Avaliação do respirador oral : uso do espelho de Glatzel e do peak nasal inspiratory flow Mouth breathing evaluation : use of Glatzel mirror and peak nasal inspiratory flow

Purpose: Purpose: To compare the use of the Glatzel mirror and peak nasal inspiratory flow in the evaluation of mouth-breathing participants and to analyze the correlation between these instruments. Methods: Sixty-four children were evaluated — 32 mouth breathers and 32 nasal breathers; the children were aged 4 to 12 years. The mouth breathers were subdivided according to the cause of obstruction by a multidisciplinary team. The Glatzel mirror and peak nasal inspiratory flow were used in both groups to evaluate patency and nasal airflow. Data were then subjected for statistical analysis. Results: The Glatzel mirror allowed us to differentiate the breathing mode considering gender, age, weight, height, and body mass index, but it did not help in identifying the cause of mouth breathing. The peak nasal inspiratory flow did not allow differentiation of the breathing mode and identification of the cause of mouth breathing. In our sample, there was no correlation between the instruments used. Conclusion: The Glatzel mirror was reliable in identifying participants with and without nasal obstruction, although it was not possible to differentiate subgroups of mouth breathers using this instrument. The peak nasal inspiratory flow showed differences only between nasal breathers and surgical mouth breathers. Low correlation was found between these two instruments. 237 Avaliação do respirador oral CoDAS 2013;25(3):236-41 InTRODUçãO A respiração oral pode acarretar diversos prejuízos à saúde, tais como alteração de tônus da musculatura orofacial, alterações oclusais, desvios dos padrões normais de mastigação e deglutição, alterações de fala, distúrbios do sono, problemas de aprendizagem, entre outros. Uma boa avaliação e, consequentemente, um bom diagnóstico, precedem uma intervenção fonoaudiológica eficaz. Diversos profissionais são responsáveis pela avaliação e tratamento dos indivíduos respiradores orais, mas é atribuição do médico otorrinolaringologista definir o fator causal da alteração do padrão respiratório. No entanto, muitos pacientes do Sistema Único de Saúde (SUS) aguardam, por um período prolongado, a oportunidade de serem submetidos a uma avaliação otorrinolaringológica e exames que possam diagnosticar o fator causal do quadro de respiração oral. Desta maneira, é importante que o profissional fonoaudiólogo disponha de instrumentos de avaliação que possam, nesse intervalo de tempo, identificar possíveis obstruções nasais, definindo desta maneira condutas e prognósticos baseados em evidências. Para tanto, se faz necessária a utilização de instrumentos rápidos, simples e baratos, que forneçam medidas acuradas do que se pretende avaliar. Atualmente, diferentes instrumentos têm sido utilizados para avaliar a permeabilidade e resistência aérea nasal. Na prática clínica fonoaudiológica, o Espelho de Glatzel (EG) é empregado para avaliação do modo respiratório, medindo o fluxo aéreo nasal por meio da condensação do ar expirado em uma placa de metal, auxiliando na identificação de possíveis obstruções nasais. Estudos de validação desse método inexistem na literatura, o que torna questionável a confiabilidade das medidas por ele fornecidas. O peak nasal inspiratory flow (PNIF) é outro instrumento que pode auxiliar na detecção de possíveis obstruções nasais. É composto por uma máscara de silicone acoplada a um êmbolo graduado que mede o fluxo aéreo nasal máximo durante uma inspiração forçada. Ambos os instrumentos encontram-se disponíveis no mercado e são de fácil aquisição para o profissional da Fonoaudiologia. É importante ressaltar que, para o uso de qualquer instrumento, é indispensável que sejam seguidas as orientações do fabricante e que o profissional conheça os benefícios e contraindicações que porventura possam existir. Considerando-se, portanto, a alta ocorrência de pacientes respiradores orais, bem como as consequências dessa alteração e a necessidade de uma avaliação fonoaudiológica eficiente, este estudo teve como objetivo comparar o uso do EG e do (PNIF) na avaliação de indivíduos respiradores orais, bem como analisar a correlação dos dois instrumentos.


InTRODUCTIOn
Mouth breathing may bring many health problems such as changes in orofacial muscle tone, occlusal changes, chewing and swallowing pattern deviations, speech disorders, sleep disorders, learning disabilities, among others (1) .
Good patient assessment and, thus, good diagnosis precede an effective speech therapy. Many professionals are responsible for assessment and treatment of mouth breathing patients, but the otolaryngologist is concerned with the definition of the triggering factors of changes in the breathing pattern. However, many patients relying on the Brazilian Public Health System (SUS) have to wait long times for an opportunity to consult an otolaryngologist and to go through exams that can diagnose the causes of mouth breathing (2) .
It is important that the speech therapist hold assessment tools that can identify possible nasal obstructions, thus defining management and prognosis based on evidence (2) ; so the use of easy-to-manipulate, simple, and cheap, but accurate, instrument is necessary. Nowadays, different tools are used to assess nasal patency and resistance. The Glatzel Mirror (GM) is used in clinical practice to assess breathing mode, measuring the nasal airflow by condensation of the expired air, which helps in the identification of nasal obstruction causes (3)(4)(5)(6)(7) . The literature lacks studies on the validation of this method, so one can question the reliability of the measures it provides.
The peak nasal inspiratory flow (PNIF) is another instrument that can aid in the detection of nasal obstruction causes (8)(9)(10)(11) , composed of a face mask attached to a graded flow meter that measures the nasal airflow at forced inspiration (12) . Both instruments are currently available in the market and can be easily acquired by Speech Therapists. It must be underscored that all instruments must be used in compliance with the manufacturer's orientation and that the professional should be familiar with all benefits and contraindications related to their use.
Considering the high prevalence of mouth-breathing patients, the consequences of such disorder, and need for an effective evaluation, this study aims to compare the use of the GM and PNIF to assess these patients and to analyze the correlation of both instruments.

METHODS
The research project was approved by the Ethics Committee of four institutions, with protocol number 541/09, and all participants had to sign the informed consent form. This was a cross-sectional descriptive study conducted with a convenience sample comprising participants from an outpatient clinic for mouth-breathing patients and from Elementary and Middle schools of Belo Horizonte. The above-mentioned outpatient clinics admits 2-to 12-year-old children, but only those diagnosed with mouth breathing are followed-up by an interdisciplinary team comprised of otolaryngologists, allergists, orthodontists, and a speech therapist. All children were submitted to skin prick testing and nasofibroscopy.
Sixty-four individuals of both genders and aging from 4 to 12 years were assessed, of which 32 were mouth-breathing patients (MB -case group) and 32 were nasal-breathing patients (NB -control group). Patients were divided by gender, age, weight, and height in groups, for these are important variables for PNIF (2) . Mouth-breathing patients were divided into four subgroups by cause of nasal obstruction -allergy, surgery, allergy-surgery, and function -after being classified by an otolaryngologist and an allergist. This characterization is summarized in Table 1.
Inclusion criteria for the MB Group were patients from the outpatient clinics of the institution and, therefore, diagnosed by different professionals with mouth breathing. Inclusion criteria for the NB Group were children without complaint or evidence of nasal obstruction according to speech therapist evaluation (13) , anamnesis and parents' interview (14) . Participants whose caregivers did not sign the informed consent form were excluded from both groups, as well as those who reported chronic use of nasal decongestants in the past 3 months, clinical picture of airway infection upon anamnesis, chronic obstructive pulmonary disease, cardiovascular disorders, craniofacial abnormalities or neurologic disorders, self-debasing cognitive distortions, and those not capable of performing the peak inspiratory flow maneuvers.
Exclusion criteria for control group patients who gave affirmative answers for one or more items of the anamnesis form: allergy, rhinitis, recurrent flu, waking up with dry mouth Patients who could not keep their mouth closed loosely during the 5-minute observation were also excluded. Participants excluded from the control group due to suspected mouth breathing were referred to otolaryngological evaluation. The management of mouth-breathing patients was carried out at the outpatient clinics while they were waiting for the multiprofessional evaluation. To compose the control group, invitations with the informed consent form and the anamnesis report were sent to 140 caregivers of students from Elementary and Middle schools of Belo Horizonte. In response, 109 forms and reports were returned, out of which six were not filled in and five were not correctly filled in. According to the anamnesis report, 58 children were excluded from the study because they presented at least one characteristic indicating breathing obstruction and eight because they presented a clinical sign indicating alteration in breathing mode at speech evaluation.
Each child was taken to a room for evaluation, where they could be weighed, measured, and oriented to perform a nasal cleansing action (15) to eliminate the possibility of airflow obstruction due to excess mucous. Afterward, the child was supposed to remain sitting and breathe normally with eyes closed, while a researcher would perform the GM examination. The instrument was placed under the nose of the child, at the anterior nasal spine, and after 1 minute of habitual expiration and inspiration, the condensation area was marked on the mirror using a proper pen. Afterward, the indication was put on a reference note for the Altmann ® mirror. The annotations were then scanned one by one in a HP PSC 1315 scanner, so the area could be measured in cm 2 using the software AutoCAD 2009. The GM was sanitized with 70% alcohol.
The measures of peak inspiratory flow were made using the In-Check Inspiratory Flow Meter (Clement Clarke International). Patients were briefly oriented about how to use the instrument; they were supposed to stand up, put on the face mask, covering the regions of the mouth and nose, breathe out and then breathe in at their utmost. We performed three measures and considered the highest value for the analysis (9)(10)(11)(12)16,17) .
Data were analyzed using the SPSS statistical program, with significance level set at 5%. Age group, weight, height, and body mass index (BMI) were grouped according to the sample distribution, by quartiles.
To assess the distribution of quantitative variables, we used measures of central tendency and dispersion and the Kolmogorov-Smirnov normality test. The Mann-Whitney test was applied to compare medians and the Spearman's coefficient to assess the correlation of PNIF and the GM results.

RESUlTS
A descriptive analysis of the quantitative variables was made, and the Kolmogorov-Smirnov test showed a normal distribution only for the variables of height, weight, and PNIF measures ( Table 2).
In the GM data analysis, we found a difference between mouth and nasal-breathing patients for all variables, except for one weight (22.40-27.29 kg) and one height band (0.95-1.21 m), being the nasal breathing higher. As to PNIF, only one height band (1.22-1.27 m) presented difference (Table 3).
Considering the subgroups, GM was able to distinguish allergic, surgical and allergic-surgical nasal-breathing patients, as well as allergic and functional mouth-breathing patients. PNIF was only able to distinguish surgical nasal-breathing patients though (Table 4).
Correlation between PNIF and the GM was analyzed for each group of individuals -divided as to breathing mode -and was proven low in all situations, with no evidence for significant association between them (Table 5).

DISCUSSIOn
After review, we found that the literature lacks studies on GM; so there are no reference values, standardization data, or proof of efficacy. This instrument has been used in some studies aiming to assess the nasal airflow (3)(4)(5)(6)(7)(18)(19)(20) . PNIF has been widely used in studies aimed at the assessment of nasal airflow, especially in allergic rhinitis patients. The studies found in the literature address data on sensibility, diagnosis accuracy, reproducibility, and reference values of the instrument (8)(9)(10)(11)16,17,21,22) . Our sample showed higher prevalence of mouth-breathing patients in the age group of 6-10 years (Table 1), in agreement with findings of the literature (23,24) -even though some studies have not identified differences concerning age (7,19) . The dominance of mouth breathing among patients aging 6-10 years may be justified by the occurrence of physiological tonsil hyperplasia (pharynges, palate, and tongue) at the ages of 4-12 years.
At this age, the structures go through atrophy along with an increase in the size of the upper airways (1) . We did not perform   analysis regarding gender (Table 1) because the study was paired and, although the literature does not have reports on the association of gender with breathing mode (7,19) , a study showed higher prevalence of males with such clinical picture (24) . In the comparisons between nasal and mouth breathing modes, all medians obtained from the MB group using GM (Table 3) were lower than those from the NB group, which agrees with the literature (7) . Therefore, the GM was able to distinguish mouth-breathing patients from nasal-breathing patients according to gender, age group, weight, height and BMI. Median values provided by PNIF (Table 3), unlike the findings reported in the literature (10,11) , were not considered different in the division by gender.
As to the remaining variables, PNIF did not show differences between groups; the literature (12) , on the other hand, reports higher values for nasal-breathing patients. Thus, the GM was proven more effective to assess a possible nasal obstruction compared to PNIF in samples stratified by gender, age group, weight, height and BMI.
In analysis involving subgroups (Table 4), that is, Allergic MB, Surgical MB, allergic and Surgical MB, functional MB and NB, we verified that the GM was not able to distinguish patients with no breathing changes from those with a functional picture. It happens because the absence of obstruction makes the measure closer to that of a nasal-breathing patient; hence the instrument is not considered reliable to distinguish MB subgroup patients.
The GM can be used to identify the presence of obstruction, but not its cause. In a previous study (7) , the GM was not considered reliable to assess nasal patency, for it was only able to distinguish nasal-breathing cases from allergic-surgical cases. It is important to mention that the aforementioned study considered nasal-breathing patients who had been submitted to surgical treatments for obstruction and later on adopted the nasal-breathing mode.
At PNFI between MB subgroups (Table 4), difference was found only between surgical MB and NB; therefore, it may not be considered reliable to identify most patients with nasal obstruction. The results found were unexpected, because PNIF is usually considered more reliable than the GM (2) .
Mean values found by the GM in patients grouped according to breathing mode do not agree with a study (7) that reported lower values mainly for nasal-breathing patients. In our study, we took the classification of these studies' samples, which diverge.
In literature review, we found a study involving two groups of children aging 4 years to 4 years and 8 months where nasal airflow was measured using the GM. In the first group, submitted to removal of sucking habits, nasal aeration was increased from 10.70 to 18.10 and 18.40 cm². The second group, submitted to both removal of sucking habits and to myofuncional therapy, showed increase from 14.10 to 26.40 and 26.50 cm² (4) . Comparing these values with those of our study, considering the closest group age (4-6.6 years -6.87 cm 2 for mouth breathing and 13.24 cm 2 for nasal breathing), we found a divergence with data from the literature.
A study addressed the variation of nasal obstruction using the GM after maneuvers of massage and nasal cleansing in mouth-breathing children aging 4 to 11 years. An improvement in airflow was observed right after it, with measures of 16.6 cm 2 before and 20.3 cm 2 after (5) . These findings are not in concordance with ours, which reports 7.42 cm 2 for mouthbreathing patients and 16.96 cm 2 for nasal-breathing patients. Differences in the marks of the GM may explain the results.
As to PNIF, we were not able to make comparisons with data from the literature because the studies that used the instrument did not stratify the sample in groups according to the cause of alteration in breathing mode.
In a study conducted with 526 participants aged 8 to 15 years, the researchers presented a mathematic model to calculate the expiratory flow measured by PNIF as related to gender only (25) . Another study, with 212 children aging 6 to 11 years, reported that PNIF results were only influenced by age, the variables of gender, height, weight and ethnics being not decisive for values (26) .
Another published study brought reference values for healthy participants, but with an adult-only sample (27) . Overall, studies using PNIF describe the instrument as a simple, easy-tohandle, low-cost and fast tool that can provide important data for the management of patients with breathing disturbances, but there are divergences as to the normality pattern of results.
In our study, when assessing the correlation coefficient of measures by both tests (Table 5), we verified a low association in all situations, with no evidence of association between groupings. This finding cannot be compared with the literature, because the studies published did not compare nasal obstruction measures by PNIF with those by the GM.
The lack of studies with samples with subgroups divided by breathing mode also hinders comparison. However, we found a study (22) that compared active anterior rhinomanometry, acoustic rhinometry, and PNIF and found that any of these methods can be used to assess nasal obstruction. PNIF is emphasized because of its low cost, good reproducibility and short measurement time.
The same author conducted a study (16) where he compared the measures by PNIF with anterior rhinomanometry in allergic individuals and concluded that PNIF is reliable for diagnosis and therapeutic follow-up in the field of allergy. A study (6) compared the GM with nasopharyngoscopy and proved the validity of such correlation.
An editorial (28) addressing instruments used to measure nasal patency stated that the Glatzel and Gertner Mirrors, the peak nasal inspiratory or expiratory flow, and oscilometry are tests intended to assess nasal patency, which have been used to identify nasal obstruction.
Nevertheless, the most specific currently available tests are rhinomanometry and acoustic rhinometry. It's important to mention that the most reliable way of measuring nasal patency is by associating instruments. Moreover, anamnesis data plus clinical examination can be useful in providing information about participants' breathing mode (14,29) .
The lack of studies on GM, on the comparison between methods used in the present study, and between measures of mouth and nasal-breathing patients was a limitation for our work, as well as the small sample size, which did not allow data generalization.
Therefore, further studies are needed to increase the sample, in addition to the inclusion of a gold-standard exam such as Measurement of nasal patency. Speech therapists from SUS believe that it is important to use an instrument that is reliable and actually give evidence of obstruction while patients wait for the otolaryngologist's assessment.

COnClUSIOn
The GM was proven able to identify patients with and without nasal obstruction regardless of the cause; however it could not point this cause. PNIF, on the other hand, was shown to be able to distinguish only nasal-breathing patients from surgical mouth-breathing patients; so its applicability is more limited. The correlation of PNIF and the GM was found low in the studied sample.
*DLM and RVMS: data collection and analysis; TVCP: data analysis and writing; HMGB: data collection and study design; ARM: study project and design, general orientation for study conduction, and writing.