A method for studying the static volume-pressure curves of the respiratory system during mechanical ventilation

Lévy, Patrick; Similowski, Thomas; Corbeil, C.; Albala, Maurizio Z.; Parienté, R; Milic–Emili, J.; Jonson, B.

doi:10.1016/0883-9441(89)90122-6

Cited by 103 publications

(62 citation statements)

References 9 publications

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“…In ALI/ARDS the intercept with the Pel,st axis equalled 0.24 kPa. The deviation from zero can represent auto-PEEP [33]. The value of the intercept was much smaller than "best PEEP" determined with the super syringe technique.…”

Section: Static Elastic Recoilmentioning

confidence: 94%

Respiratory mechanics in patients ventilated for critical lung disease

Beydon¹,

Svantesson²,

Brauer³

et al. 1996

Eur Respir J

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Respiratory mechanics, using flow interruption, was previously studied during the complete breath in healthy ventilated man, with numerical techniques relieving constraints regarding flow pattern. The classical linear model of nonNewtonian behaviour was found to be valid. The present study was extended to subjects with critical lung disease.Subjects with acute lung injury (ALI; n=2), acute respiratory distress syndrome (ARDS; n=4), and chronic obstructive pulmonary disease (COPD; n=3) were studied with and without positive end-expiratory pressure (PEEP). Functional residual capacity (FRC) was measured with sulphur hexafluoride (SF 6 ) wash-out.The static pressure-volume (P-V) curve was linear at zero end-expiratory pressure (ZEEP), but nonlinear at PEEP. Its hysteresis was nonsignificant. In ALI/ ARDS, PEEP increased lung volume by distension and recruitment, but only by distension in COPD. In ALI/ARDS, resistance was increased, at ZEEP. In COPD, resistance became extremely high during expiration at ZEEP. In ALI/ARDS at ZEEP, non-Newtonian behaviour, representing tissue stress relaxation and pendelluft, complied with the classical linear model. At PEEP, the non-Newtonian compliance became volume-dependent to an extent correlated to the nonlinearity of the static P-V curve. In COPD, non-Newtonian behaviour was adequately explained only with a model with different inspiratory and expiratory behaviour.The classical model of the respiratory system is valid in ALI/ARDS at ZEEP. More advanced models are needed at PEEP and in COPD. Eur Respir J., 1996, 9, 262-273 The flow interruption method has been used for studies both in ventilated humans and animals. The analysis has been based on a classical model. This model includes a Newtonian resistor (R) representing mainly airway resistance [1], a Newtonian capacitor (C) representing the static pressure-volume (P-V) relationship and a unit, that comprises a resistor (Rve) and a capacitor (Cve) ( fig. 1), which reflects non-Newtonian behaviour due to ventilation inhomogeneity (pendelluft) and tissue viscoelasticity (stress adaptation). It is well-known that these two phenomena cannot be distinguished on the basis of pressure and flow measured at the airway opening [1,2]. It will be discussed below that Rve and Cve probably represent tissue viscoelasticity to a greater extent than pendelluft in the present context. Rve and Cve will together be denoted the viscoelastic unit, to be considered in a broad sense. Due to methodological limitations, most studies have been limited to inspiration and constant flow [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Recently, we modified the flow interruption technique to improve accuracy of data acquisition and analysis [17]. Rve and Cve were estimated with a numerical iterative method. This method is not limited to a particular flow pattern. This enabled an analysis of the complete respiratory cycle. In normal subjects, the static P-V curve was linear. The static P-V curve did not show any hysteresis over the tidal volume...

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Section: Static Elastic Recoilmentioning

confidence: 94%

Respiratory mechanics in patients ventilated for critical lung disease

Beydon¹,

Svantesson²,

Brauer³

et al. 1996

Eur Respir J

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“…The rapid airway occlusion at constant flow inflation technique has been employed to assess response to bronchodilators in mechanically-ventilated patients [48]. This technique, which bas been extensively investigated by workers at the Meakins-Christie laboratories in Montreal, is readily applicable to modern ventilators having a constant inspiratory flow [49]. This method has been commonly used to characterize the bronchodilator response in mechanically-ventilated patients [8, 10-12, 39, 41, 50].…”

Section: Assessment Of the Bronchodilator Responsementioning

confidence: 99%

Bronchodilator delivery with metered-dose inhalers in mechanically-ventilated patients

Dhand¹,

Tobin²

1996

Eur Respir J

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“…In seven subjects, the total inspiratory work per breath (WI) and its components, namely static work (Wst), dynamic work due to viscous resistance (Wdyn) and additional tissue resistance (∆W), were assessed as previously described [12,13,15]. To this end, Pmax, P1 and Prs,st were also measured during 3-4 breaths in which the inflation volume was reduced to 0.27±0.03 and 0.14±0.03 L, respectively, while keeping inflation flow unchanged.…”

Section: Discussionmentioning

confidence: 99%

Lung and chest wall mechanics in patients with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia

et al. 1997

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Lung and chest wall mechanics in patients with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia. E. D 'Angelo, E. Calderini, F.M. Robatto, P. Puccio, J. Milic-Emili. ERS Journals Ltd 1997. ABSTRACT: The aim of this study was to assess the mechanical characteristics of the respiratory system in patients with acquired immune deficiency syndrome (AIDS) and acute respiratory distress syndrome (ARDS) caused by Pneumocystis carinii pneumonia (PCP).In 12 mechanically ventilated patients, total respiratory system mechanics was assessed using the technique of rapid airway occlusion during constant flow inflation, and was partitioned into lung and chest wall components using the oesophageal balloon technique. We measured interrupter resistance (Rint), which mainly reflects airway resistance, additional resistance (∆R) due to viscoelastic behaviour and time constant inequalities, and static elastance (Est). In addition, the static inflation volume-pressure (V-P) curve was assessed. In eight patients, computed tomography scans were performed within 2 days of the assessment of respiratory mechanics.Compared to values reported in the literature for normal subjects, Est and ∆R were markedly increased in AIDS patients with PCP, whilst Rint exhibited a relatively smaller increase. These changes, which involved only the lung and airways, were mainly due to the reduction of ventilated lung units, but additional factors were involved to cause independent modifications of lung stiffness, airway calibre, and viscoelastic properties. The changes in Rint, ∆R, and Est were similar to those observed in other studies on patients with ARDS of different aetiologies. At variance with common observations in the latter patients, none of the AIDS patients with PCP exhibited an inflection point on the static inflation V-P curve, suggesting little or no alveolar recruitment during lung inflation. This finding could be related to the distinctive histopathology of Pneumocystis carinii pneumonia. Indeed, computed tomography revealed homogeneous diffuse interstitial and alveolar infiltration rather than the dense, dependent opacities observed in other studies on acute respiratory distress syndrome of different aetiologies. Eur Respir J 1997; 10: 2343-2350 Pneumocystis carinii pneumonia (PCP) is the most frequent severe opportunistic infection in patients with acquired immunodeficiency syndrome (AIDS). It is held responsible for up to 85% of episodes of acute respiratory failure that occur in AIDS [1] and 80% of emergency admissions to intensive care units [2,3], with a reported mortality rate of 75-100% for patients requiring mechanical ventilation [4]. In a recent consensus conference [5], PCP was included, though not by unanimous decision, among the causes of acute respiratory distress syndrome (ARDS), once the following criteria are met: acute onset; arterial oxygen tension (Pa,O 2 )/inspiratory oxygen fraction (FI,O 2 ) <27 kPa (200 mmHg); bilateral infiltrates on chest radiographs; and no evidence of left atrial hyp...

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A method for studying the static volume-pressure curves of the respiratory system during mechanical ventilation

Cited by 103 publications

References 9 publications

Respiratory mechanics in patients ventilated for critical lung disease

Respiratory mechanics in patients ventilated for critical lung disease

Bronchodilator delivery with metered-dose inhalers in mechanically-ventilated patients

Lung and chest wall mechanics in patients with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia

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