Clinical assessment of peripheral muscle function in patients with

chronic pulmonary disease

Journal presentation Shifa Manhal

Authors and AffiliationsAuthors • Jordi Vilaro, PhD• Roberto Rabinovich, MD• Jose Manuel Gonzalez-deSuso, MD• Thierry Troosters, PhD• Diego Rodriguez, MD• Joan Albert Barbera, MD• Josep Roca, MD

Affiliations• Servei de pneumologia, hospital clinic • Universitat de Barcelona , Spain

Abstract

Objectives :• Correlation of muscle function , muscle mass

and endurance and exercise tolerance in chronic obstructive pulmonary disease.

Abstract

• Design : sixteen COPD patients (FEV1 – 38 ± 15% predicted) and 6

controls underwent magnetic resonance imaging of the thigh, muscle strength and endurance, and exercise tolerance assessments.

AbstractResults:• Six COPD patients presented with reduced thigh mass

(COPDLQ)• 10 patients presented with normal quadriceps mass

(COPDNQ) and all controls had identical mass distribution.

• COPDLQ had lowered muscle function and lowered exercise tolerance than both controls and COPDNQ.

• Muscle strength to muscle mass was similar among COPD patients and controls.

Abstract

Results:• Endurance to muscle mass ratio was lower in COPD

than in controls.• Half time phosphocreatine recovery was also slower

than in controls.

Abstract

Conclusion:• Impaired muscle strength was explained by

reduced muscle mass, but it did not account for abnormal muscle endurance. The latter seems associated to impaired O2 transport /O2 utilization, resulting in altered muscle bioenergetics .

Introduction

ADL, HRQOL and disease prognosis in

COPD patients

Systemic inflammation

Cell hypoxia

Nitroso – redox disequilibrium of the system

muscle disuse

Peripheral muscle

abnormalities

Limited exercise

tolerance

Background • Muscle strength and oxygen uptake kinetics in

COPD patients with preserved muscle mass are comparable with that of healthy sedentary controls.

• Impaired quadriceps strength seen in COPD patients has been explained by reduction of muscle mass.

• Abnormal muscle bioenergetics seem to account for impaired muscle endurance , independently of the amount of muscle mass.

Background

Limitation in o2 transport both at

central and peripheral level

Impaired muscle O2 utilization

Altered muscle bioenergetics in COPD patients

Background • Previous studies of muscle endurance and strength in

COPD suggest that muscle dysfunction as analyzed through strength tests may give only limited information about intrinsic muscle exercise capacity .

• In this study different approaches to assess muscle strength have been analyzed.

• The information from the above approaches have been compared with information obtained from muscle bioenergetics assessed by phosphorus-magnetic resonance spectroscopy (P-NMRS) and exercise tolerance.

Methods

16 COPD patients and 6 healthy

sedentary controls

Pulmonary function test

Muscle function test

Assessment of thigh muscle mass

by magnetic resonance imaging

Exercise testing

Pulmonary Function test• Test performed at rest • Forced spirometry • Lung volume measure • Single breath diffusion capacity

Muscle function test

Muscle function tetst

Isokinetic peak torque (isokin)

Isometric force production

(isome)

One repetition maximum

strength test (RM)

Muscle function test• Isokin and isome measurements were done using isokinetic

dynamometer (cybex 6000)• Isokin peak torque (Nm) was taken as the heighest value of

two trials with five knee extensions at the angular speed of 60 degree/sec each.

• Best isome peak power (N) from three acceptable trials aiming at maximal knee extension/contraction against a static arm lever at 60 degrees was selected.

Muscle function test • RM measured the maximum amount of weight

that can be lifted in a single repetition.• Handgrip strength of the dominant hand using a

handheld dynamometer . Best value of three reproducible maneuvers was used in the analysis.

• Muscle bioenergetics was assessed by P-NMRS using a specially designed cycle ergometer

Assessment of thigh muscle mass by magnetic resonance imaging

• Left leg MRI from the isquio-femoral joint to the inferior femur condyle.

• Calculation of thigh area /volume was performed by a single observer using an image analyzing computer program.

Exercise Testing • Incremental exercise test with cycle

ergometer.• Radial artery cannulation done to all subjects. • Subjects were asked to pedal as much as

possible against an incremental load , until exhaustion .

• A gas analyzer was used to continuously measure breath by breath oxygen consumption(VO2), carbon dioxide production (Vco2), minute ventilation (Ve) and heart rate.

•

Exercise Testing Arterial blood samples were taken every 3

minutes to assess :• Arterial lactate concentration • Oxygen saturation

Dyspnea and leg discomfort were scored at the beginning and the end of the test.

Exercise Testing • Two 6 min walk test were performed by patients in a

corridor of 90m length.• They were asked to walk as far as possible during 6

minutes with standardized encouragement.• The best results from two trials were used for data

analysis.

Statistical analysis

• Students unpaired t test • Pearsons regression analysis • Post HOC • Analysis of variance

Results – study groups • COPD patients showed severe airflow obstruction with

moderate hypoxemia , whereas the control group presented normal lung function.

• In regard to thigh muscle mass index COPDNQ showed identical distribution to the six healthy identical sedentary controls . COPDLQ had a lower MMI in comparison to both COPDNQ and controls.

• COPDLQ showed higher functional impairment than COPDNQ indicating more advanced disease.

• COPD patients as a whole group showed lower exercise tolerance than healthy sedentary controls assessed by incremental cycling exercise and timed walking test.

Results – endurance and strength vs Mass

• Quadriceps endurance was significantly lower in COPDLQ than in COPDNQ. This variable was also lower in the overall COPD group than in controls.

• Muscle strength was lower in COPDLQ than in COPDNQ . Statistically significant difference in muscle strength were also seen between the whole COPD group and controls.

• Difference in muscle strength between controls and COPDNQ were only seen in isome and handgrip measurements.

• Quadriceps isokinetic strength showed significant associations with isometric strength, repetition maximum and handgrip strength.

Results – associations with exercise tolerance

• Significant association between 6MWD and different variables indicating pulmonary and skeletal muscle function.

DISCUSSION• Impairment of muscle strength is a direct consequence of

muscle mass wasting . This phenomenon is explained by the combined effects of muscle disuse and systemic effects leading to myopathy.

• Quadriceps endurance and muscle bioenergetics were consistently abnormal in COPD patients. This is because muscle endurance is explained by both oxygen transport and muscle oxidative capacity.

• This study stresses the relevance of muscle endurance impairment in COPD patients and reinforces the for a separate assessment of muscle strength and muscle endurance.

Assessment of muscle strength vs muscle mass

• Isometric strength is the most sensible method to detect differences among subsets of subjects.

• Repetition maximum and handgrip strength can be considered for routine clinical use.

• Assessment of muscle mass is a good substitute for muscle strength in the clinical setting. Standardized measurements of bioelectrical impedance is suggested as an appropriate method for extensive noninvasive clinical use.

Clinical impact• Assessment of exercise tolerance provides an

integrative evaluation of pulmonary and peripheral factors determining aerobic capacity.

• This study shows high colinearity between muscle endurance , muscle strength and muscle mass as covariates of exercise tolerance .

• 6MWD is most suitable test for extensive clinical application.

• Further scope for research – evaluate the potential of alternative tests to assess muscle endurance in the clinical area.