Avaliação de mecânica ventilatória por oscilações forçadas: fundamentos e aplicações clínicas

Abstract

Requerendo apenas cooperação passiva e fornecendo novos parâmetros para análise da mecânica ventilatória, a técnica de oscilações forçadas (TOF) apresenta características complementares aos métodos clássicos de avaliação pulmonar. Neste trabalho, inicialmente é apresentada uma revisão dos princípios da técnica juntamente com uma discussão sobre suas vantagens e atuais limitações. A performance da técnica é comparada com a dos métodos clássicos na detecção de afecções respiratórias. As principais aplicações clínicas reportadas anteriormente na literatura, incluindo a avaliação da mecânica ventilatória infantil, estudos em neonatos, monitorização de pacientes sob ventilação mecânica, medicina ocupacional e avaliação de distúrbios no sono, são revisadas e discutidas. Com base na revisão efetuada e nos resultados obtidos em estudos efetuados em laboratório, os autores concluem que a TOF pode contribuir para um exame mais detalhado, assim como para facilitar a realização de testes de função pulmonar em condições nas quais as técnicas tradicionais não são adequadas.

Efeito da obstrução de vias aéreas nas variações das propriedades resistivas e elásticas do sistema respiratório de asmáticos, mediadas pelo uso de salbutamol

“…It is of note that, in such studies, subject height should be homogeneous, since it is the parameter that has the most influence on impedance values. (2,3,20) In the control group, bronchodilator use resulted in a small and homogeneous reduction in the Rrs values between 4 and 32 Hz (0.40 ± 0.04 cmH 2 O•L −1 •s; Figure 1a and Table 2), which corroborates the findings of another study. (21) However, in the severe obstruction with BR+ subgroup, bronchodilator use resulted in a greater reduction in total resistance (MDRrs = 0.87 ± 0.65 cmH 2 O •L −1 •s).…”

“…Using linear regression of the Rrs curve, carried out in the 4-16 Hz frequency range, we obtained the resistance at the intercept (R 0 ). (2,10,17) Based on the Xrs curve, the dynamic compliance (Cdyn) of the respiratory system at the 4-Hz frequency was calculated as follows (17,19) : Cdyn = −2ω × f × Xrs, 4 Hz The analysis of R 0 and Cdyn was performed using the values for the variation between prebronchodilator and postbronchodilator measurements in the different groups (control, mild, moderate and severe) and subgroups (BR+ and BR−).…”

“…The FOT requires only passive cooperation, is performed during spontaneous breathing and provides new parameters for analysis. (2)(3)(4) Although the potential for use of the FOT in the study of the pathophysiology of bronchodilator response in asthma patients is high, relatively few studies have investigated that potential. (5)(6)(7)(8)(9) Such studies have demonstrated that the parameters obtained using the FOT allow adequate identification of reduced muscle tone and, consequently, of reduced airway resistance as a result of bronchodilator testing in adult patients with asthma.…”

Correlação dos achados tomográficos com parâmetros de função pulmonar na fibrose pulmonar idiopática em não fumantes

“…It is known that volume reduction decreases both pulmonary compliance and the compliance of the chest wall, which can explain, at least in part, the results obtained. (13) Since its measurement is noninvasive, the potential for use of Crs,dyn in the evaluation of these patients is high. In addition, to our knowledge, there are no studies in the literature correlating Crs,dyn with HRCT findings in IPF.…”

“…The FOT was performed using an impedance analyzer, and the following parameters were evaluated: resistance at the intercept (R0), slope of resistance (S), mean resistance (mR) and dynamic respiratory compliance (Crs,dyn). (13) The remaining tests were carried out using the Collins Plus Pulmonary Function Testing Systems (Warren E. Collins, Inc., Braintree, MA, USA) and followed the standardization and interpretation of the Brazilian Thoracic Society. (14) Equations devised by Pereira (spirometry) and Neder (static lung volumes and diffusion) were used in the interpretation of the following parameters (15)(16)(17) HRCT: GE equipment, HISPEED model; 1-mm thick slices, at 1.5 s intervals and increased by 10 mm; image reconstruction with a 512 × 512 pixel matrix, using a high resolution algorithm; 1000 HU width window; −700 HU medium window level.…”