Exhaled nitric oxide at rest and exercise in water at varying temperatures

Lung exhaled nitric oxide {VNo=exhaled NO concentration ([NO]) x ventilation ( Vt)} increases linearly with VE and Oi consumption (Voz) during graded exercise but not during voluntary hypervenSlation. Increased VNo in exercise may be due to increased pulmonary flow (Q) and endothelial shear stress. Exhaled N 0 was measured by chemiluminescencein 10 males during incremental exercise bod in air and in thermoneutal head-outwater immersion (TNWI, 35° C) where Q is elevated at rest and mild exercise compared to air. VNO was unchanged at rest in Wl while it increased similarly with VE and V02 in both air and TNWI. A second groupof 10 males underwent incremental exercise in TNWI and also during Wl at 30°Candat20°C. At rest, VNO was similar at each temperature however [NO] was lower and VE higher at 20 °. Compared to TNWI, VNO was depressed signficanUyateach work toad at 30 °C with further significant decreases at each work load during 20 C. Exercise VE and Vo2 responses were similar at each temperature. We conclude ttat elevated Q in TNWI at rest and mild exercise is not associated with augmented VNO and that VNO is reduced dramatically as a function of temperaturein cod Wl where Q and shear stress are of similar to or greaterthan values observed in TNWI. These results suggest that King VNO is not dependent on pulmonary endotheüalshear stress within this range of Q alterations. The mechanisms resnonsible for the decline in Vun with coolino are unclear.