Ventilatory muscles in healthy subjects: influence of gender, age, body position and exercise - a cross-sectional study

INTRODUÇÃO: Considerando que a literatura aponta para diferença de força relacionada ao gênero e ao envelhecimento, hipotetizamos que as mulheres e os idosos tivessem diferentes comportamentos da musculatura ventilatória ao repouso e ao exercício. Como há uma correlação entre a área de secção transversa dos músculos esqueléticos e a força muscular, e que esta é maior em homens, acreditamos que a espessura do diafragma ao ultrassom pudesse refletir as alterações de força relacionadas ao gênero. Por fim, como os músculos ventilatórios também estão envolvidos em outras funções, como a manutenção da postura, acreditamos que as mudanças de posição corpórea pudessem alterar o grau de sincronia entre os compartimentos (tórax e abdome) e a capacidade de geração de força da musculatura ventilatória. OBJETIVO PRIMÁRIO: Comparar o comportamento da musculatura ventilatória em indivíduos sadios categorizados por gênero e faixas etárias, ao repouso, em diferentes posições corpóreas e ao exercício. OBJETIVOS SECUNDÁRIOS: Caracterizar a mobilidade, a espessura e a capacidade de espessamento do diafragma ao ultrassom; Correlacionar a mobilidade, a espessura e a capacidade de espessamento do diafragma ao ultrassom com a força muscular ventilatória. MÉTODOS: Foi realizado um estudo transversal com 60 voluntários sadios de ambos os gêneros, divididos em três faixas etárias: 20-39, 40-59 e 60-80 anos. Os voluntários realizaram espirometria, medidas de PI e PEmáx e SNIP. Foram monitorizados com cateteres para medidas de pressão esofágica, gástrica e transdiagragmática.. Para avaliação de força não volitiva, realizamos estímulo magnético (Twitch) inspiratório e expiratório. Monitorizamos o escaleno, o esternocleidomastóideo, o intercostal paraesternal e o oblíquo externo com eletromiografia de superfície. Para avaliar a sincronia toracoabdominal utilizamos a pletismografia de indutância. Os voluntários eram monitorizados em diferentes posições e durante um teste de esforço cardiopulmonar. Após o teste de esforço, o Twitch era repetido para avaliação de fadiga. Por fim, em um subgrupo realizamos USG do diafragma para avaliar espessura e mobilidade. RESULTADOS: As mulheres apresentam menor força ao repouso e pior acoplamento neuromecanico ao exercício. No pico do exercício, elas têm menor contribuição diafragmática e utilizam um maior percentual da força abdominal máxima. Quanto à sincronia toracoabdominal e fadiga, as mulheres têm valores similares aos dos homens, porém estes valores são atingidos em cargas significativamente mais baixas. Embora mais fracos ao repouso, os idosos não tiveram pior acoplamento neuromecanico ao exercício. Quanto ao recrutamento muscular, sincronia toracoabdominal, trabalho ventilatório e fadiga, os idosos têm valores similares aos mais jovens, porém estes valores são atingidos em cargas significativamente mais baixas. Ao US, as mulheres têm mobilidade diafragmática na respiração profunda, espessura na CPT e fração de espessamento significativamente menores que os homens. A mobilidade do diafragma na respiração profunda, a espessura diafragmática na CPT e a fração de espessamento correlacionaram-se com a função pulmonar e a força muscular ventilatória em indivíduos sadios. A posição supino altera a sincronia entre os compartimentos (tórax e abdome) e a capacidade de geração de força da musculatura ventilatória. CONCLUSÕES:. O gênero, a idade, as mudanças de posição corpórea e o exercício têm influência sobre a musculatura ventilatória. Ao US, as mulheres têm mobilidade diafragmática na respiração profunda, espessura na CPT e fração de espessamento significativamente menores. A força muscular ventilatória tem correlação com as medidas do ultrassom em indivíduos sadiosINTRODUCTION: Since the literature points to lower ventilatory muscle strength in female and elderly, we hypothesized that in female and the elderly, ventilatory muscles behave differently at rest and during exercise. Considering that males are stronger, and that muscle strength correlates to muscular cross-sectional area, we interrogated ifthe thickness of the diaphragm evaluated by ultrasound could reflect the strength differences related to gender. Finally, as the ventilatory muscles are also involved in other functions, such as maintaining posture, we believe that different body positions could influence thoracoabdominal synchrony and the strength of the ventilatory muscles. PRIMARY OBJECTIVE: To compare the behavior of ventilatory muscles in healthy subjects categorized by gender and age range, at rest, in different body positions and during exercise. SECONDARY OBJECTIVES: To characterize mobility, thickness and thickness fraction of the diaphragm evaluated by ultrasound; Correlate mobility, thickness and thickness fraction with ventilatory muscle strength. METHODS: In a cross-sectional study, 60 healthy volunteers of both genders were divided into three age range groups: 20-39, 40-59 and 60-80 years. The volunteers performed spirometry, MIP, MEP and SNIP. They were monitored with balloon catheters for measurement of esophageal, gastric and transdiaphragmatic pressure. In order to evaluate non volitional inspiratory and expiratory strength, we performed magnetic stimulation (Twitch) of phrenic and 10th dorsal roots respectively. We monitored muscle recruitment of scalene, sternocleidomastoid, parasternal intercostal and external oblique with surface electromyography. To assess thoracoabdominal synchrony, we used respiratory inductance plethysmography. Volunteers were evaluated in different positions and during a cardiopulmonary exercise test. After the exercise test, the Twitch was repeated to assess fatigue. In a subgroup we performed ultrasound to evaluate the diaphragm thickness, thickening fraction and mobility. RESULTS: Women are weaker at rest and have worse neuromechanical coupling during exercise. In the end of exercise, women have lower diaphragmatic contribution and use a higher percentage of the maximum abdominal strength. Although women have values of thoracoabdominal synchrony and fatigue similar to those of men, women have completed the exercise at significantly lower workload. Although weaker at rest, the elderly had similar neuromechanical coupling to youngers during exercise. Regarding to ventilatory muscle recruitment, thoracoabdominal synchrony, work of breathing and fatigue, the elderly have similar values to younger group, but again, these values are achieved at significantly lower workloads. Concerning to ultrasound of diaphragm, women have significantly lower diaphragmatic mobility during deep breathing, thickness in the TLC and thickening fraction than men. The mobility of the diaphragm during deep breathing, the diaphragmatic thickness in TLC and the thickening fraction correlates to lung function and respiratory muscle strength. Supine position modifies thoracoabdominal synchrony and ventilatory muscle strength. CONCLUSIONS: Gender, age, body position and exercise influence the behavior of ventilatory muscles. Women have significantly lower diaphragmatic mobility during deep breathing, thickness in the TLC and thickening fraction. The ventilatory muscle strength correlates to ultrasound measurements in healthy subject

Diagnostic methods to assess inspiratory and expiratory muscle strength

Impairment of (inspiratory and expiratory) respiratory muscles is a common clinical finding, not only in patients with neuromuscular disease but also in patients with primary disease of the lung parenchyma or airways. Although such impairment is common, its recognition is usually delayed because its signs and symptoms are nonspecific and late. This delayed recognition, or even the lack thereof, occurs because the diagnostic tests used in the assessment of respiratory muscle strength are not widely known and available. There are various methods of assessing respiratory muscle strength during the inspiratory and expiratory phases. These methods are divided into two categories: volitional tests (which require patient understanding and cooperation); and non-volitional tests. Volitional tests, such as those that measure maximal inspiratory and expiratory pressures, are the most commonly used because they are readily available. Non-volitional tests depend on magnetic stimulation of the phrenic nerve accompanied by the measurement of inspiratory mouth pressure, inspiratory esophageal pressure, or inspiratory transdiaphragmatic pressure. Another method that has come to be widely used is ultrasound imaging of the diaphragm. We believe that pulmonologists involved in the care of patients with respiratory diseases should be familiar with the tests used in order to assess respiratory muscle function.Therefore, the aim of the present article is to describe the advantages, disadvantages, procedures, and clinical applicability of the main tests used in the assessment of respiratory muscle strength

Diagnostic methods to assess inspiratory and expiratory muscle strength

Impairment of (inspiratory and expiratory) respiratory muscles is a common clinical finding, not only in patients with neuromuscular disease but also in patients with primary disease of the lung parenchyma or airways. Although such impairment is common, its recognition is usually delayed because its signs and symptoms are nonspecific and late. This delayed recognition, or even the lack thereof, occurs because the diagnostic tests used in the assessment of respiratory muscle strength are not widely known and available. There are various methods of assessing respiratory muscle strength during the inspiratory and expiratory phases. These methods are divided into two categories: volitional tests (which require patient understanding and cooperation); and non-volitional tests. Volitional tests, such as those that measure maximal inspiratory and expiratory pressures, are the most commonly used because they are readily available. Non-volitional tests depend on magnetic stimulation of the phrenic nerve accompanied by the measurement of inspiratory mouth pressure, inspiratory esophageal pressure, or inspiratory transdiaphragmatic pressure. Another method that has come to be widely used is ultrasound imaging of the diaphragm. We believe that pulmonologists involved in the care of patients with respiratory diseases should be familiar with the tests used in order to assess respiratory muscle function.Therefore, the aim of the present article is to describe the advantages, disadvantages, procedures, and clinical applicability of the main tests used in the assessment of respiratory muscle strength