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Biomedical subjects

N Zamel

Publications and source records attributed to N Zamel.

At least 55 records · Page 3Linked to original sources
PubMed1996

Tracheobronchial constriction in asthmatics induced by isocapnic hyperventilation with dry cold air.

Although it is well known that isocapnic hyperventilation (IHV) with dry cold air produces airway constriction in asthmatic subjects, the site of airway narrowing is nuclear. To address this issue, we have quantified the tracheal and bronchial response to IHV with dry cold air in 15 patients with mild asthma and 7 healthy control subjects. We employed the acoustic reflection technique to evaluate changes in airway cross-sectional areas caused by IHV with dry cold air. Airway areas were measured during tidal breathing before and 5 to 10, 30, 60, and 90 min following cold air challenge. For analysis purposes, airway areas were divided into three anatomic segments: extrathoracic tracheal segment, intrathoracic tracheal segment, and main bronchial segment. These segments were assessed at a fixed volume below total lung capacity. Maximal and partial expiratory flow-volume curves were also obtained before each set of area measurements. In normal subjects, IHV with dry cold air caused no significant changes in FEV1, flow at 30% of the vital capacity in the partial curve (V30p), or airway areas. In asthmatics, at 5 to 10 min after challenge, we found that FEV1 decreased by 22 +/- 5% (mean +/- SEM) (p < 0.0001), V30p by 33 +/- 8% (p < 0.003), intrathoracic tracheal area by 10.7% +/- 2% (p < 0.03), and main bronchial area by 14 +/- 3% (p < 0.003). At 30 min, tracheal and main bronchial areas were returned to baseline levels; however, FEV1 and V30p were still significantly decreased, by 13 +/- 3% and 16 +/- 4%, respectively. We conclude that in asthmatics, IHV with dry cold air causes both tracheal and bronchial constriction, and that recovery seems to occur first in the central airways.

Acoustics↗
PubMed1996

Lung function 12 months following emphysema resection.

OBJECTIVE: To investigate the mechanism of airflow limitation before and 6 and 12 months after targeted emphysematous resection in 10 male patients aged 67 +/- 8 years (mean +/- SD) with very severe COPD undergoing bilateral thoracoscopic stapling techniques. DESIGN: Lung function, including static lung elastic recoil, was measured 2 weeks before and 6 and 12 months after surgery. RESULTS: Twelve months after surgery, there was a significant (p < 0.001) reduction in total lung capacity (TLC), 9.5 +/- 0.3 L (mean +/- SEM) to 8.5 +/- 0.3 L, functional residual capacity, and residual volume. Airway conductance and FEV1, 0.71 +/- 0.1 L (mean +/- SEM) to 0.95 +/- 0.1 L, improved significantly (p < 0.01). Lung elastic recoil increased markedly at TLC from 11.7 +/- 0.7 cm H2O (mean +/- SEM) to 15.0 +/- 1.0 cm H2O (p < 0.01) as did maximum expiratory airflow in every patient. However, when compared with data obtained in each patient at 6 months, lung volumes are significantly increased, and expiratory airflow and lung elastic recoil pressures are significantly reduced (p < or = 0.05). Analysis of maximum expiratory flow-static elastic recoil pressure curve indicates conductance of the S airway segment (Gs) increased from 0.20 +/- 0.03 L/s/cm H2O (mean +/- SEM) to 0.28 +/- 0.04 L/s/cm H2O (p < 0.02), and critical transmural pressure in the collapsible segment (Ptm') decreased from 3.2 +/- 0.2 cm H2O (mean +/- SEM) to 2.5 +/- 0.2 cm H2O (p < 0.01). CONCLUSION: The improvement in maximal expiratory airflow can be attributed primarily to increased lung elastic recoil and its secondary effect on enlarging airway diameter causing increased airway conductance, increased Gs, and decreased Ptm'. The improvement in lung function and elastic recoil peaks at 6 months.

Aged↗
PubMed1995

Acoustic rhinometry in the evaluation of nasal obstruction.

Acoustic rhinometry (AR) is a recently developed objective technique for assessment of geometry of the nasal cavity. The technique is based on the analysis of sound waves reflected from the nasal cavities. It measures cross-sectional areas and nasal volume (NV). To obtain dependable assessments of nasal resistance by rhinomanometry or cross-sectional area measurements by AR, it is essential that the structural relations of the compliant vestibular region remain undisturbed by the measuring apparatus. The use of nozzles in making these measurements carries a great risk of direct distortion of the nasal valve. We used a nasal adapter that does not invade the nasal cavity and a chin support that stabilizes the head. In 51 healthy nasal cavities, the average minimum cross-sectional area (MCA) was 0.62 cm2 at 2.35 cm from the nostril and 0.67 cm2 at 2 cm from the nostril, respectively, before and after topical decongestion of the nasal mucosa. The MCA and NV findings in this group were significantly higher than MCA and NV (P < 0.001) in people with structural or mucosal abnormalities before mucosal decongestion. After mucosal decongestion, the MCA and NV were significantly higher in healthy nasal cavities than in nasal cavities with structural abnormalities (P < 0.001) but were not higher than nasal cavities with mucosal abnormalities (MCA, P = 0.05; NV, P = 0.06). A nozzle was applied in 20 healthy nasal cavities after mucosal decongestion, and a significantly higher MCA was found compared to measurements made with the nasal adapter (P = 0.02). We conclude that the nasal adapter, which does not invade the nasal cavities, avoids the distortion of the nasal valve and gives more accurate results.

Acoustics↗
PubMed1994

Changes in pulmonary function and cross-sectional area of trachea and bronchi in asthmatics following inhalation of procaterol hydrochloride and ipratropium bromide.

To determine the sites of action of inhaled adrenergic and anticholinergic bronchodilators, we used the acoustic reflection technique to measure airway area before and after administration of beta 2-selective adrenoreceptor agonist (procaterol hydrochloride) and quaternary anticholinergic agent (ipratropium bromide). Eight stable individuals with asthma (five men and three women; mean age, 34 +/- 12.7 yr) were studied on 2 days in single-blind randomized crossover fashion when they self-administered (using metered-dose inhaler) two puffs of either procaterol hydrochloride hemihydrate (10 micrograms/puff) or ipratropium bromide (20 micrograms/puff). Maximal expiratory flow-volume curve, specific airway resistance, and cross-sectional areas of three airway segments (extrathoracic tracheal, intrathoracic tracheal, and bronchial) were recorded at baseline and 15, 30, 60, and 120 min after drug administration. Both agents produced significant improvements in FEV1, FVC and forced expiratory flow at 50% of vital capacity (V50), and specific airway resistance (SRaw) as early as 15 min after drug administration. These effects were sustained for the 120 min monitoring period. However, all improvements were significantly greater for procaterol than for ipratropium. By contrast, there was no significant difference between drugs in the increased production in the cross-sectional areas of the three airway segments although there was a nonsignificant trend toward greater increases in tracheal area produced by the anticholinergic agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustics↗
PubMed1994

The effect of pre-exposure to 0.12 ppm of ozone on exercise-induced asthma.

Ozone (O3) is a common air pollutant that has been associated with a dose-dependent increased bronchial responsiveness and airway inflammation. Previous investigations have shown increased airway responsiveness to allergens in asthmatics pre-exposed to 0.12 ppm of O3 for 1 h. In the present study, we investigated whether inhalation of relatively low levels of O3 would modify the degree of exercise-induced bronchoconstriction. We studied 15 "never smokers" with mild stable asthma (7 male and 8 female) (mean age [+/- SD] 25.6 +/- 6.8 years) who had exhibited a fall in FEV1 > 15 percent after a standard 6-min treadmill exercise challenge test on the screening day. This was a double-blind, placebo-controlled study. The patients were randomized to receive either O3 or air (placebo) before performing the exercise challenge again. The average highest 1-h daily O3 concentrations in Toronto during O3 days and air days were 0.017 +/- 0.017 and 0.014 +/- 0.005 ppm, respectively. The O3 concentration inside the chamber averaged 0.122 +/- 0.005 ppm on O3 days and 0.002 +/- 0.001 on placebo days. Partial and complete flow volume curves were done before and after this exposure, and also 5, 10, 15, 20, 30, and 60 min postexercise. The percent fall in FEV1 on the O3 chamber day and on the air chamber day was the same (F = 0.67, p = 0.67, NS) as well as the percent fall in V40p (F = 0.91, p = 0.49, NS). A repeated measures analysis of variance to test the effects of exposure on the time course of the airway response after exercise showed no significant difference between the 2 days. There was also no significant difference in maximal percentage fall in FEV1 (25.6 +/- 8.6) or V40p (62.2+18.6) following O3 exposure, and FEV1 (26.8 +/- 9.4)(p = 0.64) or V40p (65.3+4.31)(p = 0.60) following air. Our data indicate that previous exposure at rest to a concentration of O3 that has previously been shown to augment the bronchoconstriction response to allergens did not increase the bronchoconstriction response to subsequent exercise nor did it change the time course of such bronchoconstriction.

Adult↗
PubMed1994

Acoustic rhinometry, rhinomanometry, and the sensation of nasal patency: a correlative study.

Acoustic rhinometry and rhinomanometry were used to evaluate the relationship between nasal cross-sectional areas, nasal resistances, and sensations of nasal patency. These parameters were measured before and after topical application of a nasal decongestant in 78 patients suffering from nasal obstruction. As subjects breathed voluntarily through both nasal cavities, no significant correlation was found between sensation of nasal patency and combined nasal minimum cross-sectional areas (r = .11) or of total airflow resistance (r = -.11) either before or after decongestion. However, when subjects were required to breathe through each nasal cavity separately, a significant correlation was found between ipsilateral sensation of nasal patency and both ipsilateral minimum cross-sectional area pre-decongestion (r = -.53, p < .0001) and post-decongestion (r = -.22, p < .01), and airflow resistance pre-decongestion (r = .42, p < .0001) and post-decongestion (r = .25, p < .01). A significant, negative, nonlinear relationship was also found between nasal minimum cross-sectional area and nasal resistance. Furthermore, acoustic rhinometry demonstrated that small intrusions into the lumen of the nose that might be missed by rhinoscopy produce an exponentially greater increase in nasal resistance measurements by rhinomanometry. The findings were most striking in the valve region. It is concluded that each of these objective and complementary measurement techniques provides a more reliable assessment of nasal patency than subjective evaluation by either patient or clinician and can thus provide valuable guidance in management of the symptom of nasal obstruction.

Acoustics↗
PubMed1993

Tracheobronchial dilation during isocapnic hypoxia in conscious humans.

To assess the effects of isocapnic hypoxia on the pharynx, glottis, extrathoracic trachea (ET), intrathoracic trachea (IT), and main bronchi (MB), we measured the cross-sectional areas of these airways by acoustic reflection technique in 15 healthy volunteers. Measurements were made during tidal volume breathing while subjects were normoxic [arterial O2 saturation (SaO2) > 95%] or were made hypoxic by a rebreathing procedure. Under hypoxemic conditions, airway cross-sectional areas increased significantly at ET, IT, and MB levels (P < 0.001). The magnitude of this dilation was similar for both levels of hypoxemia studied (SaO2 80-85% and 70-75%); at the milder of the two hypoxemic conditions, ET cross-sectional area increased by 12.4 +/- 4.2% (SE), IT by 10.2 +/- 5.9%, and MB by 19.1 +/- 3.2%. No significant changes were found in the pharyngeal or glottic areas. Dilation was not produced by normoxic isocapnic hyperventilation, and the use of hypoxic airway gas mixtures did not artifactually alter acoustic reflection measurements in a mechanical model. Vagal airway tone, as reflected by airway constriction during pauses in tidal breathing, was unaffected by isocapnic hypoxia. We conclude that isocapnic hypoxia produces dilation of the trachea and major bronchi, an effect unaccounted for by an alteration in the ventilatory pattern.

Adult↗
PubMed1993

Limited contribution of emphysema in advanced chronic obstructive pulmonary disease.

Previous studies on autopsy specimens or surgically resected lobes or lungs have reached varying conclusions regarding the importance of small airways disease and emphysema in causing fixed expiratory airflow limitation in patients with chronic obstructive pulmonary disease (COPD). We obtained high resolution CT scans of the lung and lung function in 56 consecutive patients with fixed expiratory airflow limitation. There was poor correlation between CT emphysema score and either FEV1/FVC% (r = -0.36) or FEV1 % predicted (r = -0.20). In only 10 of the 35 patients with FEV1 < 50% predicted, the CT emphysema score was > 40, indicating significant emphysema. A strong negative correlation between diffusing capacity % predicted and diffusing capacity per alveolar volume and CT emphysema score was found only in patients with FEV1 > or = 1 L (r = -0.75, p < 0.0001). Thus, emphysema does not appear to be primarily responsible for expiratory airflow limitation in COPD. A low diffusing capacity may be spuriously misleading in patients with FEV1 < 1 L and no or trivial emphysema.

Aged↗
PubMed1993

Assessment of airway tone in asthma. Comparison between double lung transplant patients and healthy subjects.

We investigated the hypothesis that asthmatic patients have an increased cholinergic tone by measuring tracheobronchial cross-sectional areas during transient voluntary apnea. This allowed us to assess bronchomotor tone without the influence of changes in lung recoil or lung volume. Three groups of subjects with potentially different levels of tracheobronchial tone were studied: 14 healthy volunteers (N), 18 stable asthmatic patients (A), and 10 double lung transplant recipients (T). Using the acoustic reflection technique, we measured changes in tracheobronchial cross-sectional areas during short periods (5 to 10 s) of voluntary apnea. In a subset of subjects, studies were repeated before and after the inhalation of the muscarinic antagonist ipratropium. During breath-holding, glottis and extrathoracic trachea remained unchanged but intrathoracic tracheal area decreased by 30 +/- 8% (mean +/- standard error of the mean) in N, by 27 +/- 3% in A, and by 9 +/- 4% in the T group. Bronchial areas decreased by 24 +/- 8% in N, by 45 +/- 3% in A, and by 10 +/- 4% in T. These differences among groups were statistically significant at the tracheal and bronchial levels (p < 0.05), and ipratropium significantly inhibited this airway constriction (p < 0.05) only in the asthmatic group. Assuming that changes in cross-sectional airway areas voluntary apnea reflect airway tone, these results support the view that in humans this tone is mainly vagally controlled and that it is significantly increased in asthmatic compared with nonasthmatic subjects.

Administration, Inhalation↗
PubMed1993

Reduction of lung diffusion for carbon monoxide in patients with lung carcinoma.

A retrospective study to investigate the prevalence and severity of impairment of the lung diffusing capacity for carbon monoxide (DCO) in patients with lung carcinoma was done using a case-control matched design. A group of 70 patients with the histologic diagnosis of lung carcinoma was matched on a one-to-one basis with a group of patients with chronic bronchitis and/or pulmonary emphysema (COPD); the matching was done based on the FEV1 within 10 percent of each other for all pairs. The groups of lung carcinoma and COPD had similar history of smoking consumption and pulmonary function, except that the Dco was reduced in the carcinoma group (mean +/- SD: 56.4 +/- 12.8 percent of predicted) compared with the control group (64.4 +/- 20.1 percent of predicted; p = 0.0027). Among the carcinoma group, only one patient had a Dco above 75 percent of the predicted value, while in the control group, 22 patients had a Dco above 75 percent of predicted values. It appears that Dco is more frequently reduced in patients with lung carcinoma than in a group of patients with similar FEV1 and smoking history who have chronic bronchitis and/or emphysema but had no evidence of lung carcinoma. We speculate that the reduction of Dco in patients with lung carcinoma could be due to the concurrent presence of pulmonary emphysema.

Aged↗
PubMed1992

Heterogeneous airway tone in asthmatic subjects.

We examined the effect of volume history on the dynamic relationship between airways and lung parenchyma (relative hysteresis) in 20 asthmatic subjects. The acoustic reflection technique was employed to evaluate changes in airway cross-sectional areas during a slow continuous expiration from total lung capacity to residual volume and inspiration back to total lung capacity. Lung volume was measured continuously during this quasi-static maneuver. We studied three anatomic airway segments: extra- and intrathoracic tracheal and main bronchial segments. Plots of airway area vs. lung volume were obtained for each segment to assess the relative magnitude and direction of the airway and parenchymal hysteresis. We also performed maximal expiratory flow-volume and partial expiratory flow-volume curves and calculated the ratio of maximal to partial flow rates (M/P) at 30% of the vital capacity. We found that 10 subjects (group I) showed a significant predominance of airway over parenchymal hysteresis (P < 0.005) at the extra- and intrathoracic tracheal and main bronchial segments; these subjects had high M/P ratios [1.53 +/- 0.27 (SD)]. The other 10 subjects (group II) showed similar airway and parenchymal hysteresis for all three segments and significantly lower M/P ratios (1.16 +/- 0.20, P < 0.01). We conclude that the effect of volume history on the relative hysteresis of airway and lung parenchyma and M/P ratio at 30% of vital capacity in nonprovoked asthmatic subjects is variable. We suggest that our findings may result from heterogeneous airway tone in asthmatic subjects.

Adolescent↗
PubMed1992

Maximal exercise testing in single and double lung transplant recipients.

Patients with end-stage pulmonary and pulmonary vascular disease can now be offered single-lung (SLT), double-lung (DLT), or heart-lung (HLT) transplantation. Long-term survival with greatly improved pulmonary function has been reported with all three procedures. Little has been reported of the exercise capacity after transplantation. This report documents Stage 1 exercise test results in six SLT (five males and one female; age 50.7 +/- 4.4; FEV1.0 75.5 +/- 6.7% of predicted) and seven DLT (three males and four females; age 37.3 +/- 6.7; FEV1.0 85.1 +/- 10.3% of predicted) recipients, early (3 months) and late (1 to 2 yr) following transplantation. The results show low work rates and VO2max in both SLT and DLT recipients at 3 months after transplant. Heart rate and minute ventilation did not appear limiting. There was no significant improvement when retested 1 to 2 yr after transplant. At 3 months, VO2max was 46% of predicted for SLT and 50% of predicted for DLT recipients. It is concluded that considerable exercise limitation persists after transplantation and does not appear to improve with time. These limitations are similar for both SLT and DLT and are not related to ventilation. The results may suggest chronic muscle deconditioning after long-term pretransplant debilitation.

Adult↗
PubMed1992

Changes in cross-sectional airway areas induced by methacholine, histamine, and LTC4 in asthmatic subjects.

To examine whether leukotrienes, histamine, and methacholine have different sites of bronchoconstrictor action, we studied 8 stable asthmatic subjects (mean age +/- SD, 26 +/- 5 yr) on 3 different days. On each day, a randomized challenge with LTC4, methacholine, or histamine was performed until the dose that provoked a fall of 20% in FEV1 (PC20) was obtained. Complete and partial flow-volume curves as well as area-distance profiles generated by the acoustic reflection technique (ART) at a fixed lung volume were obtained in all subjects before and after each inhalation challenge. No significant differences were found in pulmonary function or baseline cross-sectional airway areas for the different study days. The three agonists provoked significant (p less than 0.05) bronchoconstriction at the level of the main bronchi when identical falls of FEV1 were achieved. Similarly, equal reductions of V30p were elicited by the three agonists. However, LTC4 and methacholine induced additional tracheal constriction but histamine inhalation did not. These differences in the degree of tracheal constriction were statistically significant (p less than 0.05; ANOVA). These results may be explained by distinct pharmacologic properties of the agents used and may have relevance in the understanding of the pathophysiology of asthma.

Analysis of Variance↗
PubMed1992

Physiologic studies of tracheobronchial stents in airway obstruction.

When airway obstruction is due to extraluminal compression and/or dynamic collapse, metal and silicone rubber prosthetic stents may stabilize the affected airway. Through a rigid bronchoscope, we inserted three metal stents in two patients and 18 silicone stents in 15 adult patients with symptomatic tracheobronchial compression and dynamic airway collapse. The underlying cause was malignancy in three patients; benign tracheobronchial malacia in three patients, two of whom refused surgical resection; and tracheobronchial stenosis that developed at the anastomotic site following lung transplantation in 11 patients. Clinical status and lung function studies were analyzed before and after stent insertion. Following stent insertion, airway diameter at least doubled and near normal patency of the affected tracheobronchial tree was achieved in every patient using stents of axial length 4 to 5 cm. The stents were well tolerated clinically, and all patients noted immediate relief of dyspnea. Following stent insertion, the forced vital capacity (FVC) increased from 64 +/- 21% predicted (mean +/- 1 SD) to 73 +/- 19% predicted, p less than 0.1; the forced expiratory volume in 1 s (FEV1) from 49 +/- 25% predicted to 72 +/- 26% predicted, p less than 0.02; the ratio of the FEV1/FVC from 59 +/- 16% to 78 +/- 15%, p less than 0.01; and the maximum flow at 50% expired FVC from 38 +/- 26% predicted to 72 +/- 31% predicted, p less than 0.01.

Adult↗