Print version ISSN 1413-3555
Rev. bras. fisioter. vol.14 no.5 São Carlos Sept./Oct. 2010
Verônica F. ParreiraI; Carolina J. BuenoII; Danielle C. FrançaIII; Danielle S. R. VieiraIII; Dirceu R. PereiraII; Raquel R. BrittoI
IPhysical Terapy Department, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte (MG), Brazil
IIPhysical Therapy course, UFMG
IIIGraduate Program in Rehabilitation Sciences, UFMG
OBJECTIVE: To describe the breathing pattern and thoracoabdominal motion of healthy individuals, taking age and sex into consideration.
METHODS: The study included 104 individuals aged 20 to 39, 40 to 59, and 60 to 80 years (41 males and 63 females), with normal body mass index and spirometric values. Participants were evaluated at rest in the supine position, by means of respiratory inductive plethysmography. The following variables were measured: tidal volume (Vt), respiratory frequency (f), minute ventilation (VE), inspiratory duty cycle (Ti/Ttot), mean inspiratory flow (Vt/Ti), rib cage motion (%RC), inspiratory phase relation (PhRIB), expiratory phase relation (PhREB), and phase angle (PhaseAng). Comparisons between the age groups were performed using one-way ANOVA or Kruskal-Wallis H, while comparisons between the sexes were performed using Student's t test or the Mann-Whitney U test, depending on the data distribution; p<0.05 was taken to be significant.
RESULTS: Comparison between the sexes showed that, in the age groups 20 to 39 and 60 to 80 years, women presented significantly lower values for Vt, VE, and Ti/Ttot than men, and there was no significant difference in the age group 40 to 59 years. Comparisons between the age groups showed that participants aged 60 to 80 presented significantly greater PhRIB and PhaseAng than participants aged 20 to 39 years, without significant differences in the breathing pattern.
CONCLUSION: The data suggest that breathing pattern is influenced by sex whereas thoracoabdominal motion is influenced by age.
Key words: respiratory physical therapy; assessment; breathing pattern; thoracoabdominal motion; healthy individuals.
The respiratory system consists primarily of the lungs, whose main function is to ensure gas exchanges with the environment, and the thoracic wall, which moves as a result of continual muscle action1. The thoracic wall represents the thoracoabdominal area composed of the rib cage and the abdomen, separated by the diaphragm2,3. Thus, normal thoracoabdominal motion consists of expansion and retraction of these compartments during inspiration and expiration, respectively4,5. Although the rib cage and abdomen move in unison, each of the compartments has independence of movement6. When the displacement between the compartments ceases to be harmonious, the thoracoabdominal motion becomes asynchronous4,5,7. Healthy men and women in different age groups present symmetry between the movements on the right and left sides of the chest and abdomen8.
Breathing pattern and thoracoabdominal motion may be influenced by several factors, such as the individual's positioning9,10, age10,11, sex10, respiratory overload12 , neuromuscular diseases13, lung diseases associated with increased airway resistance4,14,15, and chronic obstructive pulmonary disease (COPD)5,16-18. Higher rates of asynchrony may be related to worse prognosis and significantly greater mortality16.
Among the factors that may influence the respiratory system in healthy individuals, age and sex can be highlighted. In the elderly, the structural changes to the respiratory system encompass modifications that occur in the lungs, rib cage, respiratory muscles, and respiratory drive. The main change relating to the rib cage is its reduction in compliance. Among healthy individuals, these changes are more evident after the age of 80, although they are present from the age of 50 onwards11. Studies using plethysmography have demonstrated that the mean values of the components of the breathing pattern of healthy elderly individuals do not differ significantly from what is found among non-elderly adults7,10,11. This suggests that, in the populations studied, the process of aging of the respiratory system did not cause a great impact on the parameters analyzed.
In relation to sex, a study that made comparisons between men and women showed that there were differences in respiratory times3. The inspiratory time, expiratory time, and total time of the respiratory cycle were shorter among the women. In addition, the women presented higher respiratory frequency, thus suggesting that they tended to breathe more rapidly than the men3. In the analysis of thoracoabdominal motion during quiet breathing, men and women presented the same response3,10.
Data on breathing pattern and thoracoabdominal asynchrony are important sources of information on respiratory function10,11,14,19 and represent an important tool in physical therapy evaluations of patients with acute and chronic respiratory dysfunctions. Its importance starts in primary healthcare as the patient enters the public healthcare system and goes up to high-complexity environments such as intensive care units. Data relating to breathing pattern, e.g. tidal volume and respiratory frequency, are useful for follow-ups within different types of respiratory physical therapy interventions. Examples would include pulmonary rehabilitation and patient care before and after chest and abdominal surgery, among other clinical situations, thus making it possible to observe whether different parameters have evolved favorably or not. One instrument frequently used in studies evaluating breathing pattern and thoracoabdominal motion is the inductive plethysmography, which measures displacement of thoracoabdominal compartments and changes in time and pulmonary volume3,7,10.
To the best of our knowledge, studies on breathing pattern and thoracoabdominal motion among healthy adults have either evaluated few individuals3, very different numbers of individuals in different age groups7, or a limited number of variables10. Given the importance of evaluating breathing pattern and thoracoabdominal motion for clinical practice, it would be of interest to obtain data on different variables from a significant number of Brazilian individuals. Within this context, the aim of this study was to describe the breathing pattern and thoracoabdominal motion of healthy Brazilian individuals according to sex and age.
For this study, 109 participants were recruited. Data were gathered at the Laboratório de Avaliação e Pesquisa em Desempenho Cardiorrespiratório. The inclusion criteria were: age between 20 and 80 years; body mass index (BMI) without indication of excess weight (18.5 and 29.9 kg/m2 )20; non-smoker; absence of ventilatory disorders of any kind in pulmonary function tests, in accordance with the values predicted by Pereira21; absence of evident chest or abdominal deformity; absence of cardiac or neuromuscular diseases; and absence of previous chest or abdominal surgery. The exclusion criterion was inability to understand and/or undergo any of the procedures. The study was approved by the Research Ethics Committee of Universidade Federal de Minas Gerais (UFMG), Belo Horizonte (MG), Brazil (Approval ETIC 148/07), and all participants signed an informed consent form.
Procedures and measurement instruments
After the participants had read and signed the consent form, their weight and height were measured using a calibrated scale (Filizola Ind. Ltda, São Paulo, SP, Brazil) to calculate the BMI, and the pulmonary function test was performed by means of a forced maneuver, using spirometry (Vitalograph 2120, Buckingham, England). To evaluate the breathing pattern and thoracoabdominal motion, respiratory inductive plethysmography was used (Respitrace®, Nims, Miami, FL, USA). This is a noninvasive method that requires little exertion by the participant; it has been shown to be accurate22-24 and has been used in previous studies3,5,7,10-12,14-17,25-32 . Respiratory inductive plethysmography measurements are based on changes to the cross-sectional area detected by two inductance bands. Each band is composed of two thin, adhered elastic bands around a plastic-coated transducer wire that is arranged in a sinusoidal pattern. One of the strips was positioned on the axilla and the other, on the umbilical line. The bands were given a slight stretch to fit tightly around the participant and minimize signal distortion, but without limiting chest movement or causing discomfort.
The participant was positioned in supine and asked to remain comfortably in this position while breathing quietly without raising the head (0º), speaking, sleeping, or moving any of the body segments until the data recording had finished. The signal was calibrated during spontaneous breathing, by means of a specific procedure (Qualitative Diagnostic Calibration) that was first described by Sackner et al.34. This procedure was carried out in two stages. Firstly, the participant breathed spontaneously to balance the electrical gain of the signals relating to the rib cage and abdomen. When correctly amplified and divided, these signals allow relative calibration, which lasts about five minutes. Next, after using a syringe of known volume, the participant breathed through a spirometer (Vitatrace, Pro Médico, Rio de Janeiro, RJ, Brazil) for 30 to 60 seconds using a nose clip. During this stage, the electrical signals from the rib cage and abdomen were used to obtain the tidal volume in ml.
The calibration was performed by means of a software program (RespiPanel, NIMS, Miami, FL, USA). A detailed description of the calibration has been published previously28,35. After the calibration, the plethysmographic data were recorded for around 10 minutes by means of specific software (RespiEvents 5.2, NIMS, Miami, FL, USA). To analyze the data, intervals of at least 30 seconds of stable tracing were selected. In addition, the sum of these intervals had to reach a minimum of five minutes of recording.
For the breathing pattern, the following volume and time variables were analyzed11: tidal volume (Vt); respiratory frequency (f); minute ventilation (VE); inspiratory duty cycle (Ti/Ttot); and mean inspiratory flow (Vt/Ti). In relation to thoracoabdominal motion, the following were analyzed: rib cage motion (%RC); phase angle (PhaseAng), which reflected the delay between rib cage and abdomen excursions4,5,12,14,15,27,29,30; inspiratory phase relation (PhRIB) and expiratory phase relation (PhREB), which reflected the percentage of time during one breath in which the rib cage and abdomen moved in opposite directions, respectively29,30.
The data were presented as central tendency and dispersion. To analyze the data, the individuals were divided into three groups according to age: 20 to 39 years, 40 to 59 years, and 60 to 80 years. For the comparisons between the sexes, the age groups were divided into women and men.
The normality of the data was checked by means of the Shapiro-Wilk test. The comparisons between the sexes were made using Student's t test for independent samples or the Mann-Whitney U test, depending on the data distribution. The comparisons between the age groups were made using one-way ANOVA or Kruskal-Wallis H, according to the data distribution. The significance level was set at p<0.05. The analyses were performed using the Statistical Package for the Social Sciences, version 13.0.
Of the 109 participants, five were excluded due to technical problems during the data collection. Thus, the data relate to 104 participants (48 between 20 and 39 years of age; 18 between 40 and 59, and 38 between 60 and 80 years). In all, 8667 respiratory cycles were analyzed, with a mean of 84 cycles per participant. Table 1 describes the anthropometric, demographic, and spirometric characteristics of the sample.
Table 2 presents the values of the breathing pattern and thoracoabdominal motion variables among the men and women in the three age groups. Comparisons between the sexes were made in each age group, and these showed that Vt, VE, and Ti/Ttot were significantly lower among the women in the age group 20 to 39, but without any significant differences in the other variables. There were no significant differences in the age group 40 to 59. Among the women in the elderly group, Vt, VE, and Vt/Ti were significantly lower, but without significant differences in the other variables.
Table 3 presents comparisons of breathing pattern and thoracoabdominal motion between the age groups. No significant differences were observed in any of the variables relating to the breathing pattern. In relation to thoracoabdominal motion, PhRIB and PhaseAng were significantly greater in individuals over the age of 60 than in adults between 20 and 39 years.
In addition, comparisons between the age groups were made for the men and women separately. No significant differences between the age groups were found among the women. Among the men, there was only a significant difference in the variable Ti/Ttot. Men aged 20 to 39 presented significantly lower values than did the men over 60 years.
The main result from this study was that there were significant differences in some of the breathing pattern variables between the sexes and in the thoracoabdominal motion variables between the participants in the three age groups evaluated. Comparison between the sexes showed that women presented significantly lower values than men for the variables Vt, VE, and Ti/Tot in the age group between 20 and 39 years and for the variables Vt, VE, and Vt/Ti in the elderly group, but without significant differences in the variables related to thoracoabdominal motion. Comparison between the age groups showed that the participants over the age of 60 presented significantly greater PhRIB and PhaseAng, in relation to the participants aged 20 to 39, but without significant differences in the breathing pattern variables.
To the best of our knowledge, previous studies that evaluated breathing pattern and thoracoabdominal motion variables among healthy adults were conducted among populations in other countries and/or using limited numbers of variables or individuals3,7,10. The present study adds important information, considering that the values observed among individuals in different age groups can be used both in the evaluation process and physical therapy treatment of patients with acute or chronic respiratory dysfunctions. The participants were recruited as a convenience sample from residents of the city of Belo Horizonte, Minas Gerais, Brazil, which may be considered to be a limitation of this study. Nonetheless, the number of participants analyzed is similar to the numbers in other studies related to respiratory function parameters that have put forward reference values36,37.
Regarding the measurement instrument used, it should be emphasized that respiratory inductive plethysmography is an appropriate method for evaluating breathing pattern and thoracoabdominal motion, as proposed in the present study. It is also worth noting that there is a new method for obtaining information that gives greater detail about the operational volumes of the thoracic wall. The main innovation of this method is that it provides greater accuracy of analysis during exercise, given that it can produce a three-dimensional analysis that takes into consideration three compartments of the thoracic wall (pulmonary rib cage, abdominal rib cage, and abdomen), thus differing from the respiratory inductive plethysmography that analyzes two compartments. This point is particularly important in the presence of dynamic hyperinflation38,39. It is unlikely that there was any hyperinflation among the participants in the present study, given that the evaluation was performed on healthy individuals at rest.
Regarding comparisons between the sexes, significant differences in the breathing pattern variables were observed. In relation to the men, the women in the age group 20 to 39 presented significantly lower Vt, VE, and Ti/Ttot. To the best of our knowledge, only one other study made a comparison of breathing patterns between men and women, in which individuals aged between 20 and 45 years were evaluated3. Our data corroborate what was observed previously in relation to Vt, which was significantly lower among females. This result can be attributed to the difference in physical constitution between men and women. However, this difference was insufficient to significantly influence VE, which did not present any difference between women and men in these two studies. Regarding the time components of the breathing pattern, Feltrim3 found a lower inspiratory time in the female group. This result may help to explain the significantly lower Ti/Ttot among the women in the present study. In the elderly group, the significant differences observed in Vt and VE were similar to those observed among adults aged 20 to 39, and the difference in Vt/Ti seemed to result from the change in Vt, given that no change in Ti/Ttot was observed. In relation to participants aged 40 to 59, no significant difference was observed.
In relation to the comparison between the sexes, the only difference was in the Ti/Ttot among the men over 60 years, compared with those aged 20 to 39. Despite the difference observed, the values were within the normal range7. Verschakelen and Demedts10 evaluated the influence of sex on individuals in this age group, but only in relation to the variables of thoracoabdominal motion.
Comparison of the variables relating to thoracoabdominal motion between the sexes in the present study did not show any significant difference between men and women. This result corroborates the findings in the literature. The influence of sex on thoracoabdominal motion was previously evaluated in two studies3,10, none of which found any significant difference in the percentage displacement of the chest and abdominal compartments between men and women in the supine position at rest. Thus, it seems to be well established that displacement of the abdominal compartment is proportionally greater in both men and women in the supine position.
Regarding thoracoabdominal asynchrony, no significant differences were found between men and women. To the best of our knowledge, the influence of sex on thoracoabdominal asynchrony has not been evaluated in any studies. The values observed in the present study are close to those described in the literature for healthy individuals at rest26.
Comparison between the three age groups did not show any significant differences in the breathing pattern variables. These results are in agreement with other studies that compared breathing pattern variables between healthy adults and elderly individuals. No significant differences were observed in the parameters analyzed at rest in these studies7,11. Recently, Britto et al.40 evaluated two groups of elderly people, one aged 60 to 69 and one over 69 years, also without significant differences in the respiratory pattern.
In relation to thoracoabdominal motion in the present study, the elderly participants presented significantly greater PhRIB and PhaseAng than the participants aged 20 to 39. The presence of greater thoracoabdominal asynchrony observed among the elderly participants may have been due to structural modifications to the rib cage, weakness of the respiratory muscles, and changes to the respiratory drive41, given that these factors may increase respiratory overload25. The influence of age on thoracoabdominal asynchrony was previously evaluated among 18 elderly individuals7. This study evaluated the ratio of maximum compartmental amplitude to Vt, which is a parameter measuring thoracoabdominal asynchrony, and did not observe any significant difference. It is possible that the limited number of individuals may have influenced the results.
In conclusion, the present study made it possible to describe values for variables relating to breathing pattern and thoracoabdominal motion in men and women of different age groups. The data found in this study suggest that the breathing pattern is influenced by sex whereas the thoracoabdominal motion is influenced by age.
Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).
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Correspondence to: Received: 29/05/2009 – Revised: 20/10/2009 – Accepted: 26/01/2010
Verônica Franco Parreira
Departamento de Fisioterapia, Escola de Educação Física, Fisioterapia e Terapia Ocupacional, Universidade Federal de Minas Gerais (UFMG)
Av. Presidente Antônio Carlos, 6627, Campus Pampulha
CEP 31.270-901, Belo Horizonte (MG), Brazil
Received: 29/05/2009 – Revised: 20/10/2009 – Accepted: 26/01/2010