Maximum phonation times and vital capacity in dysphonic women

Objective: to verify the correlation between vital capacity and maximum phonation times of / ė / (unvoiced) and /s/, as well as compare and relate them with the professio nal voice use and age in women with functional or organic-functional dysphonia. Methods: a retrospective research with 524 records of dysphonic patients from a school clinic, including young adult women with a speech-language diagnosis of functional or organic-functional dysphonia based on medical reports. Neurological and psychiatric alterations, previous speech therapy treatment, symptoms of flu or allergies on the day of evaluation, pulmonary disease, organic dysphonia diagnosis, and hearing loss, were excluded. The sample resulted in 14 women with functional dysphonia and 21 with organic-functional dysphonia. Data on professional voice use, as well as results for vital capacity and maximum phonation times were collected. The data were statistically analyzed at a 5% significance level. Results: There was a positive correlation for both groups of dysphonic patients between the maximum phonation times of / ė / and of /s/, as well as the maximum phonation times of / ė /, /s/, and vital capacity. Higher values for vital capacity and maxi mum times of /s/ and / ė / for voice professionals were seen. The maximum phonation times of / ė / were lower than those of /s/. Conclusion: as the maximum phonation times of / ė / increased, the maximum phona tion times of /s/ and the vital capacity also augmented in both groups, demonstrating the interrelation among these variables; there was no relation with the other variables studied.


INTRODUCTION
The respiratory system has a vital role for the proper production of voice, since the expiration of air works as the activating source of emission. Aerodynamic measures of vocal emission are one of the dimensions of vocal evaluation. They expose the control conditions of the respiratory forces and the glottic efficiency, as well as the compensatory vocal behaviors of individuals, especially those with vocal disorders [1][2][3] . Among these measures, some standardized stand out such as Vital Capacity (VC) and the Maximum Phonation Times (MPT), which aid the identification of voice alterations for the individual 2,4-6 .
VC refers to the maximum expiration that the individual can perform after a maximum inspiration 3,[5][6][7][8][9][10] . Results may vary according to stature, age, gender, proper health conditions, physical training, alcohol or smoking habits, and professional voice use. The values found vary from 2,100 ml to 3,300 ml for women, and 2,200 ml to 4,000 ml for men 5,6,9 . The VC may influence the MPT despite not determining it, given that both measures depend on the airflow control coming from the lungs 6,7,9,11 .
The MPT is obtained through the sustained emission of vowels, fricatives, and/or counting of numbers during a prolonged expiration, in normal pitch and loudness. Besides helping to describe vocal behavior, it is used to verify how the patient controls the aerodynamic forces of the expiratory air current and the myoelastic forces of the larynx 2,4,6-8, [12][13][14][15] . It allows characterizing the glottic source regarding its muscular and muco-undulatory functioning and its vocal quality, seeing that some alterations are better observed in the sustained emission of isolated phonemes 6,8,16 .
MPT may be measured, among others, using the fricative phoneme /s/ and the sustaining of the voiceless /e/ (/ė/), both unvoiced emissions. MPT/s/ measures the respiratory control for not having vibrations of the vocal folds 12,13 but suffers articulatory influence because it presents a constriction at the alveolar articulatory level 3,17 . The production of the MPT /ė/ seems to be more reliable to analyze blow control through exclusive respiratory support, evaluating the control of the respiratory musculature in the sustaining of the expiratory air column during a voiceless emission 3,5,16 .
The unvoiced MPTs are important given that, during phonation, the balance and control of respiratory forces are essential. Therefore, its use in the evaluation of all types of dysphonia and voice professionals is emphasized. Such measures are necessary to verify the performance of the respiratory level 1-6 since it needs to be balanced with the with the other vocal production levels so as not to generate pneumo-phono-articulatory incoordination 3,6 . If the aerodynamic forces are not in accordance with the vocal demands, such as with voice professionals, it can lead to hyperfunction behaviors generating tension to the phonation, brusque vocal attacks, fatigue, and dysphonias 6 . Such aspects, in turn, may lead to the emergence of functional laryngeal unbalances and organic-functional lesions.
Voice alterations due to structural laryngeal affections on the vocal folds, caused by the incorrect use of the voice, are called organic-functional dysphonias (OFD) 4,7,11,14,17 .
On the other hand, functional dysphonia (FD), although not consensual, consists of a behavioral voice problem in the absence of organic, neurological, or psychological etiology 18 . It presents predisposing factors such as genetic susceptibility, psychological issues, and, chiefly, the vocal behavior that may be compromised in voice professionals who are unaware of vocal health care 18 .
The female gender may present lower MPT and VC values compared to the male gender 6 . Voice professionals may present the same VC values of individuals who do not use their voice professionally 6 . As for the MPT, in a study with voice professionals, teachers, discretely larger MPT values compared to the control group were observed 19 , with a similar result being found in a longitudinal study with teachers who presented larger MPT values when compared to people who were not voice professionals 20 . In another study with Iranian teachers, the opposite result was found: the study group presented lower MPT values, a finding attributed to the pneumo-phono-articulatory incoordination of the teacher group 21 .
Despite the measures approached in this work being widely used in clinical practice, scientific studies relating them to each other are scarce. Correlating VC and unvoiced MPT values may contribute to enlighten whether VC is sufficient in sustaining the unvoiced MPT, seeing that it depends on the pulmonary air volume 1-3 . That is, besides a normal VC, it would also be necessary to have a proper expiratory muscle control to sustain the unvoiced MPT [1][2][3]5,6,7,9,11,16 . These results would reverberate in the objectives of the speech therapy treatment for behavioral dysphonias (FD and OFD), in which pneumo-phono-articulatory incoordination is often observed 3,6 . The same occurs regarding individuals who are voice professionals and need adequate pneumo-phono-articulatory coordination 18 to avoid overcharging one of the voice production levels -usually the glottic or phonatory level -, possibly developing laryngeal organic-functional lesions 4,7,11,14,17 . Considering the exposed, this study had the purpose of verifying the correlation among VC, MPT/ė/ (unvoiced), and MPT/s/, as well as compare and relate them with the professional voice use and the age of women with FD or OFD.

Ethical Aspects
An analytical, observational, cross-sectional, quantitative, and retrospective study using a database of patients attended at the voice sector of a speech therapy school clinic.
This study was approved by the Research Ethics Committee (REC) of the Universidade Federal de Santa Maria -UFSM (no. 56444616.0.0000.5346), with all subjects signing the Term that authorizes the use of data from the medical charts at the school clinic.

Inclusion criteria
To compose the sample, we considered as inclusion criteria the following information from the database: adherence to the term of medical chart data usage; female gender; adult age range (19 to 44 years of age) to discard alterations due to the vocal change period and to the influence of hormonal and structural alternations due to aging 6,7,17 ; speech-language diagnosis of FD or OFD based on the otorhinolaryngologist's report; data on the professional voice use and measures of VC and MPT for /s/ and /ė/.

Exclusion criteria
We excluded from the study: a record of the report or diagnosis of neurological or psychiatric alterations 3,5 ; a record of speech therapy treatment before the evaluation date 3,6,16 ; having symptoms of flu or allergies on the day of evaluation 5 ; report or diagnosis of pulmonary disease 5,7 ; diagnosis of organic dysphonia; and diagnosis of hearing loss 5,7 .
The database had a total of 524 tabulated records of patients. After applying the inclusion and exclusion criteria, the sample was constituted by 35 women. The mean ages were of 28.4 years in the FD group (n=14) and 27.3 years in the OFD group (n=21). The women who were voice professionals were two choralists, four teachers, and one community health agent (n=7), while 28 were not voice professionals.

Data collection
When coming to the school clinic in the initial collection of the MPT/ė/ and MPT/s/ values, the patients were in orthostatic position and sustained the emissions during a prolonged expiration in their usual loudness. At the emission of the MPT/ė/, the patients were instructed to emit the /ė/ without vocalization and any noise whatsoever, maintaining the same articulatory posture of the /e/ vowel 3,5,16 and sustaining the air as if it were a "very light breath" 16 .
The MPT/ė/ and MPT/s/ measures were timed with a digital chronometer in seconds thrice, and we selected the highest value obtained for each measure 3,5,6,22,23 .
Due to the lack of studies about the MPT/ė/, as a normality standard, we considered the interval from 10.43 5 to 18 s 3 , while for MPT/s/ the range was from 15 to 25 s 3,6 . MPT/ė/ and MPT/s/ values below the normality standard were considered suggestive of compromised expiratory control to phonation 5 , while values above the normality were considered better than expected relative to the expiratory control to phonation.
We measured the VC using a dry Fami-Itá® spirometer and registered the results in milliliters (ml). The patients were guided to do a deep inspiration followed by a maximum expiration on the mouth of the spirometer's tube, kept at the same height as the patient's mouth. We considered the largest value among three readings with nasal occlusion and three readings without nasal occlusion 5,8 .
As the normality standard for VC for women, we adopted values from 2,100 ml up 5,6,8 . We considered lower values suggestive of respiratory compromise, possibly making sustaining phonation difficult 5,6,8 . The measures were collected by different evaluators who followed the above description. The data on the professional voice use was obtained through the record of the interview/anamnesis with the patient. All patients were evaluated by an otorhinolaryngologist at the school clinic or private physician, with the medical report attached to the patient's chart. The speech-language diagnosis of the type of dysphonia was reached based on the otorhinolaryngologist's report 6 . We considered as OFD the presence of vocal nodules, polyps, edema, and thickening of the vocal folds, and as FD the minimal structural alteration of the coverage, glottic clefts, and incorrect vocal habits.
respectively. The average VC values for the FD and OFD groups were, respectively, of 3,157 and 2,986 ml, thus within the normality standards. The majority of the sample was of subjects who were not voice professionals (80%).
The statistical results are exposed in Tables 1, 2, and 3. Table 1 shows the descriptive analysis of variables age, VC, MPT /ė/, and MPT /s/ for each group and the whole sample, presenting the mean, standard deviation, and minimum and maximum values of such variables. Table 2 shows the correlation among MPT /ė/, MPT /s/, and VC, with all variables presenting a positive correlation.

Data analysis
The data was tabulated, descriptively analyzed, and submitted to the statistical analysis through the statistical tests of Pearson Correlation, ANOVA to compare among the variables, and Chi-Squared to verify the relation among the qualitative data. We adopted the 5% significance level (p ≤ 0.05). In the statistical analysis, we used the SPSS V17, Minitab 16, and Excel Office 2010 software.

RESULTS
Considering MPT /ė/, we found a mean of 12.1 s for the FD group and 10.7 s for the OFD group. For the MPT /s/, the means were of 14.9 and 13.6 s,

DISCUSSION
There was a significant positive correlation between MPT/ė/ and MPT/s/ for both groups analyzed ( Table   2). This positive correlation was also found in a study that compared these variables and stature in a group of adult women with normal voices 24 . Both measures evaluate the respiratory muscle control in sustaining the expiratory air column during a voiceless emission and, therefore, this result was expected.
The results also showed a significant positive correlation between MPT /ė/ and MPT /s/ and the VC for both groups analyzed (Table 2). This demonstrates the influence of VC values over the MPT /s/ and MPT /ė/, that is, the higher the VC, the higher the unvoiced MPT tends to be, seeing that both measures depend on the control of the airflow from the lungs, agreeing with the literature 3, [6][7][8]11,13 . For this reason, these variables are used to describe pneumophonic coordination.

CONCLUSION
This work verified that, as the MPT /ė/ value increased, the MPT/s/ value also increased, as well as the VC and vice-versa in both FD and OFD groups, demonstrating the interrelation among these variables.
There was no difference among the variables profes- The literature mentions that MPT values may vary according to age, such as with elders, in which the reduction of this measure is due to laryngeal and pulmonary modifications due to aging 3,6,12 . However, in this study, there was no significant correlation among MPT, VC, and age, probably due to the chosen age range having excluded women over 44 years old. In this study, the average VC of the FD and OFD groups presented itself within the standards found in other studies with adult women 1,2,5,7,15,27,28 .
There was no significance regarding the VC, MPT /s/, and MPT /ė/ measures and age among voice professionals when compared to the group that did not use their voice professionally, neither when compared to the FD and OFD groups ( Table 3). The results were similar to the study with voice professionals 26 which compared the MPT of teachers and non-teachers and found reduced values in both groups.
It is known that VC may be normal in dysphonic