Respiratory acidosis during bronchoscopy-guided percutaneous dilatational tracheostomy: impact of ventilator settings and endotracheal tube size.

BACKGROUND: The current study investigates the effect of bronchoscopy-guided percutaneous dilatational tracheostomy (PDT) on the evolution of respiratory acidosis depending on endotracheal tube (ET) sizes. In addition, the impact of increasing tidal volumes during the intervention was investigated. METHODS: Two groups of ICU-patients undergoing bronchoscopy-guided PDT with varying tidal volumes and tube sizes were consecutively investigated: 6 ml/kg (N = 29, mean age 57.4 ± 14.5 years) and 12 ml/kg predicted body weight (N = 34, mean age 59.5 ± 12.8 years). RESULTS: The mean intervention time during all procedures was 10 ± 3 min. The combination of low tidal volumes and ETs of 7.5 mm internal diameter resulted in the most profound increase in PaCO2 (32.2 ± 11.6 mmHg) and decrease in pH-value (- 0.18 ± 0.05). In contrast, the combination of high tidal volumes and ETs of 8.5 mm internal diameter resulted in the least profound increase in PaCO2 (8.8 ± 9.0 mmHg) and decrease of pH (- 0.05 ± 0.04). The intervention-related increase in PaCO2 was significantly lower when using higher tidal volumes for larger ET: internal diameter 7.5, 8.0 and 8.5: P > 0.05, =0.006 and = 0.002, respectively. Transcutaneous PCO2 monitoring revealed steadily worsening hypercapnia during the intervention with a high correlation of 0.87 and a low bias of 0.7 ± 9.4 mmHg according to the Bland-Altman analysis when compared to PaCO2 measurements. CONCLUSIONS: Profound respiratory acidosis following bronchoscopy-guided PDT evolves in a rapid and dynamic process. Increasing the tidal volume from 6 to 12 ml/kg PBW was capable of attenuating the evolution of respiratory acidosis, but this effect was only evident when using larger ETs. TRIAL REGISTRATION: DRKS00011004 . Registered 20th September 2016.

[Step-by-Step tutorial of bedside percutaneous dilatational tracheostomy]. / Perkutane dilatative Tracheotomie ­ Schritt für Schritt.

Bedside percutaneous dilatational tracheostomy has become one of the most commonly used interventions in ICU medicine. Different techniques have been developed, but guidance of percutaneous dilatational tracheostomy by video bronchoscope has been suggested to be clinically reasonable for direct visualization. The current Step-by-Step tutorial gives a detailed instruction of the procedure with visualization of every single step offering tips and pitfalls of the procedure.

Control of respiratory drive by extracorporeal CO2 removal in acute exacerbation of COPD breathing on non-invasive NAVA.

BACKGROUND: Veno-venous extracorporeal CO2 removal (vv-ECCO2R) and non-invasive neurally adjusted ventilator assist (NIV-NAVA) are two promising techniques which may prevent complications related to prolonged invasive mechanical ventilation in patients with acute exacerbation of COPD. METHODS: A physiological study of the electrical activity of the diaphragm (Edi) response was conducted with varying degrees of extracorporeal CO2 removal to control the respiratory drive in patients with severe acute exacerbation of COPD breathing on NIV-NAVA. RESULTS: Twenty COPD patients (SAPS II 37 ± 5.6, age 57 ± 9 years) treated with vv-ECCO2R and supported by NIV-NAVA were studied during stepwise weaning of vv-ECCO2R. Based on dyspnea, tolerance, and blood gases, weaning from vv-ECCO2R was successful in 12 and failed in eight patients. Respiratory drive (measured via the Edi) increased to 19 ± 10 µV vs. 56 ± 20 µV in the successful and unsuccessful weaning groups, respectively, resulting in all patients keeping their CO2 and pH values stable. Edi was the best predictor for vv-ECCO2R weaning failure (ROC analysis AUC 0.95), whereas respiratory rate, rapid shallow breathing index, and tidal volume had lower predictive values. Eventually, 19 patients were discharged home, while one patient died. Mortality at 90 days and 180 days was 15 and 25%, respectively. CONCLUSIONS: This study demonstrates for the first time the usefulness of the Edi signal to monitor and guide patients with severe acute exacerbation of COPD on vv-ECCO2R and NIV-NAVA. The Edi during vv-ECCO2R weaning was found to be the best predictor of tolerance to removing vv-ECCO2R.

Impact of sweep gas flow on extracorporeal CO2 removal (ECCO2R).

BACKGROUND: Veno-venous extracorporeal carbon dioxide (CO2) removal (vv-ECCO2R) is increasingly being used in the setting of acute respiratory failure. Blood flow rates range in clinical practice from 200 mL/min to more than 1500 mL/min, and sweep gas flow rates range from less than 1 to more than 10 L/min. The present porcine model study was aimed at determining the impact of varying sweep gas flow rates on CO2 removal under different blood flow conditions and membrane lung surface areas. METHODS: Two different membrane lungs, with surface areas of 0.4 and 0.8m2, were used in nine pigs with experimentally-induced hypercapnia. During each experiment, the blood flow was increased stepwise from 300 to 900 mL/min, with further increases up to 1800 mL/min with the larger membrane lung in steps of 300 mL/min. Sweep gas was titrated under each condition from 2 to 8 L/min in steps of 2 L/min. Extracorporeal CO2 elimination was normalized to a PaCO2 of 45 mmHg before the membrane lung. RESULTS: Reversal of hypercapnia was only feasible when blood flow rates above 900 mL/min were used with a membrane lung surface area of at least 0.8m2. The membrane lung with a surface of 0.4m2 allowed a maximum normalized CO2 elimination rate of 41 ± 6 mL/min with 8 L/min sweep gas flow and 900 mL blood flow/min. The increase in sweep gas flow from 2 to 8 L/min increased normalized CO2 elimination from 35 ± 5 to 41 ± 6 with 900 mL blood flow/min, whereas with lower blood flow rates, any increase was less effective, levelling out at 4 L sweep gas flow/min. The membrane lung with a surface area of 0.8m2 allowed a maximum normalized CO2 elimination rate of 101 ± 12 mL/min with increasing influence of sweep gas flow. The delta of normalized CO2 elimination increased from 4 ± 2 to 26 ± 7 mL/min with blood flow rates being increased from 300 to 1800 mL/min, respectively. CONCLUSIONS: The influence of sweep gas flow on the CO2 removal capacity of ECCO2R systems depends predominantly on blood flow rate and membrane lung surface area. In this model, considerable CO2 removal occurred only with the larger membrane lung surface of 0.8m2 and when blood flow rates of ≥ 900 mL/min were used.