Table 6.

Investigations of systemic hydration induced voice changes in vivo employing pharmaceuticals plus humidification

#	Pt	Hydration Inducement	Hydration Measures	Hydration Status	Vocal Function measures	Main Results	Conclusions
Verdolini-Marston et al. (1990) (49)	3M 3F 25–46 yr healthy 4 singers 2 non-singers	Method Dry 30–35% humidity + no fluid 3tsp decongestant (Dimetapp) Wet 85–100% humidity ++water 2×2tsp mucolytic (Robitussin) Normal 40–55% humidity + no fluid control No medications Timing Humidity 4hr prior Decongestant 1hr prior Mucolytic start 4hr exposure + 30min prior	Method Not measured Timing Not measured	Pre Not measured Post Not measured	Measures PTP low mid high Timing Pre ✓ Post ✓	Minimal diff. between dry, control and wet conditions at speaking pitch ↑ pitch = ↑ PTP across conditions PTP lowest in wet condition at high pitch Slight ↑ PTP in dry condition compared with control condition	Validate the relationships between PTP & pitch, and PTP & VF viscosity Relative proportion of variance due to humidity & to systemic hydration is unclear
Verdolini-Marston et al. (1994) (51)	6F 18–33 yr otherwise healthy VF nodules or polyps 6m–5yrs 8m post onset 2 no voice training 4 singers 5 no therapy 1 therapy	Method Hydration 8x 160z water + 90–100% humidity 3×1 tsp (Robitussin) mucolytic Control 3×1 tsp cherry syrup 8 sets of 20 forefinger flexions 30–40% humidity + scented candles Restrictions-limit heavy voice use, alcohol & caffeine intake, smoke exposure Timing Medications 6 hourly Each treatment for 5 consecutive days	Method Pt report of fluid intake Timing Hydration prospective log Control retrospective report General questioning prior to	Pre Not measured Post Not measured	Measures PTP low mid high PPE Lx imaging 5-point scale Perceptual rating 5-point scale Acoustics jitter, shimmer, SIN ratios Timing Pre ✓ Post ✓	Overall improved performance following both placebo & hydration conditions, with hydration reported to be superior PTP - no sig. diff., trend present at high pitch only Lx scope - Less severe rating (sig.), but less than 1 point Perceptual Rating no sig. diff. Acoustics - treatment effects present, but no clear hydration effect Inconsistency across pt	Hydration may be of benefit in the treatment of vocal nodules & polyps Benefits of treatment may be present only while undertaking treatment Hydration effects appear to vary between individuals
Verdolini et al. (2002) (2)	2M 2F 21–28 yr healthy	Method Diuretic Lasix +4oz fluid/hr Anti-histamine +4oz fluid/hr diphenhydramine hydrochloride Placebo sugar pills +8oz fluid/hr Fluid & food control in between testing sessions Timing 4 days (1 daybreak), 16 hrs /day Active drug given 3 hours post arrival (following 4 pretreatment measures) Sugar pills 3–4/ day	Method Body weight Saliva viscosity Pt report of health Timing Measures taken each hour for 16 hours per day for 4 days	Pre Not measured Post Inferred from weight change and saliva viscosity	Measures PTP high PPE Timing Pre ✓ Post ✓	↑ PTP 5–12hrs post diuretic Antihistamine did not result in salivary change or PTP effects ↓ PPE at midday in placebo cond’n but ↑ for antihistamine No clear relationship of phonatory effort with other measures Saliva viscosity did not show reliable change across treatments or days	Respiratory system may retain fluids longer than other body parts during dehydration Changes in PTP may be due to VF viscosity and/or neuromuscular function PPE may not be reliable indicator of hydration status
Verdolini et al. (1994) (50)	9F 3M 20–30 yr healthy	Method Testing at 27°C Hydration 90% humidity +++water 2x 2tsp mucolytic (Robitussin) Dehydration 10–20% humidity +no fluid 2×2tsp decongestant (Dimetapp) Control 50% humidity + no fluid control 2×2tsp cherry syrup Timing 4hr exposure to humidity Mucolytic at start & 30mins prior Decongestant 60mins prior Control 120mins prior	Method Pt report of fluid intake Timing During testing	Pre Not measured Post Not measured	Measures PTP 10 conv. 80 PPE Timing Pre ✓ Post ✓	An inverse relationship between PTP & hydration level Sensitivity of PTP to hydration level progressively greater with increasing pitch sig. ↑PPE in dry condition vs the control & wet conditions No diff. between the control & wet conditions	Changes in PTP with hydration level are pitch dependent, with the greatest impact seen at high pitches PPE is less sensitive to changes in hydration level than PTP It would be better to base PPE on PTP task than conversational speech