Randomized double blind trial of Ambroxol for the treatment of respiratory distress syndrome

High-dose Oral Ambroxol for Early Treatment of Pulmonary Acute Respiratory Distress Syndrome: an Exploratory, Randomized, Controlled Pilot Trial

OBJECTIVE

To evaluate efficacy of high-dose oral ambroxol in acute respiratory distress syndrome (ARDS) with respect to ventilator-free days (VFD).

DESIGN

Prospective, randomized, placebo-controlled, blinded pilot trial.

PATIENTS

Sixty-six mechanically ventilated patients (1 month to 12 years) with ARDS who were hand-ventilated for <24 hr before pediatric intensive care unit admission.

INTERVENTIONS

Patients randomized to oral ambroxol (40 mg/kg/day, in four divided doses) (n = 32) or placebo (n = 34) until 10 days, extubation or death whichever is earlier.

MEASUREMENTS AND MAIN RESULTS

Majority (91%) had pneumonia and bronchiolitis. Two study groups were similar in baseline characteristics. Mean partial pressure of arterial oxygen/fraction of inspired oxygen and oxygenation index were >175 and <10, respectively, with no difference in the two study groups. VFD were similar in the two study groups. Overall mortality was 26%. No adverse events were noted with ambroxol.

CONCLUSIONS

Among ventilated pulmonary ARDS patients with oxygenation index of <10, mortality was 26%. Ambroxol did not improve VFD. Study with higher and more frequently administered doses of ambroxol in larger sample is suggested after having generated relevant pharmacokinetic data among critically ill children.

A simple cost-effective modification improves the quality of immunocytochemical staining in cervical scrape samples characterized by presence of excess mucus

Immunocytochemistry (ICC) is a very important tool in a diverse range of biomedical research as well as in diagnostic cytopathology. Smears prepared from cervical scrapes contain a large amount of overlying mucus that interferes with the standard immunocytochemical staining protocol. A modified ICC protocol is described, which involves pretreatment of these smears with 1 mg/ml solution of Ambroxol hydrochloride in methanol for 1 hour. Source of Ambroxol hydrochloride was a 30 mg Mucolite^™ tablet, at a cost of 1.70 rupees (∼3·5 US cents) per tablet. This mucolytic solution effectively clears the mucus, facilitating the accessibility of the antibody to the antigenic determinants. This pretreatment resulted in the increased percentage of positively stained cells as well as staining intensity, leading to improved overall ICC staining and score. This is a novel modification that can be cost-effectively applied in ICC staining protocols for cytology samples characterized by the presence of excess mucus.

Ambroxol in the 21st century: pharmacological and clinical update

BACKGROUND

Belonging to the group of expectorants, ambroxol is an active substance with a long history that influences parameters considered to be the basis for the physiological production and the transport of the bronchial mucus. Therefore, ambroxol's indication is 'secretolytic therapy in acute and chronic bronchopulmonary diseases associated with abnormal mucus secretion and impaired mucus transport'.

OBJECTIVE

The aim of this review is to evaluate the pharmacological and clinical data on the mucokinetic compound ambroxol.

METHODS

The existing database that covers >40 years of pharmacological research and clinical development was analysed. Only studies with adequate study design were evaluated.

CONCLUSION

Ambroxol is shown to exert several activities: i) secretolytic activity (i.e., promotes mucus clearance, facilitates expectoration, and eases productive cough); ii) anti-inflammatory and antioxidant activity; and iii) a local anaesthetic effect through sodium channel blocking at the level of the cell membrane. The reduction on chronic obstructive pulmonary disease exacerbations is consistent and clinically relevant. The anaesthetic effect is a new pharmacological action that could be beneficial in the management of acute respiratory tract infections. The efficacy and safety of ambroxol is well established.

Bronchopulmonary dysplasia in preterm infants: pathophysiology and management strategies

Bronchopulmonary dysplasia (BPD) has classically been described as including inflammation, architectural disruption, fibrosis, and disordered/delayed development of the infant lung. As infants born at progressively earlier gestations have begun to survive the neonatal period, a 'new' BPD, consisting primarily of disordered/delayed development, has emerged. BPD causes not only significant complications in the newborn period, but is associated with continuing mortality, cardiopulmonary dysfunction, re-hospitalization, growth failure, and poor neurodevelopmental outcome after hospital discharge. Four major risk factors for BPD include premature birth, respiratory failure, oxygen supplementation, and mechanical ventilation, although it is unclear whether any of these factors is absolutely necessary for development of the condition. Genetic susceptibility, infection, and patent ductus arteriosus have also been implicated in the pathogenesis of the disease. The strategies with the strongest evidence for effectiveness in preventing or lessening the severity of BPD include prevention of prematurity and closure of a clinically significant patent ductus arteriosus. Some evidence of effectiveness also exists for single-course therapy with antenatal glucocorticoids in women at risk for delivering premature infants, surfactant replacement therapy in intubated infants with respiratory distress syndrome, retinol (vitamin A) therapy, and modes of respiratory support designed to minimize 'volutrauma' and oxygen toxicity. The most effective treatments for ameliorating symptoms or preventing exacerbation in established BPD include oxygen therapy, inhaled glucocorticoid therapy, and vaccination against respiratory pathogens.Many other strategies for the prevention or treatment of BPD have been proposed, but have weaker or conflicting evidence of effectiveness. In addition, many therapies have significant side effects, including the possibility of worsening the disease despite symptom improvement. For instance, supraphysiologic systemic doses of glucocorticoids lessen the incidence of BPD in infants at risk for the disease, and promote weaning of oxygen and mechanical ventilation in infants with established BPD. However, the side effects of systemic glucocorticoid therapy, most notably the recently recognized adverse effects on neurodevelopment, preclude their routine use for the prevention or treatment of BPD. Future research in BPD will most probably focus on continued incremental improvements in outcome, which are likely to be achieved through the combined effects of many therapeutic modalities.

Current perspectives on the prevention and management of chronic lung disease in preterm infants

Chronic lung disease (CLD) or bronchopulmonary dysplasia is a recognized sequel of preterm birth. With improving survival of infants at lower gestational ages, the incidence is on the rise. Pathological features of CLD include alveolar maldevelopment, with or without areas of pulmonary fibrosis. Assisted ventilation, infection/inflammation, oxygen administration, and fluid overload are the major risk factors in the evolution of CLD.Interventions, including the treatment of maternal infection, administration of prenatal glucocorticoids, and postnatal surfactant replacement therapy, improve the survival of preterm infants; however, their effect on CLD is difficult to determine. Strategies that have been effective in reducing CLD are the administration of retinol (vitamin A), high frequency oscillatory ventilation, and administration of glucocorticoids. Previous concerns regarding neurological problems associated with high frequency ventilation have not been substantiated in recent studies. Current recommendations do not advise the routine use of glucocorticoids due to concerns regarding long-term neurodevelopment. Therapies that were found to be ineffective in reducing the incidence of CLD include prenatal thyrotropin, cromolyn sodium (sodium cromoglycate), alpha-1 antitrypsin, superoxide dismutase, tocopherol (vitamin E), ascorbic acid (vitamin C), allopurinol, ambroxol, inositol, inhaled bronchodilators, and fluid restriction. Strategies that may be effective in reducing lung injury and subsequent CLD include avoiding assisted ventilation, lung protective ventilatory maneuvers, permissive hypercapnia, prevention of infection, early aggressive nutrition, and the treatment of a patent ductus arteriosus. The use of inhaled glucocorticoids improves pulmonary dynamics but long-term effects are unknown. The management of infants with established CLD has not been studied adequately, and the role of various ventilatory strategies for infants with established CLD is not clear. Adequate oxygenation should be maintained to prevent hypoxic episodes. Diuretics are helpful during acute decompensation; however, their long-term impact has not been well studied. Provision of adequate nutrition, immunization (routine and against respiratory syncytial virus), follow-up, and monitoring are the key elements in the long-term management of infants with CLD. Future research priorities should be to identify strategies to prevent/treat inflammation and promote the healing processes in the injured lung. The long-term effects of lung-protective ventilation strategies need to be studied.

Inhibition of bleomycin-induced cell death in rat alveolar macrophages and human lung epithelial cells by ambroxol

The mitochondrial permeability transition is recognized to be involved in toxic and oxidative forms of cell injury. In the present study, we investigated the effect of ambroxol against the cytotoxicity of bleomycin (BLM) by looking at the effect on the mitochondrial membrane permeability in alveolar macrophages and lung epithelial cells. Alveolar macrophages or lung epithelial cells exposed to BLM revealed the loss of cell viability and increase in caspase-3 activity. Ambroxol (10-100 microM) reduced the 75 mU/mL BLM-induced cell death and activation of caspase-3 in macrophages or epithelial cells. It reduced the condensation and fragmentation of nuclei caused by BLM in macrophages. Ambroxol alone did not significantly cause cell death. Treatment of alveolar macrophages with BLM resulted in the decrease in transmembrane potential in mitochondria, cytosolic accumulation of cytochrome c, increase in formation of reactive oxygen species (ROS) and depletion of GSH. Ambroxol (10-100 microM) inhibited the increase in mitochondrial membrane permeability, ROS formation and decrease in GSH contents due to BLM in macrophages. Ambroxol exerted a scavenging effect on hydroxyl radicals and nitric oxide and reduced the iron-mediated formation of malondialdehyde and carbonyls in liver mitochondria. It prevented cell death due to SIN-1 in lung epithelial cells. The results demonstrate that ambroxol attenuates the BLM-induced viability loss in alveolar macrophages or lung epithelial cells. This effect may be due to inhibition of mitochondrial damage and due to the scavenging action on free radicals.

Inhibition of inflammatory responses by ambroxol, a mucolytic agent, in a murine model of acute lung injury induced by lipopolysaccharide

Objective

The aim of this study is to investigate whether ambroxol inhibits inflammatory responses in a murine model of lipopolysaccharide-induced acute lung injury (ALI).

Methods

Mice (n=295) were first intratracheally instilled with lipopolysaccharide (LPS) to induce ALI and then received an intraperitoneal (ip) injection of either normal saline (NS), ambroxol (30 or 90 mg/kg per day) or dexamethasone (2.5 or 5 mg/kg per day) for 7 days. Metabolism (n=10, each), lung morphology (n=5, each) and wet-to-dry lung weight ratio (n=10, each) were studied. The levels of tumor necrosis factor (TNF-α), interleukin-6 (IL-6) and transforming growth factor (TGF-β1) and the protein concentration (n=5 or 7, each) in bronchoalveolar lavage (BAL) were measured.

Results

Mice with LPS-induced ALI that were treated with ambroxol at a dosage of 90 mg/kg per day significantly gained weight compared to the control and dexamethasone-treated groups. Ambroxol and dexamethasone significantly reduced the lung hemorrhage, edema, exudation, neutrophil infiltration and total lung injury histology score at 24 and 48 h. In addition, ambroxol and dexamethasone significantly attenuated the lung wet-to-dry weight ratio at 24 and 48 h (p<0.05). Compared to the control group, TNF-α, IL-6 and TGF-β1 levels in the BAL in both ambroxol- and dexamethasone-treated groups were significantly reduced at 24 and 48 h. The protein in BAL, an index of vascular permeability, was also significantly decreased in the ambroxol- and dexamethasone-treated groups (p<0.05).

Conclusion

Ambroxol inhibited proinflammatory cytokines, reduced lung inflammation and accelerated recovery from LPS-induced ALI.

Depressant effects of ambroxol and erdosteine on cytokine synthesis, granule enzyme release, and free radical production in rat alveolar macrophages activated by lipopolysaccharide

The present study examined the effects of ambroxol and erdosteine, bronchial expectorants, on the cytokine synthesis, granule enzyme release, and free radical production in rat alveolar macrophages activated by lipopolysaccharide. Ambroxol and erdosteine significantly decreased the production of tumour necrosis factors-alpha, interleukin-1beta, and interleukin-6 in alveolar macrophages activated by lipopolysaccharide. These drugs significantly reduced the production of superoxide anion, hydrogen peroxide, and nitric oxide and the release of acid phosphatase and lysozyme in lipopolysaccharide-activated macrophages. Ambroxol and erdosteine showed no scavenging effect on superoxide anion and hydrogen peroxide, whereas both drugs effectively decomposed nitric oxide. The results show that ambroxol and erdosteine may inhibit the responses, including cytokine synthesis and free radical production, in rat alveolar macrophages activated by lipopolysaccharide. Unlike the production of reactive oxygen species, the inhibitory effect of ambroxol and erdosteine on the production of nitric oxide in lipopolysaccharide-activated alveolar macrophages may be accomplished by a scavenging action on the species and inhibition of the respiratory burst.

Ambroxol inhibits peroxynitrite-induced damage of alpha1-antiproteinase and free radical production in activated phagocytic cells

The present study examined the effect of ambroxol on toxic action of peroxynitrite and the respiratory burst in activated phagocytic cells. Ambroxol decreased the inactivation or destruction of alpha1-antiproteinase induced by peroxynitrite (ONOO-) or hypochlorous acid (HOCl), which was similar to penicillamine and glutathione and was greater than diclofenac sodium and naproxen sodium. Ambroxol significantly decreased ONOO--mediated tyrosine nitration and iron plus EDTA-mediated degradation of 2-deoxy-D-ribose. Ambroxol significantly attenuated the production of superoxide, hydrogen peroxide, HOCl, and nitric oxide in fMLP- or IL-1-activated phagocytic cells, while the inhibitory effects of antiinflammatory and thiol compounds were only observed in HOCl production. Ambroxol and antiinflammatory drugs did not show a cytotoxic effect on macrophages. The results suggest that ambroxol protects tissue components against oxidative damage by an action different from antiinflammatory drugs. Ambroxol may interfere with oxidative damage of alpha1-antiproteinase through a scavenging action on ONOO- and HOCl and inhibition of the respiratory burst of phagocytic cells.

Depressant effect of ambroxol on stimulated functional responses and cell death in rat alveolar macrophages exposed to silica in vitro

The present study examined the effect of ambroxol on free radical production, granule enzyme release, and cell death in silica-activated rat alveolar macrophages. The action of ambroxol was assayed by measuring changes in the activities of protein kinase C (PKC) and tyrosine kinase (PTK) and in the intracellular calcium level. Ambroxol attenuated the production of superoxide, hydrogen peroxide, and nitric oxide and the release of acid phosphatase and lysozyme in macrophages activated by silica. Staurosporine, genistein, EGTA, and trifluoperazine inhibited the silica-induced free radical production and granule enzyme release. Silica induced the increase in PKC and PTK activities and the elevation of intracellular calcium level in macrophages, which was decreased by ambroxol. Silica induced a cell death and increased the caspase-3 activity in macrophages in a concentration-dependent manner. Ambroxol decreased the silica-induced cell viability loss in macrophages. The results show that ambroxol decreases the stimulated responses and cell death in rat alveolar macrophages exposed to silica, which may be accomplished by inhibition of activation processes, protein kinases, and calcium transport. The inhibitory effect of ambroxol on silica-induced cell death appears to provide the protective effect on pulmonary tissues against the toxic action of silica.

Antenatal use of ambroxol for the prevention of infant respiratory distress syndrome

OBJECTIVE

Our purpose was to evaluate the efficacy and safety of ambroxol for the prenatal prophylaxis of infant respiratory distress syndrome (IRDS).

STUDY DESIGN

This was a prospective study with 2 groups of pregnant patients with premature labor or with premature rupture of membranes at an estimated gestation between 27 to 34 completed weeks. Ambroxol treatment group consisted of 39 subjects in whom 1,000 mg of ambroxol diluted in 500 ml of 5% glucose solution was given intravenously for 4 hours once a day for 3 days, while the control group consisted of 41 subjects in whom ambroxol was not administered. Main measures included Apgar scores, clinical signs of one or more of the following: respiratory rate of > 60/min, intercostal retraction, alar flaring, expiratory grunting, cyanosis on room air and radiological evidence of IRDS. Chi-square test was used to determine the statistical significance of the results.

RESULTS

Tolerable maternal side effects were noted. Profile of newborns delivered were similar in both groups. Incidence of IRDS was significantly less in the treatment group (p < 0.01).

CONCLUSIONS

Antenatal administration of ambroxol resulted in a significant decrease in the incidence of IRDS as well as perinatal morbidity and mortality. Due to the efficacy and safety of this drug, it might be useful for the prevention of IRDS.

A risk-benefit assessment of drugs used for neonatal chronic lung disease

Improvements in neonatal intensive care have resulted in more extremely low birthweight babies surviving who are at risk of developing chronic lung disease. The preterm lung is vulnerable as it is both structurally immature and deficient in surfactant and antioxidant defences. Mechanical ventilation and high inspired oxygen concentrations are often necessary for preterm babies to survive but they can cause pulmonary inflammation which leads to lung damage. Abnormal healing in the presence of ongoing inflammation leads to airways remodelling which can result in protracted respiratory problems in these babies. A commonly used definition for chronic lung disease is the requirement for supplemental oxygen beyond 36 weeks' postconception. Many drugs that are commonly used for chronic lung disease have not been subjected to proper randomised controlled trials but are widely used on the basis of small studies showing short term benefits. They can be broadly divided into 2 groups. First, there are preventative drugs that are administered early to reduce oxygen toxicity and pulmonary inflammation. Secondly, there are those administered in established chronic lung disease, designed to reduce respiratory morbidity. Pulmonary inflammation in the neonate is reduced by systemic corticosteroids. Corticosteroid therapy within the first 2 weeks of life enables earlier extubation of preterm babies with subsequent reduced chronic lung disease and improved neonatal survival when given between 7 and 14 days. However, there is an increased risk of gastrointestinal haemorrhage, metabolic derangement, ventricular hypertrophy and potential effects on long term growth and brain development. Diuretics and inhaled bronchodilators improve pulmonary compliance and reduce oxygen requirements in established chronic lung disease but probably have little effect in reducing the incidence. In babies with established chronic lung disease, home oxygen therapy enables earlier discharge and prophylaxis against respiratory syncytial virus can reduce morbidity from bronchiolitis. All of the above therapies have adverse effects that need to be considered before initiating treatment. Recently, new drugs have become available which may be beneficial. These include inhaled nitric oxide for reduction of ventilation-perfusion mismatching, recombinant human superoxide dismutase for protection against oxidative stress and alpha-1 proteinase inhibitor which may reduce airways remodelling. At present these therapies are undergoing clinical trials. Exogenous surfactant is beneficial in respiratory distress syndrome and may reduce the risk of chronic lung disease but there have been no randomised controlled trials of its use in established chronic lung disease. Drugs which have been tried unsuccessfully include erythromycin, ambroxol and mast cell stabilisers.

Effect of early ambroxol treatment on lung functions in mechanically ventilated preterm newborns who subsequently developed a bronchopulmonary dysplasia (BPD)

In a randomized trial in 102 preterm newborns with respiratory distress syndrome (RDS) it has been shown that early Ambroxol treatment (30 mg kg(-1) over the first 5 days) significantly reduces the incidence of RDS-associated complications [bronchopulmonary dysplasia (BPD), intraventricular haemorrhage, post-natal acquired pneumonia]. The aim of the present analysis was to investigate the effect of Ambroxol treatment on lung function in newborns who developed BPD. Respiratory function testing (RFT) was performed immediately after extubation and at day 28. Tidal volume (VT) and respiratory frequency (f) were measured during tidal breathing using the deadspace free flow-through technique. The lung mechanic parameter VT/maxPes was determined by measuring the maximal oesophageal pressure changes, maxPes, with a catheter tip pressure transducer. In the placebo group 36/50 infants were extubated within the first 28 days of life and 13/36 (36%) developed BPD. In the Ambroxol group 44/52 were extubated and 9/44 (20%) developed BPD. After extubation, RFT showed (i) no statistically significant difference in the ventilatory parameters of either treatment group, (ii) improved (P<0.05) lung mechanics (VT/maxPes) in Ambroxol group compared to controls (94+/-27 ml kPa(-1) vs. 8.1+/-2.6 ml kPa(-1)) and (iii) no statistically significant difference in lung function between infants with and without BPD. At day 28 we found (i) no effect of early Ambroxol treatment on lung functions, (ii) significantly (P < 0.05) higher f (58.5+/-11.7 min(-1) vs. 49.7+/-10.1 min(-1)) and significantly (P<0.01) lower V(T) (9.6+/-1.9 ml vs. 12.3+/-2.7 ml) and V(T)/maxPes (8.9+/-2.6 ml kPa(-1)] vs. 12.0+/-2.9 ml kPa(-1)) in infants with BPD compared to infants without and (iii) these differences are not influenced by early Ambroxol treatment. If the process of BPD development is induced, early Ambroxol treatment has no influence on impaired lung function at day 28.

Depressant effects of ambroxol on lipopolysaccharide- or fMLP-stimulated free radical production and granule enzyme release by alveolar macrophages

In order to explore the depressant action of ambroxol, a bronchial expectorant, on the activated alveolar macrophage responses, its effect on lipopolysaccharide (LPS)- or N-formyl-methionyl-leucyl-phenylalanine (fMLP)- stimulated free radical production and granule enzyme release by rat lung alveolar macrophages was investigated. Ambroxol attenuated the 100 ng/ml LPS- or 1 microM fMLP-stimulated superoxide, H(2)O(2)and nitric oxide production and releases of acid phosphatase and lysozyme by alveolar macrophages. Ambroxol attenuated phorbol myristate acetate-stimulated superoxide and nitric oxide production that was inhibited by 100 nM staurosporine. N,N-dimethylsphingosine (DMS, 4.5 and 9 microM) alone stimulated superoxide production by macrophages, while 45 microM of the compound did not show a stimulatory effect. However, DMS decreased nitric oxide production in a dose-dependent manner. Ambroxol did not alter the DMS effect on free radical production that was affected by 10 microM genistein. A preincubation of macrophages with ambroxol (10 and 100 microM), staurosporine and genistein attenuated the elevation of [Ca(2+)](i)caused by LPS. The results suggest that ambroxol exerts a depressant effect on LPS- or fMLP-stimulated free radical production and granule enzyme release by rat alveolar macrophages, which may be attributed to its inhibitory action on the activation process, protein kinase C, but its action on protein tyrosine kinase is not suggested.

The inhibitory effect of ambroxol on hypochlorous acid-induced tissue damage and respiratory burst of phagocytic cells

Ambroxol (100 microM and 1 mM) and the thiols (all 1 mM), glutathione, tiopronin and cysteine, significantly attenuated the myeloperoxidase, H(2)O(2) and Cl(-) system-caused destruction of alpha(1)-antiproteinase and the HOCl-induced destruction of collagen, whereas they did not affect the elastase-induced destruction of collagen. Glutathione, tiopronin and cysteine almost completely decomposed both HOCl and H(2)O(2), while ambroxol up to 1 mM did not show a scavenging action on H(2)O(2). Ambroxol (1 to 100 microM) and 1 mM thiol compounds markedly inhibited the HOCl-induced alteration of elastase activity. Thiol compounds significantly attenuated the HOCl production caused by degraded immunoglobulin G-activated neutrophils. Ambroxol depressed superoxide and H(2)O(2) production induced by degraded immunoglobulin G-activated neutrophils and by lipopolysaccharide-activated alveolar macrophages in a dose-dependent manner. The results show that ambroxol may interfere with oxidative tissue damage and decrease proteolytic tissue destruction by attenuation of oxidative stress-induced inactivation of alpha(1)-antiproteinase through both decomposition of HOCl and inhibition of the respiratory burst in phagocytic cells.

Changes in pulmonary function in preterm infants recovering from RDS following early treatment with ambroxol: results of a randomized trial

Several studies have demonstrated that ambroxol stimulates surfactant synthesis and has antioxidative and antiinflammatory effects. We investigated the effect of ambroxol on lung function in newborns with respiratory distress syndrome (RDS) weighing <1,500 g. In all, 102 newborns were enrolled (52 received ambroxol and 50 placebo). After extubation, lung function tests were performed weekly using a face mask for ventilatory measurements and a catheter tip pressure transducer (diameter 1.7 mm) for esophageal pressure measurements (Pes) The flow-through technique was used to eliminate apparatus dead space and to allow long-term measurements during quiet sleep. Percentile curves of pulmonary function parameters from healthy newborns were used for comparison. During the first 28 days, 42 newborns were extubated in the ambroxol group and 36 in the placebo group. The ventilatory parameters of both treatment groups were in the normal range and there were no significant differences between the two groups at any time. After extubation, the ratio of tidal volume to maximal esophageal pressure changes (V(T)/P(es,max)) was below the 10th percentile in the ambroxol and placebo-treated groups. In the ambroxol group the 10th percentile was reached on day 10, whereas in the placebo group the 10th percentile was reached significantly later (P < 0.05) on day 23. Modeling of power expenditures was used to identify the optimal breathing pattern so that small differences in ventilatory parameters between the two groups could be analyzed. We conclude that early ambroxol treatment has only a modest effect on lung function in newborns with established RDS. The sensitivity of tidal breathing parameters is not sufficient to detect these small changes in lung mechanics, but small improvements could be demonstrated in lung mechanics 10 days after extubation in the ambroxol-treated group.

The inhibitory effect of ambroxol on respiratory burst, degranulation and cytosolic Ca2+ change in degraded immunoglobulin G-activated neutrophils

Superoxide and H2O2 production by neutrophils stimulated by 0.5 mg/ml degraded immunoglobulin G (IgG) and 1 microM N-formyl-methionyl-leucyl-phenylalanine (fMLP) was inhibited by ambroxol in a dose-dependent fashion, and at the concentration of 100 microM, 43.3% to 64.3% of inhibitions were detected. The inhibitory effect of ambroxol on H2O2 production by neutrophils was greater than that on superoxide production. The production of nitrite by lipopolysaccharide-activated murine peritoneal macrophages was significantly attenuated by ambroxol in a dose-dependent fashion and NG-monomethyl-L-arginine (NMMA). Ambroxol decreased the release of myeloperoxidase and lysozyme evoked by 0.5 mg/ml degraded immunoglobulin G and 1 microM fMLP in a dose-dependent fashion, and at the concentration of 100 microM, 37.1% to 64.2% of inhibitions were observed. The stimulatory effect of phorbol 12-myristate 13-acetate (PMA) (0.1 microg/ml) on superoxide production and myeloperoxidase, which is inhibited by 100 nM staurosporine, was not affected by 100 microM ambroxol. Degraded immunoglobulin G (0.5 mg/ml) caused an immediate elevation of [Ca2+]i in fura-2 load neutrophils in 1.23 mM Ca2+-containing medium. Preincubation of neutrophils with 10 microM to 100 microM ambroxol, 5 mM EGTA and 100 microM verapamil depressed the elevation of [Ca2+]i elicited by 0.5 mg/ml degraded immunoglobulin G. In conclusion, the inhibitory action of ambroxol on stimulated neutrophil responses, including respiratory burst and lysosomal enzyme release, appears to be attributed to its depressant action on the activation process, including the change in intracellular Ca2+ level. in which the role of protein kinase C is uncertain.

Comparative investigations of algorithms for the detection of breaths in newborns with disturbed respiratory signals

The correct detection of the beginning of inspiration and expiration in the respiratory signals is an essential prerequisite for accurate lung function testing in newborns. Five algorithms for breath detection using pneumotachographically measured flow and volume signals were investigated with regard to the error rate. To compare and to evaluate the reliability of these algorithms 12 minimally and 12 severely disturbed flow and volume signals from spontaneously breathing newborns were used. With the exception of an algorithm based on Walsh-transformed signals, all algorithms work reliably (error rate <1.1%) if disturbances are minimal. In severely disturbed signals there is a great difference between the algorithms. The most robust algorithm tested (trigger of the flow signal with an additional plausibility check of the recognized breath) resulted in an error rate of <3.4%. Not all algorithms tested are suitable for real-time applications because they differ considerably in delay time for breath detection.