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Effect of extracorporeal CO2 removal on respiratory rate in spontaneously breathing patients with chronic obstructive pulmonary disease exacerbation

Introduction

During severe exacerbation of chronic obstructive pulmonary disease (COPD) tachypnea, as a consequence of respiratory acidosis, and airflow limitation, due to small airway obstruction, lead to lung hyperinflation, respiratory distress and gas exchange impairment. Invasive mechanical ventilation could worsen lung hyperinflation and produce a vicious circle. We investigated whether increasing extracorporeal carbon dioxide removal (ECCO2 Cl) could reduce the respiratory rate (RR), so prolonging time for lung emptying and allowing resolution of hyperinflation.

Methods

Six patients with COPD exacerbation with respiratory acidosis (PaCO2 83 ± 27 mmHg, pH 7.19 ± 0.1) and tachypnea (RR 39 ± 5) despite maximal non-invasive ventilation underwent venovenous extracorporeal membrane oxygenation (VV-ECMO). All patients were awake and spontaneously breathing an adequate air-oxygen mixture to correct hypoxemia (PaO2 72 ± 27 mmHg). While keeping the blood flow stable (2.9 ± 0.5 l/minute), we changed the gas flow of the artificial lung to modify the extracorporeal CO2 clearance as a percentage of total patient CO2 production (% ECCO2 Cl/total VCO2) and we observed the variations of RR. We recorded RR at three levels of gas flow in each patient (Figure 1).

Figure 1
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Results

In all patients RR decreased with the increase of extracorporeal CO2 removal and a negative correlation was found between RR and ECCO2 Cl/total VCO2 (r 2 = 0.42, P < 0.01). In all patients we were able to obtain a reduction of RR below 15 (28 ± 4 vs. 8 ± 4, RR at low gas flow vs. RR at maximal gas flow, P < 0.001). The selected maximal gas flow was variable between different patients (6.7 ± 2 l/minute), corresponding to different levels of ECCO2 Cl/total VCO2 (83 ± 17%, range 53 to 100%) and RR response (8 ± 4, range 5 to 14).

Conclusion

In patients with COPD exacerbation, who failed noninvasive ventilation, VV-ECMO allows one to maintain spontaneous breathing. Titration of extracorporeal CO2 removal leads to control RR. This approach could interrupt the vicious circle of dynamic hyperinflation and allow the deflation of lung parenchyma.

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Correspondence to E Spinelli.

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Spinelli, E., Crotti, S., Zacchetti, L. et al. Effect of extracorporeal CO2 removal on respiratory rate in spontaneously breathing patients with chronic obstructive pulmonary disease exacerbation. Crit Care 17, P128 (2013). https://doi.org/10.1186/cc12066

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Keywords

  • Chronic Obstructive Pulmonary Disease
  • Respiratory Rate
  • Chronic Obstructive Pulmonary Disease Exacerbation
  • Respiratory Acidosis
  • Invasive Mechanical Ventilation