Transient fertilization of a post-Sturtian Snowball ocean margin with dissolved phosphate by clay minerals.

Marine sedimentary rocks deposited across the Neoproterozoic Cryogenian Snowball interval, ~720-635 million years ago, suggest that post-Snowball fertilization of shallow continental margin seawater with phosphorus accelerated marine primary productivity, ocean-atmosphere oxygenation, and ultimately the rise of animals. However, the mechanisms that sourced and delivered bioavailable phosphate from land to the ocean are not fully understood. Here we demonstrate a causal relationship between clay mineral production by the melting Sturtian Snowball ice sheets and a short-lived increase in seawater phosphate bioavailability by at least 20-fold and oxygenation of an immediate post-Sturtian Snowball ocean margin. Bulk primary sediment inputs and inferred dissolved seawater phosphate dynamics point to a relatively low marine phosphate inventory that limited marine primary productivity and seawater oxygenation before the Sturtian glaciation, and again in the later stages of the succeeding interglacial greenhouse interval.

Minimal clinically important difference of 3-minute chair rise test and the DIRECT questionnaire after pulmonary rehabilitation in COPD patients.

BACKGROUND: The 3-minute chair rise test (3-minute CRT) and the Disability Related to COPD Tool (DIRECT) are two reproducible and valid short tests that can assess the benefit of pulmonary rehabilitation (PR) in terms of functional capacity and dyspnea in everyday activities. METHODS: We determined the minimal clinically important difference (MCID) of the DIRECT questionnaire and 3-minute CRT using distribution methods and anchor encroaches with a panel of eight standard tests in a cohort of 116 COPD patients who completed a PR program in real-life settings. RESULTS: The estimated MCID for the 3-minute CRT and DIRECT scores was five repetitions and two units, respectively, using separate and combined independent anchors. The all-patient (body mass index-obstruction-dyspnea-exercise [BODE] scores 0-7), BODE 0-2 (n=42), and BODE 3-4 (n=50) groups showed improvements greater than the MCID in most tests and questionnaires used. In contrast, the BODE 5-7 group (n=24) showed improvements greater than MCID in only the 3-minute CRT, 6-minute walk test, endurance exercise test, and DIRECT questionnaire. DISCUSSION AND CONCLUSION: This study demonstrates that the short and simple DIRECT questionnaire and 3-minute CRT are responsive to capture the beneficial effects of a PR program in COPD patients, including those with severe disease. TRIAL REGISTRATION NUMBER: NCT03286660.

[Dyspnea and handicap in chronic obstructive pulmonary disease: interaction of their mechanisms]. / Mécanismes intégrés de la dyspnée et du handicap au cours de la bronchopneumopathie chronique obstructive.

Today, dyspnea in chronic obstructive pulmonary disease (COPD) is attributed to thoracic distention secondary to bronchial obstruction and hyperventilation. It inevitably occurs during exercise, even in patients with little obstruction, when they are capable of the elevated and prolonged power output that necessitates substantial hyperventilation. Exercise intolerance is due mainly to dyspnea, but muscle fatigue is also involved, especially in COPD patients who are malnourished. Deterioration of muscle function follows a substantial reduction in daily physical activity. In malnourished and hypoxemic subjects, however, responsibility for this is attributed to diverse aggravating biological processes related to chronic low-grade inflammation and to accentuated oxidative stress. The drastic diminution of physical activity results from ventilatory and muscle impairment and from symptoms that make movement painful. Improvement of ventilatory and muscle function, however, does not lead to recovery that allows sufficient physical activity. The spiral of disengagement, a morbid, psychodynamic process, accompanies chronic diseases and has the strongest effect in patients who were not highly physically active before becoming ill. Improvement of this handicap therefore requires a comprehensive management of patients, not confined to the prescription of physical activity under medical supervision. The aim is to offer diverse treatment propositions that can produce sustainable behavioral change.