[Science of symptomology: coughs. Development and physiopathology of cough].
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STUDY OBJECTIVE: To analyze the cough response to three airway challenges in order to clarify whether the recording of the provoked coughs would be beneficial in the management of asthma. DESIGN: A prospective study. SETTING: University hospital. PARTICIPANTS: Fifteen healthy subjects, 16 steroid-naïve subjects with asthma, and 16 subjects with steroid-treated asthma. INTERVENTIONS: Inhalation challenges with isotonic histamine, hypertonic saline solution, and hypertonic histamine, using an ultrasonic nebulizer and 2-min tidal breathing method. MEASUREMENTS: Airflow parameters were measured with a spirometer, and the coughs were recorded manually. RESULTS: Coughing during the isotonic histamine challenge was associated with the degree of the bronchoconstriction induced. When this was taken into account, the healthy subjects coughed as frequently as the asthmatic subjects. During the two hypertonic challenges, the asthmatic subjects coughed more frequently than did the healthy subjects when the induced bronchoconstriction had not yet developed. At that stage of the hypertonic saline solution challenge, the mean coughing frequency was 0.7 coughs per minute (95% confidence interval [CI], 0.03 to 1.3 coughs per minute) for the healthy subjects, 2.7 coughs per minute (95% CI, 0.8 to 4.5 coughs per minute) for the steroid-naïve asthmatic subjects, and 1.3 coughs per minute (95% CI, 0.6 to 1.9 coughs per minute) for the steroid-treated asthmatic subjects (p = 0.018). For the hypertonic histamine challenge, the respective values were 0.8 coughs per minute (95% CI, 0.4 to 1.2 coughs per minute), 3.6 coughs per minute (95% CI, 2.4 to 4.9 coughs per minute), and 2.1 coughs per minute (95% CI, 1.0 to 3.1 coughs per minute; p = 0.001). This cough did not correlate with airway hyperresponsiveness. CONCLUSIONS: Coughing during isotonic histamine challenge seems to be a manifestation of bronchoconstriction, and recording of the coughs may not provide additional information to airflow measurements. Frequent coughing during hypertonic saline solution and hypertonic histamine challenges in the absence of bronchoconstriction is a pathologic phenomenon. Sensitivity to the cough-provoking effect of hypertonic challenges seems to be enhanced in patients with asthma but unrelated to airway hyperresponsiveness. Therefore, the recording of the provoked coughs during these challenges may add to the information obtained from airflow measurements.
Cough-related variables such as cough frequency, time to onset (i.e. the time until the first cough occurs) and the cough index (i.e. the ratio between the cough frequency and the time to onset) may be important when interpreting results of cough challenges for therapeutic interventions or for comparative research purposes. Nevertheless, repeatability (or reproducibility) for these widely used variables has been poorly studied. In thirty normal subjects, coughing was induced by inhalation of threshold (T) and suprathreshold (1.6 x T) concentrations of ultrasonically nebulized distilled water (fog). Cough threshold was taken as the lowest fog concentration that evoked at least one cough effort during two challenges separated by a 30-min interval. During challenges performed at both threshold and suprathreshold stimulus intensity, cough frequency, time to onset, and the cough index were assessed; within-subject repeatability for these variables was subsequently evaluated. Median +/- interquartile range cough threshold value was 0.9+/-0.5 mL x min(-1). During the two challenges performed to assess cough threshold, the mean +/-SD values of cough frequency, time to onset, and cough index were similar (5.0+/-2.7 and 5.3+/-3.1 coughs x min(-1), 32.4+/-13.3 and 32.9+/-13.6 s, and 0.2+/-0.2 and 0.2+/-0.2, respectively). However, none of these cough-related variables proved to be sufficiently repeatable. During the two challenges performed at suprathreshold stimulus intensity, mean values of cough frequency, time to onset, and cough index were also similar (20.0+/-9.0 and 18.2+/-10.2 coughs x min(-1), 13.5+/-5.8 and 12.0+/-4.62 s, and 1.7+/-1.0 and 1.8+/-1.2); furthermore, all considered variable of suprathreshold challenge turned out to be reproducible. In conclusion, during fog challenges at threshold stimulus intensity, cough frequency, time to onset and cough index cannot reliably be used for evaluating cough responses. However, these cough-related variables may represent useful and reliable research tools in the evaluation of suprathreshold cough responses.
BACKGROUND: In asthma, measurements of airway inflammation correlate poorly with clinical markers and airway hyperresponsiveness. While the relation between determinants of asthma severity is known, that for cough is unknown. We hypothesised that cough sensitivity changes relate to changes in cough scores and objectively measured cough frequency. AIMS: To examine the relation between commonly used outcome measurements of cough severity in children. METHODS: The concentration of capsaicin causing two and five or more coughs (C2 and C5 respectively), cough frequency objectively measured using an ambulatory cough meter, and parent and child recorded subjective cough scores were determined in 40 children with recurrent cough on two occasions. RESULTS: On occasion one, log cough frequency significantly correlated with parent and child recorded log cough score (r(s) = 0.32, p = 0.05; and r(s) = 0.32, p = 0.046 respectively) and significantly negatively correlated with log C2 (r(s)= -0.5, p = 0.005). Subjective cough scores did not relate to either C2 or C5. On occasion two, the relation between cough frequency and C2 and C5 measures was lost, but C2 had a weak but significant relation to parent recorded cough score (r(s) = -0.38, p = 0.047). When the changes in the log values were determined, C5 but not C2 significantly related to cough frequency. CONCLUSION: In children, measures of cough sensitivity have a weak relation with cough frequency. Subjective cough scores have a stronger and consistent relation with cough frequency. These cough severity indices measure different aspects of cough. The choice of indices depends on the reason for performing the measurement.
BACKGROUND: Patients who complain of a persistent cough lasting >3 weeks after experiencing the acute symptoms of an upper respiratory tract infection may have a postinfectious cough. Such patients are considered to have a subacute cough because the condition lasts for no >8 weeks. The chest radiograph findings are normal, thus ruling out pneumonia, and the cough eventually resolves, usually on its own. The purpose of this review is to present the evidence for the diagnosis and treatment of postinfectious cough, including the most virulent form caused by Bordetella pertussis infection, and make recommendations that will be useful for clinical practice. METHODS: Recommendations for this section of the guideline were obtained from data using a National Library of Medicine (PubMed) search dating back to 1950, which was performed in August 2004, of the literature published in the English language. The search was limited to human studies, using the search terms "cough," "postinfectious cough," "postviral cough," "Bordetella pertussis," "pertussis infection," and "whooping cough." RESULTS: The pathogenesis of the postinfectious cough is not known, but it is thought to be due to the extensive inflammation and disruption of upper and/or lower airway epithelial integrity. When postinfectious cough emanates from the lower airway, this is often associated with the accumulation of an excessive amount of mucus hypersecretion and/or transient airway and cough receptor hyperresponsiveness; all may contribute to the subacute cough. In these patients, the optimal treatment is not known. Except for bacterial sinusitis or early on in a B pertussis infection, therapy with antibiotics has no role, as the cause is not bacterial infection. The use of inhaled ipratropium may be helpful. Other causes of postinfectious cough are persistent inflammation of the nose and paranasal sinuses, which leads to an upper airway cough syndrome (previously referred to as postnasal drip syndrome), and gastroesophageal reflux disease, which may be a complication of the vigorous coughing. One type of postinfectious cough that is particularly virulent is that caused by B pertussis infection. When the cough is accompanied by paroxysms of coughing, posttussive vomiting, and/or an inspiratory whooping sound, the diagnosis of a B pertussis infection should be made unless another diagnosis is proven. This infection is highly contagious but responds to antibiotic coverage with an oral macrolide when administered early in the course of the disease. A safe and effective vaccine to prevent B pertussis is now available for adults as well as children. It is recommended according to CDC guidelines. CONCLUSIONS: In patients who have a cough lasting from 3 to 8 weeks with normal chest radiograph findings, consider the diagnosis of postinfectious cough. In most patients, a specific etiologic agent will not be identified, and empiric therapy may be helpful. A high degree of suspicion for cough due to B pertussis infection will lead to earlier diagnosis, patient isolation, and antibiotic treatment.
OBJECTIVES: To review relevant literature and present evidence-based guidelines to assist general and specialist medical practitioners in the evaluation and management of children who present with chronic cough. METHODOLOGY: The Cochrane, MEDLINE, and EMBASE databases, review articles, and reference lists of relevant articles were searched and reviewed by a single author. The date of the last comprehensive search was December 5, 2003, and that of the Cochrane database was November 7, 2004. The authors' own databases and expertise identified additional articles. RESULTS/CONCLUSIONS: Pediatric chronic cough (ie, cough in children aged <15 years) is defined as a daily cough lasting for >4 weeks. This time frame was chosen based on the natural history of URTIs in children and differs from the definition of chronic cough in adults. In this guideline, only chronic cough will be discussed. Chronic cough is subdivided into specific cough (ie, cough associated with other symptoms and signs suggestive of an associated or underlying problem) and nonspecific cough (ie, dry cough in the absence of an identifiable respiratory disease of known etiology). The majority of this section focuses on nonspecific cough, as specific cough encompasses the entire spectrum of pediatric pulmonology. A review of the literature revealed few randomized controlled trials for treatment of nonspecific cough. Management guidelines are summarized in two pathways. Recommendations are derived from a systematic review of the literature and were integrated with expert opinion. They are a general guideline only, do not substitute for sound clinical judgment, and are not intended to be used as a protocol for the management of all children with a coughing illness. Children (aged <15 years) with cough should be managed according to child-specific guidelines, which differ from those for adults as the etiologic factors and treatments for children are sometimes different from those for adults. Cough in children should be treated based on etiology, and there is no evidence for using medications for the symptomatic relief of cough. If medications are used, it is imperative that the children are followed up and therapy with the medications stopped if there is no effect on the cough within an expected time frame. An evaluation of the time to response is important. Irrespective of diagnosis, environmental influences and parental expectations should be discussed and managed accordingly. Cough often impacts the quality of life of both children and parents, and the exploration of parental expectations and fears is often valuable in the management of cough in children.
Increased cough frequency is a common symptom associated with infective pulmonary exacerbations of cystic fibrosis (CF), but subjective assessment of cough is very unreliable. The aims of this study were: 1) to validate a modification of our previously described ambulatory cough recording device (LR 100); 2) to determine how accurately children with CF assess levels of cough; and 3) to assess the change in cough in children with CF when treated with intravenous antibiotics for a respiratory exacerbation, and whether the children themselves were able accurately to perceive any change. Fourteen CF children (aged 13.6 +/- 2.6 years) were included in the study. All 14 children were simultaneously recorded with the LR 100 cough recorder and a conventional tape recorder during a chest physiotherapy session on the first or second day of admission for an infective exacerbation diagnosed by standard criteria. The difference between the two was an underestimate of 0.5 epoch/session by the tape recorder. Ten children were recorded on admission with the LR 100 cough recorder for a complete cycle (17 hr and 40 min), and we also assessed their day and night-time cough with cough scores and visual analogue scores (VAS). In 8 of these children, the same assessments were repeated on discharge. There was no significant correlation between any of the admission or discharge cough scores, daytime or night-time cough scores, and daytime or night-time VAS scores, with the actual number of coughs recorded on the LR 100 cough recorder. For the 8 children who had cough monitoring on admission and on discharge, there was no significant improvement in daytime or night-time cough scores or VAS on discharge, despite significant improvements in spirometry. There was also no significant improvement on daytime and night-time cough counts with the cough monitor on discharge, and no significant correlation with changes in lung function. There were weak correlations only between change in daytime VAS scores and change in forced expired volume in 1 sec (r = -0.794, P = 0.019) and forced vital capacity (r = -0.723, P = 0.04). In conclusion, we describe a reliable and well-tolerated method for obtaining cough counts objectively. The use of this objective method showed that CF children did not assess their cough frequency well. In addition, treatment of respiratory exacerbation improved neither subjective nor objective measures of cough in CF children.