Rick Carter

Criterion validity of the Duke Activity Status Index for assessing functional capacity in patients with chronic obstructive pulmonary disease

PURPOSE This study evaluated the concurrent criterion validity of the Duke Activity Status Index (DASI) with respect to standard physiologic work capacity indices in patients with chronic obstructive pulmonary disease (COPD) and compared its performance with similar surrogates. METHODS 119 patients with moderate to severe COPD (86 men, 33 women) completed medical and smoking histories, physical examination, pulmonary function testing (PFT), cycle ergometry (CE), arm ergometry (AE), and 6-minute walk distance (6MWD), DASI, the Sickness Impact Profile-68 (SIP-68) and the Chronic Respiratory Disease Questionnaire (CRDQ). Correlation methods were used to assess the validity of the potential surrogates DASI and the domain scores for SIP-68 and CRDQ, with the standards CE, AE, PFT, and 6MWD (as a standard). RESULTS The mean DASI score was 33.4 +/- 13.0. Significant Pearson correlations (P <.01) were observed between the DASI and PFT outcomes maximum voluntary ventilation (r =.28); peak expiratory flow (r =.21); diffusion capacity of lung for carbon monoxide (r =.30). For CE, the correlations with DASI were oxygen consumption (VO(2))(r =.34); minute ventilation (r =.25); watts (r =.37). For AE, the correlations with DASI were VO(2) (r=.38); watts (r =.47). For 6MWD, the correlation was r =.53. Higher correlations were obtained for the distance completed during the first minute of the 6MWD and ergometric indices as well as DASI scores: watts(AE) (r =.39); VO(2AE) (r =.45); watts(CE) (r =.50); VO(2CE) (r =.44). Correlation coefficients for all SIP-68 and CRDQ domain and total scores were lower than corresponding correlations obtained for the DASI. Regression analysis demonstrated that the DASI and 6MWD were important (P <.05) for predicting VO(2) or work for CE while DASI and SIP range or CRDQ dyspnea entered for AE, when gender, age, BMI, and the FEV1 were forced into the model. In forward stepwise analyses, DASI entered first for AE, and 6MWD entered first for CE. The DASI was selected in 3 of 4 models with R(2) values ranging from.47 to.70. SIP-68 and CRDQ subscores were significant as additional predictors. CONCLUSIONS DASI has high criterion validity for predicting CE and/or AE outcomes in the COPD population. It is warranted in addition to the 6MWD, and its predictive significance and simplicity recommends it over several other self-administered instruments for evaluating functional capacity.

Peak Physiologic Responses to Arm and Leg Ergometry in Male and Female Patients With Airflow Obstruction

STUDY OBJECTIVE To investigate differences in work capacity for the arms and legs in patients with moderate-to-severe COPD. DESIGN Cross-sectional investigation. PATIENTS One hundred twenty-four patients (90 men and 34 women) aged 45 to 81 years with moderate-to-very severe COPD. FEV(1) ranged from 0.70 to 2.79 L/min (FVC, 1.73 to 5.77 L; FEV(1)/FVC, 24 to 69%). All patients were in stable condition at the time of testing and receiving a stable drug regime. MEASUREMENTS Each patient completed a demographic and medical history questionnaire, pulmonary function studies (spirometry, lung volumes, and diffusion capacity), peak exercise ergometry with gas exchange for the arms and legs; they also rated their subjective assessment of perceived dyspnea and extremity fatigue using Borg scores during exercise. RESULTS Patients were of comparable age, with men taller and heavier than women. Smoking history was significantly less for women (47.9 pack-years vs 66.6 pack-years for men) even though each group presented with equivalent age (p > 0.05). Women were less obstructed than men, with FEV(1)/FVC (mean +/- SD) of 46.5 +/- 10.9% vs 40.2 +/- 9.3%, respectively. Ventilatory limitation during exercise was noted for all patients studied. Peak work capacity was greater for men, and leg peak responses were greater than arm values for each gender. As airway obstruction increased, work capacity became more limited. Peak arm work achieved was 38.9 +/- 19.6 W, oxygen uptake (VO(2)) was 903.9 +/- 263.5 mL/min, and minute ventilation (VE) was 33.7 +/- 9.5 L. Peak leg work value was 62.9 +/- 24.8 W, VO(2) was 1,091.4 +/- 321.5 mL/min, and VE was 39.3 +/- 12.0 L. Hence, arm values were 62%, 83%, and 85% of the measured leg values, respectively. Dyspnea and extremity effort scores were similar for men and women, and for arms and legs. Regression analysis was used to derive prediction equations for arm work from measured leg ergometry testing. For watts of work, a three-variable model emerged explaining 66% of the variance; VO(2) yielded a four-variable model with 80% of the variance explained; and VE yielded a three-variable model explaining 72% of the variance. CONCLUSION Arm work is reduced by 38% that of the legs, while more modest reductions are noted for VO(2) and VE, suggesting greater mechanical efficiency for leg work as compared to arm work. These data also suggest greater metabolic demand for respiratory muscles and arm ergometry. Dyspnea and extremity Borg scores were equivalent for each modality and level of airway obstruction studied, suggesting that perception plays an important role in limiting exercise, and that a threshold for termination of exercise may exist. Further, peak leg ergometry results can be used with pulmonary function indexes to predict peak arm workload in watts, VO(2), and VE. These data may be used to assist the clinician in prescribing rehabilitation or estimating arm exercise ability when arm testing is unavailable.

Frequency and Correlates of Overweight Status in Adolescent Asthma

Background: Debate exists within the literature concerning whether asthma and obesity are linked as comorbid conditions. Further study is required to understand the relationship between asthma and overweight status, and developmental considerations are an important priority area. Objective: The present study addressed gaps in the existing literature by comparing rates of overweight status among a matched sample of adolescents with and without asthma and by examining correlates of overweight status among youth with asthma. Methods: Rates and correlates of overweight status were compared among a matched cohort of 103 adolescents with asthma, 75 adolescents with asthma characterized by history of a severe acute event, and 92 normal controls. Results: Significantly higher rates of overweight status were found among the asthma groups compared to the control group and to population estimates. Significant correlates for overweight status included younger age and earlier age at asthma diagnosis, suggesting that receiving an asthma diagnoses in early childhood may increase the propensity for weight gain. Conclusion: Asthma and obesity are problematic comorbid conditions, and specialized obesity prevention programs may be particularly necessary at the onset of a new asthma diagnosis. Clinical Implications: Identifying and addressing the factors that may contribute to the potential for obesity among youth with asthma are key research and clinical practice priorities.

Exercise training in patients with chronic obstructive pulmonary disease

Most patients with chronic obstructive pulmonary disease (COPD) demonstrate positive responses to exercise conditioning. Dyspnea is reduced and work tolerance is extended with little or no change in pulmonary function noted. Possible explanations for the increased ability to better tolerate exercise and activities of daily living (ADL) after training include: 1) psychological encouragement, 2) improvements in mechanical efficiency, 3) improved cardiovascular conditioning, 4) improved muscle function, 5) biochemical adaptations responsible for reducing glucose utilization, 6) desensitization to dyspnea, and 7) contributions from better self-care. However, not all patients respond positively to exercise conditioning. This may represent differences in patient selection, training approaches, and/or comorbidity issues commonly seen in patients with COPD. Alternatively, the answer may reside in devising an optimal training intensity, duration, and frequency combination for patients with COPD. This is not an easy matter because of the diversity of patients categorized as COPD. We have reviewed these issues from the available data and presented areas where additional research is warranted. What is needed at present is a series of well-controlled studies that focus on identifying and improving training responses in patients with COPD. Secondary to this issue is the long term epidemiologic surveillance of trained patients to document sustained effects.

Long-term continuous positive airway pressure (CPAP) outcomes from a sleep service using limited sleep studies and daycase CPAP titration in the management of obstructive sleep apnoea/hypopnoea syndrome.

Background: Detailed polysomnography (PSG) and overnight continuous positive airway pressure (CPAP) titration as the basis for investigation and treatment of obstructive sleep apnoea/hypopnoea syndrome (OSAHS) incurs high costs from inpatient stays and technician attendance, even when split night studies are employed. Responding to rapidly increasing demand, from 1996 the sleep service at Glasgow Royal Infirmary adopted limited sleep studies and daycase CPAP titration as first line management. Here we describe the outcomes of this service between 1996 and 1999. Methods: Data were collected from prospective records made at follow up by sleep technicians and by casenote review. Results: Results were available for 158 subjects (97.5%) of 162 commenced on CPAP during this period. One hundred and forty-eight (91%) were diagnosed by limited sleep studies and 80 (50%) were diagnosed at home. The median follow up was 23 months (interquartile range (IQR), 13-35). Median use of CPAP in those continuing therapy was 5.3 hours/night (IQR, 3.1 to 6.5) and 77% were still using CPAP at three years. Only initial low CPAP compliance (< 2 hours/night) significantly predicted early CPAP cessation. In those still on CPAP in 1999, the mean drop in Epworth Sleepiness Scale score was 4.6 points (95% confidence intervals, 3.2 to 6.0). Conclusion: These data from the CPAP population at Glasgow Royal Infirmary provide information on longterm outcomes using a diagnostic protocol based on limited sleep studies and daycase CPAP titration.

Oxygen conserving devices and methodologies.

Collective experience with pulmonary rehabilitation and disease management has shown that patients with lung diseases including COPD and restrictive lung diseases live a longer and more productive quality of life if they can remain active. Patients who require oxygen supplementation but can otherwise be active should have the most portable and non-encumbering systems possible. Oxygen conserving devices have made a high level of portability possible. Small gas, liquid and even some concentrators have replaced the 20 pound E cylinder with 4 and 5 pound systems. In a parallel physiological development, exercise plus oxygen increases the physiological benefits of exercise and thereby enhances the patients ability to function in life. This paper examines available options and their mechanical and physiological foundations.

Oxygen for end-of-life lung cancer care: managing dyspnea and hypoxemia.

Oxygen is commonly prescribed for lung cancer patients with advancing disease. Indications include hypoxemia and dyspnea. Reversal of hypoxemia in some cases will alleviate dyspnea. Oxygen is sometimes prescribed for non-hypoxemic patients to relieve dyspnea. While some patients may derive symptomatic benefit, recent studies demonstrate that compressed room air is just as effective. This raises the question as to whether to continue their oxygen. The most efficacious treatment for dyspnea is pharmacotherapy–particularly opioids. Adjunctive therapies include pursed lips breathing and a fan blowing toward the patient. Some patients may come to require high-flow oxygen. High-flow delivery devices include masks, high-flow nasal oxygen and reservoir cannulas. Each device has advantages and drawbacks. Eventually, it may be impossible or impractical to maintain a SpO2 > 90%. The overall goal in these patients is comfort rather than a target SpO2. It may eventually be advisable to remove continuous oximetry and transition focus to pharmacological management to achieve patient comfort.

Severe Exercise-Induced Hypoxemia

Exercise training is an essential component of pulmonary rehabilitation and is associated with improved function and other important outcomes in persons with chronic lung disease. A subset of pulmonary rehabilitation patients experience hypoxemia that may occur or worsen with exercise. For the purpose of this review, severe exercise-induced hypoxemia is defined as an SpO2 of < 89% during exercise, despite use of supplemental oxygen delivered at up to 6 L/min. There is a paucity of evidence and clinical guidelines that address assessment and management of this important manifestation of chronic lung disease. This review presents background of this topic and suggests strategies for assessment, management, and safety measures for patients with severe exercise-induced hypoxemia.

The Emerging Chronic Obstructive Pulmonary Disease Epidemic: Clinical Impact, Economic Burden, and Opportunities for Disease Management

The incidence and economic impact of chronic obstructive pulmonary disease (COPD) is escalating worldwide and is projected to remain on a positive trajectory for many years to come. At some point in this escalation, COPD may be regarded as a true epidemic. Unfortunately, the incidence among women is escalating more rapidly than in men, reflecting the social anthropology of changing smoking habits. This knowledge, coupled with the fact that the true disease prevalence is under-reported, suggests that we are facing a significant medical and economic crisis. The most preventable risks for COPD continue to be cigarette smoking and exposure to second-hand smoke. This is a particular problem for youth in their formative and critical growth years. Amalgamated with these alarming trends are the decline in air quality, occupational exposure to inhaled pollutants and pro-inflammatory materials, poor nutrition, lack of exercise, and increasing body mass index.There is a lack of patient and family understanding regarding this chronic disease process and its co-morbid conditions. First and foremost, smoking-cessation efforts must be increased, and protection from second-hand smoke needs to be emphasized. Spirometric testing to identify populations at risk and in the early stages of disease should be implemented on a large scale and should trigger implementation of appropriate preventive steps. Disease management processes and strategies used in alliance with educational-, nutritional-, and physical exercise-related interventions may hold the key to altering behavioral patterns of patients and their families. We need to provide patients with simple and definitive interventions that can be self-initiated at the earliest possible time. This may help us to integrate best medical practices early in the disease process. Thus, we can improve bodily function from a systemic perspective, while implementing coordinated disease surveillance and treatment plans for each affected individual. From an economic perspective, financial incentives can be provided by way of shifting costs from disease treatment to disease prevention and health enhancement. When the correct incentives and disease management strategies are embraced, a disease-oriented intervention can ameliorate the devastating impact of COPD on patients and their families while relieving the economic impact of the disease.In summary, numerous stakeholders will need to come together in order to identify and remove barriers for implementation of preventive measures, provide early intervention, modify the disease course, and minimize the economic impact of COPD. Strategies should be developed for populations, as well as individual patients, if we are to adequately address this emerging epidemic.

Improved Methodology for Threshold Detection Studies in Asthmatic Children

Abstract This paper reports the differences between two methodologies for threshold detection of added resistive loads in children and adolescents. The first-generation apparatus utilized a series of laminar flow screens to present various total resistances, while in the second generation the apparatus utilized a servo-controlled cone that occluded an aperture to varying degrees. Protocol modifications in the second generation methodology included forced choice, attentional enhancements, and larger increments of added resistance. Two studies conducted 2 years apart provided data on the first and second generations of methodology. All participants in Study 1 (N = 33) and Study 2 (N = 33) were children with asthma. Subjects were matched for both age and asthma severity. Results showed the methodologic improvements in the second generation to be significant. Tracking and random thresholds were achieved by 85% and 82% of the subjects in Study 2 compared to 76% and 42% in Study 1, respectively. The correlation...