Biomaterial Database

Lower exhaled nitric oxide in hypobaric than in normobaric acute hypoxia. 2009

Tryggve Hemmingsson, and Dag Linnarsson

Section of Environmental Physiology, Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden. tryggve.hemmingsson@ki.se

Analysis of exhaled nitric oxide (NO) has become an accepted complementary tool in the management of inflammatory airway diseases. Previous studies have demonstrated reduced exhaled NO at altitude and ascribed their findings to hypoxia. We studied exhaled NO partial pressures (Pe(NO)) in eight healthy subjects at reduced ambient pressure down to 540 hPa (equivalent to 5000 m altitude) and at sea level, with equivalently hypoxic breathing gases (down to 11.3% O2 in N2). Pe(NO) readings were corrected for gas density effects on the instrument performance. Sea level control values for Pe(NO) at an exhaled flow of 50 mls(-1) averaged 2.4 mPa and were virtually unchanged with normobaric hypoxia down to an inspired P(O)(2) of 10.7 kPa. With the same degree of hypoxia, hypobaric Pe(NO) was 1.4 mPa. The reduction in hypobaric Pe(NO) of up to 33+/-16% (mean+/-SD) in comparison to normobaric Pe(NO), is likely to have been caused by enhanced axial back diffusion of NO because of the reduced gas density and an associated increased alveolar NO uptake to the blood.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D009569	Nitric Oxide	A free radical gas produced endogenously by a variety of mammalian cells, synthesized from ARGININE by NITRIC OXIDE SYNTHASE. Nitric oxide is one of the ENDOTHELIUM-DEPENDENT RELAXING FACTORS released by the vascular endothelium and mediates VASODILATION. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic GUANYLATE CYCLASE and thus elevates intracellular levels of CYCLIC GMP.	Endogenous Nitrate Vasodilator,Mononitrogen Monoxide,Nitric Oxide, Endothelium-Derived,Nitrogen Monoxide,Endothelium-Derived Nitric Oxide,Monoxide, Mononitrogen,Monoxide, Nitrogen,Nitrate Vasodilator, Endogenous,Nitric Oxide, Endothelium Derived,Oxide, Nitric,Vasodilator, Endogenous Nitrate
D010100	Oxygen	An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.	Dioxygen,Oxygen-16,Oxygen 16
D010313	Partial Pressure	The pressure that would be exerted by one component of a mixture of gases if it were present alone in a container. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Partial Pressures,Pressure, Partial,Pressures, Partial
D005260	Female		Females
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000531	Altitude	A vertical distance measured from a known level on the surface of a planet or other celestial body.	Altitudes
D000860	Hypoxia	Sub-optimal OXYGEN levels in the ambient air of living organisms.	Anoxia,Oxygen Deficiency,Anoxemia,Deficiency, Oxygen,Hypoxemia,Deficiencies, Oxygen,Oxygen Deficiencies
D015656	Respiratory Mechanics	The physical or mechanical action of the LUNGS; DIAPHRAGM; RIBS; and CHEST WALL during respiration. It includes airflow, lung volume, neural and reflex controls, mechanoreceptors, breathing patterns, etc.	Breathing Mechanics,Breathing Mechanic,Mechanic, Breathing,Mechanic, Respiratory,Mechanics, Breathing,Mechanics, Respiratory,Respiratory Mechanic