Nasal or oral breathing impact on vascular endothelium - an ultrasound approach

Introduction: Obstructive Sleep Apnea-Hypopnea Syndrome (OSAH) is characterised by a reduction in nasal breathing in favour of oral breathing and obstruction of the upper airway by the lingual muscles. Epithelial production of Nitric Oxide (NO) by inducible Oxide Nitric Synthase in the paranasal sinuses plays an important role in protecting the lung from bacterial growth and increases lung perfusion. Nitric Oxide has a major vasodilatory effect (Lundberg et al. 2008 and Sanchez Crespo et al. 2010) and is absorbed during nasal breathing, emptying paranasal sinuses through a Venturi effect. The aim of the study is to compare the effect of oral and nasal breathing on the vasodilation of the brachial artery. This effect will be measured by ultrasound using the Flow Mediated Dilation method (Corretti et al. 2002). Material and Method: Fourty-five healthy male with a mean age of 21.3 ± 2.3 years volunteered after informed consent. Vascular health was monitored by the Ankle Brachial Index test, with no cardiac pathology and no sleep disorders. Each subject was well hydrated, not under the influence of alcohol or drugs, non-smoker and had not consumed dark chocolate. The participants underwent two different protocols (nasal or oral breathing) in random order. Each protocol was separated by a 10 min soft walking period and a 30 min. rest to eliminate the effects of the previous protocol. Ultrasound analysis of brachial artery dilation (protocol of Corretti et al. 2002) was performed. Results: Nasal breathing (in comparison with control oral breathing) induces significant mean dilation of 5.93% of the brachial artery (p< 0,0001). This dilation would hypothetically be due to endogenous accumulation of NO from the paranasal sinuses. Discussion and Conclusion: Nasal breathing induces a dilating response in the peripheral arterial system. In the context of OSAH, therapeutic management in favour of nasal breathing should be proposed and promoted at the expense of oral breathing. The biological cycle of production, circulation and absorption of endogenous NO in the paranasal sinuses could have a place in the treatment of hypertension in patients with OSAH (Hajian et al. 2016, Ichinose et al., 2004, Bloch et al., 2007).