Monday, 30. November 2009

Inhalation of NaCl solution mitigates exhalation of infectious bioaerosols

Humans exhale bioaerosols that serve as vectors for the spread of a range of viral and bacterial infections, including influenza, varicella-zoster virus (chickenpox), measles and tuberculosis. A study conducted by a team of German and American researchers1 has demonstrated that inhaling an NaCl solution significantly diminishes the expiration of pathogen-bearing bioaerosol droplets over a relatively long period of time. Future research in this area will examine the question of whether this finding can produce a method of reducing the risk of droplet infection that is simple, efficient and cost-effective in equal measure.

The droplets that transmit infection are < 1μm in size, since larger drops are filtered out within the respiratory tract due to gravity sedimentation.
The study, which incorporated in vivo experiments involving 11 test subjects of various ages, found that approximately one half of the group produced significantly more bioaerosols that the other half during normal breathing. The researchers therefore concluded that approximately 50% of the population is responsible for transmitting 98% of the infectious diseases that are spread by droplet infection.

The study showed that administering a 0.9% isotonic NaCl solution with the PARI LC PLUS nebuliser for six minutes diminished the expiration of bioaerosols by 72% among the individuals in the "high-producer" group, who had previously generated in excess of 500 bioaerosol particles per litre of expired air over a period of six hours. The effect of the inhalation lasted for six hours.

The effect of NaCl inhalation is apparently related to a change in the physical properties of the fluid that lines the human respiratory tract. Administering saline solution appears to modify the mucus layer of the respiratory epithelium, resulting in increased surface tension. This change favours the formation of larger bioaerosol droplets. In their experiments, the researchers succeeded in increasing the size of the droplets to > 10μm. Droplets of this size are effectively filtered out of the expired air by inertia within the respiratory tract.

The researchers plan to refine their method in future studies and to investigate the effects of a range of additional parameters, for example, the role of surface viscosity and elasticity, as well as various physiological and environmental factors.

Conclusion: Inhaling saline solution is a simple yet extremely efficient and cost-effective way to reduce the risk of infectious diseases being spread by droplet infection. A practical benefit of this method is that there are no known side-effects or interactions with other medication. In addition, it has been shown to be effective for all viruses and bacteria that are spread by droplet infection. PARI's NaCl Inhalation Solution, which supplies saline solution in convenient plastic ampoules, and the inhalation devices in the PARI BOY range, incorporating the PARI LC SPRINT nebuliser, are ideally suited to helping reduce the spread of infection in this way.

1D.A. Edwards, J.C. Man, P. Brand, J.P. Katstra, K. Sommerer, H.A. Stone, E. Nardell, G. Scheuch: Inhaling to mitigate exhaled bioaerosols, PNAS Dec 14, 2004, vol. 10, no. 50, 17383 - 17388

For more information about PARI products and the study cited here, please contact:

Dr. Rosina Ledermüller
Phone: +49 (8151) – 279 213