Detection of flow limitation in mechanically ventilated patients

Lourens, M. S.; Berg, Benno van den; Hoogsteden, Henk C.; Bogaard, J. M.

doi:10.1007/s001340101010

Cited by 24 publications

(28 citation statements)

References 23 publications

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“…However, a review of the literature in this area suggests some alternative mechanisms through which paradoxic responses could occur (30). The waterfall theory is based on a onecompartment model, which is useful to explain some clinical observations but overly simplistic for explaining phenomena such as those observed here.…”

Section: Discussionmentioning

confidence: 96%

Paradoxical responses to positive end-expiratory pressure in patients with airway obstruction during controlled ventilation*

Caramez

Borges

Tucci

et al. 2005

Critical Care Medicine

116

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Objective-To reevaluate the clinical impact of external positive end-expiratory pressure (external-PEEP) application in patients with severe airway obstruction during controlled mechanical ventilation. The controversial occurrence of a paradoxic lung deflation promoted by PEEP was scrutinized.Design-External-PEEP was applied stepwise (2 cm H 2 O, 5-min steps) from zero-PEEP to 150% of intrinsic-PEEP in patients already submitted to ventilatory settings minimizing overinflation. Two commonly used frequencies during permissive hypercapnia (6 and 9/min), combined with two different tidal volumes (V T : 6 and 9 mL/kg), were tested. Setting-A hospital intensive care unit.Patients-Eight patients were enrolled after confirmation of an obstructive lung disease (inspiratory resistance, >20 cm H 2 O/L per sec) and the presence of intrinsic-PEEP (≥5 cm H 2 O) despite the use of very low minute ventilation.Interventions-All patients were continuously monitored for intra-arterial blood gas values, cardiac output, lung mechanics, and lung volume with plethysmography. Measurements and MainResults-Three different responses to external-PEEP were observed, which were independent of ventilatory settings. In the biphasic response, isovolume-expiratory flows and lung volumes remained constant during progressive PEEP steps until a threshold, beyond which overinflation ensued. In the classic overinflation response, any increment of external-PEEP caused a decrease in isovolume-expiratory flows, with evident overinflation. In the paradoxic response, a drop in functional residual capacity during external-PEEP application (when compared to zeroexternal-PEEP) was commonly accompanied by decreased plateau pressures and total-PEEP, with increased isovolume-expiratory flows. The paradoxic response was observed in five of the eight patients (three with asthma and two with chronic obstructive pulmonary disease) during at least one ventilator pattern.Conclusions-External-PEEP application may relieve overinflation in selected patients with airway obstruction during controlled mechanical ventilation. No a priori information about disease, mechanics, or ventilatory settings was predictive of the response. An empirical PEEP trial investigating plateau pressure response in these patients appears to be a reasonable strategy with minimal side effects.* See also p. 1652.The authors have no financial interest to disclose. -12). Besides the associated hemodynamic impairment, patients with obstructive pulmonary disease frequently experience dyssynchrony during assisted ventilation and difficulty triggering mechanical breaths (2)(3)(4)6,9,10,13,14). This difficulty is caused by the large difference between alveolar and upstream pressures at end-expiration (intrinsic positive end-expiratory pressure, or intrinsic-PEEP), imposing an increased load on inspiratory muscles. NIH Public AccessUnder such conditions, external-PEEP application minimizes pressure differences across obstructed airways, reducing the effort to trigger the ventilator (2-4,9,10). ...

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Section: Discussionmentioning

confidence: 96%

Paradoxical responses to positive end-expiratory pressure in patients with airway obstruction during controlled ventilation*

Caramez

Borges

Tucci

et al. 2005

Critical Care Medicine

116

View full text Add to dashboard Cite

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“…10 Figure 4 shows the isovolume pressure-flow (IVPF) curves for cases 8 and 10 at a lung volume 0.3 l above the lung volume reached at the end of control expiration. These curves were obtained by reproducing a technique proposed by Lourens et al, 24,25 which places an adjustable resistor in the expiratory line of the ventilatory circuit. Briefly, a set of increasing levels of resistance were added to the outlet of the ventilator expiratory channel to obtain a corresponding set of test expirations with different driving pressures (alveolar minus tracheal pressure).…”

Section: Resultsmentioning

confidence: 99%

“…These techniques are based on applying a negative expiratory pressure at the patient's mouth or modifying the resistance of the expiratory circuit during a test expiration. 24,39 …”

Section: Introductionmentioning

confidence: 98%

A Simulation Study of Expiratory Flow Limitation in Obstructive Patients during Mechanical Ventilation

2006

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Although normal lungs may be represented satisfactorily by symmetrical architecture, pathological conditions generally require accounting for asymmetrical branching of the bronchial tree, since lung heterogeneity may be significant in respiratory diseases. In the present study, a recently proposed symmetrical dynamic morphometric model of the human lung, based on Weibel's regular dichotomy, was adapted to simulate different physiopathological scenarios of lung heterogeneity. The asymmetrical architecture was mimicked by modeling different conductive airway compartments below the main bronchi, each compartment being characterized by regular branching. The respiratory zone and chest wall were described by a Voigt body and a constant elastance, respectively. Simulation results allowed us to investigate the influence of the main mechanisms involved in expiratory flow limitation and dynamic hyperinflation in mechanically ventilated COPD patients. In brief, they showed that convective gas acceleration plays a key role in reproducing a negative relationship between driving pressure and expiratory flow. Moreover, reduced lung elastance due to emphysema resulted in a remarkable increase in dynamic hyperinflation, although it did not significantly modify expiratory flow limitation. Finally, the presence of a normal lung compartment masked pathological behaviors, preventing standard techniques from revealing expiratory flow limitation in affected compartments.

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“…4 This finding probably spurred a long line of investigations into the work of breathing (WOB) with CPAP systems, demand flow systems, and modern ventilators. [5][6][7][8][9][10] Both groups described improvements in patient comfort, manifest by reductions in dyspnea and respiratory rate. Neither, however, attributed the comfort to patient-device interaction.…”

Section: Patient-ventilator Interaction During Continuous Positive-prmentioning

confidence: 98%

Patient-Ventilator Interaction: The Last 40 Years

Branson

2011

Respir Care

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SummaryPatient-ventilator synchrony is a complex issue affected by ventilator performance, patient characteristics, and the patient-ventilator interface. The history of patient-ventilator interaction includes avoidance of pharmacalogic paralysis, the development of spontaneous breathing systems, microprocessor technology to maximize interaction, and closed-loop control. While most clinicians agree that patientventilator synchrony is desirable, there remain no cause-and-effect data that asynchrony is associated with poor outcome.

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Detection of flow limitation in mechanically ventilated patients

Cited by 24 publications

References 23 publications

Paradoxical responses to positive end-expiratory pressure in patients with airway obstruction during controlled ventilation*

Paradoxical responses to positive end-expiratory pressure in patients with airway obstruction during controlled ventilation*

A Simulation Study of Expiratory Flow Limitation in Obstructive Patients during Mechanical Ventilation

Patient-Ventilator Interaction: The Last 40 Years

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