Expiratory flow limitation in intensive care: prevalence and risk factors

Volta, Carlo Alberto; Corte, Francesca Dalla; Ragazzi, Riccardo; Marangoni, Elisabetta; Fogagnolo, Alberto; Scaramuzzo, Gaetano; Grieco, Domenico Luca; Alvisi, Valentina; Rizzuto, Chiara; Spadaro, Savino

doi:10.1186/s13054-019-2682-4

Cited by 28 publications

(27 citation statements)

References 41 publications

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“…This is a cardinal feature in patients with COPD but also in those with ARDS. [16][17][18] Expiratory flow limitation assessment in patients with ARDS has value because it is frequent, can be used to set PEEP, 19 and may be associated with patient outcome. 20 There are basically 2 methods to assess expiratory flow limitation during mechanical ventilation: the atmospheric method, and a small change in PEEP.…”

Section: Discussionmentioning

confidence: 99%

Bench Assessment of Expiratory Valve Resistance of Current ICU Ventilators in Dynamic Conditions

et al. 2020

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BACKGROUND: We hypothesized that the lack of benefit of setting a low versus a high PEEP in patients with ARDS may be due in part to differences in the dynamic behavior of the expiratory valve in ventilators. We tested this hypothesis by conducting a bench comparison of the dynamic behavior of expiratory valves on ICU ventilators currently in use. METHODS: We attached 7 ICU ventilators (C5, C6, Carescape, PB980, ServoU, V500, and V680) to the ASL 5000 lung model (passive condition with compliance 20 mL/cm H 2 O and resistance 5 cm H 2 O/L/s) and set in volume controlled mode (tidal volume 0.8 L, breathing frequency 10 breaths/min). Flow and pressure were measured just before the exhalation valve. At PEEP of 5, 10, and 15 cm H 2 O, the median instantaneous expiratory resistance, the time to valve opening, and the pressure time products above or below the values of PEEP (expressed in cm H 2 O 3 s) were determined. RESULTS: Median instantaneous expiratory resistance values differed between the ventilators and PEEP settings with a significant interaction: at PEEP 5 cm H 2 O, the median (interquartile range) expiratory resistance values were 3.

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Section: Discussionmentioning

confidence: 99%

Bench Assessment of Expiratory Valve Resistance of Current ICU Ventilators in Dynamic Conditions

et al. 2020

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“…EFL does not simply mean increased respiratory system resistance. It is a specific respiratory disorder with serious impact on respiratory and circulatory functions [1][2][3][4][5][6][7].…”

Section: Discussionmentioning

confidence: 99%

“…Detection of expiratory flow limitation (EFL) is crucial during mechanical ventilation (MV), because of its adverse effects on respiration and cardiovascular function [1][2][3][4][5][6][7]. Dynamic hyperinflation and increase of mean alveolar pressure are the net result of air trapping due to EFL.…”

Section: Introductionmentioning

confidence: 99%

Non-interventional monitoring of expiratory flow limitation during experimental mechanical ventilation

et al. 2020

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BackgroundΕxpiratory flow limitation (EFL) is common among ICU patients under mechanical ventilation (MV) and may have significant clinical consequences. In the present study, we examine the possibility of non-interventional detection of EFL during experimental MV.MethodsEight artificially ventilated New Zealand rabbits were included in the experiments. EFL was induced during MV by application of negative expiratory pressure (−5, −8 and −10 hPa) and detected by the negative expiratory pressure (NEP) technique. Airway pressure (Paw) and flow (Vʹ) were digitally recorded and processed off-line for the evaluation of respiratory mechanics. The method is based on the computation and monitoring of instantaneous respiratory resistance Rrs(t). The resistive pressure (Paw,res(t)) is calculated by subtracting from Paw its elastic component and the end expiratory pressure (EEP), as assessed by linear regression. Then, Rrs(t) is computed as the instant ratio Paw,res(t)/Vʹ(t).ResultsTwo completely different patterns of expiratory Rrs(t) separate the cases with EFL from those without EFL. Small and random fluctuations are noticed when EFL is absent, whereas the onset of EFL is accompanied by an abrupt and continuous rise in Rrs(t), towards the end of expiration. Thus, EFL is not only detected but may also be quantified from the volume still to be expired at the time EFL occurs.ConclusionThe proposed technique is a simple, accurate and non-interventional tool for the EFL monitoring during MV.

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“…Therefore, the relationship of fluid overload, respiratory mechanics, and outcome for ICU patients remains unclear, and further studies are needed to determine whether and why preventing EFL is a target for ICU management. Thank you for giving us the opportunity to reply to the valuable comments raised by Wang et al regarding our article [1].…”

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confidence: 95%

Expiratory flow limitation developed in ICU patients: relationship of fluid overload, respiratory mechanics, and outcome

Wang

2020

Crit Care

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Dear editor, We read with great interest in the report by Volta and colleagues [1] about the presence and determinant of expiratory flow limitation (EFL) developed in patients admitted to an intensive care unit (ICU). They found that the presence of EFL is common among ICU patients requiring mechanical ventilation for acute respiratory failure of different etiologies. And interestingly, the major determinant for developing EFL in patients during the first 3 days of their ICU stay is a positive fluid balance. However, whether there is a relationship among fluid overload, respiratory mechanics, and outcome is controversial, and we would like to add some comments. First, in Volta et al.'s work [1], 37 (31%) patients exhibited EFL upon admission, of whom 76%, 57%, and 43% had heart diseases, COPD or ARDS, and higher BMI, respectively. It is easily explainable that obese patients and those with COPD, heart disease, or ARDS can exhibit EFL at ICU admission [2]. Therefore, it should be more important to focus on patients who might develop EFL during the ICU stay and its mechanism. Second, whether fluid overload is the mechanism of developing EFL during the ICU stay was not fully explained by Volta et al.'s data [1]. A decreased respiratory system compliance and an increased airway resistance should be related to fluid overload-induced pulmonary edema, pleural effusion, or small airway swelling and closure [3]. Of note, in Volta's study,

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Expiratory flow limitation in intensive care: prevalence and risk factors

Cited by 28 publications

References 41 publications

Bench Assessment of Expiratory Valve Resistance of Current ICU Ventilators in Dynamic Conditions

Bench Assessment of Expiratory Valve Resistance of Current ICU Ventilators in Dynamic Conditions

Non-interventional monitoring of expiratory flow limitation during experimental mechanical ventilation

Expiratory flow limitation developed in ICU patients: relationship of fluid overload, respiratory mechanics, and outcome

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