Closed system endotracheal suction to reduce loss in functional residual capacity during pressure-controlled mechanical ventilation

Introduction

The aim of the study was the evaluation of efficacy to limit loss in functional residual capacity (FRC) of endotracheal suction with a closed system (ESCS) versus endotracheal suction with an open standard system (ESOS) in patients needing ventilation with PEEP > 10 cmH₂O.

Methods

After IRB approval and obtaining consent, 15 patients admitted to the ICU for acute respiratory failure were connected and adapted to the Engstrom Carestation (GE Healthcare – 2006) by the closed suction system Cathy (Vygon – 2006). We performed ESCS and ESOS in an alternate randomization sequence at a distance of 2 hours for the first from the second. FRC measurements (based on evaluation of nitrogen washin and washout by the COVX metabolic module – Engstrom Carestation Lung FRC INview) were made at baseline, 5, 10 15, 20, 25, and 30 minutes after suction. The PaO₂ was measured at baseline, immediately after the suction and 30 minutes after suction. Loss in FRC was considered as the difference between the basal value and values obtained after suction, and the time to FRC recovery after suction was considered as the minutes to return to the basal value. Data are shown as the mean ± SD; FRC was measured in millilitres, time in minutes, PaO₂ in mmHg; intergroup variables were analysed with the Mann–Whitney test. P < 0.05 was taken as statistically significant.

Results

Basal values of all studied parameters did not show significant differences between the two groups categorized by suction methods. Loss in FRC 5, 10 and 15 minutes after ESCS was significantly lower than after ESOS (5 minutes ESCS = -250 ± 483, ESOS = -740 ± 567, P = 0.002; 10 minutes ESCS = -36 ± 388, ESOS = -211 ± 188, P = 0.006; 15 minutes ESCS = -89 ± 489, ESOS = -268 ± 148, P = 0.046; 20 minutes ESCS = -157 ± 569, ESOS = -125 ± 176, not significant; 25 minutes ESCS = -167 ± 570, ESOS = -89 ± 133, not significant; 30 minutes ESCS = +216 ± 246, ESOS = +22 ± 81, not significant). Time to recovery of FRC basal value after ESCS was significantly lower than after ESOS (ESCS = 9 ± 5, ESOS = 21 ± 7, P < 0.0001). PaO₂ reduction was significantly lower after ESCS than after ESOS (ESCS = 151 ± 18, ESOS = 119 ± 9, P = 0.048)

Conclusion

ESCS in patients needing mechanical ventilation with PEEP > 10 cmH₂O for acute respiratory failure reduces significantly the loss of FRC, the reduction on PaO₂ and a time to recovery of loss after suction greater than standard open suction. In this way it could be possible to avoid pulmonary overdistension made by recruitment manoeuvres, often necessary after suction with an open system to recover the loss in FRC and PaO₂.