Oxygen desaturation during a 6 min walk test is a sign of nocturnal hypoxemia.
ABSTRACT: BACKGROUND?Patients with chronic obstructive pulmonary disease (COPD) may experience sleep disordered breathing with nocturnal desaturation. An exploratory study was performed to determine whether any commonly measured clinical parameters were useful in predicting nocturnal desaturation in patients with COPD. A validation study was subsequently performed to confirm the utility of the parameter identified in the exploratory study as most useful in this regard.A total of 103 (exploratory cohort) and 200 (validation cohort) consecutive patients with COPD admitted for pulmonary rehabilitation were evaluated. Standard outcome measures including nocturnal oximetry and the 6 min walk test (6MWT) on room air with continuous pulse oximetry were assessed. Patients with sleep apnea or those undergoing long-term oxygen therapy were excluded.In the exploratory study, the mean (± SD) patient age was 70 ± 9.9 years, with forced expiratory volume in 1 s of 0.76 ± 0.34 L, which was 36 ± 16% of predicted. Body mass index, arterial oxygen tension, oxygen saturation by pulse oximetry at rest and during the 6MWT all demonstrated significant correlations with percentage of time spent with a saturation <90%. When the lowest pulse oximetry during the 6MWT was ?88%, 10 of 21 patients demonstrated a saturation <90% for at least 30% of sleep time. This measure yielded a positive likelihood ratio of 3.77 (95% CI 1.87 to 7.62) compared with those who did not reach this threshold value. The validation study confirmed similar detection characteristics.Results from the present study suggest that monitoring oxygen saturation changes during a 6MWT is useful in helping to identify COPD patients who may experience significant nocturnal desaturation.
Project description:Negative pressure ventilation (NPV), when used as an adjuvant to pulmonary rehabilitation, improves lung function, increases exercise capacity, and reduces exacerbations. The aim of this study was to determine whether maintenance NPV improves long-term clinical outcomes and reduces mortality in patients with chronic obstructive pulmonary disease (COPD). Between 2003 and 2009, 341 patients were treated for COPD either with or without hospital-based NPV. We measured forced expiratory volume in one second (FEV1), 6-min walking distance (6MWD), and oxygen saturation by pulse oximetry (SpO2) during a 6-min walk test (6MWT) every 3-6 months. Desaturation (D) during the 6MWT was defined as a reduction in SpO2 of ≥10% from baseline. The NPV group had a better survival outcome than the Non-NPV group. The 8-year survival probabilities for the NPV and Non-NPV groups were 60% and 20%, respectively (p < 0.01). Baseline desaturation was a significant risk factor for death, and the risk of death increased with desaturation severity (SpO2 80~89: hazard ratios (HR) 2.7, 95% confidence interval (CI) 1.4-5.3; SpO2 < 80: HR 3.1, 95% CI 1.3-7.4). The NPV group had a slower decline in lung function and 6MWD. The NPV + D and Non-NPV+D had a threefold and fourfold increase in the risks of all-cause mortality compared with the NPV-ND, respectively. Maintenance non-invasive NPV reduced long-term mortality in COPD patients. The desaturating COPD patients had an increased mortality risk compared with non-desaturating COPD patients.
Project description:Long-term oxygen therapy (LTOT) is the only component of the management of chronic obstructive pulmonary disease (COPD) that improves survival in patients with severe daytime hypoxemia. LTOT is usually provided by a stationary oxygen concentrator and is recommended to be used for at least 15-18 h a day. Several studies have demonstrated a deterioration in arterial blood gas pressures and oxygen saturation during sleep in patients with COPD, even in those not qualifying for LTOT. The suggestion has been made that the natural progression of COPD to its end stages of chronic pulmonary hypertension, severe hypoxemia, right heart failure, and death is dependent upon the severity of desaturation occurring during sleep. The primary objective of the International Nocturnal Oxygen (INOX) trial is to determine, in patients with COPD not qualifying for LTOT but who present significant nocturnal arterial oxygen desaturation, whether nocturnal oxygen provided for a period of 3 years decreases mortality or delay the prescription of LTOT.The INOX trial is a 3-year, multi-center, placebo-controlled, randomized trial of nocturnal oxygen therapy added to usual care. Eligible patients are those with a diagnosis of COPD supported by a history of past smoking and obstructive disease who fulfill our definition of significant nocturnal oxygen desaturation (i.e., ≥ 30% of the recording time with transcutaneous arterial oxygen saturation < 90% on either of two consecutive recordings). Patients allocated in the control group receive room air delivered by a concentrator modified to deliver 21% oxygen. The comparison is double blind. The primary outcome is a composite of mortality from all cause or requirement for LTOT. Secondary outcomes include quality of life and utility measures, costs from a societal perspective and compliance with oxygen therapy. The follow-up period is intended to last at least 3 years.The benefits of LTOT have been demonstrated whereas those of nocturnal oxygen therapy alone have not. The INOX trial will likely determine whether supplemental oxygen during sleep is effective in reducing mortality, delaying the need for LTOT and improving health-related quality of life in patients with COPD who desaturate overnight.Current Controlled Trials ISRCTN50085100 ; ClinicalTrials.gov NCT01044628 (date of registration: January 6, 2010).
Project description:BACKGROUND: It remains unknown whether desaturation profiles during daily living are associated with prognosis in patients with chronic obstructive pulmonary disease (COPD). Point measurements of resting oxygen saturation by pulse oximetry (SpO2) and partial pressure of arterial oxygen (PaO2) are not sufficient for assessment of desaturation during activities of daily living. A small number of studies continuously monitored oxygen saturation throughout the day during activities of daily living in stable COPD patients. This study aims to analyse the frequency of desaturation in COPD outpatients, and investigate whether the desaturation profile predicts the risk of exacerbation. METHODS: We studied stable COPD outpatients not receiving supplemental oxygen therapy. Baseline assessments included clinical assessment, respiratory function testing, arterial blood gas analysis, body mass index, and the COPD Assessment Test (CAT). Patients underwent 24-hour ambulatory monitoring of SpO2 during activities of daily living. Exacerbations of COPD and death from any cause were recorded. RESULTS: Fifty-one patients were enrolled in the study, including 12 current smokers who were excluded from the analyses in case high serum carboxyhaemoglobin concentrations resulted in inaccurately high SpO2 readings. The mean percent predicted forced expiratory volume in one second (%FEV1) was 50.9%. The mean proportion of SpO2 values below 90% was 3.0% during the day and 7.4% during the night. There were no daytime desaturators, defined as???30% of daytime SpO2 values below 90%. Twenty-one exacerbations occurred in 13 patients during the mean follow-up period of 26.4 months. Univariate and multivariate Cox proportional hazards analyses did not detect any significant factors associated with exacerbation. CONCLUSIONS: Our 24-hour ambulatory oximetry monitoring provided precise data regarding the desaturation profiles of COPD outpatients. Both daytime and nighttime desaturations were infrequent. The proportion of ambulatory SpO2 values below 90% was not a significant predictor of exacerbation.
Project description:The two-minute walk test (2MWT) is less well validated than the well-known six-minute walk test (6MWT) as a field walking test in patients with chronic obstructive pulmonary disease (COPD). The primary objective of this study was to compare the accuracy of the 2MWT to the 6MWT in detecting exercise-induced oxygen desaturation in patients with severe COPD. Twenty-six patients with COPD (age: 61 ± 10 years, forced expired volume in one second: 37 ± 10%) that were normoxemic at rest performed a 2MWT and a 6MWT under normal ambient conditions on two consecutive days in random order. Oxygen saturation, total walking distance, heart rate, breathing frequency, dyspnea, and leg fatigue were evaluated. Average walking distances were 150 m (95% confidence interval (95% CI): 134-165 m) and 397 m (95% CI: 347-447 m) for the 2MWT and 6MWT, respectively (r = 0.80, p < 0.0001). The difference in minimum oxygen saturation during the 2MWT (83%, 95% CI: 81-86%) and 6MWT (mean 82%, 95% CI: 80-84%) was not statistically different and the data strongly correlated between the groups (r = 0.81, p < 0.0001). Other measurements from the 6MWT, including heart rate, breathing rate, and levels of perceived exertion were also comparable in 2MWT. The 2MWT showed comparable validity in detecting exercise-induced oxygen desaturation in patients with severe COPD compared to the 6MWT.
Project description:Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that leads to progressive weakness of the respiratory and limb muscles. Consequently, most patients with ALS exhibit progressive hypoventilation, which worsens during sleep. The aim of this study was to evaluate the relationship between nocturnal hypoxia and cognitive dysfunction and to assess the pattern of nocturnal hypoxia in patients with ALS.Twenty-five patients with definite or probable ALS underwent neuropsychologic testing, nocturnal pulse oximetry, and capnography. Patients were grouped according to the presence of nocturnal hypoxia (SpO2<95% for ?10% of the night) and their clinical characteristics and cognitive function were compared.Compared to patients without nocturnal hypoxia, those with nocturnal hypoxia (n?=?10, 40%) had poor memory retention (p?=?0.039) and retrieval efficiency (p?=?0.045). A cluster-of-desaturation pattern was identified in 7 patients (70%) in the Hypoxia Group.These results suggest that nocturnal hypoxia can be related to cognitive dysfunction in ALS. In addition, a considerable number of patients with ALS may be exposed to repeated episodes of deoxygenation-reoxygenation (a cluster-of-desaturation pattern) during sleep, which could be associated with the generation of reactive oxygen species. Further studies are required to define the exact causal relationships between these phenomena, the exact manifestations of nocturnal cluster-of-desaturation patterns, and the effect of clusters of desaturation on ALS progression.
Project description:BACKGROUND:Chronic obstructive pulmonary disease (COPD) patients can suffer from low blood oxygen concentrations. Peripheral blood oxygen saturation (SpO2), as assessed by pulse oximetry, is commonly measured during the day using a spot check, or continuously during one or two nights to estimate nocturnal desaturation. Sampling at this frequency may overlook natural fluctuations in SpO2. OBJECTIVE:This study used wearable finger pulse oximeters to continuously measure SpO2 during daily home routines of COPD patients and assess natural SpO2 fluctuations. METHODS:A total of 20 COPD patients wore a WristOx2 pulse oximeter for 1 week to collect continuous SpO2 measurements. A SenseWear Armband simultaneously collected actigraphy measurements to provide contextual information. SpO2 time series were preprocessed and data quality was assessed afterward. Mean SpO2, SpO2 SD, and cumulative time spent with SpO2 below 90% (CT90) were calculated for every (1) day, (2) day in rest, and (3) night to assess SpO2 fluctuations. RESULTS:A high percentage of valid SpO2 data (daytime: 93.27%; nocturnal: 99.31%) could be obtained during a 7-day monitoring period, except during moderate-to-vigorous physical activity (MVPA) (67.86%). Mean nocturnal SpO2 (89.9%, SD 3.4) was lower than mean daytime SpO2 in rest (92.1%, SD 2.9; P<.001). On average, SpO2 in rest ranged over 10.8% (SD 4.4) within one day. Highly varying CT90 values between different nights led to 50% (10/20) of the included patients changing categories between desaturator and nondesaturator over the course of 1 week. CONCLUSIONS:Continuous SpO2 measurements with wearable finger pulse oximeters identified significant SpO2 fluctuations between and within multiple days and nights of patients with COPD. Continuous SpO2 measurements during daily home routines of patients with COPD generally had high amounts of valid data, except for motion artifacts during MVPA. The identified fluctuations can have implications for telemonitoring applications that are based on daily SpO2 spot checks. CT90 values can vary greatly from night to night in patients with a nocturnal mean SpO2 around 90%, indicating that these patients cannot be consistently categorized as desaturators or nondesaturators. We recommend using wearable sensors for continuous SpO2 measurements over longer time periods to determine the clinical relevance of the identified SpO2 fluctuations.
Project description:Background: Chronic obstructive pulmonary disease (COPD) patients enrolled into the Long-term Oxygen Treatment Trial had hypoxemia at rest, hypoxemia on exertion, or hypoxemia both at rest and on exertion. We hypothesized that patients with different patterns of hypoxemia may have significant differences in clinical features. Methods: All patients had COPD and oxygen saturation measured by pulse oximetry (blood oxygenation [SpO2]) at rest and during the 6-minute walk test (6MWT). Hypoxemia at rest was defined as resting SpO2 between 89-93%. SpO2 < 90% for at least 10 seconds and ³ 80% for at least 5 minutes during ambulation characterized hypoxemia on exertion. Severe exercise hypoxemia (< 80% for > 1 minute) was exclusionary.Results: Of 738 patients studied, 133 (18.0%) had mild-moderate hypoxemia at rest only, 319 (43.2%) had hypoxemia on exertion only, and 286 (38.8%) had hypoxemia at both rest and exertion. Patients with hypoxemia at rest only were more likely to be current smokers, had higher body mass index (BMI) and a higher incidence of self-reported diabetes. Patients with hypoxemia on exertion only were more severely obstructed compared to the other groups. General and disease-specific quality of life scores were similarly impaired in all groups. Quality of well-being scores were more impaired in those with hypoxemia at rest only.Conclusions: COPD patients with mild-moderate hypoxemia have distinct clinical characteristics based on the pattern of oxygen desaturation at rest and with exertion.
Project description:BACKGROUND:Long-term treatment with supplemental oxygen has unknown efficacy in patients with stable chronic obstructive pulmonary disease (COPD) and resting or exercise-induced moderate desaturation. METHODS:We originally designed the trial to test whether long-term treatment with supplemental oxygen would result in a longer time to death than no use of supplemental oxygen among patients who had stable COPD with moderate resting desaturation (oxyhemoglobin saturation as measured by pulse oximetry [Spo2], 89 to 93%). After 7 months and the randomization of 34 patients, the trial was redesigned to also include patients who had stable COPD with moderate exercise-induced desaturation (during the 6-minute walk test, Spo2 ?80% for ?5 minutes and <90% for ?10 seconds) and to incorporate the time to the first hospitalization for any cause into the new composite primary outcome. Patients were randomly assigned, in a 1:1 ratio, to receive long-term supplemental oxygen (supplemental-oxygen group) or no long-term supplemental oxygen (no-supplemental-oxygen group). In the supplemental-oxygen group, patients with resting desaturation were prescribed 24-hour oxygen, and those with desaturation only during exercise were prescribed oxygen during exercise and sleep. The trial-group assignment was not masked. RESULTS:A total of 738 patients at 42 centers were followed for 1 to 6 years. In a time-to-event analysis, we found no significant difference between the supplemental-oxygen group and the no-supplemental-oxygen group in the time to death or first hospitalization (hazard ratio, 0.94; 95% confidence interval [CI], 0.79 to 1.12; P=0.52), nor in the rates of all hospitalizations (rate ratio, 1.01; 95% CI, 0.91 to 1.13), COPD exacerbations (rate ratio, 1.08; 95% CI, 0.98 to 1.19), and COPD-related hospitalizations (rate ratio, 0.99; 95% CI, 0.83 to 1.17). We found no consistent between-group differences in measures of quality of life, lung function, and the distance walked in 6 minutes. CONCLUSIONS:In patients with stable COPD and resting or exercise-induced moderate desaturation, the prescription of long-term supplemental oxygen did not result in a longer time to death or first hospitalization than no long-term supplemental oxygen, nor did it provide sustained benefit with regard to any of the other measured outcomes. (Funded by the National Heart, Lung, and Blood Institute and the Centers for Medicare and Medicaid Services; LOTT ClinicalTrials.gov number, NCT00692198 .).
Project description:<h4>Background</h4>Determination of the blood oxyhemoglobin saturation in the retinal vessels of the eye can be achieved through spectrophotometric retinal oximetry which provides access to the state of oxyhemoglobin saturation in the central nervous system circulation. The purpose of this study was to test the capability of the Oxymap T1 oximeter to detect systemic hypoxemia and the effect of supplemental oxygen on retinal vessel oxyhemoglobin saturation.<h4>Methods</h4>Oxygen saturation of hemoglobin in retinal arterioles and venules was measured in 11 subjects with severe chronic obstructive pulmonary disease (COPD) on long term oxygen therapy. Measurements were made with and without their daily supplemental oxygen. Eleven healthy age and gender matched subjects were measured during ambient air breathing for comparison of oxyhemoglobin saturation in retinal arterioles and venules. Retinal arteriolar oxyhemoglobin saturation in COPD subjects inspiring ambient air was compared with finger pulse oximetry and blood samples from radial artery.<h4>Results</h4>COPD subjects had significantly lower oxyhemoglobin saturation during ambient air breathing than healthy controls in both retinal arterioles (87.2%±4.9% vs. 93.4%±4.3%, p = 0.02; n = 11) and venules (45.0%±10.3% vs. 55.2%±5.5%, p = 0.01). Administration of their prescribed supplemental oxygen increased oxyhemoglobin saturation in retinal arterioles (87.2%±4.9% to 89.5%±6.0%, p = 0.02) but not in venules (45.0%±10.3% to 46.7%±12.8%, p = 0.3). Retinal oximetry values were slightly lower than radial artery blood values (mean percentage points difference = -5.0±5.4, 95% CI: -15.68 to 5.67) and finger pulse oximetry values (-3.1±5.5, 95% CI: -14.05 to 7.84).<h4>Conclusions</h4>The noninvasive Oxymap T1 retinal oximetry detects hypoxemia in central nervous system vessels in patients with severe COPD compared with healthy controls. The instrument is sensitive to changes in oxygen breathing but displays slightly lower measures than finger pulse oximetry or radial artery measures. With further technological improvement, retinal oximetry may offer noninvasive "on-line" measurement of oxygen levels in central circulation in general anesthesia and critically ill patients.
Project description:Importance:During mountain travel, patients with chronic obstructive pulmonary disease (COPD) are at risk of experiencing severe hypoxemia, in particular, during sleep. Objective:To evaluate whether preventive dexamethasone treatment improves nocturnal oxygenation in lowlanders with COPD at 3100 m. Design, Setting, and Participants:A randomized, placebo-controlled, double-blind, parallel trial was performed from May 1 to August 31, 2015, in 118 patients with COPD (forced expiratory volume in the first second of expiration [FEV1] >50% predicted, pulse oximetry at 760 m ?92%) who were living at altitudes below 800 m. The study was conducted at a university hospital (760 m) and high-altitude clinic (3100 m) in Tuja-Ashu, Kyrgyz Republic. Patients underwent baseline evaluation at 760 m, were taken by bus to the clinic at 3100 m, and remained at the clinic for 2 days and nights. Participants were randomized 1:1 to receive either dexamethasone, 4 mg, orally twice daily or placebo starting 24 hours before ascent and while staying at 3100 m. Data analysis was performed from September 1, 2015, to December 31, 2016. Interventions:Dexamethasone, 4 mg, orally twice daily (dexamethasone total daily dose, 8 mg) or placebo starting 24 hours before ascent and while staying at 3100 m. Main Outcomes and Measures:Difference in altitude-induced change in nocturnal mean oxygen saturation measured by pulse oximetry (Spo2) during night 1 at 3100 m between patients receiving dexamethasone and those receiving placebo was the primary outcome and was analyzed according to the intention-to-treat principle. Other outcomes were apnea/hypopnea index (AHI) (mean number of apneas/hypopneas per hour of time in bed), subjective sleep quality measured by a visual analog scale (range, 0 [extremely bad] to 100 [excellent]), and clinical evaluations. Results:Among the 118 patients included, 18 (15.3%) were women; the median (interquartile range [IQR]) age was 58 (52-63) years; and FEV1 was 91% predicted (IQR, 73%-103%). In 58 patients receiving placebo, median nocturnal Spo2 at 760 m was 92% (IQR, 91%-93%) and AHI was 20.5 events/h (IQR, 12.3-48.1); during night 1 at 3100 m, Spo2 was 84%?(IQR, 83%-85%) and AHI was 39.4 events/h (IQR, 19.3-66.2) (P?<?.001 both comparisons vs 760 m). In 60 patients receiving dexamethasone, Spo2 at 760 m was 92% (IQR, 91%-93%) and AHI was 25.9 events/h (IQR, 16.3-37.1); during night 1 at 3100 m, Spo2 was 86% (IQR, 84%-88%) (P?<?.001 vs 760 m) and AHI was 24.7 events/h (IQR, 13.2-33.7) (P?=?.99 vs 760 m). Altitude-induced decreases in Spo2 during night 1 were mitigated by dexamethasone vs placebo by a mean of 3% (95% CI, 2%-3%), and increases in AHI were reduced by 18.7 events/h (95% CI, 12.0-25.3). Similar effects were observed during night 2. Subjective sleep quality was improved with dexamethasone during night 2 by 12% (95% CI, 0%-23%). Sixteen (27.6%) patients using dexamethasone had asymptomatic hyperglycemia. Conclusions and Relevance:In lowlanders in Central Asia with COPD traveling to a high altitude, preventive dexamethasone treatment improved nocturnal oxygen saturation, sleep apnea, and subjective sleep quality. Trial Registration:ClinicalTrials.gov Identifier: NCT02450994.