Detection of expiratory flow limitation by manual compression of the abdominal wall

Acute effects of manual breathing assist technique on lung volume and dyspnea in individuals with severe chronic obstructive pulmonary disease: A quasi-experimental study

BACKGROUND

Manual breathing assist technique (MBAT) is a common physical therapy technique used to facilitate airway clearance and improve ventilation and oxygenation. The effects during and immediately after intervention in individuals with chronic obstructive pulmonary disease (COPD) are unknown. This study aimed to investigate the acute effects and potential mechanisms of MBAT on lung volume, dyspnea, and oxygenation in individuals with COPD.

METHODS

This non-randomized quasi-experimental pre-test/post-test study included participants from pulmonary rehabilitation programs at Tagami Hospital (COPD group) and a community exercise program (Healthy group). During a single session, MBAT was applied during the expiration of every breath for 10 minutes. Dyspnea and lung volumes (tidal volume; VT, inspiratory capacity; IC, inspiratory reserved capacity; IRV, expiratory reserve capacity; ERV) were collected at baseline and after MBAT. Pulse oximetry (SpO2), skeletal muscle oxygenation (SmO2), and oxy- and deoxy-hemoglobin (O2Hb and HHb) using near-infrared spectroscopy (NIRS) were collected at baseline, during, and after MBAT. Between-group comparisons were conducted using the Mann-Whitney U-test and chi-square analyses. Within-group changes before and after MBAT were analyzed using the Wilcoxon signed-rank test. The Kruskal-Wallis test was used to detect differences in NIRS variables in each phase and over time.

RESULTS

Thirty participants with COPD, matched for age and sex, were included, with 15 individuals per group. The difference scores of VT, IRV, and IC were significantly higher in the Healthy group than in the COPD group, but improvements in dyspnea and SpO2 were significantly higher in the COPD group. Compared to baseline, ERV decreased significantly in both groups, with dyspnea and SpO2 improving significantly only in the COPD group. Inspiratory accessory muscle ΔO2Hb and ΔHHb were significantly higher and lower (respectively) during MBAT in the COPD group compared to the Healthy group. Additionally, only the COPD group had increased SmO2 during and after MBAT compared to baseline.

CONCLUSIONS

MBAT in patients with COPD had acute physiological effects in reducing dyspnea by facilitating expiration and decreasing the recruitment of accessory respiratory muscles. MBAT may help individuals with COPD reduce dyspnea before exercise therapy in a pulmonary rehabilitation program.

Respiratory Mechanics

Today's management of the ventilated patient still relies on the measurement of old parameters such as airway pressures and flow. Graphical presentations reveal the intricacies of patient-ventilator interactions in times of supporting the patient on the ventilator instead of fully ventilating the heavily sedated patient. This opens a new pathway for several bedside technologies based on basic physiologic knowledge; however, it may increase the complexity of measurements. The spread of the COVID-19 infection has confronted the anesthesiologist and intensivist with one of the most severe pulmonary pathologies of the last decades. Optimizing the patient at the bedside is an old and newly required skill for all physicians in the intensive care unit, supported by mobile technologies such as lung ultrasound and electrical impedance tomography. This review summarizes old knowledge and presents a brief insight into extended monitoring options.

Improving lung compliance by external compression of the chest wall

As exemplified by prone positioning, regional variations of lung and chest wall properties provide possibilities for modifying transpulmonary pressures and suggest that clinical interventions related to the judicious application of external pressure may yield benefit. Recent observations made in late-phase patients with severe ARDS caused by COVID-19 (C-ARDS) have revealed unexpected mechanical responses to local chest wall compressions over the sternum and abdomen in the supine position that challenge the clinician's assumptions and conventional bedside approaches to lung protection. These findings appear to open avenues for mechanism-defining research investigation with possible therapeutic implications for all forms and stages of ARDS.

Diagnostic Insights from Plethysmographic Alveolar Pressure Assessed during Spontaneous Breathing in COPD Patients

Since its introduction in the clinical practice, body plethysmography has assisted pneumologists in the diagnosis of respiratory diseases and patients’ follow-up, by providing easy assessment of absolute lung volumes and airway resistance. In the last decade, emerging evidence suggested that estimation of alveolar pressure by electronically-compensated plethysmographs may contain information concerning the mechanics of the respiratory system which goes beyond those provided by the simple value of airway resistance or conductance. Indeed, the systematic study of expiratory alveolar pressure-flow loops produced during spontaneous breathing at rest has shown that the marked expansion of expiratory loops in chronic obstructive pulmonary disease patients mainly reflects the presence of tidal expiratory flow-limitation. The presence of this phenomenon can be accurately predicted on the basis of loop-derived parameters. Finally, we present results suggesting that plethysmographic alveolar pressure may be used to estimate non-invasively intrinsic positive end-expiratory pressure (PEEPi) in spontaneously breathing patients, a task which previously could be only accomplished by introducing a balloon-tipped catheter in the esophagus.

Assessment and treatment of airflow obstruction in patients with chronic obstructive pulmonary disorder: a guide for the clinician

Introduction: Chronic obstructive pulmonary disorder (COPD) is a common cause of disability, morbidity and mortality worldwide. Early diagnosis and adequate treatment maintained over time are crucial to reducing these harmful consequences.Areas covered Persistent, not reversible and naturally progressive airflow obstruction is the functional hallmark of COPD. Therefore, in the presence of individual and environmental risk factors, with or without reported suggestive symptoms, simple spirometry must be performed enough quickly to objectify an obstructive ventilatory defect and assist physicians in making a diagnosis of COPD. Then, to cope with the heterogeneity of COPD patients, more specific functional tests and imaging techniques should be implemented to better define the underlying prevalent disease and its severity. That is necessary to decide whether to introduce ICS and establish the initial level of the treatment with just one or two bronchodilators, to control and freeze, when possible, the underlying pathological process.Expert opinion: The objective assessment of airflow obstruction is mandatory to make a diagnosis of COPD, but the prevalent disease sustaining the disorder should also be investigated to select a targeted therapy, because main determinants of airflow obstruction can be different in COPD patients and may differently respond to treatment.

Non-invasive assessment of respiratory muscle activity during pressure support ventilation: accuracy of end-inspiration occlusion and least square fitting methods

Pressure support ventilation (PSV) should be titrated considering the pressure developed by the respiratory muscles (P_musc) to prevent under- and over-assistance. The esophageal pressure (P_es) is the clinical gold standard for P_musc assessment, but its use is limited by alleged invasiveness and complexity. The least square fitting method and the end-inspiratory occlusion method have been proposed as non-invasive alternatives for P_musc assessment. The aims of this study were: (1) to compare the accuracy of P_musc estimation using the end-inspiration occlusion (P_musc,index) and the least square fitting (P_musc,lsf) against the reference method based on P_es; (2) to test the accuracy of P_musc,lsf and of P_musc,index to detect overassistance, defined as P_musc ≤ 1 cmH₂O. We studied 18 patients at three different PSV levels. At each PSV level, P_musc, P_musc,lsf, P_musc,index were calculated on the same breaths. Differences among P_musc, P_musc,lsf, P_musc,index were analyzed with linear mixed effects models. Bias and agreement were assessed by Bland-Altman analysis for repeated measures. The ability of P_musc,lsf and P_musc,index to detect overassistance was assessed by the area under the receiver operating characteristics curve. Positive and negative predictive values were calculated using cutoff values that maximized the sum of sensitivity and specificity. At each PSV level, P_musc,lsf was not different from P_musc (p = 0.96), whereas P_musc,index was significantly lower than P_musc. The bias between P_musc and P_musc,lsf was zero, whereas P_musc,index systematically underestimated P_musc of 6 cmH₂O. The limits of agreement between P_musc and P_musc,lsf and between P_musc and P_musc,index were ± 12 cmH₂O across bias. Both P_musc,lsf ≤ 4 cmH₂O and P_musc,index ≤ 1 cmH₂O had excellent negative predictive value [0.98 (95% CI 0.94-1) and 0.96 (95% CI 0.91-0.99), respectively)] to identify over-assistance. The inspiratory effort during PSV could not be accurately estimated by the least square fitting or end-inspiratory occlusion method because the limits of agreement were far above the signal size. These non-invasive approaches, however, could be used to screen patients at risk for absent or minimal respiratory muscles activation to prevent the ventilator-induced diaphragmatic dysfunction.

Expiratory flow-limitation in mechanically ventilated patients: A risk for ventilator-induced lung injury?

Expiratory flow limitation (EFL), that is the inability of expiratory flow to increase in spite of an increase of the driving pressure, is a common and unrecognized occurrence during mechanical ventilation in a variety of intensive care unit conditions. Recent evidence suggests that the presence of EFL is associated with an increase in mortality, at least in acute respiratory distress syndrome (ARDS) patients, and in pulmonary complications in patients undergoing surgery. EFL is a major cause of intrinsic positive end-expiratory pressure (PEEPi), which in ARDS patients is heterogeneously distributed, with a consequent increase of ventilation/perfusion mismatch and reduction of arterial oxygenation. Airway collapse is frequently concomitant to the presence of EFL. When airways close and reopen during tidal ventilation, abnormally high stresses are generated that can damage the bronchiolar epithelium and uncouple small airways from the alveolar septa, possibly generating the small airways abnormalities detected at autopsy in ARDS. Finally, the high stresses and airway distortion generated downstream the choke points may contribute to parenchymal injury, but this possibility is still unproven. PEEP application can abolish EFL, decrease PEEPi heterogeneity, and limit recruitment/derecruitment. Whether increasing PEEP up to EFL disappearance is a useful criterion for PEEP titration can only be determined by future studies.

Expiratory Flow Limitation During Mechanical Ventilation

Expiratory flow limitation (EFL) is present when the flow cannot rise despite an increase in the expiratory driving pressure. The mechanisms of EFL are debated but are believed to be related to the collapsibility of small airways. In patients who are mechanically ventilated, EFL can exist during tidal ventilation, representing an extreme situation in which lung volume cannot decrease, regardless of the expiratory driving forces. It is a key factor for the generation of auto- or intrinsic positive end-expiratory pressure (PEEP) and requires specific management such as positioning and adjustment of external PEEP. EFL can be responsible for causing dyspnea and patient-ventilator dyssynchrony, and it is influenced by the fluid status of the patient. EFL frequently affects patients with COPD, obesity, and heart failure, as well as patients with ARDS, especially at low PEEP. EFL is, however, most often unrecognized in the clinical setting despite being associated with complications of mechanical ventilation and poor outcomes such as postoperative pulmonary complications, extubation failure, and possibly airway injury in ARDS. Therefore, prompt recognition might help the management of patients being mechanically ventilated who have EFL and could potentially influence outcome. EFL can be suspected by using different means, and this review summarizes the methods to specifically detect EFL during mechanical ventilation.

Effects of chest wall compression on expiratory flow rates in patients with chronic obstructive pulmonary disease

BACKGROUND

Manual chest wall compression (CWC) during expiration is a technique for removing airway secretions in patients with respiratory disorders. However, there have been no reports about the physiological effects of CWC in patients with chronic obstructive pulmonary disease (COPD).

OBJECTIVE

To compare the effects of CWC on expiratory flow rates in patients with COPD and asymptomatic controls.

METHOD

Fourteen subjects were recruited from among patients with COPD who were receiving pulmonary rehabilitation at the University Hospital (COPD group). Fourteen age-matched healthy subjects were also consecutively recruited from the local community (Healthy control group). Airflow and lung volume changes were measured continuously with the subjects lying in supine position during 1 minute of quiet breathing (QB) and during 1 minute of CWC by a physical therapist.

RESULTS

During CWC, both the COPD group and the healthy control group showed significantly higher peak expiratory flow rates (PEFRs) than during QB (mean difference for COPD group 0.14 L/sec, 95% confidence interval (CI) 0.04 to 0.24, p<0.01, mean difference for healthy control group 0.39 L/sec, 95% CI 0.25 to 0.57, p<0.01). In the between-group comparisons, PEFR was significantly higher in the healthy control group than in the COPD group (-0.25 L/sec, 95% CI -0.43 to -0.07, p<0.01). However, the expiratory flow rates at the lung volume at the PEFR during QB and at 50% and 25% of tidal volume during QB increased in the healthy control group (mean difference for healthy control group 0.31 L/sec, 95% CI 0.15 to 0.47, p<0.01: 0.31 L/sec, 95% CI 0.15 to 0.47, p<0.01: 0.27 L/sec, 95% CI 0.13 to 0.41, p<0.01, respectively) but not in the COPD group (0.05 L/sec, 95% CI -0.01 to 0.12: -0.01 L/sec, 95% CI -0.11 to 0.08: 0.02 L/sec, 95% CI -0.05 to 0.90) with the application of CWC.

CONCLUSION

The effects of chest wall compression on expiratory flow rates was different between COPD patients and asymptomatic controls.

Airway dynamics in COPD patients by within-breath impedance tracking: effects of continuous positive airway pressure

Tracking of the within-breath changes of respiratory mechanics using the forced oscillation technique may provide outcomes that characterise the dynamic behaviour of the airways during normal breathing.

We measured respiratory resistance (Rrs) and reactance (Xrs) at 8 Hz in 55 chronic obstructive pulmonary disease (COPD) patients and 20 healthy controls, and evaluated Rrs and Xrs as functions of gas flow (V′) and volume (V) during normal breathing cycles. In 12 COPD patients, additional measurements were made at continuous positive airway pressure (CPAP) levels of 4, 8, 14 and 20 hPa.

The Rrs and Xrsversus V′ and V relationships displayed a variety of loop patterns, allowing characterisation of physiological and pathological processes. The main outcomes emerging from the within-breath analysis were the Xrsversus V loop area (AXV) quantifying expiratory flow limitation, and the tidal change in Xrs during inspiration (ΔXI) reflecting alteration in lung inhomogeneity in COPD. With increasing CPAP, AXV and ΔXI approached the normal ranges, although with a large variability between individuals, whereas mean Rrs remained unchanged.

Within-breath tracking of Rrs and Xrs allows an improved assessment of expiratory flow limitation and functional inhomogeneity in COPD; thereby it may help identify the physiological phenotypes of COPD and determine the optimal level of respiratory support.

Effect of external PEEP in patients under controlled mechanical ventilation with an auto-PEEP of 5 cmH2O or higher

Background

In some patients with auto-positive end-expiratory pressure (auto-PEEP), application of PEEP lower than auto-PEEP maintains a constant total PEEP, therefore reducing the inspiratory threshold load without detrimental cardiovascular or respiratory effects. We refer to these patients as “complete PEEP-absorbers.” Conversely, adverse effects of PEEP application could occur in patients with auto-PEEP when the total PEEP rises as a consequence. From a pathophysiological perspective, all subjects with flow limitation are expected to be “complete PEEP-absorbers,” whereas PEEP should increase total PEEP in all other patients. This study aimed to empirically assess the extent to which flow limitation alone explains a “complete PEEP-absorber” behavior (i.e., absence of further hyperinflation with PEEP), and to identify other factors associated with it.

Methods

One hundred patients with auto-PEEP of at least 5 cmH₂O at zero end-expiratory pressure (ZEEP) during controlled mechanical ventilation were enrolled. Total PEEP (i.e., end-expiratory plateau pressure) was measured both at ZEEP and after applied PEEP equal to 80 % of auto-PEEP measured at ZEEP. All measurements were repeated three times, and the average value was used for analysis.

Results

Forty-seven percent of the patients suffered from chronic pulmonary disease and 52 % from acute pulmonary disease; 61 % showed flow limitation at ZEEP, assessed by manual compression of the abdomen. The mean total PEEP was 7 ± 2 cmH₂O at ZEEP and 9 ± 2 cmH₂O after the application of PEEP (p < 0.001). Thirty-three percent of the patients were “complete PEEP-absorbers.” Multiple logistic regression was used to predict the behavior of “complete PEEP-absorber.” The best model included a respiratory rate lower than 20 breaths/min and the presence of flow limitation. The predictive ability of the model was excellent, with an overoptimism-corrected area under the receiver operating characteristics curve of 0.89 (95 % CI 0.80–0.97).

Conclusions

Expiratory flow limitation was associated with both high and complete “PEEP-absorber” behavior, but setting a relatively high respiratory rate on the ventilator can prevent from observing complete “PEEP-absorption.” Therefore, the effect of PEEP application in patients with auto-PEEP can be accurately predicted at the bedside by measuring the respiratory rate and observing the flow-volume loop during manual compression of the abdomen.

Chronic obstructive pulmonary disease

COPD is characterized by airflow limitation that is not fully reversible. The morphological basis for airflow obstruction results from a varying combination of obstructive changes in peripheral conducting airways and destructive changes in respiratory bronchioles, alveolar ducts, and alveoli. A reduction of vascularity within the alveolar septa has been reported in emphysema. Typical physiological changes reflect these structural abnormalities. Spirometry documents airflow obstruction when the FEV1/FVC ratio is reduced below the lower limit of normality, although in early disease stages FEV1 and airway conductance are not affected. Current guidelines recommend testing for bronchoreversibility at least once and the postbronchodilator FEV1/FVC be used for COPD diagnosis; the nature of bronchodilator response remains controversial, however. One major functional consequence of altered lung mechanics is lung hyperinflation. FRC may increase as a result of static or dynamic mechanisms, or both. The link between dynamic lung hyperinflation and expiratory flow limitation during tidal breathing has been demonstrated. Hyperinflation may increase the load on inspiratory muscles, with resulting length adaptation of diaphragm. Reduction of exercise tolerance is frequently noted, with compelling evidence that breathlessness and altered lung mechanics play a major role. Lung function measurements have been traditionally used as prognostic indices and to monitor disease progression; FEV1 has been most widely used. An increase in FVC is also considered as proof of bronchodilatation. Decades of work has provided insight into the histological, functional, and biological features of COPD. This has provided a clearer understanding of important pathobiological processes and has provided additional therapeutic options.

Expiratory flow limitation

Expiratory flow limitation occurs when flow ceases to increase with increasing expiratory effort. The equal pressure point concept has been largely successful in providing intuitive understanding of the phenomenon, wherein maximal flows are determined by lung recoil and resistance upstream of the site where bronchial transmural pressure is zero (the EPP). Subsequent work on the fluid dynamical foundations led to the wave-speed theory of flow limitation, where flow is limited at a site when the local gas velocity is equal to speed of propagation of pressure waves. Each is a local theory; full predictions require knowledge of both density-dependent Bernoulli pressure drops and viscosity-dependent pressure losses due to dissipation. The former is dominant at mid to high lung volumes, whereas the latter is more important at low lung volumes as the flow-limiting site moves peripherally. The observation of relative effort independence of the maximal flow versus volume curves is important clinically insofar as such maneuvers, when carefully performed, offer a unique window into the mechanics of the lung itself, with little confounding effects. In particular, the important contributions of lung recoil and airways resistance can often be assessed, with implications and applications to diagnosis and management of pulmonary disease.

Effects of sitting position and applied positive end-expiratory pressure on respiratory mechanics of critically ill obese patients receiving mechanical ventilation*

OBJECTIVE

To evaluate the extent to which sitting position and applied positive end-expiratory pressure improve respiratory mechanics of severely obese patients under mechanical ventilation.

DESIGN

Prospective cohort study.

SETTINGS

A 15-bed ICU of a tertiary hospital.

PARTICIPANTS

Fifteen consecutive critically ill patients with a body mass index (the weight in kilograms divided by the square of the height in meters) above 35 were compared to 15 controls with body mass index less than 30.

INTERVENTIONS

Respiratory mechanics was first assessed in the supine position, at zero end-expiratory pressure, and then at positive end-expiratory pressure set at the level of auto-positive endexpiratory pressure. Second, all measures were repeated in the sitting position.

MEASUREMENTS AND MAIN RESULTS

Assessment of respiratory mechanics included plateau pressure, auto-positive end-expiratory pressure, and flow-limited volume during manual compression of the abdomen, expressed as percentage of tidal volume to evaluate expiratory flow limitation. In supine position at zero end-expiratory pressure, all critically ill obese patients demonstrated expiratory flow limitation (flow-limited volume, 59.4% [51.3-81.4%] vs 0% [0-0%] in controls; p < 0.0001) and greater auto-positive end-expiratory pressure (10 [5-12.5] vs 0.7 [0.4-1.25] cm H2O in controls; p < 0.0001). Applied positive end-expiratory pressure reverses expiratory flow limitation (flow-limited volume, 0% [0-21%] vs 59.4% [51-81.4%] at zero end-expiratory pressure; p < 0.001) in almost all the obese patients, without increasing plateau pressure (24 [19-25] vs 22 [18-24] cm H2O at zero end-expiratory pressure; p = 0.94). Sitting position not only reverses partially or completely expiratory flow limitation at zero end-expiratory pressure (flow-limited volume, 0% [0-58%] vs 59.4% [51-81.4%] in supine obese patients; p < 0.001) but also results in a significant drop in auto-positive end-expiratory pressure (1.2 [0.6-4] vs 10 [5-12.5] cm H2O in supine obese patients; p < 0.001) and plateau pressure (15.6 [14-17] vs 22 [18-24] cm H2O in supine obese patients; p < 0.001).

CONCLUSIONS

In critically ill obese patients under mechanical ventilation, sitting position constantly and significantly relieved expiratory flow limitation and auto-positive end-expiratory pressure resulting in a dramatic drop in alveolar pressures. Combining sitting position and applied positive end-expiratory pressure provides the best strategy.

Expiratory flow limitation definition, mechanisms, methods, and significance

When expiratory flow is maximal during tidal breathing and cannot be increased unless operative lung volumes move towards total lung capacity, tidal expiratory flow limitation (EFL) is said to occur. EFL represents a severe mechanical constraint caused by different mechanisms and observed in different conditions, but it is more relevant in terms of prevalence and negative consequences in obstructive lung diseases and particularly in chronic obstructive pulmonary disease (COPD). Although in COPD patients EFL more commonly develops during exercise, in more advanced disorder it can be present at rest, before in supine position, and then in seated-sitting position. In any circumstances EFL predisposes to pulmonary dynamic hyperinflation and its unfavorable effects such as increased elastic work of breathing, inspiratory muscles dysfunction, and progressive neuroventilatory dissociation, leading to reduced exercise tolerance, marked breathlessness during effort, and severe chronic dyspnea.

Methods for Assessing Expiratory Flow Limitation during Tidal Breathing in COPD Patients

Patients with severe COPD often exhale along the same flow-volume curve during quite breathing as during forced expiratory vital capacity manoeuvre, and this has been taken as indicating expiratory flow limitation at rest (EFL_T). Therefore, EFL_T, namely, attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. EFL_T leads to small airway injury and promotes dynamic pulmonary hyperinflation with concurrent dyspnoea and exercise limitation. In fact, EFL_T occurs commonly in COPD patients (mainly in GOLD III and IV stage) in whom the latter symptoms are common. The existing up-to-date physiological methods for assessing expiratory flow limitation (EFL_T) are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure (NEP) has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, non invasive, most practical, and accurate new technique.

Obesity, expiratory flow limitation and asthma symptoms

Obesity is associated with poor asthma control, but the reason for this is unclear. Reduction in operating lung volume, as occurs in obesity, and bronchoconstriction, as occurs in asthma, can increase expiratory flow limitation during tidal breathing (EFLt), which may in turn increase respiratory symptoms. The aim of this study was to determine the effect of obesity on EFLt at baseline and after bronchoconstriction in non-asthmatic and asthmatic subjects, and to determine the association between EFLt, and respiratory symptoms. Data from previously published studies in non-asthmatic and asthmatic subjects were reanalyzed using an index of EFLt derived from respiratory system reactance measured by the forced oscillation technique. The analysis showed that during bronchoconstriction both non-asthmatic and asthmatic obese individuals were more likely to develop EFLt than non-obese subjects, despite similar changes in FEV1. Furthermore the index of EFLt was a significant determinant of the severity of breathlessness during challenge in non-asthmatic subjects, and of asthma symptom control in asthmatic subjects following anti-inflammatory treatment. These studies suggest that the combination of bronchoconstriction and low resting lung volume increase the risk of EFLt, and that this altered response to bronchoconstriction may increase the severity of symptoms and lead to worse asthma control.

Hoover's sign is a predictor of airflow obstruction severity and is not related to hyperinflation in chronic obstructive pulmonary disease

BACKGROUND

Several phenotypes are described in COPD.

OBJECTIVES

To assess if COPD patients with Hoover's sign (HS) belong to a particular phenotype.

METHODS

All consecutive COPD patients with varying degree of airflow obstruction that came for lung function testing in one university hospital were prospectively assessed, using clinical and magnetometer detection of HS, body mass index (BMI), St. George's Respiratory Questionnaire for health-related quality of life, six-minute-walk test (6MWT) with inspiratory capacity (IC) measurements and expiratory flow limitation (EFL) detection. Previous exacerbations were also reported.

RESULTS

82 patients were studied. Magnetometers confirmed HS in 56 of them, of which 79% (44/56) were detected by clinical assessment. HS (+) patients were older (64 ± 10 vs 59 ± 10 years, p=0.03), had a higher BMI (26 ± 5 vs 23 ± 4, p=0.04), a lower FEV1 (53% ± 18% vs 63% ± 18% pred, p=0.02) and a higher IC decrease at the end of 6MWT, (-19 ± 2 vs -7 ± 4% pred, p=0.003). A larger proportion of HS (+) patients also reported severe exacerbations during the past 2 years (39% vs 12% p=0.01). There was no statistical evidence that HS was related to hyperinflation and/or EFL.

CONCLUSION

The very simple clinical HS allows identifying a particular population of COPD patients of older age and higher BMI with a more severe airflow obstruction, increased dynamic hyperinflation during exercise and higher exacerbation frequency. These characteristics were not linked to hyperinflation or EFL.

Dynamic hyperinflation and auto-positive end-expiratory pressure: lessons learned over 30 years

Auto-positive end-expiratory pressure (auto-PEEP; AP) and dynamic hyperinflation (DH) may affect hemodynamics, predispose to barotrauma, increase work of breathing, cause dyspnea, disrupt patient-ventilator synchrony, confuse monitoring of hemodynamics and respiratory system mechanics, and interfere with the effectiveness of pressure-regulated ventilation. Although basic knowledge regarding the clinical physiology and management of AP during mechanical ventilation has evolved impressively over the 30 years since DH and AP were first brought to clinical attention, novel and clinically relevant characteristics of this complex phenomenon continue to be described. This discussion reviews some of the more important aspects of AP that bear on the care of the ventilated patient with critical illness.

Does negative expiratory pressure (NEP) during spontaneous breathing predict respiratory impairment in elderly?

OBJECTIVE

The purpose of this study is to assess whether expiratory flow limitation (FL), as measured by applying a negative pressure at the mouth during tidal expiration, can evaluate the respiratory impairment in elderly patients.

METHODS

The study was carried out in 67 consecutive elderly inpatients (24 men and 43 women). Negative expiratory pressure (NEP) of -5 (NEP 5) and -10 (NEP 10) cm H2O were applied during spontaneous tidal expiration. According to the results of the NEP technique, the patients were stratified in two categories: not flow limited and flow limited. We realized then classic forced expiratory manoeuvres (FEV1, FVC) and clinical evaluation of dyspnea (NYHA). According to the values of the lung function data, elderly patients were then divided in 3 groups (normal, obstructive, restrictive).

RESULTS

The sensitivity, the specificity, the positive and negative predictive values for the diagnosis of obstructive syndrome by the presence of flow limitation during NEP 5 were 53, 74, 45, 79% respectively and 58, 83, 58, 83% respectively during NEP 10. These findings show that the correlation between FL obtained by the NEP technique during spontaneous breathing and spirometry is not very good despite the fact that both were well correlated with dyspnea score.

CONCLUSIONS

In clinical practice, faced with an elderly dyspneic patient unable to perform maximal expiratory manoeuvres, the evaluation of flow limitation by NEP technique seems nor to be reliable to predict an obstructive functional impairment nor to be able to explain the origin of his dyspnea.

La compression abdominale manuelle dans la détection de la limitation du débit expiratoire

INTRODUCTION

Expiratory flow limitation (EFL) is a characteristic feature of chronic obstructive pulmonary disease (COPD) and leads to dynamic hyperinflation (DH) which is a major source of dyspnoea, particularly during exercise.

STATE OF THE ART

A new technique for the detection of EFL, based on manual compression of the abdomen (MCA), was assessed both in normal subjects and patients with COPD. MCA was always associated with a moderate increase in pleural pressure and allowed the detection of EFL in a reproducible manner, in both the seated and supine postures. The technique was well tolerated. It was also a reliable method for the detection of EFL during exercise since EFL detection was effectively associated with the development of DH. Finally, MCA was also compared to NEP in patients with obstructive sleep apnoea syndrome (OSAS) and in these patients, MCA invariably increased expiratory flow whereas the NEP method produced flow limitation in some cases because of upper airway collapse.

PERSPECTIVES

EFL detection with MCA may be clinically useful since EFL is a determinant of dyspnoea, affects ventilatory response to exercise as well as maximum exercise capacity.

CONCLUSIONS

MCA is a reliable technique for the detection of EFL in different positions, during resting breathing or exercise, requiring neither special equipment nor patient cooperation.