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Sylvia Verbanck

Publications and source records attributed to Sylvia Verbanck.

12 recordsLinked to original sources
PubMed2005

Effects of methacholine on small airway function measured by forced oscillation technique and multiple breath nitrogen washout in normal subjects.

The multiple breath nitrogen washout (MBNW) can be analysed to produce the parameters Scond and Sacin as measures of ventilation heterogeneity in conductive and acinar airways, respectively. The derivation of these parameters is based on a model of pulmonary ventilation and results of similar modelling suggest that respiratory system conductance (Grs) measured by forced oscillation technique (FOT) is also sensitive to heterogeneity and to airway closure. Therefore, Scond, the volume of gas trapping at FRC (VtrappedFRC) and Grs may be inter-related parameters. These relationships were examined in 12 normals under baseline and bronchoconstricted states. Specific Grs was measured at 5Hz (sGrs5=Grs5/FRC) and Scond, Sacin and VtrappedFRC by MBNW, before and after methacholine challenge. Scond was independently predicted by VtrappedFRC and FRC in a multivariate model (R2=0.68, p=0.002). Post methacholine challenge, Scond related only to VtrappedFRC (R2=0.79, p<0.0001). The absolute change in Scond induced by methacholine challenge were predicted by the changes in VtrappedFRC and sGrs5 in a multivariate model (R2=0.82, p=0.0002). Sacin was unrelated to VtrappedFRC and sGrs5 before and after methacholine challenge. In conclusion, Scond and sGrs5 are measurements that are sensitive to changes occurring to the function of peripheral conducting airways, in particular heterogeneity and airway closure, while Sacin and presumably heterogeneity in terminal airways, are independent of these. Scond is also related to lung size. We review the current state of knowledge of FOT and MBNW in obstructive lung diseases and discuss future research directions.

Adult↗
PubMed2005

Monitoring the lung periphery of transplanted lungs.

Lung transplantation is now accepted as a viable therapeutic option for patients with end-stage lung diseases, but long-term survival is threatened by bronchiolitis obliterans (BO), which is regarded as a manifestation of chronic allograft rejection. We have used studies of ventilation distribution for the early detection of this complication. In a prospective study of 57 bilateral-lung transplant recipients, we showed that the slope of phase III of the helium single-breath washout, which targets inhomogeneities of ventilation distribution in the terminal and respiratory bronchioles, was particularly sensitive to the development of BO. In a preliminary study using nitrogen multiple-breath washouts, we showed that S(acin) and S(cond), which reflect structural changes in the acinar and conductive lung zones, were both markedly increased in patients with BO. Taken together, these studies demonstrate that monitoring the function of the allograft by measuring the distribution of ventilation in the lung periphery may be a clinically valuable tool.

Adult↗
PubMed2005

Airway closure in microgravity.

Recent single breath washout (SBW) studies in microgravity and on the ground have suggested an important effect of airway closure on gas mixing in the human lung, reflected particularly in the phase III slope of vital capacity SBW and bolus tests. In order to explore this effect, we designed a SBW in which subjects inspired 2-l from residual volume (RV) starting with a 150 ml bolus of He and SF6. In an attempt to vary the pattern of airways closure configuration before the test, the experiments were conducted in 1G and in microgravity during parabolic flight allowing the pre-test expiration to RV to be either in microgravity or at 1.8 G, with the actual test gas inhalation performed entirely in microgravity. Contrary to our expectations, the measured phase III slope and phase IV height and volume obtained from seven subjects in microgravity were essentially identical irrespective of the gravity level during the pre-test expiration to RV. The results suggest that airway closure configuration at RV before the test inspiration has no apparent impact on phases III and IV generation.

Closing Volume↗
PubMed2005

Foreword.

Explore the source record for details and available documents.

Animals↗
PubMed2005

FEV1/FEV6 and FEV6 as an alternative for FEV1/FVC and FVC in the spirometric detection of airway obstruction and restriction.

STUDY OBJECTIVES: To evaluate the use of the FEV(1)/forced expiratory volume at 6 s of exhalation (FEV(6)) ratio and FEV(6) as an alternative for FEV(1)/FVC and FVC in the detection of airway obstruction and lung restriction, respectively. SETTING: Pulmonary function laboratory of the Academic Hospital of the Free University of Brussels. PARTICIPANTS: A total of 11,676 spirometric examinations were analyzed on subjects with the following characteristics: white race; 20 to 80 years of age; 7,010 men and 4,666 women; and able to exhale for at least 6 s. METHODS: Published reference equations were used to determine lower limits of normal (LLN) for FEV(6), FVC, FEV(1)/FEV(6), and FEV(1)/FVC. We considered a subject to have obstruction if FEV(1)/FVC was below its LLN. A restrictive spirometric pattern was defined as FVC below its LLN, in the absence of obstruction. From these data, sensitivity and specificity of FEV(1)/FEV(6) and FEV(6) were calculated. RESULTS: For the spirometric diagnosis of airway obstruction, FEV(1)/FEV(6) sensitivity was 94.0% and specificity was 93.1%; the positive predictive value (PPV) and negative predictive value (NPV) were 89.8% and 96.0%, respectively. The prevalence of obstruction in the entire study population was 39.5%. For the spirometric detection of a restrictive pattern, FEV(6) sensitivity was 83.2% and specificity was 99.6%; the PPVs and NPVs were 97.4% and 96.9%, respectively. The prevalence of a restrictive pattern was 15.7%. Similar results were obtained for male and female subjects. When diagnostic interpretation differed between the two indexes, measured values were close to the LLN. CONCLUSIONS: The FEV(1)/FEV(6) ratio can be used as a valid alternative for FEV(1)/FVC in the diagnosis of airway obstruction, especially for screening purposes in high-risk populations for COPD in primary care. In addition, FEV(6) is an acceptable surrogate for FVC in the detection of a spirometric restrictive pattern. Using FEV(6) instead of FVC has the advantage that the end of a spirometric examination is more explicitly defined and is easier to achieve.

Adult↗
PubMed2004

Fluorescein-enhanced autofluorescence thoracoscopy in primary spontaneous pneumothorax.

The exact site of air leakage in a patient with primary spontaneous pneumothorax is difficult to determine and locate. In particular, the role of rupture of emphysema-like changes (blebs and bullae) versus that of enhanced porosity of lung parenchyma in the pathophysiology of primary spontaneous pneumothorax remains unclear. This is the first description of a patient with recurrent primary spontaneous pneumothorax in whom inhalation of aerosolized fluorescein followed by autofluorescence thoracoscopy allowed in vivo localization of various lung areas of extensive subpleural fluorescein accumulation which were not, or only partly, visibly abnormal during normal white light thoracoscopy. No air leak was present at the time of thoracoscopy. No emphysema-like changes were seen. Our findings suggest substantial areas of parenchymal abnormality that remain unnoticed by white light thoracoscopic inspection of the parenchymal surface. In this respect, fluorescein-enhanced autofluorescence thoracoscopy may become an exciting tool in the study of the pathophysiology of primary spontaneous pneumothorax, and could prove useful in clinical practice in determining the sites of surgical staple resection whenever this treatment modality is considered.

Administration, Inhalation↗
PubMed2004

Noninvasive assessment of airway alterations in smokers: the small airways revisited.

It has been shown that structural changes in small airways of smokers with average smoking histories greater than 35 pack-years could be reflected in the single-breath washout test. The more sophisticated multiple breath washout test (MBW) has the potential to anatomically locate the affected small airways in acinar and conductive lung zones through increased phase III slope indices S(acin) and S(cond), respectively. Pulmonary function, S(acin), and S(cond) were obtained in 63 normal never-smokers and in 169 smokers classified according to smoking history (< 10 pack-years; 10-20 pack-years; 20-30 pack-years; > 30 pack-years). Compared with never-smokers, significant changes in S(acin) (p = 0.02), S(cond) (p < 0.001), and diffusing capacity (DL(CO); p < 0.001) were detected from greater than 10 pack-years onwards. Spirometric abnormality was significant only from greater than 20 pack-years onwards. In smokers with greater than 30 pack-years and DL(CO) less than 60% predicted, the presence of emphysema resulted in disproportionally larger S(acin) than S(cond) increases. We conclude that S(cond) and S(acin) can noninvasively detect airway changes from as early as 10 pack-years onwards, locating the earliest manifestations of smoking-induced small airways alterations around the acinar entrance. In these early stages, the associated DL(CO) decrease may be a reflection of ventilation heterogeneity rather than true parenchymal destruction. In more advanced stages of smoking-induced lung disease, differential patterns of S(acin) and S(cond) are characteristic of the presence of parenchymal destruction in addition to peripheral airways alterations.

Breath Tests↗
PubMed2004

Aerosol profile extracted from spacers as a determinant of actual dose.

PURPOSE: We propose a novel method to evaluate the efficacy of a pressurized metered dose inhaler (pMDI) in combination with a spacer, by not only considering the total dose extractable from the spacer but also the dependence of dose on the volume available for aerosol inhalation. METHODS: We studied volume-dependence of aerosol concentration during extraction from two commonly used plastic spacers (150 ml AerochamberPlus; 750 ml Volumatic) after a single puff of a 100 microg salbutamol pMDI (HFA-Ventolin), using laser photometric measurements. RESULTS: After a delay of is in each spacer, the aerosol peak dose for AerochamberPlus was 2-fold that for Volumatic (p < 0.001), with the peak appearing well within the first 0.5 L even for the largest spacer. The opposite dose relationship is reached when considering total cumulative dose, which was 2-fold higher for Volumatic than for AerochamberPlus (p < 0.001); >95% of total cumulative dose was extracted well within 3 L for the largest spacer. The 2-fold cumulative dose relationship was confirmed by chemical assay on an absolute filter [AerochamberPlus: 21.4+/-3.2 (SD) microg; Volumatic: 43.8+/-9.1 (SD) microg]. CONCLUSIONS: Actual aerosol dose available to patients during inhalation via spacers can only be done on the basis of a quantification of aerosol peak dose and cumulative dose as a function of extracted volume.

Administration, Inhalation↗
PubMed2004

A comparison of two methods for measuring airway distensibility: nitrogen washout and the forced oscillation technique.

The measurement of airway stiffness is an important tool for studying airway remodelling in asthma. The relationship between airway calibre and lung volume (airway distensibility) was measured by forced oscillation technique (FOT) and compared with that measured by single-breath nitrogen washout (SBNW). In four non-asthmatic healthy subjects and three asthmatics, anatomical dead space (VDF) was measured by SBNW and respiratory system conductance (Grs) was measured by FOT at 6 Hz. During SBNW testing, 0.51 oxygen boluses were inhaled from three different lung volumes: functional residual capacity (FRC), 11 above FRC and near total lung capacity (TLC). Following inhalation of the oxygen bolus subjects exhaled to residual volume and then inhaled to TLC. During FOT, subjects breathed 0.5-1.01 tidal volumes but with gradually increasing end-expiratory lung volume until close to TLC, then returned to normal breathing before inhaling to TLC. This was also repeated but with reducing lung volume from TLC. Absolute lung volumes were measured by body plethysmography and related to volumes during FOT and SBNW by reference to TLC obtained at the end of each SBNW or FOT test manoeuvre. Distensibility was calculated as the linear regression slopes of VDF or Grs versus lung volume. Distensibility measured by VDF ranged 16-37 ml 1(-1) lung volume and by Grs it ranged 0.06-0.19 1 s(-1) cmH2O(-1) 1(-1) lung volume. Both distensibility measurements were correlated (Pearson's R2 = 0.91, p = 0.001). The SBNW and FOT are comparable methods for measuring airway distensibility and may have similar clinical usefulness. However, further studies are required to make any specific inferences about the relationship between airway distensibility by FOT and airway remodelling.

Administration, Inhalation↗
PubMed2002

Nonreversible conductive airway ventilation heterogeneity in mild asthma.

A multiple-breath washout technique was used to assess residual ventilation heterogeneity in the conductive and acinar lung zones of asthmatic patients after maximal beta(2)-agonist reversibility. Reversibility was assessed in 13 patients on two separate visits corresponding to a different baseline condition in terms of forced expiratory volume in 1 s [FEV(1); average FEV(1) over 2 visits: 92 +/- 21% of predicted (SE)]. On the visit corresponding to each patient's best baseline, 400 micro g salbutamol led to normal acinar ventilation heterogeneity, normal FEV(1), and normal peak expiratory flow; i.e., none was significantly different from that obtained in 13 matched controls. By contrast, conductive ventilation heterogeneity and forced expiratory flow after exhalation of 75% forced vital capacity remained significantly different from controls (P < or = 0.005 on both indexes). In addition, the degree of postdilation conductive ventilation heterogeneity was similar to what was previously obtained in asthmatic individuals with a 19% lower baseline FEV(1) and twofold larger acinar ventilation heterogeneity (Verbanck S, Schuermans D, Noppen M, Van Muylem A, Paiva M, and Vincken W. Am J Respir Crit Care Med 159: 1545-1550, 1999). We conclude that, even in the mildest forms of asthma, the most consistent pattern of non-beta(2)-agonist-reversible ventilatory heterogeneity is in the conductive lung zone, most probably in the small conductive airways.

Adrenergic beta-Agonists↗
PubMed2002

Tidal volume single-breath washin of SF6 and CH4 in transient microgravity.

We performed tidal volume single-breath washins (SBW) by using tracers of different diffusivity and varied the time spent in microgravity (microG) before the start of the tests to look for time-dependent effects. SF(6) and CH(4) phase III slopes decreased by 35 and 26%, respectively, in microG compared with 1 G (P < 0.05), and the slope difference between gases disappeared. There was no effect of time in microG, suggesting that neither the hypergravity period preceding microG nor the time spent in microG affected gas mixing at volumes near functional residual capacity. In previous studies using SF(6) and He (Lauzon A-M, Prisk GK, Elliott AR, Verbanck S, Paiva M, and West JB. J Appl Physiol 82: 859-865, 1997), the vital capacity SBW showed an increase in slope difference between gases in transient microG, the opposite of the decrease in sustained microG. In contrast, tidal volume SBW showed a decrease in slope difference in both microG conditions. Because it is only the behavior of the more diffusive gas that differed between maneuvers and microG conditions, we speculate that, in the previous vital capacity SBW, the hypergravity period preceding the test in transient microG provoked conformational changes at low lung volumes near the acinar entrance.

Adult↗