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Time required for PaO2 equilibration during mechanical ventilation with changes in FiO2
Critical Care volume 2, Article number: P088 (1998)
Although it's a general practice to obtain blood gas sample after 30 min when FiO2 was changed during mechanical ventilation, exact timing for blood gas analysis has not been very well documented. In this study we aimed to investigate the time required for PaO2 equilibration during pressure controlled ventilation (PCV) with changes in FiO2.
Patients and methods
25 adult patients with stable blood gas values (5 female, 20 male) on PCV (Servo 900C Siemens, Elema, Sweden) with FiO2:0.35, frequency: 12 breaths/min, tidal volume: 10 ml/kg and PEEP: 5 cmH2O were studied.
Following a control blood gas measurement at FiO2:0.35 and determination of PaO2 (PaO235), FiO2 was increased to 0.55 for 60 min and again returned to 0.35 without any change in ventilatory parameters. Blood samples were obtained and immediate blood gas measurements were performed on 3, 5, 7, 9, 11, 15, 20, 25, 30 min in both periods and at the 60th minute in FiO2:0.55 period. The PaO2 value measured at the 60th minute of FiO2:0.55 (PaO255) was accepted as representative of equilibration.
The timing of PaO2 values reaching either the PaO255 and PaO235 levels were recorded for each patient and average (Mean ± SD) of these values were calculated.
The average (Mean ± SD) time period necessary to reach PaO255 and PaO235 were 9 ± 7.33 min and 7.08 ± 6.02 min respectively. The numbers and the percentages of the patients reaching their own PaO255 and PaO235 values for each sampling time were listed in Table 1.
We concluded that after FiO2 changes during PCV, 10 min will be adequate for obtaining the blood gas sample representative for equilibration of PaO2.
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Cite this article
Cakar, N., Tugrul, M., Demirarslan, A. et al. Time required for PaO2 equilibration during mechanical ventilation with changes in FiO2. Crit Care 2, P088 (1998). https://doi.org/10.1186/cc218
- Mechanical Ventilation
- Emergency Medicine
- Sampling Time
- Tidal Volume
- Exact Timing