The effect of inhaled nitric oxide and oxygen on the hydroxylation of salicylate in rat lungs

Inhaled nitric oxide (iNO) is used as a selective pulmonary vasodilator, and often under conditions when a high fraction of inspired oxygen is indicated. However, little is known about the potential toxicity of iNO therapy with or without concomitant oxygen therapy. NO can combine with superoxide (O2-) to form peroxynitrite (ONOO-), which can in turn decompose to form hydroxyl radical (OH.). Both OH. and ONOO- are involved in various forms of lung injury. To begin evaluation of the effect of iNO under either normoxic or hyperoxic conditions on OH. and/or ONOO- formation, rats were exposed for 58 h to either 21% O2, 21% O2 + 10 parts per million (ppm) NO, 21% O2 + 100 ppm NO, 50% O2, 90% O2, 90% O2 + 10 ppm NO, or 90% O2 + 100 ppm NO. We used a salicylate hydroxylation assay to detect the effects of these exposures on lung OH. and/or ONOO- formation measured as the appearance of 2,3-dihydroxybenzoic acid (2,3-DHBA). Exposure to 90% O2 and 90% O2 + 100 ppm NO resulted in significantly (p < 0.05) greater lung wet weight (1.99 +/- 0.14 g and 3.14 +/- 0.30 g, respectively) compared with 21% O2 (1.23 +/- 0.01 g). Exposure to 21% O2 + 100 ppm NO led to 2.5 times the control (21% O2 alone) 2,3 DHBA formation (p < 0.05) and exposure to 90% O2 led to 2.4 times the control 2,3-DHBA formation (p < 0.05). However, with exposure to both 90% O2 and 100 ppm NO, the 2,3-DHBA formation was no greater than the control condition (21% O2). Thus, these results indicate that, individually, both the hyperoxia and the 100 ppm NO led to greater salicylate hydroxylation, but that the combination of hyperoxia and 100 ppm NO led to less salicylate hydroxylation than either did individually. The production of OH. and/or ONOO- in the lung during iNO therapy may depend on the ratio of NO to O2.     

Responses of pulmonary platelet-derived growth factor peptides and receptors to hyperoxia and nitric oxide in piglet lungs

The peptides platelet-derived growth factor-A (PDGF-A) and especially -B have important roles in lung development. The effect of hyperoxic exposure with and without inhaled nitric oxide (iNO) on lung expression of PDGF and its receptors is unknown. We hypothesized that hyperoxia exposure would suppress mRNA expression and protein production of these ligands and their receptors. The addition of iNO to hyperoxia may further aggravate the effects of hyperoxia. Thirteen-day-old piglets were randomized to breathe 1) room air (RA); 2) 0.96 fraction of inspired oxygen (O2), or 3) 0.96 fraction of inspired oxygen plus 50 ppm of NO (O2+NO), for 5 d. Lungs were preserved for mRNA, Western immunoblot, and immunohistochemical analyses for PDGF-A and -B and their receptors PDGFR-alpha and -beta. PDGF-B mRNA expression was greater than that of PDGF-A or PDGFR-alpha and -beta in RA piglet lungs (p<0.05). Hyperoxia with or without iNO reduced lung PDGF-B mRNA and protein expression relative to the RA group lungs (p<0.01). PDGF-B immunostain intensity was significantly increased in the alveolar macrophages, which were present in greater numbers in the hyperoxia-exposed piglet lungs, with or without NO (p<0.01). PDGFR-beta immunostaining was significantly increased in airway epithelial cells in O2- and O2+NO-exposed piglets. PDGF-A and PDGFR-alpha immunostain intensity and distribution pattern were unchanged relative to the RA group. Sublethal hyperoxia decreases PDGF-B mRNA and protein expression but not PDGF-A or their receptors in piglet lungs. iNO neither aggravates nor ameliorates this effect.     

Endostatin and vascular endothelial cell growth factor (VEGF) in piglet lungs: effect of inhaled nitric oxide and hyperoxia

Pulmonary hyperoxic injury manifests as widespread alveolar-epithelial and microvascular endothelial cell necrosis, resolution of which requires angiogenesis. We investigated the hypothesis that inhaled nitric oxide (iNO) and hyperoxia each decreases lung vascular endothelial growth factor (VEGF) expression but increases endostatin and that concurrent administration of both gases will show a greater effect. Piglets were randomized to breathe for 5 d room air (RA); RA + NO (RA + 50 ppm NO), O(2) (hyperoxia, F(I)O(2) >0.96), O(2) + NO, or O(2) + NO + REC (O(2) + NO plus recovery in 50% O(2) for 72 h. After the piglets were killed, we measured lung capillary leak, VEGF mRNA, VEGF, and endostatin protein in homogenates, plasma, and lavage. VEGF mRNA decreased significantly with O(2) and O(2) + NO compared with breathing RA (p < or = 0.05). VEGF protein declined in the experimental groups with a significant reduction in the recovery group compared with the RA group (p < or = 0.05). Similar but more dramatic, endostatin declined in all groups relative to the RA group (p < 0.001). Lavage fluid VEGF protein and lung capillary leak rose significantly with O(2) and O(2) + NO compared with RA, but endostatin was unchanged. At 72 h of recovery from hyperoxia, VEGF mRNA and lavage fluid VEGF but not lung VEGF protein had normalized. Hyperoxia and iNO suppresses lung endostatin expression, but iNO unlike hyperoxia alone does not alter lung VEGF production. Hyperoxia paradoxically raises lavageable VEGF levels. This latter effect and that on VEGF mRNA level but not protein is abrogated by recovery in reduced F(I)O(2) for 72 h.     

Inhaled nitric oxide attenuates hyperoxic lung injury in lambs

Cytochrome P450 (CYP) inhibition with cimetidine reduces hyperoxic lung injury in young lambs. Nitric oxide (NO), also a CYP inhibitor, has been shown to either aggravate or protect against oxidant stress depending on experimental context. The objective of this study was to determine whether NO, like cimetidine, would protect young lambs against hyperoxic lung injury, and whether its effect was associated with CYP inhibition. Three groups of lambs were studied: 1) room air exposure, 2) >95% O2, and 3) >95% O2 plus inhaled NO. After 72 h, hyperoxia alone resulted in a significant increase in arterial P(CO2) and number of polymorphonuclear leukocytes in bronchoalveolar lavage (BAL), and a significant decrease in arterial/alveolar O2 tension (a/A). The addition of inhaled NO significantly decreased the hypercarbia and BAL polymorphonuclear cellular response associated with hyperoxia but had no beneficial effect on a/A ratio. There were no significant differences in F2-isoprostanes or isofurans (markers of lipid peroxidation) measured in BAL or lung tissue among study groups. No intergroup differences were detected in BAL epoxyeicosatrienoic acid levels (index of CYP activity). The results of this study indicate that hypercarbia and inflammation accompanying hyperoxic lung injury in young lambs can be attenuated by inhaled NO. However, this study provides no direct evidence that NO is inhibiting CYP-mediated oxidant lung injury.     

高氧致慢性肺疾病新生大鼠肺组织中ERK1/2变化的研究

目的：探讨细胞外信号调节激酶（ERK）1/2在高氧致慢性肺疾病（CLD）新生大鼠肺组织中的表达及作用。方法：将48 只新生Wistar大鼠随机分为高氧组和对照组,每组 24 只。高氧组生后即置于氧箱中,维持氧浓度为 0.90,诱导CLD;对照组生后置于空气中。于生后3 d、7 d和14 d采集肺组织标本,应用免疫组化、Western blot及Real-time PCR方法检测ERK1/2蛋白及mRNA表达,同时测定肺组织纤维化评分。结果：免疫组化及Western blot结果显示7 d、14 d时高氧组肺组织p-ERK1/2蛋白的表达均明显高于同时间点对照组（P<0.01）。Western blot结果同时显示各组间ERK1/2总蛋白的表达差异无统计学意义。Real-time PCR结果表明各组间ERK1、ERK2 mRNA水平差异无统计学意义（P＞0.05）。结论：新生大鼠持续吸入高氧后,ERK1/2蛋白磷酸化活化,参与了高氧致CLD肺纤维化的形成过程。     

Hyperoxia and tidal volume: Independent and combined effects on neonatal pulmonary inflammation

BACKGROUND: Hyperoxia and tidal volume mechanical ventilation are independent factors in the genesis of lung injury, but it remains unclear the extent to which each is responsible or contributes to this process in newborns. OBJECTIVES: To study the independent and combined effects of hyperoxia and tidal volume mechanical ventilation on the induction of lung inflammation in a newborn piglet model of ventilator-induced lung injury. METHODS: Following exposure to either ambient air or F(I)O2 = 1.0 for a period of 3 days, newborn piglets were randomized to receive mechanical ventilation with either high tidal volume (20 ml/kg) or low tidal volume (6 ml/kg) for 4 h while controlling for pH. RESULTS: Monocyte chemoattractant protein-1 level in the lungs of animals randomized to hyperoxia with high tidal volume ventilation was significantly elevated, compared to all other groups (p < 0.05). Myeloperoxidase assayed in lung homogenate was found to be significantly higher in nonventilated animals exposed to hyperoxia (p < 0.01). Only in animals previously exposed to hyperoxia did the addition of high tidal volume ventilation further increase the level of myeloperoxidase present (p < 0.05). Pulmonary vascular resistance was significantly elevated after 4 h of mechanical ventilation compared to 1 h (p < 0.001). CONCLUSIONS: We conclude that in neonatal piglets undergoing hyperoxic stress, superimposition of high tidal volume ventilation exacerbates the lung inflammation as assessed by lung monocyte chemoattractant protein-1 and level of myeloperoxidase.     

高氧致慢性肺疾病新生鼠肺泡上皮细胞AQP_1和AQP_5表达及其意义

目的探讨高氧损伤状态下,肺组织内水通道蛋白1(AQP1)和AQP5 mRNA的动态变化规律及其在肺水肿中的作用。方法新生鼠320只,依据吸氧浓度(FiO2)分组:实验组1(FiO20.8)、实验组2(FiO20.6)、实验组3(FiO20.4)、空气对照组(FiO20.21)。每组分别于实验后1、3、5、7、14d行AQP1 mRNA、AQP5 mRNA RT-PCR检测,同时检测肺组织Evans蓝含量。结果高氧各组肺组织Evans蓝含量与空气组相比均显著增加,并随吸氧浓度、暴露时间的延长而增加。新生大鼠肺组织AQP1(高氧3d时)、AQP5(高氧5d时)基因表达明显低于对照组(F1=53.004,P=0.008;F2=16.617,P=0.01),总趋势上AQP1、AQP5 mRNA的表达实验组1、实验组2、实验组3依次降低。结论AQP1、AQP5 mRNA在高氧肺损伤时表达降低,并与肺水肿的严重程度密切相关。     

Inhaled nitric oxide decreases hyperoxia-induced surfactant abnormality in preterm rabbits

Inhaled nitric oxide (iNO) is a specific pulmonary vasodilator. By serving as a pro-oxidant or antioxidant, iNO may influence other pulmonary functions as well. This study was designed to test the hypothesis that iNO affects the alveolar lining after premature birth. Preterm rabbits (gestation 29 d, term 31 d) were nose-only exposed NO (14 ppm) and 98% O2, for 20 h. The others were exposed to either 98% O2 or air. In another experiment, premature rabbits were exposed to either NO in air or to air. After the exposure, bronchoalveolar lavage (BAL) was performed and the surfactant aggregates were isolated. The surfactant components and surface activity were analyzed. In total, 144 animals were studied. There were no significant differences in the number, distribution, or respiratory burst activity of cells recovered by BAL. Neither brief hyperoxia nor iNO increased plasma-derived proteins in BAL. Exposure to O2 decreased large surfactant aggregates, surface activity, and the content of surfactant protein B in BAL, whereas iNO prevented completely or partially these effects of acute hyperoxia on surfactant. Hyperoxia increased the content of malondialdehyde and decreased glutathione in epithelial lining fluid. iNO decreased malondialdehyde (p < 0.05) and tended to increase glutathione (p = 0.06) in animals breathing O2. Nitrotyrosine was not detectable in BAL, and NO2 was low in the breathing area. In room air, iNO had no significant effect on surfactant. According to the present results, a brief period of hyperoxia causes an oxidant stress and decreases the surface activity of alveolar surfactant in premature rabbits. In contrast, a low dosage of iNO decreased or prevented the O2-induced detrimental effects on alveolar surfactant and alleviated the oxidant stress.     

表皮生长因子对新生未成熟大鼠高氧性损伤肺组织纤维化的影响

目的探讨外源性表皮生长因子(epidermalgrowthfactor,EGF)对新生大鼠高氧性损伤肺组织纤维化的影响。方法取胎龄21d剖宫产出生的新生Sprague-dawley(SD)大鼠持续吸入95%的O2制作未成熟肺高氧性损伤模型,随机分为高氧 EGF组和高氧 生理盐水(NS)组,另设空气 NS对照组;所有组按给药(或NS)时间分为3个亚组,即:a亚组(1~3d)、b亚组(4~6d)、c亚组(1~6d);各亚组均于生后3、7、14d分批处死采取肺组织标本。应用Masson三色染色、纤维化评分及羟脯氨酸含量测定判断肺组织纤维化的程度。结果空气 NS组未见胶原沉积增多现象,高氧 NS组生后7d胶原沉积明显增多,14d程度加重,7、14d高氧 EGF组较高氧 NS组胶原沉积明显减少;羟脯氨酸(HYP)的含量和纤维化评分也表明7、14d时高氧 EGF组胶原纤维的含量较高氧 NS组明显减少(P<0·01);在高氧 EGF组中b亚组效果不及a亚组和c亚组。结论表皮生长因子可以减轻新生未成熟大鼠高氧性损伤肺组织纤维化程度,在肺损伤早期应用效果更好。     

Glutathione ethyl ester supplementation prevents mortality in newborn rats exposed to hyperoxia

Human premature neonates suffer from respiratory distress syndrome due to immature lungs and require assisted ventilation with high concentrations of oxygen. Hyperoxic exposure and/or antioxidant deficiency causes an increase in the lung levels of reactive oxygen species (ROS) leading to oxidative stress-induced cellular damage. In this study, we explored the protective role of the nonenzymatic antioxidant glutathione, by administering glutathione ethyl ester (GSHEE), in newborn rats exposed to hyperoxia (>95% FiO(2)). Our results show that GSHEE supplementation (5 mmol/kg/day) prevents mortality in newborn rats exposed to hyperoxia. We further show that delayed GSHEE supplementation in newborn rats, pre-exposed to hyperoxia for 4 days, also prevents death. Electron microscopic studies on the lung of GSHEE-treated hyperoxic rats showed normal histology and an absence of the marked swelling and degeneration of mitochondria and lamellar bodies, which are typically observed in the hyperoxic lungs of newborn rats. Furthermore, there were no apparent differences in weight gain or general appearance/activity among room air and hyperoxic GSHEE-supplemented animals when monitored, post-treatment, in room air for 30 days. Our results show a preventive/therapeutic role of GSHEE supplementation against mortality caused in newborn rats due to hyperoxic exposure, and may further be applicable to a variety of degenerative diseases that are caused as a result of ROS accumulation.     

新生大鼠高氧肺损伤血管内皮生长因子蛋白及其mRNA表达变化研究

目的：血管内皮生长因子（VEGF）参与肺的发育和损伤修复,VEGF具有促进肺泡和肺血管增殖以及预防新生儿支气管肺发育不良（BPD）的作用。该研究的目的是探讨新生大鼠高氧肺损伤后肺组织VEGF蛋白及VEGF mRNA表达的变化。方法：新生Sprague-Dawley大鼠48只随机分为高氧实验组和空气对照组,高氧实验组吸入95%以上高氧建立高氧肺损伤模型。分别采用免疫组化法和逆转录多聚酶链式反应（RT-PCR）检测新生大鼠3 d,7 d,14 d肺组织VEGF蛋白及VEGF mRNA表达变化。结果：空气对照组新生大鼠生后随着肺发育,肺组织中VEGF蛋白及VEGF mRNA表达逐渐增加。高氧实验组新生鼠吸入高氧3 d,肺VEGF蛋白表达出现降低,在7 d,14 d明显降低与对照组比较差异有显著性（VEGF 蛋白:12.67±3.82 vs 7.79±5.23; 15.10±8.91 vs 5.85±3.37, 均P<0.01）;高氧实验组VEGF mRNA表达在3 d,7 d,14 d均明显低于对照组（VEGF mRNA: 1.19±0.63 vs 0.78±0.22, 1.52±0.47 vs 0.53±0.18, 1.89±0.81 vs 0.48±0.12, 均P<0.01）。结论：VEGF能促进新生大鼠肺发育,VEGF蛋白及VEGF mRNA表达与新生大鼠肺发育有密切关系。高氧可抑制VEGF蛋白及VEGF mRNA在新生大鼠肺内的表达,VEGF在新生鼠肺发育和高氧肺损伤发病机制中起重要作用。     

Altered expressions of fibroblast growth factor receptors and alveolarization in neonatal mice exposed to 85% oxygen

In the present study, we tested the hypothesis that exposure of newborn mice to sublethal hyperoxia would alter lung development and expressions of fibroblast growth factor receptors (FGFRs)-3 and FGFR-4. Newborn FVB mice were exposed to 85% O2 or maintained in room air for up to 14 d. No animal mortality was observed, and body weight gains were not affected by hyperoxia. At postnatal d 7 and 14 (P7, P14), lungs of mice exposed to 85% O2 showed fewer alveolar secondary crests and larger alveoli or terminal air spaces than did mice in room air. In pups kept in room air, lung levels of FGFR-3 and FGFR-4 mRNA were greater at P3 than at P1, but similar increases were not observed in hyperoxic mice. Immunoreactivity of FGFR-3 and FGFR-4 was lower in lungs of hyperoxic mice than in controls at P14. In pups kept in room air, lung fibroblast growth factor (FGF)-7 mRNA levels were greater at P14 than at P1, but similar changes were not observed in hyperoxic mice. The temporally and spatially specific alterations in the expressions of FGFR-3, FGFR-4, and FGF-7 in the mice exposed to hyperoxia may contribute to aberrant lung development.     

Effect of initial nitric oxide concentration on outcome in infants with persistent pulmonary hypertension of the newborn

A randomized nonblinded comparison of two treatment groups was performed to determine whether treatment of infants with persistent pulmonary hypertension of the newborn using a continuous 6-ppm dose of inhaled nitric oxide (iNO) changes the likelihood of death or utilization of extracorporeal membrane oxygenation (ECMO) when compared to infants treated with 20 ppm iNO for 4 h followed by 6 ppm. Twenty-nine infants with a gestational age >/=34 weeks and a diagnosis of persistent pulmonary hypertension of the newborn were enrolled during the 3- year study period. The relative risk (20/6 vs. 6 ppm) for treatment with ECMO was 3.11 (p = 0.02), for death it was 2.80 (p = 0.32), and for either death or ECMO it was 3.42 (p = 0. 006). There was no apparent advantage of treatment with a higher dosage of iNO at the initiation of therapy in the reduction of death or utilization of ECMO. These data suggest that a continuous lower dose of iNO results in a comparable improvement in oxygenation as a short exposure of higher dose iNO at the initiation of therapy.     

细胞粘附因子-1在新生大鼠高氧肺损伤模型肺组织的表达及意义

目的探讨细胞粘附因子-1(ICAM-1)与新生大鼠高氧肺损伤的关系以及高氧肺损伤的发病机制。方法取102只胎龄22天足月新生大鼠,随机分为实验组与对照组各51只。实验组生后立即置入持续高浓度氧(>95%)环境中饲养,对照组在空气中饲养。两组新生大鼠根据随机数字法于生后第3、7、14天各抽取8只定位相应亚组。处死新生鼠取其肺组织,HE染色观察肺组织病理变化,Masson三色染色判断肺组织纤维化程度,免疫组化检测ICAM-1并对表达强度进行半定量分析。结果 (1)对照组生后3、7、14天各亚组未见肺损伤的病理性改变,Masson三色染色未见胶原沉积增多现象,ICAM-1在肺组织中阴性或弱阳性表达。(2)实验组7天HE染色可见大量炎细胞浸润,肺间隔轻度增宽,14天炎细胞浸润减少,肺泡结构破坏较明显,肺间隔明显增厚;Masson三色染色生后7天胶原沉积开始增加,14天纤维化程度更加显著,ICAM-1在各时间点均呈阳性表达,且分布广泛;半定量分析显示,实验组各时间点ICAM-1的表达明显高于对照组,生后7天表达最强(P<0.05)。结论高氧对肺组织有明显的损害作用,高氧暴露早期ICAM-1在肺组织中的表达随着暴露时间的延长而增加,ICAM-1在高氧暴露早期的急性炎症阶段起作用,继续暴露则逐渐降低,并未证实其与高氧肺损伤后期的纤维化有关系。     

Differential responses in the lungs of newborn mouse pups exposed to 85% or >95% oxygen

Premature infants often develop serious clinical complications associated with respiratory failure and hyperoxic lung injury that includes lung inflammation and alterations in lung development. The goal of these studies is to test the hypothesis that there are differences in the course of lung injury in newborn mice exposed to 85% or >95% oxygen that provide models to address the differential effects of oxidation and inflammation. Our results indicate differences between the 85% and >95% O2 exposure groups by day 14 in weight gain and lung alveolarization. Inflammation, assessed by neutrophil counts, was observed in both hyperoxia groups by day 3 but was dramatically greater in the >95% O2-exposed groups by day 14 and associated with greater developmental deficits. Cytoplasmic phospholipase A2, cyclooxygenase-2, and 5-lipoxygenase levels were elevated but no patterns of differences were observed between exposure groups. Prostaglandins D2, E2, and F2alpha were increased in the tissues from mouse pups exposed to >95% O2 at 7 d indicating a differential expression of cyclooxygenase-2 products. Our data indicate that there are differences in the models of 85% or >95% O2 exposure and these differences may provide mechanistic insights into hyperoxic lung injury in an immature system.     

粘着斑激酶在早产大鼠高氧肺损伤肺组织中的表达变化和意义

目的探讨粘着斑激酶(FAK)与高氧肺损伤发生、发展的关系。方法剖宫术取出孕21 d大鼠作为早产鼠,分别置早产鼠于85％高氧环境下3、7和14 d,各组均以空气组早产鼠为对照,留取肺组织标本,采用免疫组织化学法和Western blot技术对高氧组和空气组肺组织FAK多肽表达进行定位、定量检测,采用RT-PCR方法对FAK mRNA表达水平进行半定量分析。结果 FAK mRNA和蛋白在空气组早产大鼠肺组织均有较高水平表达,高氧暴露3、7和14 d后,FAK mRNA和蛋白表达水平均呈不同程度的下降,尤以高氧14 d最明显。结论高氧抑制FAK表达是导致正常肺泡化过程受阻以及不成熟肺组织损伤后异常修复的重要因素,其机制可能与其抑制肺泡上皮细胞增殖、分化,以及毛细血管形成有关。     

基质金属蛋白酶-8及其组织抑制因子-1在高氧致新生鼠肺纤维化中的基因表达及其意义

目的：近年来研究发现细胞外基质（ECM）的过度沉积与肺纤维化发生密切相关，而ECM合成与降解在新生儿慢性肺疾病的肺纤维化发生、发展中作用如何尚不清楚。本文着重研究基质金属蛋白酶-8（MMP-8, Ⅰ型胶原的降解酶）及其组织抑制因子-1（TIMP-1）基因在高氧致新生鼠肺损伤中的表达，并探讨其在纤维化中的作用。方法：80只足月新生大鼠依吸氧浓度（FiO2）随机分为高氧组（FiO2＝0.90）和对照组（FiO2＝0.21）,每组均为40只。采用高浓度氧诱导新生鼠肺损伤模型，应用酶联免疫吸附法（ELISA）、免疫组织化学及反转录聚合酶链反应（RT-PCR）技术，动态研究MMP-8及TIMP-1 mRNA表达，并同时观察肺组织Ⅰ型胶原蛋白的表达强度及其含量变化。结果：实验后14 d 和21 d的高氧组肺组织中，Ⅰ型胶原蛋白表达和Ⅰ型胶原水平均高于对照组， 差异有显著性意义。 而实验后14 d 和21 d，高氧组肺组织MMP-8 mRNA表达降低，TIMP-1 mRNA表达增高，与对照组比较差异有显著性意义。结论：高氧通过下调MMP-8及上调TIMP-1基因表达，导致ECM降解减少，过量ECM沉积于肺组织, 这可能是高氧致肺纤维化的机制之一。［中国当代儿科杂志，2007，9（1）：1-5］     

Use of inhaled nitric oxide in the new born period: results from the European inhaled nitric oxide registry

Aims: The aim of this study was to present data relating to the use of inhaled nitric oxide (iNO) in newborn infants included in the European Inhaled Nitric Oxide Registry. Methods: Demographic, clinical and therapeutic data from seven European centres are reported. Univariate analyses were performed to identify factors associated with acute response to iNO and survival without extra corporeal membrane oxygenation (ECMO). Results: A total of 112 newborn infants received iNO, with 40% being less than 34 weeks gestational age. The commonest indication for iNO was secondary pulmonary hypertension. Acute response to iNO was more common in infants with a higher oxygenation index (median OI 32.7 vs 22.6, p = 0.040), although acute response did not predict survival without ECMO. Infants who survived without ECMO had a lower OI prior to therapy (median OI 24 vs 43, p = 0.009), were commenced on a higher starting dose (median dose 20 ppm vs 10 ppm p = 0.013) and received a lower maintenance dose (median dose 10 vs 17 ppm, p = 0.027) than those who died or received ECMO. Conclusion: Collating and reporting data about iNO therapy in neonates across a number of European centres using a web‐based system is feasible. These data may be used to monitor the clinical use of iNO, identify adverse effects, generate research hypotheses and promote high standards in the clinical use of iNO.