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Adjusting tidal volume to stress index in an open lung condition optimizes ventilation and prevents overdistension in an experimental model of lung injury and reduced chest wall compliance.

Ferrando C, Suárez-Sipmann F, Gutierrez A, Tusman G, Carbonell J, García M, Piqueras L, Compañ D, Flores S, Soro M, Llombart A, Belda FJ - Crit Care (2015)

Bottom Line: PaCO2 was significantly higher in the Pplat-group (82 versus 53 mmHg, P = 0.01), with a resulting lower pH (7.19 versus 7.34, P = 0.01).We observed significant differences in VT (7.3 versus 5.4 mlKg(-1), P = 0.002) and Pplat values (30 versus 35 cmH2O, P = 0.001) between the Pplat-group and SI-group respectively.Cytokines and histopathology showed no differences.

View Article: PubMed Central - PubMed

Affiliation: Anesthesiology and Critical Care Department, Hospital Clínico Universitario of Valencia, Av. Blasco Ibañez, 17, Valencia, CP: 46010, Spain. cafeoranestesia@gmail.com.

ABSTRACT

Introduction: The stress index (SI), a parameter derived from the shape of the pressure-time curve, can identify injurious mechanical ventilation. We tested the hypothesis that adjusting tidal volume (VT) to a non-injurious SI in an open lung condition avoids hypoventilation while preventing overdistension in an experimental model of combined lung injury and low chest-wall compliance (Ccw).

Methods: Lung injury was induced by repeated lung lavages using warm saline solution, and Ccw was reduced by controlled intra-abdominal air-insufflation in 22 anesthetized, paralyzed and mechanically ventilated pigs. After injury animals were recruited and submitted to a positive end-expiratory pressure (PEEP) titration trial to find the PEEP level resulting in maximum compliance. During a subsequent four hours of mechanical ventilation, VT was adjusted to keep a plateau pressure (Pplat) of 30 cmH2O (Pplat-group, n = 11) or to a SI between 0.95 and 1.05 (SI-group, n = 11). Respiratory rate was adjusted to maintain a 'normal' PaCO2 (35 to 65 mmHg). SI, lung mechanics, arterial-blood gases haemodynamics pro-inflammatory cytokines and histopathology were analyzed. In addition Computed Tomography (CT) data were acquired at end expiration and end inspiration in six animals.

Results: PaCO2 was significantly higher in the Pplat-group (82 versus 53 mmHg, P = 0.01), with a resulting lower pH (7.19 versus 7.34, P = 0.01). We observed significant differences in VT (7.3 versus 5.4 mlKg(-1), P = 0.002) and Pplat values (30 versus 35 cmH2O, P = 0.001) between the Pplat-group and SI-group respectively. SI (1.03 versus 0.99, P = 0.42) and end-inspiratory transpulmonary pressure (PTP) (17 versus 18 cmH2O, P = 0.42) were similar in the Pplat- and SI-groups respectively, without differences in overinflated lung areas at end- inspiration in both groups. Cytokines and histopathology showed no differences.

Conclusions: Setting tidal volume to a non-injurious stress index in an open lung condition improves alveolar ventilation and prevents overdistension without increasing lung injury. This is in comparison with limited Pplat protective ventilation in a model of lung injury with low chest-wall compliance.

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Changes in lung mechanics during the experimental protocol. Dashed line: SI-group, pointed line: Pplat-group. Upper panel: compliance. Triangle: chest wall compliance, square: lung compliance, circle: respiratory system compliance. Lower panel: transpulmonary pressure. Triangle: end-inspiratory transpulmonary pressure, square: delta transpulmonary pressure, circle: end-expiratory transpulmonary pressure. T0: Baseline. T1: 60, T2: 120, T3: 180 and T4: 240 minutes after protocol defined ventilation was started. *P <0.05 Pplat-group versus SI-group.
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Fig2: Changes in lung mechanics during the experimental protocol. Dashed line: SI-group, pointed line: Pplat-group. Upper panel: compliance. Triangle: chest wall compliance, square: lung compliance, circle: respiratory system compliance. Lower panel: transpulmonary pressure. Triangle: end-inspiratory transpulmonary pressure, square: delta transpulmonary pressure, circle: end-expiratory transpulmonary pressure. T0: Baseline. T1: 60, T2: 120, T3: 180 and T4: 240 minutes after protocol defined ventilation was started. *P <0.05 Pplat-group versus SI-group.

Mentions: There was a significant difference in Pplat, VT, VE and RR between both groups at all measurement points (Table 1). While in the Pplat-group the Pplat was controlled with values = 30 cmH2O, in the SI-group Pplat was not controlled, with mean values around 35 cmH2O during the entire experimental protocol. The SI-group had higher VTs than the Pplat-group. The maximal differences in VT between groups were around 1 to 2 ml kg−1. No significant differences between groups were found in the SI, end-expiratory, end-inspiratory and delta PTP and for Crs, Ccw and CL (Table 1, Figure 2). None of the study animals developed auto-PEEP during the study period.Figure 2


Adjusting tidal volume to stress index in an open lung condition optimizes ventilation and prevents overdistension in an experimental model of lung injury and reduced chest wall compliance.

Ferrando C, Suárez-Sipmann F, Gutierrez A, Tusman G, Carbonell J, García M, Piqueras L, Compañ D, Flores S, Soro M, Llombart A, Belda FJ - Crit Care (2015)

Changes in lung mechanics during the experimental protocol. Dashed line: SI-group, pointed line: Pplat-group. Upper panel: compliance. Triangle: chest wall compliance, square: lung compliance, circle: respiratory system compliance. Lower panel: transpulmonary pressure. Triangle: end-inspiratory transpulmonary pressure, square: delta transpulmonary pressure, circle: end-expiratory transpulmonary pressure. T0: Baseline. T1: 60, T2: 120, T3: 180 and T4: 240 minutes after protocol defined ventilation was started. *P <0.05 Pplat-group versus SI-group.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4352239&req=5

Fig2: Changes in lung mechanics during the experimental protocol. Dashed line: SI-group, pointed line: Pplat-group. Upper panel: compliance. Triangle: chest wall compliance, square: lung compliance, circle: respiratory system compliance. Lower panel: transpulmonary pressure. Triangle: end-inspiratory transpulmonary pressure, square: delta transpulmonary pressure, circle: end-expiratory transpulmonary pressure. T0: Baseline. T1: 60, T2: 120, T3: 180 and T4: 240 minutes after protocol defined ventilation was started. *P <0.05 Pplat-group versus SI-group.
Mentions: There was a significant difference in Pplat, VT, VE and RR between both groups at all measurement points (Table 1). While in the Pplat-group the Pplat was controlled with values = 30 cmH2O, in the SI-group Pplat was not controlled, with mean values around 35 cmH2O during the entire experimental protocol. The SI-group had higher VTs than the Pplat-group. The maximal differences in VT between groups were around 1 to 2 ml kg−1. No significant differences between groups were found in the SI, end-expiratory, end-inspiratory and delta PTP and for Crs, Ccw and CL (Table 1, Figure 2). None of the study animals developed auto-PEEP during the study period.Figure 2

Bottom Line: PaCO2 was significantly higher in the Pplat-group (82 versus 53 mmHg, P = 0.01), with a resulting lower pH (7.19 versus 7.34, P = 0.01).We observed significant differences in VT (7.3 versus 5.4 mlKg(-1), P = 0.002) and Pplat values (30 versus 35 cmH2O, P = 0.001) between the Pplat-group and SI-group respectively.Cytokines and histopathology showed no differences.

View Article: PubMed Central - PubMed

Affiliation: Anesthesiology and Critical Care Department, Hospital Clínico Universitario of Valencia, Av. Blasco Ibañez, 17, Valencia, CP: 46010, Spain. cafeoranestesia@gmail.com.

ABSTRACT

Introduction: The stress index (SI), a parameter derived from the shape of the pressure-time curve, can identify injurious mechanical ventilation. We tested the hypothesis that adjusting tidal volume (VT) to a non-injurious SI in an open lung condition avoids hypoventilation while preventing overdistension in an experimental model of combined lung injury and low chest-wall compliance (Ccw).

Methods: Lung injury was induced by repeated lung lavages using warm saline solution, and Ccw was reduced by controlled intra-abdominal air-insufflation in 22 anesthetized, paralyzed and mechanically ventilated pigs. After injury animals were recruited and submitted to a positive end-expiratory pressure (PEEP) titration trial to find the PEEP level resulting in maximum compliance. During a subsequent four hours of mechanical ventilation, VT was adjusted to keep a plateau pressure (Pplat) of 30 cmH2O (Pplat-group, n = 11) or to a SI between 0.95 and 1.05 (SI-group, n = 11). Respiratory rate was adjusted to maintain a 'normal' PaCO2 (35 to 65 mmHg). SI, lung mechanics, arterial-blood gases haemodynamics pro-inflammatory cytokines and histopathology were analyzed. In addition Computed Tomography (CT) data were acquired at end expiration and end inspiration in six animals.

Results: PaCO2 was significantly higher in the Pplat-group (82 versus 53 mmHg, P = 0.01), with a resulting lower pH (7.19 versus 7.34, P = 0.01). We observed significant differences in VT (7.3 versus 5.4 mlKg(-1), P = 0.002) and Pplat values (30 versus 35 cmH2O, P = 0.001) between the Pplat-group and SI-group respectively. SI (1.03 versus 0.99, P = 0.42) and end-inspiratory transpulmonary pressure (PTP) (17 versus 18 cmH2O, P = 0.42) were similar in the Pplat- and SI-groups respectively, without differences in overinflated lung areas at end- inspiration in both groups. Cytokines and histopathology showed no differences.

Conclusions: Setting tidal volume to a non-injurious stress index in an open lung condition improves alveolar ventilation and prevents overdistension without increasing lung injury. This is in comparison with limited Pplat protective ventilation in a model of lung injury with low chest-wall compliance.

Show MeSH
Related in: MedlinePlus