Increased ventilatory variability and complexity in patients with hyperventilation disorder.

It has been hypothesized that hyperventilation disorders could be characterized by an abnormal ventilatory control leading to enhanced variability of resting ventilation. The variability of tidal volume (VT) often depicts a nonnormal distribution that can be described by the negative slope characterizing augmented breaths formed by the relationship between the probability density distribution of VT and VT on a log-log scale. The objectives of this study were to describe the variability of resting ventilation [coefficient of variation (CV) of VT and slope], the stability in respiratory control (loop, controller and plant gains characterizing ventilatory-chemoresponsiveness interactions) and the chaotic-like dynamics (embedding dimension, Kappa values characterizing complexity) of resting ventilation in patients with a well-defined dysfunctional breathing pattern characterized by air hunger and constantly decreased PaCO2 during a cardiopulmonary exercise test. Compared with 14 healthy subjects with similar anthropometrics, 23 patients with hyperventilation were characterized by increased variability of resting tidal ventilation (CV of VT median [interquartile]: 26% [19-35] vs. 36% [28-48], P = 0.020; slope: -6.63 [-7.65; -5.36] vs. -3.88 [-5.91; -2.66], P = 0.004) that was not related to increased chemical drive (loop gain: 0.051 [0.039-0.221] vs. 0.044 [0.012-0.087], P = 0.149) but that was related to an increased ventilatory complexity (Kappa values, P < 0.05). Plant gain was decreased in patients and correlated with complexity (with Kappa 5 - degree 5: Rho = -0.48, P = 0.006). In conclusion, well-defined patients suffering from hyperventilation disorder are characterized by increased variability of their resting ventilation due to increased ventilatory complexity with stable ventilatory-chemoresponsiveness interactions.

Non specific pattern of lung function in a respiratory physiology unit: causes and prevalence: results of an observational cross-sectional and longitudinal study.

BACKGROUND: ATS/ERS Task Force has highlighted that special attention must be paid when FEV1 and FVC are concomitantly decreased (<5th percentile) and the FEV1/FVC ratio is normal (>5th percentile) because a possible cause of this non specific pattern (NSP) is collapse of small airways with normal TLC measured by body plethysmography (>5th percentile). Our objectives were to determine the main lung diseases associated with this pattern recorded prospectively in a lung function testing (LFT) unit, the prevalence of this pattern in our LFT and among the diseases identified, and its development. METHODS: Observational study of routinely collected data selected from our Clinical Database Warehouse. RESULTS: The prevalence of NSP was 841/12 775 tests (6.6%, 95% CI: 6.2 to 7.0%). NSP was mainly associated with seven lung diseases: asthma (prevalence of NSP among asthmatics: 12.6%), COPD/emphysema (prevalence 8.6%), bronchiectasis (12.8%), sarcoidosis (10.7%), interstitial pneumonia (4.0%), pulmonary hypertension (8.9%) and bilateral lung transplantation for cystic fibrosis (36.0%). LFT measurements were described in 185 patients with NSP and indisputable nonoverlapping causes. A moderate defect (FEV1: 66 ± 9% predicted) with mild lung hyperinflation (FRC: 111 ± 27%, RV: 131 ± 33% predicted: suggesting distal airway obstruction) was evidenced whatever the underlying cause. A long term stability of NSP was evidenced in 130/185 patients (70% 95% CI: 64 to 77%). CONCLUSIONS: NSP is observed in asthma, COPD/emphysema, bronchiectasis, sarcoidosis, pulmonary hypertension, interstitial pneumonia and after bilateral lung transplantation and remains stable in the majority of patients.

Tracheal section is an independent predictor of asthma in patients with nasal polyposis.

Airway anatomy could be a risk factor for asthma in susceptible patients with airway hyperresponsiveness. This anatomy can be described by only two parameters, the tracheal cross-sectional area and the homothety ratio, which describes the reduction of calibre at each subsequent generation. Thus, we hypothesized that the tracheal area would be linked to the risk of asthma presence. Tracheal area (measured by acoustic reflexion method) and airway responsiveness to metacholine (expressed as Dose Response Slope) were evaluated in 71 consecutive adult patients with nasal polyposis and normal baseline lung function. Hyperresponsiveness was evidenced in 30/71 patients (42%), and 20/71 patients (28%) were asthmatics. Forced expiratory flows were related to tracheal areas (mean value: 3.22±1.32cm(2)). In a logistic multivariate analysis, tracheal area and the degree of responsiveness were independent predictors of asthma. In conclusion, this study suggests that airway anatomy, crudely assessed by tracheal section, is an independent determinant of asthma.

Endurance-training in healthy men is associated with lesser exertional breathlessness that correlates with circulatory-muscular conditioning markers in a cross-sectional design.

Whether exertional dyspnoea can be attributed to poor circulatory-muscular conditioning is a difficult clinical issue. Because criteria of poor conditioning such as low oxygen pulse, low ventilatory threshold or high heart rate/oxygen consumption slope can be observed in heart or lung diseases and are not specific to conditioning, we assessed the relationships between physical exercise, conditioning and exertional breathlessness in healthy subjects, in whom the aforementioned criteria can confidently be interpreted as reflecting conditioning. To this end, healthy males with either low (inactive men, n = 31) or high (endurance-trained men, n = 31) physical activity evaluated using the International Physical Activity Questionnaire (IPAQ) underwent spirometry and incremental exercise testing with breathlessness assessment using Borg scale. No significant breathlessness was reported before the ventilatory threshold in the two groups. Peak breathlessness was highly variable, did not differ between the two groups, was not related to any conditioning criterion, but correlated with peak respiratory rate. Nevertheless, endurance-trained subjects reported lower breathlessness at the same ventilation levels in comparison with inactive subjects. Significant but weak associations were observed between isoventilation breathlessness and physical activity indices (Borg at 60 L/min and total IPAQ scores, rho = -0.31, p = 0.020), which were mainly attributable to the vigorous domain of physical activity, as well as with conditioning indices (Borg score at 60 L.min(-1) and peak oxygen pulse or heart rate/oxygen consumption slope, rho = -0.31, p = 0.021 and rho = 0.31, p = 0.020; respectively). In conclusion, our data support a weak relationship between exertional breathlessness and circulatory-muscular conditioning, the later being primarily related to vigorous physical activity.

Prevalence of overestimation or underestimation of the functional capacity using MRC score as compared to 6-minute walk test in patients with cardio-respiratory disorders.

OBJECTIVES: The first objective of our study was to assess whether patients diagnosed with cardio-respiratory disorders report overestimation or underestimation on recall (Medical Research Council (MRC) dyspnea scale) of their true functional capacity (walked distance during a 6-minute walk test (6MWT)). The second objective was to assess whether the measurement of breathlessness at the end of a 6MWT (Borg score) may help to identify dyspneic patients on recall. METHODS: The 6MWTs of 746 patients aged from 40 to 80 years who were diagnosed with either chronic obstructive pulmonary disease (COPD, n = 355), diffuse parenchymal lung disease (n = 140), pulmonary vascular diseases (n = 188) or congestive heart failure (n = 63) were selected from a prospective Clinical Database Warehouse. RESULTS: The percentage of patients who overestimated (MRC ≤ 2 with distance < lower limit of normal (LLN), 61/746, 8%; 95% confidence interval (CI): 6 to 10%) or underestimated (MRC > 2 with distance ≥LLN, 121/746, 16%; 95%CI: 14 to 19%) on recall their capacity was elevated. The overestimation seemed related to self-limitation, while the underestimation seemed related to patients who "work through" their breathing discomfort. These two latter groups of patients were mainly diagnosed with COPD. A Borg dyspnea score >3 (upper limit of normal) at the end of the 6MWT had 84% specificity for the prediction of a MRC score >1. CONCLUSION: Almost one fourth of patients suffering from cardio-pulmonary disorders overestimate or underestimate on recall their true functional capacity. An elevated Borg dyspnea score at the end of the 6MWT has a good specificity to predict dyspnea on recall.

Ageing and endurance training effects on quantity and quality of pulmonary vascular bed in healthy men.

It has recently been demonstrated that in healthy individuals, peak oxygen consumption is associated with a greater pulmonary capillary blood volume and a more distensible pulmonary circulation. Our cross-sectional study suggests that, in healthy men aged 20 to 60 years (n = 63), endurance sport practice (vigorous-intensity domain of the International Physical Activity Questionnaire) is associated with better quantity (pulmonary capillary blood volume) and quality (slope of increase in lung diffusion for carbon monoxide on exercise) of the pulmonary vascular bed, partly counterbalancing the deleterious effects of ageing, which remains to be demonstrated in a prospective longitudinal design.

Cross-sectional assessment of the relationships between dyspnea domains and lung function in diffuse parenchymal lung disease.

BACKGROUND: Activity-related dyspnea is the main contributor to the altered quality of life in diffuse parenchymal lung diseases (DPLD). Instruments pertaining to dyspnea are classified as pertaining to domains of sensory-perceptual experience, affective distress or symptom/disease impact; whether these domains are equally related to lung function impairments remains to be established. OBJECTIVES: They were to assess the relationships between two domains of dyspnea (sensory-perceptual experience and symptom impact) and pulmonary function tests according to their evaluation of ventilatory demand, capacity and drive in patients suffering from DPLD. METHODS: Fifty patients were prospectively enrolled (median age, 58 years; 25 women) and underwent spirometry, body plethysmography, measurements of lung diffusion for carbon monoxide (DLCO) and nitric oxide, maximal airway pressures (capacity and demand assessments), mouth occlusion pressure at 0.1 s (P0.1: respiratory drive assessment) and a 6-min walk test with Borg score assessment (dyspnea: sensory domain). The impact domain of dyspnea was evaluated using the baseline dyspnea index. RESULTS: The sensory domain of dyspnea was linked to demand (CO transfer coefficient, kCO) only, while the impact domain was independently linked to demand and capacity (kCO and forced vital capacity, respectively). Among resting pulmonary function tests, both P0.1 and DLCO allowed the assessment of these two domains of dyspnea. CONCLUSIONS: In DPLD, the sensory-perceptual domain of dyspnea is mainly linked to alterations in ventilatory demand while the impact domain is related to both demand and capacity. DLCO that assesses both demand and capacity and P0.1 were the strongest correlates of dyspnea.

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.

Cross-sectional assessment of the roles of comorbidities in resting and activity-related dyspnea in severely obese women.

OBJECTIVES: Obesity has been associated with a lesser degree of asthma control that may be biased by other comorbidities. The objectives of this cross-sectional study were to describe resting and activity-related dyspnea complaints according to the presence of obesity-related comorbidities (asymptomatic airway hyperresponsiveness (AHR), asthma, gastroesophageal reflux disease (GERD) and sleep-disordered breathing (SDB)). We hypothesized that obese women can exhibit both resting and activity-related dyspnea, independently of the presence of asthma. METHODS: Severely obese (body mass index (BMI) > 35 kg m(-2)) women prospectively underwent description of resting and activity-related dyspnea (verbal descriptors and Medical Research Council (MRC) scale), pulmonary function testing (spirometry, absolute lung volumes, and methacholine challenge test), oesogastro-duodenal fibroscopy, and overnight polygraphy. Thirty healthy lean women without airway hyperresponsiveness were enrolled. RESULTS: Resting dyspnea complaints were significantly more prevalent in obesity (prevalence 41%) than in healthy lean women (prevalence 3%). Chest tightness and the need for deep inspirations were independently associated with both asthma and GERD while wheezing and cough were related to asthma only in obese women. Activity-related dyspnea was very prevalent (MRC score > 1, 75%), associated with obesity, with the exception of wheezing on exertion due to asthma. Asymptomatic AHR and SDB did not affect dyspneic complaints. CONCLUSIONS: In severely obese women referred for bariatric surgery, resting dyspnea complaints are observed in association with asthma or GERD, while activity-related dyspnea was mainly related to obesity only. Consequently, asthma does not explain all respiratory complaints of obese women.

Risk factors for airway hyperresponsiveness in severely obese women.

Obesity affects airway diameter and tidal ventilation pattern, which could perturb smooth muscle function. The objective was to assess the pathophysiology of airway hyperresponsiveness in obesity while controlling for gastro-oesophageal reflux disease. Obese women (n=118, mean±SD BMI 46.1±6.8kg/m(-2)) underwent pulmonary function testing (including tidal ventilation monitoring and methacholine challenge) and oesogastro-duodenal fibroscopy. Fifty-seven women (48%, 95% CI: 39-57%) exhibited hyperresponsiveness (dose-response slope ≥2.39% decrease/µmol) that was independently and positively correlated with predicted % FRC, Raw0.5 and negatively correlated with sigh frequency during tidal ventilation. Obese women had an increased breathing frequency but a similar sigh frequency than healthy lean women (n=30). Twenty-two obese women (19%, 95% CI: 12-26%) were classified as asthmatics (hyperresponsiveness and suggestive symptoms) without confounding effect of gastro-oesophageal reflux disease. In conclusion, in women referred for bariatric surgery, unloading of bronchial smooth muscle (reduced airway calibre and sigh frequency) is associated with hyperresponsiveness.

Relationships between respiratory and airway resistances and activity-related dyspnea in patients with chronic obstructive pulmonary disease.

BACKGROUND: The aims of the study were: (1) to compare numerical parameters of specific airway resistance (total, sRaw(tot), effective, sRaw(eff) and at 0.5 L · s(-1), sRaw(0.5)) and indices obtained from the forced oscillation technique (FOT: resistance extrapolated at 0 Hz [Rrs(0 Hz)], mean resistance [Rrs(mean)], and resistance/frequency slope [Rrs(slope)]) and (2) to assess their relationships with dyspnea in chronic obstructive pulmonary disease (COPD). METHODS: A specific statistical approach, principal component analysis that also allows graphic representation of all correlations between functional parameters was used. A total of 108 patients (mean ± SD age: 65 ± 9 years, 31 women; GOLD stages: I, 14; II, 47; III, 39 and IV, 8) underwent spirometry, body plethysmography, FOT, and Medical Research Council (MRC) scale assessments. RESULTS: Principal component analysis determined that the functional parameters were described by three independent dimensions (airway caliber, lung volumes and their combination, specific resistance) and that resistance parameters of the two techniques were not equivalent, obviously. Correlative analyses further showed that Raw(tot) and Raw(eff) (and their specific resistances) can be considered as equivalent and correlated with indices that are considered to explore peripheral airways (residual volume (RV), RV/ total lung capacity (TLC), Rrs(slope)), while Rrs(mean) and Raw(0.5) explored more central airways. Only specific resistances taking into account the specific resistance loop area (sRaw(tot) and sRaw(eff)) and Rrs(slope) were statistically linked to dyspnea. CONCLUSION: Parameters obtained from both body plethysmography and FOT can explore peripheral airways, and some of these parameters (sRaw(tot), sRaw(eff,) and Rrs(slope)) are linked to activity-related dyspnea in moderate to severe COPD patients.

Diffusing capacity for carbon monoxide is linked to ventilatory demand in patients with chronic obstructive pulmonary disease.

Dyspnea is deemed to result from an imbalance between ventilatory demand and capacity. The single-breath diffusing capacity for carbon monoxide (DLCO) is often the best correlate to dyspnea in COPD. We hypothesized that DLCO contributes to the assessment of ventilatory demand, which is linked to physiological dead space /tidal volume (V(D)/V(T)) ratio. An additional objective was to assess the validity of non-invasive measurement of transcutaneous P(CO2) allowing the calculation of this ratio. Forty-two subjects (median [range] age: 66 [43-80] years; 12 females) suffering mainly from moderate-to-severe COPD (GOLD stage 2 or 3: n = 36) underwent pulmonary function and incremental exercise tests while taking their regular COPD treatment. DLCO% predicted correlated with both resting and peak physiological V(D)/V(T) ratios (r = -0.55, p = 0.0015 and r = -0.40, p = 0.032; respectively). The peak physiological V(D)/V(T) ratio contributed to increase ventilation (increased ventilatory demand), to increase dynamic hyperinflation and to impair oxygenation on exercise. Indirect (MRC score) and direct (peak Borg score/% predicted VO(2)) exertional dyspnea assessments were correlated and demonstrated significant relationships with DLCO% predicted and physiological V(D)/V(T) at peak exercise, respectively. The non-invasive measurement of transcutaneous P(CO2) both at rest and on exercise was validated by Bland-Altman analyses. In conclusion, DLCO constitutes and indirect assessment of ventilatory demand, which is linked to exertional dyspnea in COPD patients. The assessment of this demand can also be non invasively obtained on exercise using transcutaneous PCO(2) measurement.

Activity-related dyspnea is not modified by psychological status in people with COPD, interstitial lung disease or obesity.

Sensory (physiological) and affective (psychological) dimensions of dyspnea have been described but the usefulness of measuring psychological status in addition to ventilatory capacity (spirometry, lung volumes) in the assessment of exertional dyspnea remains controversial. We hypothesized that activity-related dyspnea would not be modified by psychological status. Principal component analysis (PCA) was used to reduce the number of parameters (psychological or functional) to fewer independent dimensions in 328 patients with altered ventilatory capacity: severe obesity (BMI ≥ 35, n = 122), COPD (n = 128) or interstitial lung disease (n = 78). PCA demonstrated that psychological status (Hospital Anxiety-Depression, Fatigue Impact scales) and dyspnea (Medical Research Council [MRC] scale) were independent dimensions. Ventilatory capacity was described by three main dimensions by PCA related to airways, volumes, and their combination (specific airway resistance, FEV(1)/FVC), which were weakly correlated with dyspnea. In conclusion, in patients with COPD, interstitial lung disease or severe obesity, psychological status does not modify activity-related dyspnea rating as evaluated by the MRC scale.

Pathophysiology of airway hyperresponsiveness in patients with nasal polyposis.

BACKGROUND: It has been hypothesized that airway hyperresponsiveness (AHR) is characterized by sensitivity (strength of stimulus) and reactivity (responsiveness to stimulus); the latter could be the intrinsic characteristic of AHR. The underlying mechanisms leading to AHR could be 1) airway inflammation, 2) reduction of forces opposing bronchoconstriction, and 3) structural airway changes/geometric factors. OBJECTIVE: Our main objective was to assess the relationships between reactivity in patients with nasal polyposis and these three mechanisms using measurements of 1) bronchial and bronchiolar/alveolar NO, 2) bronchomotor response to deep inspiration, and 3) forced expiratory flows and an index of airway to lung size, i.e. FEF(25-75%)/FVC. METHODS: Patients underwent spirometry, multiple flow measurement of exhaled NO (corrected for axial diffusion), assessment of bronchomotor response to deep inspiration by forced oscillation technique and methacholine challenge allowing the calculation of reactivity (slope of the dose-response curve) and sensitivity (PD(10)). RESULTS: One hundred and thirty-two patients were prospectively enrolled of whom 71 exhibited AHR. Airway reactivity was correlated with alveolar NO concentration (rho = 0.35; p = 0.017), with airflow limitation (FEF(25-75%): rho = -0.40; p = 0.003) and with an index of airway size to lung size (FEF(25-75%)/FVC: rho = -0.38; p = 0.005), of which only alveolar NO remained the only independent factor in a stepwise multiple regression analysis (variance 25%). Airway sensitivity was not correlated with any pulmonary function or exhaled NO parameter. CONCLUSION: In patients with nasal polyposis, alveolar NO is associated with airway reactivity, suggesting that bronchiolar/alveolar lung inflammation may constitute one intrinsic characteristic of increased responsiveness.

Too rapid increase and too much breathlessness are distinct indices of exertional dyspnea in COPD.

To assess whether different indices of dyspnea can be obtained from cardiopulmonary exercise test and whether these indices correlate with distinct physiological parameters in COPD. Forty-two COPD patients (12 females, median [IQ] age 66 [56-70] years; FEV(1)% predicted: 51 [38-65]) underwent pulmonary function and incremental exercise tests. A power law function described the oxygen consumption (V(O2)-Dyspnea relationship from which two indices correlated with MRC score: dyspnea score measured at 50% of predicted V(O2) (too much breathless for that effort) and tangent measured at 50% of peak dyspnea (too rapid increase in dyspnea at this time point). The former independently correlated with ventilation on exercise, while the latter independently correlated with baseline hyperinflation. An upward shift of both (iso)-V(O2) and -ventilation was evidenced in patients with higher levels of dyspnea (MRC score ≥ 3) and their tangents were significantly different. In conclusion, baseline hyperinflation is associated with the perception of a too rapid increase in dyspnea on exercise in COPD.

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.

Offline exhaled nitric oxide in emergency department and subsequent acute asthma control.

BACKGROUND: Few studies have evaluated exhaled NO measurement during acute asthma. OBJECTIVES: To evaluate exhaled NO fraction (FE(NO)) and peak expiratory flow (PEF) time-courses during acute asthma treatment (beta 2-agonist plus systemic steroid) and to assess whether FE(NO) time-course predicts subsequent asthma control. METHODS: Sixty-five asthmatic patients (mean +/- SD, 34 +/- 10 years) were prospectively enrolled in three Emergency Departments. RESULTS: Sixteen patients were excluded (failure of offline FE(NO) measurement at 100 mL/s [FE(NO 0.1)], n = 4, and early discharge). The 49 remaining patients performed FE(NO 0.1) and PEF on admission, at the 2nd (H2) and 6th hour (H6). Follow-up using an Asthma Control Diary was obtained in 27 of 49 patients, whether they were hospitalized (n = 9) or discharged (n = 18). All but 2 patients had elevated FE(NO) on admission (median [interquartile], 49 [26-78] ppb). Unlike PEF, mean FE(NO 0.1) of our sample was not significantly modified by treatment. No significant relationship was evidenced between exhaled NO and PEF variations. The variation of FE(NO 0.1) [H0 minus H6] was different in patients who were hospitalized (decrease of 8 +/- 20 ppb) versus discharged (increase of 5 +/- 20 ppb, p = 0.04). This variation of FE(NO 0.1) was correlated with the Diary score (control of subsequent week), an initial increase in FE(NO 0.1) being associated with better asthma control. Nevertheless, neither exhaled NO nor PEFR were good predictors of asthma control. CONCLUSIONS: An increase in FE(NO) is observed in almost all patients with acute asthma, and its subsequent increase within 6 hours is associated with a better degree of asthma control in the subsequent week.