Non Invasive Evaluation of Muscle Hypoxia in COPD Patient (EVANIMUS)
Non Invasive Evaluation of Muscle Hypoxia in COPD Patient (EVANIMUS)
Peripheral muscle oxidative function is altered in COPD(chronic obstrutive pulmonary disease)
 patients. Multiple factors could contribute to this dysfunction including chronic hypoxia and
 deconditioning (sedentarity).

 The evaluation of mitochondrial function is based on invasive method (muscle biopsy and in
 vitro respirometry) or magnetic resonance spectroscopy limited to small muscle groups.
 Recently, a non invasive method has been described using Near InfraRed Spectroscopy (NIRS).
 During arterial occlusion, muscle deoxygenation is only dependent of local oxygen
 consumption. The time constant recovery (k) of the deoxygenation during repeated ischemia
 periods has been shown to be correlated to measurements of maximal mitochondrial capacity.

 k is lower in COPD patients compared to smokers without bronchial obstruction. However, the
 influence of arterial hypoxia has never been studied precisely, no more than the confounding
 effect of deconditioning on k.

 So , the aim is to compare k in COPD patients with chronic hypoxemia (treated with long term
 oxygenotherapy, LTOT+ group) and patients without hypoxia, matched for their physical
 activity (LTOT- group).

 The hypothe is that k will be lower in LTOT+ group compared to LTOT- group and that short
 term O2 supplementation will improve it, which would suggest a muscle hypoxia. By contrast,
 O2 should not influence k in LOT- group, in whom it is mainly determined by muscle
 conditioning.
Investigator will compare mVO2 time constant in 2 groups of COPD (chronic obstrutive
 pulmonary disease) patients matched for age, sex, physical activity (estimated by GPAQ
 questionnaire (Global Physical Activity Questionnaire)), one with chronic hypoxemia (LTOT+
 group) and one without blood gas abnormalities (LTOT- group)..

 Inclusion visit It will allow to calculate physical activity in Mets.min/week, from the GPAQ
 questionnaire. The patient will also be accustomed to the repeated arterial occlusion
 procedure. A pneumatic cuff will be wrapped around the thigh and will be progressively
 inflated to a suprasystolic value (rapid air inflation system Hokanson), from 160 mmHg up to
 tolerated maximal pressure (max 220 mmHg).

 Experimental visit

 -  Muscle biopsy. A biopsy of the vastus lateralis will be performed while breathing
 ambient air. After disinfection and anesthesia of skin and subcutaneous tissue, an
 automatic biopsy gun (Monopty Bard 14G) will be introduced in the muscle and a 20 mg
 biopsy will be withdrawn. The maximal mitochondrial O2 consumption and mitochondrial
 affinity for O2 will be immediately measured with high resolution respirometry
 (Oroboros, 10 mg tissue). A 10 mg fragment will be stored in liquid nitrogen for mRNA
 analysis of hypoxia driven genes (Hypoxia-inducible Factor 1, Vascular Endothelial
 Growth Factor, Carbonic Anhydrase 9, Heme Oxygenase 1).

 -  mVO2 time constant measurement (k, min-1) in ambient air. A NIRS probe (Oxymon III) will
 be placed on the thigh (contralateral to the muscle biopsy) and secured with an elastic
 wrap. The NIRS signal will be displayed continuously and recorded on a software
 (Oxysoft) The inflation cuff will be placed upstream the NIRS probe. After 5 to 10
 isometric contractions of the quadriceps, the cuff will be rapidly inflated (maximal
 tolerated pressure determined during the inclusion visit) and deflated according to a
 predetermined protocol: 5 s /5 s 5 times, followed by 7 s /7 s 5 times and then 10 s/10
 s 10 times. The deoxygenation kinetics (% deoxygenation/min) will be calculated for
 every occlusion and these deoxygenation indices will be expressed over time in order to
 calculate the time constant of the exponential relationship (k, min-1). This sequence
 will be repeated twice and the k values will be averaged.

 -  mVO2 time constant measurement with O2. Oxygen therapy will be given to the patient for
 1 hour before repeating the k determination as described above. Oxygen flow will be set
 to the habitual flow rate in the LTOT+ group, and an arbitrary 3 L/min flow rate in the
 LTOT- group.
Inclusion Criteria:

 -  COPD diagnostic

 -  Both sex

 -  18 <Age <80 years old

 -  LTOT- group : PaO2 ≥ 65 mmHg and SaO2≥ 92%

 -  LTOT+ group: long term oxygenotherapy prescribed for more than 3 months, with daily
 use between 12 and 15 hours.

 Patients in both groups will be matched for age (± 5 years), sex and physical activity
 estimated by GPAQ questionnaire (± 15% Mets.min/week).

 Exclusion Criteria:

 -  Recent cardiorespiratory exacerbation (<6 weeks).

 -  Pulmonary rehabilitation program during the last 2 months

 -  Continuous LTOT (24 hours) or deambulation O2 therapy alone

 -  Anticoagulant drugs

 -  Hematocrit outside the normal range (35-50%)