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Measurement of pressure-volume curves in patients on mechanical ventilation: methods and significance.

Lu Q, Rouby JJ - Crit Care (2000)

Bottom Line: Physiological background concerning mechanics of the respiratory system, techniques of measurement and clinical implications of pressure-volume curve measurement in mechanically ventilated patients are discussed in the present review.Evidence suggests that the continuous flow method is a simple and reliable technique for measuring pressure-volume curves at the bedside.In patients with acute respiratory failure, determination of lower and upper inflection points and measurement of respiratory compliance should become a part of the routine assessment of lung injury severity, allowing a bedside monitoring of the evolution of the lung disease and an optimization of mechanical ventilation.

View Article: PubMed Central - HTML - PubMed

Affiliation: University of Paris VI, Paris, France. qin.lu@psl.ap-hop-paris.fr

ABSTRACT
Physiological background concerning mechanics of the respiratory system, techniques of measurement and clinical implications of pressure-volume curve measurement in mechanically ventilated patients are discussed in the present review. The significance of lower and upper inflection points, the assessment of positive end-expiratory pressure (PEEP)-induced alveolar recruitment and overdistension and rationale for optimizing ventilatory settings in patients with acute lung injury are presented. Evidence suggests that the continuous flow method is a simple and reliable technique for measuring pressure-volume curves at the bedside. In patients with acute respiratory failure, determination of lower and upper inflection points and measurement of respiratory compliance should become a part of the routine assessment of lung injury severity, allowing a bedside monitoring of the evolution of the lung disease and an optimization of mechanical ventilation.

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Inspiratory occlusion technique as described by Levy et				al [8]. The patient is on controlled ventilation				with a constant flow. Between two measurements, the lung volume is standardized				by maintaining the ventilatory parameters constant. The intrinsic PEEP (PEEPi)				is determined before each inflation followed by an end-inspiratory occlusion.				The plateau pressure (Pst) is obtained a few seconds after the occlusion. From				Levy et al [8].
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Figure 1: Inspiratory occlusion technique as described by Levy et al [8]. The patient is on controlled ventilation with a constant flow. Between two measurements, the lung volume is standardized by maintaining the ventilatory parameters constant. The intrinsic PEEP (PEEPi) is determined before each inflation followed by an end-inspiratory occlusion. The plateau pressure (Pst) is obtained a few seconds after the occlusion. From Levy et al [8].

Mentions: The inspiratory occlusion technique was developed in the late 1980s and was initially described by Levy et al [8]. It consists of measurement of plateau pressures that correspond to different tidal volumes during successive end-inspiratory occlusions. This technique is performed using a mechanical ventilator equipped with facilities for end-inspiratory and end-expiratory occlusions. It is not necessary to disconnect the patient from the ventilator, and the loss of volume due to lung oxygen uptake is negligible because each measurement lasts only 3 s. The patient is ventilated in a volume-controlled mode with a constant flow. Between two measurements, the ventilation is normalized by using the same ventilatory parameters. The different tidal volumes are administered in a randomized sequence. These tidal volumes are obtained by changing the respiratory rate while maintaining the inspiratory flow constant (lengthening or shortening the duration of inflation). The intrinsic PEEP is determined before each inflation to ensure that the lung volume and the end-expiratory pressure are stable. The occlusion manoeuvre is performed at end-inspiration and the plateau pressure is measured after a few seconds of occlusion. The pressure-volume curve is constructed from the different plateau pressures that correspond to the administered volumes (Fig. 1).


Measurement of pressure-volume curves in patients on mechanical ventilation: methods and significance.

Lu Q, Rouby JJ - Crit Care (2000)

Inspiratory occlusion technique as described by Levy et				al [8]. The patient is on controlled ventilation				with a constant flow. Between two measurements, the lung volume is standardized				by maintaining the ventilatory parameters constant. The intrinsic PEEP (PEEPi)				is determined before each inflation followed by an end-inspiratory occlusion.				The plateau pressure (Pst) is obtained a few seconds after the occlusion. From				Levy et al [8].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC137332&req=5

Figure 1: Inspiratory occlusion technique as described by Levy et al [8]. The patient is on controlled ventilation with a constant flow. Between two measurements, the lung volume is standardized by maintaining the ventilatory parameters constant. The intrinsic PEEP (PEEPi) is determined before each inflation followed by an end-inspiratory occlusion. The plateau pressure (Pst) is obtained a few seconds after the occlusion. From Levy et al [8].
Mentions: The inspiratory occlusion technique was developed in the late 1980s and was initially described by Levy et al [8]. It consists of measurement of plateau pressures that correspond to different tidal volumes during successive end-inspiratory occlusions. This technique is performed using a mechanical ventilator equipped with facilities for end-inspiratory and end-expiratory occlusions. It is not necessary to disconnect the patient from the ventilator, and the loss of volume due to lung oxygen uptake is negligible because each measurement lasts only 3 s. The patient is ventilated in a volume-controlled mode with a constant flow. Between two measurements, the ventilation is normalized by using the same ventilatory parameters. The different tidal volumes are administered in a randomized sequence. These tidal volumes are obtained by changing the respiratory rate while maintaining the inspiratory flow constant (lengthening or shortening the duration of inflation). The intrinsic PEEP is determined before each inflation to ensure that the lung volume and the end-expiratory pressure are stable. The occlusion manoeuvre is performed at end-inspiration and the plateau pressure is measured after a few seconds of occlusion. The pressure-volume curve is constructed from the different plateau pressures that correspond to the administered volumes (Fig. 1).

Bottom Line: Physiological background concerning mechanics of the respiratory system, techniques of measurement and clinical implications of pressure-volume curve measurement in mechanically ventilated patients are discussed in the present review.Evidence suggests that the continuous flow method is a simple and reliable technique for measuring pressure-volume curves at the bedside.In patients with acute respiratory failure, determination of lower and upper inflection points and measurement of respiratory compliance should become a part of the routine assessment of lung injury severity, allowing a bedside monitoring of the evolution of the lung disease and an optimization of mechanical ventilation.

View Article: PubMed Central - HTML - PubMed

Affiliation: University of Paris VI, Paris, France. qin.lu@psl.ap-hop-paris.fr

ABSTRACT
Physiological background concerning mechanics of the respiratory system, techniques of measurement and clinical implications of pressure-volume curve measurement in mechanically ventilated patients are discussed in the present review. The significance of lower and upper inflection points, the assessment of positive end-expiratory pressure (PEEP)-induced alveolar recruitment and overdistension and rationale for optimizing ventilatory settings in patients with acute lung injury are presented. Evidence suggests that the continuous flow method is a simple and reliable technique for measuring pressure-volume curves at the bedside. In patients with acute respiratory failure, determination of lower and upper inflection points and measurement of respiratory compliance should become a part of the routine assessment of lung injury severity, allowing a bedside monitoring of the evolution of the lung disease and an optimization of mechanical ventilation.

Show MeSH
Related in: MedlinePlus