By Dr. Doreen Wiggins for Yoga Medicine®.
Currently, studies are being conducted looking at this exact question. Preliminary research has been supportive, and universities such as John Hopkins are supporting diaphragmatic breathing to help with recovery from Covid. 
This article will explore the ancient wisdom and practice of pranayama, the basic tenet of yoga, and may serve to explain our first line of defense for the prevention, and aid in recovery from SARS-CoV-2.
What have we learned about the SARS-CoV-2 virus? How could yoga breath work help?
Viruses use receptors located on the cell surface to enter the body. The SARS-CoV 2 has a spike glycoprotein that binds to cells through the ACE 2 receptor, thus mediating entry of the virus into the cell. ACE 2 is a significant component of the Renin Angiotensin-Aldosterone System (RAS). ACE 2 modulates a protein called angiotensin II, an informational substance, with widespread and diverse functions; neuroendocrine, immune, cardiovascular, gastrointestinal, basic energy, modulating all aspects of well-being including our emotions. The ACE 2 receptor is also related to the emotion of anxiety.
This is why Covid 19 does not just cause a primary viral pneumonia.
Covid 19 utilizes the ACE 2 receptors to enter the cell and has direct effects within multiple organs through the Renin Angiotensin-Aldosterone System (RAS). There are two pathways of activation within the RAS with opposite bodily responses: related to cardiovascular, respiratory, renal, neurologic, immune, cytokine, and endothelial function.
Covid 19 virus typically enters the classical pathway with adverse systemic effects: cardiovascular challenges, increased sympathetic nervous system tension, respiratory, hypercoagulation, inflammatory, endothelial malfunction, and insulin resistance.  Which is also potentially heightened by states of anxiety and stress related to the emotional function of the ACE 2 receptor. Individuals living with a more active classical pathway before the virus, those with obesity, hypertension, sympathetic engagement, anxiety, and diabetes may have more receptors available to the virus to propagate a more intense reaction, and infection to Covid 19.
There is another pathway associated with the ACE 2 receptors, a pathway that can lead to better health outcomes, the “Counter-Regulatory RAS Axis” triggering: vasodilation, anti-inflammatory, anti-fibrotic and physiologic beneficial effects for the body. Lifestyle measures: nutrition, stress management, sleep, exercise (daily movement, moderate exercise not over- exercising), nasal breathing may help prevent infection or lead to improved outcome based on the manipulation of the RAS pathway.  Many of these lifestyle measures also can help strengthen the vagus nerve.
Why are the elderly more at risk with Covid 19, how is the RAS involved?
The RAS effects all cells associated with aging, through the classic pathway, leading to atherosclerotic process (fibrosis, vasoconstriction), and cellular dysfunction promoting age related diseases and decline. It has been demonstrated that the RAS is involved the the pathophysiological processes of other aging-related disorders, such as diabetes, chronic kidney disease, dementia, osteoporosis, and cancer. 4 The ACE 2 pathway in our elders is primed for the virus to enter, they have a unique vulnerability. (Tipping the RAS natural aging process towards the the Counter Regulatory Axis (Ang-(1-7) if engaging in health lifestyle practices may delay significant aging-related disorders.)
How does nasal breathing, pranayama help to prevent Covid and help with recovery?
Enhancing the Counter Regulatory RAS pathway, Ang-(1-7), a potential target to improve outcome, and conceptually decrease Covid 19 susceptibility is where pranayama, bee humming breath, and yoga come in.. with provocative molecular, peptide, and physiologic data.
Nitric Oxide produced by nasal breathing has inhibitory effects on Covid 19, and can potentially lessen viral load, and body response if infected.
The nasal cavity and turbinates play important physiological functions by filtering, warming and humidifying inhaled air. Paranasal sinuses continually produce nitric oxide (NO), a reactive oxygen species that diffuses to the bronchi and lungs to produce bronchodilators and vasodilatory effects. Studies indicate that NO may also help to reduce respiratory tract infection by inactivating viruses and inhibiting their replication in epithelial cells. 5 NO has been shown to be a powerful vasodilator, produced by blood vessel endothelial cells, that relaxes the smooth muscle fibers of the vascular wall. In fact, its physiological role extends to many other cell and tissue functions, notably in the respiratory, nervous and immune systems. 
Humming is 5 times more potent than nasal breathing with regards to Nitric Oxide production.
Harnessing NO through pranayama, bee humming breath, and yoga may serve as a potential tool to reduce viral extent of disease, improve immune response, and vasodilatation. 
Here are a few pranayama practices that can be helpful!
- Nasal breathing with prolonged expiration
- Bee Humming Breath: index fingers in the ears, mouth closed, and hum
- Anuloma Viloma Breath
- Wiese OJ, Allwood BW, Zemlin AE. COVID-19 and the renin-angiotensin system (RAS): A spark that sets the forest alight?. Med Hypotheses. 2020;144:110231. doi:10.1016/j.mehy.2020.110231
- Méry G, Epaulard O, Borel AL, Toussaint B, Le Gouellec A. COVID-19: Underlying Adipokine Storm and Angiotensin 1-7 Umbrella. Front Immunol. 2020 Jul 21;11:1714. doi:10.3389/fimmu.2020.01714. PMID: 32793244; PMCID: PMC7385229.
- Kamo T, Akazawa H, Komuro I. Pleiotropic Effects of Angiotensin II Receptor Signaling in Cardiovascular Homeostasis and Aging. Int Heart J. 2015 May 13;56(3):249-54. doi:10.1536/ihj.14-429. Epub 2015 Apr 27. PMID: 25912907.
- Martel J, Ko YF, Young JD, Ojcius DM. Could nasal nitric oxide help to mitigate the severity of COVID-19?. Microbes Infect. 2020;22(4-5):168-171. doi:10.1016/j.micinf.2020.05.002
- Jankowski R, Nguyen DT, Poussel M, Chenuel B, Gallet P, Rumeau C. Sinusology. Eur Ann Otorhinolaryngol Head Neck Dis. 2016 Sep;133(4):263-8. doi: 10.1016/j.anorl.2016.05.011. Epub 2016 Jul 1. PMID: 27378676
- Adusumilli NC, Zhang D, Friedman JM, Friedman AJ. Harnessing nitric oxide for preventing, limiting and treating the severe pulmonary consequences of COVID-19. Nitric Oxide. 2020;103:4-8. doi:10.1016/j.niox.2020.07.003
Important Health Advisory
The information within this article is not meant to replace medical care or preventative measures. You should consult an appropriate healthcare professional to determine if the exercise and information in this article are appropriate for your physical, medical, and psychological conditions.
If you are a yoga teacher, you should convey this message to your clients.