Chronic obstructive pulmonary disease: clinical integrative physiology

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.

Haemodynamic compensations for exercise tissue oxygenation in early stages of COPD: an integrated cardiorespiratory assessment study

BACKGROUND

Cardiovascular comorbidities are increasingly being recognised in early stages of chronic obstructive pulmonary disease (COPD) yet complete cardiorespiratory functional assessments of individuals with mild COPD or presenting with COPD risk factors are lacking. This paper reports on the effectiveness of the cardiocirculatory-limb muscles oxygen delivery and utilisation axis in smokers exhibiting no, or mild to moderate degrees of airflow obstruction using standardised cardiopulmonary exercise testing (CPET).

METHODS

Post-bronchodilator spirometry was used to classify participants as 'ever smokers without' (n=88), with 'mild' (n=63) or 'mild-moderate' COPD (n=56). All underwent CPET with continuous concurrent monitoring of oxygen uptake (V'O2) and of bioimpedance cardiac output (Qc) enabling computation of arteriovenous differences (a-vO2). Mean values of Qc and a-vO2 were mapped across set ranges of V'O2 and Qc isolines to allow for meaningful group comparisons, at same metabolic and circulatory requirements.

RESULTS

Peak exercise capacity was significantly reduced in the 'mild-moderate COPD' as compared with the two other groups who showed similar pulmonary function and exercise capacity. Self-reported cardiovascular and skeletal muscle comorbidities were not different between groups, yet disease impact and exercise intolerance scores were three times higher in the 'mild-moderate COPD' compared with the other groups. Mapping of exercise Qc and a-vO2 also showed a leftward shift of values in this group, indicative of a deficit in peripheral O2 extraction even for submaximal exercise demands. Concurrent with lung hyperinflation, a distinctive blunting of exercise stroke volume expansion was also observed in this group.

CONCLUSION

Contrary to the traditional view that cardiovascular complications were the hallmark of advanced disease, this study of early COPD spectrum showed a reduced exercise O2 delivery and utilisation in individuals meeting spirometry criteria for stage II COPD. These findings reinforce the preventive clinical management approach to preserve peripheral muscle circulatory and oxidative capacities.

High-intensity non-invasive ventilation during exercise-training versus without in people with very severe COPD and chronic hypercapnic respiratory failure: a randomised controlled trial

BACKGROUND

People with very severe chronic obstructive pulmonary disease (COPD) using nocturnal non-invasive ventilation (NIV) for chronic hypercapnic respiratory failure (CHRF) experience reduced exercise capacity and severe dyspnoea during exercise training (ET). The use of NIV during ET can personalise training during pulmonary rehabilitation (PR) but whether high-intensity NIV (HI-NIV) during exercise is accepted and improves outcomes in these extremely physically limited patients is unknown. The aim of this trial was to determine if ET with HI-NIV during PR was more effective than without at improving exercise capacity and reducing dyspnoea during exercise.

METHODS

Patients with COPD, CHRF and nocturnal-NIV were randomised to supervised cycle-ET as part of PR with HI-NIV or without (control). Primary outcome was change in cycle endurance time (ΔCETtime), while secondary outcomes were dyspnoea at isotime during the cycle endurance test and during ET-sessions and for the HI-NIV group, post-trial preferred exercising method.

RESULTS

Twenty-six participants (forced expiratory volume in 1 s 22±7%pred, PaCO251±7 mm Hg) completed the trial (HI-NIV: n=13, ET: IPAP 26±3/EPAP 6±1 cm H2O; control n=13). At completion of a 3 week ET-programme, no significant between-group differences in ΔCETtime were seen (HI-NIV-control: Δ105 s 95% CI (-92 to 302), p=0.608). Within-group ΔCETtime was significant (HI-NIV: +246 s 95% CI (61 to 432); control: +141 s 95% CI (60 to 222); all p<0.05). The number of responders (Δ>minimal important difference (MID)101 s: n=53.8%) was the same in both groups for absolute ΔCETtime and 69.2% of control and 76.9% of the HI-NIV group had a %change>MID33%.Compared with control, the HI-NIV group reported less isotime dyspnoea (Δ-2.0 pts. 95% CI (-3.2 to -0.8), p=0.005) and during ET (Δ-3.2 pts. 95% CI (-4.6 to -1.9), p<0.001). Most of the HI-NIV group (n=12/13) preferred exercising with NIV.

CONCLUSION

In this small group of patients with very severe COPD requiring nocturnal NIV, participation in an ET-programme during PR significantly improved exercise capacity irrespective of HI-NIV use. Reported dyspnoea was in favour of HI-NIV.

TRIAL REGISTRATION NUMBER

NCT03803358.

Cardiovascular Diseases in COPD: From Diagnosis and Prevalence to Therapy

Chronic obstructive pulmonary disease (COPD) is considered one of the leading causes of mortality. Cardiovascular comorbidities are diagnosed often in COPD patients, not only because of the common risk factors these two diseases share, but also because of the systemic inflammation which characterizes COPD and has deleterious effects in the cardiovascular system. The comorbid cardiovascular diseases in COPD result in several difficulties in the holistic treatment of these patients and affect outcomes such as morbidity and mortality. Several studies have reported that mortality from cardiovascular causes is common among COPD patients, while the risk for acute cardiovascular events increases during COPD exacerbations and remains high for a long time even after recovery. In this review, we focus on the prevalence of cardiovascular comorbidities in COPD patients, presenting the evidence regarding the interaction of the pathophysiological pathways which characterize each disease. Furthermore, we summarize information regarding the effects of cardiovascular treatment on COPD outcomes and vice versa. Finally, we present the current evidence regarding the impact of cardiovascular comorbidities on exacerbations, quality of life and survival of COPD patients.

Exertional dyspnea responses to the Dyspnea Challenge in heart failure: Comparison to chronic obstructive pulmonary disease

BACKGROUND

In heart failure (HF), exertional dyspnea is a common symptom, but validated field-based tests for its measurement are limited. The Dyspnea Challenge is a two-minute uphill treadmill walk designed to measure exertional dyspnea in cardiopulmonary disease.

OBJECTIVES

The purpose of this study was to establish the test-retest reliability of the Dyspnea Challenge in HF and to compare the exercise responses to a group with chronic obstructive pulmonary disease (COPD).

METHODS

The study was an experimental, single-blind, randomized, multi-site project that recruited individuals with HF (New York Heart Association I-III) and COPD (Global Initiative for Chronic Obstructive Lung Disease II-IV). Participants completed two visits. On the first visit, participants performed two six-minute walk tests (6MWT), followed by two to three Dyspnea Challenges to calculate treadmill speed and gradient. At Visit Two, participants performed two separate Dyspnea Challenges, with one including measures of pulmonary gas exchange and central hemodynamics.

RESULTS

Twenty-one individuals with HF (10 female; 66±11years; ejection fraction:45.3 ± 6.1%; six-minute distance(6MWD) 520 ± 97 m), and 25 COPD (11 female; 68 ± 10 yr; forced expiratory volume in 1 s:47.6 ± 11.5%; 6MWD: 430 ± 101 m). Intraclass correlation coefficients demonstrated excellent test-retest reliability for HF (0.94, P<.01) and COPD (0.95, P<.01). While achieving similar end-exercise exertional dyspnea intensities (P=.60), the HF group walked at a higher average speed (4.2 ± 0.8 vs. 3.5 ± 0.8km·h^-1) and gradient (10.3 ± 2.8 vs. 9.6 ± 2.8%) and a greater oxygen uptake (P<.01) and ventilation (P<.01) than those with COPD. While achieving similar cardiac outputs (P=.98), stroke volumes (P=.97), and heart rates (P=.83), those with HF displayed a larger arteriovenous oxygen difference (P<.01), while those with COPD exhibited greater decreases in inspiratory capacity (P=.03), arterial oxygen saturation (P=.02), and breathing reserve (P<.01).

CONCLUSIONS

The Dyspnea Challenge is a reliable test-retest measure of exertional dyspnea in HF. Typical to their pathologies, HF seemed limited by an inadequate modulation of cardiac output, while ventilatory constraints hampered those with COPD.

Efficacy of 12 weeks oral beta-alanine supplementation in patients with chronic obstructive pulmonary disease: a double-blind, randomized, placebo-controlled trial

BACKGROUND

Beta-alanine (BA) supplementation increases muscle carnosine, an abundant endogenous antioxidant and pH buffer in skeletal muscle. Carnosine loading promotes exercise capacity in healthy older adults. As patients with chronic obstructive pulmonary disease (COPD) suffer from elevated exercise-induced muscle oxidative/carbonyl stress and acidosis, and from reduced muscle carnosine stores, it was investigated whether BA supplementation augments muscle carnosine and induces beneficial changes in exercise capacity, quadriceps function, and muscle oxidative/carbonyl stress in patients with COPD.

METHODS

In this double-blind, randomized, placebo (PL)-controlled trial (clinicaltrials.gov identifier: NCT02770417), 40 patients (75% male) with COPD (mean ± standard deviation: age 65 ± 6 years; FEV₁ % predicted 55 ± 14%) were assigned to 12 weeks oral BA or PL supplementation (3.2 g/day). The primary outcome, i.e. muscle carnosine, was quantified from m. vastus lateralis biopsies obtained before and after intervention. Co-primary outcomes, i.e. incremental and constant work rate cycle capacity, were also assessed. Linear mixed model analyses were performed. Compliance with and side effects of supplement intake and secondary outcomes (quadriceps strength and endurance, and muscle oxidative/carbonyl stress) were also assessed.

RESULTS

Beta-alanine supplementation increased muscle carnosine in comparison with PL in patients with COPD (mean difference [95% confidence interval]; +2.82 [1.49-4.14] mmol/kg wet weight; P < 0.001). Maximal incremental cycling capacity (VO₂ peak: +0.5 [-0.7 to 1.7] mL/kg/min; P = 0.384, Wpeak: +5 [-1 to 11] W; P = 0.103) and time to exhaustion on the constant work rate cycle test (+28 [-179 to 236] s; P = 0.782) did not change significantly. Compliance with supplement intake was similar in BA (median (quartile 1-quartile 3); 100 (98-100)%) and PL (98 (96-100)%) (P = 0.294) groups, and patients did not report side effects possibly related to supplement intake. No change was observed in secondary outcomes.

CONCLUSIONS

Beta-alanine supplementation is efficacious in augmenting muscle carnosine (+54% from mean baseline value) without side effects in patients with COPD in comparison with PL. However, accompanied beneficial changes in exercise capacity, quadriceps function, and muscle oxidative/carbonyl stress were not observed.

Exertional Dyspnoea responses reported in the Dyspnoea Challenge and measures of disease severity in COPD

BACKGROUND

The Dyspnoea Challenge has been developed to facilitate the field-based measure of exertional dyspnoea(ED). To further validate the test, we aimed to; investigate the relationship between end-exercise ED, generated by a fixed-intensity Dyspnoea Challenge(DC_FIX), and measures of disease severity (Forced expiratory volume in 1 s(FEV₁), six-minute walk distance(6MWD), breathing reserve(V̇_E/MVV), modified medical research council dyspnoea scale (mMRC), Body-mass index, airflow Obstruction, Dyspnoea, and Exercise (BODE index) and compare the physiological response of the DC_FIX to a six-minute walk test(6MWT).

METHODS

Thirty-two individuals (15 female) with COPD (GOLD II-IV) (age: 69.7 ± 9.4 yrs; FEV₁: 49.1 ± 18.2 %) performed 2×6MWT and 2xDC_FIX at a treadmill speed of 3 km h^-1 and gradient of 4 %. The intensity of ED was measured using the modified Borg dyspnoea scale at baseline and end-exercise with heart rate (HR) and oxygen saturation (S_pO₂) monitored continuously. During 1×6MWT and 1xDC_FIX pulmonary gas exchange, cardiac output (Q̇) and dynamic hyperinflation were measured.

RESULTS

End-exercise ED measured during the DC_FIX was not correlated to FEV₁, but moderately correlated to; 6MWD(r_s = -0.54, P < .01), V̇_E/MVV (r_s = 0.46, P = .02), mMRC(r_s = 0.45, P = .01), and the BODE index(r_s = 0.53, P < .01). When comparing the DC_FIX and 6MWT, participants walked to comparable levels of oxygen consumption(P = .38), ventilation(P = .37), Q̇(P = .20), V̇_E/MVV(P = .83), maximum HR percentages(P = .67) and dynamically hyperinflated to a similar degree(P = .37).

CONCLUSIONS

The Dyspnoea Challenge is correlated to different parameters of disease severity and produces a similar physiological and ED response to that of the 6MWT with the added benefit of being appropriate for longitudinal assessment of ED.

Diagnostic value of computed tomography-based pulmonary artery to aorta ratio measurement in chronic obstructive pulmonary disease with pulmonary hypertension: A systematic review and meta-analysis

OBJECTIVE

We conducted a meta-analysis to systematic assess the diagnostic value of computed tomography (CT)-based pulmonary artery to aorta (PA:A) ratio measurement in COPD with pulmonary hypertension (COPD-PH).

METHODS

Published studies referring to diagnostic accuracy of PA:A ratio for COPD-PH were screened out from PubMed, Embase, Web of science, China National Knowledge databases (CNKI), Wan fang databases, and VIP databases. We used bivariate random-effects model to estimate pooled sensitivity (SEN), specificity (SPE), positive and negative likelihood ratios (PLR and NLR, respectively), and diagnostic odds ratios (DOR). Summary receiver operating characteristic (SROC) curves and area under the curve (AUC) were also calculated to summarize the aggregate diagnostic performance.

RESULTS

Nine eligible studies were included and the pooled SEN was 69% (95% CI: 59 ~ 78), SPE was 85% (95% CI: 77 ~ 90), PLR was 4.5 (95% CI: 2.8 ~ 7.5), and NLR was 0.36 (95% CI: 0.26 ~ 0.51), respectively. DOR reached 13.00 (95% CI: 6.00 ~ 28.00), and value of AUC was 0.84 (95% CI: 0.81 ~ 0.87). Subgroup analysis indicated that when the value of PA:A ratio was equal or greater than one (PA/A ≥ 1), the combined SEN, SPE, AUC, and DOR was 69%, 89%, 0.90, and 19.65, respectively.

CONCLUSIONS

PA:A ratio is helpful for appraisal of COPD-PH, and PA/A ≥ 1 possessed prominent diagnostic accuracy.

Effects of Non-intubated Video-Assisted Thoracic Surgery on Patients With Pulmonary Dysfunction

Background: Non-intubated video-assisted thoracic surgery (NIVATS) can be safely performed in lung volume reduction surgery for patients with severe pulmonary dysfunction. However, there is still no cohort observation on the effects of NIVATS on patients with pulmonary dysfunction undergoing different types of thoracic procedures. This retrospective study aimed to observe the effects of NIVATS for this kind of patients.

Methods: Three hundred and twenty-eight patients with moderate to severe obstructive pulmonary dysfunction, who underwent video-assisted thoracic surgery (VATS), were retrospectively collected from June 1st, 2017 to September 30th, 2019. Patients in NIVATS were case-matched with those in intubated video-assisted thoracic surgery (IVATS) by a propensity score-matched analysis. The primary outcome was the comparison of perioperative values, the secondary outcome was the risk factors for postoperative clinical complications (PCP) which were identified by binary logistic regression analysis.

Results: After being matched, there were no differences in demographics and preoperative values of pulmonary function between NIVATS and IVATS groups. The duration of surgery and anesthesia had no difference (P = 0.091 and P = 0.467). As for the postoperative recovery, except for the mean intensive care unit (ICU) stay was longer in the IVATS group than in the NIVATS group (P = 0.015), the chest tube removal time and the postoperative hospital stay had no difference (P = 0.394 and P = 0.453), and the incidence of PCP also had no difference (P = 0.121). The binary logistic regression analysis revealed that the history of pulmonary disease, anesthesia method, and surgical location were risk factors of PCP.

Conclusion: For patients with pulmonary dysfunction when undergoing different types of thoracic procedures, the NIVATS can be performed as effectively and safely as the IVATS, and can reduce the ICU stay.

Exertional ventilation/carbon dioxide output relationship in COPD: from physiological mechanisms to clinical applications

There is well established evidence that the minute ventilation (V′_E)/carbon dioxide output (V′_CO2) relationship is relevant to a number of patient-related outcomes in COPD. In most circumstances, an increased V′_E/V′_CO2 reflects an enlarged physiological dead space (“wasted” ventilation), although alveolar hyperventilation (largely due to increased chemosensitivity) may play an adjunct role, particularly in patients with coexistent cardiovascular disease. The V′_E/V′_CO2 nadir, in particular, has been found to be an important predictor of dyspnoea and poor exercise tolerance, even in patients with largely preserved forced expiratory volume in 1 s. As the disease progresses, a high nadir might help to unravel the cause of disproportionate breathlessness. When analysed in association with measurements of dynamic inspiratory constraints, a high V′_E/V′_CO2 is valuable to ascertain a role for the “lungs” in limiting dyspnoeic patients. Regardless of disease severity, cardiocirculatory (heart failure and pulmonary hypertension) and respiratory (lung fibrosis) comorbidities can further increase V′_E/V′_CO2. A high V′_E/V′_CO2 is a predictor of poor outcome in lung resection surgery, adding value to resting lung hyperinflation in predicting all-cause and respiratory mortality across the spectrum of disease severity. Considering its potential usefulness, the V′_E/V′_CO2 should be valued in the clinical management of patients with COPD.

The minute ventilation/carbon dioxide production relationship is relevant to a number of patient-related outcomes in COPD. Minute ventilation/carbon dioxide production, therefore, should be valued in the clinical management of these patients.https://bit.ly/3df2upH

Sleep quality and architecture in COPD: the relationship with lung function abnormalities

OBJECTIVE

Impaired respiratory mechanics and gas exchange may contribute to sleep disturbance in patients with COPD. We aimed to assess putative associations of different domains of lung function (airflow limitation, lung volumes, and gas exchange efficiency) with polysomnography (PSG)-derived parameters of sleep quality and architecture in COPD.

METHODS

We retrospectively assessed data from COPD 181 patients ≥ 40 years of age who underwent spirometry, plethysmography, and overnight PSG. Univariate and multivariate linear regression models predicted sleep efficiency (total sleep time/total recording time) and other PSG-derived parameters that reflect sleep quality.

RESULTS

The severity of COPD was widely distributed in the sample (post-bronchodilator FEV1 ranging from 25% to 128% of predicted): mild COPD (40.3%), moderate COPD (43.1%), and severe-very severe COPD (16.6%). PSG unveiled a high proportion of obstructive sleep apnea (64.1%) and significant nocturnal desaturation (mean pulse oximetry nadir = 82.2% ± 6.9%). After controlling for age, sex, BMI, apnea-hypopnea index, nocturnal desaturation, comorbidities, and psychotropic drug prescription, FEV1/FVC was associated with sleep efficiency (β = 25.366; R2 = 14%; p < 0.001), whereas DLCO predicted sleep onset latency (β = -0.314; R2 = 13%; p < 0.001) and rapid eye movement sleep time/total sleep time in % (β = 0.085; R2 = 15%; p = 0.001).

CONCLUSIONS

Pulmonary function variables reflecting severity of airflow and gas exchange impairment, adjusted for some potential confounders, were weakly related to PSG outcomes in COPD patients. The direct contribution of the pathophysiological hallmarks of COPD to objectively measured parameters of sleep quality seems to be less important than it was previously assumed.

Exercise Capacity, Ventilatory Response, and Gas Exchange in COPD Patients With Mild to Severe Obstruction Residing at High Altitude

Background

Exercise intolerance, desaturation, and dyspnea are common features in patients with chronic obstructive pulmonary disease (COPD). At altitude, the barometric pressure (BP) decreases, and therefore the inspired oxygen pressure and the partial pressure of arterial oxygen (PaO₂) also decrease in healthy subjects and even more in patients with COPD. Most of the studies evaluating ventilation and arterial blood gas (ABG) during exercise in COPD patients have been conducted at sea level and in small populations of people ascending to high altitudes. Our objective was to compare exercise capacity, gas exchange, ventilatory alterations, and symptoms in COPD patients at the altitude of Bogotá (2,640 m), of all degrees of severity.

Methods

Measurement during a cardiopulmonary exercise test of oxygen consumption (VO₂), minute ventilation (VE), tidal volume (VT), heart rate (HR), ventilatory equivalents of CO₂ (VE/VCO₂), inspiratory capacity (IC), end-tidal carbon dioxide tension (PETCO₂), and ABG. For the comparison of the variables between the control subjects and the patients according to the GOLD stages, the non-parametric Kruskal–Wallis test or the one-way analysis of variance test was used.

Results

Eighty-one controls and 525 patients with COPD aged 67.5 ± 9.1 years were included. Compared with controls, COPD patients had lower VO₂ and VE (p < 0.001) and higher VE/VCO₂ (p = 0.001), A-aPO₂, and V_D/V_T (p < 0.001). In COPD patients, PaO₂ and saturation decreased, and delta IC (p = 0.004) and VT/IC increased (p = 0.002). These alterations were also seen in mild COPD and progressed with increasing severity of the obstruction.

Conclusion

The main findings of this study in COPD patients residing at high altitude were a progressive decrease in exercise capacity, increased dyspnea, dynamic hyperinflation, restrictive mechanical constraints, and gas exchange abnormalities during exercise, across GOLD stages 1–4. In patients with mild COPD, there were also lower exercise capacity and gas exchange alterations, with significant differences from controls. Compared with studies at sea level, because of the lower inspired oxygen pressure and the compensatory increase in ventilation, hypoxemia at rest and during exercise was more severe; PaCO₂ and PETCO₂ were lower; and VE/VO₂ was higher.

Pulmonary function with expiratory resistive loading in healthy volunteers

Expiratory flow limitation is a key characteristic in obstructive pulmonary diseases. To study abnormal lung mechanics isolated from heterogeneities of obstructive disease, we measured pulmonary function in healthy adults with expiratory loading. Thirty-seven volunteers (25±5 yr) completed spirometry and body plethysmography under control and threshold expiratory loading of 7, 11 cmH2O, and a subset at 20 cmH2O (n = 11). We analyzed the shape of the flow-volume relationship with rectangular area ratio (RAR; Ma et al., Respir Med 2010). Airway resistance was increased (p<0.0001) with 7 and 11 cmH2O loading vs control (9.20±1.02 and 11.76±1.68 vs. 2.53± 0.80 cmH2O/L/s). RAR was reduced (p = 0.0319) in loading vs control (0.45±0.07 and 0.47±0.09L vs. 0.48±0.08). FEV1 was reduced (p<0.0001) in loading vs control (3.24±0.81 and 3.23±0.80 vs. 4.04±1.05 L). FVC was reduced (p<0.0001) in loading vs control (4.11±1.01 and 4.14±1.03 vs. 5.03±1.34 L). Peak expiratory flow (PEF) was reduced (p<0.0001) in loading vs control (6.03±1.67 and 6.02±1.84 vs. 8.50±2.81 L/s). FEV1/FVC (p<0.0068) was not clinically significant and FRC (p = 0.4) was not different in loading vs control. Supra-physiologic loading at 20 cmH2O did not result in further limitation. Expiratory loading reduced FEV1, FVC, PEF, but there were no clinically meaningful differences in FEV1/FVC, FRC, or RAR. Imposed expiratory loading likely leads to high airway pressures that resist dynamic airway compression. Thus, a concave expiratory flow-volume relationship was consistently absent-a key limitation for model comparison with pulmonary function in COPD. Threshold loading may be a useful strategy to increase work of breathing or induce dynamic hyperinflation.

Pulmonary function testing in COPD: looking beyond the curtain of FEV1

Chronic obstructive pulmonary disease (COPD) management remains challenging due to the high heterogeneity of clinical symptoms and the complex pathophysiological basis of the disease. Airflow limitation, diagnosed by spirometry, remains the cornerstone of the diagnosis. However, the calculation of the forced expiratory volume in the first second (FEV1) alone, has limitations in uncovering the underlying complexity of the disease. Incorporating additional pulmonary function tests (PFTs) in the everyday clinical evaluation of COPD patients, like resting volume, capacity and airway resistance measurements, diffusion capacity measurements, forced oscillation technique, field and cardiopulmonary exercise testing and muscle strength evaluation, may prove essential in tailoring medical management to meet the needs of such a heterogeneous patient population. We aimed to provide a comprehensive overview of the available PFTs, which can be incorporated into the primary care physician's practice to enhance the efficiency of COPD management.

Clinical Interpretation of Cardiopulmonary Exercise Testing: Current Pitfalls and Limitations

Several shortcomings on cardiopulmonary exercise testing (CPET) interpretation have shed a negative light on the test as a clinically useful tool. For instance, the reader should recognize patterns of dysfunction based on clusters of variables rather than relying on rigid interpretative algorithms. Correct display of key graphical data is of foremost relevance: prolixity and redundancy should be avoided. Submaximal dyspnea ratings should be plotted as a function of work rate (WR) and ventilatory demand. Increased work of breathing and/or obesity may normalize peak oxygen uptake (V̇O₂) despite a low peak WR. Among the determinants of V̇O₂, only heart rate is measured during non-invasive CPET. It follows that in the absence of findings suggestive of severe impairment in O₂ delivery, the boundaries between inactivity and early cardiovascular disease are blurred in individual subjects. A preserved breathing reserve should not be viewed as evidence that "the lungs" are not limiting the subject. In this context, measurements of dynamic inspiratory capacity are key to uncover abnormalities germane to exertional dyspnea. A low end-tidal partial pressure for carbon dioxide may indicate either increased "wasted" ventilation or alveolar hyperventilation; thus, direct measurements of arterial (or arterialized) PO₂ might be warranted. Differentiating a chaotic breathing pattern from the normal breath-by-breath noise might be complex if the plotted data are not adequately smoothed. A sober recognition of these limitations, associated with an interpretation report free from technicalities and convoluted terminology, is crucial to enhance the credibility of CPET in the eyes of the practicing physician.

Intercept of minute ventilation versus carbon dioxide output relationship as an index of ventilatory inefficiency in chronic obstructive pulmonary disease

Background

Ventilatory inefficiency contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). The intercept of the minute ventilation (V^˙_E) vs. carbon dioxide output (V^˙ CO₂) plot is a key ventilatory inefficiency parameter. However, its relationships with lung hyperinflation (LH) and airflow limitation are not known. This study aimed to evaluate correlations between the V^˙_E/V^˙ CO₂ intercept and LH and airflow limitation to determine its physiological interpretation as an index of functional impairment in COPD.

Methods

We conducted a retrospective analysis of data from 53 COPD patients and 14 healthy controls who performed incremental cardiopulmonary exercise tests (CPETs) and resting pulmonary function assessment. Ventilatory inefficiency was represented by parameters reflecting the V^˙_E/V^˙ CO₂ nadir and slope (linear region) and the intercept of V^˙_E/V^˙ CO₂ plot. Their correlations with measures of LH and airflow limitation were evaluated.

Results

Compared to control, the slope (30.58±3.62, P<0.001) and intercept (4.85±1.11 L/min, P<0.05) were higher in COPD_stages1-2, leading to a higher nadir (31.47±4.47, P<0.01). Despite an even higher intercept in COPD_stages3-4 (7.16±1.41, P<0.001), the slope diminished with disease progression (from 30.58±3.62 in COPD_stages1-2 to 26.84±4.96 in COPD_stages3-4, P<0.01). There was no difference in nadir among COPD groups and higher intercepts across all stages. The intercept was correlated with peak V^˙_E/maximal voluntary ventilation (MVV) (r=0.489, P<0.001) and peak V^˙ O₂/Watt (r=0.354, P=0.003). The intercept was positively correlated with residual volume (RV) % predicted (r=0.571, P<0.001), RV/total lung capacity (TLC) (r=0.588, P<0.001), peak tidal volume (V_T)/FEV₁ (r=0.482, P<0.001) and negatively correlated with rest inspiratory capacity (IC)/TLC (r=−0.574, P<0.001), peak V_T/TLC (r=−0.585, P<0.001), airflow limitation forced expiratory volume in 1 s (FEV₁) % predicted (r=−0.606, P<0.001), and FEV₁/forced vital capacity (FVC) (r=−0.629, P<0.001).

Conclusions

V^˙_E/V^˙ CO₂ intercept was consistently correlated with worsening static and dynamic LH, pulmonary gas exchange, and airflow limitation in COPD. The V^˙_E/V^˙ CO₂ intercept emerged as a useful index of ventilatory inefficiency in COPD patients.

Systemic but not local rehydration restores dehydration-induced changes in pulmonary function in healthy adults

Water transport and local (airway) hydration are critical for the normal functioning of lungs and airways. Currently, there is uncertainty regarding the effects of systemic dehydration on pulmonary function. Our aims were 1) to clarify the impact of exercise- or fluid restriction-induced dehydration on pulmonary function in healthy adults; and 2) to establish whether systemic or local rehydration can reverse dehydration-induced alterations in pulmonary function. Ten healthy participants performed four experimental trials in a randomized order (2 h exercise in the heat twice and 28 h fluid restriction twice). Pulmonary function was assessed using spirometry and whole body plethysmography in the euhydrated, dehydrated, and rehydrated states. Oral fluid consumption was used for systemic rehydration and nebulized isotonic saline inhalation for local rehydration. Both exercise and fluid restriction induced mild dehydration (2.7 ± 0.7% and 2.5 ± 0.4% body mass loss, respectively; P < 0.001) and elevated plasma osmolality (P < 0.001). Dehydration across all four trials was accompanied by a reduction in forced vital capacity (152 ± 143 mL, P < 0.01) and concomitant increases in residual volume (216 ± 177 mL, P < 0.01) and functional residual capacity (130 ± 144 mL, P < 0.01), with no statistical differences between modes of dehydration. These changes were normalized by fluid consumption but not nebulization. Our results suggest that, in healthy adults: 1) mild systemic dehydration induced by exercise or fluid restriction leads to pulmonary function impairment, primarily localized to small airways; and 2) systemic, but not local, rehydration reverses these potentially deleterious alterations.NEW & NOTEWORTHY This study demonstrates that, in healthy adults, mild systemic dehydration induced by exercise in the heat or a prolonged period of fluid restriction leads to negative alterations in pulmonary function, primarily localized to small airways. Oral rehydration, but not nebulized isotonic saline, is able to restore pulmonary function in dehydrated individuals. Our findings highlight the importance of maintaining an adequate systemic fluid balance to preserve pulmonary function.

Ambient air pollution, lung function and COPD: cross-sectional analysis from the WHO Study of AGEing and adult health wave 1

BACKGROUND

Long-term exposure to ambient air pollution leads to respiratory morbidity and mortality; however, the evidence of the effect on lung function and chronic obstructive pulmonary disease (COPD) in older adult populations is inconsistent.

OBJECTIVE

To address this knowledge gap, we investigated the associations between particulate matter (PM), nitrogen dioxide (NO2) exposure and lung function, as well as COPD prevalence, in older Chinese adults.

METHODS

We used data from the WHO Study on global AGEing and adult health (SAGE) China Wave 1, which includes 111 693 participants from 64 townships in China. A cross-sectional analysis explored the association between satellite-based air pollution exposure estimates (PM with an aerodynamic diameter of ≤10 µm [PM10], ≤2.5 µm [PM2.5] and NO2) and forced expiratory volume in one second (FEV1), forced vital capacity (FVC), the FEV1/FVC ratio and COPD (defined as post-bronchodilator FEV1/FVC <70%). Data on lung function changes were further stratified by COPD status.

RESULTS

Higher exposure to each pollutant was associated with lower lung function. An IQR (26.1 µg/m3) increase in PM2.5 was associated with lower FEV1 (-71.88 mL, 95% CI -92.13 to -51.64) and FEV1/FVC (-2.81 mL, 95% CI -3.37 to -2.25). For NO2, an IQR increment of 26.8 µg/m3 was associated with decreases in FEV1 (-60.12 mL, 95% CI -84.00 to -36.23) and FVC (-32.33 mL, 95% CI -56.35 to -8.32). A 31.2 µg/m3 IQR increase in PM10 was linked to reduced FEV1 (-8.86 mL, 95% CI -5.40 to 23.11) and FEV1/FVC (-1.85 mL, 95% CI -2.24 to -1.46). These associations were stronger for participants with COPD. Also, COPD prevalence was linked to higher levels of PM2.5 (POR 1.35, 95% CI 1.26 to 1.43), PM10 (POR 1.24, 95% CI 1.18 to 1.29) and NO2 (POR 1.04, 95% CI 0.98 to 1.11).

CONCLUSION

Ambient air pollution was associated with lower lung function, especially in individuals with COPD, and increased COPD prevalence in older Chinese adults.

Lung Function Testing in Chronic Obstructive Pulmonary Disease

Lung function testing has undisputed value in the comprehensive assessment and individualized management of chronic obstructive pulmonary disease, a pathologic condition in which a functional abnormality, poorly reversible expiratory airway obstruction, is at the core of its definition. After an overview of the physiologic underpinnings of the disease, the authors outline the role of lung function testing in this disease, including diagnosis, assessment of severity, and indication for and responses to pharmacologic and nonpharmacologic interventions. They discuss the current controversies surrounding test interpretation with these purposes in mind and provide balanced recommendations to optimize their usefulness in different clinical scenarios.

Heart, lungs, and muscle interplay in worsening activity-related breathlessness in advanced cardiopulmonary disease

PURPOSE OF REVIEW

Activity-related breathlessness is a key determinant of poor quality of life in patients with advanced cardiorespiratory disease. Accordingly, palliative care has assumed a prominent role in their care. The severity of breathlessness depends on a complex combination of negative cardiopulmonary interactions and increased afferent stimulation from systemic sources. We review recent data exposing the seeds and consequences of these abnormalities in combined heart failure and chronic obstructive pulmonary disease (COPD).

RECENT FINDINGS

The drive to breathe increases ('excessive breathing') secondary to an enlarged dead space and hypoxemia (largely COPD-related) and heightened afferent stimuli, for example, sympathetic overexcitation, muscle ergorreceptor activation, and anaerobic metabolism (largely heart failure-related). Increased ventilatory drive might not be fully translated into the expected lung-chest wall displacement because of the mechanical derangements brought by COPD ('inappropriate breathing'). The latter abnormalities, in turn, negatively affect the central hemodynamics which are already compromised by heart failure. Physical activity then decreases, worsening muscle atrophy and dysfunction.

SUMMARY

Beyond the imperative of optimal pharmacological treatment of each disease, strategies to lessen ventilation (e.g., walking aids, oxygen, opiates and anxiolytics, and cardiopulmonary rehabilitation) and improve mechanics (heliox, noninvasive ventilation, and inspiratory muscle training) might mitigate the burden of this devastating symptom in advanced heart failure-COPD.

Peculiarities of Autonomic Regulation of the Heart in Experimental Normobaric Hypoxia of Different Genesis

We compared autonomic regulation of the heart in Wistar rats with acute exogenous hypoxic and chronic normobaric hypoxia against the background of experimental chronic obstructive pulmonary disease. In animals subjected to normobaric hypoxia, dysfunction of the autonomic regulation of the heart developed; it manifested in a significant limitation of the effects of the parasympathetic and sympathetic nervous systems on the pacemaker activity of the sinoatrial node. Disturbances in autonomic regulation of the heart in acute exogenous hypoxic normobaric hypoxia were characterized by "rigid" heart rhythm and bradycardia in the presence of systolic-diastolic arterial hypotension. Centralization of heart rhythm control did not provide compensation for hemodynamic disturbances. In case of chronic normobaric hypoxia, an increase in arterial hypoxemia was associated with protective "denervation" of the heart against the background of increased activity of the humoral regulation, which manifested in tachycardia, isolated systolic arterial hypertension, and overstrain of regulatory systems.

Are the “critical” inspiratory constraints actually decisive to limit exercise tolerance in COPD?

Exercise intolerance is characteristically multi-factorial in patients with chronic obstructive pulmonary disease (COPD) [1]. At least in symptomatic patients with moderate-to-severe airflow limitation, higher operating lung volumes assume a relevant role in decreasing patients’ tolerance to sustain “prolonged” exercise. As a consequence of the dynamic increase in the end-expiratory lung volume, tidal volume (VT) occurs close to total lung capacity (TLC), thereby reducing the room for further lung–chest wall expansion. The combination of low dynamic lung compliance and a severely reduced inspiratory reserve volume causes a mismatch between a growing respiratory neural drive and the resulting lung–chest wall displacement [2]. It has been postulated that such critical inspiratory constraints (CIC) lead to a plateau in VT, and a concomitant increase in dyspnoea as a function of ventilation (V′_E) [3]. Accordingly, patients change their perception of the uncomfortable respiratory sensations from “laboured breathing” to “insufficient inspiration”, prompting early exercise termination [4].

The concept of critical inspiratory constraints is key to the modern understanding of exercise pathophysiology in patients with moderate-to-severe COPDhttps://bit.ly/2A6bCxD

Interventions for promoting physical activity in people with chronic obstructive pulmonary disease (COPD)

BACKGROUND

Escalating awareness of the magnitude of the challenge posed by low levels of physical activity in people with chronic obstructive pulmonary disease (COPD) highlights the need for interventions to increase physical activity participation. The widely-accepted benefits of physical activity, coupled with the increasing availability of wearable monitoring devices to objectively measure participation, has led to a dramatic rise in the number and variety of studies that aimed to improve the physical activity of people with COPD. However, little was known about the relative efficacy of interventions tested so far.

OBJECTIVES

In people with COPD, which interventions are effective at improving objectively-assessed physical activity?

SEARCH METHODS

We identified trials from the Cochrane Airways Trials Register Register, which contains records identified from bibliographic databases including the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, CINAHL, AMED, and PsycINFO. We also searched PEDro, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform portal and the Australian New Zealand Clinical Trials Registry (from inception to June 2019). We checked reference lists of all primary studies and review articles for additional references, as well as respiratory journals and respiratory meeting abstracts, to identify relevant studies.

SELECTION CRITERIA

We included randomised controlled trials of interventions that used objective measures for the assessment of physical activity in people with COPD. Trials compared an intervention with no intervention or a sham/placebo intervention, an intervention in addition to another standard intervention common to both groups, or two different interventions.

DATA COLLECTION AND ANALYSIS

We used standard methods recommended by Cochrane. Subgroup analyses were possible for supervised compared to unsupervised pulmonary rehabilitation programmes in clinically-stable COPD for a range of physical activity outcomes. Secondary outcomes were health-related quality of life, exercise capacity, adverse events and adherence. Insufficient data were available to perform prespecified subgroup analyses by duration of intervention or disease severity. We undertook sensitivity analyses by removing studies that were at high or unclear risk of bias for the domains of blinding and incomplete outcome data.

MAIN RESULTS

We included 76 studies with 8018 participants. Most studies were funded by government bodies, although some were sponsored by equipment or drug manufacturers. Only 38 studies had physical activity as a primary outcome. A diverse range of interventions have been assessed, primarily in single studies, but improvements have not been systematically demonstrated following any particular interventions. Where improvements were demonstrated, results were confined to single studies, or data for maintained improvement were not provided. Step count was the most frequently reported outcome, but it was commonly assessed using devices with documented inaccuracy for this variable. Compared to no intervention, the mean difference (MD) in time in moderate- to vigorous-intensity physical activity (MVPA) following pulmonary rehabilitation was four minutes per day (95% confidence interval (CI) -2 to 9; 3 studies, 190 participants; low-certainty evidence). An improvement was demonstrated following high-intensity interval exercise training (6 minutes per day, 95% CI 4 to 8; 2 studies, 275 participants; moderate-certainty evidence). One study demonstrated an improvement following six months of physical activity counselling (MD 11 minutes per day, 95% CI 7 to 15; 1 study, 280 participants; moderate-certainty evidence), but we found mixed results for the addition of physical activity counselling to pulmonary rehabilitation. There was an improvement following three to four weeks of pharmacological treatment with long-acting muscarinic antagonist and long-acting beta2-agonist (LAMA/LABA) compared to placebo (MD 10 minutes per day, 95% CI 4 to 15; 2 studies, 423 participants; high-certainty evidence). These interventions also demonstrated improvements in other measures of physical activity. Other interventions included self-management strategies, nutritional supplementation, supplemental oxygen, endobronchial valve surgery, non-invasive ventilation, neuromuscular electrical stimulation and inspiratory muscle training.

AUTHORS' CONCLUSIONS

A diverse range of interventions have been assessed, primarily in single studies. Improvements in physical activity have not been systematically demonstrated following any particular intervention. There was limited evidence for improvement in physical activity with strategies including exercise training, physical activity counselling and pharmacological management. The optimal timing, components, duration and models for interventions are still unclear. Assessment of quality was limited by a lack of methodological detail. There was scant evidence for a continued effect over time following completion of interventions, a likely requirement for meaningful health benefits for people with COPD.

Clinical and Physiologic Implications of Negative Cardiopulmonary Interactions in Coexisting Chronic Obstructive Pulmonary Disease-Heart Failure

Chronic obstructive pulmonary disease (COPD) and heart failure with reduced ejection fraction (HF) frequently coexist in the elderly. Expiratory flow limitation and lung hyperinflation due to COPD may adversely affect central hemodynamics in HF. Low lung compliance, increased alveolar-capillary membrane thickness, and abnormalities in pulmonary perfusion because of HF further deteriorates lung function in COPD. We discuss how those negative cardiopulmonary interactions create challenges in clinical interpretation of pulmonary function and cardiopulmonary exercise tests in coexisting COPD-HF. In the light of physiologic concepts, we also discuss the influence of COPD or HF on the current medical treatment of each disease.

Effects of high- and moderate-intensity exercise on central hemodynamic and oxygen uptake recovery kinetics in CHF-COPD overlap

The oxygen uptake (V˙O₂) kinetics during onset of and recovery from exercise have been shown to provide valuable parameters regarding functional capacity of both chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) patients. To investigate the influence of comorbidity of COPD in patients with CHF with reduced ejection fraction on recovery from submaximal exercise, 9 CHF-COPD male patients and 10 age-, gender-, and left ventricle ejection fraction (LVEF)-matched CHF patients underwent constant-load exercise tests (CLET) at moderate and high loads. The V˙O₂, heart rate (HR), and cardiac output (CO) recovery kinetics were determined for the monoexponential relationship between these variables and time. Within-group analysis showed that the recovery time constant of HR (P<0.05, d=1.19 for CHF and 0.85 for CHF-COPD) and CO (P<0.05, d=1.68 for CHF and 0.69 for CHF-COPD) and the mean response time (MRT) of CO (P<0.05, d=1.84 for CHF and 0.73 for CHF-COPD) were slower when moderate and high loads were compared. CHF-COPD patients showed smaller amplitude of CO recovery kinetics (P<0.05) for both moderate (d=2.15) and high (d=1.07) CLET. Although the recovery time constant and MRT means were greater in CHF-COPD, CHF and CHF-COPD groups were not differently affected by load (P>0.05 in group vs load analysis). The ventilatory efficiency was related to MRT of V˙O₂ during high CLET (r=0.71). Our results suggested that the combination of CHF and COPD may further impair the recovery kinetics compared to CHF alone.

Antidiabetic Effects of Bisamide Derivative of Dicarboxylic Acid in Metabolic Disorders

In clinical practice, the metabolic syndrome can lead to multiple complications, including diabetes. It remains unclear which component of the metabolic syndrome (obesity, inflammation, hyperglycemia, or insulin resistance) has the strongest inhibitory effect on stem cells involved in beta cell regeneration. This makes it challenging to develop effective treatment options for complications such as diabetes. In our study, experiments were performed on male C57BL/6 mice where metabolic disorders have been introduced experimentally by a combination of streptozotocin-treatment and a high-fat diet. We evaluated the biological effects of Bisamide Derivative of Dicarboxylic Acid (BDDA) and its impact on pancreatic stem cells in vivo. To assess the impact of BDDA, we applied a combination of histological and biochemical methods along with a cytometric analysis of stem cell and progenitor cell markers. We show that in mice with metabolic disorders, BDDA has a positive effect on lipid and glucose metabolism. The pancreatic restoration was associated with a decrease of the inhibitory effects of inflammation and obesity factors on pancreatic stem cells. Our data shows that BDDA increases the number of pancreatic stem cells. Thus, BDDA could be used as a new compound for treating complication of the metabolic syndrome such as diabetes.

Determinants of the diminished exercise capacity in patients with chronic obstructive pulmonary disease: looking beyond the lungs

KEY POINTS

Peak oxygen uptake, a primary determinant of prognosis, mortality and quality of life, is diminished in patients with chronic obstructive pulmonary disease (COPD), with mounting evidence supporting an important role for peripheral dysfunction, particularly within skeletal muscle. In patients with severe COPD and activity-matched controls, muscle oxygen transport and utilization were assessed at peak effort during single-leg knee-extensor exercise (KE), where ventilation is assumed to be submaximal. This strategy removes ventilation as the major constraint to exercise capacity in COPD, allowing maximal muscle function to be attained and evaluated. During maximal KE, both convective arterial oxygen delivery to the skeletal muscle microvasculature and subsequent diffusive oxygen delivery to the mitochondria were diminished in patients with COPD compared to control subjects. These findings emphasize the importance of factors, beyond the lungs, that influence exercise capacity in this patient population and may, ultimately, influence the prognosis, mortality and quality of life for patients with COPD.

ABSTRACT

Peak oxygen uptake ( V ̇ O 2 peak ), a primary determinant of prognosis, mortality and quality of life, is diminished in patients with chronic obstructive pulmonary disease (COPD). Mounting evidence supports an important role of the periphery, particularly skeletal muscle, in the diminished V ̇ O 2 peak with COPD. However, the peripheral determinants of V ̇ O 2 peak have not been comprehensively assessed in this cohort. Thus, the hypothesis was tested that both muscle convective and diffusive oxygen (O2 ) transport, and therefore skeletal muscle peak O2 uptake ( V ̇ M O 2 peak ), are diminished in patients with COPD compared to matched healthy controls, even when ventilatory limitations (i.e. attainment of maximal ventilation) are minimized by using small muscle mass exercise. Muscle O2 transport and utilization were assessed at peak exercise from femoral arterial and venous blood samples and leg blood flow (by thermodilution) in eight patients with severe COPD (forced expiratory volume in 1s (FEV1 ) ± SEM = 0.9 ± 0.1 l, 30% of predicted) and eight controls during single-leg knee-extensor exercise. Both muscle convective O2 delivery (0.44 ± 0.06 vs. 0.69 ± 0.07 l min-1 , P < 0.05) and muscle diffusive O2 conductance (6.6 ± 0.8 vs. 10.4 ± 0.9 ml min-1  mmHg-1 , P < 0.05) were ∼1/3 lower in patients with COPD than controls, resulting in an attenuated V ̇ M O 2 peak in the patients (0.27 ± 0.04 vs. 0.42 ± 0.05 l min-1 , P < 0.05). When cardiopulmonary limitations to exercise are minimized, the convective and diffusive determinants of V ̇ M O 2 peak , at the level of the skeletal muscle, are greatly attenuated in patients with COPD. These findings emphasize the importance of factors, beyond the lungs, that may ultimately influence this population's prognosis, mortality and quality of life.

An update on pulmonary rehabilitation techniques for patients with chronic obstructive pulmonary disease

Introduction: Pulmonary rehabilitation (PR) is one of the core components in the management of patients with chronic obstructive pulmonary disease (COPD). In order to achieve the maximal level of independence, autonomy, and functioning of the patient, targeted therapies and interventions based on the identification of physical, emotional and social traits need to be provided by a dedicated, interdisciplinary PR team.Areas covered: The review discusses cardiopulmonary exercise testing in the selection of different modes of training modalities. Neuromuscular electrical stimulation as well as gait assessment and training are discussed as well as add-on therapies as oxygen, noninvasive ventilator support or endoscopic lung volume reduction in selected patients. The potentials of pulsed inhaled nitric oxide in patients with underlying pulmonary hypertension is explored as well as nutritional support. The impact of sleep quality on outcomes of PR is reviewed.Expert opinion: Individualized, comprehensive intervention based on thorough assessment of physical, emotional, and social traits in COPD patients forms a continuous challenge for health-care professionals and PR organizations in order to dynamically implement and adapt these strategies based on dynamic, more optimal understanding of underlying pathophysiological mechanisms.

Factors Contributing to CO Uptake and Elimination in the Body: A Critical Review

BACKGROUND

Carbon monoxide (CO) poisoning is an important public health issue around the world. Research indicates that many factors may be related to the rate of CO uptake and elimination in the human body. However, some factors related to CO uptake and elimination are considered controversial. Relatively little attention has been devoted to review and synthesis of factors affecting CO uptake and elimination.

PURPOSE

This paper provides a critical scoping review of the factors and divides them into four aspects, including environmental, demographic, physiological and treatment factors.

METHODS

We searched the scientific databases for research that has proposed a mathematical equation as a synthesis of quantities related to CO poisoning, CO elimination, CO uptake, CO half-life, CO uptake and elimination and their relationships. After excluding the studies that did not meet the study criteria, there were 39 studies included in the review and the search was completed before 16 December 2019.

RESULTS AND CONCLUSION

This review discusses most of the factors that impact the rate of CO uptake and elimination. Several factors may be related to CO uptake and elimination, such as CO concentration, the duration of exposure to CO, age, sex, exercise, minute ventilation, alveolar ventilation, total haemoglobin mass and different treatments for CO poisoning. Although some potential factors were not included in the review, the findings are useful by presenting an overview for discussing factors affecting CO uptake and elimination and provide a starting point for further study regarding strategies for CO poisoning and the environmental standard of CO.

Effects of lung deflation induced by tiotropium/olodaterol on the cardiocirculatory responses to exertion in COPD

BACKGROUND

Hyperinflation has been associated with negative cardiocirculatory consequences in patients with chronic obstructive pulmonary disease (COPD). These abnormalities are likely to worsen when the demands for O₂ increase, e.g., under the stress of exercise. Thus, pharmacologically-induced lung deflation may improve cardiopulmonary interactions and exertional cardiac output leading to higher limb muscle blood flow and oxygenation in hyperinflated patients with COPD.

METHODS

20 patients (residual volume = 201.6 ± 63.6% predicted) performed endurance cardiopulmonary exercise tests (75% peak) 1 h after placebo or tiotropium/olodaterol 5/5 μg via the Respimat® inhaler (Boehringer Ingelheim, Ingelheim am Rhein, Germany). Cardiac output was assessed by signal-morphology impedance cardiography. Near-infrared spectroscopy determined quadriceps blood flow (indocyanine green dye) and intra-muscular oxygenation.

RESULTS

Tiotropium/olodaterol was associated with marked lung deflation (p < 0.01): residual volume decreased by at least 0.4 L in 14/20 patients (70%). The downward shift in the resting static lung volumes was associated with less exertional inspiratory constraints and dyspnoea thereby increasing exercise endurance by ~50%. Contrary to our premises, however, neither central and peripheral hemodynamics nor muscle oxygenation improved after active intervention compared to placebo. These results were consistent with those found in a subgroup of patients showing the largest decrements in residual volume (p < 0.05).

CONCLUSIONS

The beneficial effects of tiotropium/olodaterol on resting and operating lung volumes are not translated into enhanced cardiocirculatory responses to exertion in hyperinflated patients with COPD. Improvement in exercise tolerance after dual bronchodilation is unlikely to be mechanistically linked to higher muscle blood flow and/or O₂ delivery.

Respiratory muscles dysfunction and respiratory diseases

This review presents an analysis of the literature on the topic of respiratory muscle (RM) dysfunction in various forms of respiratory pathology: chronic obstructive pulmonary disease (COPD), asthma, community-acquired pneumonia, idiopathic pulmonary fibrosis (IPF), sarcoidosis and interstitial lung diseases (ILD), associated with systemic connective tissue diseases (polymyositis, dermatomyositis and systemic lupus erythematosus - SLE). Various clinical and pathophysiological aspects of RM dysfunction and general patterns of its pathogenesis were examined. It was proved that the role of RM in the development of respiratory failure depends on the form and stage of the pulmonary pathology and the severity of systemic manifestations of these diseases: excessive proteolysis, oxidative stress, hypoxia, chronic systemic inflammation. These factors modify the morphofunctional status of RM, worsens their contractile function, which is contributed to the development of respiratory failure. In some cases, the primary weakness of RM precedes the clinical manifestation of pulmonary pathology, which is distinctive for some variants of myositis-associated ILD and SLE. Endogenous intoxication syndrome plays a significant role in the development of RM dysfunction during community-acquired pneumonia. It is noted that sarcoid pulmonary ventilation disorders associate with the RM weakness, but not with the degree of lung damage. In most cases, secondary RM dysfunction predominates that contributes to respiratory failure progression, which is especially noticeable in case of COPD, asthma and IPF.

Patient assessment and selection for pulmonary rehabilitation

Pulmonary rehabilitation (PR) is beneficial for people with several forms of chronic respiratory disease. Given the existing limitations on availability of PR services, it is important to identify participants who are most likely to benefit from it. Identification of criteria for patient referral to PR is challenging, as chronic respiratory diseases and their medical and psychosocial co-morbidities place a complex and multifaceted burden on patients. Although research studies have attempted to identify key parameters predictive of 'responsiveness to PR', to date no firm physiological, psychosocial or other criteria exist by which optimal patient candidacy can be determined. Moreover, individual factors do not reliably predict successful multidimensional PR outcomes. In general, individuals who remain symptomatic with dyspnoea, fatigue and exercise intolerance; who have difficulty performing activities of daily living (ADL); and who are having difficulty coping with or managing their disease despite optimized pharmacological therapy are potential candidates for PR. Patient assessment and outcome measurement are core essential features of PR. To be considered as a PR programme, rehabilitation programmes must demonstrate, at a minimum, assessment and outcome measurement in regard to exercise capacity, dyspnoea and health-related quality of life. Additional parameters, including physical activity, nutritional status, tobacco use status, patient knowledge and self-efficacy, performance of ADL, fatigue, disease exacerbations, hospitalizations and other urgent healthcare utilization, and behavioural outcomes, including coping styles, patient satisfaction and programme metrics, are other relevant and important aspects of patient assessment and outcome measurement that should be considered and undertaken in PR, where feasible.

Does oxygen pulse trajectory during incremental exercise discriminate impaired oxygen delivery from poor muscle oxygen utilisation?

Cardiopulmonary exercise testing (CPET) is often helpful to shed light on the mechanisms of exercise intolerance in different clinical populations. Although specific response patterns are rarely pathognomonic, an integrative approach considering metabolic and mechanical–ventilatory responses in addition to limiting symptoms has been valuable to guide further investigations [1].

A flattened or decreasing O₂ pulse trajectory during incremental CPET is commonly found in patents with low exercise stroke volume but not in those with severely impaired muscle O₂ utilisation. This finding should prompt additional cardiovascular work-up.http://bit.ly/2HRE739

New insights into early intervention of chronic obstructive pulmonary disease with mild airflow limitation

Chronic obstructive pulmonary disease (COPD) has become one of the major public health problems worldwide due to its high morbidity and mortality. Up until now, COPD is still under-diagnosed and under-treated, especially for mild or moderate patients. It is widely accepted that the majority of patients with COPD are in the early stages, yet this subpopulation is underestimated. In recent years, growing evidence indicates that substantial physiological and clinical abnormalities exist in patients with mild COPD compared with healthy controls. Furthermore, recent studies suggest that pharmacologic intervention in early COPD has the potential to alter clinical outcomes. The main objective of this review is to summarize recent research regarding the heterogeneous pathophysiology, clinical features, and treatment of mild and moderate COPD. We also discuss promising markers of disease progression, which may contribute to the development of precision medicine in early COPD.

Effects of bi-level positive airway pressure on ventilatory and perceptual responses to exercise in comorbid heart failure-COPD

This study tested the hypothesis that, by increasing the volume available for tidal expansion (inspiratory capacity, IC), bi-level positive airway pressure (BiPAP™) would lead to greater beneficial effects on dyspnea and exercise intolerance in comorbid heart failure (HF)-chronic obstructive pulmonary disease (COPD) than HF alone. Ten patients with HF and 9 with HF-COPD (ejection fraction = 30 ± 6% and 35 ± 7%; FEV₁ = 83 ± 12% and 65 ± 15% predicted, respectively) performed a discontinuous exercise protocol under sham ventilation or BiPAP™. Time to intolerance increased with BiPAP™ only in HF-COPD (p < 0.05). BiPAP™ led to higher tidal volume and lower duty cycle with longer expiratory time (p < 0.05). Of note, BiPAP™ improved IC (by ∼0.5 l) across exercise intensities only in HF-COPD. These beneficial consequences were associated with lower dyspnea scores at higher levels of ventilation (p < 0.05). By improving the qualitative" (breathing pattern and operational lung volumes) and sensory (dyspnea) features of exertional ventilation, BiPAP™ might allow higher exercise intensities to be sustained for longer during cardiopulmonary rehabilitation in HF-COPD.

Exercise intolerance in comorbid COPD and heart failure: the role of impaired aerobic function

Impaired aerobic function is a potential mechanism of exercise intolerance in patients with combined cardiorespiratory disease. We investigated the pathophysiological and sensory consequences of a low change in oxygen uptake (ΔV'_O2 )/change in work rate (ΔWR) relationship during incremental exercise in patients with coexisting chronic obstructive pulmonary disease (COPD) and systolic heart failure (HF).After clinical stabilisation, 51 COPD-HF patients performed an incremental cardiopulmonary exercise test to symptom limitation. Cardiac output was non-invasively measured (impedance cardiography) in a subset of patients (n=18).27 patients presented with ΔV'_O2 /ΔWR below the lower limit of normal. Despite similar forced expiratory volume in 1 s and ejection fraction, the low ΔV'_O2 /ΔWR group showed higher end-diastolic volume, lower inspiratory capacity and lower transfer factor compared to their counterparts (p<0.05). Peak WR and peak V'_O2 were ∼15% and ∼30% lower, respectively, in the former group: those findings were associated with greater symptom burden in daily life and at a given exercise intensity (leg discomfort and dyspnoea). The low ΔV'_O2 /ΔWR group presented with other evidences of impaired aerobic function (sluggish V'_O2 kinetics, earlier anaerobic threshold) and cardiocirculatory performance (lower oxygen pulse, lower stroke volume and cardiac output) (p<0.05). Despite similar exertional hypoxaemia, they showed worse ventilatory inefficiency and higher operating lung volumes, which led to greater mechanical inspiratory constraints (p<0.05).Impaired aerobic function due to negative cardiopulmonary-muscular interactions is an important determinant of exercise intolerance in patients with COPD-HF. Treatment strategies to improve oxygen delivery to and/or utilisation by the peripheral muscles might prove particularly beneficial to these patients.

ERS statement on respiratory muscle testing at rest and during exercise

Assessing respiratory mechanics and muscle function is critical for both clinical practice and research purposes. Several methodological developments over the past two decades have enhanced our understanding of respiratory muscle function and responses to interventions across the spectrum of health and disease. They are especially useful in diagnosing, phenotyping and assessing treatment efficacy in patients with respiratory symptoms and neuromuscular diseases. Considerable research has been undertaken over the past 17 years, since the publication of the previous American Thoracic Society (ATS)/European Respiratory Society (ERS) statement on respiratory muscle testing in 2002. Key advances have been made in the field of mechanics of breathing, respiratory muscle neurophysiology (electromyography, electroencephalography and transcranial magnetic stimulation) and on respiratory muscle imaging (ultrasound, optoelectronic plethysmography and structured light plethysmography). Accordingly, this ERS task force reviewed the field of respiratory muscle testing in health and disease, with particular reference to data obtained since the previous ATS/ERS statement. It summarises the most recent scientific and methodological developments regarding respiratory mechanics and respiratory muscle assessment by addressing the validity, precision, reproducibility, prognostic value and responsiveness to interventions of various methods. A particular emphasis is placed on assessment during exercise, which is a useful condition to stress the respiratory system.

[Delayed diagnosis is associated with greater disease severity of chronic obstructive pulmonary disease]

OBJECTIVE

To investigate the association of the time of initial diagnosis with the severity of chronic obstructive pulmonary disease (COPD).

METHODS

A total of 803 patients who were diagnosed to have COPD for the first time in our hospital between May 2015 to February 2018 were enrolled in this study.The diagnoses of COPD and asthma COPD overlap (ACO) were made according GOLD guidelines and european consensus definition.Lung function of the patients was graded according to the GOLD guidelines.

RESULTS

The patients with COPD had a mean age of 61.8±9.9 years,including 726 male and 77 female patients.The course of the patients (defined as the time from symptom onset to the establishment of a diagnosis) was 3(0.5,8) years.Among these patients,85.2% had a moderate disease severity (FEV1%&lt;80%),and 48.3% had severe or very severe conditions (FEV1%&lt;50%);47.0% of them were positive for bronchial dilation test.In the overall patients,295(36.7%) were also diagnosed to have ACO,and the mean disease course of ACO[3(1,9) years]was similar to that of COPD[3(0.5,8) years](P&gt;0.05).A significant correlation was found between the disease course and the lung function of the patients.Multiple linear regression analysis showed that an older age and a longer disease course were associated with poorer lung functions and a greater disease severity.

CONCLUSIONS

The delay of the initial diagnosis is significantly related to the severity of COPD.