The use of nasal dilator strips as a placebo for trials evaluating continuous positive airway pressure

OBJECTIVES: The aim of the current study was to compare the objective and subjective effects of continuous positive airway pressure to the use of nasal dilator strips in patients with acromegaly and moderate to severe obstructive sleep apnea. METHODS: We studied 12 patients with acromegaly and moderate to severe obstructive sleep apnea (male/females = 8/4, age = 52 +/- 8 ys, body mass index = 33.5 +/- 4.6 Kg/m(2), apnea-hypopnea index = 38 +/- 14 events/h) who had been included in a randomized, crossover study to receive three months of treatment with continuous positive airway pressure and nasal dilator strips. All patients were evaluated at study entry and at the end of each treatment by polysomnography, and Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index and treatment satisfaction questionnaires. ClinicalTrials.gov: NCT01265121 RESULTS: The apnea-hypopnea index values decreased significantly with continuous positive airway pressure treatment but did not change with the use of nasal dilator strips. All of the subjective symptoms improved with both treatments, but these improvements were significantly greater with continuous positive airway pressure than with the nasal dilator strips. CONCLUSION: The use of nasal dilator strips had a much smaller effect on the severity of obstructive sleep apnea in patients with acromegaly and moderate to severe obstructive sleep apnea in comparison to the use of continuous positive airway pressure. Moreover, the improvement in several subjective parameters without any significant objective improvement in obstructive sleep apnea resulting from the use of nasal dilator strips is compatible with a placebo effect.

Biphasic positive airway pressure minimizes biological impact on lung tissue in mild acute lung injury independent of etiology

Abstract Introduction Biphasic positive airway pressure (BIVENT) is a partial support mode that employs pressure-controlled, time-cycled ventilation set at two levels of continuous positive airway pressure with unrestricted spontaneous breathing. BIVENT can modulate inspiratory effort by modifying the frequency of controlled breaths. Nevertheless, the optimal amount of inspiratory effort to improve respiratory function while minimizing ventilator-associated lung injury during partial ventilatory assistance has not been determined. Furthermore, it is unclear whether the effects of partial ventilatory support depend on acute lung injury (ALI) etiology. This study aimed to investigate the impact of spontaneous and time-cycled control breaths during BIVENT on the lung and diaphragm in experimental pulmonary (p) and extrapulmonary (exp) ALI. Methods This was a prospective, randomized, controlled experimental study of 60 adult male Wistar rats. Mild ALI was induced by Escherichia coli lipopolysaccharide either intratracheally (ALIp) or intraperitoneally (ALIexp). After 24 hours, animals were anesthetized and further randomized as follows: (1) pressure-controlled ventilation (PCV) with tidal volume (Vt) = 6 ml/kg, respiratory rate = 100 breaths/min, PEEP = 5 cmH2O, and inspiratory-to-expiratory ratio (I:E) = 1:2; or (2) BIVENT with three spontaneous and time-cycled control breath modes (100, 75, and 50 breaths/min). BIVENT was set with two levels of CPAP (Phigh = 10 cmH2O and Plow = 5 cmH2O). Inspiratory time was kept constant (Thigh = 0.3 s). Results BIVENT was associated with reduced markers of inflammation, apoptosis, fibrogenesis, and epithelial and endothelial cell damage in lung tissue in both ALI models when compared to PCV. The inspiratory effort during spontaneous breaths increased during BIVENT-50 in both ALI models. In ALIp, alveolar collapse was higher in BIVENT-100 than PCV, but decreased during BIVENT-50, and diaphragmatic injury was lower during BIVENT-50 compared to PCV and BIVENT-100. In ALIexp, alveolar collapse during BIVENT-100 and BIVENT-75 was comparable to PCV, while decreasing with BIVENT-50, and diaphragmatic injury increased during BIVENT-50. Conclusions In mild ALI, BIVENT had a lower biological impact on lung tissue compared to PCV. In contrast, the response of atelectasis and diaphragmatic injury to BIVENT differed according to the rate of spontaneous/controlled breaths and ALI etiology.

CPAP Has No Effect on Clearance, Sputum Properties, or Expectorated Volume in Cystic Fibrosis

BACKGROUND: Positive expiratory pressure (PEP) is used for airway clearance in cystic fibrosis (CF) patients. Hypertonic saline (HTS) aerosol increases sputum expectoration volume and may improve respiratory secretion properties. CPAP may also be used to maintain airway patency and mobilize secretions. To evaluate if CPAP would increase the beneficial clearance effect of HTS in subjects with CF, we investigated the effects of CPAP alone and CPAP followed by HTS on sputum physical properties and expectoration volume in CF subjects. METHODS: In this crossover study, 15 CF subjects (mean age 19 y old) were randomized to interventions, 48 hours apart: directed coughs (control), CPAP at 10 cm H2O, HTS 7%, and both CPAP and HTS (CPAP+HTS). Sputum collection was performed at baseline and after interventions. Expectorated volume was determined and in vitro sputum properties were analyzed for contact angle and cough clearability. RESULTS: There were no significant differences between any treatment in arterial blood pressure, heart rate, or pulse oximetry, between the 2 time points. HTS and CPAP+HTS improved cough clearability by 50% (P = .001) and expectorated volume secretion by 530% (P = .001). However, there were no differences between control and CPAP on sputum contact angle, cough clearability, or volume of expectorated secretion. CONCLUSIONS: CPAP alone had no effect on mucus clearance, sputum properties, or expectorated volume, and did not potentiate the effect of HTS alone in CF subjects.

Mönckeberg's sclerosis – is the artery the only target of calcification?

Abstract Background Since its first description, Mönckeberg's sclerosis has only been related to arterial media calcification, being listed among the primary diseases of the vessels. Case presentation We report here a clinically and histologically confirmed case of Mönckeberg's sclerosis in which the patient presented with massive areas of soft tissue calcifications in the pharynx and larynx. Polysomnographic parameters showed severe obstructive apnea refractory to nasal continuous positive airway pressure. Clinical and laboratory findings excluded concomitant endocrine or rheumatological diseases. Conclusion Our data provide a new insight about Mönckeberg's sclerosis, i.e., the fact that the etiopathogenic process involved in the phenomenon of calcification may not be restricted only to the arteries, but may occur in the entire organism. Further studies of the etiopathogenesis of this disease are needed.

Noninvasive positive-pressure ventilation in clinical practice at a large university-affiliated Brazilian hospital

OBJECTIVES: To describe noninvasive positive-pressure ventilation use in intensive care unit clinical practice, factors associated with NPPV failure and the associated prognosis. METHODS: A prospective cohort study. RESULTS: Medical disorders (59%) and elective surgery (21%) were the main causes for admission to the intensive care unit. The main indications for the initiation of noninvasive positive-pressure ventilation were the following: post-extubation, acute respiratory failure and use as an adjunctive technique to chest physiotherapy. The noninvasive positive-pressure ventilation failure group was older and had a higher Simplified Acute Physiology Score II score. The noninvasive positive-pressure ventilation failure rate was 35%. The main reasons for intubation were acute respiratory failure (55%) and a decreased level of consciousness (20%). The noninvasive positive-pressure ventilation failure group presented a shorter period of noninvasive positive-pressure ventilation use than the successful group [three (2-5) versus four (3-7) days]; they had lower levels of pH, HCO3 and base excess, and the FiO(2) level was higher. These patients also presented lower PaO2:FiO2 ratios; on the last day of support, the inspiratory positive airway pressure and expiratory positive airway pressure were higher. The failure group also had a longer average duration of stay in the intensive care unit [17 (10-26) days vs. 8 (5-14) days], as well as a higher mortality rate (9 vs. 51%). There was an association between failure and mortality, which had an odds ratio (95% CI) of 10.6 (5.93 - 19.07). The multiple logistic regression analysis using noninvasive positive pressure ventilation failure as a dependent variable found that treatment tended to fail in patients with a Simplified Acute Physiology Score II >= 34, an inspiratory positive airway pressure level >= 15 cmH2O and pH<7.40. CONCLUSION: The indications for noninvasive positive-pressure ventilation were quite varied. The failure group had a longer intensive care unit stay and higher mortality. Simplified Acute Physiology Score II >= 34, pH<7.40 and higher inspiratory positive airway pressure levels were associated with failure.

Intermittent hypoxia inhibits clearance of triglyceride-rich lipoproteins and inactivates adipose lipoprotein lipase in a mouse model of sleep apnoea

Delayed lipoprotein clearance is associated with atherosclerosis. This study examined whether chronic intermittent hypoxia (CIH), a hallmark of obstructive sleep apnoea (OSA), can lead to hyperlipidaemia by inhibiting clearance of triglyceride rich lipoproteins (TRLP). Male C57BL/6J mice on high-cholesterol diet were exposed to 4 weeks of CIH or chronic intermittent air (control). FIO2 was decreased to 6.5 once per minute during the 12 h light phase in the CIH group. After the exposure, we measured fasting lipid profile. TRLP clearance was assessed by oral gavage of retinyl palmitate followed by serum retinyl esters (REs) measurements at 0, 1, 2, 4, 10, and 24 h. Activity of lipoprotein lipase (LpL), a key enzyme of lipoprotein clearance, and levels of angiopoietin-like protein 4 (Angptl4), a potent inhibitor of the LpL activity, were determined in the epididymal fat pads, skeletal muscles, and heart. Chronic intermittent hypoxia induced significant increases in levels of total cholesterol and triglycerides, which occurred in TRLP and LDL fractions (P 0.05 for each comparison). Compared with control mice, animals exposed to CIH showed increases in REs throughout first 10 h after oral gavage of retinyl palmitate (P 0.05), indicating that CIH inhibited TRLP clearance. CIH induced a 5-fold decrease in LpL activity (P 0.01) and an 80 increase in Angptl4 mRNA and protein levels in the epididymal fat, but not in the skeletal muscle or heart. CIH decreases TRLP clearance and inhibits LpL activity in adipose tissue, which may contribute to atherogenesis observed in OSA.

Practices of use of nasal intermittent positive pressure ventilation (NIPPV) in neonatology in northeastern Brazil

Objective: To investigate the use of nasal intermittent positive pressure ventilation (NIPPV) in level three neonatal intensive care units (NICU) in northeastern Brazil. Methods: This observational cross-sectional survey was conducted from March 2009 to January 2010 in all level three NICUs in northeastern Brazil that are registered in the Brazilian Registry of Health Establishments (Cadastro Nacional de Estabelecimentos de Saude, CNES) of the Ministry of Health. Questionnaires about the use of NIPPV were sent to the NICU directors in each institution. Statistical analysis was conducted using the software Epi-Info 6.04 and double data entry. A chi-square test was used to compare variables, and the level of statistical significance was set at p <= 0.05. Results: This study identified 93 level three NICUs in northeastern Brazil registered in CNES, and 87% answered the study questionnaire. Most classified themselves as private institutions (30.7%); 98.7% used NIPPV; 92.8 % adapted mechanical ventilators for NIPPV and used short binasal prongs as the interface (94.2%). Only 17.3% of the units had a protocol for the use of NIPPV. Mean positive inspiratory pressure and positive end-expiratory pressure were 20.0 cmH(2)O (standard deviation [SD]: 4.47) and 5.0 cmH(2)O (SD: 0.84). Conclusion: NICUs in northeastern Brazil use nasal intermittent positive pressure ventilation, but indications and ventilation settings are not the same in the different institutions.

A Randomized Trial of Noninvasive Positive End Expiratory Pressure in Patients With Acquired Immune Deficiency Syndrome and Hypoxemic Respiratory Failure

BACKGROUND: Acquired immunodeficiency syndrome (AIDS) is a pandemic disease commonly associated with respiratory infections, hypoxemia, and death. Noninvasive PEEP has been shown to improve hypoxemia. In this study, we evaluated the physiologic effects of different levels of noninvasive PEEP in hypoxemic AIDS patients. METHODS: Thirty AIDS patients with acute hypoxemic respiratory failure received a randomized sequence of noninvasive PEEP (5, 10, or 15 cm H2O) for 20 min. PEEP was provided through a facial mask with pressure-support ventilation (PSV) of 5 cm H2O and an F-IO2, of 1. Patients were allowed to breathe spontaneously for a 20-min washout period in between each PEEP trial. Arterial blood gases and clinical variables were recorded after each PEEP treatment. RESULTS: The results indicate that oxygenation improves linearly with increasing levels of PEEP. However, oxygenation levels were similar regardless of the first PEEP level administered (5, 10, or 15 cm H2O), and only the subgroup that received an initial treatment of the lowest level of PEEP (ie, 5 cm H2O) showed further improvements in oxygenation when higher PEEP levels were subsequently applied. The P-aCO2, also increased in response to PEEP elevation, especially with the highest level of PEEP (ie, 15 cm H2O). PSV of 5 cm H2O use was associated with significant and consistent improvements in the subjective sensations of dyspnea and respiratory rate reported by patients treated with any level of PEEP (from 0 to 15 cm H2O). CONCLUSIONS: AIDS patients with hypoxemic respiratory failure improve oxygenation in response to a progressive sequential elevation of PEEP (up to 15 cm H2O). However, corresponding elevations in P-aCO2, limit the recommended level of PEEP to 10 cm H2O. At a level of 5 cm H2O, PSV promotes an improvement in the subjective sensation of dyspnea regardless of the PEEP level employed.

Effects of different tidal volumes in pulmonary and extrapulmonary lung injury with or without intraabdominal hypertension

We hypothesized that: (1) intraabdominal hypertension increases pulmonary inflammatory and fibrogenic responses in acute lung injury (ALI); (2) in the presence of intraabdominal hypertension, higher tidal volume reduces lung damage in extrapulmonary ALI, but not in pulmonary ALI. Wistar rats were randomly allocated to receive Escherichia coli lipopolysaccharide intratracheally (pulmonary ALI) or intraperitoneally (extrapulmonary ALI). After 24 h, animals were randomized into subgroups without or with intraabdominal hypertension (15 mmHg) and ventilated with positive end expiratory pressure = 5 cmH(2)O and tidal volume of 6 or 10 ml/kg during 1 h. Lung and chest wall mechanics, arterial blood gases, lung and distal organ histology, and interleukin (IL)-1 beta, IL-6, caspase-3 and type III procollagen (PCIII) mRNA expressions in lung tissue were analyzed. With intraabdominal hypertension, (1) chest-wall static elastance increased, and PCIII, IL-1 beta, IL-6, and caspase-3 expressions were more pronounced than in animals with normal intraabdominal pressure in both ALI groups; (2) in extrapulmonary ALI, higher tidal volume was associated with decreased atelectasis, and lower IL-6 and caspase-3 expressions; (3) in pulmonary ALI, higher tidal volume led to higher IL-6 expression; and (4) in pulmonary ALI, liver, kidney, and villi cell apoptosis was increased, but not affected by tidal volume. Intraabdominal hypertension increased inflammation and fibrogenesis in the lung independent of ALI etiology. In extrapulmonary ALI associated with intraabdominal hypertension, higher tidal volume improved lung morphometry with lower inflammation in lung tissue. Conversely, in pulmonary ALI associated with intraabdominal hypertension, higher tidal volume increased IL-6 expression.

Variability of neurally-adjusted ventilatory assist (nava) compared to pressure support ventilation (psv) during the weaning phase of mechanical ventilation.

Rationale: NAVA is an assisted ventilatory mode that uses the electrical activity of the diaphragm (Edi) to trigger and cycle the ventilator, and to offer inspiratory assistance in proportion to patient effort. Since Edi varies from breath to breath, airway pressure and tidal volume also vary according to the patient's breathing pattern. Our objective was to compare the variability of NAVA with PSV in mechanically ventilated patients during the weaning phase. Methods: We analyzed the data collected for a clinical trial that compares PSV and NAVA during spontaneous breathing trials using PSV, with PS of 5 cmH2O, and NAVA, with Nava level titrated to generate a peak airway pressure equivalent to PSV of 5 cmH2O (NCT01137271). We captured flow, airway pressure and Edi at 100Hz from the ventilator using a dedicated software (Servo Tracker v2, Maquet, Sweden), and processed the cycles using a MatLab (Mathworks, USA) code. The code automatically detects the tidal volume (Vt), respiratory rate (RR), Edi and Airway pressure (Paw) on a breath-by-breath basis for each ventilatory mode. We also calculated the coefficient of variation (standard deviation, SD, divided by the mean). Results: We analyzed data from eleven patients. The mean Vt was similar on both modes (370 ±70 for Nava and 347± 77 for PSV), the RR was 26±6 for Nava and 26±7 or PSV. Paw was higher for Nava than for PSV (14±1 vs 11±0.4, p=0.0033), and Edi was similar for both modes (12±8 for Nava and 11±6 for PSV). The variability of the respiratory pattern, assessed with the coefficient of variation, was larger for Nava than for PSV for the Vt ( 23%±1% vs 15%±1%, p=0.03) and Paw (17%±1% vs 1% ±0.1%, p=0.0033), but not for RR (21% ±1% vs 16% ±8%, p=0.050) or Edi (33%±14% vs 39% ±16%,p=0.07). Conclusion: The variability of the breathing pattern is high during spontaneous breathing trials independent of the ventilatory mode. This variability results in variability of airway pressure and tidal volume, which are higher on Nava than on PSV. Our results suggest that Nava better reflects the normal variability of the breathing pattern during assisted mechanical ventilation.

Development and Evaluation of a Pseudoreference Pt//Ag/AgCl Electrode for Electrochemical Systems

The use of standard reference electrodes, such as Ag/AgCl or saturated calomel electrodes, in potentiometric and amperometric studies involving miniaturized electrochemical systems, or those operating under positive hydraulic pressure, is often impractical. Placement of the reference electrode in the direct vicinity of the working electrode is often prohibited by the dimensions or layout of the electrochemical cell, while the alternative strategy of locating the reference electrode in a separate compartment often leads to electrolyte leakage and contamination of the system. In the present study, we have investigated the functionality of a pseudoreference electrode comprising a platinum wire, one end of which was maintained in intimate contact with the internal solution of an Ag/AgCl reference electrode while the other was connected, via a BNC connector, to a platinum probe located within the electrochemical cell. Linear and cyclic voltammetric studies, involving both aqueous and nonaqueous electrolytes, were carried out using the pseudoreference electrode and an electrochemical cup-type cell with three electrodes or an electrochemical flow reactor. In all cases, the functionality of the Pt//Ag/AgCl system was similar to that of a conventional Ag/AgCl reference electrode. Variations in the electrolyte did not alter the potential or voltammetric profile recorded when using the pseudoreference system, although peak currents were generally improved and potential values shifted by approximately +350 mV in comparison with the Ag/AgCl electrode, therefore, the system pseudoreference can be applied in any electrochemical system due to the constant potential difference. It is concluded that the pseudoreference electrode can be used with advantage to obtain potentiometric and amperometric measurements in both simple and complex electrochemical systems.

Effects of Positive End-expiratory Pressure Titration and Recruitment Maneuver on Lung Inflammation and Hyperinflation in Experimental Acid Aspiration-induced Lung Injury

Background: In acute lung injury positive end-expiratory pressure (PEEP) and recruitment maneuver are proposed to optimize arterial oxygenation. The aim of the study was to evaluate the impact of such a strategy on lung histological inflammation and hyperinflation in pigs with acid aspiration-induced lung injury. Methods: Forty-seven pigs were randomly allocated in seven groups: (1) controls spontaneously breathing; (2) without lung injury, PEEP 5 cm H2O; (3) without lung injury, PEEP titration; (4) without lung injury, PEEP titration + recruitment maneuver; (5) with lung injury, PEEP 5 cm H2O; (6) with lung injury, PEEP titration; and (7) with lung injury, PEEP titration + recruitment maneuver. Acute lung injury was induced by intratracheal instillation of hydrochloric acid. PEEP titration was performed by incremental and decremental PEEP from 5 to 20 cm H2O for optimizing arterial oxygenation. Three recruitment maneuvers (pressure of 40 cm H2O maintained for 20 s) were applied to the assigned groups at each PEEP level. Proportion of lung inflammation, hemorrhage, edema, and alveolar wall disruption were recorded on each histological field. Mean alveolar area was measured in the aerated lung regions. Results: Acid aspiration increased mean alveolar area and produced alveolar wall disruption, lung edema, alveolar hemorrhage, and lung inflammation. PEEP titration significantly improved arterial oxygenation but simultaneously increased lung inflammation in juxta-diaphragmatic lung regions. Recruitment maneuver during PEEP titration did not induce additional increase in lung inflammation and alveolar hyperinflation. Conclusion: In a porcine model of acid aspiration-induced lung injury, PEEP titration aimed at optimizing arterial oxygenation, substantially increased lung inflammation. Recruitment maneuvers further improved arterial oxygenation without additional effects on inflammation and hyperinflation.

Low pressure support changes the rapid shallow breathing index (RSBI) in critically ill patients on mechanical ventilation

Background: The rapid shallow breathing index (RSBI) is the most widely used index within intensive care units as a predictor of the outcome of weaning, but differences in measurement techniques have generated doubts about its predictive value. Objective: To investigate the influence of low levels of pressure support (PS) on the RSBI value of ill patients. Method: Prospective study including 30 patients on mechanical ventilation (MV) for 72 hours or more, ready for extubation. Prior to extubation, the RSBI was measured with the patient connected to the ventilator (Drager (TM) Evita XL) and receiving pressure support ventilation (PSV) and 5 cmH(2)O of positive end expiratory pressure or PEEP (RSBI_MIN) and then disconnected from the VM and connected to a Wright spirometer in which respiratory rate and exhaled tidal volume were recorded for 1 min (RSBI_ESP). Patients were divided into groups according to the outcome: successful extubation group (SG) and failed extubation group (FG). Results: Of the 30 patients, 11 (37%) failed the extubation process. In the within-group comparison (RSBI_MIN versus RSBI_ESP), the values for RSBI_MIN were lower in both groups: SG (34.79 +/- 4.67 and 60.95 +/- 24.64) and FG (38.64 +/- 12.31 and 80.09 +/- 20.71; p<0.05). In the between-group comparison, there was no difference in RSBI_MIN (34.79 +/- 14.67 and 38.64 +/- 12.31), however RSBI_ESP was higher in patients with extubation failure: SG (60.95 +/- 24.64) and FG (80.09 +/- 20.71; p<0.05). Conclusion: In critically ill patients on MV for more than 72h, low levels of PS overestimate the RSBI, and the index needs to be measured with the patient breathing spontaneously without the aid of pressure support.

First-year experience of a Brazilian tertiary medical center in supporting severely ill patients using extracorporeal membrane oxygenation

OBJECTIVES: The aim of this manuscript is to describe the first year of our experience using extracorporeal membrane oxygenation support. METHODS: Ten patients with severe refractory hypoxemia, two with associated severe cardiovascular failure, were supported using venous-venous extracorporeal membrane oxygenation (eight patients) or veno-arterial extracorporeal membrane oxygenation (two patients). RESULTS: The median age of the patients was 31 yr (range 14-71 yr). Their median simplified acute physiological score three (SAPS3) was 94 (range 84-118), and they had a median expected mortality of 95% (range 87-99%). Community-acquired pneumonia was the most common diagnosis (50%), followed by P. jiroveci pneumonia in two patients with AIDS (20%). Six patients were transferred from other ICUs during extracorporeal membrane oxygenation support, three of whom were transferred between ICUs within the hospital (30%), two by ambulance (20%) and one by helicopter (10%). Only one patient (10%) was anticoagulated with heparin throughout extracorporeal membrane oxygenation support. Eighty percent of patients required continuous venous-venous hemofiltration. Three patients (30%) developed persistent hypoxemia, which was corrected using higher positive end-expiratory pressure, higher inspired oxygen fractions, recruitment maneuvers, and nitric oxide. The median time on extracorporeal membrane oxygenation support was five (range 3-32) days. The median length of the hospital stay was 31 (range 3-97) days. Four patients (40%) survived to 60 days, and they were free from renal replacement therapy and oxygen support. CONCLUSIONS: The use of extracorporeal membrane oxygenation support in severely ill patients is possible in the presence of a structured team. Efforts must be made to recognize the necessity of extracorporeal respiratory support at an early stage and to prompt activation of the extracorporeal membrane oxygenation team.

Extracellular matrix in airway smooth muscle is associated with dynamics of airway function in asthma

Background: Altered deposition of extracellular matrix (ECM) in the airway smooth muscle (ASM) layer as observed in asthma may influence ASM mechanical properties. We hypothesized that ECM in ASM is associated with airway function in asthma. First, we investigated the difference in ECM expression in ASM between asthma and controls. Second, we examined whether ECM expression is associated with bronchoconstriction and bronchodilation in vivo. Methods: Our cross-sectional study comprised 19 atopic mild asthma patients, 15 atopic and 12 nonatopic healthy subjects. Spirometry, methacholine responsiveness, deep-breath-induced bronchodilation (Delta R-rs) and bronchoscopy with endobronchial biopsies were performed. Positive staining of elastin, collagen I, III and IV, decorin, versican, fibronectin, laminin and tenascin in ASM was quantified as fractional area and mean density. Data were analysed using Pearson's or Spearman's correlation coefficient. Results: Extracellular matrix expression in ASM was not different between asthma and controls. In asthmatics, fractional area and mean density of collagen I and III were correlated with methacholine dose-response slope and DRrs, respectively (r = 0.71, P < 0.01; r = 0.60, P = 0.02). Furthermore, ASM collagen III and laminin in asthma were correlated with FEV1 reversibility (r = -0.65, P = 0.01; r = -0.54, P = 0.04). Conclusion: In asthma, ECM in ASM is related to the dynamics of airway function in the absence of differences in ECM expression between asthma and controls. This indicates that the ASM layer in its full composition is a major structural component in determining variable airways obstruction in asthma.