Effects of PEEP on inspiratory resistance in mechanically ventilated COPD patients

Guérin, Claude; Fournier, G.; Milic–Emili, J.

doi:10.1183/09031936.01.00072001

Cited by 20 publications

(15 citation statements)

References 23 publications

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“…The differences in parameter values between our study groups can also be attributed to different levels of hyperinflation, which may have been more serious in the AECOPD patients; however, in our study protocol, the premeasurement PEEP was standardized and the actual lung volumes were not known. We note that, although there is agreement between the results of Guerin et al (13) and those of the present study in regard to the decrease in R N , Guerin et al observed an unchanged viscoelastic behavior of the respiratory system with increasing PEEP. This is in sharp contrast with the decline in G with increasing PEEP in the present study, indicating that the two modeling approaches do not account for the combined effects of stress relaxation and ventilation inhomogeneity in a similar manner.…”

Section: Discussionsupporting

confidence: 91%

Low-frequency assessment of airway and tissue mechanics in ventilated COPD patients

Lorx

Szabó

Hercsuth

et al. 2009

Journal of Applied Physiology

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Lorx A, Szabó B, Hercsuth M, Pénzes I, Hantos Z. Lowfrequency assessment of airway and tissue mechanics in ventilated COPD patients. J Appl Physiol 107: 1884 -1892, 2009. First published October 15, 2009 doi:10.1152/japplphysiol.00151.2009.-Low-frequency forced oscillations have increasingly been employed to characterize airway and tissue mechanics separately in the normal respiratory system and animal models of lung disease; however, few data are available on the use of this method in chronic obstructive pulmonary disease (COPD). We studied 30 intubated and mechanically ventilated patients (COPD, n ϭ 9; acute exacerbation of COPD, n ϭ 21) during short apneic intervals at different levels of positive endexpiratory pressure (PEEP), with small-amplitude forced oscillations between 0.4 and 4.8 Hz. In 16 patients, measurements were made before and after inhalation of fenoterol hydrobromide plus ipratropium bromide (Berodual). Newtonian resistance and coefficients of tissue resistance (G) and elastance (H) were estimated from the respiratory system impedance (Zrs) data by model fitting. Apart from some extremely high Zrs data obtained primarily at relatively low PEEP levels, the model yielded a reasonable partitioning of the airway and tissue parameters, and the inclusion of further parameters did not improve the model performance. With increasing PEEP, Newtonian resistance and the ratio G/H decreased, reflecting the volume dependence of the airway caliber and the improved homogeneity of the lungs, respectively. Bronchodilation after the administration of Berodual was also associated with simultaneous decreases in G and H, indicating recruitment of lung units. In conclusion, the measurement of lowfrequency Zrs can be accomplished in ventilated COPD patients during short apneic periods and offers valuable information on the mechanical status of the airways and tissues. forced oscillation; respiratory resistance; respiratory elastance; mechanical ventilation; bronchodilation THE FORCED OSCILLATION TECHNIQUE (FOT) has increasingly been used as a lung function test method in both health and disease (26). A variant of the FOT, involving low oscillation frequencies comparable with the breathing rate (LFOT) and a modelbased evaluation of respiratory system impedance (Zrs), has been shown to provide a noninvasive method for partitioning of the total respiratory or pulmonary mechanics into airway and respiratory tissue properties. The LFOT has been employed extensively in infants during Hering-Breuer reflex apnea (e.g., Refs. 14, 32) and in perioperative studies on adults (2,3,8,25) and children with normal lung function (28). In these studies, the interpretation of the measured Zrs data via a mechanical model consisting of a simple airway compartment connected to a constant-phase tissue impedance (16) resulted in physiologically meaningful parameters. Although this approach has been implemented in numerous investigations on different animals both under normal conditions and in disease models, few LFOT measurements have been...

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Section: Discussionsupporting

confidence: 91%

Low-frequency assessment of airway and tissue mechanics in ventilated COPD patients

Lorx

Szabó

Hercsuth

et al. 2009

Journal of Applied Physiology

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“…This assumption may not be entirely valid in some cases [33,34]. However, continuous measurements of respiratory resistance are not typically available and the effect of this resistive term is limited mathematically in its impact.…”

Section: Discussionmentioning

confidence: 99%

Model-based PEEP optimisation in mechanical ventilation

et al. 2011

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BackgroundAcute Respiratory Distress Syndrome (ARDS) patients require mechanical ventilation (MV) for breathing support. Patient-specific PEEP is encouraged for treating different patients but there is no well established method in optimal PEEP selection.MethodsA study of 10 patients diagnosed with ALI/ARDS whom underwent recruitment manoeuvre is carried out. Airway pressure and flow data are used to identify patient-specific constant lung elastance (Elung) and time-variant dynamic lung elastance (Edrs) at each PEEP level (increments of 5cmH2O), for a single compartment linear lung model using integral-based methods. Optimal PEEP is estimated using Elung versus PEEP, Edrs-Pressure curve and Edrs Area at minimum elastance (maximum compliance) and the inflection of the curves (diminishing return). Results are compared to clinically selected PEEP values. The trials and use of the data were approved by the New Zealand South Island Regional Ethics Committee.ResultsMedian absolute percentage fitting error to the data when estimating time-variant Edrs is 0.9% (IQR = 0.5-2.4) and 5.6% [IQR: 1.8-11.3] when estimating constant Elung. Both Elung and Edrs decrease with PEEP to a minimum, before rising, and indicating potential over-inflation. Median Edrs over all patients across all PEEP values was 32.2 cmH2O/l [IQR: 26.1-46.6], reflecting the heterogeneity of ALI/ARDS patients, and their response to PEEP, that complicates standard approaches to PEEP selection. All Edrs-Pressure curves have a clear inflection point before minimum Edrs, making PEEP selection straightforward. Model-based selected PEEP using the proposed metrics were higher than clinically selected values in 7/10 cases.ConclusionContinuous monitoring of the patient-specific Elung and Edrs and minimally invasive PEEP titration provide a unique, patient-specific and physiologically relevant metric to optimize PEEP selection with minimal disruption of MV therapy.

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“…No harmful effects have been reported from positive expiratory breathing (39). Although there have been some contradictory reports (37,39) and there have not yet been meta-analyses of the use of positive end-expiratory pressure for people with cystic fibrosis, chronic obstructive pulmonary disease or neuromuscular disorders, the majority of clinical studies (27,28,35,(40)(41)(42)(43)(44)(45) have described benefits of positive expiratory pressure on mucus clearance and pulmonary function.…”

Section: Effects Of Positive End-expiratory Pressure On Mucus Clearanmentioning

confidence: 99%

High‐Frequency Chest Compression: A Summary of the Literature

Dosman

Jones

2005

Canadian Respiratory Journal

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The purpose of the present literature summary is to describe high-frequency chest compression (HFCC), summarize its history and outline study results on its effect on mucolysis, mucus transport, pulmonary function and quality of life. HFCC is a mechanical method of self-administered chest physiotherapy, which induces rapid air movement in and out of the lungs. This mean oscillated volume is an effective method of mucolysis and mucus clearance. HFCC can increase independence. Some studies have shown that HFCC leads to more mucus clearance and better lung function compared with conventional chest physiotherapy. However, HFCC also decreases end-expiratory lung volume, which can lead to increased airway resistance and a decreased oscillated volume. Adding positive end-expiratory pressure to HFCC has been shown to prevent this decrease in end-expiratory lung volume and to increase the oscillated volume. It is possible that the HFCC-induced decrease in end-expiratory lung volume may result in more mucus clearance in airways that remain open by reducing airway size. Adjunctive methods, such as positive end-expiratory pressure, may not always be needed to make HFCC more effective.

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Effects of PEEP on inspiratory resistance in mechanically ventilated COPD patients

Cited by 20 publications

References 23 publications

Low-frequency assessment of airway and tissue mechanics in ventilated COPD patients

Low-frequency assessment of airway and tissue mechanics in ventilated COPD patients

Model-based PEEP optimisation in mechanical ventilation

High‐Frequency Chest Compression: A Summary of the Literature

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