On the equivalence of the X-ray scattering retrieval with beam tracking and analyser-based imaging using a synchrotron source

X-ray phase contrast imaging (XPCI) methods give access to contrast mechanisms that are based on the refractive properties of matter on top of the absorption coefficient in conventional x-ray imaging. Ultra small angle x-ray scattering (USAXS) is a phase contrast mechanism that arises due to multiple refraction events caused by physical features of a scale below the physical resolution of the used imaging system. USAXS contrast can therefore give insight into subresolution structural information, which is an ongoing research topic in the vast field of different XPCI techniques. In this study, we quantitatively compare the USAXS signal retrieved by the beam tracking XPCI technique with the gold standard of the analyzer based imaging XPCI technique using a synchrotron x-ray source. We find that, provided certain conditions are met, the two methods measure the same quantity.

Puzzled by dysfunctional breathing disorder(s)? Consider the Bayesian brain hypothesis!

There is currently growing clinical concern regarding dysfunctional breathing disorder(s) (DBD), an umbrella term for a set of multidimensional clinical conditions that are characterized by altered breathing pattern associated with a variety of intermittent or chronic symptoms, notably dyspnea, in the absence or in excess of, organic disease. However, several aspects of DBD remain poorly understood and/or open to debate, especially the inconsistent relationship between the array of experienced symptoms and their supposedly underlying mechanisms. This may be partly due to a more general problem, i.e., the prevailing way we conceptualize symptoms. In the present article, after a brief review of the different aspects of DBD from the current perspective, I submit a call for considering DBD under the innovating perspective of the Bayesian brain hypothesis, i.e., a potent and novel model that fundamentally changes our views on symptom perception.

A decrease in plant gain, namely CO2 stores, characterizes dysfunctional breathing whatever its subtype in children

Background: Whether dysfunctional breathing (DB) subtype classification is useful remains undetermined. The hyperventilation provocation test (HVPT) is used to diagnose DB. This test begins with a 3-min phase of hyperventilation during which fractional end-tidal CO₂ (FETCO₂) decreases that could be an assessment of plant gain, which relies on CO₂ stores. Our aim was to assess 1) whether the children suffering from different subtypes of DB exhibit decreased plant gain and 2) the relationships between HVPT characteristics and plant gain. Methods: We retrospectively selected 48 children (median age 13.5 years, 36 females, 12 males) who exhibited during a cardiopulmonary exercise test either alveolar hyperventilation (transcutaneous PCO₂ < 30 mmHg, n = 6) or inappropriate hyperventilation (increased VE'/V'CO₂ slope) without hypocapnia (n = 18) or dyspnea without hyperventilation (n = 18) compared to children exhibiting physiological breathlessness (dyspnea for sports only, n = 6). These children underwent tidal-breathing recording (ventilation and FETCO₂ allowing the calculation of plant gain) and a HVPT. Results: The plant gain was significantly higher in the physiological group as compared to the dyspnea without hyperventilation group, p = 0.024 and hyperventilation without hypocapnia group, p = 0.008 (trend for the hyperventilation with hypocapnia group, p = 0.078). The slope of linear decrease in FETCO₂ during hyperventilation was significantly more negative in physiological breathlessness group as compared to hyperventilation without hypocapnia group (p = 0.005) and dyspnea without hyperventilation group (p = 0.049). Conclusion: The children with DB, regardless of their subtype, deplete their CO₂ stores (decreased plant gain), which may be due to intermittent alveolar hyperventilation, suggesting the futility of our subtype classification.

Diagnostic tests and subtypes of dysfunctional breathing in children with unexplained exertional dyspnea

BACKGROUND

Inappropriate hyperventilation during exercise may be a specific subtype of dysfunctional breathing (DB).

OBJECTIVE

To assess whether Nijmegen questionnaire and hyperventilation provocation test (HVPT) are able to differentiate inappropriate hyperventilation from other DB subtypes in children with unexplained exertional dyspnea, and normal spirometry and echocardiography.

METHODS

The results were compared between a subgroup of 25 children with inappropriate hyperventilation (increased V'E/V'CO₂ slope during a cardiopulmonary exercise test (CPET)) and an age and sex matched subgroup of 25 children with DB without hyperventilation (median age, 13.5 years; 36 girls). Anxiety was evaluated using State-Trait Anxiety Inventory for Children questionnaire.

RESULTS

All children were normocapnic (at rest and peak exercise) and the children with hyperventilation had lower tidal volume/vital capacity on peak exercise (shallow breathing). The Nijmegen score correlated positively with dyspnea during the CPET and the HVPT (p = 0.001 and 0.010, respectively) and with anxiety score (p = 0.022). The proportion of children with a positive Nijmegen score (≥19) did not differ between hyperventilation (13/25) and no hyperventilation (14/25) groups (p = 0.777). Fractional end-tidal CO₂ (FETCO₂ ) at 5-min recovery of the HVPT was < 90% baseline in all children (25/25) of both subgroups. Likewise, there was no significant difference between the two subgroups for other indices of HVPT (FETCO₂ at 3-min recovery and symptoms during the test).

CONCLUSION

The validity of the Nijmegen questionnaire and the HVPT to discriminate specific subtypes of dysfunctional breathing, as well as the relevance of the inappropriate hyperventilation subtype itself may both be questioned.

Salbutamol Worsens the Autonomic Nervous System Dysfunction of Children With Sickle Cell Disease

Background

Sickle cell disease (SCD) patients with asthma have an increased rate of vaso-occlusive crisis (VOC) and acute chest syndrome (ACS) episodes when compared to those without asthma. We hypothesized that either asthma diagnosis or bronchodilator treatment might aggravate SCD via their modulating effect on the autonomic nervous system (ANS).

Methods

Cross-sectional evaluation of heart rate variability (HRV) during pulmonary function tests, including salbutamol administration, in children with SCD receiving asthma treatment or not when compared to asthmatic children without SCD matched for ethnicity.

Results

SCD children with asthma (n = 30, median age of 12.9 years old) were characterized by a reduced FEV₁/FVC ratio, an increased bronchodilator response, and a greater incidence of VOC and ACS when compared to SCD children without asthma (n = 30, 12.7 years). Children with asthma without SCD (n = 29, 11.4 years) were characterized by a higher exhaled NO fraction than SCD children. SCD children when compared to non-SCD children showed reduced HRV [total power, low (LF) and high (HF, vagal tone) frequencies], which was further worsened by salbutamol administration in all the groups: reduction in total power and HF with an increase in LF/HF ratio. After salbutamol, the LF/HF ratio of the SCD children was higher than that of the non-SCD children. The two groups of SCD children were similar, suggesting that asthma diagnosis per se did not modify ANS functions.

Conclusion

SCD children are characterized by impaired parasympathetic control and sympathetic overactivity that is worsened by salbutamol administration.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT04062409.

Cross-sectional phenotyping of small airway dysfunction in preschool asthma using the impulse oscillometry system

Objective. Asthma is a chronic inflammatory airway disorder known to induce small airways dysfunction (SAD). It is important to develop tools to assess the presence and extent of SAD in daily clinical practice. An Impulse Oscillometry System (IOS) might detect SAD, but the validity of the underlying model (serial Resistive airway and Compliant tissue model: RC model) in diseased lungs remains questionable.Methods. Our objective was to evaluate the usefulness of parameters obtained from six electrical circuit models that were fitted to the measurements of impedance obtained with IOS in asthmatic children characterized by an abnormal lung function defined by an increased baseline interrupter resistance (Rint, z-score > +1.645).Results. The six models were tested in 102 asthmatic children (median age: 5.5 years). Two models allowed the description of 92/102 (90%) children: 74 by the extended RIC model (central and peripheral Resistance, Inertance and peripheral airway Compliance) and 18 by the Mead₁₉₆₉ model (extended RIC plus lung compliance). Thus, peripheral airway compliance and resistance were essential to describe lung function abnormalities of these asthmatic children. Parenchyma impairment (increased lung compliance) which was responsive to salbutamol was present in 18% of asthmatic children. After salbutamol, peripheral airway resistance decreased while peripheral airway compliance increased, arguing for asthma-related SAD. R5-20Hz independently correlated with the two latter parameters but was increased in two thirds of children with increased Rint only.Conclusion. Additional modeling of IOS results can be a reliable tool to assess the presence and extent of SAD in young asthmatic children.

[Characteristics of patients who received an indication of involuntary admission, with or without the involvement of a third party, in a Parisian psychiatric emergency unit]

BACKGROUND

The French mental health law, first enacted on July 5, 2011, introduced the possibility of psychiatric commitment in case of extreme urgency (imminent peril - ASPPI). The decision of involuntary admission can then be made by the hospital director based on a medical certificate, without the need of a third party request. This procedure was intended to be applied on an exceptional basis, but its use is steadily increasing against the other types of involuntary care. Our study aimed at comparing the characteristics of patients who had received an indication for involuntary admission due to imminent peril (ASPPI) or at the request of a third party (ASPDT/u) in a psychiatric emergency ward, according to sociodemographic and clinical characteristics and regarding the potential implication of a third party.

METHODS

An observational study was conducted among patients from the Centre Psychiatrique d'Orientation et d'Accueil (CPOA), located at Sainte-Anne hospital in Paris, from August 1st to 31st, 2016.

RESULTS

One hundred and fifty patients with an indication for involuntary commitment were included, 101 of whom for ASPDT/u (67 %) and 49 for ASPPI (33 %). For more than half of the patients from the ASPPI group, a third party had been identified with (39 %) or without (17 %) contact information. Compared to ASPDT/u patients, ASPPI individuals were more socially vulnerable, showed more negligence, and had a lower mean functioning score. The indication for ASPPI status was also associated with behavioural quirks, prior psychiatric hospitalization (especially as an ASPPI patient) and with the diagnosis of chronic psychosis instead of mood disorder.

CONCLUSION

Our exploratory results help to better understand how the ASPPI procedure is used in psychiatric emergency wards six years after enactment of the law. They highlight the differences between ASPPI patients and ASPDT/u and raise ethical issues regarding involuntary psychiatric care.

Pathophysiology of dyspnoea in acute pulmonary embolism: A cross-sectional evaluation

BACKGROUND AND OBJECTIVE

Dyspnoea in pulmonary embolism (PE) remains poorly characterized. Little is known about how to measure intensity or about the underlying mechanisms that may be related to ventilatory abnormalities, alveolar dead space ventilation or modulating factors such as psychological modulate. We hypothesized that dyspnoea would mainly be associated with pulmonary vascular obstruction and its pathophysiological consequences, while the sensory-affective domain of dyspnoea would be influenced by other factors.

METHODS

We undertook a prospective study of 90 consecutive non-obese patients (mean ± SD age: 49 ± 16 years, 41 women) without cardiorespiratory disease. All patients were hospitalized with symptoms for <15 days and a confirmed PE (multi-detector computed tomography (MDCT) scan, n = 87 and high-probability ventilation/perfusion scan, n = 3). Patients underwent assessment of dyspnoea using the Borg score, modified Medical Research Council (mMRC) scale, assessment of psychological trait, state of anxiety and depression and chest pain via the Visual Analogical Scale at the time of maximum dyspnoea. Functional evaluations such as the quantitative ventilation-perfusion lung scan, echocardiography, alveolar dead space fraction and tidal ventilation measurements were completed within 48 h of admission.

RESULTS

Multivariate analyses demonstrated that dyspnoea was mainly linked to pulmonary vascular obstruction and/or its consequences such as raised pulmonary arterial pressure and chest pain. The sensory-affective domain of dyspnoea showed additional determinants such as age, depression and breathing variability.

CONCLUSION

Dyspnoea is mainly related to vascular consequences of PE such as increased pulmonary arterial pressure or chest pain. The sensory-affective domain of dyspnoea also correlates with age, depression and breathing variability.

Cross-sectional assessment of exertional dyspnea in otherwise healthy children

OBJECTIVES

Exertional dyspnea during sport at school in children with asthma or in otherwise healthy children is commonly attributed to exercise-induced asthma (EIA), but when a short-acting beta agonist (SABA) trial fails to improve symptoms the physician is often at a loose end.

DESIGN

The aims were to prospectively assess the causes of exertional dyspnea in children/adolescents with or without asthma using a cardiopulmonary exercise test while receiving a SABA and to assess the effects of standardized breathing/reassurance therapy.

RESULTS

Seventy-nine patients (12.2 ± 2.3 years, 41 girls, 49 with previously diagnosed asthma) with dyspnea unresponsive to SABA were prospectively included. Exercise test outcomes depicted normal or subnormal performance with normal ventilatory demand and capacity in 53/79 children (67%) defining a physiological response. The remaining 26 children had altered capacity (resistant EIA [n = 17, 9 with previous asthma diagnosis], vocal cord dysfunction [n = 2]) and/or increased demand (alveolar hyperventilation [n = 3], poor conditioning [n = 7]). Forty-two children who had similar characteristics than the remaining 37 children underwent the two sessions of standardized reassurance therapy. They all demonstrated an improvement that was rated "large." The degree of improvement correlated with % predicted peak V'O2 (r = -0.37, P = 0.015) and peak oxygen pulse (r = -0.45, P = 0.003), whatever the underlying dyspnea cause. It suggested a higher benefit in those with poorer conditioning condition.

CONCLUSIONS

The most frequent finding in children/adolescents with mild exertional dyspnea unresponsive to preventive SABA is a physiological response to exercise, and standardized reassurance afforded early clinical improvement, irrespective of the dyspnea cause.

Use of specific airway resistance to assess bronchodilator response in children

BACKGROUND AND OBJECTIVE

Changes in specific airway resistance (ΔsRaw) after bronchodilation, as measured by plethysmography and FEV(1) , are frequently considered to be interchangeable indices of airway obstruction. However, the baseline relationship between these two indices is weak, and the value of ΔsRaw that best predicts FEV(1) reversibility in children has yet to be determined. The aim of this study was (i) to establish the sRaw cut-off value that best distinguishes between positive and negative bronchodilator responses, as measured by FEV(1) reversibility; (ii) to determine whether the discrepancy between ΔsRaw and ΔFEV(1) might be explained by independent correlations between ΔFEV(1) and both ΔsRaw (mainly airway obstruction) and ΔFVC (airway closure); and (iii) to assess the effect of height and age on the relationship between ΔsRaw and ΔFEV(1) .

METHODS

A retrospective study was performed in 481 children (median age 10.5years, range 6.1-17.6) with actual or suspected asthma, for whom sRaw and spirometry data were obtained at baseline and after administration of a bronchodilator.

RESULTS

The sRaw cut-off value that best predicted FEV(1) reversibility was a 42% decrease from baseline (P=0.0001, area under the curve 0.70, sensitivity 55%, specificity 77%) and was independent of height and age. Changes in FEV(1) were significantly but independently related to ΔsRaw and ΔFVC (index of air trapping) (r=0.40, P<0.0001 and r=0.39, P<0.0001, respectively).

CONCLUSIONS

A 42% decrease in sRaw predicted FEV(1) reversibility reasonably well, whereas a smaller decrease in sRaw failed to detect approximately one out of two positive responses detected by FEV(1) , with no influence of height or age.

Lung function impairment evidenced by sequential specific airway resistance in childhood persistent asthma: a longitudinal study

BACKGROUND

Specific airway resistance (sRaw) is virtually independent of lung growth, height, and gender, thus facilitating longitudinal follow-up.

OBJECTIVE

To assess whether a specific phenotype of asthmatic children with a decline in lung function can be evidenced using sRaw.

METHODS

The authors hypothesized that sequential sRaw measurements over a long period would detect subtle trends. Clinical and functional data of children with persistent asthma under inhaled corticosteroids, evaluated at least three times per year for at least 4 years, were retrieved from a database.

RESULTS

One hundred fourteen children (30 girls) were followed for (median [interquartile range]) 6.9 years [5.6-7.9]. Data from 1699 measurements of sRaw (median 14/child) allowed the calculation of individual slopes of sRaw plotted against time demonstrating stable values in the group as a whole between 4 and 18 years. A positive correlation between individual slopes and the degree of intraindividual variation of sRaw was observed (R(2) = .16; p < .0001). Children with more than one positive skin test showed larger intrasubject variation of sRaw (p = .011). In 19/114 children (17%), a significant increase in sRaw of 12.3% per year (median) was observed. As compared to children without, those with a significant increase in sRaw were boys (p < .0001), had a lower initial (p = .008) and a higher final resistance (p = .025) but did not differ in terms of inhaled corticosteroid dose.

CONCLUSION

This retrospective study identifies a specific phenotype of asthmatic children that develops an impairment of lung function, confirming the results of a post hoc analysis of the Childhood Asthma Management Program study.

Gas trapping is associated with severe exacerbation in asthmatic children

BACKGROUND

Gas trapping suggesting small airway disease is observed in adult asthmatic suffering from severe asthma. The aim of the study was to assess whether gas trapping could be evidenced in asthmatic children with/without severe exacerbation and with/without symptoms during the past three months.

METHODS AND PATIENTS

Forced expiratory flows (FEV(1), FVC, MEF(25-75%), MEF(50%)), plethysmographic lung volumes (TLC, FRC, RV) before and after bronchodilation (BD) were recorded in asthmatic children with documented airflow reversibility. Three groups were defined according to the presence during the last three months of 1) severe exacerbation (oral steroid: 3 consecutive days) 2) asthma symptoms without severe exacerbation and 3) without any symptom (GINA guidelines).

RESULTS

180 children (median 11.3 years, range 6.3-17.6, 57 girls) were included, 24 (13%) had at least one severe exacerbation, 58 (33%) had respiratory symptoms without severe exacerbation and 98 (54%) had no symptom during the past 3 months. Forced expiratory flows did not significantly differ in these three groups, while RV/TLC was significantly higher in the first group before and even after bronchodilation: before BD, 0.27 +/- 0.07, 0.24 +/- 0.05 and 0.23 +/- 0.05, respectively (p = 0.016) and after BD, 0.25 +/- 0.07, 0.21 +/- 0.05, 0.21 +/- 0.05, respectively (p = 0.003).

CONCLUSION

In asthmatic children, gas trapping is associated with occurrence of a severe exacerbation during the last three months, suggesting a small airway disease that is not evidenced by forced expiratory flows.

Lumen areas and homothety factor influence airway resistance in COPD

The remodelling process of COPD may affect both airway calibre and the homothety factor, which is a constant parameter describing the reduction of airway lumen (h(d): diameter of child/parent bronchus) that might be critical because its reduction would induce a frank increase in airway resistance. Airway dimensions were obtained from CT scan images of smokers with (n=22) and without COPD (n=9), and airway resistance from plethysmography. Inspiratory airway resistance correlated to lumen area of the sixth bronchial generation of right lung, while peak expiratory flow correlated to the area of the third right generation (p=0.0009, R=0.57). A significant relationship was observed between h(d) and resistance (p=0.036; R(2)=0.14). A modelling approach of central airways (5 generations) further described the latter relationship. In conclusion, a constant homothety factor can be described by CT scan analysis, which partially explains inspiratory resistance, as predicted by theoretical arguments. Airway resistance is related to lumen areas of less proximal airways than commonly admitted.

The link between exhaled NO and bronchomotor tone depends on the dose of inhaled steroid in asthma

BACKGROUND

Exhaled NO (FE(NO)) is a steroid dose dependent eosinophilic inflammometer, but also a mediator of bronchomotor tone, but statistically significant relationships have infrequently been obtained with pulmonary function tests (PFT). The aim was to test the hypothesis that the relationships between FE(NO) and PFT could be uncovered by inhaled corticosteroid (ICS) treatment, namely that a link between FE(NO) and bronchodilator response (an index of bronchomotor tone) would appear under ICS.

METHODS

Exhaled NO, forced expiratory flows and lung volumes were measured in atopic asthmatic children without recent (one month) respiratory symptoms.

RESULTS

Two hundred and thirty children (mean + or - SD, age: 11.2 + or - 2.5 years, 69 girls) were included (% predicted, FEV(1): 100 + or - 14; FEF(50%): 76 + or - 23; RV: 107 + or - 29). The relationship between ICS dose (GINA classification) and FE(NO) plateaued in children with an ICS dose higher than 200 microg beclomethasone equipotent daily dose: FE(NO) (median [25th-75th percentiles]), 43 ppb [15-105] (no treatment, n=65), 33 ppb [15-77] (low dose, n=70), 23 ppb [12-57] (medium dose, n=57) and 26 ppb [9-49] (high dose, n=38). Statistically significant relationships between FE(NO) and PFT were only observed in children receiving more than 200 microg/day ICS: with FEV(1) (medium ICS dose: rho=0.43, p=0.001; high dose: rho=0.32, p=0.052) and bronchodilator (400 microg salbutamol) response (medium dose: rho=0.54, p=0.001; high dose: rho=0.65, p=0.002).

CONCLUSIONS

A positive correlation between FE(NO) and bronchomotor tone appears with increasing ICS doses in atopic children with clinically controlled asthma, which further suggests that children depicting the highest FE(NO) values may have lesser steroid sensitivity.

What does a single exhaled nitric oxide measurement tell us in asthmatic children?

BACKGROUND

Due to the multiple factors affecting exhaled nitric oxide (NO) value, physicians are often puzzled by the result of a single measurement in asthmatic patients.

OBJECTIVE

The aim of this prospective transversal study was to evaluate the relative contributions to exhaled NO fraction (FE(NO)) of the commonly considered major NO determinants, i.e., recent symptoms (upper and lower respiratory tract), atopy (prick skin tests and degree of allergic exposure), and treatment (dose of inhaled corticosteroid [ICS]) to know what information gives a single measure.

METHODS

FE(NO) at 50 mL/s expiratory flow was measured in 199 asthmatic children (141 boys, age: 11.2 years +/- 2.5 years). The allergic risk due to pollen exposure (ARPE index) was independently evaluated by the "Réseau National de Surveillance Aérobiologique."

RESULTS

A multivariate analysis of FE(NO) as dependent variable showed that explanatory variables explained 23% of total FE(NO) variance (symptoms > atopy > ICS). In the children without recent symptoms (n = 118), a FE(NO) > 23 ppb predicted atopy (sensitivity 47%, specificity 85%, p = 0.0006). Multiple regression only showed a trend to significance between FE(NO) and the dose of ICS (p = 0.057, r = - 0.19). Incidentally, despite similar dose of ICS, children under fluticasone (mean +/- SD, 259 +/- 149 microg/day) had lower FE(NO) than those under budesonide (299 +/- 195 microg/day) (median [interquartile], 21 ppb [14-42], n = 55 versus 35 ppb [19-47], n = 104; p = 0.007), which may be due to a higher potency of fluticasone. A relationship between FE(NO) and ARPE index was significant in children with exclusive seasonal sensitisation (n = 31, r = 0.48, p = 0.008).

CONCLUSION

Common exhaled NO determinants weakly explain a single value of FE(NO), which only can confidently predict atopy.

Relationships between specific airway resistance and forced expiratory flows in asthmatic children

BACKGROUND

The earliest changes associated with airflow obstruction in asthmatic children are a proportionally greater reduction in FEF(50%) than in FEV(1) using spirometry, and an increase in specific airway resistance (sRaw) using body plethysmography. Consequently, we hypothesized that sRaw could be better linked to FEF(50%) than to FEV(1). The first aim was to assess the relationships between forced expiratory flows and sRaw in a large group of asthmatic children in a transversal study. We then performed a longitudinal study in order to determine whether sRaw of preschool children could predict subsequent impairment of forced expiratory flows at school age.

METHODOLOGY

Pulmonary function tests (sRaw and forced expiratory flows) of 2193 asthmatic children were selected for a transversal analysis, while 365 children were retrospectively selected for longitudinal assessment from preschool to school age.

PRINCIPAL FINDINGS

The transversal data showed that sRaw is differently related to FEF(50%) (-1/sRaw) and to FEV(1) (near linearly). These results were further explained by a simple one-compartment lung model, which justified the shape of the observed relationships. As hypothesized, sRaw correlated more strongly to FEF(50%) than to FEV(1) (r = -0.64 versus -0.39, respectively; p<0.001). In the longitudinal part of the study, sRaw at preschool age correlated with subsequent FEF(50%) (% predicted) (-0.31, 95% CI, -0.40 to -0.22), but weakly with subsequent FEV(1) (% predicted) (-0.09, 95% CI, -0.20 to 0).

CONCLUSION

Specific Raw is more strongly related to FEF(50%) than to FEV(1) and could be used in preschool children to predict subsequent mild airflow limitation.

Can bronchodilator response predict bronchial response to methacholine in preschool coughers?

The aim of the present study was to determine the relationship between bronchodilator response, assessed by interrupter resistance (Rint), and bronchial reactivity in preschool children with chronic cough. Thirty-eight children coughers (median age 5.0 years, range 2.8-6.4) were tested. Bronchodilator response was recorded within 4 months before methacholine challenge. Response to the latter was assessed using transcutaneous partial pressure of oxygen and Rint. Children were considered responders if a 20% fall in transcutaneous partial pressure of oxygen occurred during the bronchial challenge. Bronchodilator response was not different between responders (n = 24) and nonresponders (n = 14) [median (range) -0.11 (-0.44-0.09) vs. -0.08 (-0.21-0.10) kPa L(-1) sec; respectively]. However, none of the nonresponders had a bronchodilator response larger than -0.21 kPa L(-1) sec, this cutoff had a 100% positive and a 44% negative predictive value to predict a positive methacholine challenge. The relationship between bronchodilator response and bronchial methacholine responsiveness reached the limit of significance (P = 0.048). Furthermore, the magnitude of the bronchodilator response was correlated to the level of methacholine-induced level of bronchoconstriction (P = 0.01), and to the postchallenge bronchodilation (P = 0.04), all values expressed as % predicted. Moreover, the postbronchodilator Rint value obtained with preceding methacholine challenge was lower than the postbronchodilator value without preceding methacholine challenge in 71.4% (10/14) of the nonresponders and in only 33.3% (8/24) of the responders. Conclusions in preschool coughers bronchodilator response, assessed by the interrupter technique, was correlated to the bronchial responsiveness to methacholine. Non responders had a bronchodilator response not larger than -0.21 kPa L(-1) sec.

Interrupter resistance short-term repeatability and bronchodilator response in preschool children

Interrupter resistance (Rint) technique can be easily and successfully performed in preschool children. The establishment of Rint short-term repeatability is essential to interpret any Rint change after a pharmacological intervention.

AIMS OF THE STUDY

In preschool children with asthma or chronic cough: (1) to assess two indices of short-term repeatability: (a) intra-measurement and (b) within-occasion between-test repeatability; (2) to study the relationship between short-term repeatability and bronchodilator response (BDR).

RESULTS

Rint intra-measurement repeatability assessed by the coefficient of variation was similar at baseline and after bronchodilator in asthmatics and in coughers (median 10% and 12%, respectively). There was no significant difference between asthmatics and coughers for both coefficient of repeatability (CR) (0.25 kPa L(-1)s and 32% of predicted vs 0.16 kPa L(-1) s and 21% of predicted, respectively) and BDR (median -14.7% vs -21.1% of predicted, respectively). However, in 20% of the study children, baseline variability of Rint modified the significance of the BDR.

CONCLUSION

In the present study, Rint short-term repeatability was similar to that of previous studies. Similar Rint repeatability in coughers and in asthmatic children favored the use of asthmatic CR for both populations, and a -35% cut-off as a positive BDR. In 20% of study children, baseline Rint variability could influence the significance of the BDR. In order to improve assessment of BDR using Rint, further studies are needed (1) to compare the variability of Rint to other resistance measurement techniques and (2) to define the best method for Rint calculation and for expression of BDR.

Relevance of a portable spirometer for detection of small airways obstruction

While portable spirometers are increasingly used, little attention has been paid to test their validity for measurement of flows in small airways. The aim of this study was to compare the Spirotel portable spirometer to a laboratory spirometer (Jeager PFT), with regard to accuracy in measuring forced expiratory flows, and more specifically those influenced by small airways (FEF(25-75)). Fifty-nine children (mean age, 12 years; range, 7-17), were studied at baseline and after a bronchodilator inhalation. Spirometers were tested separately in a randomly designed order. A total of 117 sessions of flow-volume curves was performed with each spirometer. We obtained at least two acceptable and reproducible curves in 88% and 76% of the sessions, with the laboratory and the portable spirometers, respectively. Unacceptable curves were easily detected by visual inspection of flow-time and flow-volume waveforms. Agreement was excellent between spirometers for the measurement of all expiratory flows, both at baseline and postbronchodilator. More specifically, agreement between spirometers was as high for measurements of FEF(25-75) (intraclass correlation coefficients 0.97) as for proximal flows. High correlations were found between baseline expiratory flows measured by each spirometer (and expressed as percent of predicted values), both in large and small airways (P < 0.001). The portable spirometer was highly sensitive for detecting small airways obstruction, as compared to the laboratory spirometer. Finally, the magnitudes of bronchodilator-related flow changes were also highly correlated, both in large and small airways (P < 0.001 and P = 0.004, respectively). We conclude that the Spirotel portable spirometer is reliable for measurement of forced expiratory flows, in large and small airways, provided that all curve waveforms can be stored and available for visual inspection.

Neural substrates for the perception of acutely induced dyspnea

Little is currently known about the brain regions involved in central processing of dyspnea. We performed a functional imaging study with positron emission tomography (PET) to assess brain activation associated with an important component of dyspnea, respiratory discomfort during loaded breathing. We induced respiratory discomfort in eight healthy volunteers by adding external resistive loads during inspiration and expiration. Brain activation was characterized by a significant increase in regional cerebral blood flow (rCBF) (Z score of peak activation > 3.09). As compared with the unloaded control condition, high loaded breathing was associated with neural activation in three distinct brain regions, the right anterior insula, the cerebellar vermis, and the medial pons (respective Z scores = 4.75, 4.44, 4.41). For these brain regions, we further identified a positive correlation between rCBF and the perceived intensity of respiratory discomfort (respective Z scores = 4.45, 4.75, 4.74) as well as between rCBF and the mean amplitude of mouth pressure swings (DeltaPm), the index of the main generating mechanism of the sensation (respective Z scores = 4.67, 4.36, 4.31), suggesting a common activation by these two parameters. Furthermore, we identified an area in the right posterior cingulate cortex where neural activation was specifically associated with perceived intensity of respiratory discomfort that is not related to DeltaPm (Z score = 4.25). Our results suggest that respiratory discomfort related to loaded breathing may be subserved by two distinct neural networks, the first being involved in the concomitant processing of the genesis and perception of respiratory discomfort and the second in the modulation of perceived intensity of the sensation by various factors other than its main generating mechanism, which may include emotional processing.

Effect of cetirizine on bronchial hyperresponsiveness in patients with seasonal allergic rhinitis and asthma

Although H1 antihistamine compounds (H1) are highly effective in the treatment of allergic rhinitis (AR), their role in the treatment of asthma is still controversial. Because a strong association between AR and bronchial hyperresponsiveness (BHR) has been reported, this study was designed to assess the effect of a new H1 anti histamine, cetirizine (C), on nonspecific BHR in patients with AR. Twelve patients were included in a double-blind, crossover, placebo-controlled trial. All patients had positive skin tests for common allergens and showed BHR to inhaled methacholine after specific nasal allergenic challenge. After a washout period of 1 week to ensure the stability of the BHR, the patients received, by crossover randomization, C 10 mg daily or placebo (P) for 2 weeks. After each treatment period, BHR and nasal blocking index (NBI) were measured 1 and 6 h after nasal challenge. Bronchial responsiveness was expressed as methacholine PD20, the provocation dose of methacholine causing a 20% decrease in FEV1. Measurements were then performed after 2 weeks of C and after 2 weeks of P. Baseline values of PD20 (median) measured before challenge showed no difference after cetirizine or after placebo (1.36 mg). Results 1 h after allergen did not show significant differences between C (methacholine PD20=0.522 mg) and placebo (methacholine PD20=0.455 mg). By contrast, 6 h after challenge, methacholine PD20 was 0.918 mg for C and 0.483 mg for P (P=0.042). Similarly, NBI showed no change between C and P 1 h after challenge, whereas the difference was significant 6 h after challenge (P=0.011 ). These data demonstrate a protective nasal effect of C against BHR measured 6 h after nasal allergen challenge in patients with AR. They suggest that C may be useful in patients with asthma associated with AR.

Respiratory sensation related to resistive loads in lung transplant recipients

In order to assess the contribution of pulmonary afferent nerves to the processing of respiratory sensation, we compared sensation related to inspiratory resistive loaded breathing in 14 lung transplant recipients with normal lung function with that in 14 matched healthy control subjects. Respiratory sensation was characterized for each subject by the correlation coefficient and slope of the linear relationship between the intensity of sensation (expressed as Borg scores [BSc]) and peak inspiratory mouth pressure (peak Pm), which was considered the main physical stimulus of the sensation. Individual correlation coefficients were very high and did not differ between lung transplant recipients and controls. In contrast, individual slopes of BSc as a function of peak Pm (BSc/peak Pm slopes) were significantly lower in lung transplant recipients than in controls (0.63 versus 1.26; p < 0.01). Furthermore, ventilatory responses to external loads differed significantly between lung transplant recipients and controls in terms of higher values and ranges of generated peak Pm and peak inspiratory flow in lung transplant recipients than in controls (all p < 0.05). These results suggest that pulmonary afferent nerves may contribute to ventilatory and sensory responses to external loads. However, as suggested by the inverse relation between BSc/peak Pm slopes and peak Pm ranges, higher stimulus ranges in lung transplant recipients may also have contributed to intergroup differences in respiratory sensation related to loaded breathing.

Perception of bronchial obstruction in asthmatic patients. Relationship with bronchial eosinophilic inflammation and epithelial damage and effect of corticosteroid treatment

We studied the perception of bronchoconstriction in asthmatic subjects who were randomly treated with inhaled beta 2 agonist given either alone (n = 9) or associated with inhaled corticosteroids (n = 9). Methacholine and bradykinin challenges, bronchoalveolar lavage, and bronchial biopsies were performed in all subjects. After each dose of agonist, breathlessness was assessed using a visual analog scale (VAS) and the forced expiratory volume in 1 s (FEV1) was measured. The relationship between VAS scores and FEV1 and the slope of the regression line of VAS scores on the corresponding FEV1 (VAS/FEV1 slope) were analyzed for each agonist. Subjects without corticosteroids had good perception of methacholine but poor perception of bradykinin-induced bronchoconstriction. In subjects with corticosteroids, bronchoconstriction was well perceived whatever the agonist. VAS/FEV1 slopes for bradykinin but not for methacholine correlated negatively with the magnitude of eosinophilic inflammation in airway mucosa. VAS/FEV1 slopes for each agonist correlated positively with the percentage of basement membrane covered by airway epithelium. We conclude that in asthmatic patients perception of bronchoconstriction is related to eosinophilic inflammation and to epithelial damage in airways and that corticosteroid treatment is associated with improved perception of bronchoconstriction induced by bradykinin, a mediator endogenously produced in asthma.

Relationship between spontaneous dyspnoea and lability of airway obstruction in asthma

1. As marked lability of bronchial obstruction is a risk factor for asthma severity, it may influence dyspnoea, the most common subjective complaint in asthma. We therefore studied the relationship between spontaneous dyspnoea and the degree of bronchial lability, as assessed by the daily variability in peak expiratory flow rate and the bronchial responsiveness to either carbachol or salbutamol, in 33 stable symptomatic asthmatic patients. 2. Three times daily, for 10 consecutive days, the patients rated the intensity of their dyspnoea on a visual analogue scale and immediately afterwards recorded their peak expiratory flow rate. Within the next 5 days, we determined the bronchial response by measuring the forced expiratory volume in 1 s and the specific resistance of airways to either carbachol or salbutamol according to baseline airway obstruction. 3. We characterized dyspnoea for each patient by using two parameters: (1) the relationship with underlying airway obstruction, as assessed by the correlation coefficient r between dyspnoea scores and corresponding values of peak expiratory flow rate (r DSc-PEFR), and (2) the intensity, as assessed by the mean visual analogue scale dyspnoea score adjusted for comparable airway obstruction. Bronchial lability was characterized by (1) variability in mean daily peak expiratory flow rate and (2) bronchial responsiveness to either carbachol (as assessed by the threshold dose and the slope of the dose-response curve) or salbutamol (as assessed by the threshold dose and maximal response). We assessed the relationship between dyspnoea and bronchial lability by correlating each of their respective characteristics. 4. We found large inter-subject differences in both characteristics of dyspnoea.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronobiological study of the relationship between dyspnoea and airway obstruction in symptomatic asthmatic subjects

1. We performed a chronobiological study of the relationship between peak expiratory flow rate (PEFR) and magnitude of dyspnoea in 35 symptomatic asthmatic patients to determine how accurately asthmatic subjects assess spontaneous airway obstruction and whether this accuracy varies throughout the 24 h period and depends on characteristics of the subjects or asthma. 2. At 07.00, 11.00, 15.00, 19.00 and 23.00 hours on 8 consecutive days in their ordinary environment and under their usual drug regimen, the subjects first rated their dyspnoea with a visual analogue scale and immediately after recorded their PEFR. 3. The linear regression coefficients between dyspnoea score and PEFR for the 35 subjects were continuously distributed between -0.93 and +0.21, with most r values ranging from -0.9 to -0.5. The group median r values calculated at each time point showed that strongest correlation between dyspnoea score and PEFR occurred at 7 h. which coincided with the lowest PEFR values. 4. We chose r = -0.7 (r2 = 0.5) as a limit to distinguish good perceivers (-1 less than r less than or equal to -0.7) from bad perceivers of airway obstruction. These two populations differed only by a higher variability of both PEFR and dyspnoea score in good than in bad perceivers, but not for severity, duration or treatment of asthma, absolute value of dyspnoea score, age or sex. 5. Our study quantified an important intra- and between-subject variability in the accuracy of perception of spontaneous airway obstruction in asthmatic subjects which seems to be unrelated to most characteristics of asthma.