Nocturnal cough in asthma

Cough frequency in children with mild asthma correlates with sputum neutrophil count

BACKGROUND

A study was undertaken to measure cough frequency in children with stable asthma using a validated monitoring device, and to assess the correlation between cough frequency and the degree and type of airway inflammation.

METHODS

Thirty six children of median age 11.5 years (interquartile range (IQR) 9-14) with stable asthma were recruited. They underwent spirometric testing, exhaled nitric oxide (eNO) measurement, sputum induction for differential cell count, and ambulatory cough monitoring for 24 hours. Coughing episodes were counted both as individual spikes and as clusters.

RESULTS

All children had mild intermittent asthma and their median forced expiratory volume in 1 second and eNO were 83.3% (IQR 81.1-97.6) and 56.1 ppb (IQR 37.4-105), respectively. The median number of cough episodes per day was 25.5 (IQR 16-42.8). Sputum induction was successful in 69% of the subjects and cough frequency was found to have a significant positive correlation with sputum neutrophil count (r = 0.833, p = 0.0001).

CONCLUSIONS

Children with stable mild asthma have increased cough frequency that might be driven by a neutrophilic inflammatory pathway.

Comparison of objective and subjective measurements of cough frequency in patients with seasonal allergic rhinitis

BACKGROUND

Cough is a frequent complaint of patients with a variety of respiratory disorders, including seasonal allergic rhinitis (SAR), and it is often evaluated subjectively to determine disease status and response to treatment. However, it is not known whether subjective reports of cough from patients with SAR are accurate.

OBJECTIVE

To compare a novel objective measurement with subjective reports of cough frequency in a subset of 28 patients (aged > or = 12 years) with active SAR who were enrolled in a large, multicenter trial examining the efficacy of an active treatment for SAR.

METHODS

In this supplemental pilot study, subjective data were collected on a diary card and objective data were collected using home-based telemetry. Three 24-hour recording sessions were conducted with each patient: 2 consecutive baseline sessions (day 1 and day 2) and 1 session after randomization to placebo or active cough treatment (day 3).

RESULTS

Strong correlations existed between cough frequency data for days 1 and 2 (Spearman correlation coefficient = 0.91; P < .001) and between subjective and objective data for days 1, 2, and 3 (daytime greater than nighttime) (Spearman correlation coefficient = 0.51; P < .001).

CONCLUSION

These results have implications for the design and interpretation of results from clinical trials that evaluate cough frequency as a treatment outcome.

Cough frequency in children with stable asthma: correlation with lung function, exhaled nitric oxide, and sputum eosinophil count

BACKGROUND

A study was undertaken to assess the correlation between cough frequency in asthmatic children with lung function and two non-invasive markers of airway inflammation.

METHODS

Thirty two children of median age 12.0 years (interquartile range (IQR) 9.5-13.4) with stable asthma were recruited. They underwent spirometric testing, exhaled nitric oxide (eNO) measurement, sputum induction for differential cell count, and ambulatory cough monitoring over 17 hours and 40 minutes. Coughing episodes were counted both as individual spikes and as clusters.

RESULTS

Complete cough frequency data were available in 29 children (90%) and their median forced expiratory volume in 1 second (FEV1) and eNO were 88.5% (IQR 79.5-98) and 23.9 ppb (IQR 11.4-41.5), respectively. The median number of cough episodes was 14 (IQR 7.0-24.0) which was significantly higher than that of normal children (6.7 (IQR 4.1-10.5), p<0.001). Sputum induction was successful in 61% of the subjects; the median induced sputum eosinophil count was 0.05% (IQR 0-9.0). Cough frequency was found to have a significant positive correlation with eNO (Spearman's r =0.781, p<0.001) but not with FEV1 or sputum eosinophil count (r =-0.270, p=0.157; r =0.173, p=0.508, respectively).

CONCLUSIONS

Children with stable asthma have increased cough frequency compared with normal controls and cough frequency was greater during the day than at night. Cough may be a more sensitive marker of airway inflammation than simple spirometry.

[Chronic cough, asthma and allergy]

The medical approach of chronic cough suffers from the lack of a standardised definition. The most frequently encountered criterion is a recurrent cough observed during several consecutive months, each episode lasting at least 1 week. The link between recurrent cough and asthma is still discussed. Cough-related asthma diagnosis is facilitated when wheezing is clearly confirmed, or may be reminded by a nonproductive middle night cough, or an exercise-triggered cough, or the presence of personal or familial atopy. Conversely, an early morning and productive cough associated with tobacco exposure do not suggest asthma.

A review of cough in children

Cough is a very common symptom of respiratory disease and reason for parents to seek medical attention. The article presents broad clinical guidelines on the approach to childhood cough and discusses current controversies of the management of cough in children.

Cough as the ambiguous indicator of airway obstruction in asthma

This study tested the hypothesis that cough frequency during induced airway obstruction in children and adolescents with asthma relates significantly to other symptoms. The second hypothesis was that cough during remission may often be a conditioned or voluntary response. In experiment 1, tracheal sounds were recorded from 30 participants with asthma during a histamine challenge test. In experiment 2, tracheal sounds were recorded from 30 participants with and 30 without asthma during a standardized physical exercise task. Cough and respiratory wheeze were assessed from the sound records by two examiners independently. The results showed that cough during airway obstruction did not relate to other variables. Only the second hypothesis was supported. In both experiments the frequency of cough was independent of lung function (forced expiratory volume in 1 sec [FEV1]), wheezing, dyspnea, and severity of asthma. The percentage of participants with asthma who coughed in experiment 1 increased from 21% (baseline) to 71% after histamine inhalation. During experiment 2, the cough percentage increased from 52% to 69% in asthmatics, and from zero to 57% in controls. It was concluded that cough in asthma is not diagnostically useful for assessment of airway obstruction. Excessive baseline cough among asthmatics could be the result of acquired responses to anticipated exercise-induced symptoms.

Prescribing for persistent cough in children

To identify the medications general practitioners consider for the treatment of persistent isolated cough, we undertook a postal questionnaire survey of a sample of general practitioners in east London. Fewer than 10% indicated that they never prescribed for such cough. About 70% sometimes considered antibiotics and/or bronchodilators in all age groups. Inhaled steroids and cromoglycate were considered by about 30% of prescribers for infants compared with over 60% for older age groups. As yet there is no evidence that medication is beneficial for persistent isolated cough. The role of asthma drugs for children with this symptom needs to be evaluated so that we can better identify those who are likely to benefit.

Diagnostics of spontaneous cough in childhood asthma: results of continuous tracheal sound recording in the homes of children

Spontaneous cough is a symptom with diffuse diagnostic significance for childhood asthma. Information on the interrelations between presence/frequency of cough and other symptoms of asthma are not available to the physician. Tracheal sounds were continuously recorded in the homes of 60 children with and 30 without asthma, at 72 and 24 h, respectively. Presence and frequency of cough and presence of wheeze were scored by trained examiners. Wheeze was used to indicate airway obstruction during hours when peak expiratory flow (PEF) values were not available. PEF and self-reported dyspnea were assessed every 4 h. Results showed that asthmatics coughed significantly more often than control subjects during exacerbations, but not during remission. The highest diagnostic sensitivity percentages of cough were 72% for wheeze and 69% for a reduction in PEF > 20%. However, the diagnostic specificity was poor, 41% for wheeze and 34% for a reduction in PEF > 20%. Cough and dyspnea were independent. Three children did not cough during exacerbations. Persistent, isolated cough was observed in two children. It was concluded that spontaneous cough is modestly predictive of asthmatic exacerbations, but not of a diagnosis of asthma or severity of asthma.

Chronic night cough and asthma severity in children with stable asthma

The relationship between night cough and other indices of asthma severity was studied in 21 children with clinically stable asthma and persistent night cough. Overnight cough was quantified and related to symptom scores, oxygen saturation (SaO2) during sleep, evening and morning peak flow recordings and daytime tests of lung function. In the index group the median number of coughing episodes was 23 (range 1-158). Only 4 children had counts of < 10 overnight, similar to the comparison group of 12 children all of whom had counts of < 10. There was a trend towards the association of overnight cough with reduced evening peak flow (r = -0.407, P = 0.07) and reduced SaO2 (r = -0.36, P = 0.10). Abnormalities in daytime tests of lung function were observed in 13 children. There was no relationship between night cough and daytime indices of lung function abnormality although children with more severe daytime abnormalities also had significant night cough. Conversely, five children with chronic night cough had normal daytime function. Conclusion. Night-time cough in children with asthma is not simply a reflection of daytime lung function status, whereas, overnight SaO2 correlates well. Other factors need to be explored to explain the variability of night-time cough in these children.

A new device for ambulatory cough recording

Nocturnal cough reporting on diary cards has been shown to be unreliable and inconsistent. Whether subjective reporting of daytime cough is equally unreliable remains unknown. We have, therefore, developed a new and easily portable device (RBC-7) that records electromyographic (EMG) and audio cough signals for at least a 24-hr period, with a capacity of over 48 hr. Additional information is obtained from electrocardiographic (ECG) signals, and from an accelerometer indicating the level of the subject's activity. The RBC-7 can be set up with the aid of a notebook computer at the subjects home, school or workplace. Initial studies utilizing a prototype device were performed to determine the optimal position of the EMG leads and the microphone. The optimal position for the EMG leads was determined as the positive electrode in the sixth intercostal space (ICS) in the midclavicular line on the left, the negative electrode in the same position on the right, and the reference electrode in the midline over the abdomen. This position was shown to give the highest EMG voltages and the greatest difference in voltages between cough and other signals. The optimal microphone position for signal strength and comfort was over the first ICS, either right or left, close to the sternum. Recordings were performed simultaneously in 20 subjects with conventional tape recorders and the multiparametric cough monitoring system (RBC-7). Conventional tape recordings limited the duration of the studies due to the inherent restrictions. No significant difference in the number of single coughs recorded by each system was detected (correlation coefficient = 0.996). The RBC-7 offers a unique opportunity to obtain objective information on cough in ambulatory subjects over at least a 24-hr period, and to relate cough to time, activity and heart rate, while normal activities are pursued.

Effect of controlled release salbutamol on nocturnal cough in asthma

Sixteen asthmatic children completed a double blind placebo controlled crossover study of controlled release salbutamol (CRS) to assess its efficacy in controlling night time cough. Children with asthma were enrolled into the study on the basis of a history of persistent cough confirmed by two overnight tape recordings at home. Outcome was measured by two overnight tapes on each medication. Other treatment was unaffected. There was no significant fall in cough counts on CRS. Median scores were 14.5 and 12.0 coughing episodes per night for CRS and placebo respectively. Mean overnight oxygen saturation was identical in both treatment periods but morning peak flow showed a trend towards improvement on CRS. Treatment with CRS does not have a significant effect in control of night cough although it may improve objective measurements of lung function.

Asthma severity at night during recovery from an acute asthmatic attack

This study was undertaken to investigate the severity of night time asthma in children in hospital recovering from an acute attack of asthma. Twenty two children aged 5-14 years were studied. Coughing 'epochs' overnight varied from one to 156 (median 39.5) and mean overnight arterial oxygen saturation (Sao2) from 82 to 98% (mean 91.3). Log values for cough showed a correlation with Sao2. An Sao2 of less than 90% was invariably associated with coughing but Sao2 above 95% did not preclude cough. Peak flow measured in the morning or evening correlated with Sao2 but not with log cough, and clinical examination scores showed no correlation with overnight measurements. Night time Sao2 correlated better with daytime tests of lung function than log cough. In general, night time indices of severity reflected daytime pulmonary function status but night cough was sometimes prominent in less severely affected cases. At the time of discharge, clinical indices of severity underestimated the degree of functional impairment at night.