Identification and characterization of near-fatal asthma phenotypes by cluster analysis.

BACKGROUND: Near-fatal asthma (NFA) is a heterogeneous clinical entity and several profiles of patients have been described according to different clinical, pathophysiological and histological features. However, there are no previous studies that identify in a unbiased way--using statistical methods such as clusters analysis--different phenotypes of NFA. Therefore, the aim of the present study was to identify and to characterize phenotypes of near fatal asthma using a cluster analysis. METHODS: Over a period of 2 years, 33 Spanish hospitals enrolled 179 asthmatics admitted for an episode of NFA. A cluster analysis using two-steps algorithm was performed from data of 84 of these cases. RESULTS: The analysis defined three clusters of patients with NFA: cluster 1, the largest, including older patients with clinical and therapeutic criteria of severe asthma; cluster 2, with an high proportion of respiratory arrest (68%), impaired consciousness level (82%) and mechanical ventilation (93%); and cluster 3, which included younger patients, characterized by an insufficient anti-inflammatory treatment and frequent sensitization to Alternaria alternata and soybean. CONCLUSIONS: These results identify specific asthma phenotypes involved in NFA, confirming in part previous findings observed in studies with a clinical approach. The identification of patients with a specific NFA phenotype could suggest interventions to prevent future severe asthma exacerbations.

Maximum respiratory pressures in trumpet players.

We studied whether experienced trumpet players can develop higher pressures with their inspiratory and expiratory muscles than untrained subjects. Twelve male trumpet players (mean age, 22.4 +/- 3.3 years) participated in the study. All of them had played the trumpet for at least 4 years and were nonsmokers. Twelve healthy male subjects (mean age, 23.3 +/- 3.1 years) participated as a control group. There were no differences in spirometric parameters between both groups. Maximum respiratory pressures were higher in the trumpet player group (trumpet players: Pmax 151.3 +/- 19.8 cm H2O; Pemax, 234.6 +/- 53.9 cm H2O; control group: Pemax, 106.7 +/- 10.4 cm H2O; Pemax, 189.6 +/- 14.6 cm H2O). We concluded that in young trumpet players, maximum respiratory pressures are higher than in young people who do not play wind instruments. This is most probably a consequence of respiratory muscle training with a wind instrument.

Spirometry and maximal respiratory pressures in patients with facial paralysis.

The study included 17 patients with facial paralysis (FP) (10 male, 7 female) aged 47.6 +/- 21.0 years. Twelve of the 17 patients had Bell's palsy. The other causes of FP were as follows: one, polyradiculoneuritis; one, war injury; one, cerebrovascular accident; one, sarcoidosis; and one, dermatomyositis. Spirometry and maximal respiratory pressures (PImax and PEmax) were performed with three different techniques: without holding the lips, with patient holding lips, and with technician holding lips. We observed significant differences for PImax and PEmax among the three methods. There were no differences for spirometric values. In nine of the patients with Bell's palsy, PImax, PEmax, and spirometry tests were repeated two months after the first determination. With respect to the first determination, the values of Pmax-w/v holding lips increased, yet spirometric values were similar. In conclusion, PImax and PEmax can be an index of clinical FP evolution. Spirometric maneuvers can be performed with either patient or technician holding lips to ensure a perfect seal between lips and mouthpiece.

Analysis of tracheal sounds during forced exhalation in asthma patients and normal subjects: bronchodilator response effect.

PURPOSE: During the past 10 years, the acoustic analysis of breath sounds has been used as a diagnostic tool in patients suffering from obstructive respiratory diseases. Acoustic analysis might be able to monitor the response to bronchodilator therapy in a clinical setting. So far, few studies have been carried out in asthmatic patients. To assess the responses of a sampling of asthma patients to an inhaled bronchodilator (terbutaline) by means of spectral analysis of the tracheal sound performed during forced expiratory maneuvers. MATERIAL AND METHODS: Seventeen nonsmoking asthma patients (9 were male, 8 were female) who had been suffering from the disease for > or = 15 years were included in the study, as were 15 normal subjects (7 were male, 8 were female). The average age (+/- SD) was 56.5 +/- 15.2 years (FVC, 2.7 +/- 0.9 L [63.4%]; FEV1, 1.5 +/- 0.6 L [53.0%]). The tracheal sounds were collected during three forced expiratory maneuvers with a sampling frequency of 5,000 Hz and were analyzed by applying a 16-parameter autoregressive model. RESULTS: The centroid frequency decreased after the bronchodilator was given at different flow segments between 1.2 and 0.4 L/s, with significant changes between 0.6 and 0.4 L/s. CONCLUSIONS: Patients with asthma showed changes in the spectral acoustic analysis frequencies after the administration of a bronchodilator drug (terbutaline) during forced expiratory maneuvers.

Postural variation of the maximum inspiratory and expiratory pressures in normal subjects.

The maximum static inspiratory and expiratory pressures (MIP and MEP, respectively) were measured in 15 normal male subjects (average age, 27.14 years) in standing and sitting position. The MIP was determined at RV and FRC and MEP was determined at TLC and FRC. No significant differences were found for these parameters between the two postures. Our study proves that the posture adopted by the subject when these two maneuvers are performed does not influence the results obtained.

Effects of inhaled platelet activating factor on bronchial responsiveness in patients with symptomatic and asymptomatic pulmonary embolism.

To determine the possible role of platelet-activating factor (PAF) in pulmonary embolism (PE), the reactivity of the airways to inhaled PAF, using doses ranging from 6.25 to 400 micrograms, was examined in 24 patients with a past episode of PE. Twelve of these patients had experienced acute respiratory insufficiency during the episode (with or without additional symptoms). None of the remaining 12 patients had experienced any respiratory symptoms during the PE episode. Diagnosis was established by means of a ventilation-perfusion lung scan performed when admitted to the hospital because of deep venous thrombosis (DVT) in the lower limbs. Nonspecific bronchial reactivity as measured by the response to bronchoprovocation testing with methacholine showed no significant differences between both groups. PAF caused a dose-dependent bronchoconstriction defined by at least a 35 percent decrease in specific airway conductance (SGaw) in all patients. The average dose of PAF needed to decrease SGaw 35 percent was significantly lower in patients who had had a symptomatic PE than in those with asymptomatic PE (p = 0.011). This finding suggests that patients who suffered from symptomatic PE may present a greater airway reactivity to inhaled PAF. This different behavior might explain the existence of some of the respiratory symptoms of PE, which could be attributed to PAF-related effects. However, additional studies are needed to evaluate the role of PAF in PE.

Acoustic analysis of vowel emission in obstructive sleep apnea.

UNLABELLED: We studied vocalization in 18 men with obstructive sleep apnea syndrome (OSAS) (age, 49 [7.5] years; body mass index [BMI] 33.6 [7.6]) and 10 normal men as a control group (age, 46.7 [6.2] years; BMI 24.6 [2.2]). Polysomnographic data for patients with OSAS were as follows: total sleep time (TST), 387.5 [27.9] min; awake, 17.6 (12.6% TST); stage 1, 19.8 (18.7 percent TST); stage 2, 54.8 (23.2 percent TST); stage 3 and 4, 1.5 (0.3 percent TST); and stage REM, 4.2 (1.7 percent TST). Apnea hypopnea index (AHI) was 43.0 (18.2) and lowest O2 saturation was 73.6 (11.4). We recorded the following sounds in all subjects: /a/ as in "father"; /e/ as in "get"; /i/ as in "see"; /o/ as in "go"; /u/ as in "too." Three maneuvers for each vowel sound were taken for analysis. Signals were digitized at 10,000 Hz. Fast Fourier transformation was applied to segments of 512 points of each utterance corresponding to the vowel sound. The following parameters were obtained: maximum frequency of harmonics, mean frequency of harmonics, and the number of harmonics. RESULTS: There were significant differences between both groups in the maximum frequency of harmonics of /i/ and /e/ vowels. (For /i/: 2,650 [672] Hz controls; 425 [71.2] Hz OSAS. For /e/: 2,605 [772.3] Hz controls; 1,250.0 [828.4] OSAS). The number of harmonics for /i/ vowel was 4.5 (1.2) for controls as compared with 2.7 (1) Hz for OSAS. CONCLUSIONS: Vocalization in patients with OSAS is different from normal subjects. Vowel /i/ can distinguish these patients from normal subjects.

nCPAP treatment interruption in OSA patients.

This study has investigated the effect of interrupting nasal continuous positive airway pressure (nCPAP) therapy on 10 obstructive sleep apnoea (OSA) patients (nine male, one female) (53.6 +/- 7.3 years) treated over 2 years. The effect of nCPAP interruption was determined by variations in sleep counts and gasometric values during five consecutive nights. On the first night, the patient used his habitual nCPAP. On the remaining nights, nasal nCPAP was not applied. The apnoea-hypopnoea index (AHI) was found to increase significantly in the second night, attaining a similar level to that of the basal study (2 years ago). SaO2 minimum decreased and PaCO2 increased in the second night with respect to the first night. The interruption of nCPAP therapy in OSA patients treated over a long period of time increases the sleep counts and impairs the gasometric parameters. Consequently, any change in nCPAP time therapy must be checked to avoid negative effects.

Maximum inspiratory and expiratory pressures have no daytime variation in healthy men.

The variation of maximal respiratory pressures (Pimax and Pemax) in healthy subjects were studied on the same day in 16 non-smoking healthy men (age 26.2 +/- 3.2 years). The Pimax and Pemax were obtained on three occasions (8 a.m., 2 p.m. and 9 p.m.) within the same day. There were no differences between readings for Pimax and Pemax values.

Study of myographic signals from sternomastoid muscle in patients with chronic obstructive pulmonary disease.

Analysis of the respiratory muscle activity is a promising technique for diagnosis of respiratory diseases, such as chronic obstructive pulmonary disease (COPD). The sternomastoid muscle (SMM) was selected to study the activity of respiratory muscles due to its accessibility in order to define a noninvasive analysis. The aims of this work are two: analyze the relationship between the SMM function and pulmonary obstruction, and study the influence of spectral estimator on frequency parameters related with the muscle activity. For the first goal, we propose the analysis of vibromyographic and electromyographic signals from the SMM to study the muscle function during two ventilatory tests. Activity of SMM was found by means of several indexes: root-mean-square (rms) values, mean and median frequencies, and ratio between high and low-frequency components. For the second goal, spectral analysis was performed by means of nonparametric methods: Correlogram and Welch periodogram, and parametric methods: autoregressive (AR), moving average (MA), and ARMA models. It is deduced that these indexes show muscle activity and certain fatigue of the SMM, whose muscle function depends on the level of pulmonary obstruction, and they depend a lot of spectral estimator being the more suitable an AR model with high order.

Influence of estimators of spectral density on the analysis of electromyographic and vibromyographic signals.

Electromyographic (EMG) and vibromyographic (VMG) signals are related to electrical and mechanical muscle activity, respectively. It is known that variations in their frequency components are related to changes in muscle activity and fatigue. The aims of this study were: (1) to analyse the resolution, variance and bias of different estimations of power spectral density function (PSD); and (2) to evaluate the influence of the spectral estimation method on three indices calculated from the PSD of EMG and VMG signals: mean (f(m)) and median (f(c)) frequencies and the ratio of high and low frequency components (H/L ratio) to select the most suitable estimator. Myographic signals were recorded from the sternomastoid muscle, an accessory respiratory muscle, during breathing. For non-parametric methods, Welch periodograms and correlograms were analysed with different windows. Autoregressive (AR) moving average (MA) and ARMA models with different orders were evaluated in the parametric methods. The reproducibility of the results was also studied. Frequency indices, particularly the H/L ratio and f(c), changed considerably when varying the following parameters of the estimators: periodogram with segment durations longer than 150 ms in EMG and with any duration in VMG signals; correlogram with window length shorter than 10% of the total number of samples; and AR models with an order lower than 10, 20 and 40 in f(c), fm and H/L ratio, respectively, in both myographic signals.

[Factors associated with pleural thickening in pleural tuberculosis. Review of 99 cases]. / Factores asociados al engrosamiento pleural en la pleuritis tuberculosa. Análisis de 99 casos.

OBJECTIVE: To analyze which factors were related to the development of pleural thickening in pleural tuberculosis (PT). METHODS: We reported 99 patients diagnosed as having PT separated into two different groups according to the presence of radiographic pleural thickening after completing the treatment: normal chest roentgenogram (group 1) or pleural thickening (group 2). We compared: clinical history, chest radiography, pleural fluid analysis, microbiological studies and effects of the treatment. RESULTS: 35 cases in group 1 (35.35%) and 64 in group 2 (64.45%). All the compared results did not differ between the two groups, excluding a higher incidence of febrile cases, increased white cell count and decreased relative percentage of pleural lymphocytes in group 1, and increased number of cases with hemoptysis, positive sputum cultures in patients with parenchymal infiltrates, relative percentage of pleural lymphocytes and decreased white cell count in group 2. CONCLUSIONS: We reported an elevated incidence of residual pleural thickening, but it is unlikely that all the cases could have any clinical significance. We didn't confirm a characteristic pattern. Our findings suggested that a different reaction related or not to the hypersensitivity, rather than the inflammatory response to infection was the responsible for the fibrosis.

Cardiac interference reduction in diaphragmatic MMG signals during a Maintained Inspiratory Pressure Test.

A recursive least square (RLS) adaptive filtering algorithm for reduction of cardiac interference in diaphragmatic mecanomyographic (MMGdi) signals is addressed in this paper. MMGdi signals were acquired with a capacitive accelerometer placed between 7th and 8th intercostal spaces, on the right anterior axillary line, during a maintained inspiratory pressure test. Subjects were asked to maintain a constant inspiratory pressure with a mouthpiece connected to a closed tube (without breathing). This maneuver was repeated at five different contraction efforts: apnea (no effort), 20 cmH2O, 40 cmH2O, 60 cmH2O and maximum voluntary contraction. An adaptive noise canceller (ANC) using the RLS algorithm was applied on the MMGdi signals. To evaluate the behavior of the ANC, the MMGdi signals were analyzed in two segments: with and without cardiac interference (WCI and NCI, respectively). In both segments it was analyzed the power spectral density (PSD), and the ARV and RMS amplitude parameters for each contraction effort. With the proposed ANC algorithm the amplitude parameters of the WCI segments were reduced to a level similar to the one of the NCI segments. The obtained results showed that ANC using the RLS algorithm allows to significantly reduce the cardiac interference in MMGdi signals.

Respiratory and spontaneous arousals in patients with Sleep Apnea Hypopnea Syndrome.

Sleep in patients with Sleep Apnea-Hypopnea Syndrome (SAHS) is frequently interrupted with arousals. Increased amounts of arousals result in shortening total sleep time and repeated sleep-arousal change can result in sleep fragmentation. According to the American Sleep Disorders Association (ASDA) an arousal is a marker of sleep disruption representing a detrimental and harmful feature for sleep. The nature of arousals and its role on the regulation of the sleep process raises controversy and has sparked the debate in the last years. In this work, we analyzed and compared the EEG spectral content of respiratory and spontaneous arousals on a database of 45 SAHS subjects. A total of 3980 arousals (1996 respiratory and 1984 spontaneous) were analyzed. The results showed no differences between the spectral content of the two kinds of arousals. Our findings raise doubt as to whether these two kinds of arousals are truly triggered by different organic mechanisms. Furthermore, they may also challenge the current beliefs regarding the underestimation of the importance of spontaneous arousals and their contribution to sleep fragmentation in patients suffering from SAHS.

All night analysis of time interval between snores in subjects with sleep apnea hypopnea syndrome.

Sleep apnea-hypopnea syndrome (SAHS) is a serious sleep disorder, and snoring is one of its earliest and most consistent symptoms. We propose a new methodology for identifying two distinct types of snores: the so-called non-regular and regular snores. Respiratory sound signals from 34 subjects with different ranges of Apnea-Hypopnea Index (AHI = 3.7-109.9 h(-1)) were acquired. A total number of 74,439 snores were examined. The time interval between regular snores in short segments of the all night recordings was analyzed. Severe SAHS subjects show a shorter time interval between regular snores (p = 0.0036, AHI cp: 30 h(-1)) and less dispersion on the time interval features during all sleep. Conversely, lower intra-segment variability (p = 0.006, AHI cp: 30 h(-1)) is seen for less severe SAHS subjects. Features derived from the analysis of time interval between regular snores achieved classification accuracies of 88.2 % (with 90 % sensitivity, 75 % specificity) and 94.1 % (with 94.4 % sensitivity, 93.8 % specificity) for AHI cut-points of severity of 5 and 30 h(-1), respectively. The features proved to be reliable predictors of the subjects' SAHS severity. Our proposed method, the analysis of time interval between snores, provides promising results and puts forward a valuable aid for the early screening of subjects suspected of having SAHS.

Normal non-regular snores as a tool for screening SAHS severity.

Snoring is one of the earliest and most consistent sign of upper airway obstruction leading to Sleep Apnea-Hypopnea Syndrome (SAHS). Several studies on post-apneic snores, snores that are emitted immediately after an apnea, have already proven that this type of snoring is most distinct from that of normal snoring. However, post-apneic snores are more unlikely and sometimes even inexistent in simple snorers and mild SAHS subjects. In this work we address that issue by proposing the study of normal non-regular snores. They correspond to successive snores that are separated by normal breathing cycles. The results obtained establish the feasibility of acoustic parameters of normal non-regular snores as a promising tool for a prompt screening of SAHS severity.

Regular and non regular snore features as markers of SAHS.

Sleep Apnea-Hypopnea Syndrome (SAHS) diagnosis is still done with an overnight multi-channel polysomnography. Several efforts are being made to study profoundly the snore mechanism and discover how it can provide an opportunity to diagnose the disease. This work introduces the concept of regular snores, defined as the ones produced in consecutive respiratory cycles, since they are produced in a regular way, without interruptions. We applied 2 thresholds (TH(adaptive) and TH(median)) to the time interval between successive snores of 34 subjects in order to select regular snores from the whole all-night snore sequence. Afterwards, we studied the effectiveness that parameters, such as time interval between successive snores and the mean intensity of snores, have on distinguishing between different levels of SAHS severity (AHI (Apnea-Hypopnea Index) < 5h(-1), AHI <10 h(-1), AHI < 15 h(-1), AHI < 30 h(-1)). Results showed that TH(adaptive) outperformed TH(median) on selecting regular snores. Moreover, the outcome achieved with non-regular snores intensity features suggests that these carry key information on SAHS severity.

Analysis of forced wheezes in asthma patients.

BACKGROUND: Spirometric parameters can be normal in many stable asthma patients, making a diagnosis difficult at certain times in the course of disease. OBJECTIVES: The present study aims to find differences and similarities in the acoustic characteristics of forced wheezes among asthma patients with and without normal spirometric values. METHODS: Eleven chronic asthma patients (8 men/3 women) with moderate-to-severe airway obstruction (FEV1 48.4%), 9 stable asthma patients (6 males/3 females) with normal spirometry (FEV1 84.0%) and a positive methacholine test and 14 healthy subjects (8/6) were enrolled in the study. A contact sensor was placed on the trachea, and wheezes were detected by a modified Shabtai-Musih algorithm in a time-frequency representation. RESULTS: More wheezes were recorded in obstructive asthma patients than in stable asthma and control subjects: nonstable asthma 13.6 (13.3), stable asthma 3.5 (3.0) and control subjects 2.5 (2.1). The mean frequency of all wheezes detected was higher in control subjects than in either stable or non-stable asthma patients. The change in the total number of wheezes after terbutaline inhalation was more pronounced in nonstable asthma patients than in stable asthmatics and control subjects. CONCLUSIONS: This study confirms that wheeze recording during forced expiratory maneuvers can be a complementary measure to spirometry to identify asthma patients.