Exercise-induced Oxygen Desaturation Research Articles

Test-retest Repeatability and Minimal Detectable Change of 1-minute Sit-to-Stand Test for the Ability to Detect Exercise-induced Oxygen Desaturation in Patients with Interstitial Lung Diseases

Test-retest Repeatability and Minimal Detectable Change of 1-minute Sit-to-Stand Test for the Ability to Detect Exercise-induced Oxygen Desaturation in Patients with Interstitial Lung Diseases

HLA-G14-bp variant is associated with exercise-induced oxygen desaturation in the post-COVID-19 condition

<i>HLA-G</i>14-bp variant is associated with exercise-induced oxygen desaturation in the post-COVID-19 condition

The Utility Of 1-Minute Sit-To-Stand Test to Detect Exercise-Induced Oxygen Desaturation in Outpatient Assessment of Post COVID-19 Patients

The Utility Of 1-Minute Sit-To-Stand Test to Detect Exercise-Induced Oxygen Desaturation in Outpatient Assessment of Post COVID-19 Patients

Os testes do degrau são viáveis, seguros e podem ser utilizados para avaliar a capacidade de exercício no domicílio após hospitalização por COVID-19

Abstract Introduction: Step-based tests are commonly utilized to assess the exercise capacity of individuals with respiratory diseases. However, the feasibility and safety of the step tests have not yet been studied in individuals after COVID-19. Objective: To investigate the feasibility and safety of the six-minute step test (6MST) and the modified incremental step test (MIST) in assessing exercise capacity at home in individuals after hospitalization for COVID-19, and to identify factors associated with performance in these tests. Methods: Cross-sectional multicenter study with individuals hospitalized for COVID-19 fifteen days after hospital discharge. Participants performed spirometry, 6MST, and MIST during a single home visit. Adverse events were registered during and immediately after the tests. Results: Sixty-five participants were studied (50 ± 10 years old, 55% male). The feasibility was 96.9% and the incidence of adverse events was 13.8% in 6MST and 6.2% in MIST. The individuals performed 76.9% of the predicted on the 6MST, with 40% of the participants reaching 80% of the maximum HR and 31% presenting exercise-induced oxygen desaturation. In the MIST, the individuals performed 20% of the predicted, 23% of the participants reached 80% of the maximum heart rate, and 17% presented exercise-induced oxy-gen desaturation. Length of hospital stay and the use of mechanical ventilation were associated with test performance. Conclusion: 6MST and MIST are feasible, safe, and can be used to assess exercise capacity in a home environment in individuals after hospitalization for COVID-19. The performance in these tests was associated with a prolonged hospital stay and the use of mechanical ventilation.

Do cardiopulmonary exercise tests predict summit success and acute mountain sickness? A prospective observational field study at extreme altitude

ObjectiveDuring a high-altitude expedition, the association of cardiopulmonary exercise testing (CPET) parameters with the risk of developing acute mountain sickness (AMS) and the chance of reaching the summit were investigated.MethodsThirty-nine...

Prescribing and adjusting exercise training in chronic respiratory diseases – Expert-based practical recommendations

BackgroundInternational guidelines recommend endurance (ET) and strength training (ST) in patients with chronic respiratory diseases (CRDs), but only provide rough guidance on how to set the initial training load. This may unintentionally lead to practice variation and inadequate training load adjustments. This study aimed to develop practical recommendations on tailoring ET and ST based on practices from international experts from the field of exercise training in CRDs. Methods35 experts were invited to address a 64-item online survey about how they prescribe and adjust exercise training. ResultsCycling (97%) and walking (86%) were the most commonly implemented ET modalities. Continuous endurance training (CET, 83%) and interval endurance training (IET, 86%) were the frequently applied ET types. Criteria to prescribe IET instead of CET were: patients do not tolerate CET due to dyspnoea at the initial training session (79%), intense breathlessness during initial exercise assessment (76%), and/or profound exercise-induced oxygen desaturation (59%). For ST, most experts (68%) recommend 3 sets per exercise; 62% of experts set the intensity at a specific load that patients can tolerate for a range of 8 to 15 repetitions per set. Also, 56% of experts advise patients to approach local muscular exhaustion at the end of a single ST set. ConclusionsThe experts´ practices were summarized to develop practical recommendations in the form of flowcharts on how experts apply and adjust CET, IET, and ST in patients with CRDs. These recommendations may guide health care professionals to optimize exercise training programs in patients with CRDs.

Association of air pollution exposure with exercise-induced oxygen desaturation in COPD

BackgroundThere is a link between exposure to air pollution and the increased prevalence of chronic obstructive pulmonary disease (COPD) and declining pulmonary function, but the association with O2 desaturation during exercise in COPD patients with emphysema is unclear. Our aims were to estimate the prevalence of O2 desaturation during exercise in patients with COPD, and determine the association of exposure to air pollution with exercise-induced desaturation (EID), the degree of emphysema, and dynamic hyperinflation (DH).MethodsWe assessed the effects of 10-year prior to the HRCT assessment and 7 days prior to the six-minute walking test exposure to particulate matter with an aerodynamic diameter of < 10 µm (PM10) or of < 2.5 µM (PM2.5), nitrogen dioxide (NO2), and ozone (O3) in patients with emphysema in this retrospective cohort study. EID was defined as a nadir standard pulse oximetry (SpO2) level of < 90% or a delta (△)SpO2 level of ≥ 4%. Ambient air pollutant (PM2.5, PM10, O3, and NO2) data were obtained from Taiwan Environmental Protection Administration (EPA) air-monitoring stations, usually within 10 km to each participant’s home address.ResultsWe recruited 141 subjects with emphysema. 41.1% of patients with emphysema exhibited EID, and patients with EID had more dyspnea, worse lung function, more severe emphysema, more frequent acute exacerbations, managed a shorter walking distance, had DH, and greater long-term exposure to air pollution than those without EID. We observed that levels of 10-year concentrations of PM10, PM2.5, and NO2 were significantly associated with EID, PM10 and PM2.5 were associated with the severity of emphysema, and associated with DH in patients with emphysema. In contrast, short-term exposure did not have any effect on patients.ConclusionLong-term exposure to ambient PM10, PM2.5 and NO2, but not O3, was associated with EID.

Blood Cadmium Levels and Oxygen Desaturation during the 6-Minute Walk Test in Patients with Chronic Obstructive Pulmonary Disease

Background and Objectives: chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation and a history of exposure to noxious stimuli. Cigarette smoking is the most important causal factor for developing COPD. Cadmium, a minor metallic element, is one of the main inorganic components in tobacco smoke. Inhaled cadmium was associated with a decline in lung function, gas exchange impairment, and the development of obstructive lung disease. Patients with COPD who had oxygen desaturation during the 6-min walk test (6MWT) had a significantly worse prognosis than non-desaturation in COPD patients. Nonetheless, few studies have addressed the influence of blood cadmium levels on exercise-induced oxygen desaturation in COPD patients. Our objective was to assess the potential impact of blood cadmium levels on oxygen desaturation during the 6MWT among COPD patients. Materials and Methods: we performed a retrospective analysis of patients with COPD who were examined for blood cadmium levels in a tertiary care referral center in Taiwan, between March 2020 and May 2021. The 6-min walk test was performed. Normal control subjects who had no evidence of COPD were also enrolled. Results: a total of 73 COPD patients were analyzed and stratified into the high-blood cadmium group (13 patients) and low-blood cadmium group (60 patients). A total of 50 normal control subjects without a diagnosis of COPD were enrolled. The high-blood cadmium group had a significantly higher extent of desaturation than the low-blood cadmium group. The frequency of desaturation during 6MWT revealed a stepwise-increasing trend with an increase in blood cadmium levels. A multivariable logistic regression model revealed that blood cadmium levels were independently associated with desaturation during the 6MWT (odds ratio 12.849 [95% CI 1.168–141.329]; p = 0.037). Conclusions: our findings indicate that blood cadmium levels, within the normal range, were significantly associated with desaturation during 6MWT in patients with COPD.

Telemonitoring of daily activities compared to the six-minute walk test further completes the puzzle of oximetry-guided interventions

Pulmonary rehabilitation is based on a thorough patient assessment, including peripheral oxygen saturation (SpO2) and heart rate (HR) at rest and on exertion. To understand whether exercise-field tests identify patients who desaturate (SpO2 < 90%) during physical activities, this study compared the six-minute walk test (6MWT) and daily-life telemonitoring. Cross-sectional study including 100 patients referred for pulmonary rehabilitation. The 6MWT was performed in hospital with continuous assessment of SpO2, HR, walked distance and calculated metabolic equivalent of tasks (METs). Patients were also evaluated in real-life by SMARTREAB telemonitoring, a combined oximetry-accelerometery with remote continuous assessment of SpO2, HR and METs. SMARTREAB telemonitoring identified 24% more desaturators compared with the 6MWT. Moreover, there were significant mean differences between 6MWT and SMARTREAB in lowest SpO2 of 7.2 ± 8.4% (P < 0.0005), in peak HR of − 9.3 ± 15.5% (P < 0.0005) and also in activity intensity of − 0.3 ± 0.8 METs (P < 0.0005). The 6MWT underestimates the proportion of patients with exercise-induced oxygen desaturation compared to real-life telemonitoring. These results help defining oximetry-guided interventions, such as telemedicine algorithms, oxygen therapy titration and regular physical activity assessment in pulmonary rehabilitation.

Prevalence of exercise-induced oxygen desaturation after recovery from SARS-CoV-2 pneumonia and use of lung ultrasound to predict need for pulmonary rehabilitation

BackgroundPersistence of breathlessness after recovery from SARS-CoV-2 pneumonia is frequent. Recovery from acute respiratory failure (ARF) is usually determined by normalized arterial blood gases (ABGs), but the prevalence of persistent exercise-induced desaturation (EID) and dyspnea is still unknown. MethodsWe investigated the prevalence of EID in 70 patients with normal arterial oxygen at rest after recovery from ARF due to COVID-19 pneumonia. Patients underwent a 6-min walking test (6MWT) before discharge from hospital. We recorded dyspnea score and heart rate during 6MWT. We also investigated the possible role of lung ultrasound (LU) in predicting EID. Patients underwent a LU scan and scores for each explored area were summed to give a total LU score. ResultsIn 30 patients (43%), oxygen desaturation was >4% during 6MWT. These patients had significantly higher dyspnea and heart rate compared to non-desaturators. LU score >8.5 was significantly able to discriminate patients with EID. ConclusionIn SARS-CoV-2 pneumonia, ABGs at discharge cannot predict the persistence of EID, which is frequent. LU may be useful to identify patients at risk who could benefit from a rehabilitation program.

COVID-19: Patient Characteristics in the First Phase of Postintensive Care Rehabilitation

ObjectiveTo describe clinical characteristics of patients after intensive care unit (ICU) treatment for coronavirus disease 2019 (COVID-19) who were admitted for inpatient rehabilitation. DesignA cross-sectional design. SettingInpatient rehabilitation care in the Netherlands. ParticipantsAll post-ICU patients with COVID-19 admitted to the rehabilitation center between April 2 and May 13, 2020, were invited to participate in the study. Included were patients older than 18 years needing inpatient rehabilitation after ICU treatment for COVID-19 (N=60; mean age, 59.9y; 75% male). InterventionsNot applicable. Main Outcome MeasuresThe following information was collected in the first week of inpatient rehabilitation care: (1) demographics; (2) ICU stay parameters; (3) medical, physical, and functional characteristics; and (4) self-reported symptoms. ResultsThe most important findings for rehabilitation were the following: in the first week after discharge to the rehabilitation center, 38.3% of all patients experienced exercise-induced oxygen desaturation, in 72.7% muscle weakness was present in all major muscle groups, and 21.7% had a reduced mobility in 1 or both shoulders. Furthermore 40% had dysphagia, and 39.2% reported symptoms of anxiety. ConclusionPost-ICU patients with COVID-19 display physical and anxiety symptoms as reported in other post-ICU patient groups. However, this study showed some remarkable clinical characteristics of post-ICU patients with COVID-19. Rehabilitation programs need to anticipate on this. Long-term follow-up studies are necessary.

Is the 1-Minute Sit-To-Stand Test a Good Tool to Evaluate Exertional Oxygen Desaturation in Chronic Obstructive Pulmonary Disease?

Background: Chronic obstructive pulmonary disease (COPD) is frequently associated with exertional oxygen desaturation, which may be evaluated using the 6-minute walking test (6MWT). However, it is a time-consuming test. The 1-minute sit-to-stand test (1STST) is a simpler test, already used to evaluate the functional status. The aim of this study was to compare the 1STST to the 6MWT in the evaluation of exertional desaturation. Methods: This was a cross-sectional study including 30 stable COPD patients who performed the 6MWT and 1STST on the same day. Six-minute walking distance (6MWD), number of 1STST repetitions (1STSTr), and cardiorespiratory parameters were recorded. Results: A significant correlation was found between the 6MWD and the number of 1STSTr (r = 0.54; p = 0.002). The minimum oxygen saturation (SpO2) in both tests showed a good agreement (intraclass correlation coefficient (ICC) 0.81) and correlated strongly (r = 0.84; p < 0.001). Regarding oxygen desaturation, the total agreement between the tests was 73.3% with a fair Cohen’s kappa (κ = 0.38; p = 0.018), and 93.33% of observations were within the limits of agreement for both tests in the Bland–Altman analysis. Conclusion: The 1STST seems to be a capable tool of detecting exercise-induced oxygen desaturation in COPD. Because it is a less time- and resources-consuming test, it may be applied during the outpatient clinic consultation to regularly evaluate the exercise capacity and exertional desaturation in COPD.

Pulmonary function and radiological features 4 months after COVID-19: first results from the national prospective observational Swiss COVID-19 lung study.

BackgroundThe infectious coronavirus disease 2019 (COVID-19) pandemic is an ongoing global healthcare challenge. Up to one-third of hospitalised patients develop severe pulmonary complications and acute respiratory distress syndrome. Pulmonary outcomes following COVID-19 are unknown.MethodsThe Swiss COVID-19 lung study is a multicentre prospective cohort investigating pulmonary sequelae of COVID-19. We report on initial follow-up 4 months after mild/moderate or severe/critical COVID-19 according to the World Health Organization severity classification.Results113 COVID-19 survivors were included (mild/moderate n=47, severe/critical n=66). We confirmed several comorbidities as risk factors for severe/critical disease. Severe/critical disease was associated with impaired pulmonary function, i.e. diffusing capacity of the lung for carbon monoxide (DLCO) % predicted, reduced 6-min walk distance (6MWD) and exercise-induced oxygen desaturation. After adjustment for potential confounding by age, sex and body mass index (BMI), patients after severe/critical COVID-19 had a DLCO 20.9% pred (95% CI 12.4–29.4% pred, p=0.01) lower at follow-up. DLCO % pred was the strongest independent factor associated with previous severe/critical disease when age, sex, BMI, 6MWD and minimal peripheral oxygen saturation at exercise were included in the multivariable model (adjusted odds ratio per 10% predicted 0.59, 95% CI 0. 37–0.87; p=0.01). Mosaic hypoattenuation on chest computed tomography at follow-up was significantly associated with previous severe/critical COVID-19 including adjustment for age and sex (adjusted OR 11.7, 95% CI 1.7–239; p=0.03).Conclusions4 months after severe acute respiratory syndrome coronavirus 2 infection, severe/critical COVID-19 was associated with significant functional and radiological abnormalities, potentially due to small-airway and lung parenchymal disease. A systematic follow-up for survivors needs to be evaluated to optimise care for patients recovering from COVID-19.

How the COVID-19 infection tsunami revolutionized the work of respiratory physiotherapists: an experience from Northern Italy.

Due to COVID-19 outbreak, to lighten the burden of acute and critical care hospitals, some respiratory rehabilitation departments have been used to host patients with COVID-19 in the post-acute phase. This new and unexpected situation required a change of roles and scheduling of the rehabilitation teams. In this manuscript we describe the unexpected and urgent organizational change of the Cardio-Pulmonary Rehabilitation (CPR) service during the COVID-19 emergency in a Northern Italian rehabilitation hospital, focusing on the Respiratory Physiotherapists' (RPTs) role. A quick three-days complete reorganization of the entire hospital was needed. A COVID-19 care team including a multidisciplinary panel of physicians, nurses, and RPTs was quickly performed to manage 90 beds for post acute patients with COVID-19. Within the team, the RPTs changed their shifts, so as to be available 16h per day, 7 days out of 7. Remodelled tasks in charge of RPTs were: oxygen therapy daily monitoring, non invasive ventilation (NIV) and continuous positive airways pressure (CPAP) delivery, pronation and postural changes to improve oxygenation, reconditioning with leg/arm cranking and exercises, initial and final patients' functional assessment by short-physical performance battery (SPPB) and 1-minute sit-to-stand test (1-STS) to evaluate motor conditions and exercise-induced oxygen desaturation. Three "what-to-do" algorithms were developed to guide: i) oxygen de-escalation by reducing inhaled fraction of oxygen (FiO2); ii) oxygenation improvement through the use of Venturi mask; iii) reconditioning and physical activity. One-hundred seventy patients were treated in one month. As main topics, RPTs have been involved in oxygen therapy management in almost a third of the admitted patients, reconditioning exercises in 60% of the cases, and initial and final functional motor capacity assessment in all patients. Details of activities performed by the RPT in one typical working day are also shown. Our reorganization has exploited the professional skills and clinical expertise of the RPTs. This re-organization can provide practical insights to other facilities that are facing this crisis, and may be a starting point for implementing post-COVID-19 rehabilitation. Future studies will have to improve and review this organization.

Exercise-Induced Oxygen Desaturation during the 6-Minute Walk Test.

The 6-minute walk test (6MWT) is not intended to document oxygen (O2) desaturation during exertion but is often used for this purpose. Because of this, it only has modest reproducibility in determining the need for ambulatory O2 therapy in patients with cardiopulmonary disease. The diagnostic and prognostic value of detecting exertional O2 desaturation is still unknown. The aims of this study were to estimate the prevalence of O2 desaturation during a 6MWT based on pulse oximetry measurements at the beginning and end of a 6MWT in a clinical population of patients with suspected cardiopulmonary disease and to determine whether the pulmonary function test (PFT) can predict exercise-induced desaturation during a 6MWT. This retrospective cohort study reviewed the results of the 6MWT and the PFT (i.e., spirometry, lung volumes, and diffusion capacity) of all patients who were evaluated for suspected cardiopulmonary disease at an academic medical center during a 5-year study period. The patients were categorized into three groups based on the change in O2 saturation by pulse oximetry (SpO2) from start to end of the 6MWT: (1) SpO2 decreased by ≥3%; (2) SpO2 unchanged (−2 ≤ Δ ≤ 0%); and (3) SpO2 increased by ≥1%. Demographic, anthropometric, and lung function measurements were analyzed to determine which factors predicted O2 desaturation during the 6MWT. Of the 319 patients who underwent the 6MWT and the PFT from November 2005 until December 2010 (mean age = 54 ± 0.78 years, 63% women, 58% Whites, body mass index = 29.63 ± 8.10 kg/m2), 113 (35%) had a decreased SpO2, 146 (46%) had no change, and 60 (19%) had an increased SpO2 from the start to end of test. Our bivariate analysis found age, spirometric measures, and diffusion capacity for carbon monoxide (DLCO) had statistically significant inverse associations with the SpO2 change category (p < 0.001). Both a 3% and 4% drop in SpO2 during the 6MWT were statistically significantly associated with an older age, a higher prevalence of obstruction, and reduced forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC, DLCO and 6-minute walk distance (6MWD). Multivariable logistic regression analyses revealed that only DLCO was a significant independent predictor of the change in SpO2 and a ≥ 4% O2 desaturation during a 6MWT. Receiver operating curve analysis indicates DLCO cut-off of 45% is 82% sensitive and 40% specific in identifying ≥4% O2 desaturators, with an area under the curve of 0.788 ± 0.039 (p < 0.001). The prevalence of a ≥ 3% oxygen desaturation via pulse oximetry during a 6MWT in our clinical population of patients with suspected cardiopulmonary disease was 35%. Although age, spirometric lung volumes, and DLCO had statistically significant unadjusted inverse associations with the change in SpO2 during a 6MWT, the DLCO is the only significant independent predictor of both the magnitude of the change in SpO2 and the occurrence of O2 desaturation of at least 4%, respectively, during the test. Clinical Implications: A DLCO cut-off of 45% may be useful in identifying patients at risk for exertional hypoxemia during a 6MWT.

Effects of Non-Invasive Ventilation Combined with Oxygen Supplementation on Exercise Performance in COPD Patients with Static Lung Hyperinflation and Exercise-Induced Oxygen Desaturation: A Single Blind, Randomized Cross-Over Trial.

The effects of non-invasive ventilation (NIV) in addition to supplemental oxygen on exercise performance in patients with chronic obstructive pulmonary disease (COPD) with hyperinflation and exercise-induced desaturation (EID) remain unclear. We hypothesized that these patients would benefit from NIV and that this effect would be an add-on to oxygen therapy. Thirteen COPD patients with a residual volume >150% of predicted, normal resting arterial oxygen pressure (PaO2) and carbon-dioxide pressure (PaCO2) and EID during a six-minute walk test were included. Patients performed four constant work-rate treadmill tests, each consisting of two exercise bouts with a recovery period in between, wearing an oronasal mask connected to a ventilator and oxygen supply. The ventilator was set to the following settings in fixed order with clockwise rotation: Sham (continuous positive airway pressure (CPAP) 2 cm H2O, FiO2 21%), oxygen (CPAP 2 cm H2O, FiO2 35%), NIV and oxygen (inspiratory positive airway pressure (IPAP) 14 cm H2O/expiratory positive airway pressure (EPAP) 6 cm H2O, inspired oxygen fraction (FiO2) 35%), intermittent (walking: Sham setting, recovery: NIV and oxygen setting). During the first exercise, bout patients walked further with the oxygen setting compared to the sham setting (225 ± 107 vs 120 ± 50 meters, p < 0.05), but even further with the oxygen/NIV setting (283 ± 128 meters; p < 0.05). Recovery time between two exercise bouts was shortest with NIV and oxygen. COPD patients with severe static hyperinflation and EID benefit significantly from NIV in addition to oxygen during exercise and recovery.

Effect of domiciliary oxygen therapy on exercise capacity and quality of life in patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension: a randomised, placebo-controlled trial.

We investigated whether domiciliary oxygen therapy (DOXT) increases exercise capacity and quality of life in patients with pulmonary arterial or distal chronic thromboembolic pulmonary hypertension (PAH/CTEPH) presenting with mild resting hypoxaemia and exercise-induced oxygen desaturation. 30 patients with PAH/CTEPH, mean±sd age 60±15 years, pulmonary artery pressure 39±11 mmHg, resting arterial oxygen saturation measured by pulse oximetry (S pO2 ) ≥90%, S pO2 drop during a 6-min walk test ≥4%, on pulmonary hypertension-targeted medication, were randomised in a double-blind crossover protocol to DOXT and placebo (ambient air) treatment, each over 5 weeks, at 3 L·min-1 via nasal cannula overnight and when resting during the day. Treatment periods were separated by 2 weeks of washout. Co-primary outcomes were changes in 6-min walk distance (6MWD, breathing ambient air) and physical functioning scale of the 36-item short-form medical outcome questionnaire during treatment periods. DOXT increased the 6MWD from baseline 478±113 m by a mean (95% CI) of 19 (6-32) m, and physical functioning from 52±29 by 4 (0-8) points. Corresponding changes with placebo were 1 (-11-13) m in 6MWD and -2 (-6-2) points in physical functioning. Between-treatment differences in changes were 6MWD 18 (1-35) m (p=0.042) and physical functioning 6 (1-11) points (p=0.029). DOXT significantly improved the NewYork Heart Association functional class versus placebo. This first randomised trial in PAH/CTEPH patients with exercise-induced hypoxaemia demonstrates that DOXT improves exercise capacity, quality of life and functional class. The results support large long-term randomised trials of DOXT in PAH/CTEPH.

Exercise-Induced Oxygen Desaturation as a Predictive Factor for Longitudinal Decline in 6-Minute Walk Distance in Subjects With COPD.

There are limited longitudinal studies reporting predictive factors for decline in 6-min walk distance (6MWD) in patients with COPD. While previous studies have confirmed the association between air-flow limitation and decline in 6MWD, other factors have not been clarified. The objective of this study was to investigate whether exercise-induced oxygen desaturation (EID) could be a predictive factor for decline in 6MWD in patients with COPD. The interactive effect of air-flow limitation on the association between EID and decline in 6MWD was also investigated. A longitudinal observational study was conducted with 71 out-patients with COPD who were followed for 1 year. 6MWD, EID, spirometry, and clinical characteristics were assessed. The effect of EID on changes in 6MWD was examined using linear regression analyses. Furthermore, the subjects were categorized into 4 groups according to their EID and air-flow limitation status, and changes in 6MWD were compared among the groups. 51 subjects completed the follow-up assessments, and 29 (56.9%) experienced EID. Multiple linear regression model revealed that EID was the only predictive factor for changes in 6MWD after adjusting for confounders (β = -38.9, P = .02). As results of multiple comparisons among the 4 groups based on EID and air-flow limitation status, changes in 6MWD in the EID and severe air-flow limitation group were the lowest. Our results revealed that EID was a predictive factor for decline in the functional capacity of subjects with COPD. The assessment of EID and air-flow limitation would thus be useful in estimating the prognosis of decline in the functional capacity of patients with COPD.

Distance-saturation product of the 6-minute walk test predicts mortality of patients with non-cystic fibrosis bronchiectasis.

Previous surveillance methods to monitor the prognoses of patients with bronchiectasis are too complex for use in daily practice. The 6-minute walk test (6MWT) is a simple exercise test to predict the prognosis of chronic obstructive airway disease and numerous chronic lung diseases, including idiopathic pulmonary fibrosis. No studies have investigated exercise-induced oxygen desaturation (EID) and distance-saturation product (DSP) of 6MWT to predict the prognoses of patients with bronchiectasis. This was a prospective study to identify correlations between variables of 6MWT and mortality in patients with bronchiectasis over a 6-year period. The study cohort included 69 patients with stable non-cystic fibrosis (non-CF) bronchiectasis who were regularly evaluated for functional status via 6-minute walk distance (6MWD), spirometry, BODE index, EID, and DSP. Of the 69 patients, 9 (13%) died and 60 (87%) survived during the 6-year follow-up period. The percentage of EID was higher [7 of 9 patients (78%) vs. 22 of 60 patients (27%), P=0.003] in the non-survivors group. The 6MWD (467.9±77.1 vs. 363.7±126.7 m, P=0.001) was higher in the survivors group. DSP was significantly lower in the non-survivors group (411.0±78.4 vs. 283.9±90.0 m%, P<0.001). Multivariate analysis showed that DSP (OR =0.983; 95% CI: 0.974-0.993, P=0.001) was the best parameter of 6MWT to predict mortality. Patients with a lower DSP of <280 m% were at a 66.5-fold greater risk (OR =66.5; 95% CI: 9.4-469.2) of 6-year mortality compared with those with DSP >280 m% (P<0.001). DSP is a simple parameter to predict 6-year mortality in patients with non-CF bronchiectasis.

Usefulness of the desaturation-distance ratio from the six-minute walk test for patients with COPD.

PurposeA straightforward, noninvasive method is needed to assess emphysema and pulmonary hypertension (PH) in COPD patients. The desaturation–distance ratio (DDR) is an index derived from the distance traveled and level of desaturation during a six-minute walk test (6MWT); it has previously been shown to be associated with percentage of forced expiratory volume in the first second of expiration (%FEV1.0) and percentage of diffusion capacity of the lung for carbon monoxide (%DLCO). The aim of this study was to examine the associations between DDR and emphysema and PH.Patients and methodsWe collected the following data for 74 stable COPD outpatients: lung function tests (%FEV1.0 and %DLCO), 6MWT distance and desaturation, and area of emphysema on computed tomography (percentage of low attenuation area). Enlargement of the pulmonary artery (PA) was assessed by the ratio of the diameter of the PA to that of the aorta (PA:A ratio) as an index of PH. DDR was calculated by the distance traveled and the degree of desaturation reached during a 6MWT. The relationships between study outcomes were assessed with Spearman’s rank-correlation analysis. Receiver operating characteristic (ROC) curves were used to determine the threshold values with the optimum cutoff points for predicting severe or very severe airway obstruction, pulmonary diffusing capacity disorder, moderate or severe emphysema, and enlargement of the PA.ResultsDDR correlated significantly with %FEV1.0, %DLCO, %LAA, and PA:A ratio. DDR showed high accuracy (area under the ROC curve >0.7) for predicting severe or very severe airway obstruction, pulmonary diffusing capacity disorder, moderate or severe emphysema, and enlargement of the PA.ConclusionThe results suggest that DDR is a good index of emphysema and PH in COPD patients. The 6MWT is widely used to assess COPD, and DDR could help with the early diagnosis of COPD.