Dynamic hyperinflation is a risk factor for mortality and severe exacerbations in COPD patients

OBJECTIVE

To assess if dynamic hyperinflation is an independent risk factor for mortality and severe exacerbations in COPD patients.

METHODS

A cohort of 141 patients with stable COPD and moderate to very severe airflow limitation, treated according to conventional guidelines, was followed for a median of 9 years. Clinical characteristics were recorded and arterial blood gases, pulmonary function tests, 6-min walk and incremental exercise test with measurement of respiratory pattern and operative lung volumes were performed. Endpoints were all-cause mortality and hospitalization for COPD exacerbation.

RESULTS

58 patients died during the follow-up period (1228 patients x year). The mortality rate was higher in patients with dynamic hyperinflation (n = 106) than in those without it (n = 35) (14.6; 95% CI, 14.5-14.8 vs. 7.2; 95% CI, 7.1-7.4 per 1000 patients-year). After adjusting for sex, age, body mass index, pack-years and treatment with inhaled corticosteroids, dynamic hyperinflation was associated with a higher mortality risk (adjusted hazard ratio [aHR], 2.725; 95% CI, 1.010-8.161), and in a multivariate model, comorbidity, peak oxygen uptake and dynamic hyperinflation were retained as independent predictors of mortality. The time until first severe exacerbation was shorter for patients with dynamic hyperinflation (aHR, 3.961; 95% CI, 1.385-11.328), and dynamic hyperinflation, FEV1 and diffusing capacity were retained as independent risk factors for severe exacerbation. Moreover, patients with dynamic hyperinflation had a higher hospitalization risk than those without it (adjusted incidence rate ratio, 1.574; 95% CI, 1.087-2.581).

CONCLUSION

In stable COPD patients, dynamic hyperinflation is an independent prognostic factor for mortality and severe exacerbations.

Evidence of ventilatory constraints during exercise in hypermobile Ehlers-Danlos syndrome

PURPOSE

Hypermobile Ehlers-Danlos syndrome (hEDS) is a connective tissue disorder with many different symptoms such as pain, fatigue, dysautonomia, or respiratory symptoms. Among the respiratory manifestations described, the most frequent are exertional dyspnea and breathing difficulties. Mechanical ventilatory constraints during exercise could participate in these respiratory manifestations. The objective of this study was to explore the response of pulmonary flow-volume loops to exercise in patients with hEDS and to look for dynamic hyperinflation and expiratory flow limitation during exercise.

METHODS

For this purpose, breathing pattern and tidal exercise flow-volume loops were recorded at two workloads (30% and 80% of the peak power output) of a constant load exercise test.

RESULTS

Twelve patients were included (11 women, mean age 41 ± 14 years). The results showed a decrease (p = 0.028) in the inspiratory capacity (from 3.12 ± 0.49 L to 2.97 ± 0.52 L), an increase (p = 0.025) in the end-expiratory lung volume (from 0.73 ± 0.68 L to 0.88 ± 0.66 L, i.e., from EELV comprising 17 ± 12% to 21 ± 12% of forced vital capacity) between the two workloads in favor of dynamic hyperinflation, and half of the patients had expiratory flow limitations.

CONCLUSION

This exploratory study provides evidence for mechanical ventilatory constraints during exercise in patients with hEDS, which may induce discomfort during exercise and could contribute to the respiratory symptomatology.

TRIAL REGISTRATION NUMBER

This study is part of a larger clinical trial (ID: NCT04680793, December 2020).

Intercostal muscle oxygenation and expiratory loaded breathing at rest: Respiratory pattern effect

In patients with airway obstruction, an increase in breathing frequency at rest is commonly associated with a dynamic hyperinflation (DH). In such a situation, intercostal muscle oxygenation may be disturbed. This hypothesis was examined in a context of simulated airway obstruction in healthy subjects. After a control period of 5 min, twelve participants (20 ± 2 years) breathed at rest through a 20-cmH₂O expiratory threshold load, either by increasing or reducing their respiratory rate (_ETLF⁺ or _ETLF). Tissue saturation index (TSI) and concentration changes in oxyhaemoglobin (oxy[Hb+Mb]) were measured as well as cardiorespiratory variables. Inspiratory capacity was decreased in _ETLF⁺ (p < 0.001) and correlated with dyspnea. An increase in oxy[Hb+Mb] occurred in _ETLF⁺ that was higher than in _ETLF (p < 0.01). TSI was not different between conditions. In healthy subjects at rest, an increase in respiratory rate during a simulated obstruction with an expiratory threshold load resulted in paradoxical response with DH emergence while intercostal muscle oxygenation was preserved.

A randomized, crossover, placebo controlled, double blind trial of the effects of tiotropium-olodaterol on neuromuscular performance during exercise in COPD

Exercise intolerance in COPD is associated with dyspnea, reduced inspiratory capacity (IC) and occurs with a neuromuscular "power reserve" i.e. an acute ability to increase isokinetic locomotor power. This power reserve is associated with resting FEV₁/FVC suggesting that treatments to target pulmonary function may protect neuromuscular performance and extend whole-body exercise in COPD. We, therefore, tested whether combination long-acting β-agonist and muscarinic antagonist bronchodilator therapy (LAMA+LABA; Stiolto Respimat®) would ameliorate the decline in neuromuscular performance and increase endurance time during constant power cycling at 80% peak incremental power. Fourteen COPD patients (4 female; 64[58,72] years; FEV₁ 67[56,75]% predicted; median[25^th,75^th percentile]), participated in a randomized, placebo-controlled cross-over trial (NCT02845752). Pulmonary function and cardiopulmonary exercise responses were assessed before and after 1 week of treatment, with 2 weeks washout between conditions. Performance fatigue was assessed using a ~4-second maximal isokinetic cycling effort at pre-exercise, isotime and intolerance. Isotime was the shorter exercise duration of the two treatment conditions. Significance was assessed using ANOVA with treatment as fixed factor and subject as random factor. FEV₁ was greater with LAMA+LABA vs. placebo (1.81[1.58,1.98] L vs 1.72[1.29,1.99] L; P=0.006), but IC at isotime, performance fatigue at isotime and constant power endurance time were not different between condition (each P>0.05). A modest (~95 mL) FEV₁ increase in following 1 week of combination LAMA+LABA treatment did not alleviate neuromuscular performance fatigue or enhance cycle exercise tolerance in mild to severe COPD patients with largely preserved "static" lung volumes.

The role of inspiratory capacity and tidal flow in diagnosing exercise ventilatory limitation in Cystic Fibrosis

BACKGROUND

Exercise ventilatory limitation conventionally defined by reduced breathing reserve (BR) may underestimate the effect of lung disease on exercise capacity in patients with mild to moderate obstructive lung diseases.

OBJECTIVE

To investigate whether ventilatory limitation may be present despite a normal BR in Cystic Fibrosis (CF).

METHODS

Twenty adult CF patients (age 16-58y) with a wide range of pulmonary obstruction severity completed a symptom-limited incremental exercise test on a cycle ergometer. Operating lung volumes were derived from inspiratory capacity (IC) measurement during exercise and exercise tidal flow volume loop analysis.

RESULTS

six patients had a severe airway obstruction (FEV₁<45% predicted) and conventional evidence of ventilatory limitation (low BR). Fourteen patients had mild to moderate-severe airway obstructive (FEV₁ 46-103% predicted), and a normal BR [12-62 L/min, BR% (17-40)]. However, dynamic respiratory mechanics demonstrated that even CF patients with mild to moderate-severe lung disease had clear evidence of ventilatory limitation during exercise. IC was decreased by (median) 580 ml (range 90-1180 ml) during exercise, indicating dynamic hyperinflation. Inspiratory reserve volume at peak exercise was 445 ml (241-1350 ml) indicating mechanical constraint on the respiratory system. The exercise tidal flow met or exceeded the expiratory boundary of the maximal flow volume loop over 72% of the expiratory volume (range 40-90%), indicating expiratory flow limitation.

CONCLUSION

Reduced BR as a sole criterion underestimates ventilatory limitation during exercise in mild to moderate-severe CF patients. Assessment of dynamic respiratory mechanics during exercise revealed ventilatory limitation, present even in patients with mild obstruction.

Predictors of exercise-induced bronchoconstriction in subjects with mild asthma

Background

Physical effort is capable of triggering airway obstruction in asthmatics, the so-called exercise-induced bronchoconstriction in asthma (EIBa). This study was performed in subjects with mild persistent asthma, aiming to find predictors for developing EIBa.

Methods

In 20 subjects with mild asthma, measurements of baseline functional respiratory parameters and airways responsiveness by a methacholine challenge were obtained on the first day. A maximal, symptom-limited incremental cardiopulmonary exercise test (CPExT) was performed the day after, with subsequent, repeated maneuvers of maximal full forced expiration to monitor the FEV₁ change at 1,3,5,7,10 and 15 min after the end of the exercise.

Results

19 subjects completed the two-days protocol. No functional parameters both at rest and during effort were useful to predict EIBa after stopping exercise. In asthmatics with EIBa, mean Inspiratory Capacity (IC) did not increase with increasing ventilatory requirements during CPExT because 6 of them (50%) displayed dynamic pulmonary hyperinflation (DH), as documented by their progressive increase of end-expiratory lung volume. This subgroup, showing earlier post-exercise FEV₁ fall, had significantly lower forced mean expiratory flow between 25% and 75% of forced vital capacity (FEF_25-75%) at rest (p < 0.05) and higher airways responsiveness, expressed as PD₂₀FEV₁ (p < 0.05) as compared with other asthmatics with EIBa.

Conclusions

No functional respiratory parameters seem to predict EIBa in mild asthmatics. However, in those with EIBa, a subgroup developed DH during exercise, and this was associated with a baseline reduced forced expiratory flow rates at lower lung volumes and higher airway hyperresponsiveness, suggesting a prominent small airways impairment.

Effect of Dynamic Hyperinflation on Cardiac Response to Exercise of Patients With Chronic Obstructive Pulmonary Disease

INTRODUCTION

Although the major limitation to exercise performance in patients with COPD is dynamic hyperinflation (DH), little is known about its relation with cardiac response to exercise. Our objectives were to compare the exercise response of stroke volume (SV) and cardiac output (CO) between COPD patients with or without DH and control subjects, and to assess the main determinants.

METHODS

Fifty-seven stable COPD patients without cardiac comorbidity and 25 healthy subjects were recruited. Clinical evaluation, baseline function tests, computed tomography and echocardiography were conducted in all subjects. Patients performed consecutive incremental exercise tests with measurement of operating lung volumes and non-invasive measurement of SV, CO and oxygen uptake (VO₂) by an inert gas rebreathing method. Biomarkers of systemic inflammation and oxidative stress, tissue damage/repair, cardiac involvement and airway inflammation were measured.

RESULTS

COPD patients showed a lower SV/VO₂ slope than control subjects, while CO response was compensated by a higher heart rate increase. COPD patients with DH experienced a reduction of SV/VO₂ and CO/VO₂ compared to those without DH. In COPD patients, the end-expiratory lung volume (EELV) increase was related to SV/VO₂ and CO/VO₂ slopes, and it was the only independent predictor of cardiac response to exercise. However, in the regression models without EELV, plasma IL-1β and high-sensitivity cardiac troponin T were also retained as independent predictors of SV/VO₂ slope.

CONCLUSION

Dynamic hyperinflation decreases the cardiac response to exercise of COPD patients. This effect is related to systemic inflammation and myocardial stress but not with left ventricle diastolic dysfunction.

Decapneization as supportive therapy for the treatment of status asthmaticus: a case report

Background

Acute severe asthma is a life-threatening medical emergency. Characteristics of asthma include increased airway resistance and dynamic pulmonary hyperinflation that can manifest in dangerous levels of hypercapnia and acidosis, with significant mortality and morbidity. Severe respiratory distress can lead to endotracheal intubation followed by mechanical ventilation, which can cause increased air trapping with dynamic hyperinflation, predisposing the lungs to barotraumas.

Case presentation

The present case report describes the use of the minimally invasive ECCO₂R ProLUNG^® (Estor) with protective low-tidal-volume ventilation, in a Caucasian patient with near-fatal asthma and with no response to conventional therapy.

Conclusions

Since hypercarbia rather than hypoxemia is the primary abnormality in status asthmaticus, a rescue therapeutic strategy combining the ECCO₂R membrane ProLUNG^® (Estor) with ultra-protective low-tidal-volume ventilation can be successfully applied to limit the risk of severe barotrauma during invasive mechanical ventilation. ECCO₂R ProLUNG^® is a partial respiratory support technique that, based on the use of an extracorporeal circuit with a gas-exchange membrane, achieves relevant CO₂ clearance directly from the blood using double-lumen venous-venous vascular access, at blood flow in the range of 0.4–1.0 L/minute.

Comparison of Multiple Diagnostic Tests to Measure Dynamic Hyperinflation in Patients with Severe Emphysema Treated with Endobronchial Coils

Purpose

For this study, we aimed to compare dynamic hyperinflation measured by cardiopulmonary exercise testing (CPET), a six-minute walking test (6-MWT), and a manually paced tachypnea test (MPT) in patients with severe emphysema who were treated with endobronchial coils. Additionally, we investigated whether dynamic hyperinflation changed after treatment with endobronchial coils.

Methods

Dynamic hyperinflation was measured with CPET, 6-MWT, and an MPT in 29 patients before and after coil treatment.

Results

There was no significant change in dynamic hyperinflation after treatment with coils. Comparison of CPET and MPT showed a strong association (rho 0.660, p < 0.001) and a moderate agreement (BA-plot, 202 ml difference in favor of MPT). There was only a moderate association of the 6-MWT with CPET (rho 0.361, p 0.024).

Conclusion

MPT can be a suitable alternative to CPET to measure dynamic hyperinflation in severe emphysema but may overestimate dynamic hyperinflation possibly due to a higher breathing frequency.

Dynamic hyperinflation, chronotropic intolerance and abnormal heart rate recovery in non-severe chronic obstructive pulmonary disease patients-reflections in the mirror

BACKGROUND

The presence of abnormal heart rate recovery (HRR) and chronotropic incompetence (CI) suggests autonomic dysfunction (AD) and is associated with diminished physical activity and increased cardio-vascular (CV) risk.

AIM

Our aim is to analyse the correlation between AD and airflow obstruction - forced expiratory volume in 1s (FEV1), dynamic hyperinflation (DH) and disease prognosis - the BODE - index (BMI; Obstruction - FEV1;Dyspnea - mMRC;E - exercise capacity) in non-severe COPD patients without overt CV comorbidities.

METHODS

We used cardio-pulmonary exercise testing (CPET) with 67 subjects. Inspiratory capacity (IC) manouevres were performed for DH assessment. Echocardiography was executed before CPET and 1-2min after peak exercise. Stress left ventricular diastolic dysfunction (LVDD) was assumed if stress E/e'>15.Wilkoff method calculated the metabolic-chronotropic relationship (MCR). Chronotropic incompetence (CI) and abnormal HR recovery (HRR) were determined.

MAIN RESULTS

CI was detected in 44% of the mild and 65% of the moderate COPD patients. Abnormal HRR was present in 75% of the mild and 78% of the moderate COPD subjects. Multivariate regression analysis showed no association between FEV1, CPET parameters, BODE index, stress LVDD and AD. DH was the only independent predictor for both abnormal HRR and CI.

CONCLUSION

Evaluation of AD during incremental CPET unravels lung hyperinflation as a potential mechanism of attenuated HR response and diminished physical activity in non-severe COPD free of overt CV comorbidities. This multifaceted approach to dyspnea may facilitate the discrimination of its pathogenesis and improve its proper clinical management.

Respiratory function, autonomic dysfunction, and systemic inflammation are closely linked in patients with COPD and tidal flow limitation: An exploratory study

RATIONALE

The study aimed to investigate the interplay among respiratory function, autonomic dysfunction, and systemic inflammation in COPD patients.

METHODS

In 19 COPD patients, functional respiratory parameters, heart rate variability (HRV), and plasma high-sensitivity-C-reactive-protein (hs-CRP) were assessed. Forced oscillation technique (FOT) was used to detect the absence (NFL) or presence (FL) of resting tidal expiratory flow limitation. Subsequently, patients underwent an incremental shuttle walking test (ISWT). Twenty healthy subjects were also shown as controls.

RESULTS

FEV₁, DL_CO, and lung volumes displayed significant correlations with LH/FH ratio (0.56 < r²<0.27,p < 0.01). A significant relationship was found between LH/FH ratio with IC/TLC ratio% (r² = 0.29,p < 0.05) and hs-CRP (r² = 0.26,p < 0.05). Patients with FL had greater hs-CRP plasma levels (p < 0.05), lower IC/TLC% (p < 0.05), and higher LH/FH ratio (p<0.001).

CONCLUSIONS

Worse airflow obstruction was associated with a higher LH/HF ratio, directly related, to hs-CRP and indices of dynamic hyperinflation. The presence of resting tidal FL with dynamic pulmonary hyperinflation is a strong driver of systemic inflammation and autonomic dysfunction.

Effect of Dynamic Hyperinflation on Cardiac Response to Exercise of Patients With Chronic Obstructive Pulmonary Disease

INTRODUCTION

Although the major limitation to exercise performance in patients with COPD is dynamic hyperinflation (DH), little is known about its relation with cardiac response to exercise. Our objectives were to compare the exercise response of stroke volume (SV) and cardiac output (CO) between COPD patients with or without DH and control subjects, and to assess the main determinants.

METHODS

Fifty-seven stable COPD patients without cardiac comorbidity and 25 healthy subjects were recruited. Clinical evaluation, baseline function tests, computed tomography and echocardiography were conducted in all subjects. Patients performed consecutive incremental exercise tests with measurement of operating lung volumes and non-invasive measurement of SV, CO and oxygen uptake (VO₂) by an inert gas rebreathing method. Biomarkers of systemic inflammation and oxidative stress, tissue damage/repair, cardiac involvement and airway inflammation were measured.

RESULTS

COPD patients showed a lower SV/VO₂ slope than control subjects, while CO response was compensated by a higher heart rate increase. COPD patients with DH experienced a reduction of SV/VO₂ and CO/VO₂ compared to those without DH. In COPD patients, the end-expiratory lung volume (EELV) increase was related to SV/VO₂ and CO/VO₂ slopes, and it was the only independent predictor of cardiac response to exercise. However, in the regression models without EELV, plasma IL-1β and high-sensitivity cardiac troponin T were also retained as independent predictors of SV/VO₂ slope.

CONCLUSION

Dynamic hyperinflation decreases the cardiac response to exercise of COPD patients. This effect is related to systemic inflammation and myocardial stress but not with left ventricle diastolic dysfunction.

Change in Dynamic Hyperinflation After Bronchoscopic Lung Volume Reduction in Patients with Emphysema

BACKGROUND AND PURPOSE

In patients with severe emphysema, dynamic hyperinflation is superimposed on top of already existing static hyperinflation. Static hyperinflation reduces significantly after bronchoscopic lung volume reduction (BLVR). In this study, we investigated the effect of BLVR compared to standard of care (SoC) on dynamic hyperinflation.

METHODS

Dynamic hyperinflation was induced by a manually paced tachypnea test (MPT) and was defined by change in inspiratory capacity (IC) measured before and after MPT. Static and dynamic hyperinflation measurements were performed both at baseline and 6 months after BLVR with endobronchial valves or coils (treatment group) or SoC (control group).

RESULTS

Eighteen patients underwent BLVR (78% female, 57 (43-67) years, FEV₁ 25(18-37) %predicted, residual volume 231 (182-376) %predicted). Thirteen patients received SoC (100% female, 59 (44-74) years, FEV₁ 25 (19-37) %predicted, residual volume 225 (152-279) %predicted. The 6 months median change in dynamic hyperinflation in the treatment group was: + 225 ml (range - 113 to + 803) (p < 0.01) vs 0 ml (- 1067 to + 500) in the control group (p = 0.422). An increase in dynamic hyperinflation was significantly associated with a decrease in residual volume (r = - 0.439, p < 0.01).

CONCLUSION

Bronchoscopic lung volume reduction increases the ability for dynamic hyperinflation in patients with severe emphysema. We propose this is a consequence of improved static hyperinflation.

Health Services Utilization Is Increased in Poor Perceivers of Bronchoconstriction and Hyperinflation in Asthma

BACKGROUND

Impaired symptom perception is often listed as a risk factor for life-threatening asthma, but there is limited evidence to support this.

OBJECTIVE

We aimed to determine whether impaired perception of bronchoconstriction (BC) and/or dynamic hyperinflation (DH) are risk factors for severe asthma exacerbations.

METHODS

In this prospective cohort study, individuals with asthma underwent high-dose methacholine challenge testing. Changes in forced expiratory volume in 1 second (FEV₁) (% predicted) and inspiratory capacity (IC) (% predicted) were measured to assess the degree of BC and DH, respectively, during high-dose methacholine bronchoprovocation. Participants rated dyspnea intensity during testing and were categorized as poor, normal, and over perceivers of BC and DH based on perception scores at standardized changes (20%, 30%, and 40%) in FEV₁ (% predicted) and IC (% predicted). We compared the rates of severe asthma exacerbations (defined as one of emergency department [ED] visit or hospitalization) between groups, using Ontario's administrative health databases.

RESULTS

Poor perceivers had higher rates of ED visits and hospitalizations as compared with normal perceivers at 4 of 6 threshold decreases in FEV₁ and IC studied. Poor perceivers of severe DH had a 6-fold increase in asthma exacerbations (odds ratio, 5.7; 95% confidence interval, 1.31-25.03).

CONCLUSIONS

Health services utilization is increased in individuals with asthma who have poor perception of BC and DH. Poor perceivers of severe DH appear to be at the highest risk of exacerbations.

Cardiopulmonary exercise testing in patients with asthma: What is its clinical value?

Asthma is one of the most common respiratory disorders, characterized by fully or largely reversible airflow limitation. Asthma symptoms can be triggered or magnified during exertion, while physical activity limitation is often present among asthmatic patients. Cardiopulmonary exercise testing (CPET) is a dynamic, non-invasive technique which provides a thorough assessment of exercise physiology, involving the integrative assessment of cardiopulmonary, neuromuscular and metabolic responses during exercise. This review summarizes current evidence regarding the utility of CPET in the diagnostic work-up, functional evaluation and therapeutic intervention among patients with asthma, highlighting its potential role for thorough patient assessment and physician clinical desicion-making.

Mechanical Ventilation Strategies for the Patient with Severe Obstructive Lung Disease

Patients with respiratory failure due to obstructive lung disease present a challenge to the emergency physician. These patients have physiologic abnormalities that prevent adequate gas exchange and lung mechanics which render them at increased risk of cardiopulmonary decompensation when managed with invasive mechanical ventilation. This article addresses key principles when managing these challenging patients: patient-ventilator synchrony, air trapping and auto-positive end-expiratory pressure, and airway pressures. This article provides a practical workflow for the emergency physician responsible for managing these patients.

Continuous monitoring of intrinsic PEEP based on expired CO2 kinetics: an experimental validation study

Background

Quantification of intrinsic PEEP (PEEPi) has important implications for patients subjected to invasive mechanical ventilation. A new non-invasive breath-by-breath method (etCO₂D) for determination of PEEPi is evaluated.

Methods

In 12 mechanically ventilated pigs, dynamic hyperinflation was induced by interposing a resistance in the endotracheal tube. Airway pressure, flow, and exhaled CO₂ were measured at the airway opening. Combining different I:E ratios, respiratory rates, and tidal volumes, 52 different levels of PEEPi (range 1.8–11.7 cmH₂O; mean 8.45 ± 0.32 cmH₂O) were studied. The etCO₂D is based on the detection of the end-tidal dilution of the capnogram. This is measured at the airway opening by means of a CO₂ sensor in which a 2-mm leak is added to the sensing chamber. This allows to detect a capnogram dilution with fresh air when the pressure coming from the ventilator exceeds the PEEPi. This method was compared with the occlusion method.

Results

The etCO₂D method detected PEEPi step changes of 0.2 cmH₂O. Reference and etCO₂D PEEPi presented a good correlation (R² 0.80, P < 0.0001) and good agreement, bias − 0.26, and limits of agreement ± 1.96 SD (2.23, − 2.74) (P < 0.0001).

Conclusions

The etCO₂D method is a promising accurate simple way of continuously measure and monitor PEEPi. Its clinical validity needs, however, to be confirmed in clinical studies and in conditions with heterogeneous lung diseases.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2430-9) contains supplementary material, which is available to authorized users.

The value of high-resolution computed tomography (HRCT) to determine exercise ventilatory inefficiency and dynamic hyperinflation in adult patients with cystic fibrosis

Introduction

In Cystic Fibrosis (CF), exercise ventilatory inefficiency and dynamic hyperinflation (DH) cause exercise limitation and induce poor exercise tolerance. High-resolution computed tomography (HRCT) of the lung can detect pulmonary abnormalities in CF patients. We aimed to identify the determinants of exercise ventilatory inefficiency and DH using HRCT-derived metrics.

Methods

Fifty-two adult CF patients were prospectively enrolled; all participants underwent cardio-pulmonary exercise test (CPET) and HRCT. Radiological impairment was evaluated by the Brody II scoring system. Slope and intercept of the minute ventilation/CO₂ production (V’_E/V’_CO2) regression line and the ratio of inspiratory capacity/total lung capacity (IC/TLC) at rest and at peak of exercise were measured.

Results

Four groups of patients were identified based on the combination of ventilatory efficiency (Vef) or inefficiency (Vin) and the presence/absence of DH. Compared to other groups, CF adults with Vin and DH had worse functional status and higher total (T), bronchiectasis (B) and air trapping (AT) scores at HRCT. Significant correlations were found between V’_E/V’_{CO2 intercept} and V’_E/V’_{CO2 slope} (ρ − 0.455, p = 0.001) and between V’_E/V’_{CO2 intercept} and Δ inspiratory capacity (IC) (ρ − 0.334, p = 0.015). Regression analysis identified AT score (cut-off 7.9, odds ratio-OR 3.50) as the only independent predictor of Vin and T (cut-off 53.6, OR 4.98), B (cut-off 16.1, OR 4.88), airways wall thickening (AWT) (cut-off 13, OR 3.41), and mucous plugging (MP) scores (cut-off 11.7, OR 4.18) as significant predictors of DH.

Conclusion

In adult CF cohort, values of HRCT metrics are determinants of Vin (AT) and DH (T, B, AWT, MP).

Is the Metronome-Paced Tachypnea Test (MPT) Ready for Clinical Use? Accuracy of the MPT in a Prospective and Clinical Study

BACKGROUND

A simple technique to measure dynamic hyperinflation (DH) in patients with chronic obstructive pulmonary disease (COPD) is the metronome-paced tachypnea test (MPT). Earlier studies show conflicting results about the accuracy of the MPT compared to cardiopulmonary exercise testing (CPET).

OBJECTIVES

The focus was to investigate the diagnostic accuracy of MPT to detect DH in a prospective and clinical study.

METHODS

COPD patients were included; all underwent spirometry, CPET, and MPT. DH (ΔIC) was calculated as the difference in % between inspiratory capacity (IC) at the start and end of the test divided by IC at the start. A subject was identified as a hyperinflator, if ΔIC (% of ICrest) was smaller than -10.2 and -11.1% in CPET and MPT, respectively. With these values, sensitivity and specificity were calculated. Bland-Altman plots were made of ΔIC (% of ICrest).

RESULTS

In the prospective and clinical study, 107 and 48 patients were included, respectively. Sensitivity of the MPT was 85% in both studies. The specificities were 33 and 27%, respectively. In the prospective study, B = +2.6%, L = 30.6, and -25.6%. In the clinical study, B = +0.8%, L = 31.0, and -29.1%.

CONCLUSION

MPT seems to be a good replacement for CPET in group studies. The mean amount of DH was not different between CPET and MPT. On an individual level, MPT cannot be used to identify hyperinflators; it should be kept in mind that MPT overdiagnoses DH. The amount of DH should not be interchanged between CPET and MPT.

Combination of assist use of short-acting beta-2 agonists inhalation and guidance based on patient-specific restrictions in daily behavior: Impact on physical activity of Japanese patients with chronic obstructive pulmonary disease

BACKGROUND

Assist use of inhaled short-acting beta 2 agonists (SABAs) is reportedly effective for preventing shortness of breath on exertion in chronic obstructive pulmonary disease (COPD) patients. However, it is unclear what strategy would be useful for improving physical activity in such patients. The aim is to investigate the effects of assisted use of SABA (procaterol) on physical activity in Japanese COPD patients targeting patient-specific restrictions in daily behavior.

METHODS

Fourteen patients with stable COPD (age: 72.1±1.5, %FEV₁: 55.6±4.5%) were asked to inhale 20 μg of procaterol 15 minutes before patient-specific daily physical activity that had been identified as limited by a questionnaire and document their usage in a diary. Physical activity was measured using a triaxial accelerometer and the results were collected every month for 2 months. In the first month, a clinician assessed whether inhalation of SABA was appropriate based on a usage diary and coached patients to conduct adequate assist use of SABA for limited physical activity.

RESULTS

The strategy significantly improved the physical activity level, assessed using the values of the metabolic equivalents (METs) multiplied by physical activity endurance, at ≥3.0 METs (p<0.05), and physical activity endurance at ≥2.5 and ≥3.0 METs, (p<0.05, p<0.05, respectively). The degree of improvement of physical activity level was significantly positively correlated with the baseline %FVC and %FEV₁ (p<0.05, p<0.05, respectively).

CONCLUSIONS

Assist use of SABA targeting patient-specific restrictions, particularly when better lung function is still preserved, could be a useful approach for improving physical activity in patients with COPD.

Improvement of exertional dyspnea and breathing pattern of inspiration to expiration after bronchial thermoplasty

Background

Bronchial thermoplasty (BT) is a bronchoscopic treatment that can ameliorate the symptoms of severe asthma. However, little is known about the mechanism by which BT improves exertional dyspnea without significantly changing the resting pulmonary function in asthmatics. To understand the mechanism, cardiopulmonary variables were investigated using cardiopulmonary exercise testing (CPET) in a patient with severe asthma before and after BT.

Case presentation

A 57-year-old Japanese man visited our hospital for consultation of the intractable asthma, which we managed with three treatment sessions of BT. Comparison of the findings pre-BT and at 1 year after BT demonstrated that (1) the resting tests for respiration showed no improvement in forced expiratory volume in 1 s, but the forced oscillation technique showed decreases in both inhalation and exhalation respiratory resistance values, and (2) the CPET results showed (i) improvement in exertional dyspnea, exercise endurance, and arterial oxygen saturation at the end of exercise; (ii) that the expiratory tidal volume exceeded the inspiratory tidal volume during exercise, which implied that a sufficient exhalation enabled longer inspiratory time and adequate oxygen absorption; and (iii) that an increase in respiratory frequency could be prevented throughout exercise.

Conclusions

This case report described a novel mechanism of BT in improving exertional dyspnea and exercise duration, which was brought about by ventilatory improvements related to the breathing pattern of inspiration to expiration.

Is daily physical activity affected by dynamic hyperinflation in adults with cystic fibrosis?

Background

The aim of this study was to investigate the relationship between dynamic hyperinflation and daily physical activity (DPA) in adults with cystic fibrosis (CF).

Methods

Thirty-four clinically stable CF were studied. All patients undertook incremental cardiopulmonary exercise testing (CPET). CPET-related measurements included: oxygen uptake (V’O₂), carbon dioxide production (V’CO₂), ventilatory profile, work rate (W), inspiratory capacity (IC), end-expiratory lung volume (EELV). PA was assessed using the accelerometer SenseWear Pro3 Armband.

Results

Exercise tolerance was reduced in most of patients and the mean V’O_2,peak value was 75.2% of predicted (28.5 ± 4.8 ml/min/kg). Seventy % of patients responded to CPET with dynamic hyperinflation. Higher incidence of dynamic hyperinflation was found in CF males compared to CF females (p = 0.026). Patients who developed dynamic hyperinflation during CPET had higher vigorous PA (p = 0.01) and more total energy expenditure (p = 0.006) than patients who did not. EELVΔ was related to activities requiring vigorous intensity and total energy expenditure (R = 0.46, p = 0.001; R = 0.57, p <  0.001).

Conclusions

In adults with CF and mild to moderate lung impairment, DPA might not be limited by dynamic hyperinflation.

Electronic supplementary material

The online version of this article (10.1186/s12890-018-0623-7) contains supplementary material, which is available to authorized users.

Effect of tiotropium on spontaneous expiratory flow-volume curves during exercise in GOLD 1-2 COPD

This substudy of a large, randomized, controlled trial (NCT01072396) examined tiotropium (18 μg qd) effects on dynamic hyperinflation during constant work rate treadmill exercise. Areas-under-the-spontaneous expiratory flow-volume (SEFV)-curves were compared in 20 COPD patients and 16 age-matched untreated controls, using rectangular area ratio (RAR) between peak intrabreath and end-expiratory flow. Seven patients exhibited SEFV curve concavity with RAR ≤ 0.5 (RAR_low) in ≥1 test without tiotropium; (mean ± SD FEV₁: 1.60 ± 0.59 L; 63.4 ± 14.0%predicted). In RAR_low patients, tiotropium increased end-exercise inspiratory capacity (IC, 2.10 ± 0.05 vs. 1.89 ± 0.05 L, tiotropium vs. placebo; p = 0.045) and RAR (0.57 ± 0.02 vs. 0.53 ± 0.02; p < 0.001). Patients without SEFV curve concavity with RAR > 0.5 (n = 13; RAR_high), had higher screening FEV₁ (2.15 ± 0.47 L; 79.6 ± 10.1%predicted) versus RAR_low patients and no difference in end-exercise IC and RAR between tiotropium and placebo (IC: 2.24 ± 0.03 vs. 2.17 ± 0.03 L; RAR: 0.63 ± 0.005 vs. 0.62 ± 0.005). RAR and%predicted IC at peak exercise were positively correlated in RAR_low patients (R² = 0.43, p = 0.0002). Tiotropium increased exercise RAR in GOLD 1-2 patients with SEFV curve concavity.

Assessment of dyspnea and dynamic hyperinflation in male patients with chronic obstructive pulmonary disease during a six minute walk test and an incremental treadmill cardiorespiratory exercise test

The six minute walk test (6MWT) is a standardized test that provides information on exercise capacity in patients with COPD. It is considered a submaximal test in opposition to incremental cardiopulmonary exercise tests (CPET) that provide valuable information on all the systems involved in exercise.

OBJECTIVES

1. To compare the perceptive, physiological responses and degree of dynamic hyperinflation during two exercise tests: the 6MWT and the incremental CPET on a treadmill. 2. To evaluate how dyspnea is related to dynamic hyperinflation (DH) and other functional parameters in both tests.

METHODS

29 stable COPD male patients, age 68±5.8 years, mean post-bronchodilator FEV1 57±11%, were recruited. To evaluate dynamic hyperinflation, inspiratory capacity (IC) was measured at rest and upon completing each one of the tests. At the same time, perceived dyspnea and leg discomfort were rated on specific modified Borg scales.

RESULTS

The mean walk distance in 6MWT was 494±88m. The Borg scale rating for shortness of breath upon completing the test was 4.7±2, whilst 2.9±2 for leg discomfort. IC changed from 2.53±0.63l before to 2.34±0.60l after completion of the test. In the treadmill CPET, maximal oxygen consumption (V˙O₂max) was 21.8±5mL/kg/min with 6.6±2 dyspnea and 4.3±2 leg discomfort on Borg scales. IC changed from 2.17±0.53l to 1.20±0.43l.

CONCLUSIONS

Dynamic hyperinflation occurs in male COPD patients during submaximal exercise such as the 6MWT. This phenomenon is more pronounced after incremental CPET on a treadmill. Despite being dyspnea the dominant limiting symptom for both tests, we observed different physiological responses.

Effect of pulmonary rehabilitation on tidal expiratory flow limitation at rest and during exercise in COPD patients

We hypothesized that severe COPD patients who present with the disadvantageous phenomenon of Expiratory Flow Limitation (EFL) may benefit as COPD patients without EFL do after implementation of a Pulmonary Rehabilitation (PR) program. Forty-two stable COPD patients were studied at rest and during exercise. EFL and dynamic hyperinflation (DH) were documented using the negative expiratory pressure (NEP) technique and inspiratory capacity (IC) maneuvers, respectively. Patient centered outcomes were evaluated by the Saint-George's Respiratory Questionnaire (SGRQ) and the mMRC dyspnea scale. Before PR, 16 patients presented with EFL at rest and/or during exercise. After PR, EFL was abolished in 15 out of those 16 EFL patients who exhibited a significant increase in IC values. These were mainly accomplished through a modification of the breathing pattern. In the 26 NFL patients no increase was noted in their IC or a modification of their breathing pattern. However, both NFL and EFL COPD patients improved exercise capacity and patients centered outcomes undergoing the same PR program.

Exertional Dyspnoea in Chronic Respiratory Diseases: From Physiology to Clinical Application

Dyspnoea is a complex, highly personalized and multidimensional sensory experience, and its underlying cause and mechanisms are still being investigated. Exertional dyspnoea is one of the most frequently encountered symptoms of patients with cardiopulmonary diseases, and is a common reason for seeking medical help. As the symptom usually progresses with the underlying disease, it can lead to an avoidance of physical activity, peripheral muscle deconditioning and decreased quality of life. Dyspnoea is closely associated with quality of life, exercise (in)tolerance and prognosis in various conditions, including chronic obstructive pulmonary disease, heart failure, interstitial lung disease and pulmonary hypertension, and is therefore an important therapeutic target. Effective management and treatment of dyspnoea is an important challenge for caregivers, and therapeutic options that attempt to reverse its underlying cause have been only partially successful This "review" will attempt to shed light on the physiological mechanisms underlying dyspnoea during exercise and to translate/apply them to a broad clinical spectrum of cardio-respiratory disorders.

Relation of concavity in the expiratory flow-volume loop to dynamic hyperinflation during exercise in COPD

Active expiration during exercise can increase intrathoracic pressure yielding concavity in the expiratory flow-volume loop in COPD. We investigated the relationship between this concavity and dynamic hyperinflation (DH). 17 COPD patients (FEV₁: 38±10%pred, GOLD stage 3-4) and 12 healthy subjects performed cycle ergometer incremental exercise. Expiratory limb of the spontaneous flow-volume loop was analyzed breath-by-breath using a geometric approach (rectangular area ratio (RAR), Respir. Med., 104(3):389-96, 2010). RAR below 0.5 demonstrates expiratory limb concavity. DH was determined with serial inspiratory capacity maneuvers. 5 of 17 patients displayed little end-exercise concavity (RAR=0.52±0.04, group LCONC). 12 patients had concavity at rest and end-exercise RAR reached 0.40±0.03 (group HCONC). Healthy subjects showed no concavity. End-exercise RAR correlated with resting FEV₁%pred (R²=0.81, P<0.05). Group HCONC, compared to groups LCONC and H, reached significantly lower work rate, minute ventilation, and more dyspnea. DH inversely correlated with RAR (R²=0.81, P<0.05). Detection of concavity in spontaneous flow-volume loops may help assess DH and exercise limitation in COPD.

Typical patterns of expiratory flow and carbon dioxide in mechanically ventilated patients with spontaneous breathing

Incomplete expiration of tidal volume can lead to dynamic hyperinflation and auto-PEEP. Methods are available for assessing these, but are not appropriate for patients with respiratory muscle activity, as occurs in pressure support. Information may exist in expiratory flow and carbon dioxide measurements, which, when taken together, may help characterize dynamic hyperinflation. This paper postulates such patterns and investigates whether these can be seen systematically in data. Two variables are proposed summarizing the number of incomplete expirations quantified as a lack of return to zero flow in expiration (IncExp), and the end tidal CO₂ variability (varETCO₂), over 20 breaths. Using these variables, three patterns of ventilation are postulated: (a) few incomplete expirations (IncExp < 2) and small varETCO₂; (b) a variable number of incomplete expirations (2 ≤ IncExp ≤ 18) and large varETCO₂; and (c) a large number of incomplete expirations (IncExp > 18) and small varETCO₂. IncExp and varETCO₂ were calculated from data describing respiratory flow and CO₂ signals in 11 patients mechanically ventilated at 5 levels of pressure support. Data analysis showed that the three patterns presented systematically in the data, with periods of IncExp < 2 or IncExp > 18 having significantly lower variability in end-tidal CO₂ than periods with 2 ≤ IncExp ≤ 18 (p < 0.05). It was also shown that sudden change in IncExp from either IncExp < 2 or IncExp > 18 to 2 ≤ IncExp ≤ 18 results in significant, rapid, change in the variability of end-tidal CO₂ p < 0.05. This study illustrates that systematic patterns of expiratory flow and end-tidal CO₂ are present in patients in supported mechanical ventilation, and that changes between these patterns can be identified. Further studies are required to see if these patterns characterize dynamic hyperinflation. If so, then their combination may provide a useful addition to understanding the patient at the bedside.

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.

Air Current Applied to the Face Improves Exercise Performance in Patients with COPD

PURPOSE

Improving dyspnea and exercise performance are goals of COPD therapy. We tested the hypothesis that air current applied to the face would lessen dyspnea and improve exercise performance in moderate-severe COPD patients.

METHODS

We recruited 10 COPD patients (5 men, age 62 ± 6 years, FEV1 0.93 ± 0.11 L (34 ± 3% predicted), TLC 107 ± 6%, RV 172 ± 18%) naïve to the study hypothesis. Each patient was randomized in a crossover fashion to lower extremity ergometry at constant submaximal workload with a 12-diameter fan directed at the patients face or exposed leg. Each patients' studies were separated by at least 1 week. Inspiratory capacity and Borg dyspnea score were measured every 2 min and at maximal exercise.

RESULTS

Total exercise time was longer when the fan was directed to the face (14.3 ± 12 vs. 9.4 ± 7.6 min, face vs. leg, respectively, p = 0.03). Inspiratory capacity tended to be greater with the fan directed to the face (1.4 (0.6-3.25) vs. 1.26 (0.56-2.89) L, p = 0.06). There was a reduction in dynamic hyperinflation, as reflected by higher IRV area in the fan on face group (553 ± 562 a.u. vs. 328 ± 319 a.u., p = 0.047). There was a significant improvement in the Borg dyspnea score at maximal exercise (5.0 (0-10) vs. 6.5 (0-10), p = 0.03), despite exercising for 34 % longer with the fan directed to the face.

CONCLUSIONS

Air current applied to the face improves exercise performance in COPD. Possible mechanisms include an alteration in breathing pattern that diminishes development of dynamic hyperinflation or to a change in perception of breathlessness.

Reduced dynamic hyperinflation after LVRS is associated with improved exercise tolerance

INTRODUCTION

Dynamic hyperinflation (DH) after lung volume reduction surgery (LVRS) has not been well studied. It is not known if reductions in DH correlate with improvements in exercise performance post-LVRS.

METHODS

Forty-two upper-lobe predominant emphysema patients who underwent LVRS were analyzed. Inspiratory capacity was measured every 2 min during symptom-limited cardiopulmonary exercise test (CPET) and end-expiratory lung volumes (EELV) were calculated. The main measure of DH was EELV/TLC ratio matched at metabolic isotimes (based on the post-rehabilitation VCO2max).

RESULTS

Patients had very severe airflow obstruction (FEV1 28.3 ± 7.0% predicted), were hyperinflated (TLC 125 ± 17% predicted) and gas trapped (RV 198 ± 39% predicted). Compared to the post-rehab baseline, dynamic hyperinflation (EELV/TLC) was significantly reduced after LVRS at 6, 12, 24, and 36 months. There were also increases in inspiratory reserve volume at matched isotimes after surgery. Patients adopted a slower, deeper breathing pattern during exercise after LVRS, which strongly correlated to reductions in DH. There were significant correlations between reductions in DH (EELV/TLC @50% VCO2max) and improvements in 6 min walk distance (Pearson r = -0.411, p = 0.02, n = 33) and maximal watts on CPET (Spearman r = -0.536, p = 0.001, n = 33) when comparing post-rehabilitation and 6 month post-LVRS values.

CONCLUSION

Dynamic hyperinflation during exercise was reduced after LVRS (up to 3 years) and there was a strong association between alterations in breathing pattern and reduced DH after LVRS. This is the first study to demonstrate that reductions in DH correlated with improved exercise performance following LVRS.

Neuromuscular electrical stimulation improves clinical and physiological function in COPD patients

BACKGROUND

Neuromuscular electrical stimulation (NMES) improves muscle performance and exercise tolerance in chronic obstructive pulmonary disease (COPD) patients. In contrast, no study has assessed the effect of NMES on dynamic hyperinflation (DH) in COPD. This study investigated the effect of short-term, high-frequency NMES on DH in patients with COPD.

METHODS

Twenty patients were randomly allocated to either a NMES applied bilaterally to the quadriceps muscles (n = 11: 8 weeks, 5 days/week, twice/day, 45 min/session) or a control group (n = 09). All patients received respiratory physical therapy and stretching exercises. Free fat mass, pulmonary function, time to exercise tolerance (Tlim), 6-min walk test distance (6-MWTD), tumor necrosis factor (TNF-α) and β-endorphin levels, Borg dyspnea and leg score (BDS and BLS) and quality of life by the St. George's Respiratory Questionnaire score (SGRQ) were examined before and after the intervention.

RESULTS

Compared with the control group, NMES increased FEV1 and FEV1/FVC, 6-MWD and Tlim (P < 0.01) and reduced BDS and SGRQ (P < 0.01). Additionally, changes in the Tlim were positively correlated with respiratory improvements in FEV1 (rho = 0.48, P < 0.01). Also, NMES reduced TNF-α and increased β-endorphin levels, compared with the control group (P < 0.001).

CONCLUSION

In summary, 8 weeks of NMES promotes reduction of the perceived sensation of dyspnea during exercise in patients with COPD. This finding is accompanied by improvements in FEV1, exercise tolerance and quality of life, and DH. Interestingly, these findings may be associated with enhanced vasodilatory function and a reduction in inflammatory responses.

CLINICAL TRIAL REGISTRATION

NCT01695421.

Determinants of dynamic hyperinflation during metronome-paced tachypnea in COPD and normal subjects

In COPD, dynamic hyperinflation (DH) occurs during exercise and during metronome-paced tachypnea (MPT). We investigated the relationship of DH with breathing pattern and ventilation (V˙E) in COPD and normal subjects (NS). In 35 subjects with moderate COPD and 17 younger healthy volunteers we measured inspiratory capacity (IC), breathing frequency (fR), expiratory time (TE), ventilation (V˙E) and end-tidal carbon dioxide tension (PETCO2) at baseline and after 30s of MPT at 40breaths/min with metronome-defined I:E ratios of 1:1 and 1:2. A reduction in IC (ΔIC) was taken to indicate DH. In COPD subjects, DH correlated with TE but not with V˙E or PETCO2, and was best predicted by total lung capacity. NS also showed DH (although less than in COPD), which correlated with PETCO2 but not with fR, TE or V˙E. We conclude that MPT evokes DH in both NS and patients with COPD. TE is the most important determinant of DH during MPT in patients with COPD.