Author, date and country | Patient group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
---|---|---|---|---|---|
Paes, Zambon, Yamasaki, Simberg and Behlau 2013 Brazil and Finland | 25 female teachers with diagnosis of chronic behavioural dysphonia (5 years +) performed 10 tokens of sustained phonation into a straw in water. | Cohort study | Self- assessment (rating vocal comfort and voice quality as better, equal or worse than before exercises), auditory perceptual analysis (blinded rating of whether one recording was similar or better than the other) and acoustic evaluation (blinded visual analysis of instability of tracing, subharmonics, noise at high and low frequencies and series of harmonics). | Statistically significant result for self-rating (68% reported improved vocal comfort; 52% reported improved voice quality), auditory perceptual analysis of counting (60% rated as improved) and acoustic measures of instability, subharmonics, noise at high frequencies and fundamental frequency. No significance found on auditory perceptual rating of sustained vowel or on acoustic measures of noise at low frequencies and harmonic series. | No control group No sample size estimates No long-term effects measured Low sensitivity of rating scale |
Guzman, Higueras, Fincheira, Munoz, Guajardo, Dowdall (2013). Chile. 2013 Chile | 41 primary school teachers with mild dysphonia (GRBAS = 1 for grade and breathiness) allocated to experimental group (four phonatory tasks with straw) or control group (four phonatory tasks with /a/). | Control trial | Acoustic measures using long-term average spectrum pre- and post-treatment, providing information about mode of phonation (L1 – L0 ratio), noise in the glottal source (ratio between 1-5khz and 5-8 khz) and spectral slope declination (alpha ratio). Speaking fundamental frequency also measured pre- and post-treatment. | Statistically significant result on all measures for experimental group except for speaking fundamental frequency. | No sample size estimates No long-term effects measured Only looks at mild dysphonia Diagnosis not defined Unclear methodology eg if randomly allocated |
Costa, Costa, Oliveira and Behlau 2011 Brazil | 23 individuals with benign vocal fold lesion (GL) 25 without performed sustained phonation into a straw for a period of one minute. | Cohort study | Self- assessment of voice (easier voice, better voice, easier and better voice, no difference), blinded perceptual auditory evaluation (mark the best segment or lack of difference in paired recordings), acoustic analysis (fundamental frequency, jitter and shimmer on sustained vowel) and laryngoscopy (constriction and phonatory gap). | Statistically significant result for self-rating of voice in the lesion group. No other significant results. | No sample size estimates No long-term effects measured Exercise only performed for one minute Low sensitivity of rating scale |