Inhaled nasopharyngeal nitric oxide concentrations during unilateral nostril breathing – A pilot study
Graphical abstract
Introduction
The yogic pranayama technique of unilateral nostril breathing (UNB) has been shown to provide multiple benefits including improvement in language and anxiety in stroke sufferers (Marshall et al., 2014), as well as reduced blood pressure and increased heart rate in normal healthy adults (Ertuğrul Öztürk, 2012).
The nasal airways, particularly the paranasal sinuses, are a rich source of inhaled nitric oxide (NO) (Lundberg et al., 1995), a vasodilator and neurotransmitter gas produced by NO synthase from arginine and oxygen (Young, 2002) that has antibacterial and antiviral actions (Lundberg, 2008), and also plays an important role in modulating epithelial function including ciliary beat frequency (Lundberg, 2008; Qian et al., 2001; Ren et al., 2019). Previous research has shown that nasal NO concentrations are nasal airflow dependent (Chatkin et al., 1999; Qian et al., 2001). The increased inhaled NO concentration in the congested side of the nose associated with the nasal cycle, is thought related to reduced airflow (Qian et al., 2001). Although NO concentrations on each side of the nose might change with patency status, the NO concentrations delivered to the lower airways remain relatively stable, and reduce with increasing age, poor diet and inactivity (Torregrossa et al., 2011)
During unobstructed bilateral nostril breathing (BNB), the nasal cycle describes periodic changes in nasal airway geometry which results in a greater tidal nasal air-flow volume passing through one side of the nose: the patent airway, while a lesser volume passes through the other side: the congested airway (Eccles, 2000; Hanif et al., 2000). While the purpose(s) of the nasal cycle continues to be debated and discussed (Pendolino et al., 2018), it is well known that the nose has an important role in maintaining airway health by entrapping inhaled pathogens, allergens and pollutants, as well as heating and humidifying inhaled air (Elad et al., 2008). One important purpose of the nasal cycle is thought to enable the upper airway to accommodate the contrasting roles of air conditioning and the removal of entrapped contaminants through fluctuation in airflow partitioning between each airway (White et al., 2015).
Previous research has investigated nasal NO concentrations in a non-ventilated nose (Chatkin et al., 1999), as well as nasal NO concentrations associated with the nasal cycle (Qian et al., 2001). These studies found nasal NO concentration is nasal airflow dependent, and pharyngeal NO concentrations were correlated negatively to nasal volume.
Our investigation sought to identify the influence UNB has on mean inhaled nasopharyngeal NO concentrations compared to unobstructed BNB, and if this was the case, identify the nasal cycle phase associated with any increase in inhaled nasal NO concentration.
Section snippets
Methods
We conducted a clinical study at the Auckland University of Technology BioDesign Lab between April and July 2019. All research procedures were approved by the Auckland University of Technology Ethics Committee (AUTEC approval 17/135) and conducted in accordance with the Helsinki Declaration. All volunteers underwent a nasal endoscopic examination by an otolaryngologist. Volunteers with a significant septal deviation, turbinate abnormalities or inflammation were excluded, along with those with a
Results
All the breathing condition gas concentration means were found to be normally distributed.
Discussion
Mean inhaled ambient NO concentrations at the nasal vestibule (Table 1) were low for all participants, and typical of that found indoors (Jarvis et al., 2010). Exhaled nasal NO concentrations, which are normally used to diagnose airway inflammation (Maniscalco et al., 2007), (Table 1, Table 2), were in the healthy range (Hogman et al., 2000), indicating none of the participants had underlying airway inflammatory issues. For each participant in the current study, minor variation in mean ambient
Conclusions
Inhaled nasopharyngeal NO concentrations appear to change with the nasal patency status associated with the nasal cycle. For a nose exhibiting a nasal cycle, inhaled nasopharyngeal NO concentrations are consistently higher during congested-side UNB compared to both patent-side UNB or BNB. The findings of this pilot study suggest that for maximum inhaled NO, UNB should commence on the congested side of the nose.
Author contributions
DEW and JB designed the study, JB undertook all nasal examinations, THAS undertook data collection, THAS, JB and DEW were involved with manuscript preparation. All authors have read and approved the final manuscript.
Declaration of Competing Interest
DEW and JB are listed inventors of a lateralised nasal breathing device.
THAS has no competing financial interests.
Acknowledgements
The authors would like to thank all participants from this study, and Dr Robin Hankin of the School of Computing and Mathematical Sciences, Auckland University of Technology, for providing statistical advice and analysis.
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