Pressure oscillations after flow interruption in relation to lung mechanics

The value of interrupter resistance measurements has been questioned because these depend on equilibration between alveolar (PA) and mouth pressure (PAO), which may not occur during airway obstruction or in measurements in children. In order to determine whether airway geometry and its interaction with the lung volume can be obtained without complete pressure equilibration, the postocclusional oscillatory airway opening pressure transients PAO(t) after flow interruption were studied in comparison to airway resistance (RAW), lung volumes (TGV, VC) and MEF50 in 9 healthy children (7-14 y) and 5 adults (28-37 y) in both time and frequency domains. The frequency of pressure oscillations was correlated to TGV (p < 0.01). Its damping properties (d) were correlated to MEF50 (p < 0.005). Performing airflow interruptions in the same subject showed that d increased at low lung volumes. During bronchial challenge test, d significantly increased with carbachol and decreased with salbutamol, whereas the frequency decreased with carbachol and increased with salbutamol. Therefore, the analysis of postocclusional pressure oscillations can be used to assess relative changes in airway mechanics and its interaction with lung volume during bronchial challenge tests in patients such as children with poor cooperation.

Neurotrophin and neurotrophin receptors in vascular smooth muscle cells. Regulation of expression in response to injury

The neurotrophins, a family of related polypeptide growth factors including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin (NT)-3 and NT-4/5 promote the survival and differentiation of distinctive sets of embryonic neurons. Here we define a new functional role for neurotrophins, as autocrine or local paracrine mediators of vascular smooth muscle cell migration. We have identified neurotrophins, and their cognate receptors, the trk tyrosine kinases, in human and rat vascular smooth muscle cells in vivo. In vitro, cultured human smooth muscle cells express BDNF; NT-3; and trk A, B, and C. Similarly, rat smooth muscle cells expressed all three trk receptors as well as all four neurotrophins. Moreover, NGF induces cultured human smooth muscle cell migration at subnanomolar concentrations. In the rat aortic balloon deendothelialization model of vascular injury, the expression of NGF, BNDF, and their receptors trk A and trk B increased dramatically in the area of injury within 3 days and persisted during the formation of the neointima. In human coronary atherosclerotic lesions, BDNF, NT-3, and NT-4/5, and the trk B and trk C receptors could be demonstrated in smooth muscle cells. These findings suggest that neurotrophins play an important role in regulating the response of vascular smooth muscle cells to injury.

Interrelationship between postocclusional oscillatory pressure transients and standard lung function in healthy and asthmatic children

We studied the correlation between characteristics of the postocclusional oscillatory airway opening pressure transients after flow interruption and body height, the degree of pulmonary hyperinflation [measured by thoracic gas volume (TGV)], and the degree of airway obstruction [measured by airway resistance (Raw)] and maximal expiratory flow at 50% vital capacity (MEF50) in 10 healthy and 50 asthmatic children age 7-16 years. Focusing on the damped oscillatory change in pressure, the first derivative of the shutter curve was analyzed, featuring a natural frequency fO and damping factor d in the time domain, and frequency FFS and power AFS in the frequency domain. A maximal frequency was found at approximately 80 Hz without a two peak distribution as described in dogs. Multiple linear forward step analysis revealed that omega O (the undamped, natural frequency) and AFS were related to body height (P < 0.001). The damping factor d (independent of body height) was related to TGV and MEF50 (P < 0.001), and FFS to Raw (P < 0.001). The analysis of the postocclusional pressure transients after airflow interruption provides information on the resistive, elastic and inertive properties of the thoraco-pulmonary system. The measurements obtained are influenced by the end-expiratory resting level (or the degree of pulmonary hyperinflation) and the degree of airway obstruction.

Cystic fibrosis mutations and immotile cilia syndrome

The immotile cilia syndrome (ICS) presents with autosomal recessive inheritance and is a chronic respiratory disease supposed to be caused by different genetic determinants. The hypothesis that cystic fibrosis (CF) heterozygotes may have a predisposition to develop bronchial or respiratory diseases other than CF prompted us to look for CF mutations in patients with ICS. Five patients, as well as the parents and two healthy brothers of one patient were tested for 12 CF mutations, for the polymorphic GATT repeat in intron 6a and for the CF gene flanking markers XV-2c, KM19, MP6d-9, J3.11. None of the 12 mutations at the CF locus have been detected in the ICS patients and no linkage was found between ICS and the polymorphic markers. Thus, based on our data, ICS and CF seem to be two different clinical entities.

Plethysmographic measurements in the clinical assessment of infants with bronchopulmonary disease

Whole-body plethysmography makes it possible, to measure, during the same test sequence, the end-expiratory resting level (thoracic gas volume (TGV)), and, hence, an estimate of lung volume, and its close inter-relationship to airway function (airway resistance (Raw), or its reciprocal value airway conductance (Gaw). An overview is given of the physiological background and some equipment required for this technique. Furthermore, the attractive usefulness of whole-body plethysmography in clinical routine is discussed. Based on plethysmographic data obtained in 118 infant survivors of respiratory distress syndrome (RDS), in wheezy infants and infants with cystic fibrosis (CF), the important inter-relationship between changes in end-expiratory resting level (TGV) and the deficit in airway mechanics (Gaw) is shown, and special emphasis is given to the absolute need to obtain these measurements simultaneously. It can be shown that this recommendation is of even greater clinical importance in view of the fact that the younger the child the more frequent and severe the pulmonary hyperinflation present. Finally, this inter-relationship has to be borne in mind when reversibility of functional abnormalities on adrenoceptor agonists is assessed by lung function measurements.

Chronic metabolic alkalosis: not uncommon in young children with severe cystic fibrosis

The acid-base balance of 199 patients with cystic fibrosis, seen from 1987 through 1992 at the Bern Outpatient Clinic, were evaluated. Simple metabolic alkalosis was demonstrated in 16 and mixed metabolic alkalosis and respiratory acidosis in 9 patients. When compared with 10 patients with simple respiratory acidosis and 16 with normal hydrogen ion balance, those with simple metabolic alkalosis were significantly younger. The need for pancreatic enzymes was significantly higher and the relative underweight significantly more severe in patients with either simple or mixed metabolic alkalosis and respiratory acidosis. The results indicate the rather common occurrence of chronic metabolic alkalosis in cystic fibrosis. It is observed in young patients, in patients who need high doses of pancreatic enzymes and in the those with poor nutritional status.

The age at onset of chronic Pseudomonas aeruginosa colonization in cystic fibrosis--prognostic significance

To evaluate the prognostic significance of the age at onset of chronic Pseudomonas aeruginosa colonization (OPCP) with respect to pulmonary disease progression in patients with cystic fibrosis (CF), a retrospective long-term analysis using annual chest radiographs was performed on 54 CF patients. Thirty-seven patients (68%) were chronically colonized before the age of 12 years (group 1), 17 patients (32%) thereafter (group 2). These two groups did not significantly differ in terms of mean duration of follow up (16.2 +/- 5.9 years), sex, CF genotypes, colonization with other respiratory pathogens, supportive medical treatment and death rate during the study period. Chest radiographs were evaluated according to the Chrispin-Norman score, increasing scores representing increasing severity of respiratory disease. In both groups, progression of score means was not accelerated of score means was not accelerated up to 6 years after OCPC (Scores at OCPC set 0; mean score +/- SEM 6 years prior to OCPC -5.6 +/- 2.0; 10 years after OCPC +3.6 +/- 0.7 points). Patients chronically colonized prior to age 12 years (group 1) scored significantly higher between age 2 and 11 years (maximum difference at age 8 years [mean +/- SEM]: 9.4 +/- 0.7 vs. 4.3 +/- 1.3 points; P = 0.002) as compared to group 2. After age 11 years, mean scores were similar in both groups, since in group 2 scores increased rapidly after age 8 years. We conclude that OCPC did not cause an immediate acceleration of CF lung disease judged by serial chest radiographs. Rapid progression in group 2 (OCPC after age 12 years) was independent of OCPC since it occurred earlier. These data indicate that OCPC may be a marker rather than the cause of respiratory disease progression.

[Acute asthma attack in children]

Asthma is one of the most common problems confronting the emergency department physician. It is estimated that 10 to 15% of the population have had manifestations of asthma. In pediatric patients it is the most common chronic disease, and is the leading cause of school absence. Asthma can be associated with a significant morbidity in terms of exercise intolerance and disruption of the family unit. In the present article, reference is given to three entities: bronchiolitis, wheezy bronchitis and bronchial asthma. The etiopathogenetic factors and mechanisms involved are reviewed in the light to give a rationale for what should be undertaken to treat and, thereafter, avoid asthmatic attacks in infants and children. Each occurrence of an asthmatic attack should provoke reflections concerning the actual state of diagnosis and the actual state of treatment. The final goals of an adequate long-term management of asthmatic children, which is unavoidable for most, are symptom freedom and optimized lung function. Good management will clearly help to avoid serious asthmatic attacks and to impede the development of an ongoing immunoallergic process of airway inflammation.

[Assessment of intrapulmonary ventilation disorders in children with bronchial asthma using the nitrogen elimination technique]

Stratification of functional abnormalities evaluated by whole-body plethysmography in asthmatic children can be characterized into three functional groups: pulmonary hyperinflation (H: TGV > mean + 2SD), bronchial obstruction (O: Raw > mean + 2SD) and a mixed type, group M, including both abnormalities. The multibreath nitrogen washout (MBNW) offers the possibility to measure FRC and calculate the amount of trapped gases (TG = TGV-FRCMBNW). Furthermore ventilation inequalities can be estimated by mathematical analysis of the washout curve from which indexes such as the lung clearance index (LCI), the mean dilution number (MDN) and the moment ratio (m2:m0 = M-ratio) can be obtained. In 69 asthmatic children (age 5-17 y; 38 boys, 31 girls) body plethysmography and MBNW were performed in the symptom free interval. The questions were, at what extend TG are present within the different functional groups, and which parameters best describe ventilation inequalities. The group attribution was H: 23, M: 16, O: 30. The highest amount of TG was found in H (36.4 +/- 22.2% TGV), then in M (26.6 +/- 23.1% TGV) and in O (19.4 +/- 16.0% TGV). In 33/50 cases presenting with normal TGV, TG mainly was at cost of a low FRC (13 in H, 8 im M, 12 in O). In 19 cases FRC was higher than TGV (3 in H, 1 in M 15 in O). TG was closely related with LCI, MDN and M-ratio. Most pronounced ventilation inequalities were found in group M showing a correlation only with FRC, but not with TGV.(ABSTRACT TRUNCATED AT 250 WORDS)

Protease-antiprotease imbalance in the lungs of children with cystic fibrosis

Cystic fibrosis (CF) is characterized in the lung by chronic purulent bronchitis culminating in pulmonary insufficiency. There is evidence to suggest that neutrophil elastase (NE) released by neutrophils on the respiratory epithelial surface plays a major role in the pathogenesis of this lung disease. This study sought to determine the age of onset of the chronic neutrophil-dominated inflammation in CF and the consequences to the NE-anti-NE screen on the respiratory epithelial surface of the CF lung. NE and anti-NE defensive molecules were evaluated in respiratory epithelial lining fluid (ELF) in 27 children with stable CF (1 to 18 yr of age). Despite normal antigenic concentrations of alpha 1-antitrypsin (alpha 1AT) and secretory leukoprotease inhibitor (SLPI), 25 of 27 children with CF had neutrophil-dominated inflammation (> 500 neutrophils/microliters ELF). Active NE was found in ELF in 20 of 27 children, including two of four aged 1 yr. Western blot analysis showed the majority of alpha 1AT and SLPI molecules to be complexed and/or degraded. These observations demonstrate that a chronic imbalance of the NE-anti-NE protective screen develops early on the respiratory epithelial surface in persons with CF and is likely well established by 1 yr of age, with resultant potential for lung damage.

Expression of the v-crk oncogene product in PC12 cells results in rapid differentiation by both nerve growth factor- and epidermal growth factor-dependent pathways

The transforming gene of the avian sarcoma virus CT10 encodes a fusion protein (p47gag-crk or v-Crk) containing viral Gag sequences fused to cellular sequences consisting primarily of Src homology regions 2 and 3 (SH2 and SH3 sequences). Here we report a novel function of v-Crk in the mammalian pheochromocytoma cell line, PC12, whereby stable expression of v-Crk induces accelerated differentiation, as assessed by induction of neurites following nerve growth factor (NGF) or basic fibroblast growth factor (bFGF) treatment compared with the effect in native PC12 cells. Surprisingly, however, these cells also develop extensive neurite processes after epidermal growth factor (EGF) stimulation, an event which is not observed in native PC12 cells. Following EGF or NGF stimulation of the v-CrkPC12 cells, the v-Crk protein itself became tyrosine phosphorylated within 1 min. Moreover, in A431 cells or TrkA-PC12 cells, which overexpress EGF receptors and TrkA, respectively, a GST-CrkSH2 fusion protein was indeed capable of binding these receptors in a phosphotyrosine-dependent manner, suggesting that v-Crk can directly couple to receptor tyrosine kinase pathways in PC12 cells. In transformed fibroblasts, v-Crk binds to specific tyrosine-phosphorylated proteins of p130 and paxillin. Both of these proteins are also complexed to v-Crk in PC12 cells, as evidenced by their coprecipitation with v-Crk in detergent lysates, suggesting that common effector pathways may occur in both cell types. However, whereas PC12 cellular differentiation can occur solely by overexpression of the v-Src or oncogenic Ras proteins, that induced by v-Crk requires a growth factor stimulatory signal, possibility in a two-step process.

A pressurized injection/suction system for ventilation in the presence of complete airway obstruction

OBJECTIVE

To describe the design and ventilatory characteristics of a new mode of ventilation (pressurized injection/suction ventilation).

DESIGN

Descriptive and analytical laboratory study.

SETTING

Laboratory study.

SUBJECTS

Simulated lung model and dogs.

INTERVENTIONS

We tested the ability to maintain ventilation through a 2.5-mm internal diameter ventilating stylet in the setting of simulated complete airway occlusion. A microprocessor-controlled ventilator mode was used wherein injection of oxygen under high pressure (flow rate 95 L/min) alternates with suction of expired gas (flow rate 18 L/min) through the ventilating stylet.

MEASUREMENTS AND MAIN RESULTS

In a lung model, we achieved a maximum minute ventilation of 12.9 L/min. In two dogs, we maintained stable oxygenation (mean PaO2 603 +/- 47 torr [80.4 +/- 6.3 kPa]) and ventilation (mean PaCO2 19 +/- 3 torr [2.5 +/- 0.4 kPa]) for 15 mins at maximum minute ventilation settings. No clinically important deleterious effects on the tracheal mucosa were observed. The ventilator system's safety-abort feature prevented overinflation or excessive deflation of the dogs' lungs in every test of simulated malfunction of the pressure-monitoring mechanism.

CONCLUSIONS

Pressurized injection/suction ventilation can maintain adequate gas exchange in an animal model with near-complete airway obstruction. Further work is needed to develop the safety and clinical applications of pressurized injection/suction ventilation in the management of patients with near-complete airway occlusion.

Interfering factors to sensitivity and specificity of bronchial reactivity in children

Bronchial reactivity to carbachol, estimated by the PD65, the provocation dose of inhaled carbachol inducing a 65% increase of baseline respiratory resistance, was measured in 355 asthmatic children (age 8.7 +/- 2.6 years) and 149 healthy children (age 11.8 +/- 2.3 years). The frequency distribution of PD65 showed apart from 2 minima at 480 micrograms and 960 micrograms 2 significant peaks at 240 micrograms (p = 0.003) and 1200 micrograms (p = 0.01) to carbachol, reflecting a hyperreactive class (PD65 < 480 micrograms), an intermediate class (481 micrograms < PD65 < 960 micrograms) and a normo-reactive class (PD65 > 961 micrograms). The intermediate class is characterised by a considerable overlap between "health" and "disease". However, taking into account the degree of air pollution in which healthy children are living (best related factor to specificity) and the type of initial lung function disorder in asthmatic children, (the MEF50 to be the best related factor for specificity), weighed specificity and sensitivity improved from 64 to 88%. Evaluating bronchial responsiveness in children, such interfering factors should be strongly considered.

Specific approach on dose-response curves to inhaled carbachol assessed by the interruption technique in children

To determine significant thresholds obtained by bronchial challenge tests in children for assessment of bronchial reactivity, changes of respiratory resistance (Rint) induced by inhaled carbachol were evaluated in 20 asthmatic children (10 boys and 10 girls, mean age 9.1 +/- 2.8 y, range 5 to 15 y) and 20 healthy control children (10 boys and 10 girls, mean age 12.1 +/- 2.6 y, range 8 to 16 y). Baseline lung function was assessed by whole body plethysmography. The carbachol challenge test was performed by the interruption technique. The objectives were to search for the most predictable provocation dose (PD) according to statistical and practical considerations. The statistical argument is given by the condition that the target PD must definitively be out of the measurement error of baseline values. From the practical point of view, the object is to provoke the subjects the least amount possible. As thresholds of bronchial reactivity, the provocation doses inducing a 50%, 65%, 75%, or 100% increase in baseline Rint (PD50, PD65, PD75, PD100) were computed by a 4th power polynomial function analysis including data points of the entire dose-response curve. In comparison, a new threshold, the "variance based" provocation dose (PDvb), was defined as threshold to be definitively above the range of the baseline Rint variation before initiating challenge [PDvb > mean + 2 SD range of Rint(0)]. Although the PD50, PD65, PD75, and PD100 can be adequately computed by the 4th power function from the whole dose-response curve, comparison between the different provocation thresholds revealed that PDvb gives the best values to differentiate between healthy and asthmatic children (p < 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between bone mineral density and dietary intakes in the elderly

Dietary protein and/or calorie insufficiencies represent an important problem in elderly patients. The biological and clinical implications, and particularly the influence on bone mass of undernutrition in the elderly, have not been completely defined, although several studies have demonstrated a high prevalence of dietary insufficiencies in patients with a recent fracture of the proximal femur. In the present study the relationship between dietary intakes, physical performance and bone mineral density (BMD) was examined in hospitalized elderly patients. The study comprised 74 patients (48 women, mean age 82 years; and 26 men, mean age 80 years) who were hospitalized for various medical indications. They were divided into two groups according to their dietary protein intakes, evaluated during the first 28 days in hospital while on a regular diet. The first group consisted of 26 patients (14 women and 12 men) whose protein intake was equal to or greater than 1 g per kilogram of ideal body weight. The second group consisted of 48 patients (34 women and 14 men) who consumed less than 1 g of protein per kilogram of ideal body weight. The two groups differed also in their energy, carbohydrate, lipid and calcium intakes. Patients in the group with the higher protein intake displayed higher BMD at the level of the femoral neck as measured by dual-photon absorptiometry. The men in this group also had higher lumbar spine BMD. After 4 weeks in hospital the women with a higher protein intake had significantly enhanced bicipital and quadricipital muscle strength and better performance as indicated by the increased capacity to climb stairs.(ABSTRACT TRUNCATED AT 250 WORDS)

Practical interest in the detection of functional abnormalities in infants and children with lung disease

There are new techniques which have been developed in order to assess objective functional data concerning the severity and type of abnormalities in infants and children with lung disease. In the present review some applications of the various techniques are given in connection with deductions, which can be based on such functional findings. Insight into the mechanisms leading to lung disease and the institution of appropriate therapeutic guidelines largely depend on whether the degree of pulmonary hyperinflation or restriction, of bronchial obstruction, of bronchial hyperreactivity, of ventilation inequalities and the function of gas exchange can be objectively evaluated. Recent advances in the non-invasive assessment of lung function in infants and children promises progress in this task.

Induction of basic fibroblast growth factor mRNA and protein synthesis in smooth muscle cells by cholesteryl ester enrichment and 25-hydroxycholesterol

Basic fibroblast growth factor (bFGF) is a potent smooth muscle cell mitogen. Smooth muscle cell and macrophage-derived foam cells, resulting from cholesteryl ester accretion, are hallmark characteristics of atherosclerosis. We wanted to determine if bFGF synthesis is altered during cholesteryl ester accumulation in smooth muscle cells. Cholesteryl ester enrichment causes a 3-fold increase in bFGF in cellular lysates and a 3-fold increase in steady state mRNA levels for bFGF, as compared with control cells. Conditioned media from cholesteryl ester-enriched smooth muscle cells contains 6 times more mitogenic activity than conditioned media from control cells; this activity is neutralized by an antibody directed against bFGF but not by an antibody directed against platelet-derived growth factor. These results suggest that cholesteryl ester enrichment also enhances bFGF release. Since oxysterols have been implicated in the pathogenesis of atherosclerosis, we determined if oxysterols could affect bFGF production and release. 25-Hydroxycholesterol also increases the release of bFGF-like mitogens from smooth muscle cells, as well as increasing mRNA transcript levels for bFGF. Cholesteryl ester enrichment and 25-hydroxycholesterol did not promote bFGF release secondary to cell injury. In conclusion, these data define a basic mechanism for smooth muscle cell hyperplasia during atherogenesis involving the generation of bFGF by smooth muscle cell-derived foam cells.

A new method for assessing flow-volume measurements by means of a simple isoflow electronic pocket device (IfloPen)

The IfloPen is a new device for measuring isoflows featuring specific information about the effort-independent part of the flow-volume curve. Whereas the recording of the latter normally requires expensive equipment, the IfloPen is a handy, portable and simple device. In addition, the isoflow technique requires minimal cooperation. Significant correlations have been found between the isoflow-points measured with the IfloPen and PF, MEF50, MEF25 and FEV1 (p < 0.001). The IfloPen showed better correlations with spirometric lung function data than with the Peak-flow-Meter. Even experimentally induced bronchial obstruction during a bronchial challenge with carbachol can be measured functionally by the IfloPen, showing similar changes as obtained by the FEV1 and the MEF50 (p < 0.001). From a practical point of view, the IfloPen features a new device to measure more accurately bronchial obstruction (no overestimation, physiological breathing maneuver, good practicability). It can therefore be used in medical practice and is a suitable device for home monitoring.

Comparison of different inhalation schedules to control childhood asthma

In a double-blind, placebo-controlled study control of asthma was assessed by diary symptom cards, peak-flow measurements and lung function within 3 treatment groups over a 6 months period. 36 children (25 boys, 11 girls 5.5 to 13.2 years of age) with exogen allergic, perennial asthma inhaled either beclomethasone dipropionate (BDP) with salbutamol (S) or disodium cromoglycate (DNCG) with S or a placebo preparation with S from metered dose inhalers (MDI) through a large-spaced auxiliary device (Volumatic). At entry, after 2 and 4 months lung function tests were performed evaluating changes in the degree of pulmonary hyperinflation, bronchial obstruction, and bronchial hyperreactivity (BHR). Daily PF measurements showing wide variations (up to 10-12%) were insensitive to indicate any significant changes. In contrast evaluation of symptom diaries presented dramatic improvement during the first 3 months of the study. In addition, the DNCG group showed significant improvement of BHR (p = 0.02). Moreover, the majority of patients on regular therapy with salbutamol and placebo showed an increase of airway resistance. It is concluded that even in mild childhood asthma, for optimal control a combination of a beta 2-stimulant as bronchodilator and DNCG or BDP as protector should be applied.