The expiration reflex from the vocal folds

The authors present their 30 years’ experience with expiration reflex. The reflex can be elicited from vocal folds by mechanical, chemical or electrical stimulation of the superior laryngeal nerve of man and laboratory animals, except mice and rats. It manifests itself by a short, forcible expiratory effort without a preceding inspiration which is indispensable for cough effort. The role of expiration reflex is to prevent penetration of foreign bodies into airways, expelling phlegm and detritus from subglottal area. The initial inspiration before expiration is undesired and could lead to inspiration pneumonia. The reflex is well known to laryngologists as „laryngeal cough.” Its receptors are small in number, localised mainly in medial margin of vocal folds deep in mucosa which can explain their stability in pathological conditions of the larygx. Afferentiation of the reflex is via laryngeal nerve similarly to sneezing and cough. Expiration reflex is not co-ordinated by a single „centre” but rather by a network system in the brain stem. Its motor pattern is supposedly produced by „multifunctional” population of medullar neurones in Bötzinger complex and the rostral ventral respiratory group involved also in the genesis of breathing and cough. However, in cats also other neurones may play a vital role in production, shaping and mediation of the motor pattern of respiratory reflex, localised in rostral pons, lateral tegmental field or in the raphe medullar midline

Cough quality in children: a comparison of subjective vs. bronchoscopic findings

BACKGROUND: Cough is the most common symptom presenting to doctors. The quality of cough (productive or wet vs dry) is used clinically as well as in epidemiology and clinical research. There is however no data on the validity of cough quality descriptors. The study aims were to compare (1) cough quality (wet/dry and brassy/non-brassy) to bronchoscopic findings of secretions and tracheomalacia respectively and, (2) parent's vs clinician's evaluation of the cough quality (wet/dry). METHODS: Cough quality of children (without a known underlying respiratory disease) undergoing elective bronchoscopy was independently evaluated by clinicians and parents. A 'blinded' clinician scored the secretions seen at bronchoscopy on pre-determined criteria and graded (1 to 6). Kappa (K) statistics was used for agreement, and inter-rater and intra-rater agreement examined on digitally recorded cough. A receiver operating characteristic (ROC) curve was used to determine if cough quality related to amount of airway secretions present at bronchoscopy. RESULTS: Median age of the 106 children (62 boys, 44 girls) enrolled was 2.6 years (IQR 5.7). Parent's assessment of cough quality (wet/dry) agreed with clinicians' (K = 0.75, 95%CI 0.58–0.93). When compared to bronchoscopy (bronchoscopic secretion grade 4), clinicians' cough assessment had the highest sensitivity (0.75) and specificity (0.79) and were marginally better than parent(s). The area under the ROC curve was 0.85 (95%CI 0.77–0.92). Intra-observer (K = 1.0) and inter-clinician agreement for wet/dry cough (K = 0.88, 95%CI 0.82–0.94) was very good. Weighted K for inter-rater agreement for bronchoscopic secretion grades was 0.95 (95%CI 0.87–1). Sensitivity and specificity for brassy cough (for tracheomalacia) were 0.57 and 0.81 respectively. K for both intra and inter-observer clinician agreement for brassy cough was 0.79 (95%CI 0.73–0.86). CONCLUSIONS: Dry and wet cough in children, as determined by clinicians and parents has good clinical validity. Clinicians should however be cognisant that children with dry cough may have minimal to mild airway secretions. Brassy cough determined by respiratory physicians is highly specific for tracheomalacia

The effect of the pulsatile electromagnetic field in children suffering from bronchial asthma

From the bibliography it is well known that pulsatile electromagnetic field has an anti-inflammatory and analgesic effect. It causes vasodilatation, myorelaxation, hyper-production of connective tissue and activation of the cell membrane. Therefore our aim was to study the possible therapeutic effect of pulsatile electromagnetic field in asthmatic children. Forty-two children participating in this study were divided in two groups. The 1st group consisting of 21 children (11 females, 10 males, aged 11.8±0.4 yr) was treated by pulsatile electromagnetic field and pharmacologically. The 2 nd group served as control, consisting also of 21 children (11 females, 10 males, aged 11.7±0.3 yr) and was treated only pharmacologically. Therapeutic effect of the pulsatile electromagnetic field was assessed on the basis of pulmonary tests performed by means of a Spirometer 100 Handi (Germany). The indexes FVC, IVC, ERV, IRV, FEV1, FEV1/FVC%, MEF75,50,25, PEF, PIF and the changes of the flow-volume loop were also registered. The pulsatile electromagnetic field was applied by means of the device MTU 500H, Therapy System (Brno, Czech Republic) for 5 days, two times daily for 30 minutes (magnetic induction: 3 mT, frequency: 4 Hz as recommended by the manufacturer). The results in children of the 1st group showed an improvement of FVC of  about 70 ml, IVC of about 110 ml, FEV1 of about 80 ml, MEF75 of about 30 ml, PEF of about 480 ml, PIF of about 550 ml. The increases of ERV, IRV and FEV1/FVC and decreases of MEF25,50 were statistically insignificant. The results in the 2nd group were less clear. The flow-volume loop showed a mild improvement in 14 children. This improvement in the 2nd group was less significant. The clinical status of children and their mood became better. We believe hat the pulstatile electro-magnetotherapy in children suffering from asthma is effective. On the basis of our results we can recommend it as a complementary therapy

Analysis of the cough sound frequency in adults and children with bronchial asthma

It is well known that the frequency distribution of cough sound varies in different pathological conditions. Its identification could have diagnostic value. In this study the cough sound frequency in adults (n=20, 51.7±11 yrs), children (n=21, 11.8±0.4 yrs) asthmatics and healthy volunteers (n=25, 21 yrs) was explored. All patients were suffering from bronchial asthma. They were on a stable therapeutic regime and in a quiet status. Voluntary cough sound was recorded by a microphone and a tape recorder and digitally processed. Overlapping technique and Fast Fourier Transform were used to estimate the sound spectra. The records were smoothed by the method of Pascal triangle. They demonstrate the mean values of cough sound spectra. The registered pseudo three-dimensional plots of cough sound frequency (1 K spectra as function in time) of adults showed that the intensity of frequencies increased from 100 to 900 Hz in 3-4 waves. These frequencies afterwards decreased and between 1 to 2 kHz a smaller elevation was present. The spectra of children resembled to the spectrum of adults but had a smoother course. The spectra of asthmatics had some specificity and differed from the spectrum of healthy volunteers

Convex Models for Optimal Utility-Based Distributed Generation Allocation in Radial Distribution Systems

© 2007-2012 IEEE. This paper introduces various models for optimal and maximal utility-based distributed generation penetration in the radial distribution systems. Several problems with different probabilistic indices as objective functions constrained by power flow equations, distributed generation penetration, voltage, and thermal limits are proposed to obtain the optimal penetration of distributed generations on rural distribution networks. There are tradeoffs between interests and risks that the distribution network operators or distribution companies may be willing to take on. Thus, to have an effective method for maximal allocation of distributed generations, new indices are proposed, and the problems are formulated as a risk-constrained optimization model. The obtained problems have mixed-integer nonlinear programming and nonconvex forms because of nonlinearity and nonconvexity of the optimal power flow (OPF) equations and indices, leading to computationally nondeterministic polynomial-time-hard problems. Accordingly, in this paper, convex relaxations of OPF are introduced instead of the conventional nonlinear equations. Efficient linear equivalents of the objective function and constraints are introduced to reduce the computational burden. Test results of the proposed models on a radial distribution system are presented and discussed