Respiratory oscillometry and functional analyses in patients with idiopathic scoliosis.

Scoliosis is a condition that affects the spine and causes chest rotation and trunk distortion. Individuals with severe deformities may experience dyspnea on exertion and develop respiratory failure. Respiratory oscillometry is a simple and non-invasive method that provides detailed information on lung mechanics. This work aims to investigate the potential of oscillometry in the evaluation of respiratory mechanics in patients with scoliosis and its association with physical performance. We analyzed 32 volunteers in the control group and 32 in the scoliosis group. The volunteers underwent traditional pulmonary function tests, oscillometry, and the 6-minute walk test (6MWT). Oscillometric analysis showed increased values of resistance at 4 Hz (R4, P<0.01), 12 Hz (R12, P<0.0001), and 20 Hz (R20, P<0.01). Similar analysis showed reductions in dynamic compliance (Cdyn, P<0.001) and ventilation homogeneity, as evaluated by resonance frequency (fr, P<0.001) and reactance area (Ax, P<0.001). Respiratory work, described by the impedance modulus, also showed increased values (Z4, P<0.01). Functional capacity was reduced in the group with scoliosis (P<0.001). A significant direct correlation was found between Cobb angle and R12, AX, and Z4 (P=0.0237, P=0.0338, and P=0.0147, respectively), and an inverse correlation was found between Cdyn and Cobb angle (P=0.0190). These results provided new information on respiratory mechanics in scoliosis and are consistent with the involved pathophysiology, suggesting that oscillometry may improve lung function tests for patients with scoliosis.

Respiratory oscillometry and functional analyses in patients with idiopathic scoliosis

Scoliosis is a condition that affects the spine and causes chest rotation and trunk distortion. Individuals with severe deformities may experience dyspnea on exertion and develop respiratory failure. Respiratory oscillometry is a simple and non-invasive method that provides detailed information on lung mechanics. This work aims to investigate the potential of oscillometry in the evaluation of respiratory mechanics in patients with scoliosis and its association with physical performance. We analyzed 32 volunteers in the control group and 32 in the scoliosis group. The volunteers underwent traditional pulmonary function tests, oscillometry, and the 6-minute walk test (6MWT). Oscillometric analysis showed increased values of resistance at 4 Hz (R4, P<0.01), 12 Hz (R12, P<0.0001), and 20 Hz (R20, P<0.01). Similar analysis showed reductions in dynamic compliance (Cdyn, P<0.001) and ventilation homogeneity, as evaluated by resonance frequency (fr, P<0.001) and reactance area (Ax, P<0.001). Respiratory work, described by the impedance modulus, also showed increased values (Z4, P<0.01). Functional capacity was reduced in the group with scoliosis (P<0.001). A significant direct correlation was found between Cobb angle and R12, AX, and Z4 (P=0.0237, P=0.0338, and P=0.0147, respectively), and an inverse correlation was found between Cdyn and Cobb angle (P=0.0190). These results provided new information on respiratory mechanics in scoliosis and are consistent with the involved pathophysiology, suggesting that oscillometry may improve lung function tests for patients with scoliosis.

Correlations between forced oscillation technique parameters and pulmonary densitovolumetry values in patients with acromegaly.

The aims of this study were to evaluate the forced oscillation technique (FOT) and pulmonary densitovolumetry in acromegalic patients and to examine the correlations between these findings. In this cross-sectional study, 29 non-smoking acromegalic patients and 17 paired controls were subjected to the FOT and quantification of lung volume using multidetector computed tomography (Q-MDCT). Compared with the controls, the acromegalic patients had a higher value for resonance frequency [15.3 (10.9-19.7) vs 11.4 (9.05-17.6) Hz, P=0.023] and a lower value for mean reactance [0.32 (0.21-0.64) vs 0.49 (0.34-0.96) cm H2O/L/s2, P=0.005]. In inspiratory Q-MDCT, the acromegalic patients had higher percentages of total lung volume (TLV) for nonaerated and poorly aerated areas [0.42% (0.30-0.51%) vs 0.25% (0.20-0.32%), P=0.039 and 3.25% (2.48-3.46%) vs 1.70% (1.45-2.15%), P=0.001, respectively]. Furthermore, the acromegalic patients had higher values for total lung mass in both inspiratory and expiratory Q-MDCT [821 (635-923) vs 696 (599-769) g, P=0.021 and 844 (650-945) vs 637 (536-736) g, P=0.009, respectively]. In inspiratory Q-MDCT, TLV showed significant correlations with all FOT parameters. The TLV of hyperaerated areas showed significant correlations with intercept resistance (rs=-0.602, P<0.001) and mean resistance (rs=-0.580, P<0.001). These data showed that acromegalic patients have increased amounts of lung tissue as well as nonaerated and poorly aerated areas. Functionally, there was a loss of homogeneity of the respiratory system. Moreover, there were correlations between the structural and functional findings of the respiratory system, consistent with the pathophysiology of the disease.

Correlations between forced oscillation technique parameters and pulmonary densitovolumetry values in patients with acromegaly

The aims of this study were to evaluate the forced oscillation technique (FOT) and pulmonary densitovolumetry in acromegalic patients and to examine the correlations between these findings. In this cross-sectional study, 29 non-smoking acromegalic patients and 17 paired controls were subjected to the FOT and quantification of lung volume using multidetector computed tomography (Q-MDCT). Compared with the controls, the acromegalic patients had a higher value for resonance frequency [15.3 (10.9-19.7) vs 11.4 (9.05-17.6) Hz, P=0.023] and a lower value for mean reactance [0.32 (0.21-0.64) vs 0.49 (0.34-0.96) cm H2O/L/s2, P=0.005]. In inspiratory Q-MDCT, the acromegalic patients had higher percentages of total lung volume (TLV) for nonaerated and poorly aerated areas [0.42% (0.30-0.51%) vs 0.25% (0.20-0.32%), P=0.039 and 3.25% (2.48-3.46%) vs 1.70% (1.45-2.15%), P=0.001, respectively]. Furthermore, the acromegalic patients had higher values for total lung mass in both inspiratory and expiratory Q-MDCT [821 (635-923) vs 696 (599-769) g, P=0.021 and 844 (650-945) vs 637 (536-736) g, P=0.009, respectively]. In inspiratory Q-MDCT, TLV showed significant correlations with all FOT parameters. The TLV of hyperaerated areas showed significant correlations with intercept resistance (rs=−0.602, P<0.001) and mean resistance (rs=−0.580, P<0.001). These data showed that acromegalic patients have increased amounts of lung tissue as well as nonaerated and poorly aerated areas. Functionally, there was a loss of homogeneity of the respiratory system. Moreover, there were correlations between the structural and functional findings of the respiratory system, consistent with the pathophysiology of the disease.

Relationships between the pulmonary densitometry values obtained by CT and the forced oscillation technique parameters in patients with silicosis.

OBJECTIVE: To evaluate the correlations between pulmonary densitometry values and forced oscillation technique (FOT) parameters in patients with silicosis. METHODS: This cross-sectional study comprised 36 non-smoker patients with silicosis and 20 matched control subjects who were submitted to FOT and multidetector CT (MDCT). RESULTS: Compared with the control subjects, the MDCT evaluation demonstrated that patients with silicosis exhibited greater total lung mass. These patients also had larger non-aerated and poorly aerated compartments, which included nodules and scarring. Compared with the control subjects, FOT evaluation demonstrated that patients with silicosis exhibited changes in both reactive and resistive properties of the respiratory system. In these patients, there was a greater heterogeneity of the respiratory system and increased work of breathing. Significant correlations between non-aerated compartment size and FOT parameters that reflect the non-homogeneity of the respiratory system were observed. The dynamic compliance of the respiratory system was negatively correlated with non-aerated compartment size, while the impedance at 4 Hz was positively correlated with non-aerated compartment size. CONCLUSION: Patients with silicosis have heavier lungs. In these patients, a larger non-aerated compartment is associated with a worsening of lung function. A more significant pulmonary involvement is associated with a loss of homogeneity and increased mechanical load of the respiratory system. Advances in knowledge The findings provided by both pulmonary densitometry and FOT may add valuable information to the subjective analysis of silicosis; however, more studies are necessary to evaluate the potential use of these methods for assessing disease progression.

Technical developments of functional electrical stimulation to correct drop foot: sensing, actuation and control strategies.

This work presents a review on the technological advancements over the last decades of functional electrical stimulation based neuroprostheses to correct drop foot. Functional electrical stimulation is a technique that has been put into practice for several years now, and has been shown to functionally restore and rehabilitate individuals with movement disorders, such as stroke, multiple sclerosis and traumatic brain injury, among others. The purpose of this technical review is to bring together information from a variety of sources and shed light on the field's most important challenges, to help in identifying new research directions. The review covers the main causes of drop foot and its associated gait implications, along with several functional electrical stimulation-based neuroprostheses used to correct it, developed within academia and currently available in the market. These systems are thoroughly analyzed and discussed with particular emphasis on actuation, sensing and control of open- and closed-loop architectures. In the last part of this work, recommendations on future research directions are suggested.

Fluctuation analysis of respiratory impedance waveform in asthmatic patients: effect of airway obstruction.

Fluctuation analysis has great potential to contribute to pulmonary clinical science and practice. We evaluated the relationship between asthma and the respiratory impedance recurrence period density entropy (RPDEnZrs) and the variability (SDZrs). A non-invasive and simple protocol for assessing respiratory mechanics during spontaneous breathing was used in a group of 74 subjects with various levels of airway obstruction. Airway obstruction resulted in a reduction in the RPDEnZrs that was significantly correlated with both spirometric indices of airway obstruction (R = 0.48, p < 0.0001) and mean respiratory impedance (R = -0.83, p < 0.0001). These results suggest that the impedance pattern becomes less complex in asthmatic patients, which may explain the reduction in respiratory systems' adaptability to daily life activities. Preliminary evaluations indicate that RPDEnZrs may contribute to the asthma diagnosis, presenting accuracies of 82 and 87 % in patients with moderate and severe airway obstruction, respectively. On the other hand, SDZrs increased with obstruction (p < 0.0001) and was inversely correlated with spirometric indices of obstruction (R = -0.42, p = 0.0003) and directly associated with mean impedance (R = 0.88, p < 0.0001). This analysis contributes to elucidate previous studies and identified respiratory changes in patients with moderate and severe obstruction with an adequate accuracy (85 and 87 %, respectively).

Diagnostic performance of the Forced Oscillation Technique in the detection of early respiratory changes in rheumatoid arthritis.

The objective of this study was to evaluate the clinical potential of the Forced Oscillation Technique (FOT) in the detection of the early alterations in respiratory mechanics of Rheumatoid Arthritis (RA) patients. A total of 36 individuals were analyzed, 18 healthy and 18 with RA. The clinical usefulness of the parameters was evaluated investigating sensibility (Se), specificity (Sp) and the area under the receiver operating characteristic curve (AUC). In the RA group, all the 3 studied parameters obtained high accuracy for clinical use (AUC>0.9), while in spirometric parameters, no parameter obtained appropriate accuracy for clinical use (AUC < 0.7). In conclusion, the parameters obtained by FOT presented adequate Se and Sp, indicating that this technique can be helpful in the evaluation of the early respiratory mechanical alterations in patients with RA.

Mechanical analysis of an oscillatory positive expiratory pressure device used in respiratory rehabilitation.

This article aims to characterize the mechanical behavior of the Acapella Blue, a respiratory rehabilitation device designed to aid sputum clearance. In this scope, the present study initially describes in detail the peak-to-peak oscillation amplitude (App) and peak frequency (fp) behavior, as well as positive pressure level (Ppl), in the flow range more comonly found in practice. The parameters were evaluated in all 5 adjustment levels of the equipment in intervals of 50 mL/s. The device characterization has shown fp up to 23 Hz, App from 0.2 to 2.8 cmH(2)O and Ppl ranging from 1.2 to 13.5 cmH(2)O. The studied device may produce oscillation in the ranges of ciliary movements and respiratory system resonance frequency of patients with respiratory diseases. Data obtained in this work may help to optimize the use of the Acapella Blue device in respiratory rehabilitation. Suggestions for the practical use of the device are also presented.

Validation of the Forced Oscillation Technique in the diagnostic of respiratory changes in patients with silicosis.

Silicosis is a typical occupational respiratory disease characterized by irreversible alterations throughout the alveolar and interstitial structure. The objectives of this study were (1) investigate the potential of the Forced Oscillation Technique (FOT) in the analysis of the patients with silicosis, and (2) evaluate the ability of FOT to identify early alterations in the respiratory mechanics of these patients. Sixty-one volunteers were analyzed: 20 healthy subjects and 41 with silicosis; these, were divided into 4 groups according to spirometric results: normal spirometric exam (n = 11); mild obstruction (n = 20); moderate and severe obstruction (n = 10.). A significant (p〈0.0001) increase in total resistance (R0) and mean resistance (Rm) were observed, as well as a decrease in the dynamic compliance (p〈0.0003) and mean reactance (p〈0.000004). R0 and Rm obtained adequate accuracy for clinical use (>80%). FOT parameters adequately described the pathophysiological changes associated with silicosis and presented adequate accuracy for clinical use, indicating that this technique can be helpful in the evaluation respiratory mechanics in this disease.

Efeito da obesidade sobre as propriedades resistivas e reativas do sistema respiratório / Effect of obesity on the resistive and reactive properties of the respiratory system

A fim de avaliar uma possível relação entre a obesidade e as modificações nas propriedades resistivas e reativas do sistema respiratório e do potencial de oscilações forçadas no estudo da obesidade, mecânica oscilações foram avaliados em 25 saudáveis e 25 indivíduos obesos...

Efeito do envelhecimento sobre as propriedades resistivas e reativas do sistema respiratório / Effect of aging on the resistive and reactive properties of the respiratory system

Os sintomas respiratórios em idosos podem ser confundidos com modificações fisiológicas que introduz erros no processo de diagnóstico. Esta obra tem como objetivo investigar as modificações nas propriedades resistivas e reativas do sistema respiratório com o aumento da idade da técnica de oscilações forçadas...

Simplified oscillation method for assessing nasal obstruction non-invasively and under spontaneous ventilation: a pilot study.

The clinical application of the current methods of measuring nasal obstruction has been limited by complicated, invasive and stressful procedures that require the full co-operation of the patient. A pilot study is described where a simple way of evaluating nasal obstruction, based on oscillation methods, was investigated. The technique did not disturb spontaneous breathing and required little co-operation and comprehension. Significant differences were obtained when clinically classified normal (5.2 +/- 1.8 cmH2O l(-1) s) and patient (10.6 +/- 5.9 cmH2O l(-1) s) groups were evaluated (p<0.01). A significant reduction (p<0.02) was also observed in impedance results before (8.5 +/- 1.1 cmH2O l(-1) s) and after (5.2 +/- 1.7 cmH2O l(-1) s) clinically successful nasal surgery, closely reflecting the clinical conditions of the subjects. This simple forced oscillation technique showed good potential for future clinical applications in the pre-screening of nasal patients and the evaluation of therapeutic surgery.

Effect of generator nonlinearities on the accuracy of respiratory impedance measurements by forced oscillation.

Measurements of respiratory impedance by means of the forced oscillation technique (FOT) are usually made using a loudspeaker as the excitation device. Its nonlinear nature can introduce artifacts that coincide with the frequencies applied to excite the respiratory system, limiting the accuracy of the impedance estimation. In this paper, this hypothesis is evaluated in the case of both a traditional estimator and the unbiased estimator proposed by Daróczy and Hantos (1982). A simulated study under apnoea conditions in the pressure range 0.5-3.0 cmH2O peak-to-peak reveals that loudspeaker nonlinearities introduce a characteristic pattern of dispersion in both the resistance and reactance curves that can be significantly decreased (p approximately equal to 0.03, signtest) by reducing the nonlinearities. A simulation of spontaneous breathing shows the same pattern, and is observed in the case of traditional as well as unbiased estimators. The dispersion is quantified by the mean absolute distance between the theoretical and simulated data and decreases with the reduction of nonlinearities when impedance is estimated with a traditional estimator (from 6.63 to 4.72% in real estimates and from 6.78 to 3.47% in imaginary estimates) as well as with an unbiased estimator (real estimates from 4.84 to 1.57% and 5.61 to 2.06% in imaginary estimates). Studies with normal subjects show the same dispersion pattern, which decreases if the generator nonlinearities are reduced. These results supply substantial evidence that reducing generator nonlinearities can contribute to the production of more reliable mechanical impedance FOT measurements.

Linear servo-controlled pressure generator for forced oscillation measurements.

In respiratory input impedance measurements, the low-frequency range contains important clinical and physiological information. However, the patient's spontaneous ventilation can contaminate the data in this range, leading to unreliable results. Unbiased estimators are a good alternative to overcome this problem, provided that the generator is considered linear. This condition is not fulfilled by most existing generators as they are based on loudspeakers, which have strong nonlinearities. The present work aims to contribute to the solution of this problem, and describes a pressure generator that minimises the nonlinearities by an optical sensor placed in a position feedback loop. The static evaluation shows a high linearity for the optical system. The well known frequency response of pressure transducers is used in the dynamic evaluation of the instrument. The analysis of the generator shows that the use of position feedback improved the frequency response. The total harmonic distortion (THD) measurement shows that closed loop resulted in an effective decrease in the nonlinearities. The reduction of THD achieved by the servo-controlled generator can contribute to the practical implementation of the unbiased estimators, increasing the reliability of the impedance data, especially in the low-frequency range. This system is compared with conventional generators and with another servo-controlled system.