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Overdistension in ventilated children.

Nève V, Leclerc F, de la Roque ED, Leteurtre S, Riou Y - Crit Care (2001)

Bottom Line: Young children may be more susceptible than adults to overdistension, and individual evaluation of the effects of ventilator settings is therefore required.Three studies have applied indices for the detection of overdistension to dynamic V-P curves in ventilated children.Two of those studies compared these indices to those obtained using a reference technique ([quasi]-static V-P curves), and suggested that the c coefficient of a second order polynomial equation (SOPE) and the ratio of the volume-dependent elastance to total dynamic elastance (%E2) were suitable indices for estimating overdistension.

View Article: PubMed Central - HTML - PubMed

Affiliation: Service de Réanimation Pédiatrique, Centre Hospitalier et Universitaire de Lille, Lille, France. fleclerc@chru-lille.fr

ABSTRACT
Ventilating patients with acute respiratory failure according to standardized recommendations can lead to varying volume-pressure (V-P) relationships and overdistension. Young children may be more susceptible than adults to overdistension, and individual evaluation of the effects of ventilator settings is therefore required. Three studies have applied indices for the detection of overdistension to dynamic V-P curves in ventilated children. Two of those studies compared these indices to those obtained using a reference technique ([quasi]-static V-P curves), and suggested that the c coefficient of a second order polynomial equation (SOPE) and the ratio of the volume-dependent elastance to total dynamic elastance (%E2) were suitable indices for estimating overdistension.

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Detection of overdistension using the C20/C ratio and c coefficient on the same dynamic volume–pressure curves of two representative patients. The C20/C ratio was calculated on the inspiratory part of the V-P loop obtained during mechanical ventilation. It is the ratio of the compliance calculated from the last 20% of the inspiratory V-P curve (C20) to the total compliance calculated from the entire slope of the inspiratory curve (C) between zero flow points. A C20/C ratio below 0.80 is indicative of overdistension [20]. The nonlinear coefficient c of a SOPE (see Equation 5) was fitted to the V-P data obtained during a period of constant flow. The sign of this coefficient c describes the curvature of the V-P curve. When a convex shape with a progressive decrease in slope with increasing inflation volume is observed, the coefficient c is negative, indicating overdistension; when a concave shape with a progressive increase in slope with increasing inflation volume is observed, the coefficient c is positive [23]. For patient A, the positive value of coefficient c and the C20/C ratio in excess of 0.80 were not indicative of overdistension. For patient B, the negative value of coefficient c and the C20/C ratio below 0.80 were both indicative of overdistension.
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Figure 1: Detection of overdistension using the C20/C ratio and c coefficient on the same dynamic volume–pressure curves of two representative patients. The C20/C ratio was calculated on the inspiratory part of the V-P loop obtained during mechanical ventilation. It is the ratio of the compliance calculated from the last 20% of the inspiratory V-P curve (C20) to the total compliance calculated from the entire slope of the inspiratory curve (C) between zero flow points. A C20/C ratio below 0.80 is indicative of overdistension [20]. The nonlinear coefficient c of a SOPE (see Equation 5) was fitted to the V-P data obtained during a period of constant flow. The sign of this coefficient c describes the curvature of the V-P curve. When a convex shape with a progressive decrease in slope with increasing inflation volume is observed, the coefficient c is negative, indicating overdistension; when a concave shape with a progressive increase in slope with increasing inflation volume is observed, the coefficient c is positive [23]. For patient A, the positive value of coefficient c and the C20/C ratio in excess of 0.80 were not indicative of overdistension. For patient B, the negative value of coefficient c and the C20/C ratio below 0.80 were both indicative of overdistension.

Mentions: Ranieri et al [23], in adult patients with ARDS, showed that the sign of this coefficient c describes the curvature of the V-P curve. When a convex shape with a progressive decrease in slope with increasing inflation volume was observed, the coefficient c was negative, indicating overdistension. When a concave shape with a progressive increase in slope with increasing inflation volume was observed, the coefficient c was positive. Figure 1 illustrates the detection of overdistension using the C20/C ratio and coefficient c in two representative patients.


Overdistension in ventilated children.

Nève V, Leclerc F, de la Roque ED, Leteurtre S, Riou Y - Crit Care (2001)

Detection of overdistension using the C20/C ratio and c coefficient on the same dynamic volume–pressure curves of two representative patients. The C20/C ratio was calculated on the inspiratory part of the V-P loop obtained during mechanical ventilation. It is the ratio of the compliance calculated from the last 20% of the inspiratory V-P curve (C20) to the total compliance calculated from the entire slope of the inspiratory curve (C) between zero flow points. A C20/C ratio below 0.80 is indicative of overdistension [20]. The nonlinear coefficient c of a SOPE (see Equation 5) was fitted to the V-P data obtained during a period of constant flow. The sign of this coefficient c describes the curvature of the V-P curve. When a convex shape with a progressive decrease in slope with increasing inflation volume is observed, the coefficient c is negative, indicating overdistension; when a concave shape with a progressive increase in slope with increasing inflation volume is observed, the coefficient c is positive [23]. For patient A, the positive value of coefficient c and the C20/C ratio in excess of 0.80 were not indicative of overdistension. For patient B, the negative value of coefficient c and the C20/C ratio below 0.80 were both indicative of overdistension.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC137279&req=5

Figure 1: Detection of overdistension using the C20/C ratio and c coefficient on the same dynamic volume–pressure curves of two representative patients. The C20/C ratio was calculated on the inspiratory part of the V-P loop obtained during mechanical ventilation. It is the ratio of the compliance calculated from the last 20% of the inspiratory V-P curve (C20) to the total compliance calculated from the entire slope of the inspiratory curve (C) between zero flow points. A C20/C ratio below 0.80 is indicative of overdistension [20]. The nonlinear coefficient c of a SOPE (see Equation 5) was fitted to the V-P data obtained during a period of constant flow. The sign of this coefficient c describes the curvature of the V-P curve. When a convex shape with a progressive decrease in slope with increasing inflation volume is observed, the coefficient c is negative, indicating overdistension; when a concave shape with a progressive increase in slope with increasing inflation volume is observed, the coefficient c is positive [23]. For patient A, the positive value of coefficient c and the C20/C ratio in excess of 0.80 were not indicative of overdistension. For patient B, the negative value of coefficient c and the C20/C ratio below 0.80 were both indicative of overdistension.
Mentions: Ranieri et al [23], in adult patients with ARDS, showed that the sign of this coefficient c describes the curvature of the V-P curve. When a convex shape with a progressive decrease in slope with increasing inflation volume was observed, the coefficient c was negative, indicating overdistension. When a concave shape with a progressive increase in slope with increasing inflation volume was observed, the coefficient c was positive. Figure 1 illustrates the detection of overdistension using the C20/C ratio and coefficient c in two representative patients.

Bottom Line: Young children may be more susceptible than adults to overdistension, and individual evaluation of the effects of ventilator settings is therefore required.Three studies have applied indices for the detection of overdistension to dynamic V-P curves in ventilated children.Two of those studies compared these indices to those obtained using a reference technique ([quasi]-static V-P curves), and suggested that the c coefficient of a second order polynomial equation (SOPE) and the ratio of the volume-dependent elastance to total dynamic elastance (%E2) were suitable indices for estimating overdistension.

View Article: PubMed Central - HTML - PubMed

Affiliation: Service de Réanimation Pédiatrique, Centre Hospitalier et Universitaire de Lille, Lille, France. fleclerc@chru-lille.fr

ABSTRACT
Ventilating patients with acute respiratory failure according to standardized recommendations can lead to varying volume-pressure (V-P) relationships and overdistension. Young children may be more susceptible than adults to overdistension, and individual evaluation of the effects of ventilator settings is therefore required. Three studies have applied indices for the detection of overdistension to dynamic V-P curves in ventilated children. Two of those studies compared these indices to those obtained using a reference technique ([quasi]-static V-P curves), and suggested that the c coefficient of a second order polynomial equation (SOPE) and the ratio of the volume-dependent elastance to total dynamic elastance (%E2) were suitable indices for estimating overdistension.

Show MeSH
Related in: MedlinePlus