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2021 Feb 1
Department of Biomedical Sciences, University of Sassari, Sassari, Italy
Energy expenditure and oxygen consumption during activities of daily living in people with multiple sclerosis and healthy subjects: an ecological approach to estimate real-life fatigue and fatigability
https://pubmed.ncbi.nlm.nih.gov/33539804/

Abstract

Objective: To compare oxygen consumption and energy expenditure (EE) of the activities of daily living (ADL) in people with multiple sclerosis (PwMS) and healthy subjects.

Design: Cross-sectional observational study SETTING: Outpatient care facilities PARTICIPANTS: Twenty-four moderately impaired PwMS and twenty-one healthy controls.

Intervention: Not applicable.

Outcome measures: Oxygen consumption, EE rate and total EE assessed by portable open-circuit spirometry during the accomplishment of a comprehensive set of 14 ADL. Body composition was also assessed with bioelectrical impedance analysis. Body cell mass was used to normalize metabolic rates between groups.

Results: PwMS exhibited significantly higher oxygen consumption than controls in transfer and mobility tasks (walking with stairs: +10.4%, p=0.04; without stairs: +15.2%, p=0.002; driving: +10.4%, p=0.04), and higher EE rate for walking (+13.6%, p=0.01). ADL completion took significantly longer in PwMS. Consequently, when total EE to complete each ADL was considered, PwMS used significantly more energy in 10 of the 14 ADL. Of these, 'climb stairs' and walking with or without stairs showed the largest differences (+100%, +99.5%, +79.3%, respectively; all p-values<0.0005), followed by 'dressing' (+48.8%; p=0.002), 'laundry' (+41.7%; p=0.007), and 'shopping' (+40.1%; p=0.003).

Conclusions: Moderately disabled PwMS display oxygen consumption and EE rates during ADL that are comparable to those of matched healthy subjects, except for the activities that involve walking. While metabolic rates were not different for the majority of ADL, PwMS showed higher total EE to complete the same activities at a comparable work intensity, which may contribute to the burden of 'real-life' tiredness and fatigue typically described in this population. Importantly, the subjective MFIS score significantly correlated to EE and VO2 of selected ADL, such as 'make a bed', 'driving', 'clean surfaces' and 'climb-stairs'. The joint employment of open-circuit spirometry during ADL and body composition analysis allows an accurate metabolic characterization of PwMS, who frequently complain of fatigue.

2021 Feb 5
McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
Resting cerebral oxygen metabolism exhibits archetypal network features
https://pubmed.ncbi.nlm.nih.gov/33544446/

Abstract

Standard magnetic resonance imaging approaches offer high-resolution but indirect measures of neural activity, limiting understanding of the physiological processes associated with imaging findings. Here, we used calibrated functional magnetic resonance imaging during the resting state to recover low-frequency fluctuations of the cerebral metabolic rate of oxygen (CMRO2 ). We tested whether functional connections derived from these fluctuations exhibited organization properties similar to those established by previous standard functional and anatomical connectivity studies. Seventeen participants underwent 20 min of resting imaging during dual-echo, pseudocontinuous arterial spin labeling, and blood-oxygen-level dependent (BOLD) signal acquisition. Participants also underwent a 10 min normocapnic and hypercapnic procedure. Brain-wide, CMRO2 low-frequency fluctuations were subjected to graph-based and voxel-wise functional connectivity analyses. Results demonstrated that connections derived from resting CMRO2 fluctuations exhibited complex, small-world topological properties (i.e., high integration and segregation, cost efficiency) consistent with those observed in previous studies using functional and anatomical connectivity approaches. Voxel-wise CMRO2 connectivity also exhibited spatial patterns consistent with four targeted resting-state subnetworks: two association (i.e., frontoparietal and default mode) and two perceptual (i.e., auditory and occipital-visual). These are the first findings to support the use of calibration-derived CMRO2 low-frequency fluctuations for detecting brain-wide organizational properties typical of healthy participants. We discuss interpretations, advantages, and challenges in using calibration-derived oxygen metabolism signals for examining the intrinsic organization of the human brain.