Gas exchange impairment induced by open suctioning in ARDS: impact of permissive hypercapnia

Background and aims

There is still controversy over the impact of open suctioning (OS) on gas exchange and the duration of suctioning. The goal of this physiologic study was to determine whether hypercarbia occurs following the use of OS in a lung lavage injured sheep and whether the level of baseline PaCO₂ and duration of suctioning impacts gas exchange.

Methods

Six female sheep were lung injured by isotonic saline lavage until their PaO₂ dropped to 100 mmHg on an FIO₂ of 1.0, PEEP 5 cmH₂O and VT 10 ml/kg. Then the VT was decreased to 6 ml/kg. RR was set to establish a PaCO₂ of 40 mmHg or 80 mmHg. OS was performed on each animal. PaCO₂ was randomly adjusted to 40 mmHg and 80 mmHg and the suction time randomly set at 10 s and 30 s. Before each of the four experimental conditions animals received recruitment maneuvers of 40 cmH₂O CPAP for 40 s to establish a volume history, following by baseline for 15 min where FiO₂ and PEEP were set based on the ARDSnet FiO₂/PEEP [1]. OS was performed using a 14 Fr, TrachCare catheter at a pressure of -100 mmHg. Mean arterial blood pressure, heart rate, pulmonary and arterial wedge pressure, cardiac output, and arterial blood gases, were measured before, 1 min and then every 2 min after OS for 30 min.

Results

During suctioning at 80 mmHg PaCO₂ at both 10 s and 30 s suctioning times, the PaCO₂ increased at 1, 15 and 31 min post suctioning (P < 0.05). PaCO₂ also increased at 1 min when the baseline PaCO₂ was 40 mmHg and the suction time was 30 s (P < 0.05) (Fig. 1). PaO₂ decreased 1 min post suctioning in all conditions but recovered by 15 min. Hemodynamics did not demonstrate any significance differences regardless of the experimental condition.

Figure 1

Comparison of PaCO₂ between groups.

Conclusions

OS causes in a significant increase in baseline PaCO₂ during baseline hypercapnia and when suctioning is applied for 30 s. OS regardless of conditions results in a decrease in PaO₂ that recovers rapidly post suctioning.