Airway hydration & health
The following peer-reviewed publications are a compendium of scientific literature related to the health and wellness implications of dry airways and the breathing of moist and salty air. Select a year below to learn more.
Relative humidity in droplet and airborne transmission of disease. J. Biol. Phys. 47, 1-29
Anže Božič, Matej Kandu.
This review discusses the physical principles that govern the fate of respiratory droplets and any viruses trapped inside them, with a focus on the role of relative humidity.
Hydrating the respiratory tract: An alternative explanation why masks lower severity of COVID-19. Biophysical Journal.
Courtney JM, Bax A.
This demonstrates that normal breathing results in an absorption-desorption cycle inside facemasks, in which supersaturated air is absorbed by the mask fibers during expiration, followed by evaporation during inspiration of dry environmental air.
Exhaled aerosol increases with COVID-19 infection, age, and obesity. PNAS
D.A. Edwards, D. Ausiello, J Salzman, T Devlin, R. Langer, B. Beddingfield, A.C. Dears, L.A. Doyle-Meyers, R.K. Redmann, S.Z. Killeen, N.J. Maness, C.J. Roy.
This studied respiratory droplet generation and exhalation in human and nonhuman primate subjects with and without COVID-19 infection to explore whether SARS-CoV-2 infection, and other changes in physiological state, translate into observable evolution of numbers and sizes of exhaled respiratory droplets in healthy and diseased subjects.
Rapid changes in mucociliary transport in the tracheal epithelium caused by unconditioned room air or nebulized hypertonic saline and mannitol are not determined by frequency of beating cilia. Intensive Care Medicine Experimental.
Kelly JS, Martinsen P, and Tatkov S.
This study determines the short-term effect of flowing room air and nebulized hypertonic saline and mannitol on mucociliary transport in the trachea.
Influence of water spraying on an oscillating channel. Journal of Fluids and Structures, Elsevier
A Bouvet, X Pelorson, A van Hirtum
Looks at the influence of homogeneous water spraying on an oscillating channel is investigated experimentally using several vocal folds replicas. Changes to glottal flow features are systematically quantified for a rigid replica with forced oscillation. Changes to auto-oscillation features are systematically quantified by analyzing the pressure measured upstream from deformable replicas
Relationship between biometeorological factors and the number of hospitalizations due to asthma. Sci Rep
A. Romaszko-Wojtowicz, I. Cymes, E Dragańska. et al.
An assessment of relations between the frequency of asthma exacerbation and environmental conditions was made according to the meteorological components, the biometeorological index UTCI (Universal Thermal Climate Index), as well as selected air quality parameters, including concentrations of PM10 and PM2.5.
Airway Hygiene in Children and Adults for Lowering Respiratory Droplet Exposure in Health and Learning Environments in Clean and Dirty Air. Molecular Frontiers Journal.
C.E. George, J. Salzman, L.R. Inbaraj, S. Chandrasingh, C. Klein, L. Morawska, D.A. Edwards.
Found in a human volunteer study involving that respiratory droplets — of the size and nature to potentially contain COVID-19, influenza, allergens and other contaminants — diminish in number on exhalation by up to 99% via the “airway hygiene” administration of a nasal saline rich in calcium. Exhaled particles were significantly higher and efficacy of airway hygiene greatest at the site (Bangalore India) with highest fine particle ambient air burden.
A new natural defense against airborne pathogens. QRB Discovery
D.A. Edwards, A. Hickey, R. Batycky, L. Griel, M. Lipp, W. Dehaan, R. Clarke, D. Hava, J. Perry, B. Laurenzi, A.K. Curran. 1, e5
This proposes the nasal administration of calcium-enriched physiological salts as a new hygienic intervention with possible therapeutic application as a response to the rapid and tenacious spread of COVID-19.
Nasal Calcium-Rich Salts for Cleaning Airborne Particles from the Airways of Essential Workers, Students, and a Family in Quarantine. Molecular Frontiers Journal
This study evaluated the intranasal delivery of calcium-enriched saline to suppress breath particles in practical settings reflecting essential worker hygiene, quarantine hygiene, and back-to-school hygiene.
Exhaled particles and small airways. Respir Res
B. Bake, P. Larsson, G. Ljungkvist, et al.
Analyzing the content of exhaled particles as generated by the airway reopening mechanism, offers an exciting noninvasive way to obtain samples of RTLF from small airways. Results from a few early and small clinical studies on COPD, asthma and BOS indicate associations with altered particle formation and particle composition.
Aqueous Microdroplets Containing Only Ketones or Aldehydes Undergo Dakin and Baeyer-Villiger Reactions. Chem. Sci.
Dan Gao, Feng Jin, Jae Kyoo Lee, Richard N. Zare.
It was found that increasing the content of water and decreasing the droplet size improve the product yield of the Dakin and BV reactions, supporting the contention that the amount of H2O2 generated in aqueous microdroplets could induce the two reactions and the reactions occur at or near the air–water interface of the microdroplet surface.
Low ambient humidity impairs barrier function and innate resistance against influenza infection. PNAS 116:10905–10
E. Kudo, E. Song, L.J. Yockey, T. Rakib, P.W. Wong, et al..
It was found that inhalation of dry air impairs mucociliary clearance, innate antiviral defense, and tissue repair. Moreover, disease exacerbated by low relative humidity was ameliorated in caspase-1/11–deficient Mx1 mice, independent of viral burden. Single-cell RNA sequencing revealed that induction of IFN-stimulated genes in response to viral infection was diminished in multiple cell types in the lung of mice housed in low humidity condition. These results indicate that exposure to dry air impairs host defense against influenza infection, reduces tissue repair, and inflicts caspase-dependent disease pathology.
Spontaneous Generation of Hydrogen Peroxide from Aqueous Microdroplets, Proc. Nat. Acad. Sci (US)
Jae. Kyoo Lee, et al.
This showed that H2O2 is spontaneously produced from pure water by atomizing bulk water into microdroplets (1 μm to 20 µm in diameter). Production of H2O2, as assayed by H2O2-sensitve fluorescence dye peroxyfluor-1, increased with decreasing microdroplet size.
Mechanistic insights into the effect of humidity on airborne influenza virus survival, transmission, and incidence. J. R. Soc. Interface
This re-evaluates studies of influenza virus survival in aerosols, transmission in animal models and influenza incidence to show that the combination of temperature and RH is equally valid as AH as a predictor. Collinearity was considered, as higher levels of AH are only possible at higher temperatures, where it is well established that virus decay is more rapid.
The effect of hydration on voice quality in adults: a systematic review, J Voice
This study is aimed to critically appraise scientific, peer-reviewed articles, published in the past 10 years on the effects of hydration on voice quality in adults.
The impact of cold on the respiratory tract and its consequences to respiratory health. Clin Transl Allergy
M. D’Amato, A. Molino, G. Calabrese, L. Cecchi, I. Annesi-Maesano, G. D’Amato.
There is a need to better define the consequences of repeated exposure to cold air and the mechanisms by which such exposure could modify airway function and affect the outcomes of patients with pre-existing airway disease. This could help to promote adequate policy and public health actions to face the incoming challenges.
The mystery of dry indoor air – An overview. Environment International, Volume 121, Part 2, Pages 1058-1065
Perceived dry air is among the most abundant complaints in office-like environments. Perceived dry air is elicited by low air humidity aggravating eyes, nose and airways. Perceived dry air may be exacerbated by proto-sensory irritation from air pollutants. Perceived dry air intercorrelated with low air humidity, eye and nose symptoms. Age, certain medication, and nasal diseases exacerbate the perception of dry air.
Indoor temperature and humidity in New York City apartments during winter, Science of The Total Environment
Ashlinn Quinn, Jeffrey Shaman
Wintertime air in New York City apartments is very dry. Levels of humidity seen here are consistent with increased influenza virus survival. Humidifier ownership was not associated with increased indoor humidity.
Efficiency of controlled halotherapy in rehabilitation of patients with occupational lung diseases. Med Tr Prom Ekol
Chervinskaya AV, Kotenko KV.
The study was aimed at features and efficiency of controlled halotherapy method in patients with occupational chronic obstructive lung disease (COLD). Considerable improvement was seen: for mild COLD-- in 40% of cases, for moderate COLD - in 30%, with general efficiency for these patients of 90 and 85% respectively. Analysis of the results obtained enables to evaluate controlled halotherapy as an effective method of rehabilitation and prevention in occupational COLD patients.
Airway hydration and COPD. Cell Mol Life Sci.
A. Ghosh, R.C. Boucher, R. Tarran
This review highlights the cellular components responsible for maintaining MCC and how this process is disrupted following tobacco exposure and with CB. Existing therapeutic strategies for the treatment of chronic bronchitis and how components of the MCC can be used as biomarkers for the evaluation of tobacco or tobacco-like-product exposure are also discussed.
Duration of action of hypertonic saline on mucociliary clearance in the normal lung. J Appl Physiol 118: 1483–1490
Bennett WD,Wu J, Fuller F, Balcazar JR, Zeman KL, Duckworth H, Donn KH, O’Riordan TG, Boucher RC and Donaldson SH.
Assesses the duration of pharmacodynamic effects of HS in healthy subjects by performing radiotracer clearance studies at baseline, 30-min post-HS administration, and 4-h post-HS administration.
On the role of environmental humidity on cortisol production by epidermal keratinocytes. Exp Dermatol, 23: 15-17
Guo Zhu, Zorica Janjetovic, Andrzej Slominsk.
... skin can act as an independent steroidogenic organ. The role of this regulated steroidogenic system in physiological or pathological outcomes requires further studies with focus on cutaneous homeostasis, formation of epidermal barrier, antimicrobial activity and display of immune (both pro- and anti-inflammatory) properties.
A review of halotherapy for chronic obstructive pulmonary disease. Int J Chron Obstruct Pulmon Dis.
Rashleigh R, Smith SM, Roberts NJ.
This review critically evaluates and summarizes the evidence for the use of halotherapy as a treatment for COPD.
How much water is lost during breathing? Pneumonol. Alergol. Pol. 80, 3: 339–342
J. Zieliński, J. Przybylski.
Using the Antoine equation and the ideal gas law, the volume of exhaled water was calculated. Air temperature, humidity and minute ventilation had been taken accounted for and during physical exercise the amount of exhaled H(2)O is linear, but not proportional to heart rate.
Why Do We have to Move Fluid to be Able to Breathe. Front Physiol. 3,146
M. Fronius, W.G. Clauss, M. Althaus.
The review highlights the importance of the alveolar fluid, its volume and its composition. Maintenance of the fluid volume and composition within certain limits is critical to facilitate gas exchange.We propose that the alveolar fluid is an essential element of the air-blood barrier
Hypertonic Saline in Treatment of Pulmonary Disease in Cystic Fibrosis. The Scientific World Journal. Volume 2012, Article ID 465230
Reeves ER, Molloy K et al and McElvaney
This review aims to discuss the described therapeutic benefits of hypertonic saline and specifically to identify novel models of hypertonic saline action independent of airway hydration.
Mechanisms and applications of hypertonic saline. J R Soc Med
Elkins MR, Bye PT.
Hypertonic saline is a strong sterile solution of salt water that can be inhaled as a nebulized medication for people with cystic fibrosis (CF). To examine how it should be applied clinically, the mechanisms by which it affects the disease process, and which signs, symptoms and other clinical outcomes it influences were considered. Finally, how the effect is influenced by the dose received, and whether this should influence how it is applied in clinical practice were also considered.
Saline nasal irrigation for acute upper respiratory tract infections.
Kassel JC, King D, Spurling GK.
Systematic review to evaluate the efficacy of saline nasal irrigation in treating the symptoms of acute URTIs.
The role of hydration in vocal fold physiology. Curr Opin Otolaryngol Head Neck Surg. 18(3): 171–175
M. Sivasankar and C. Leyden
Increased systemic and superficial vocal fold hydration as a component of vocal hygiene may improve overall health and efficiency of the vocal apparatus. However, continued exploration of biological mechanisms regulating vocal fold hydration is needed to optimize clinical hydration interventions.
Influence of gender and body composition on hydration and body water spaces. Clin. Nutr. 27, 740–746
P. Ritz, S. Vol, G. Berrut, I. Tack, M.J. Arnaud and J. Tichet, J.
This study provides reference values for body water spaces in healthy adults that are negatively correlated with BMI. Women and obese people display indicators of cellular dehydration, and are more at risk of dehydration.
Influenza virus transmission is dependent on relative humidity and temperature. PLoS Pathog 3(10): e151
Anice C Lowen , Samira Mubareka, John Steel, Peter Palese.
Using the guinea pig as a model host, we show that aerosol spread of influenza virus is dependent upon both ambient relative humidity and temperature. We provide direct, experimental evidence to support the role of weather conditions in the dynamics of influenza and thereby address a long-standing question fundamental to the understanding of influenza epidemiology and evolution.
Why inhaling salt water changes what we exhale. J Colloid Interface Sci 307(1), 71-78
W. Watanabe W.
We find that inhaling salt water diminishes subsequently exhaled biomaterial in man and animals due to reversible stabilization of the airway lining fluid (ALF)/air interface as a novel potential means for control of the spread of airborne infectious disease. The mechanism of this phenomenon relates to charge shielding of mucin or mucin-like macromolecules that consequently undergo gelation; this gelation alters the physical properties of the ALF surface and reduces its breakup.
Inhaling to mitigate exhaled bioaerosols. Proceedings of the National Academy of Sciences 101(50), 17383-17388
D. A. Edwards, et al.
We find that some normal human subjects expire many more bioaerosol particles than other individuals during quiet breathing and therefore bear the burden of production of exhaled bioaerosols. Administering nebulized isotonic saline to these “high-producer” individuals diminishes the number of exhaled bioaerosol particles expired by 72.10 ± 8.19% for up to 6 h. In vitro and in vivo experiments with saline and surfactants suggest that the mechanism of action of the nebulized saline relates to modification of the physical properties of the airway-lining fluid, notably surface tension.
Total body water data for white adults 18 to 64 years of age: the Fels Longitudinal Study. Kidney Int. 56, 244–252
W.C. Chumlea, S.S. Guo, C.M.. Zeller, N.V. Reo, N. V., and R.M. Siervogel
Total body water (TBW) volume is reported to decrease with age, but much of the published data are 20 to almost 50 years old and are cross-sectional. The findings from these mixed longitudinal data indicate that TBW volume, on average, maintains a reasonable degree of stability in men and women through a large portion of adulthood.
Fluid Dynamics of the Human Larynx and Upper Tracheobronchial Airways. Aerosol Science and Technology. 19:2, 133-156
Martonen TB, Zhang Z & Lessmann RC.
An original theory is presented for the simulation of laryngeal and tracheobronchial fluid dynamics. The mathematical model describes conditions in such respiratory tract airways of adult human subjects under various breathing conditions.The data indicate that the larynx exerts a pronounced influence on flows in distal airways. Fluid motion in the trachea and main bronchi include convective core flows with countercurrents along airway walls. The effects of these flow patterns may be to promote particle deposition at select sites within the larynx and tracheobronchial airways.
The effect if viscosity changes in the vocal folds on the range of oscillation. Journal of Voice, 1, 320-325 (1988)
B.K Finklehor, I.R Titze, and P.L Durham
Changes in vocal fold oscillation threshold pressure were induced in excised canine larynges by experimentally causing fluid movement into and out of the vocal folds. A range of oscillation threshold pressures was measured for each condition of hydration by varying length and glottal width. Decreased hydration (increased viscosity) raised the threshold of oscillation, and increased hydration (decreased viscosity) lowered the threshold of oscillation.
Breathing dry air causes acute epithelial damage and inflammation of the guinea pig trachea. J. Appl. Physiol. 64:1851–57
J.P. Barbet, M. Chauveau, S. Labbe, A. Lockhart.
Study investigated whether breathing dry air is capable of causing structural changes of the airways mucosa. The data demonstrated that a short exposure of the trachea to dry air causes marked epithelial lesions and local inflammation.