Impulse oscillometry in acute and stable asthmatic children: a comparison with spirometry

Objective: Lung function tests have attracted interest for the diagnosis and follow-up of childhood asthma in recent years. For patients who cannot perform forced expiratory maneuvers, impulse oscillometry (IOS), performed during spontaneous breathing, may be an alternative tool. Methods: Thirty-five acute, 107 stable asthmatic and 103 healthy children who presented to our clinic performed IOS followed by spirometry before and after salbutamol inhalation. The mean baseline and reversibility of IOS and spirometry parameters were compared between the groups. Correlation analyses were undertaken within the asthmatics, and the healthy controls separately. To distinguish the three groups, the sensitivity and specificity of baseline and reversibility values of IOS and spirometry were computed. When spirometry was taken as the gold standard, the discriminating performance of IOS to detect the airway obstruction and reversibility was investigated. Results: The mean absolute values of Zrs, R5, R5?R20, X5, X10, X15, Fres, AX, and all spirometric parameters, and the mean reversibility values of R5, R10, Fres, AX and forced expiratory volume in one second were different between the groups and the highest area under curve values to discriminate the groups was obtained from area of reactance (AX) and ΔAX. Zrs, all resistance (including R5?R20) and reactance parameters, Fres and AX were correlated with at least one spirometric parameter. Spirometric reversibility was detected by ≤?22.34 and ≤?39.05 cut-off values of ΔR5 and ΔAX, respectively. Conclusions: IOS has shown a highly significant association with spirometric indices and reversibility testing. It may be a substitute for spirometry in children who fail to perform forced expiratory maneuvers.     

The airway hyperresponsiveness to methacholine may be predicted by impulse oscillometry and plethysmography in children with well-controlled asthma

Objective: Airway hyperresponsiveness (AHR) is a hallmark of asthma. Methacholine challenge test which is mostly used to confirm AHR is not routinely available. The aim of this study was to investigate the predictive values of fractional exhaled nitric oxide (FeNO), impulse oscillometry (IOS), and plethysmography for the assessment of AHR in children with well-controlled asthma. Methods: 60 children with controlled allergic asthma aged 6–18 years participated in the study. FeNO measurement, spirometry, IOS, and plethysmography were performed. Methacholine challenge test was done to assess AHR. PC20 and dose response slope (DRS) of methacholine was calculated. Results: Mild to severe AHR with PC20 < 4 mg/ml was confirmed in 31 (51.7%) patients. Baseline FeNO and total specific airway resistance (SRtot)%pred and residual volume (RV)%pred levels in plethysmography were significantly higher and FEV1%pred, FEV1/FVC%pred, MMEF%pred values were lower in the group with PC20 < 4 mg/ml. FeNO, SRtot%pred, and RV%pred levels were found to be positively correlated with DRS methacholine. The higher baseline FeNO, frequency dependence of resistance (R5–R20) in IOS and SRtot%pred in plethysmography were found to be significantly related to DRS methacholine in linear regression analysis (β: 1.35, p = 0.046, β: 4.58, p = 0.002, and β: 0.78, p = 0.035, respectively). The cut-off points for FeNO and SRtot% for differentiating asthmatic children with PC20 < 4 mg/ml from those with PC20 ≥ 4 mg/ml were 28 ppb (sensitivity: 67.7%, specificity: 72.4%, p < 0.001) and 294.9% (sensitivity: 35.5%, specificity: 96.6%, p = 0.013), respectively. Conclusion: IOS and plethysmography may serve as reliable and practical tools for prediction of mild to severe methacholine induced AHR in otherwise “seemingly well-controlled’’ asthma.     

Discriminative capacity of bronchodilator response measured with three different lung function techniques in asthmatic and healthy children aged 2 to 5 years

The primary aim of this study was to quantify and compare bronchodilator responsiveness in healthy and asthmatic children aged 2 to 5 yr. The secondary aim of the study was to compare discriminative capacity (i.e., sensitivity, specificity, and predictive values of the reversibility test for the diagnosis of asthma) for each of the lung function tests applied in the study. Specific airway resistance (sRaw) as measured by whole-body plethysmography, respiratory resistance as measured with the interrupter technique (Rint), and respiratory resistance and reactance at 5 Hz (Rrs5, Xrs5, respectively) as measured with the impulse oscillation technique were assessed before and 20 min after inhalation of terbutaline from a pressurized metered-dose inhaler via a metal spacer by 92 children (37 healthy controls and 55 asthmatic subjects). The study of healthy children followed a randomized, double-blind, crossover design, whereas the study of asthmatic children was open. Baseline lung function was significantly decreased in asthmatic children as compared with healthy control subjects as reflected by all techniques used in the study. sRaw, Rint, and Rrs5, but not Xrs5, improved significantly with terbutaline as compared with placebo in healthy control subjects. Lung function improved to a significantly greater extent in asthmatic children than in control subjects as reflected by all methods. sRaw provided the best discriminative power of such a bronchodilator response, with a sensitivity of 66% and specificity of 81% at the cutoff level of a 25% decrease in sRaw after bronchodilator administration. In conclusion, bronchodilator response measured by sRaw allows a separation of asthmatic from healthy young children. This may help define asthma in this clinically difficult-to-manage group of young wheezy children. The sensitivity and specificity of the other methods used in the study were less than those of sRaw.     

Assessment of airway function in young children with asthma: comparison of spirometry, interrupter technique, and tidal flow by inductance plethsmography

The assessment of airway function in young children requires adaptation of techniques designed for adults and/or application of techniques that do not require complex respiratory maneuvers. We sought to assess two methods of measuring airway function: time to peak expiratory flows as a ratio of expiratory time (T(PTEF)/T(E)), derived from respiratory inductance plethysmography, and total respiratory resistance by the interrupter technique (Rint), both obtained during quiet tidal breathing. Both techniques were referenced to FEV1 and flow at 50% expired volume (FEF50) from conventional spirometry in 30 children aged 4-8 years (median age, 6.9; range, 4.5-8.5 years) with a physician diagnosis of asthma and who were able to perform FEV1 with a repeatability of at least 8%. T(PTEF)/T(E) and Rint were performed in random order followed by spirometry, in order to reduce the possible effects of pulmonary stretch on tidal breathing measures. Coefficients of variation (CV) and mean absolute change/baseline standard deviation were derived for each measurement. Baseline FEV1 did not correlate significantly with T(PTEF)/T(E) (r = 0.025), but did correlate with Rint (r = 0.737, P < 0.001); respective relationships for change after bronchodilator were r = 0.09 (ns) and r = 0.64 (P < 0.001). FEF50 also correlated significantly with Rint (R = 0.769, P < 0.001) but not with T(PTEF)/T(E). FEV1 and FEF50 both increased postbronchodilator, with respective mean changes of 11.4% and 28% (P < 0.001), while Rint decreased by 24.3% (P < 0.001). No significant changes were noted for T(PTEF)/T(E). T(PTEF)/T(E) derived from inductance plethysmography does not detect mild airway obstruction or modest changes in airway caliber following bronchodilator in young children with asthma. The interrupter technique may have a role in assessing baseline airway function and response to therapy in children unable to perform reliable spirometry, and/or when the investigator wishes to avoid the possible influence of forced maneuvers on airway tone.     

Respiratory impedance response to a deep inhalation in asthmatic children with spontaneous airway obstruction.

The aim of the study was to determine whether the bronchomotor effect of a deep inhalation (DI) may be detected during tidal breathing in asthmatic children with spontaneous airway obstruction (AO). Two groups of children aged 5-15 yrs were studied. AO was mild in group 1 (n=12, forced expiratory volume in one second (FEV1) > or = 75% predicted) and moderate-to-severe in group 2 (n=9, FEV1 > or = 70% pred). The forced oscillation technique at 12 Hz using a head generator allowed the determination of respiratory resistance in inspiration (Rrsi) and expiration (Rrse) before and after DI, at baseline and after salbutamol. At baseline, Rrsi but not Rrse was found to decrease significantly after DI in group 1 but not in group 2. The change induced by DI was significantly different in group 1 (-1.5+/-0.5 hPa x s x L(-1)) compared to group 2 (0.5+/-0.5 hPa x s x L(-1)) and exhibited significant negative correlation to FEV1 % pred. After salbutamol, DI had no effect. In conclusion, asthmatic children show a bronchomotor response to deep inhalation that depends on the degree of airway obstruction. The effect is more readily demonstrated in inspiration than in expiration.     

Comparison between peak expiratory flow rate and forced expiratory volume in one second in the evaluation of children suspected to have asthma

This study was conducted to evaluate whether forced expiratory volume in 1 second (FEV1) for the diagnosis of bronchial reactivity by means of the free-running exercise test and bronchodilator inhalation, could be appropriately replaced by simple measurements of peak expiratory flow rate (PEFR) in children.We studied 108 referred symptomatic children (due to chronic cough or wheezing) suspected to have asthma aged 5-14y. Forced breathing spirometry and the "Mini-Wright peak flow meter" tests were recorded before and fifteen minutes after the challenge with free- running exercise or bronchodilator (Salbutamol) inhalation, regarding the baseline FEV1 value (FEV1> 80% considered as normal).There was a high correlation between PEFR and FEV1 (in absolute value and percent predicted) measured before and after bronchodilator inhalation test (r = 0.48, P = 0.05) in comparison to the values referred to free- running exercise test (r = 0.26, P = 0.01)."forced breathing spirometry" and "Mini-Wright peak flow" cannot be used interchangeably for diagnosing asthma, and PEFR measurement should remain a procedure for monitoring and following up the patients.     

Impulse oscillometry vs. body plethysmography in assessing respiratory resistance in children

In 334 children aged 5-18 years, we compared the results of plethysmographic measurements of airway resistance (Raw) with oscillometric (impulse oscillometry; IOS) assessment of respiratory properties of the respiratory system (resistance (R) at 5, 20, and 35 Hz). All three resistances correlated significantly with plethysmographic Raw, and the strongest correlation was seen for R5 (r = 0.64). R5, R20, and R35 were significantly greater than Raw in the whole group. In the group of children with obstruction (FEV(1)%FVC below lower limit of normal), R5 was still greater than Raw, while R20 and R35 were not. The Bland-Altman analysis comparing plethysmographic measurements with oscillometric R5 revealed a significant difference between Raw and R5 in the whole group, which disappeared in the group of obstructed patients. Oscillometric assessment of resistive properties of the respiratory system of the lung requires less patient cooperation than does plethysmography. As the results of measurements using oscillometric R5 are similar to those obtained by plethysmography, IOS may be useful in diagnosing children with obstructive respiratory diseases.     

Three 20-minute interspaced salbutamol inhalations as a test for the diagnosis of reversible airflow limitation in adult asthmatics.

Reversible airflow limitation represents an important parameter for the diagnosis of bronchial asthma. The aim of this study was to design a simple and useful test for the detection of reversible airflow limitation. The subjects were 29 patients with asthma and forced expiratory volume in 1 second (FEV1) < 80% predicted. Following baseline spirometry, subjects inhaled 1.5 mg of salbutamol by a nebulizer and then spirometry was performed 20 min later. The procedure was repeated three times. Subsequently, 13 patients received 30 mg of predonisolone orally once daily for 1 week. Spirometry was performed before and after the oral predonisolone therapy, and results were compared with those of salbutamol inhalation test. The mean increase in FEV1 over the baseline was 18.3% after the first salbutamol inhalation, 26.4% after the second inhalation, and 30.2% after the third inhalation. The increases in FEV1 were significant after each inhalation. The mean increases in the maximum expiratory flow rate at 50% (V50) and that at 25% (V25), measured from the flow volume loop, were 53.5% and 46.9% after the first inhalation, but there were no significant changes by repeated inhalations. A significant reversal of airflow limitation was demonstrated in 18 subjects after the first inhalation, 22 subjects after the second inhalation, and 27 subjects after the third inhalation. Improvement in FEV1 after oral predonisolone was equivalent to that after the third inhalation of salbutamol. A test composed of three 20-min interspaced salbutamol inhalations is useful for the diagnosis of asthma by demonstrating the presence of reversible airflow limitation.     

Formoterol and salbutamol metered aerosols: comparison of a new and an established beta-2-agonist for their bronchodilating efficacy in the treatment of childhood bronchial asthma

In this placebo-controlled, double-blind, single-dose study the new beta-2-agonist formoterol (one puff, 12 micrograms) was intraindividually compared with salbutamol (one puff, 100 micrograms) for onset, magnitude, and duration of bronchodilating efficacy in 15 young asthmatics aged 5 to 14 years with mild to severe asthma. All but one had regular antiasthmatic medication before beginning the study, but none was oral steroid dependent. Both medications produced rapid bronchodilatation within 10 minutes, reflected by a decrease in specific airway resistance (sRaw) with maximum effects at 10 minutes (salbutamol, 51%) and 30 minutes (formoterol, 60%). Significant bronchodilation was present at 10 minutes to 2 hours after inhalation of salbutamol and at 30 minutes to 8 hours after formoterol. Mean percent improvement over baseline was higher for formoterol at all measured times from 30 minutes to 12 hours, when 55% mean decrease in sRaw was still present. The effect of salbutamol was a less than 10% mean decrease in sRaw after 6 hours. The differences in sRaw decrease between the two medications were statistically significant at 4 to 10 hours after inhalation. Neither medication administered as an aerosol caused cardiac side effects. Both had a rapid onset of action and a comparable maximal effect. However, at the doses studied, formoterol produced a larger decrease in sRaw from baseline for longer periods after inhalation than did salbutamol.     

Within- and between-day variability of respiratory impedance,using impulse oscillometry in adolescent asthmatics

The objectives of the present study were to: 1) assess spirometric indices and respiratory impedance with forced oscillation (FO), using impulse oscillometry (IOS) in clinically stable asthmatic children over 3 consecutive days; 2) assess FO reactance (X), using an integrated index and resistance (R) separately during inspiration and expiration; and 3) assess effects on FO of hand support of cheeks vs. no hand support. Our hypotheses were: 1) because of increased sensitivity, IOS manifests day-to-day variability not demonstrable by spirometry; 2) IOS R during expiration exceeds that during inspiration; and 3) hand support of cheeks affects IOS R and X only minimally. We obtained triplicate twice-daily measures of IOS R and X in asthmatic adolescents at summer camp, in a convenience sample of children willing, with parental permission, to undergo repeated testing on consecutive days. Subjects received all medications between 6:30-7:30 AM, and were bronchodilated at time of testing. Subjects underwent IOS tests without hand support of cheeks, followed by tests with both hands supporting cheeks. ANOVA and regression analyses were used to discern technique differences.Significant differences in IOS inspiratory R5, R5 - R15 (frequency dependence of R), and low frequency reactance area (AX) occurred across 3 days, but spirometric indices were unchanged. Inspiratory R at 5 Hz (R5) was significantly smaller than expiratory R5 (P < 0.0001). ANOVA revealed no significant differences between hand and facial muscle cheek support for IOS R and X below 15 Hz, but significant differences occurred above 15 Hz.In conclusion, inspiratory R5, R5 - R15, and AX are sensitive measures for detecting changes in bronchomotor tone in adolescent asthmatic subjects, while expiratory R5 may be influenced by additional factors. Manual support of cheeks does not appear to affect IOS indices of peripheral airway obstruction in adolescent asthmatics. IOS is a practical method for quantifying respiratory mechanics, and its potential role in disease management warrants further study.     

Methacholine-induced asthma symptoms correlate with impulse oscillometry but not spirometry

Previous studies showed poor correlation between asthma symptoms and spirometric-based bronchial provocation tests. Use of impulse oscillometry (IOS) in airways resistance measurement may be more sensitive. In 20 individuals with stable asthma, we analysed the relationship between methacholine-induced asthma symptoms scores, IOS and spirometry. Following a screening visit, methacholine challenge testing was performed twice (visits 1 and 2). Dyspnoea, tightness and wheeze were quantified using visual analogue scores. IOS and spirometry were conducted at each incremental dose of methacholine. The Pearson correlation coefficient and linear regression analyses were conducted to explore the relations. A significant correlation was observed between methacholine-induced dyspnoea scores and the change in IOS measures of R((5)) (r=0.62, p=0.004) and X(5) (r=0.51, p=0.022), but not with the spirometric changes in FEV((1)) (r=0.37(,)p=0.11) or MEF(50) (r=0.32, p=0.17). In a multiple linear regression model, R(5) was the only significant variable to explain dyspnoea variability (p=0.003). Results of correlation analyses for chest tightness were similar to those obtained with dyspnoea. However, the symptom of wheeze showed correlation with IOS and spirometry. We conclude that airway resistance measured by IOS during methacholine challenge correlates better with asthma symptoms than traditional spirometric measures implying a higher sensitivity index.     

Clinical equivalence between salbutamol hydrofluoroalkane pMDI and salbutamol Turbuhaler at the same cumulative microgram doses in paediatric patients

This study aimed to demonstrate equivalent efficacy and safety between salbutamol delivered via the HFA134a pMDI (Hydrofluoroalkane 134a pressurised Metered Dose Inhaler) and the Turbuhaler dry powder inhaler in asthmatic children. This was a randomised, double-blind, double-dummy, placebo-controlled, crossover study in 10 asthmatic children aged 6-15 years who demonstrated at least 10% reversibility of FEV1 after inhaling 400 microg of salbutamol. On 5 single study days subjects received either placebo or cumulative doses of 100, 200, 400 and 800 microg of salbutamol at 30 minute intervals. Both devices were placebo on one study day while each device was active on two study days. FEV1 was measured before and 20 minutes after each dose. Heart rate was measured before spirometry. Mean FEV1 and heart rate at each time point and the area under the dose response time curve (AUC) were analysed using ANOVA. FEV1 increased similarly after cumulative doses of salbutamol on each of the study days, irrespective of device. Mean treatment difference in AUC was 0.01 L. min (95%CI -0.05 to 0.08 L). Heart did not differ at any dose. It is concluded that salbutamol delivery from a HFA pMDI and Turbuhaler is equivalenton a microgram basis in asthmatic children for efficacy and safety.     

Measurement of lung function in awake 2–4-year-old asthmatic children during methacholine challenge and acute asthma: A comparison of the impulse oscillation technique,the interrupter technique,and transcutaneous measurement of oxygen versus whole-body plethysmography

This study evaluated three techniques for testing of lung function in young awake children. We compared measurements by the forced or impulse oscillation technique (IOS), the interrupter technique (IT), and transcutaneous measurements of oxygen (tcPO₂) with concomitant measurements of specific airway resistance (sRaw) during methacholine challenge in 20 stable asthmatic children, 2–4 years old. Measurements were performed with all techniques after each dose of methacholine and after inhalation of a bronchodilator. Measurements were carried out during tidal breathing using a face-mask with a built-in mouthpiece. The ranking of sensitivity was as follows: sRaw > IOS, respiratory reactance at 5 Hz (Xrs5) > tcPO₂ > interrupter resistance (Rint) > IOS, respiratory resistance at 5 Hz (Rrs5). The sensitivity of sRaw and Xrs5 was not significantly different, but both were significantly more sensitive than Rint and Rrs5; the sensitivity of tcPO₂, Rint, and Rrs5 was not significantly different. Measurements in eight of the subjects performed during an episode of acute asthma yielded comparable results in regard to the sensitivity of the techniques. Measurements improved significantly after bronchodilator administration; however, the response to bronchodilator tended to be less during acute asthma and was best demonstrated by a deterioration of tcPO₂. All the evaluated techniques reliably reflect short-term changes in respiratory function and can provide clinically useful estimates of airway function. The techniques are non-invasive, are not dependent on the active co-operation or sedation of the subjects, and therefore are well suited for routine use in young children. Pediatr Pulmonol. 1996; 21:290–300. © 1996 Wiley-Liss, Inc.     

Oscillometric and spirometric bronchodilator response in preschool children with and without asthma

BACKGROUND:

Bronchodilator responses (BDR) are routinely used in the diagnosis and management of asthma; however, their acceptability and repeatability have not been evaluated using quality control criteria for preschool children.

OBJECTIVES:

To compare conventional spirometry with an impulse oscillometry system (IOS) in healthy and asthmatic preschool children.

METHODS:

Data from 30 asthmatic children and 29 controls (two to six years of age) who underwent IOS and spirometry before and after salbutamol administration were analyzed.

RESULTS:

Stable asthmatic subjects significantly differed versus controls in their spirometry-assessed BDR (forced expiratory volume in 1 s [FEV₁], forced vital capacity and forced expiratory flow at 25% to 75% of forced vital capacity) as well as their IOS-assessed BDR (respiratory resistance at 5 Hz [Rrs₅], respiratory reactance at 5 Hz and area under the reactance curve). However, comparisons based on the area under the ROC curve for ΔFEV₁ % initial versus ΔRrs₅ % initial were 0.82 (95% CI 0.71 to 0.93) and 0.75 (95% CI 0.62 to 0.87), respectively. Moreover, the sensitivity and specificity for ΔFEV₁ ≥9% were 0.53 and 0.93, respectively. Importantly, sensitivity increased to 0.63 when either ΔFEV₁ ≥9% or ΔRrs₅ ≥29% was considered as an additional criterion for the diagnosis of asthma.

CONCLUSION:

The accuracy of asthma diagnosis in preschool children may be increased by combining spirometry with IOS when measuring BDR.     

脉冲振荡法在阻塞性通气功能障碍评定中的价值

目的 探讨脉冲振荡法评定阻塞性通气功能障碍的应用价值及其与常规肺通气功能测定的关系.方法 2007年11月至2008年5月,采用德国耶格公司的肺功能仪及产品说明书给出的预计值公式,测定100例(男72例,女28例)门诊和住院患者的FEV1、FVC、5 Hz时气道阻力(R5)、20 Hz时气道阻力(R20)、结构参数图中的中心阻力(Rc)和周边阻力(Rp)的实测值,FEV1、R5和R20占预计值%,以及FEV1/FVC等指标.并对常规和脉冲振荡法测定肺通气功能的指标进行相关分析.结果 所有受试者均获得满意的脉冲振荡测定结果.当FEV1/FVC低于正常时(＜70%),R5和Rp明显升高至(5.3±2.1)和(6.2±2.9)cm H2O·L-1·S-1(1 cm H2O=0.098 kPa),FEV1与R5、Rp呈显著负相关(r值分别为-0.38和-0.47,均P＜0.01),FVC与R5、Rp也呈显著负相关(r值分别为-0.28和-0.37,均P＜0.01).FEV1占预计值%、FVC占预计值%、FEV1/FVC与R5占预计值%均呈显著负相关(r值分别为-0.49、-0.39和-0.43,均P＜0.01).结论 脉冲振荡法的测定指标可用于评估阻塞性通气功能障碍,尤其是R5的诊断价值最大,并且与常规肺通气功能指标之间有良好的相关性.     

FEV1 response to bronchodilation in an adult urban population

BACKGROUND: Most studies evaluating bronchodilation in flow-volume spirometry have been conducted in patients with obstructive airways diseases, but less is known about bronchodilation responses in the general population or in healthy subjects. METHODS: We evaluated an urban population sample of 628 adults (260 men, 368 women) aged 25 to 74 years with flow-volume spirometry using inhalation of 0.4 mg of a salbutamol aerosol with a spacer device for bronchodilation. On the basis of a structured interview, a subgroup of 219 healthy, asymptomatic nonsmokers was selected. RESULTS: In the population sample, the average increase in FEV(1) from baseline after salbutamol inhalation was 77.2 mL (SD, 109.7 mL) or 2.5% (SD, 3.9%). In healthy asymptomatic nonsmokers, the mean change in FEV(1) was 62.0 mL (SD, 89.7 mL) or 1.8% (SD, 2.6%). In the whole population, the 95th percentile limit of the increase in FEV(1) was 8.5%, while it was 5.9% among healthy asymptomatic nonsmokers. The absolute change in FEV(1) correlated significantly with baseline FVC (p < 0.01). The FEV(1)/FVC ratio at baseline was the strongest influencing factor for the bronchodilation response. CONCLUSIONS: The results indicate that a significant increase in FEV(1) from baseline in a bronchodilation test is around 9% in an urban population. The level of the significant absolute increase in FEV(1) seems to depend on FVC. Low baseline FEV(1)/FVC ratio, reflecting airflow limitation, is the strongest determinant for FEV(1) response to bronchodilation.     

Comparison of the forced oscillation technique and the interrupter technique for assessing airway obstruction and its reversibility in children

The forced oscillation technique (FOT) and interrupter technique are particularly attractive for pediatric use as they require only passive cooperation from the patient. We compared the sensitivity and specificity of these methods for detecting airway obstruction and its reversibility in 118 children (3-16 yr) with asthma or chronic nocturnal cough. FOT (R(0) and R(16)) and interruption (Rint) parameters were measured at baseline and after bronchodilator inhalation (n = 94). Rint was significantly lower than R(0), especially in children with high baseline values. Baseline parameters were normalized for height and weight [R(SD)]. In children able to perform forced expiratory maneuvers (n = 93), the best discrimination between those with baseline FEV(1) < 80% or > or = 80% of predicted values was obtained with R(0)(SD). At a specificity of 80%, R(0)(SD) yielded 66% sensitivity, whereas Rint(SD) yielded only 33% sensitivity. Similarly, postbronchodilator changes in R(0)(SD) [DeltaR(0)(SD)] yielded the best discrimination between children with and without significant reversibility in FEV(1). At a specificity of 80%, DeltaR(0)(SD) yielded 67% sensitivity and DeltaRint(SD) yielded 58% sensitivity. In children unable to perform forced expiratory maneuvers (n = 25), FOT, contrary to the interrupter technique, clearly identified a subgroup of young children with high resistance values at baseline, which returned to normal after bronchodilation. We conclude that, in asthmatic children over 3 yr old, FOT measurements provide a more reliable evaluation of bronchial obstruction and its reversibility compared with the interrupter technique, especially in young children with high baseline values.     

脉冲振荡法在支气管舒张试验中的应用价值

为探讨脉冲振荡法在支气管舒张试验中的应用价值 ,采用脉冲振荡法测定了 2 1例哮喘发作期患者吸入支气管舒张剂前后呼吸阻抗的变化及改善率 ,同时测定肺通气功能变化及改善率 ,并对两种方法所测结果进行对比及相关性分析。结果显示 ,吸入沙丁胺醇后 5 Hz和 2 0 Hz振荡频率时粘性阻力 ( R5、R2 0 )、5 Hz振荡频率时电抗( X5)及共振频率 ( Fres)与用药前比较均明显改善 ( P<0 .0 1) ,其中以 Fres改善最明显 ;一秒钟用力呼气容积( FEV1 )、最大峰流速 ( PEF)、5 0 %和 2 5 %肺活量最大呼气流速 ( V50 、V2 5)均明显改善 ( P<0 .0 1) ;呼吸阻抗改善率显著高于肺通气功能改善率 ( P<0 .0 5 ) ;吸药后 FEV1 增加与 Fres、R5和 X5变化相关密切 ,相关系数分别为0 .69、0 .4 8和 - 0 .4 2。认为 ,脉冲振荡法用于支气管舒张试验是诊断、鉴别诊断支气管哮喘及观察药物疗效的有用工具 ,值得临床推广使用     

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.     

The current single exhalation method of measuring exhales nitric oxide is affected by airway calibre.

The authors have observed that some patients with acute exacerbations of asthma do not have substantially higher levels of exhaled nitric oxide (NO). The study examined whether this could be explained by the effect of airway calibre on exhaled NO. Exhaled NO, height and forced expiratory volume in one second (FEV1) were measured in 12 steroid-naive asthmatics and 17 normal subjects. For comparison, another group of patients with airways disease (34 cystic fibrosis patients) were also studied. In 20 asthmatics (on various doses of inhaled steroids, 0-3,200 microg x day-1), exhaled NO was measured before and after histamine challenge (immediately after reaching the provocative concentration causing a 20% fall in FEV1) and in 12 of these patients, also after nebulized salbutamol to restore FEV1 to baseline. Studies were also conducted to examine possible confounding effects of repeated spirometry (as would occur in histamine challenge) and nebulized salbutamol alone in exhaled NO levels. Exhaled NO was measured using a single exhalation method with a chemiluminescence analyser at a constant flow rate and mouth pressure. There was a significant correlation between FEV1 and exhaled NO in steroid naive asthmatics (r=0.9, p<0.001) and cystic fibrosis patients (r=-0.48, p<0.05) but not in normal subjects (r=-0.13, p=0.61). Exhaled NO decreased significantly after histamine challenge and returned to baseline after bronchodilation by nebulized salbutamol (mean+/-SEM: 23.6+/-3.6 parts per billion (ppb) (prehistamine), 18.2+/-2.7 ppb (posthistamine) and 23.6+/-3.8 ppb (postsalbutamol) p=0.001). Repeated spirometry and nebulized salbutamol did not affect exhaled NO measurements significantly. Exhaled nitric oxide levels appear to be lower in circumstances of smaller airway diameter. Hence, within a subject nitric oxide levels may be artefactually decreased during bronchoconstriction. This may be caused by increased airflow velocity in constricted airways when the exhalation rate is kept constant.