Blood shifts between body compartments during submaximal exercise with induced expiratory flow limitation in healthy humans

External expiratory flow limitation (EFLe) can be applied in healthy subjects to mimic the effects of chronic obstructive pulmonary disease during exercise. At maximal exercise intensity, EFLe leads to exercise intolerance owing to respiratory pump dysfunction limiting venous return. We quantified blood shifts between body compartments to determine whether such effects can be observed during submaximal exercise, when the load on the respiratory system is milder. Ten healthy men (25.2±3.2 years of age, 177.3±5.4cm in height and weighing 67.4±5.8kg) exercised at 100W (∼40% of maximal oxygen uptake) while breathing spontaneously (CTRL) or with EFLe. We measured respiratory dynamics with optoelectronic plethysmography, oesophageal (Pes) and gastric (Pga) pressures with balloon catheters, and blood shifting between body compartments with double body plethysmography. During exercise, EFLe resulted in the following changes: (i) greater intrabreath blood shifts between the trunk and the extremities [518±221 (EFLe) vs. 224±60ml (CTRL); P<0.001] associated with lower Pes during inspiration (r=0.53, P<0.001) and higher Pga during expiration (r=0.29, P<0.024); and (ii) a progressive pooling of blood in the trunk over time (∼700ml after 3min of exercise; P<0.05), explained by a predominant effect of lower inspiratory Pes (r=0.54, P<0.001) over that of increased Pga. It follows that during submaximal exercise, EFLe amplifies the respiratory pump mechanism, with a prevailing contribution from lower inspiratory Pes over increased expiratory Pga, drawing blood into the trunk. Whether these results can be replicated in chronic obstructive pulmonary disease patients remains to be determined. (Figure presented.). Key points: External expiratory flow limitation (EFLe) can be applied in healthy subjects to mimic the effects of chronic obstructive pulmonary disease and safely study the mechanisms of exercise intolerance associated with the disease. At maximal exercise intensity with EFLe, exercise intolerance ...