there was significant improvement: 119 (98 to 164) versus 161 (123 to 182) mmHg and 141 (130 to 183) versus 239 (224 to 369) mmHg, P < 0.05, respectively. Dynamic compliance (Cdyn) significantly dropped at t as compared with t in the NR-group, Cdyn = 62 (48 to 87) versus 53 (43 to 78) ml/cmH2O, while there was no significant change in the LR- and HR-groups, P < 0.05. At the same time points the dead space to tidal volume ratio (Vds/Vte) significantly increased in the NR-group, Vds/Vte = 30 (23 to 37) versus 37 (26 to 42)%, but not in the LR- and HR-groups, P < 0.05.

Conclusion

Recruitment maneuvers improved PaO2/FiO2 in the majority of patients (73%) without affecting Cdyn or Vds/Vte; therefore it may be a safe approach to improve oxygenation in patients ventilated in CPAP/PS mode.

References

  1. 1.

    Lachman B: Intensive Care Med. 1992, 18: 319-21. 10.1007/BF01694358.

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Lovas, A., Trasy, D., Nemeth, M. et al. Effect of lung recruitment on oxygenation in patients with acute lung injury ventilated in CPAP/pressure support mode. Crit Care 19, P226 (2015). https://doi.org/10.1186/cc14306

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Keywords

  • Observational Study
  • Volume Ratio
  • Emergency Medicine
  • Lung Injury
  • Tidal Volume