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Effect of PEEP and tidal volume on ventilation distribution and end-expiratory lung volume: a prospective experimental animal and pilot clinical study.

Zick G, Elke G, Becher T, Schädler D, Pulletz S, Freitag-Wolf S, Weiler N, Frerichs I - PLoS ONE (2013)

Bottom Line: In healthy animals, high compared to low VT increased C(RS) and ventilation in dependent lung regions implying tidal recruitment.ALI reduced C(RS) and EELV in all regions without changing ventilation distribution.Tidal recruitment and end-inspiratory overinflation can be assessed by EIT-based analysis of regional C(RS).

View Article: PubMed Central - PubMed

Affiliation: University Medical Center Schleswig-Holstein, Campus Kiel, Department of Anesthesiology and Intensive Care Medicine, Kiel, Germany. guenther.zick@uksh.de

ABSTRACT

Introduction: Lung-protective ventilation aims at using low tidal volumes (VT) at optimum positive end-expiratory pressures (PEEP). Optimum PEEP should recruit atelectatic lung regions and avoid tidal recruitment and end-inspiratory overinflation. We examined the effect of VT and PEEP on ventilation distribution, regional respiratory system compliance (C(RS)), and end-expiratory lung volume (EELV) in an animal model of acute lung injury (ALI) and patients with ARDS by using electrical impedance tomography (EIT) with the aim to assess tidal recruitment and overinflation.

Methods: EIT examinations were performed in 10 anaesthetized pigs with normal lungs ventilated at 5 and 10 ml/kg body weight VT and 5 cmH2O PEEP. After ALI induction, 10 ml/kg VT and 10 cmH2O PEEP were applied. Afterwards, PEEP was set according to the pressure-volume curve. Animals were randomized to either low or high VT ventilation changed after 30 minutes in a crossover design. Ventilation distribution, regional C(RS) and changes in EELV were analyzed. The same measures were determined in five ARDS patients examined during low and high VT ventilation (6 and 10 (8) ml/kg) at three PEEP levels.

Results: In healthy animals, high compared to low VT increased C(RS) and ventilation in dependent lung regions implying tidal recruitment. ALI reduced C(RS) and EELV in all regions without changing ventilation distribution. Pressure-volume curve-derived PEEP of 21±4 cmH2O (mean±SD) resulted in comparable increase in C(RS) in dependent and decrease in non-dependent regions at both VT. This implied that tidal recruitment was avoided but end-inspiratory overinflation was present irrespective of VT. In patients, regional C(RS) differences between low and high VT revealed high degree of tidal recruitment and low overinflation at 3±1 cmH2O PEEP. Tidal recruitment decreased at 10±1 cmH2O and was further reduced at 15±2 cmH(2)O PEEP.

Conclusions: Tidal recruitment and end-inspiratory overinflation can be assessed by EIT-based analysis of regional C(RS).

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Regional ventilation distribution.Examples of functional EIT scans of regional lung ventilation in animal 2 during all measurement time points (see Figure 1 for explanation). The orientation of the scans is indicated (ant., anterior; post., posterior). Panel A: Ventilated areas within the chest cross-section exhibit higher values of relative impedance change and are shown in red tones. In normal lungs (NL), symmetrical ventilation distribution between the right and left lung regions was found. With induction of acute lung injury (ALI), higher ventilation in the right lung region with pronounced ventilation in its ventral part and reduced left lung ventilation especially in its dorsal part were found. After PEEP was set 2 cm H2O above the lower inflection point (LIP) according to the pressure-volume curve, a shift in ventilation toward the dependent (dorsal) lung regions was observed. No obvious difference between ventilation with 10 ml/kg VT and inactive interventional lung assist (ILA) (high VT, no ILA) and ventilation with 5 ml/kg VT and active ILA (low VT, ILA) was detected. Panel B: Ventilation difference scans of the same animal. Red color indicates increase in regional ventilation, blue color shows the decrease in ventilation compared with baseline.
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pone-0072675-g002: Regional ventilation distribution.Examples of functional EIT scans of regional lung ventilation in animal 2 during all measurement time points (see Figure 1 for explanation). The orientation of the scans is indicated (ant., anterior; post., posterior). Panel A: Ventilated areas within the chest cross-section exhibit higher values of relative impedance change and are shown in red tones. In normal lungs (NL), symmetrical ventilation distribution between the right and left lung regions was found. With induction of acute lung injury (ALI), higher ventilation in the right lung region with pronounced ventilation in its ventral part and reduced left lung ventilation especially in its dorsal part were found. After PEEP was set 2 cm H2O above the lower inflection point (LIP) according to the pressure-volume curve, a shift in ventilation toward the dependent (dorsal) lung regions was observed. No obvious difference between ventilation with 10 ml/kg VT and inactive interventional lung assist (ILA) (high VT, no ILA) and ventilation with 5 ml/kg VT and active ILA (low VT, ILA) was detected. Panel B: Ventilation difference scans of the same animal. Red color indicates increase in regional ventilation, blue color shows the decrease in ventilation compared with baseline.

Mentions: Functional EIT scans were generated from each measurement using an established approach [19]. They showed the distribution of regional VT in the chest cross-section by calculating the tidal amplitudes of relative impedance change in 912 image pixels (Figure 2).


Effect of PEEP and tidal volume on ventilation distribution and end-expiratory lung volume: a prospective experimental animal and pilot clinical study.

Zick G, Elke G, Becher T, Schädler D, Pulletz S, Freitag-Wolf S, Weiler N, Frerichs I - PLoS ONE (2013)

Regional ventilation distribution.Examples of functional EIT scans of regional lung ventilation in animal 2 during all measurement time points (see Figure 1 for explanation). The orientation of the scans is indicated (ant., anterior; post., posterior). Panel A: Ventilated areas within the chest cross-section exhibit higher values of relative impedance change and are shown in red tones. In normal lungs (NL), symmetrical ventilation distribution between the right and left lung regions was found. With induction of acute lung injury (ALI), higher ventilation in the right lung region with pronounced ventilation in its ventral part and reduced left lung ventilation especially in its dorsal part were found. After PEEP was set 2 cm H2O above the lower inflection point (LIP) according to the pressure-volume curve, a shift in ventilation toward the dependent (dorsal) lung regions was observed. No obvious difference between ventilation with 10 ml/kg VT and inactive interventional lung assist (ILA) (high VT, no ILA) and ventilation with 5 ml/kg VT and active ILA (low VT, ILA) was detected. Panel B: Ventilation difference scans of the same animal. Red color indicates increase in regional ventilation, blue color shows the decrease in ventilation compared with baseline.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3750001&req=5

pone-0072675-g002: Regional ventilation distribution.Examples of functional EIT scans of regional lung ventilation in animal 2 during all measurement time points (see Figure 1 for explanation). The orientation of the scans is indicated (ant., anterior; post., posterior). Panel A: Ventilated areas within the chest cross-section exhibit higher values of relative impedance change and are shown in red tones. In normal lungs (NL), symmetrical ventilation distribution between the right and left lung regions was found. With induction of acute lung injury (ALI), higher ventilation in the right lung region with pronounced ventilation in its ventral part and reduced left lung ventilation especially in its dorsal part were found. After PEEP was set 2 cm H2O above the lower inflection point (LIP) according to the pressure-volume curve, a shift in ventilation toward the dependent (dorsal) lung regions was observed. No obvious difference between ventilation with 10 ml/kg VT and inactive interventional lung assist (ILA) (high VT, no ILA) and ventilation with 5 ml/kg VT and active ILA (low VT, ILA) was detected. Panel B: Ventilation difference scans of the same animal. Red color indicates increase in regional ventilation, blue color shows the decrease in ventilation compared with baseline.
Mentions: Functional EIT scans were generated from each measurement using an established approach [19]. They showed the distribution of regional VT in the chest cross-section by calculating the tidal amplitudes of relative impedance change in 912 image pixels (Figure 2).

Bottom Line: In healthy animals, high compared to low VT increased C(RS) and ventilation in dependent lung regions implying tidal recruitment.ALI reduced C(RS) and EELV in all regions without changing ventilation distribution.Tidal recruitment and end-inspiratory overinflation can be assessed by EIT-based analysis of regional C(RS).

View Article: PubMed Central - PubMed

Affiliation: University Medical Center Schleswig-Holstein, Campus Kiel, Department of Anesthesiology and Intensive Care Medicine, Kiel, Germany. guenther.zick@uksh.de

ABSTRACT

Introduction: Lung-protective ventilation aims at using low tidal volumes (VT) at optimum positive end-expiratory pressures (PEEP). Optimum PEEP should recruit atelectatic lung regions and avoid tidal recruitment and end-inspiratory overinflation. We examined the effect of VT and PEEP on ventilation distribution, regional respiratory system compliance (C(RS)), and end-expiratory lung volume (EELV) in an animal model of acute lung injury (ALI) and patients with ARDS by using electrical impedance tomography (EIT) with the aim to assess tidal recruitment and overinflation.

Methods: EIT examinations were performed in 10 anaesthetized pigs with normal lungs ventilated at 5 and 10 ml/kg body weight VT and 5 cmH2O PEEP. After ALI induction, 10 ml/kg VT and 10 cmH2O PEEP were applied. Afterwards, PEEP was set according to the pressure-volume curve. Animals were randomized to either low or high VT ventilation changed after 30 minutes in a crossover design. Ventilation distribution, regional C(RS) and changes in EELV were analyzed. The same measures were determined in five ARDS patients examined during low and high VT ventilation (6 and 10 (8) ml/kg) at three PEEP levels.

Results: In healthy animals, high compared to low VT increased C(RS) and ventilation in dependent lung regions implying tidal recruitment. ALI reduced C(RS) and EELV in all regions without changing ventilation distribution. Pressure-volume curve-derived PEEP of 21±4 cmH2O (mean±SD) resulted in comparable increase in C(RS) in dependent and decrease in non-dependent regions at both VT. This implied that tidal recruitment was avoided but end-inspiratory overinflation was present irrespective of VT. In patients, regional C(RS) differences between low and high VT revealed high degree of tidal recruitment and low overinflation at 3±1 cmH2O PEEP. Tidal recruitment decreased at 10±1 cmH2O and was further reduced at 15±2 cmH(2)O PEEP.

Conclusions: Tidal recruitment and end-inspiratory overinflation can be assessed by EIT-based analysis of regional C(RS).

Show MeSH
Related in: MedlinePlus