From the Research
There is no direct comparison between 0.9% sodium chloride and 0.7% sodium chloride for vocal fold hydration in the provided studies, but based on the available evidence, 0.9% sodium chloride (normal saline) is the preferred option for vocal fold hydration due to its isotonic properties and ability to maintain the viscoelastic properties of the vocal fold mucosa. The primary goal of saline hydration is to maintain the viscoelastic properties of the vocal fold mucosa, which is crucial for proper vibration during phonation. Adequate hydration helps reduce phonation threshold pressure (the minimum pressure needed to initiate vocal fold vibration) and can help prevent vocal fatigue and injury, particularly for professional voice users.
- The study by 1 found that 0.9% normal saline had the best treatment effect for decreased voice stability caused by vocal fold dehydration, compared to 5% hypertonic saline and double-distilled water.
- Another study by 2 found that nebulized isotonic saline (0.9% Na+Cl-) improved voice production in patients with Sjögren's syndrome, an autoimmune disease causing laryngeal dryness.
- The study by 3 found that hydration affects vocal fold vibration by altering tissue rheologic (or viscoelastic) properties, and that 0.9% saline can help maintain the viscoelastic properties of the vocal fold mucosa.
- Although the exact difference between 0.9% and 0.7% sodium chloride is not directly compared in the studies, the available evidence suggests that 0.9% sodium chloride is the preferred option for vocal fold hydration due to its isotonic properties and ability to maintain the viscoelastic properties of the vocal fold mucosa.
- The 0.7% solution is slightly more hypotonic, which could potentially cause more cellular swelling due to osmotic pressure differences, but there is no direct evidence to support this claim in the context of vocal fold hydration.
- In clinical practice, 0.9% saline can be used in nebulizers or as a nasal spray, typically administered 3-4 times daily or as needed when experiencing vocal fatigue, with each session lasting about 5-10 minutes if using a nebulizer.