Organ perfusion during voluntary pulmonary hyperinflation; a magnetic resonance imaging study

Pulmonary hyperinflation is used by competitive breath-hold divers and is accomplished by glossopharyngeal insufflation (GPI) known to compress the heart and pulmonary vessels, increasing sympathetic activity and lowering cardiac output (CO) without known consequence for organ perfusion. Myocardial, pulmonary, skeletal muscle, kidney and liver perfusion were evaluated by magnetic resonance imaging in 10 elite breath-hold divers at rest and during moderate GPI. Cardiac chamber volumes, stroke volume (SV) and thus CO were determined from cardiac short-axis cine images. Organ volumes were assessed from gradient echo-sequences and organ perfusion was evaluated from first-pass images after gadolinium injection. During GPI, lung volume increased by 5.2±1.5 L (mean±SD; P<0.001), while spleen and liver volume decreased by 46±39 and 210±160 mL, respectively (P<0.05) and inferior caval vein diameter by 4±3 mm (P<0.05). Heart rate tended to increase (67±10 to 86±20 bpm; P=0.052) as right and left ventricular volumes were reduced (P<0.05). SV (107±21 to 53±15 mL) and CO (7.2±1.6 to 4.2±0.8 L min(-1)) decreased as assessed after 1 min of GPI (P<0.01). Left ventricular myocardial perfusion maximum up-slope and its perfusion index decreased by 1.52±0.15 s(-1) (P<0.001) and 0.02±0.01 (P<0.05), respectively, without transmural differences. Pulmonary tissue, spleen, kidney and pectoral-muscle perfusion also decreased (P<0.05) and yet liver perfusion was maintained. Thus, during pulmonary hyperinflation by GPI, CO and organ perfusion including the myocardium as well as perfusion of skeletal muscles are reduced and yet perfusion of the liver is maintained. Liver perfusion seems to be prioritized when cardiac output decreases during glossopharyngeal insufflation.