Within-Breath Analysis of Respiratory Mechanics in Asthmatic Patients by Forced Oscillation

Abstract

INTRODUCTION:The within-breath analysis of respiratory mechanics by the monofrequency Forced Oscillation Technique (mFOT) is of great interest in both physiopathology studies and the diagnosis of respiratory diseases. However, there are limited data on the use of this technique in the analysis of asthma. This study evaluates within-breath mechanics of asthmatic individuals and the contribution of the mFOT in the asthma diagnosis.METHODS:Twenty-two healthy and twenty-two asthmatic subjects, including patients with mild (n=8), moderate (n=8), and severe (n=6) obstruction, were studied. Forced Oscillation Technique data were interpreted using the mean respiratory impedance (Zt), the impedance during inspiration (Zi), expiration (Ze), at the beginning of inspiration (Zii), and at expiration (Zie). The peak-to-peak impedance (Zpp) was also calculated by the subtraction of Zii from Zie. Receiver operating characteristic curves were used to determine the sensitivity (Se) and specificity (Sp) of m Forced Oscillation Technique parameters in identifying asthma.RESULTS:Respiratory impedance values were significantly higher in asthmatics: Zt (p<0.001), Zi (p<0.001), Ze (p<0.001), Zii (p<0.001), Zie (p<0.001), and Zpp (p<0.003). The best parameters for detecting asthma were Zi, Zii, and Zie (Se=90.9%, Sp=90.9%), followed by Zt and Ze. These results are in close agreement with recently published theories and pathophysiological fundamentals.CONCLUSIONS:mFOT permits a non-invasive and detailed analysis in different phases of the respiratory cycle, providing parameters that are adequate for the diagnosis of asthma with high accuracy. These results confirm the high clinical and scientific potential of this methodology in the evaluation of asthmatic patients.

Total inspiratory and expiratory impedance in patients with severe chronic obstructive pulmonary disease

“…Under these conditions, Ze was the most suitable for correctly identifying the effects of COPD, with a sensitivity of 100% and a specificity of 90%. These promising results are consistent with those obtained previously21,44 and suggest that the Zrs observed in different phases of the respiratory cycle may be useful in the detection of COPD.…”

“…The resulting signals are recorded by an analog signal processing circuit to perform calculations to obtain the Zrs (Zrs = P/V´') in real time. This variable is known as the impedance module and describes the total mechanical load of the respiratory system, including the effects of resistance and reactance 11,21. The instrument was calibrated by means of a reference mechanical load and, after this, measurement errors were <0.5% 10,11.…”

Heart period sensitivity to forced oscillations in ventilatory pressure

“…The concomitant alteration in autonomic outXow may have implications on the normalcy of parameters of compliance, resistance, and inertance estimated using this method of pulmonary testing. While this pronounced eVect on the modulation of heart rate was observed using forced random ventilation, it is not known if the single sinusoidal method of estimating respiratory impedance has a similar eVect (DuBois et al 1956;Veiga et al 2009) or how the response may be dependent on the frequency of the sinusoid. To our knowledge, this profound eVect of forced oscillation on HRV has not been previously described.…”

Avaliação dos artigos de pneumologia publicados em periódicos Brasileiros além do Jornal Brasileiro de Pneumologia

“…(2) The presence of associated diseases, such as rhinitis (symptoms are present in 90% of cases), gastroesophageal Sleep 5 [16][17][18][19][20] Physiology, exercise, and rehabilitation 12 [21][22][23][24][25][26][27][28][29][30][31][32] COPD 8 [33][34][35][36][37][38][39][40] Pathology 3 [41][42][43] CT 2 [44][45] Occupational medicine 1 46 Pulmonary thromboembolism 2 [47][48] Pulmonary hypertension 3 [49][50][51] Lung cancer 3 [52][53][54] Smoking 2 [55][56] Evaluation of articles on pulmonology published in Brazilian In their study involving patients with severe OSAS, Neves et al found that the use of sildenafil worsens OSAS, as well as causing deleterious cardiovascular effects because of the increased parasympathetic tone and affecting the HR variability. (19) Pires et al, in a study of drivers engaged in night shift work, contradicted the notion that the sleep pattern of older individuals is more negatively affected than that of younger individuals.…”

“…Veiga et al used the forced oscillation technique in asthma patients, and this allowed the identification of increased respiratory impedance in such patients. (21) Using the forced oscillation technique, Tramont et al demonstrated that, with ageing, there is a reduction in the homogeneity of the respiratory system, especially in individuals over 70 years of age. (22) Measurement of PEF by five different meters was compared by Takara et al, who observed that there was no agreement among the devices.…”