Long-term treatment with oral N-acetylcysteine: affects lung function but not sputum inflammation in cystic fibrosis subjects. A phase II randomized placebo-controlled trial.

PURPOSE: To evaluate the effects of oral N-acetylcysteine (NAC), which replenishes systemic glutathione, on decreasing inflammation and improving lung function in CF airways. METHODS: A multicenter, randomized, double-blind proof of concept study in which 70 CF subjects received NAC or placebo orally thrice daily for 24 weeks. ENDPOINTS: primary, change in sputum human neutrophil elastase (HNE) activity; secondary, FEV(1) and other clinical lung function measures; and safety, the safety and tolerability of NAC and the potential of NAC to promote pulmonary hypertension in subjects with CF. RESULTS: Lung function (FEV(1) and FEF(25-75%)) remained stable or increased slightly in the NAC group but decreased in the placebo group (p=0.02 and 0.02). Log(10) HNE activity remained equal between cohorts (difference 0.21, 95% CI -0.07 to 0.48, p=0.14). CONCLUSIONS: NAC recipients maintained their lung function while placebo recipients declined (24 week FEV1 treatment effect=150 mL, p<0.02). However no effect on HNE activity and other selected biomarkers of neutrophilic inflammation were detected. Further studies on mechanism and clinical outcomes are warranted.

Hemodynamic effects of endothelin-1 on ovine fetal pulmonary circulation.

To determine the hemodynamic effects of endothelin-1 (ET-1) in the fetal pulmonary circulation, we studied pulmonary vascular responses to brief and prolonged intrapulmonary infusions of the peptide in nine chronically prepared late-gestation fetal sheep. Left pulmonary artery (LPA) blood flow was measured with an electromagnetic flow transducer, and a catheter placed in the LPA allowed ET-1 infusion directly into the left lung. Brief (10-min) infusions of ET-1 (12.5-100 ng/min) increased flow up to 212% of baseline without changing pulmonary artery pressure. With prolonged (120-min) infusion of ET-1 (50 ng/min), flow increased from 69 +/- 8 to 164 +/- 23 ml/min at 10 min (P less than 0.05) but then declined and was not different from baseline at 120 min. The gradient between mean pulmonary artery and aortic pressures did not change, suggesting no constriction of the ductus arteriosus. Systemic (vena caval) infusion of ET-1 (100 ng/min for 30 min) caused systemic and pulmonary hypertension, as mean pulmonary artery pressure increased from 43 +/- 1 to 51 +/- 2 mmHg (P less than 0.05) and remained elevated for 30 min after cessation of the ET-1 infusion. We conclude that intrapulmonary ET-1 is a potent fetal pulmonary vasodilator, but its dilator effect is transient during prolonged infusion. In contrast, systemic infusion causes sustained hypertension, suggesting differential effects of ET-1 on the pulmonary and systemic circulations. These findings demonstrate marked vasoactivity of ET-1 in the fetus, suggesting a potential role in the normal or abnormal transitional circulation.

Role of endothelium-derived relaxing factor during transition of pulmonary circulation at birth.

To examine the potential role of endothelium-derived relaxing factor (EDRF) in regulation of the perinatal pulmonary circulation, we studied the hemodynamic effects of a selective inhibitor of EDRF production, nitro-L-arginine (L-NA), on pulmonary vascular tone and dilator reactivity in the late-gestation ovine fetus and on the pulmonary vasodilation that normally occurs at birth. L-NA infusion decreased pulmonary blood flow from 78 +/- 8 to 65 +/- 6 ml/min (P less than 0.01) and increased pulmonary artery pressure from 48 +/- 2 to 54 +/- 3 mmHg (P less than 0.002, n = 8 animals). To study the selectivity of L-NA on vasodilator responses to endothelium-dependent (acetylcholine) and -independent (atrial natriuretic factor) stimuli, we measured responses to brief infusions of each dilator before and after L-NA treatment. Acetylcholine increased pulmonary blood flow during the control period but not after L-NA treatment. In contrast, L-NA had little effect on the vasodilator response to atrial natriuretic factor. To study the role of EDRF in the transition of the pulmonary circulation from fetal to neonatal conditions, we infused L-NA into the left pulmonary artery immediately before cesarean-section delivery. In comparison with control animals, the rise in pulmonary blood flow at 1 h after delivery was reduced in the L-NA-treated animals (331 +/- 28 in control vs. 185 +/- 16 ml/min in treated, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Maturational changes in endothelium-derived relaxing factor activity of ovine pulmonary arteries in vitro.

To examine mechanisms underlying fetal pulmonary vascular vasodilator responses and maturational changes in endothelial function, we studied effects of endothelium-dependent (acetylcholine, ACh: adenosine diphosphate, ADP; and A23187) and -independent (sodium nitroprusside, SNP) vasodilators on tone of small (third generation) pulmonary artery rings isolated from late-gestation fetal, newborn, and adult sheep. Changes in isometric force of phenylephrine-contracted rings were measured after the cumulative addition of vasodilators in baths aerated with 21% O2 and 5% CO2. Pulmonary artery rings from fetal lambs demonstrated minimal relaxation to ACh, ADP, and A23187, achieving only 17 +/- 3, 14 +/- 5, and 23 +/- 8% relaxation, respectively. In contrast, fetal rings relaxed completely (100%) to SNP. Rings from newborn and adult animals had significantly greater maximal relaxation in response to ACh. ADP, and A23187 than fetal rings (at least P less than 0.05 for each comparison with fetal rings), but responses to SNP were not different. Hemoglobin (10(-5) M), an inhibitor of endothelium-derived relaxing factor, caused less augmentation of phenylephrine contraction in fetal than adult pulmonary artery rings (11 +/- 4% vs. 49 +/- 8%; P less than 0.01). We conclude that in comparison with pulmonary artery rings from postnatal animals, fetal pulmonary artery rings have diminished endothelium-derived relaxation factor activity. We speculate that maturational changes in endothelial cell function contribute to ontogenetic differences in pulmonary vasoreactivity.

Diagnostic value of transbronchial, thoracoscopic, and open lung biopsy in immunocompetent children with chronic interstitial lung disease.

OBJECTIVES: To evaluate the diagnostic value of transbronchial biopsy (TBB), video-assisted thoracoscopy (VAT), and open lung biopsy (OLB) in immunocompetent children with chronic, diffuse infiltrates; to identify factors that may predict diagnosis in children requiring biopsy; to determine whether age, number of biopsies, or type of procedure are associated with diagnostic yield in children undergoing transthoracic biopsy; and to compare morbidity of VAT with that of OLB. STUDY DESIGN: As part of a prospective, descriptive study to define the clinical spectrum of pediatric interstitial lung disease, 30 immunocompetent children required TBB, VAT, and/or OLB for diagnosis of diffuse infiltrates. We reviewed and analyzed the following clinical variables: age; preoperative diagnosis; type of procedure; number of lobes undergoing biopsies; durations of surgery, chest tube insertion, and hospitalization; tissue diagnosis; and complications. RESULTS: Specific diagnoses were made in 50%, 60%, and 53% of patients undergoing TBB, VAT, and OLB, respectively. A variety of rare disorders was found, and tissue diagnosis confirmed the preoperative diagnosis in 25% of all procedures. For patients who underwent transthoracic biopsy, patient age of greater than 24 months was significantly associated with increased diagnostic yield, but the number of lobes biopsied and type of procedure were not. VAT was associated with shorter operating time, chest tube placement, and hospitalization when compared with OLB. The complications of VAT and OLB were comparable. CONCLUSION: Lung biopsy is an important tool for the diagnosis of interstitial lung disease in immunocompetent children, but the diagnosis of many children, particularly those aged 2 years or younger, remains uncertain.

Effects of birth-related stimuli on L-arginine-dependent pulmonary vasodilation in ovine fetus.

To determine the effects of birth-related stimuli on L-arginine-dependent vasodilation or nitric oxide (NO) activity in the perinatal lung, we studied the fetal pulmonary vascular effects of nitro-L-arginine (L-NA), a specific inhibitor of NO formation, during 1) mechanical ventilation without altering fetal blood gas tensions; 2) administration of high oxygen concentrations; and 3) increased flow or shear stress. In the first protocol, 13 late-gestation fetal lambs were ventilated with low fraction of inspired oxygen concentration (FIO2 less than or equal to 0.10) for 60 min after infusion of L-NA or saline into the left pulmonary artery (LPA). In control animals, LPA flow steadily increased during 60 min of ventilation. With L-NA treatment, the rise in flow and decrease in total pulmonary resistance (TPR) were reduced 67% (P less than 0.001 vs. control) and 28% (P less than 0.01 vs. control), respectively. Subsequent ventilation with high FIO2 (1.00) decreased mean pulmonary arterial pressure (PAP) in control but not in L-NA-treated animals. TPR remained fourfold greater in L-NA-treated animals than in control animals (P less than 0.001). In the second protocol, with partial compression of the ductus arteriosus, LPA flow increased 300% and TPR decreased 61% over 30 min. After L-NA treatment the rise in blood flow and decrease in TPR was markedly attenuated (P less than 0.001). We conclude that the perinatal pulmonary vasodilator response to ventilation without changing arterial oxygen tension and ventilation with increased oxygen tension are modulated by NO.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated immunoreactive endothelin-1 levels in newborn infants with persistent pulmonary hypertension.

To study the potential role of endothelin-1, a potent endothelium-derived vasoconstrictor peptide, in the pathophysiology of persistent pulmonary hypertension of the newborn (PPHN), we measured arterial concentrations of immunoreactive endothelin-1 (irET-1) in 24 neonates with PPHN. Secondary diagnoses included meconium aspiration syndrome (13 patients), sepsis (2), congenital diaphragmatic hernia (1), asphyxia (1), pulmonary hemorrhage (1), aspiration of blood (1), and respiratory distress syndrome (1). Compared with irET-1 levels in umbilical cord blood in normal infants (15.1 +/- 4.1 pg/ml; mean +/- SEM) and in newborn infants with hyaline membrane disease who were supported by mechanical ventilation (11.8 +/- 1.2 pg/ml), infants with PPHN had markedly elevated circulating irET-1 levels (27.6 +/- 3.6 pg/ml; p < 0.01 vs cord blood, hyaline membrane disease). Infants with severe PPHN requiring extracorporeal membrane oxygenation (ECMO) therapy had higher irET-1 levels than infants with milder disease (31.0 +/- 4.7 for ECMO-treated infants vs 21.2 +/- 2.0 for non-ECMO-treated infants; p < 0.05). In patients treated without ECMO, irET-1 progressively decreased during the following 3 to 5 days, paralleling clinical improvement. In contrast, irET-1 concentrations remained elevated in infants with severe PPHN during ECMO therapy. We conclude that circulating irET-1 levels are elevated in newborn infants with PPHN, are positively correlated with disease severity, and decline with resolution of disease in patients who do not require ECMO therapy. Whether endothelin-1 contributes directly to the pathophysiology of PPHN or is simply a marker of disease activity remains speculative.

Circulating immunoreactive endothelin-1 in children with pulmonary hypertension. Association with acute hypoxic pulmonary vasoreactivity.

To determine whether circulating levels of endothelin-1 (ET-1), a potent vasoconstrictor peptide, are elevated in children with pulmonary hypertension and related to the degree of hypoxic pulmonary vasoconstriction, we measured arterial and mixed venous plasma concentrations of immunoreactive ET-1 (irET-1) in 13 children during cardiac catheterization. Clinical diagnoses in seven children with pulmonary hypertension (PH) included chronic lung disease (four children), congenital heart disease after surgical repair (two children), and primary ("reactive") pulmonary hypertension (one child). Blood samples were simultaneously obtained from pulmonary artery (venous) and systemic arterial sites during baseline conditions. Plasma irET-1 was elevated in children with PH (12.3 +/- 3.4 versus 3.6 +/- 0.7 pg/ml, PH versus non-PH; p < 0.01). Arterial/venous irET-1 ratios in the PH group (1.1 +/- 0.2) were not different from those in the non-PH group. During acute hypoxia, mean Ppa increased from 27 +/- 3 to 40 +/- 5 mm Hg. Basal irET-1 correlated strongly with the degree of elevation of mean Ppa during acute hypoxia (r = 0.69; p < 0.02). We conclude that irET-1 levels are often elevated in children with PH, and they are strongly correlated with pulmonary vasoreactivity during acute hypoxia. Whether elevated irET-1 levels contribute directly to or are markers of altered pulmonary vascular tone and reactivity in children with PH remains speculative.

Pancreatic insufficiency, growth, and nutrition in infants identified by newborn screening as having cystic fibrosis.

To evaluate the impact of early pancreatic insufficiency on growth and nutritional status in cystic fibrosis, we studied 49 infants identified by a newborn screening program. Pancreatic insufficiency, determined by increased 72-hour fecal fat excretion, was present in 59% (23/39) of infants at diagnosis (7.0 +/- 0.8 weeks; mean +/- SEM). Before initiation of pancreatic enzyme replacement, growth and nutritional status of pancreatic-insufficient (n = 16) and pancreatic-sufficient (n = 13) infants were compared. Pancreatic-insufficient infants gained less weight from birth to diagnosis (13.4 +/- 3.4 vs 22.3 +/- 4.0 gm/day; p = 0.05), had decreased triceps skin-fold thicknesses (4.5 +/- 0.3 vs 6.1 +/- 0.4 mm; p less than 0.005), and had lower blood urea nitrogen (3.07 +/- 0.42 vs 4.62 +/- 0.65 mg/dl; p = 0.02) and albumin (2.99 +/- 0.14 vs 3.54 +/- 0.14 gm/dl; p less than 0.01) levels despite higher gross calorie (154 +/- 8 vs 116 +/- 13 kcal/kg per day; p less than 0.01) and protein intakes (2.81 +/- 0.21 vs 2.14 +/- 0.33 gm/kg per day; p = 0.03). Fecal nitrogen loss was correlated with fat loss (r = 0.79; p less than 0.001). Fat malabsorption was present in 79% (30/38) and 92% (33/36) of infants tested at 6 months and 12 months of age, respectively, indicating that pancreatic insufficiency persists and increases in frequency throughout infancy. We conclude that pancreatic insufficiency is prevalent in young infants with cystic fibrosis and has a significant impact on growth and nutrition.