MAXIMUM PHONATION TIME OF FUTURE PROFESSIONAL VOICE USERS

(1) Phonoaudiologist, Master by the Postgraduate Program in Human Communication Disorders at the Federal University of Santa Maria, RS, CNPq scholarship. (2) Phonoaudiologist of the Antônio Francisco Lisbôa School, LabVoz Collaborative –UFSM. (3) Phonoaudiologist, Associate Professor from the Department of Phonoaudiology at Federal University of Santa Maria; PhD in Applied Linguistics from the Catholic University of Rio Grande do Sul (4) Academic of the Phonoaudiology Course from the Federal University of Santa Maria.

the tendency to voice problems and the referred measures propose to show coordination between the levels of voice production 1 .
Thus, the present study aimed to verify the MPT of the vowels and correlate the results of the ė/e, s/z relationships and OMPT/ PMPT, according to gender, in future adult voice professionals with normal voice.

METHOD
The study was a transversal analytical type, with quantitative character.
The target population was composed of all subjects who sought a Phonoaudiology school clinic to perform vocal improvement, from March 2009 to July 2010.
To compose the study group it was adopted the following inclusion criteria: signing of the Informed Consent Form (ICF), being a student of course that would require professional use of the voice in the future profession 1,3,10 ; auditory thresholds within the normal range 5,[17][18][19]23,[25][26][27][28] , aged from 18 to 40, avoiding hormonal and structural changes of the period of voice change and aging 9,10,17,27 and present the average degree of zero to 0.9 in the aspects evaluated by RASATI 18,19 .
Exclusion criteria were: present reported history of neurological and/or psychiatric conditions that could interfere with the understanding of the orders during evaluation 1 , endocrinological, gastric and respiratory diseases 9,10,17,18,23,27,28 or stomatognathic system deviations that could influence vocal performance 8,17,18,27 ; presenting influenza and/or respiratory allergies at the time of the phonoaudiological assessment, because both can cause vocal fold edema limiting performance evaluations, with results which do not correspond to the usual standards of the subjects 5,10,17,23,27 ; hormonal changes due to pregnancy or the menstrual and premenstrual periods 9,10,23,27 ; having done therapy and/or previous ENT; sing in choirs ruling out the possibility the subject having received vocal and respiratory training with vocal techniques 17,18,27 ; complaints such as vocal voice failures; burning sensation in the throat, vocal fatigue and/or hoarseness because they could suggest disorders in laryngeal level and interfere with the results of the study 27 .
Audiometric screening was performed by means of the scan of pure tones by air conduction at frequencies of 500, 1000, 2000 and 4000 Hz, 25 dB in a soundproof booth (with Fonix, model FA -12, type I) 18,19,25 .An evaluation of the stomatognathic system verified aspect, tone, posture and mobility of the structures and their functions in order to apply the exclusion criteria above 3 .treatment of any voice disorder as well as voice enhancement.The importance of vocal assessment keeps throughout the treatment/enhancement as a means of measuring the possible evolutions of the patient and ensure proper timing of therapeutic discharge 10,15,16,[18][19][20][21] .
The measurement of maximum phonation time (MPT) is used to obtain pneumophonic data, being one of the most used in the practice of clinical voice assessment, because it is easily measured and is considered an objective acoustic measurement of glottic efficiency 9,10,[15][16][17]19,20,22 .
The MPT indicates the efficiency of the coordination between the levels of breathing and phonation, since, for maximum sustained phonation, the individual uses the maximum of her/her vital capacity (VC) to maintain a phoneme for as long as possible, reflecting the neuromuscular control and aerodynamic vocal production 10,16,17,19,20 .The VC can also change the values of MPT 9,11,[16][17][18] .
The extent of MPT can be used by phonoaudiologists, otolaryngologists and singing teachers as a pre-assessment to other forms of qualitative or quantitative assessment 9,16,19,20 .
The aerodynamic control of the emission with the progressive exit of the expiratory air can be quantitatively evaluated by the value of MPT/s/ and MPT /ė/, voiceless phonemes do use the vibration of the vocal folds, thus underlining the performance of breathing level phonation.The oscillatory component can be measured by the value of MPT/z/ and MPT /e/, as it is voiced phonemes that have vibration on vocal folds, showing the performance of the glottic level or phonatory to the emission.The relationship s/ z and the relationship ė/e, therefore, provide the assessment of the phonatory dynamics and laryngeal efficiency and respiratory 5,[9][10][11]15,16,18,19,23,24 .
Through the OMPT/ PMPT relationship it is possible to check the occurrence of glottic hypercontraction or air leak to phonation, because the PMPT is a prediction about the time that the subject should sustain the emission based on the values of VC, and OMPT is time that it was effectively performed by the subject (MPT /a/) 9,22 .
Based on the above, this research is justified by the lack of studies with the population of future voice professionals, as it is a population that has presents After the selection of the study group was collected the VC in the bipedal standing position, with dry spirometer Fami-Itá®, the subject was asked to conduct a maximal inspiration and maximal expiration into the device, positioned at the height of the patient 9,28 .It was considered for this study, the highest value obtained among the six collected samples, three with and three without nasal occlusion 28 .
To record the voices it was used a professional stereo digital recorder with unidirectional microphone (Zoom brand, model H4N), placed four inches from their mouth, with an angle of 90 ° directional pickup 17,19,30 , in a room with ambient noise less than 50 dB SPL, measured by digital sound pressure level meter Instrutherm, model-Dec 480 9,27,30,31 .
As normal range for MPT, we used the interval of 15 to 25s for women, and 25 to 35s for men 9,16,27 .Values under these intervals were considered indicative of air escape during phonation and higher values indicate excessive coaptation in the vocal folds 9,16,19,27 .
We calculated the s/z ratio by dividing the larger MPT/s/ by the higher MPT /z/, considering the normality between 0.8 and 1.2.Values below 0.8 indicate excessive coaptation of the vocal folds and values above 1, 2 indicate air leakage during phonation.According to literature, the same values are considered for the evaluation of both genders, therefore, these measures, the group has been reported as a whole and not divided by gender  The ė/e relationship, division of the higher MPT/ė/ by the higher MPT /e/, was classified with the same intervals of normality of the s/z relationship 23 .
The OMPT/PMPT relationship was calculated starting by multiplying the VC by the value 0.0051 for female subjects, and by multiplying the VC by the value 0.0057 for the male subjects, obtaining the value of the MFT each subject 9 .After OMPT, or the largest value of MPT /a/ was divided by the PMPT values were considered within the normal range between 0.9 and 1.1.Lower values were considered suggestive of air escape during phonation and higher values suggestive of excessive coaptation in the vocal fold 9 .
The study was approved by the Ethics Committee in Research (016945/2010-76) and the Considering that the scale RASATI is an effective tool in identifying perceptive auditory voice disorders related to irregular vibration of the vocal folds (glottal source) 29 and having as methodological basis in other studies 19,21,30,31 , the criteria used to classify the voices in this research was based on the average responses of three phonoaudiologist judges with expertise in voice, for each parameter in the RASATI scale.In this study it was established as a criterion of vocal normality, the average degree of 0.9 to the aspects evaluated by RASATI 19,26 .
The judges performed the analysis with specific protocol for RASATI, independent of each other and ignoring the research objectives.The largest MPT of vowel /a/ of each subject was doubled and the total of those emissions was organized and presented randomly for each judge, unmarked and without knowing that they were evaluating the same emission twice 5,9,29,30 .
To check the intra and inter rater agreement it was applied in calculating the Kappa coefficient on the average responses of each judge for each RASATI parameter, obtaining the average coefficient of intra and inter rater.Results were considered to be between 0.8 and 1, almost perfect agreement; between 0.6 and 0.8, good agreement; between 0.4 and 0.6, moderate, between 0.2 and 0.4, regulate, among zero and 0.2, slight; between -1 and zero poor 22 .The judge one obtained Kappa coefficient of 0.7, Judge two 0.68 and Judge three 0.71.The judges 1 and 2 obtained inter rater agreement of 0.66,to 1 and 3, out of 0.68, and the 2 and 3 out of 0,62.
The results of this assessment were decisive in the classification of voices as normal or altered and hence an inclusion criterion, because it was not possible to hold the ENT examination in all subjects.It judged the perceptive auditory analysis of MPT procedure most suitable and reliable for the selection of subjects for the presence or absence of dysphonia, since the MPT is widely described in the scientific literature with emphasis on the detection of diseases in glottic level 5,9,11,18,19,23,31 .
We evaluated 86 subjects.One was excluded for having hearing loss, five were younger than 18 years, and 18 were excluded because their average grade above 0.9 on the RASATI parameters.
Therefore, the study group included 62 subjects, 12 men aged from 20 to 35 years old (average 24,25) and 50 women aged from 18 to 29 years old (average 21,42).Although the group of men has been outnumbered, we chose to keep them in the study for the enrichment of the data, taking care to not make comparisons of results between the genders due to the numerical difference between the groups.The classification of the correlation values obtained was: very weak correlation (0 to 0.19); weak correlation (0.20 0.39), moderate correlation (0.40 to 0.69), a strong correlation (0.70 to 0.89); very strong correlation (0.90 to 1.00).
As the variables were not normally distributed, it was not used average values in the tabulation of results.

RESULTS
ICF was written as recommended the 196/96 rule of the National Commission of Ethic in Research (CONEP/1996).
After tabulating of the data, we tested the normality of the variables (Lilliefords test) and opted for the Spearman correlation test to correlate the results of the relationships of s/z, ė/e and OMPT/ PMPT.To compare two proportions we used the binomial test.The level of significance was 5% (p ≤.05).The s/z relationship is proposed to verify the occurrence of muscle hyper component and lack of coaptation of the vocal cords of the relevant data for dysphonia 5,9,22,28 .
Through the results obtained in this study, it was observed that the s/z relationship of the study group was significantly as expected, suggesting proper coordination between breathing (Table 2).The data are similar to those obtained in other studies, such as in a survey of 40 undergraduate students, which compared the results of the s/z relationship in men and women (20 men and 20 women) with normal voices and found s/z relationship values close to one, with no significant difference between the genders, although the isolated MPT /s/ and /z/ were significantly higher in men 5 .But in a study with seven women, future teachers of physical education, three evaluations were performed, one at the beginning of the semester in which the academic began the internship, the other during the midterm and the last at the end of the semester.In the first evaluation, we found the average s/z of 1.15, 1.22 in the second, and in the last 1.90, suggesting increased incoordination between breathing with increased vocal demand without adequate preparation 25 .
It is important to note that a measure should not be interpreted in isolation, but in conjunction with others, since altered MPT /s/ and /z/ may result in a relative normal s/z, leading to false negative 19,28 .
This study showed a significant difference in favor of the increased values of the ė/e, when compared to lower values, showing that most of the studied group concentrates with increased values, suggesting air leakage during phonation (Table 2), being different from those results found in s/z relationship.
As the study group did not have voice problems or a history of problems in breathing level, MPT results and s/z and e/ė relationships, suggest pneumophonoarticulatory incoordination.This may be a risk factor for the development of dysphonia with increasing vocal demand, which is likely to occur at the time that future voice professionals begin their professional activities 5,6,8.Another important finding in this study was that the relationships s/z and ė/e presented moderate positive significant correlation, showing that its results correspond.Indeed expected, since .

Table 3 -Correlations between variables: OMPT/ PMPT relationship, s / z relationship, and the ė/e relationship
7f the group presented results of the s/z within the normal range7.In another study, conducted with adult women, with and without vocal nodules, there was a similar result, as the group without vocal nodules, 100% presented results of normal s/z relationship and in the group with vocal nodules, 70% had normal values 30% aerodynamic prevalence and no women had increased values 27 .