Effect of chest wall vibration timing on peak expiratory flow and inspiratory pressure in a mechanically ventilated lung model.

OBJECTIVE: To investigate the effects of chest wall vibration timing on air flow and pressure in a ventilated lung model. DESIGN: Laboratory-based bench study. PARTICIPANTS: Thirty physiotherapists with experience in intensive care. INTERVENTION: Physiotherapists applied three sets of eight chest wall vibrations to an intubated, mechanically ventilated mannequin. Vibrations were applied at the start of expiration (optimal), mid to late inspiration (early) and early to mid expiration (late). Air flow, peak pressure and volume were measured continuously. Forces applied during vibrations were recorded using a force-sensing mat, placed under the physiotherapists' hands. RESULTS: During optimal and early vibrations, peak expiratory flow increased significantly compared with baseline ventilation [mean difference for optimal vibrations 8.8l/minute, 95% confidence interval (CI) 6.0 to 11.6; mean difference for early vibrations 7.0l/minute, 95% CI 4.3 to 9.9]. Late vibrations did not enhance expiratory flow. Peak inspiratory pressure was significantly higher during early vibrations compared with baseline values (mean difference 5.6cmH(2)O, 95% CI 2.9 to 8.2). Peak inspiratory pressure generated during early vibrations was, on average, 8.4cmH(2)O greater than with optimal timing. CONCLUSION: The safety and effectiveness of respiratory physiotherapy treatments are likely to be influenced by the timing of vibrations within the breath cycle. Early vibrations generate potentially dangerous peak inspiratory pressures. Late vibrations, although not harmful, are not effective at increasing peak expiratory flow. This is an important consideration when training physiotherapists and evaluating outcomes of treatments in intensive care.

Simultaneous measurement of force and respiratory profiles during chest physiotherapy in ventilated children.

There are currently no objective means of quantifying chest wall vibrations during manual physiotherapy. The aims of the study were to (i) develop a method to quantify physiotherapy-applied forces and simultaneous changes in respiratory flow and pressure, (ii) assess the feasibility of using this method in ventilated children and (iii) characterize treatment profiles delivered by physiotherapists in the paediatric intensive care unit. Customized sensing mats were designed and used in combination with a respiratory profile monitor. Software was developed to align force and flow data streams. Force and respiratory data were successfully collected in 55 children (median age 1.6 years (range 0.02-13.7 years)). Physiotherapists demonstrated distinctive variations in the pattern of force applied and manual lung inflations. The maximum applied force ranged from 15 to 172 N, and was correlated with the child's age (r = 0.76). Peak expiratory flow increased significantly during manual inflations both with and without chest wall vibrations (p < 0.05). This method provides the basis for objective assessments of the direct and independent effects of vibration forces and manual lung inflations as an essential precursor to developing evidence-based practice.

Systemic effects of inhaled corticosteroids on growth and bone turnover in childhood asthma: a comparison of fluticasone with beclomethasone.

Inhaled steroids are frequently used in childhood asthma, but concerns based on limited objective evidence remain, regarding long-term side-effects. In this study the systemic effects of standard doses of inhaled steroids in childhood asthma were assessed, comparing beclomethasone dipropionate (BDP) with fluticasone propionate (FP). The study was prospective, randomized and double-blind. Twenty-three steroid-naive children with moderately severe asthma, aged 5-10 yrs, were allocated either BDP (400 microg x day(-1) or FP (200 microg x day(-1)) using a metered-dose inhaler with a spacer. Asthma control was assessed at regular intervals over 20 months. Fasting morning blood and overnight urine samples were collected for estimation of serum cortisol, serum 1-carboxyterminal telopeptide (ICTP), serum osteocalcin and urine deoxypyridinoline (DPD). Bone mineral density (BMD) was measured at each visit. None of the markers of bone turnover showed any change during the study period. BMD increased at normal rates with age. Serum cortisol significantly decreased on BDP, but not on FP. A significant difference in growth rates was found between the groups, with a slower rate of growth towards the end of the observation period in the BDP group. In conclusion when taken in a relatively modest dose over a period of time, beclomethasone dipropionate had significant effects on the hypothalamic-pituitary-adrenal axis and statural growth in childhood asthma. These systemic effects were not seen with an equipotent dose of fluticasone propionate.

Effect of inhaled corticosteroids on bone mineral density in childhood asthma: comparison of fluticasone propionate with beclomethasone dipropionate.

There is a dearth of data on long-term effects of inhaled corticosteroids (ICS) on bone architecture in childhood asthma. This study was designed to assess the possible effects of two different inhaled steroids on bone mineral density (BMD) in steroid-naïve, prepubertal children. Twenty-three children were randomized to receive equipotent doses of either fluticasone propionate (100 micrograms twice daily) or beclomethasone dipropionate (200 micrograms twice daily). They were followed up over a period of 20 months with regular dual-energy X-ray absorptiometry scans for BMD. Densitometry of lumbar spine and total body showed a significant increase over time, which followed the normal patterns for growth. No difference was observed between the two subgroups. There was no change in fat distribution over time and no increase in percentage total body fat. As expected, girls had significantly higher total body fat. This absence of deleterious effects suggests that in the standard doses used neither beclomethasone nor fluticasone has any significant effect on bone density over a moderate period of time. Further studies should continue monitoring BMD through the critical years of bone mass accumulation during adolescence.

Airway function correlates with circulating eosinophil, but not mast cell, markers of inflammation in childhood asthma.

BACKGROUND: Lung function tests, including forced expiratory volume in one second (FEV1), forced expiratory flow at 25-75% of vital capacity (FEF25-75%) and provocation concentrations of histamine which reduce FEV1 by 20% (PC20), are used as indicators of airway form and function in bronchial asthma. Recently, markers of eosinophil activation in bronchial lavage and serum have been suggested as a measure of eosinophil mediated inflammation in the airways. These include eosinophil cationic protein (ECP), eosinophil protein X (EPX) (also known as eosinophil derived neurotoxin) and eosinophil peroxidase (EPO). Similarly, serum tryptase has been used as a marker of mast cell activation in systemic anaphylaxis. OBJECTIVES: We measured both sets of indices in a group of children with moderately severe asthma to assess the contribution of eosinophil and mast cell mediated events to airflow limitation and bronchial hyperresponsiveness. METHODS: Forty-eight children aged 5-10 years had spirometric assessments, histamine challenges and blood sampling on the same occasion. After analysis of sera, the indices were compared. RESULTS: The eosinophil markers ECP and EPX correlated very well with each other. They showed a moderate negative correlation with PC20 for histamine. EPX was also found to negatively correlate with FEV1 and FEF25-75%. Serum tryptase levels showed no such correlates with airway function. CONCLUSION: These results suggest that serum markers of eosinophil activation correlate with airway function in childhood asthma, and may be of value in assessing the severity of the disease. It further supports the notion that childhood asthma has a similar immunopathology to that occurring in adults, with predominance of eosinophil mediated inflammation.

Assessment of the continued supervision and asthma management knowledge of patients possessing home nebulizers.

This paper describes the results of a questionnaire survey on some aspects of nebulizer use, nebulizer instruction, and features relating to the recognition and management of deteriorating asthma. The study population consisted of 90 children with home nebulizers attending a paediatric asthma clinic, and 200 asthmatic children and 200 asthmatic adults whose nebulizers had been purchased directly from a manufacturer in the U.K. The results suggest that follow-up supervision of the patients who bought their own nebulizers occurred in only approximately 25% of cases. Written information focusing on the management of symptoms was also lacking. Peak flow meters were being under-used. Although the majority (77-100%) of patients were aware of the '4 h rule' for repeat use of bronchodilator therapy at home, there was still some confusion about the acceptable time interval and action to be taken should the dose be required more frequently. Very few (32%) in the nationwide adult group had a crisis action plan should the nebulizer fail to produce relief. This paper recommends that a simple treatment and crisis plan should be included with the purchased nebulizer, highlighting the key areas to be discussed by the patients with the doctor or other medical professionals. Such a package may prevent the occasional disaster that can occur with unsupervised nebulized bronchodilator usage.

Increased resting energy expenditure in childhood asthma: does this contribute towards growth failure?

In order to determine whether or not there was a relationship between disorders of growth in children suffering from asthma and either increased resting energy expenditure or inadequate energy intake, a group of 34 children suffering from perennial symptoms were studied. A control group matched with the asthmatic children for sex and fat free mass were similarly studied. The children kept seven day records of weighed food intake. Basal metabolic rate was measured on one occasion in the fasted state by means of indirect calorimetry using the ventilated hood technique. The asthmatic children kept a 28 day record of peak expiratory flow rates, asthma symptoms, and medication usage. The asthmatic children expended significantly more energy at rest than their matched controls in absolute terms (14%). There was no correlation between height or height SD score and any parameter of energy balance. The causes of these finding are as yet speculative.