[Wheezing during normal breathing as a sign of bronchial obstruction]

Wheezing is a clinical feature in patients with chronic obstructive airway diseases. Long-term monitoring of wheezing could provide a new dimension of diagnostic information as compared to lung function if wheezing really does represent airway obstruction. Patients with wheezing who were part of our Marburg Respiratory Sound Database (MARS) were studied. 20 patients with asthma and 17 patients with chronic obstructive pulmonary disease (COPD) were analysed with respect to pathological changes of lung function parameters. The patients were matched with persons without wheezing in regard to age, diagnosis and sex. Additionally, 58 healthy persons with normal lung function tests were analysed for the occurrence of spontaneous wheezing during normal breathing. In patients with wheezing, at least one parameter of lung function was pathological. For asthmatic patients significant differences for MEF (50) (p = 0.011), R (tot) (p = 0.002) and Tiffeneau (p = 0.001) were found. In patients with COPD significant differences for FEV (1) (p = 0.002) and MEF (50) (p = 0.030) were found. In none of the healthy persons with normal lung function did we find wheezing. Wheezing as a clinical sign of bronchial obstruction is useable for long-term monitoring. The method provides additional information that can help to monitor nocturnal asthma.

[Obscure coughing and the feeling of suffocation during sleep. Long-term nocturnal acoustic recording]

A 58-year old male presented with a 6-week history of increasing nocturnal cough, dyspnea and awakening. Physical examination, chest auscultation and lung function in the daytime did not show any pathological findings. Only nocturnal long-term recording of respiratory sounds was helpful: In- and expiratory wheezing, as the acoustic manifestation of airway obstruction, was found throughout the night. As the cause for nocturnal cough and distinct airway obstruction, a pansinusitis with postnasal drip syndrome was diagnosed.

[Nocturnal long-term recording of breath sounds in patients with bronchial asthma -- a reasonable diagnostic option?]

Alterations in normal breath sounds are an important indication of pathophysiological processes in the bronchial system and the lung. In the presence of non-specific symptoms like dyspnea, wheezing or cough while sleeping it seems reasonable to make a nocturnal long-term recording of breath sounds. Thus specific auscultation phenomena can be recorded qualitative and particularly quantitative in the course. A mobile recording system provides a non-invasive monitoring at home which is independent of vigilance. Furthermore it can be used for follow-up examinations of medical interventions.

Warum ist die obstruktive Schlafapnoe (OSA) ein kardiovaskul�rer Risikofaktor?

Patients with obstructive sleep apnea (OSA) frequently suffer from cardiovascular diseases. Mechanisms like intrathoracic pressure variations, changes in blood gases (hypoxia), arousals and neurohumeral adaptation mechanisms, combined with breathing disorders are causing these cardiovascular sequelae. In particular repetitive hypoxemia and activation of the sympathetic nervous system have to be considered as stressors for the cardiovascular system. Special clinical findings should take OSA into consideration as a differential diagnosis. A systematic anamnesis with questions to daytime conditions (hypersomnia, decrease of performance), snoring and apneas while sleeping is easy to ascertain, and will lead to the correct diagnosis in more than 90% of cases. The extent and need for therapy should be assessed by three criteria: 1) daytime symptoms, 2) the extent of breathing disorder and 3) cardiovascular comorbidity.

[Effect of subcutaneous fatty tissue on normal respiratory sounds]

Auscultation is an important, non-invasive and simple measure in the diagnosis of lung diseases that can detect sometimes pathological processes prior to radiography. Attempts have already been made to automatically detect characteristic pathological sounds, but a knowledge of potential influencing factors is a must for correct interpretation. In this study we have investigated the effect of the subcutaneous fat layer on normal lung sounds. This is of importance to determine corrective factors for the automatic detection of bronchial breathing in pneumonia. The lung sounds of 125 healthy people (55f, 70m) were digitally recorded at four different positions of the thorax (3. ICR paravertebral, 7. ICR medioscapular, all left and right). Evaluation was done separately for gender. The subcutaneous fat layer was measured with a Holtain Skinfold Caliper at the identical four recording positions. For a quantitative evaluation of the sounds we calculated the relative power of frequency bands 330-600 Hz and 60-330 Hz and their ratio. The relation between these parameters and the subcutaneous fat layer was analyzed with the Pearson correlation. The results of this study show that the influence of subcutaneous fat layer is negligible and can be ignored in the automatic detection of lung sounds.

[Acoustic follow-up of nocturnal bronchial obstruction therapy]

Long acting beta 2-agonists belong to the basic therapy of COPD. Especially patients with nocturnal respiratory problems may benefit from this therapy. Long term recording of lung sounds is a new method for quantitative measurements of bronchial obstructions. In combination with polysomnography an evaluation of cardiorespiratory parameters and sleep structure is possible. A total of 10 patients (8 male and 2 female) with moderate COPD (FEV1 58 +/- 11 %) and signs of bronchial obstruction were investigated. The combination of acoustic long term recording and polysomnography was done for 2 or 3 nights without and under therapy (long acting beta 2-agonist, 50 microg Salmeterol). In all patients we could find nocturnal bronchial obstruction events. Nocturnal wheezing time was reduced during therapy to 33 +/- 17 % (1. therapy night, n. s.) compared to 49 +/- 30 % without therapy (control night) and to 17 +/- 17 % (2. therapy night, n = 6, p < 0.05) vs. 51 +/- 30 % (control night, n = 6). Sleep efficiency and REM sleep increased (n. s.) under therapy, deep sleep stages NREM III/IV were nearly the same. Acoustic long term monitoring confirms the reduction of nocturnal bronchial obstructions under therapy with beta 2-agonists. A better sleep quality may be expected from the improvement of the respiratory situation during sleep.

Detection of bronchial breathing caused by pneumonia

The classic auscultation with stethoscope is the established clinical method for the detection of lung diseases. The interpretation of the sounds depends on the experience of the investigating physician. Therefore, a new computer-based method has been developed to classify breath sounds from digital lung sound recordings. Lung sounds of 11 patients with one-sided pneumonia and bronchial breathing were recorded on both the pneumonia side and on contralateral healthy side simultaneously using two microphones. The spectral power for the 300-600 Hz frequency band was computed for four respiratory cycles and normalized. For each breath, the ratio R between the time-segments (duration = 0.1 s) with the highest inspiratory and highest expiratory flow was calculated and averaged. We found significant differences in R between the pneumonia side (R = 1.4 +/- 1.3) and the healthy side (R = 0.5 +/- 0.5; p = 0.003 Wilcoxon-test) of lung. In 218 healthy volunteers we found R = 0.3 +/- 0.2 as a reference-value. The differences of ratio R (delta R) between the pneumonia side and the healthy side (delta R = 1.0 +/- 0.9) were significantly higher compared to follow-up studies after recovery (delta R = 0.0 +/- 0.1, p = 0.005 Wilcoxon-test). The computer based detection of bronchial breathing can be considered useful as part of a quantitative monitoring of patients at risk to develop pneumonia.