Lung and chest wall mechanics in mechanically ventilated COPD patients

Guérin, Claude; Coussa, M. L.; Eissa, N. Tony; Corbeil, C.; Chassé, M.; Braidy, J.; Matar, Nadim; Milic–Emili, J.

doi:10.1152/jappl.1993.74.4.1570

Cited by 115 publications

(113 citation statements)

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“…In order to evaluate this dependency, it is necessary to know the values of the parameters in this model [2±4, 7,9]. The clinical utility of the present method lies in the possibility of performing only a few bedside measurements in order to obtain viscoelastic constants.…”

Section: Discussionmentioning

confidence: 99%

Bedside assessment of respiratory viscoelastic properties in ventilated patients

Antonaglia¹,

Peratoner²,

Simoni³

et al. 2000

Eur Respir J

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Viscoelasticity represents an important component of respiratory mechanics, being responsible, in some cases, for most of the pressure dissipated during breathing. Hitherto the methods available for determining the viscoelastic properties have been simplified, but are still time-demanding and depend on a great deal of calculation. In this study, a simple means of determining respiratory viscoelastic properties during mechanical ventilation was introduced.The viscoelastic constants of the respiratory system, modelled as a Maxwell body, were studied in 17 normal subjects and seven patients with acute lung injury (ALI) using two end-inspiratory occlusions; one with a short inspiratory time (tI) to determine the elastic component of viscoelasticity and the other with a long tI to assess the resistive component of viscoelasticity.The results were reproducible and similar to those provided by the previously described multiple-breath method (MB) Viscoelasticity represents an important component of respiratory mechanics, being responsible, in some cases, for most of the pressure dissipated during breathing. In order to study the viscoelastic behaviour of the respiratory system, it is necessary to assess the pressure developed by the viscoelastic components. Direct measurement of the viscoelastic inspiratory pressure can be performed by the technique of rapid end-inspiratory airway occlusion and the viscoelastic behaviour interpreted according to a Maxwell body. This linear viscoelastic model has been shown to provide an accurate description of the time-dependency of resistance and elastance of the respiratory system observed in normal animal [1] and human lungs [2] In this model, the viscoelastic properties which impact such time-dependency can be characterized by two parameters, the theoretical maximal viscoelastic resistance (R2) and elastance (E2). A third useful variable, the viscoelastic time constant (t2), can also be obtained from R2/E2 [3]. Using the technique of rapid airway occlusion (RAO) during constant-flow (V') inflation, it has been possible to determine the values of these viscoelastic constants for the lung, chest wall and total respiratory system in normal mechanically ventilated humans [3±5] and experimental animals [1,6], based on either of the following functions:where Pvisc(t) is the viscoelastic pressure (Pvisc) dissipated within the lung, chest wall or both during constant-V' inflation started from the relaxed volume of the respiratory system, t is time during lung inflation and DRrs is viscoelastic resistance, obtained by dividing both sides of Equation 1 by V' [3]. This analysis, however, is timeconsuming and technically complex because it requires either a series of isovolumic inflations with different inspiratory V' , or multiple iso-V' inflations with different volumes [3,6]. As a result, the above analysis has been used only in a limited number of studies on normal subjects [3±5] and patients [7±9]. Recently, a single-breath method was proposed for assessing the viscoelastic prope...

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Section: Discussionmentioning

confidence: 99%

Bedside assessment of respiratory viscoelastic properties in ventilated patients

Antonaglia¹,

Peratoner²,

Simoni³

et al. 2000

Eur Respir J

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“…Accordingly, in COPD, the thresholds for fR and V 'E were necessarily lower than those obtained by YANG and TOBIN [1] in a nonhomogeneous population (table 2). In the present COPD patients, the Crs,st measured during mechanical ventilation were relatively high (table 3), reflecting the fact that, in COPD patients with ARF, the Crs,st does not differ significantly from that of normal subjects [4,10], except on the first day of mechanical ventilation, when they exhibit marked dynamic hyperinflation and hence their VT impinges on the flat upper part of the static volume/pressure curve of the respiratory system [2]. It should be noted, however, that during spontaneous breathing trials COPD patients may exhibit markedly enhanced dynamic hyperinflation (DH) with concomitant decrease in Crs,st.…”

Section: Discussionmentioning

confidence: 47%

Predictors of weaning outcome in chronic obstructive pulmonary disease patients

Alvisi¹,

Volta²,

Er³

et al. 2000

Eur Respir J

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Several threshold values for predicting weaning outcome from mechanical ventilation have been proposed. These values, however, have been obtained in nonhomogeneous patient populations. The aim of the present study was to determine the threshold values in chronic obstructive pulmonary disease (COPD) patients and compare them to those reported for nonhomogeneous patient populations.The initial weaning trial included 81 COPD patients. Fifty-three of them underwent a successful weaning trial, whereas 28 failed it. The latter were enrolled into the present investigation, and were restudied during a subsequent successful trial. The weaning indices used were those reported in the literature.The threshold values obtained were within 10% of those reported for a nonhomogeneous patients population only for tidal volume and effective compliance. The classification error was <20% for maximal inspiratory pressure (MIP), occluded inspiratory pressure swing (DPI)/MIP, rapid and shallow breathing (respiratory frequency/tidal volume), and compliance, rate, oxygenation, pressure index (CROP), whereas the area under the receiver operating characteristic curves was >0.9 only for DPI/MIP and CROP.In conclusion, the threshold values obtained in chronic obstructive pulmonary disease patients who failed the first weaning attempt differed from those previously reported. Although a gold standard weaning index is not available for chronic obstructive pulmonary disease patients, the occluded inspiratory pressure swing/ maximal inspiratory pressure and compliance, rate, oxygenation, pressure index may be candidates for such a role. Eur Respir J 2000; 15: 656±662.

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“…Dynamic Wrs was further partitioned into two components by the ∆V-P1 relationship, the difference between Pdyn and P1 along the horizontal axis representing the immediate drop in pressure after airway occlusion, and that between P1 and Pst the slow decay during the occlusion. The area enclosed between the ∆V-tracheal Pdyn (Pdyn,tr) and ∆V-tracheal P1 (P1,tr) relationships should essentially represent work done to overcome airway resistance (Waw) [13,24], whilst the difference between Wdyn,rs and Waw reflects the additional work (∆Wrs) done on the respiratory system as a result of time constant inequality and viscoelastic tissue behaviour [12]. Because no immediate drop was discernible on the Poes tracings of single airway occlusions and hence no ∆V-P1 relationship could be drawn for the chest wall, dynamic inspiratory pressure of the chest wall (WI,dyn,w) should essentially represent the additional work done on the chest wall (∆Ww).…”

Section: Resultsmentioning

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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Lung and chest wall mechanics in mechanically ventilated COPD patients

Cited by 115 publications

References 0 publications

Bedside assessment of respiratory viscoelastic properties in ventilated patients

Bedside assessment of respiratory viscoelastic properties in ventilated patients

Predictors of weaning outcome in chronic obstructive pulmonary disease patients

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

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