Abstract
Background:
PEEP is titrated to improve oxygenation during mechanical ventilation. PEEP may ameliorate or exacerbate lung injury. It is clinically desirable to identify factors that are associated with a clinical improvement or deterioration following a PEEP change. However, these factors have not been adequately described in the literature. Therefore, we quantify the empirical probability of PEEP changes resulting in positive effects on oxygenation, pulmonary mechanics and dead-space fraction and identify clinical factors associated with positive response in children receiving mechanical ventilation.
Methods:
A retrospective analysis of continuous data was conducted in mechanically ventilated pediatric subjects admitted to the intensive care unit. During a PEEP increase (PEEPincrease), a responder was defined as anyone who exhibited an improved SpO2/FIO2 (S/F); non-responders demonstrated a worsening S/F in the hour following. For cases where PEEP was decreased (PEEPdecrease), a responder was anyone who maintained or increased S/F; non-responders demonstrated a worsening S/F. Features from continuous mechanical ventilation variables were extracted and differences in these features between responders and non-responders were tested using a generalized estimating equation to account for repeated measures.
Results:
A total of 286 PEEP change cases were eligible for analysis in 76 subjects. Of the PEEPincrease cases, the empirical probability of positive response was 56%, 67% and 54% for oxygenation, mechanics and dead-space fraction respectively. The median S/F increase was 13. For PEEPdecrease, the empirical probability of acceptable response was 46%, 53% and 46% for oxygenation, mechanics and dead-space fraction respectively. PEEPincrease responders had higher FIO2 requirement (70.8 versus 52.5%; P < 0.001), mean airway pressure (14.0 versus 12.9 cm H2O; P= 0.029) and oxygen saturation index (9.9 versus 7.5; P< 0.01) versus non-responders. For PEEPdecrease, no statistically significant differences in demographic or ventilator parameters were observed.
Conclusions:
In children requiring mechanical ventilation, the responder rate was modest for both PEEPincrease and PEEPdecrease cases. These data suggest PEEP titration often does not have the desired clinical effect and predicting which patients will manifest a positive response is complex, potentially requiring more sophisticated means of assessing individual subjects.
Comparison between PEEP responders and non-responders following a PEEP increase. Responders were defined as those demonstrating oxygenation improvement in the 1-hour following the PEEP change relative to the preceding 1-hour.
Clinical Parameter
Responders
Non-responders
P
Cdynamic (ml/kg/cmH2O)
0.42 (0.25 - 0.53)
0.44 (0.29 - 0.50)
0.598
PEEP (cmH2O)
8 (6 - 10)
7 (5 - 8)
0.438
SpO2 (%)
95 (93 - 97)
94 (93 - 96)
0.450
FiO2 (%)
71 (55 - 86)
52 (46 - 65)
<0.001
Vt (ml/kg)
6.0 (5.0 - 7.2)
6.7 (5.3 - 7.2)
0.427
RR (breaths/min)
28 (24 - 36)
27 (24 - 32)
0.367
Pmean (cmH2O)
14.0 (11.9 - 16.5)
13.0 (10.8 - 14.8)
0.029
OSI
9.9 (7.4 - 14.8)
7.5 (5.7 - 8.4)
0.002
ΔPEEP (cmH2O)
1 (1 – 2)
1 (1 – 2)
0.732
1 (n, %)
59 (63)
37 (51)
2 (n, %)
19 (20)
24 (26)
3 (n, %)
14 (15)
11 (15)
4 (n, %)
2 (2)
0 (0)
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