REDUCED MECHANICAL EFFICIENCY IN COPD, BUT NORMAL PEAK VO2 WITH SMALL MUSCLE MASS EXERCISE
ABSTRACT We studied 6 patients with COPD (FEV1 = 1.1 ± 0.2 L, 32% of predicted) and 6 age and activity level matched,controls while performing both maximal,bicycle exercise and single leg knee-extensor exercise. Arterial and femoral venous blood sampling, thermodilution blood flow measurements,and needle biopsies allowed the assessment of
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ABSTRACT: Rehabilitants with chronic orthopaedic diseases are assigned to either the traditional or the behaviour-medical rehabilitation approach by consultant physicians of the rehabilitation department within the Deutsche Rentenversicherung Bund (German pension insurance agency). The clinical relevance of this assignment was evaluated at the Rehazentrum Bad Pyrmont-Klinik Weser within a randomised controlled trial. In a sample of 363 rehabilitants the agreement of consultant physicians with the ratings of physicians and psychologists in the clinic was analyzed. We also tested whether rehabilitants treated in their assigned approach benefit more from the treatment than patients who by randomisation were not treated in their assigned approach. Results indicate that psychiatric comorbidity frequently is taken into consideration as a decision-making criterion in the assignment made by the consultant physicians. However, there is only little agreement between the assignment by consultant physicians and the ratings by treating physicians and psychologists. Further, rehabilitants treated in their assigned approach did not benefit more from the treatment than patients who due to randomisation had not been treated in their assigned approach but in the other. Therefore, the procedure applied so far for assigning rehabilitants to either the traditional or the multidisciplinary rehabilitation approach is not sufficiently valid. Concluding, implications for the modification of assignment criteria are discussed.Die Rehabilitation 01/2008; 46(6):323-32. · 0.71 Impact Factor
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ABSTRACT: A work-related orientation within medical rehabilitation represents concepts with a stronger focus on the patient's individual vocational requirements and is based on different vocationally-orientated strategies of treatment. "Medical Occupational Orientation" ("Medizinisch-berufliche Orientierung", MBO), the model of Klinik Niedersachsen in Bad Nenndorf, places Functional Capacity Evaluation according to Susan Isernhagen (EFL) at the centre of rehabilitation diagnostics and therapy. This study investigates the effects of the MBO model relative to activities and vocational participation of patients with musculoskeletal disorders faced with vocational problems and on management at the interface between medical and vocational rehabilitation. Presented are findings of a randomized follow-up study aimed at evaluating the MBO model. A total of 494 patients of LVA Westfalen, a regional insurance agency, took part. A need for MBO was diagnosed for 222 patients. These patients were randomly assigned either to the MBO model of treatment (experimental group --> U[+]) or to the conventional medical treatment (control group --> K[+]). Patients without a need for MBO (U[-], K[-]) were treated likewise. The written questionings took place at the beginning (t (1)) and end of rehabilitation (t (2)), as well as six (t (3)) and twelve months (t (4)) after the patients' discharge. Currently, the results are based on the 6-month follow-up. Concerning the activities, an MBO-related effect in the experimental group (U[+]) has been found for the Pain Disability Index (PDI), effect sizes being d (u+) = 0.82; d (k+) = 0.17. The risk of unemployment six months after rehabilitation is decreased for MBO(+) patients who participated in the MBO model. In addition, the clinic can make effective prognosis concerning subsequent participation in vocational rehabilitation for both experimental groups (U[+], U[-]). Established for the first time in a randomized controlled trial, the findings presented show that patients with musculoskeletal disorders who are faced with particular vocational problems will achieve significantly better results concerning activities and vocational reintegration if their medical rehabilitation had been based upon an EFL-centred MBO approach.Die Rehabilitation 06/2006; 45(3):161-71. · 0.71 Impact Factor
- American Journal of Respiratory and Critical Care Medicine 07/2006; 173(12):1390-413. · 11.04 Impact Factor
REDUCED MECHANICAL EFFICIENCY IN COPD,
BUT NORMAL PEAK VO2 WITH SMALL MUSCLE MASS EXERCISE
"This article has an online data supplement, which is accessible from this issue's table of content
online at www.atsjournals.com"
Authors: Russell S. Richardson
Bryan T. Leek
Timothy P. Gavin
Luke J. Haseler
Sundar R.D. Mudaliar
Andrew L. Ries
Odile D. Mathieu-Costello
Peter D. Wagner
Institution:Department of Medicine,
University of California San Diego,
La Jolla, CA 92093.
Dr. R.S. Richardson
Department of Medicine, 0623
University of California San Diego,
La Jolla, CA 92093-0623
TEL: (858) 534-9841
FAX: (858) 534-4812
Running Head: COPD and skeletal muscle function.
Word count: 7,176
Subject Category Number: 53 COPD: Pathophysiology
Copyright (C) 2003 by the American Thoracic Society.
AJRCCM Articles in Press. Published on September 18, 2003 as doi:10.1164/rccm.200305-627OC
We studied 6 patients with COPD (FEV1 = 1.1 ± 0.2 L, 32% of predicted) and 6 age and
activity level matched controls while performing both maximal bicycle exercise and
single leg knee-extensor exercise. Arterial and femoral venous blood sampling,
thermodilution blood flow measurements and needle biopsies allowed the assessment of
muscle O2 supply, utilization and structure. Maximal work rates and single leg maximal
oxygen consumption (controls = 0.63 ± 0.1; COPD = 0.37 ± 0.1 l/min) were significantly
greater in the control group during bicycle exercise. During knee-extensor exercise this
difference in maximal oxygen consumption disappeared, while maximal work capacity
was reduced (flywheel resistance: controls = 923 ± 198; COPD = 612 ± 81 g) revealing a
significantly reduced mechanical efficiency (work per unit O2 consumed) with COPD.
The patients had an elevated number of less efficient Type II muscle fibers while muscle
fiber cross sectional areas, capillarity and mitochondrial volume density were not
different between the groups. Therefore although metabolic capacity per se is unchanged,
fiber type differences associated with COPD may account for the reduced muscular
mechanical efficiency that becomes clearly apparent during knee-extensor exercise, when
muscle is no longer overshadowed by the decrement in lung function.
Word Count 200
KEY WORDS: lung disease, Oxygen consumption, blood flow, fiber type, quadriceps
Although researchers have recently focused their attention on the potential involvement
of skeletal muscle in the pathophysiology of COPD (7, 28, 32, 35, 41) there is currently no
accord on this matter (1). An issue that has clouded conclusions is the difference between
skeletal muscle dysfunction and disuse (52). Certainly, patients with COPD experience
locomotor muscle disuse, promoted by the dyspnea that accompanies exercise in this condition.
However, should simply deconditioned skeletal muscle be considered dysfunctional? The
tendency to answer yes to this question has been promoted by studies that magnify the
differences in COPD skeletal muscle by comparisons with relatively physically active control
subjects (32, 33, 52, 67). Thus, the selection of appropriately inactive controls becomes an
essential component of the experimental design of research focused on the assessment of skeletal
muscle function and COPD.
Additional support for the concept of dysfunctional muscle in COPD has been provided
by the regular use of whole body exercise, such as cycling, to evaluate muscle function (32, 35,
64). The use of a large muscle mass exercise paradigm, in COPD patients, may shroud peripheral
muscle limitations by the attainment of a patient’s reduced ventilation ceiling, before truly taxing
the locomotor muscles. Ideally, to study muscle function itself in COPD, the amount of muscle
recruited should be small enough that the patient can achieve maximal muscular work before the
influence of central ventilatory limitations.
The single leg knee-extensor exercise model (3), allows the measurement of O2 supply
and utilization to a known mass of active muscle (53) under conditions of limited ventilatory
demand, and thus is an ideal exercise paradigm with which to study the skeletal muscle of
patients with COPD (59). The ability to monitor muscle O2 supply in this paradigm is essential,
because without this, metabolic differences may be the consequence of either intrinsic muscle
dysfunction or the normal response of healthy (even if detrained) muscle to reduced O2 supply.
Consequently, this study was designed to assess skeletal muscle function in patients with
COPD during both cycle and single leg knee-extensor exercise in comparison to healthy control
subjects that were well-matched, both in terms of physical activity and physical characteristics.
The purpose of this study was to test the following hypotheses: 1) during cycle exercise the
skeletal muscle of patients with COPD will appear dysfunctional in comparison to controls in
terms of maximal work rate, muscle blood flow, and VO2, while 2) during single leg knee-
extensor exercise the skeletal muscle of patients with COPD will have a more similar
physiological response to that of the control subjects. This work has been previously published in
abstract form (51).
Subjects: Six patients with COPD (FEV1= 1.1 ±0.2, 32 ± 5% predicted )(11) and six
healthy age, weight and activity matched controls volunteered according to the University of
California San Diego, Human Research Protection Program requirements. Controls were
determined to be sedentary and the majority of the COPD patients had completed the UCSD
Pulmonary Rehabilitation Program (within 8-24 months), but did not differ from the controls in
terms of current physical activity (13, 23, 70). Subject characteristics are presented in Table 1.
Exercise models: Two exercise modalities were employed in this study the first being
conventional bicycle ergometry performed on an electrically braked bike (Excalibur, Quinton
Instruments Company, Holland). Cadence was self selected, but for most subjects fell between
60-80 revolutions per minute. The second exercise paradigm was knee-extensor exercise, that
limits muscular work to the quadriceps of one leg (3, 53, 58), this was performed with subjects
reclined on a padded chair with the knee-extensor exercise ergometer placed in front of them
(illustrated in Reference (57)) (see online supplement).
Experimental protocol: Within 1 wk of preliminary familiarization studies, subjects
returned to the laboratory where two catheters (radial artery and left femoral vein) and a
thermocouple (left femoral vein) were emplaced using sterile technique as previously reported
(49, 58)(see online supplement). Blood samples were taken from the arterial and femoral venous
catheters to quantify arterial-venous O2 concentration differences.
Following the catheterization procedures two bouts of graded exercise were performed: 1)
conventional cycle exercise and 2) single leg knee-extensor exercise. The order of these exercise
bouts across subjects was balanced to avoid potential ordering effects. For each exercise bout,
the work rate was increased from an unweighted warm-up to the previously determined