An objective study of acid reflux and cough in children using an ambulatory pHmetry-cough logger

OBJECTIVE

There are no objective ambulatory studies on the temporal relationship between reflux and cough in children. Commercial pHmetry loggers have slow capture rates (0.25 Hz) that limit objective quantification of reflux and cough. The authors aimed to evaluate if there is a temporal association between cough and acid pH in ambulatory children with chronic cough.

DESIGN, SETTING AND PATIENTS

The authors studied children (aged <14 years) with chronic cough, suspected of acid reflux and considered for pHmetry using a specifically built ambulatory pHmetry-cough logger that enabled the simultaneous ambulatory recording of cough and pH with a fast (10 Hz) capture rate.

MAIN OUTCOME MEASURES

Coughs within (before and after) 10, 30, 60 and 120 s of a reflux episode (pH<4 for >0.5 s).

RESULTS

Analysis of 5628 coughs in 20 children. Most coughs (83.9%) were independent of a reflux event. Cough-reflux (median 19, IQR 3-45) and reflux-cough (24.5, 13-51) sequences were equally likely to occur within 120 s. Within the 10 and 30 s time frame, reflux-cough (10 s=median 2.5, IQR 0-7.25; 30 s=6.5, 1.25-22.25) sequences were significantly less frequent than reflux-no cough (10 s=27, IQR 15-65; 30 s=24.5, 14.5-55.5) sequences, (p=0.0001 and p=0.001, respectively). No differences were found for 60 and 120 s time frame. Cough-reflux sequence (median 1.0, IQR 0-8) within 10 s was significantly less (p=0.0001) than no cough-reflux sequences (median 29.5, 15-67), within 30 s (p=0.006) and 60 s (p=0.048) but not within 120 s (p=0.47).

CONCLUSIONS

In children with chronic cough and suspected of having gastro-oesophageal reflux disease, the temporal relationship between acid reflux and cough is unlikely causal.

A new method for objective identification and measurement of airway lumen in paediatric flexible videobronchoscopy

BACKGROUND

Accurate measurements of airway and lesion dimensions are important to the developmental progress of paediatric bronchoscopy. The malacia disorders are an important cause of respiratory morbidity in children, but no methods are currently available to measure these lesions or the airway lumen accurately. A new measurement technique is described here.

METHODS

The magnification power of a paediatric videobronchoscope was defined and a simple and user friendly computer based program (Image J) was used to develop an objective technique (colour histogram mode technique, CHMT) for measurement of the airway lumen.

RESULTS

In vivo intra-observer and inter-observer repeatability coefficients for repeated area measurements from 28 images using the Bland-Altman method were 0.9 mm2 and 1.6 mm2, respectively. The average intraclass correlation coefficient for repeated measurements of area was 0.93. In vitro validation measurements using a 2 mm diameter tube resolved radii measurements to within 0.1 mm (coefficient of variability 8%). An "acceptable result" was defined in 92% of 734 images completed with the CHMT alone and 8% with its modification. The success rate for two of three images being within 10% of each other's area was 100%. Measurements of cricoid cross sectional areas from 116 patients compared with expected airway areas for age derived from endotracheal tube sizes were comparable.

CONCLUSIONS

The CHMT method of identifying and measuring airway dimensions is objective, accurate, and versatile and, as such, is important to the future development of flexible videobronchoscopy.

Quantification of the magnification and distortion effects of a pediatric flexible video-bronchoscope

BACKGROUND

Flexible video bronchoscopes, in particular the Olympus BF Type 3C160, are commonly used in pediatric respiratory medicine. There is no data on the magnification and distortion effects of these bronchoscopes yet important clinical decisions are made from the images. The aim of this study was to systematically describe the magnification and distortion of flexible bronchoscope images taken at various distances from the object.

METHODS

Using images of known objects and processing these by digital video and computer programs both magnification and distortion scales were derived.

RESULTS

Magnification changes as a linear function between 100 mm (x1) and 10 mm (x9.55) and then as an exponential function between 10 mm and 3 mm (x40) from the object. Magnification depends on the axis of orientation of the object to the optic axis or geometrical axis of the bronchoscope. Magnification also varies across the field of view with the central magnification being 39% greater than at the periphery of the field of view at 15 mm from the object. However, in the paediatric situation the diameter of the orifices is usually less than 10 mm and thus this limits the exposure to these peripheral limits of magnification reduction. Intraclass correlations for measurements and repeatability studies between instruments are very high, r = 0.96. Distortion occurs as both barrel and geometric types but both types are heterogeneous across the field of view. Distortion of geometric type ranges up to 30% at 3 mm from the object but may be as low as 5% depending on the position of the object in relation to the optic axis.

CONCLUSION

We conclude that the optimal working distance range is between 40 and 10 mm from the object. However the clinician should be cognisant of both variations in magnification and distortion in clinical judgements.

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.