William Slivka - Academia.edu (original) (raw)
Papers by William Slivka
COPD: Journal of Chronic Obstructive Pulmonary Disease, 2013
American Journal of Respiratory and Critical Care Medicine, 2010
Rationale: Before the introduction of combination antiretroviral (ARV) therapy, patients infected... more Rationale: Before the introduction of combination antiretroviral (ARV) therapy, patients infected with HIV had an increased prevalence of respiratory symptoms and lung function abnormalities. The prevalence and exact phenotype of pulmonary abnormalities in the current era are unknown. In addition, these abnormalities may be underdiagnosed. Objectives: Our objective was to determine the current burden of respiratory symptoms, pulmonary function abnormalities, and associated risk factors in individuals infected with HIV. Methods: Cross-sectional analysis of 167 participants infected with HIV who underwent pulmonary function testing. Measurements and Main Results: Respiratory symptoms were present in 47.3% of participants and associated with intravenous drug use (odds ratio [OR] 3.64; 95% confidence interval [CI], 1.32-10.046; P 5 0.01). Only 15% had previous pulmonary testing. Pulmonary function abnormalities were common with 64.1% of participants having diffusion impairment and 21% having irreversible airway obstruction. Diffusion impairment was independently associated with ever smoking (OR 2.46; 95% CI, 1.16-5.21; P 5 0.02) and Pneumocystis pneumonia prophylaxis (OR 2.94; 95% CI, 1.10-7.86; P 5 0.01), whereas irreversible airway obstruction was independently associated with pack-years smoked (OR 1.03 per pack-year; 95% CI, 1.01-1.05; P , 0.01), intravenous drug use (OR 2.87; 95% CI, 1.15-7.09; P 5 0.02), and the use of ARV therapy (OR 6.22; 95% CI, 1.19-32.43; P 5 0.03). Conclusions: Respiratory symptoms and pulmonary function abnormalities remain common in individuals infected with HIV. Smoking and intravenous drug use are still important risk factors for pulmonary abnormalities, but ARV may be a novel risk factor for irreversible airway obstruction. Obstructive lung disease is likely underdiagnosed in this population.
COPD: Journal of Chronic Obstructive Pulmonary Disease, 2007
There is increasing interest in the objective measurement of physical activity in chronic obstruc... more There is increasing interest in the objective measurement of physical activity in chronic obstructive pulmonary disease (COPD) patients due to the close relationship between physical activity level, health, disability and mortality. We aimed to (a) determine the validity and reproducibility of an activity monitor that integrates accelerometry with multiple physiologic sensors in the determination of energy expenditure in COPD subjects and (b) to document the independent contribution of the additional physiologic sensors to accelerometry measures in improving true energy expenditure determination. Eight subjects (4 male, FEV 1 56.4 ± 14.1%, RV 145.0 ± 75.7%) performed 2 separate 6-minute walk and 2 incremental shuttle walk exercise tests. Energy expenditure was calculated during each exercise test using the physiologic activity monitor and compared to a validated exhaled breath metabolic system. Test-retest reproducibility of physiologic activity monitor during the walking tests was comparable to an exhaled breath metabolic system. Physiologic sensor data significantly improved the explained variance in energy expenditure determination (r 2 = 0.88) compared to accelerometry data alone (r 2 = 0.68). This physiologic activity monitor provides a valid and reproducible estimate of energy expenditure during slow to moderate paced walking in a laboratory setting and represents an objective method to assess activity in COPD subjects.
COPD: Journal of Chronic Obstructive Pulmonary Disease, 2007
There is increasing interest in the objective measurement of physical activity in chronic obstruc... more There is increasing interest in the objective measurement of physical activity in chronic obstructive pulmonary disease (COPD) patients due to the close relationship between physical activity level, health, disability and mortality. We aimed to (a) determine the validity and reproducibility of an activity monitor that integrates accelerometry with multiple physiologic sensors in the determination of energy expenditure in COPD subjects and (b) to document the independent contribution of the additional physiologic sensors to accelerometry measures in improving true energy expenditure determination. Eight subjects (4 male, FEV 1 56.4 ± 14.1%, RV 145.0 ± 75.7%) performed 2 separate 6-minute walk and 2 incremental shuttle walk exercise tests. Energy expenditure was calculated during each exercise test using the physiologic activity monitor and compared to a validated exhaled breath metabolic system. Test-retest reproducibility of physiologic activity monitor during the walking tests was comparable to an exhaled breath metabolic system. Physiologic sensor data significantly improved the explained variance in energy expenditure determination (r 2 = 0.88) compared to accelerometry data alone (r 2 = 0.68). This physiologic activity monitor provides a valid and reproducible estimate of energy expenditure during slow to moderate paced walking in a laboratory setting and represents an objective method to assess activity in COPD subjects.
Aviation, space, and environmental medicine, 1998
We sought to describe changes in spirometric variables and lung volume subdivisions in healthy su... more We sought to describe changes in spirometric variables and lung volume subdivisions in healthy subjects and patients with chronic obstructive pulmonary disease (COPD) during moderate acute hypobaric hypoxia as occurs during air travel. We further questioned whether changes in lung function may associate with reduced maximum ventilation or worsened arterial blood gases. Ambulatory patients with COPD and healthy adults comprised the study populations (n = 27). We obtained baseline measurements of spirometry, lung volumes and arterial blood gases from each subject at sea level and repeated measurements during altitude exposure to 8000 ft (2438 m) above sea level in a man-rated hypobaric chamber. Six COPD patients and three healthy subjects had declines in FVC during altitude exposure greater than the 95% confidence interval (CI) for expected within day variability (p < 0.05). Average forced vital capacity (FVC) declined by 0.123 +/- 0.254 L (mean +/- SD; 95% CI = -0.255, -0.020; p &...
B67. EXERCISE ASSESSMENT IS CRITICAL IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE, 2010
Page 1. / Thematic Poster Session / B67 EXERCISE ASSESSMENT IS CRITICAL IN CHRONIC OBSTRUCTIVE PU... more Page 1. / Thematic Poster Session / B67 EXERCISE ASSESSMENT IS CRITICAL IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE Monday, May 17/8:15 AM-4:00 PM / Area K, Hall G (First Level), Morial Convention Center ...
CHEST Journal, 2007
The current recommendations of 8 to 12 min for the optimal targeted duration of symptom-limited m... more The current recommendations of 8 to 12 min for the optimal targeted duration of symptom-limited maximal cardiopulmonary exercise testing (CPET) to attain maximal oxygen consumption are based on results from healthy individuals and may not be applicable to patients with severe COPD. We aimed to determine the optimal duration for a CPET to attain the peak oxygen consumption (VO2peak) in a group of patients with severe COPD using different carefully conducted workload protocols. We studied 11 subjects with severe COPD (mean FEV1, 32% predicted; 95% confidence interval [CI], 27 to 38% predicted). They completed four incremental, symptom-limited exercise tests on a cycle ergometer using four protocols (4, 8, and 16 W/min continuous ramp protocols, and 8 W/min step protocol) using a randomized double-blind design. The mean duration of these 44 tests was 6.3 min (95% CI, 5.0 to 9.0 min). The duration of the exercise tests differed significantly for the protocols used, as follows: 16-W ramp protocol, 4.0 min (95% CI, 3.0 to 5.1 min); 8-W ramp protocol, 6.6 min (95% CI, 5.0 to 9.0 min); 8-W step protocol, 6.0 min (95% CI, 4.0 to 8.0 min); and 4-W ramp protocol, 8.7 min (95% CI, 4.4 to 13.0 min; p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). The maximal workload significantly increased as the ramp slope increased from 4 to 8 to 16 W/min (maximal workload, 35.6 vs 50.7 vs 64.3 W, respectively; p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). Maximal minute ventilation, heart rate, Borg ratings, and VO2 peak, were not different among the four protocols. No differences were found between the ramp and step protocols. In patients with severe COPD (Global Initiative for Chronic Obstructive Lung Disease stages III-IV), a targeted duration of 5 to 9 min for a CPET appears to be more appropriate than the 8 to 12 min proposed in the current guidelines. Maximal workload, in contrast to VO2peak, is highly dependent on the ramp incrementation rate.
American journal of …, 2003
A37. COPD COMORBIDITIES, 2009
Journal of speech, language, and hearing research : JSLHR, Jan 11, 2015
The larynx has a dual role in the regulation of gas flow into and out of the lungs while also est... more The larynx has a dual role in the regulation of gas flow into and out of the lungs while also establishing resistance required for vocal fold vibration. This study assessed reciprocal relations between phonatory functions - specifically phonatory laryngeal airway resistance (Rlaw) - and respiratory homeostasis during states of ventilatory gas perturbations. Twenty-four healthy women performed phonatory tasks while exposed to induced hypercapnia (high carbon dioxide [CO2]), hypocapnia (low CO2) and normal breathing (eupnea). Effects of gas perturbations on Rlaw were investigated as were the reciprocal effects of Rlaw modulations on respiratory homeostasis. Rlaw remained stable despite manipulations of inspired gas concentrations. In contrast, end-tidal carbon dioxide (PetCO2) levels increased significantly during all phonatory tasks. Thus, for the conditions tested, Rlaw did not adjust to accommodate ventilatory needs, as predicted. Rather, stable Rlaw was spontaneously accomplished ...
Copd Journal of Chronic Obstructive Pulmonary Disease, Mar 24, 2015
Six-minute walk testing (6MWT) and cardiopulmonary exercise testing (CPX) are used to evaluate im... more Six-minute walk testing (6MWT) and cardiopulmonary exercise testing (CPX) are used to evaluate impairment in emphysema. However, the extent of impairment in these tests as well as the correlation of these tests with each other and lung function in advanced emphysema is not well characterized. During screening for the National Emphysema Treatment Trial, maximum ergometer CPX and 6MWT were performed in 1,218 individuals with severe COPD with an average FEV(1) of 26.9 +/- 7.1 % predicted. Predicted values for 6MWT and CPX were calculated from reference equations. Correlation coefficients and multivariable regression models were used to determine the association between lung function, quality of life (QOL) scores, and exercise measures. The two forms of exercise testing were correlated with each other (r = 0.57, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001). However, the impairment of performance on CPX was greater than on the 6MWT (27.6 +/- 16.8 vs. 67.9 +/- 18.9 % predicted). Both exercise tests had similar correlation with measures of QOL, but maximum exercise capacity was better correlated with lung function measures than 6-minute walk distance. After adjustment, 6MWD had a slightly greater association with total SGRQ score than maximal exercise (effect size 0.37 +/- 0.04 vs. 0.25 +/- 0.03 %predicted/unit). Despite advanced emphysema, patients are able to maintain 6MWD to a greater degree than maximum exercise capacity. Moreover, the 6MWT may be a better test of functional capacity given its greater association with QOL measures whereas CPX is a better test of physiologic impairment.
American Journal of Respiratory and Critical Care Medicine, Dec 20, 2012
The 6-minute walk test is used in clinical practice and clinical trials of lung diseases; however... more The 6-minute walk test is used in clinical practice and clinical trials of lung diseases; however, it is not clear whether replicate tests need to be performed to assess performance. Furthermore, little is known about the impact of walking course layout on test performance. We conducted 6-minute walks on 761 patients with severe emphysema (mean +/- SD FEV1% predicted = 26.3 +/- 7.2) who were participants in the National Emphysema Treatment Trial. Four hundred seventy participants had repeated walks on a separate day. The second test was improved by an average of 7.0 +/- 15.2% (66.1 +/- 146 feet, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001, by paired t test), with an intraclass correlation coefficient of 0.88 between days. The course layout had an effect on the distance walked. Participants tested on continuous (circular or oval) courses had a 92.2-foot longer walking distance than those tested on straight (out and back) courses. Course length had no significant effect on walking distance. The training effect found in these patients with severe emphysema is less than in previous reports of patients with chronic obstructive pulmonary disease. Furthermore, the layout of the track may influence the 6-minute walk performance.
American Journal of Respiratory and Critical Care Medicine, 2016
Lower forced expiratory volume in one-second (FEV1) is associated with increased prevalence of at... more Lower forced expiratory volume in one-second (FEV1) is associated with increased prevalence of atherosclerosis, however, causal mechanisms remain elusive. To determine if systemic endothelial dysfunction mediates the association between reduced FEV1 and increased atherosclerosis. Brachial artery endothelial function, pulmonary function, coronary artery calcium, and carotid plaque were assessed in 231 SCCOR study participants, while peripheral arterial endothelial function, pulmonary function, and coronary artery calcium were assessed in 328 HeartSCORE study participants. Lower FEV1 was independently associated with increased atherosclerosis in both cohorts (per 25% lower % predicted FEV1: OR=1.76, 95% CI 1.30-2.40, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001 for carotid plaque in SCCOR participants and OR=1.35, 95% CI 1.02-1.77, p=0.03 for coronary artery calcium in HeartSCORE participants). Similarly, reduced endothelial function was independently associated with increased atherosclerosis in both cohorts (per standard-deviation lower endothelial function: OR=1.30, 95% CI 1.01-1.67, p=0.04 for carotid plaque in SCCOR participants; and OR=1.38, 95% CI 1.09-1.76, p=0.008 and OR=1.41, 95% CI 1.07-1.86, p=0.01 for coronary artery calcium in SCCOR and HeartSCORE participants, respectively). However, there was no association between endothelial dysfunction and FEV1, FEV1/FVC, low-attenuation area/visual emphysema, and diffusing capacity in SCCOR participants, and between endothelial dysfunction and FEV1 or FEV1/FVC in HeartSCORE participants (all p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;0.05). Adjusting the association between FEV1 and atherosclerosis for endothelial dysfunction had no impact. Endothelial dysfunction does not mediate the association between airflow limitation and atherosclerosis. Instead, airflow limitation and endothelial dysfunction appear to be unrelated and mutually independent predictors of atherosclerosis.
The New England Journal of Medicine, Apr 1, 1996
Pulmonary function may improve after surgical resection of the most severely affected lung tissue... more Pulmonary function may improve after surgical resection of the most severely affected lung tissue (lung-reduction surgery) in patients with diffuse emphysema. The basic mechanisms responsible for the improvement, however, are not known. We studied 20 patients with diffuse emphysema before and at least three months after either a unilateral or a bilateral lung-reduction procedure. Clinical benefit was assessed by measurement of the six-minute walking distance and the transitional-dyspnea index, which is a subjective rating of the change from base line in functional impairment and the threshold for effort- and task- dependent dyspnea. Pressure-volume relations in the lungs were measured with static expiratory esophageal-balloon techniques, and right ventricular systolic function was assessed by echocardiography. The patients had significant improvement in the transitional-dyspnea index after surgery (P<0.001). The mean (+/-SD) coefficient of retraction, an indicator of elastic recoil of the lung, improved (from 1.3+/-0.6 cm of water per liter before surgery to 1.8+/-0.8 after, P<0.001). Sixteen patients with increased elastic recoil had a greater increase in the distance walked in six minutes than the other four patients, in whom recoil did not increase (P=0.02). The improved lung recoil led to disproportionate decreases in residual volume as compared with total lung capacity (16 percent vs. 6 percent), but the decreases in both values were significant (P<0.001). Forced expiratory volume in one second increased (from 0.87+/-0.36 to 1.11+/-0.45 liters, P<0.001). End-expiratory esophageal pressure also decreased (P=0.002). These improvements in lung mechanics led to a decrease in arterial partial pressure of carbon dioxide form 42+/-6 to 38+/-5 mm Hg (P=0.006). Furthermore, the fractional change in right ventricular area, an indicator of systolic function, increased from 0.33+/-0.11 to 0.38+/-0.010 (P=0.02). Lung-reduction surgery can produce increases in the elastic recoil of the lung in patients with diffuse emphysema, leading to short-term improvement in dyspnea and exercise tolerance.
D68. PULMONARY VASCULAR DISEASES: CLINICAL CASES, 2012
A42. CHRONIC OBSTRUCTIVE PULMONARY DISEASE PHENOTYPES, 2010
COPD: Journal of Chronic Obstructive Pulmonary Disease, 2013
American Journal of Respiratory and Critical Care Medicine, 2010
Rationale: Before the introduction of combination antiretroviral (ARV) therapy, patients infected... more Rationale: Before the introduction of combination antiretroviral (ARV) therapy, patients infected with HIV had an increased prevalence of respiratory symptoms and lung function abnormalities. The prevalence and exact phenotype of pulmonary abnormalities in the current era are unknown. In addition, these abnormalities may be underdiagnosed. Objectives: Our objective was to determine the current burden of respiratory symptoms, pulmonary function abnormalities, and associated risk factors in individuals infected with HIV. Methods: Cross-sectional analysis of 167 participants infected with HIV who underwent pulmonary function testing. Measurements and Main Results: Respiratory symptoms were present in 47.3% of participants and associated with intravenous drug use (odds ratio [OR] 3.64; 95% confidence interval [CI], 1.32-10.046; P 5 0.01). Only 15% had previous pulmonary testing. Pulmonary function abnormalities were common with 64.1% of participants having diffusion impairment and 21% having irreversible airway obstruction. Diffusion impairment was independently associated with ever smoking (OR 2.46; 95% CI, 1.16-5.21; P 5 0.02) and Pneumocystis pneumonia prophylaxis (OR 2.94; 95% CI, 1.10-7.86; P 5 0.01), whereas irreversible airway obstruction was independently associated with pack-years smoked (OR 1.03 per pack-year; 95% CI, 1.01-1.05; P , 0.01), intravenous drug use (OR 2.87; 95% CI, 1.15-7.09; P 5 0.02), and the use of ARV therapy (OR 6.22; 95% CI, 1.19-32.43; P 5 0.03). Conclusions: Respiratory symptoms and pulmonary function abnormalities remain common in individuals infected with HIV. Smoking and intravenous drug use are still important risk factors for pulmonary abnormalities, but ARV may be a novel risk factor for irreversible airway obstruction. Obstructive lung disease is likely underdiagnosed in this population.
COPD: Journal of Chronic Obstructive Pulmonary Disease, 2007
There is increasing interest in the objective measurement of physical activity in chronic obstruc... more There is increasing interest in the objective measurement of physical activity in chronic obstructive pulmonary disease (COPD) patients due to the close relationship between physical activity level, health, disability and mortality. We aimed to (a) determine the validity and reproducibility of an activity monitor that integrates accelerometry with multiple physiologic sensors in the determination of energy expenditure in COPD subjects and (b) to document the independent contribution of the additional physiologic sensors to accelerometry measures in improving true energy expenditure determination. Eight subjects (4 male, FEV 1 56.4 ± 14.1%, RV 145.0 ± 75.7%) performed 2 separate 6-minute walk and 2 incremental shuttle walk exercise tests. Energy expenditure was calculated during each exercise test using the physiologic activity monitor and compared to a validated exhaled breath metabolic system. Test-retest reproducibility of physiologic activity monitor during the walking tests was comparable to an exhaled breath metabolic system. Physiologic sensor data significantly improved the explained variance in energy expenditure determination (r 2 = 0.88) compared to accelerometry data alone (r 2 = 0.68). This physiologic activity monitor provides a valid and reproducible estimate of energy expenditure during slow to moderate paced walking in a laboratory setting and represents an objective method to assess activity in COPD subjects.
COPD: Journal of Chronic Obstructive Pulmonary Disease, 2007
There is increasing interest in the objective measurement of physical activity in chronic obstruc... more There is increasing interest in the objective measurement of physical activity in chronic obstructive pulmonary disease (COPD) patients due to the close relationship between physical activity level, health, disability and mortality. We aimed to (a) determine the validity and reproducibility of an activity monitor that integrates accelerometry with multiple physiologic sensors in the determination of energy expenditure in COPD subjects and (b) to document the independent contribution of the additional physiologic sensors to accelerometry measures in improving true energy expenditure determination. Eight subjects (4 male, FEV 1 56.4 ± 14.1%, RV 145.0 ± 75.7%) performed 2 separate 6-minute walk and 2 incremental shuttle walk exercise tests. Energy expenditure was calculated during each exercise test using the physiologic activity monitor and compared to a validated exhaled breath metabolic system. Test-retest reproducibility of physiologic activity monitor during the walking tests was comparable to an exhaled breath metabolic system. Physiologic sensor data significantly improved the explained variance in energy expenditure determination (r 2 = 0.88) compared to accelerometry data alone (r 2 = 0.68). This physiologic activity monitor provides a valid and reproducible estimate of energy expenditure during slow to moderate paced walking in a laboratory setting and represents an objective method to assess activity in COPD subjects.
Aviation, space, and environmental medicine, 1998
We sought to describe changes in spirometric variables and lung volume subdivisions in healthy su... more We sought to describe changes in spirometric variables and lung volume subdivisions in healthy subjects and patients with chronic obstructive pulmonary disease (COPD) during moderate acute hypobaric hypoxia as occurs during air travel. We further questioned whether changes in lung function may associate with reduced maximum ventilation or worsened arterial blood gases. Ambulatory patients with COPD and healthy adults comprised the study populations (n = 27). We obtained baseline measurements of spirometry, lung volumes and arterial blood gases from each subject at sea level and repeated measurements during altitude exposure to 8000 ft (2438 m) above sea level in a man-rated hypobaric chamber. Six COPD patients and three healthy subjects had declines in FVC during altitude exposure greater than the 95% confidence interval (CI) for expected within day variability (p < 0.05). Average forced vital capacity (FVC) declined by 0.123 +/- 0.254 L (mean +/- SD; 95% CI = -0.255, -0.020; p &...
B67. EXERCISE ASSESSMENT IS CRITICAL IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE, 2010
Page 1. / Thematic Poster Session / B67 EXERCISE ASSESSMENT IS CRITICAL IN CHRONIC OBSTRUCTIVE PU... more Page 1. / Thematic Poster Session / B67 EXERCISE ASSESSMENT IS CRITICAL IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE Monday, May 17/8:15 AM-4:00 PM / Area K, Hall G (First Level), Morial Convention Center ...
CHEST Journal, 2007
The current recommendations of 8 to 12 min for the optimal targeted duration of symptom-limited m... more The current recommendations of 8 to 12 min for the optimal targeted duration of symptom-limited maximal cardiopulmonary exercise testing (CPET) to attain maximal oxygen consumption are based on results from healthy individuals and may not be applicable to patients with severe COPD. We aimed to determine the optimal duration for a CPET to attain the peak oxygen consumption (VO2peak) in a group of patients with severe COPD using different carefully conducted workload protocols. We studied 11 subjects with severe COPD (mean FEV1, 32% predicted; 95% confidence interval [CI], 27 to 38% predicted). They completed four incremental, symptom-limited exercise tests on a cycle ergometer using four protocols (4, 8, and 16 W/min continuous ramp protocols, and 8 W/min step protocol) using a randomized double-blind design. The mean duration of these 44 tests was 6.3 min (95% CI, 5.0 to 9.0 min). The duration of the exercise tests differed significantly for the protocols used, as follows: 16-W ramp protocol, 4.0 min (95% CI, 3.0 to 5.1 min); 8-W ramp protocol, 6.6 min (95% CI, 5.0 to 9.0 min); 8-W step protocol, 6.0 min (95% CI, 4.0 to 8.0 min); and 4-W ramp protocol, 8.7 min (95% CI, 4.4 to 13.0 min; p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). The maximal workload significantly increased as the ramp slope increased from 4 to 8 to 16 W/min (maximal workload, 35.6 vs 50.7 vs 64.3 W, respectively; p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). Maximal minute ventilation, heart rate, Borg ratings, and VO2 peak, were not different among the four protocols. No differences were found between the ramp and step protocols. In patients with severe COPD (Global Initiative for Chronic Obstructive Lung Disease stages III-IV), a targeted duration of 5 to 9 min for a CPET appears to be more appropriate than the 8 to 12 min proposed in the current guidelines. Maximal workload, in contrast to VO2peak, is highly dependent on the ramp incrementation rate.
American journal of …, 2003
A37. COPD COMORBIDITIES, 2009
Journal of speech, language, and hearing research : JSLHR, Jan 11, 2015
The larynx has a dual role in the regulation of gas flow into and out of the lungs while also est... more The larynx has a dual role in the regulation of gas flow into and out of the lungs while also establishing resistance required for vocal fold vibration. This study assessed reciprocal relations between phonatory functions - specifically phonatory laryngeal airway resistance (Rlaw) - and respiratory homeostasis during states of ventilatory gas perturbations. Twenty-four healthy women performed phonatory tasks while exposed to induced hypercapnia (high carbon dioxide [CO2]), hypocapnia (low CO2) and normal breathing (eupnea). Effects of gas perturbations on Rlaw were investigated as were the reciprocal effects of Rlaw modulations on respiratory homeostasis. Rlaw remained stable despite manipulations of inspired gas concentrations. In contrast, end-tidal carbon dioxide (PetCO2) levels increased significantly during all phonatory tasks. Thus, for the conditions tested, Rlaw did not adjust to accommodate ventilatory needs, as predicted. Rather, stable Rlaw was spontaneously accomplished ...
Copd Journal of Chronic Obstructive Pulmonary Disease, Mar 24, 2015
Six-minute walk testing (6MWT) and cardiopulmonary exercise testing (CPX) are used to evaluate im... more Six-minute walk testing (6MWT) and cardiopulmonary exercise testing (CPX) are used to evaluate impairment in emphysema. However, the extent of impairment in these tests as well as the correlation of these tests with each other and lung function in advanced emphysema is not well characterized. During screening for the National Emphysema Treatment Trial, maximum ergometer CPX and 6MWT were performed in 1,218 individuals with severe COPD with an average FEV(1) of 26.9 +/- 7.1 % predicted. Predicted values for 6MWT and CPX were calculated from reference equations. Correlation coefficients and multivariable regression models were used to determine the association between lung function, quality of life (QOL) scores, and exercise measures. The two forms of exercise testing were correlated with each other (r = 0.57, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001). However, the impairment of performance on CPX was greater than on the 6MWT (27.6 +/- 16.8 vs. 67.9 +/- 18.9 % predicted). Both exercise tests had similar correlation with measures of QOL, but maximum exercise capacity was better correlated with lung function measures than 6-minute walk distance. After adjustment, 6MWD had a slightly greater association with total SGRQ score than maximal exercise (effect size 0.37 +/- 0.04 vs. 0.25 +/- 0.03 %predicted/unit). Despite advanced emphysema, patients are able to maintain 6MWD to a greater degree than maximum exercise capacity. Moreover, the 6MWT may be a better test of functional capacity given its greater association with QOL measures whereas CPX is a better test of physiologic impairment.
American Journal of Respiratory and Critical Care Medicine, Dec 20, 2012
The 6-minute walk test is used in clinical practice and clinical trials of lung diseases; however... more The 6-minute walk test is used in clinical practice and clinical trials of lung diseases; however, it is not clear whether replicate tests need to be performed to assess performance. Furthermore, little is known about the impact of walking course layout on test performance. We conducted 6-minute walks on 761 patients with severe emphysema (mean +/- SD FEV1% predicted = 26.3 +/- 7.2) who were participants in the National Emphysema Treatment Trial. Four hundred seventy participants had repeated walks on a separate day. The second test was improved by an average of 7.0 +/- 15.2% (66.1 +/- 146 feet, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001, by paired t test), with an intraclass correlation coefficient of 0.88 between days. The course layout had an effect on the distance walked. Participants tested on continuous (circular or oval) courses had a 92.2-foot longer walking distance than those tested on straight (out and back) courses. Course length had no significant effect on walking distance. The training effect found in these patients with severe emphysema is less than in previous reports of patients with chronic obstructive pulmonary disease. Furthermore, the layout of the track may influence the 6-minute walk performance.
American Journal of Respiratory and Critical Care Medicine, 2016
Lower forced expiratory volume in one-second (FEV1) is associated with increased prevalence of at... more Lower forced expiratory volume in one-second (FEV1) is associated with increased prevalence of atherosclerosis, however, causal mechanisms remain elusive. To determine if systemic endothelial dysfunction mediates the association between reduced FEV1 and increased atherosclerosis. Brachial artery endothelial function, pulmonary function, coronary artery calcium, and carotid plaque were assessed in 231 SCCOR study participants, while peripheral arterial endothelial function, pulmonary function, and coronary artery calcium were assessed in 328 HeartSCORE study participants. Lower FEV1 was independently associated with increased atherosclerosis in both cohorts (per 25% lower % predicted FEV1: OR=1.76, 95% CI 1.30-2.40, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001 for carotid plaque in SCCOR participants and OR=1.35, 95% CI 1.02-1.77, p=0.03 for coronary artery calcium in HeartSCORE participants). Similarly, reduced endothelial function was independently associated with increased atherosclerosis in both cohorts (per standard-deviation lower endothelial function: OR=1.30, 95% CI 1.01-1.67, p=0.04 for carotid plaque in SCCOR participants; and OR=1.38, 95% CI 1.09-1.76, p=0.008 and OR=1.41, 95% CI 1.07-1.86, p=0.01 for coronary artery calcium in SCCOR and HeartSCORE participants, respectively). However, there was no association between endothelial dysfunction and FEV1, FEV1/FVC, low-attenuation area/visual emphysema, and diffusing capacity in SCCOR participants, and between endothelial dysfunction and FEV1 or FEV1/FVC in HeartSCORE participants (all p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;0.05). Adjusting the association between FEV1 and atherosclerosis for endothelial dysfunction had no impact. Endothelial dysfunction does not mediate the association between airflow limitation and atherosclerosis. Instead, airflow limitation and endothelial dysfunction appear to be unrelated and mutually independent predictors of atherosclerosis.
The New England Journal of Medicine, Apr 1, 1996
Pulmonary function may improve after surgical resection of the most severely affected lung tissue... more Pulmonary function may improve after surgical resection of the most severely affected lung tissue (lung-reduction surgery) in patients with diffuse emphysema. The basic mechanisms responsible for the improvement, however, are not known. We studied 20 patients with diffuse emphysema before and at least three months after either a unilateral or a bilateral lung-reduction procedure. Clinical benefit was assessed by measurement of the six-minute walking distance and the transitional-dyspnea index, which is a subjective rating of the change from base line in functional impairment and the threshold for effort- and task- dependent dyspnea. Pressure-volume relations in the lungs were measured with static expiratory esophageal-balloon techniques, and right ventricular systolic function was assessed by echocardiography. The patients had significant improvement in the transitional-dyspnea index after surgery (P<0.001). The mean (+/-SD) coefficient of retraction, an indicator of elastic recoil of the lung, improved (from 1.3+/-0.6 cm of water per liter before surgery to 1.8+/-0.8 after, P<0.001). Sixteen patients with increased elastic recoil had a greater increase in the distance walked in six minutes than the other four patients, in whom recoil did not increase (P=0.02). The improved lung recoil led to disproportionate decreases in residual volume as compared with total lung capacity (16 percent vs. 6 percent), but the decreases in both values were significant (P<0.001). Forced expiratory volume in one second increased (from 0.87+/-0.36 to 1.11+/-0.45 liters, P<0.001). End-expiratory esophageal pressure also decreased (P=0.002). These improvements in lung mechanics led to a decrease in arterial partial pressure of carbon dioxide form 42+/-6 to 38+/-5 mm Hg (P=0.006). Furthermore, the fractional change in right ventricular area, an indicator of systolic function, increased from 0.33+/-0.11 to 0.38+/-0.010 (P=0.02). Lung-reduction surgery can produce increases in the elastic recoil of the lung in patients with diffuse emphysema, leading to short-term improvement in dyspnea and exercise tolerance.
D68. PULMONARY VASCULAR DISEASES: CLINICAL CASES, 2012
A42. CHRONIC OBSTRUCTIVE PULMONARY DISEASE PHENOTYPES, 2010