August Krogh's theory of muscle microvascular control and oxygen delivery: a paradigm shift based on new data

Abstract

He is a fellow of the Danish Royal Academy of Sciences and Letters. They share interests in microcirculatory function, oxygen and substrate transport and cellular energetics, especially in muscle at rest and during exercise and also within the brain in health and disease.

SARS CoV‐2 related microvascular damage and symptoms during and after COVID‐19: Consequences of capillary transit‐time changes, tissue hypoxia and inflammation

“…Therefore, blood's uptake of oxygen in the lungs, and the uptake of oxygen by tissue, not only depend on blood flow , but also on bloods microscopic distribution across the capillary bed (Angleys & Østergaard, 2020; Hsia et al, 1999; Jespersen & Østergaard, 2012; Østergaard, 2020). Biophysically, the redistribution of blood among open capillaries can account for the puzzling increase in oxygen PS observed as blood flow increases through most organs, without the need to invoke classical “capillary recruitment” (the active opening of previously closed capillaries), which has now been ruled out in most organs (Østergaard, 2020; Poole et al, 2020). This review focuses on the effects of break ‐ downs in the factors that ensure the crucial, parallel increase in PS and blood flow, after biophysical models have predicted that capillary occlusions and severe capillary flow disturbances can limit tissue oxygenation to the same extent as symptomatic reductions in blood flow (ischemia) in brain, heart, and kidneys (Østergaard et al, 2013, 2014, 2015).…”

Spatial matching of microvascular oxygen delivery to demand in skeletal muscle: Has the missing link been found?

“…By contrast to dated models, compelling evidence now supports that blood flow is controlled at the arteriolar level and the majority of capillaries support red blood cells (RBCs) and plasma flux at rest (Poole et al . 2020). Thus, during exercise, capillaries increase by elevating RBC velocity and flux (perfusive O 2 conductance) and haematocrit (diffusive O 2 conductance) in contrast to de novo recruitment per se .…”

August Krogh: physiology genius and compassionate humanitarian

“…The featured paper (Poole et al . 2020) presents Krogh's three 1919 Journal of Physiology muscle microcirculation and oxygen transport papers that won him the Nobel. In Poole et al .…”

“…In Poole et al . (2020) Julius Comroe's insightful retrospectroscopic approach (Comroe, 1978) is adopted to help illuminate and contextualize Krogh's (and his wife, Marie's) discoveries and bring them into contemporary perspective. To focus the reader's attention to the scientific progression of our understanding of capillary function, other details of Krogh's life, his unique challenges and many other achievements were omitted from Poole et al .…”

“…To focus the reader's attention to the scientific progression of our understanding of capillary function, other details of Krogh's life, his unique challenges and many other achievements were omitted from Poole et al . (2020). For the interested reader pertinent vignettes are presented below revealing a fascinating backdrop to this outstanding humanitarian and one of the most influential physiologists to this day.…”