Different Concentrations Of Nitric Oxide Research Articles

Nitric oxide reapplication during controlled atmosphere storage impacts on oxidative stress and volatiles production in 'Cripps Pink' apples

The aim of this study was to evaluate the effect of different concentrations of nitric oxide (NO) reapplied during controlled atmosphere (CA) storage on oxidative stress defense mechanisms and on profile of volatile compounds of 'Cripps Pink' apples. Fruit were treated with NO at 0, 1, 2, 5, or 10 μL L−1 every seven days during CA storage (0.8 kPa of O2, <0.5 kPa of CO2, at temperature of 1.5 ± 0.2 °C, and 94 ± 2% RH). Fruit were evaluated after 8 months of CA storage, followed by seven days of shelf life. In general, linear and quadratic models adjusted to quantitative levels of NO showed increased contents of total phenolic compounds (in the pulp and peel tissues), increased activity of catalase, reduced activity of lipoxygenase, reduced content of H2O2, reduced lipid peroxidation and ethylene production in the fruit with the increase of NO concentrations. NO treatment had no effect in the total antioxidant activity and in the activity of the enzymes superoxide dismutase and peroxidase in the fruit. The increase of NO concentrations reduced the volatile compounds butyl acetate, hexyl acetate, 2-methylbutyl acetate, ethyl butanoate, til 2-methylbutanoate, and 1-butanol in the pulp of the fruit. The results show that weekly application of NO at ∼6 μL L−1 during CA storage of 'Cripps Pink' apples improved the mechanisms to protect the fruit from oxidative stress, but it might impair the production of the main esters associated with aroma.

Effect of nitric oxide fumigation on microorganisms and quality of dried apricots during storage

The effect of nitric oxide (NO) on microorganisms and quality of dried apricots during storage was investigated. The results showed that NO fumigation at various concentrations could effectively reduce natural disease and moth pest incidence, as well as decrease the total number of microorganisms on dried apricots during storage. Compared with the control (CK), NO fumigation maintained higher levels of total soluble solids, titratable acidity, ascorbic acid, and reducing sugar in dried apricots. Additionally, the fumigated apricots displayed lower levels of total color change, degree of browning, and decline of nutrients compared with control. Furthermore, although the concentrations of nitrate and nitrite ions in dried apricots after NO fumigation were higher than those of the CK group, their levels were in line with the standard limits. Among the different concentrations of NO, 1,500 μl/L showed the best results regarding natural diseases, moth pests, and microbial inhibition, while 900 μl/L maintained the best quality of dried apricots during storage. These findings demonstrated that NO fumigation has potential to be a safe and effective treatment method to control microbial contamination and preserve the storage quality of dried apricots. Practical applications Nitric oxide (NO) fumigation can be used as a safe and effective storage method for dried fruits. This is the theoretical and technical foundation for the industrial application of NO fumigation technology, which provides new ideas and directions for the storage of dried fruits.

A Highly Stable Two-Photon Ratiometric Fluorescence Probe for Real-Time Biosensing and Imaging of Nitric Oxide in Brain Tissues and Larval Zebrafish

A Highly Stable Two-Photon Ratiometric Fluorescence Probe for Real-Time Biosensing and Imaging of Nitric Oxide in Brain Tissues and Larval Zebrafish

Preconditioning of sperm with sublethal nitrosative stress: a novel approach to improve frozen-thawed sperm function.

Can sublethal stress induced by nitric oxide on fresh human spermatozoa protect the functional properties of post-thaw human spermatozoa? Semen samples were obtained from 46 donors. Twenty semen samples were used to determine toxicity level of nitric oxide by incubation of semen with different concentrations of nitric oxide (0.01 to 400 μM). Then, 26 semen samples were cryopreserved with optimized ranges of nitric oxide: control (NO-0.00), 0.01 μM nitric oxide (NO-0.01), 0.1 μM nitric oxide (NO-0.1), 1 μM nitric oxide (NO-1), 10 μM nitric oxide (NO-10), 100 μM nitric oxide (NO-100). Frozen-thawed spermatozoa were assessed for motion characteristics, viability, morphology, apoptosis-like changes, caspase 3 activity, DNA fragmentation and intracellular reactive oxygen species levels. Fertilization potential was investigated by heterologous piezo-intracytoplasmic sperm injection (piezo-ICSI) of human spermatozoa into mouse oocytes. In fresh spermatozoa, nitric oxide did not induce a negative effect, except a significant reduction in motility and viability at 200 µM and 400 µM (P < 0.05). Cryopreservation significantly reduced sperm motility and increased reactive oxygen species, apoptosis-like changes, caspase 3 activity, and DNA damage (P < 0.05). NO-0.01 significantly increased total and progressive motility versus the other groups (P < 0.05). The lowest percentage of caspase 3 activity was in the NO-0.01 and NO-0.1 compared with the other freezing groups. In the fertilization trial, the rate of two-cell embryo formation after heterologous piezo-ICSI was higher (P < 0.05) in NO-0.01 (69%) versus controls (42%). Sublethal oxidative stress induced by nitric oxide might improve human sperm function after cryopreservation.

Catalytic oxidation of NO to NO2 for nitric acid production over a Pt/Al2O3 catalyst

The oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) is a key step both in NOx abatement technologies as well as in the Ostwald process for nitric acid production. A 1 wt.% Pt/Al2O3 catalyst was used to study oxidation of nitric oxide at two different concentrations of NO; 400 ppm NO (representative of engine exhaust treatment) and 10% NO (nitric acid plant). The catalyst was characterised using N2 adsorption and CO chemisorption. The effect of temperature and feed concentration on catalytic activity was investigated.For a feed comprising of 10% NO and 6% O2, Pt/Al2O3 exhibits significant catalytic activity above 300 °C. Addition of 15% H2O in the feed had an insignificant effect on activity of the catalyst. We report for the first time the kinetics for oxidation of NO to NO2 under nitric acid plant conditions. An apparent activation energy of 33 kJ/mol was observed. The rate equation for the overall reaction was determined to be r=kfKG(PO2)0.5, where kf is the forward rate constant. The reaction is independent of NO concentration while it has half order dependency on oxygen. The reaction mechanism which fits our experimental observation consists of dissociative adsorption of oxygen, associative adsorption of nitric oxide with desorption of nitrogen dioxide as the rate limiting step.

Stress preconditioning of rooster semen before cryopreservation improves fertility potential of thawed sperm

Avian semen cryopreservation is not as successful as that seen in mammals. This failure is mostly attributed to unique physiological characteristics of poultry semen that make it susceptible to cryo-damages. Utilization of sublethal oxidative stress for preconditioning of sperm, as an innovative approach, improves the cryo-survival of sperm in certain mammalian species. The purpose of this study was to investigate the effects of preconditioning of rooster semen with sublethal oxidative stress [very low concentrations of nitric oxide (NO)] before cryopreservation on the quality and fertility potential of thawed sperm. Semen samples were collected from 20 roosters, twice a wk, and different concentrations of NO [0 (NO-0), 0.01 (NO-0.01), 0.1 (NO-0.1), 1 (NO-1), 10 (NO-10), and 100 μM (NO-100)] were used to investigate the effects of controlled induction of sublethal stress before semen cryopreservation on the thawed sperm performance. A significantly higher (P < 0.05) percentage of total motility was observed in semen treated with NO-1 compared to NO-0, NO-0.01, NO-0.1, NO-10, and NO-100. NO-1 and NO-100 produced the highest and lowest percentages of progressive motility, which were significantly different from that of the other groups (P < 0.05). A significantly higher (P < 0.05) percentage of sperm mitochondria activity was observed in semen exposed to NO-0, NO-0.01, NO-0.1, and NO-1. Moreover, the lowest (P < 0.05) concentration of malondialdehyde (MDA) was measured in samples treated with NO-1 in comparison to the other groups. Abnormal morphology, acrosome integrity, and velocity parameters [velocity average path (VAP) and linearity (LIN)] of sperm were not significantly (P > 0.05) affected by different concentrations of NO. Sperm exposed to NO-1 produced the highest percentage of viable spermatozoa (Annexin-/PI-), which was significantly different from the other samples. Finally, rate of fertility after artificial insemination was significantly higher (P < 0.05) following treatment with NO-1 compared to NO-0 and NO-0.1. Application of 1μM NO as a sublethal oxidative stress before cryopreservation of sperm efficiently increased numerous quality indices of thawed sperm as well as its fertility potential.

A chamber study of alkyl nitrate production formed by terpene ozonolysis in the presence of NO and alkanes

Organic nitrates are relatively long-lived species and have been shown to have a potential impact on atmospheric chemistry on local, regional, and even global scales. However, the significance of these compounds in the indoor environment remains to be seen. This work describes an impinger-based sampling and analysis technique for organic nitrate species, focusing on formation via terpene ozonolysis in the presence of nitric oxide (NO). Experiments were conducted in a Teflon film environmental chamber to measure the formation of alkyl nitrates produced from α-pinene ozonolysis in the presence of NO and alkanes using gas chromatography with an electron capture detector. For the different concentrations of NO and O3 analyzed, the concentration ratio of [O3]/[NO] around 1 was found to produce the highest organic nitrate concentration, with [O3] = 100 ppb & [NO] = 105 ppb resulting in the most organic nitrate formation, roughly 5 ppb. The experiments on α-pinene ozonolysis in the presence of NO suggest that organic nitrates have the potential to form in indoor air between infiltrated ozone/NO and terpenes from household and consumer products.

Effects of different concentrations of nitric oxide on liver cancer cell line HepG2 and peripheral blood mononuclear cells in indirect co-culture system

Objective To study the effects of different concentrations of nitric oxide (NO) on liver cancer cell line HepG2 and peripheral blood mononuclear cells (PBMC). Methods Different rates of PBMC/HepG2 and drugs were arranged to regulate the concentrations of NO. Activity changes of the two kinds of cells were measured in cells cultured alone and co-cultured, which were compared with control group. Results The activity of PBMCs in co-cultured system was harmed only when the concentration of NO was more than 120 μmol/L, however, the activity of HepG2 cells in co-cultured system was suppressed when the concentration of NO was less than that of control group or was more than 241 μmol/L; moreover, the activity of co-cultured HepG2 cells was higher than that of HepG2 cells cultured alone in different concentrations of NO. In co-cultured system, with the increase of PBMC/HepG2 ratio, the concentration of NO was decreased, but the activity of HepG2 cells was increased. Conclusions The results have shown that HepG2 cells are damaged by high or low concentration of NO, and PBMC are only damaged by high concentration of NO, however, the low concentration of NO has few influences on PBMC. Moreover, the indirect contact of PBMC can promote the growth of the HepG2 cells. Key words: Liver neoplasms; Co-culture; Nitric oxide; Immunotherapy

The features of lipid peroxidation and the antioxidant system of blood under the influence of different concentrations of nitric oxide in a chronic experiment

This paper presents the results of the study of oxidative metabolism of the blood of intact animals subjected to prolonged exposure to nitric oxide at concentrations of 20, 50, and 100 ppm. The experiment was carried out with Wistar rats. NO inhalation was performed for 30 days. The state of blood oxidative metabolism was evaluated after inhalation and a 30-day-long recovery period after discontinuation of NO oxidative stress. The intensity of lipid peroxidation was studied in plasma and erythrocytes by induced biochemiluminescence and the measurement of the level of malondialdehyde. The activity of superoxide dismutase was determined in the hemolysate of erythrocytes. It was established that the optimal dose of inhaled NO is 20 ppm: a maximum increase in the total antioxidant activity after 30 days and normalization of lipid peroxidation in the blood after the completion of the recovery period were observed at this concentration. High concentrations of nitric oxide (50 and 100 ppm) initiated lipid peroxidation in erythrocytes and plasma after discontinuation of NO oxidative stress (after the completion of the recovery period) thus enhancing catalytic properties of superoxide dismutase.

Differentiated, Promoter-specific Response of [4Fe-4S] NsrR DNA Binding to Reaction with Nitric Oxide

NsrR is an iron-sulfur cluster protein that regulates the nitric oxide (NO) stress response of many bacteria. NsrR from Streptomyces coelicolor regulates its own expression and that of only two other genes, hmpA1 and hmpA2, which encode HmpA enzymes predicted to detoxify NO. NsrR binds promoter DNA with high affinity only when coordinating a [4Fe-4S] cluster. Here we show that reaction of [4Fe-4S] NsrR with NO affects DNA binding differently depending on the gene promoter. Binding to the hmpA2 promoter was abolished at ∼2 NO per cluster, although for the hmpA1 and nsrR promoters, ∼4 and ∼8 NO molecules, respectively, were required to abolish DNA binding. Spectroscopic and kinetic studies of the NO reaction revealed a rapid, multi-phase, non-concerted process involving up to 8–10 NO molecules per cluster, leading to the formation of several iron-nitrosyl species. A distinct intermediate was observed at ∼2 NO per cluster, along with two further intermediates at ∼4 and ∼6 NO. The NsrR nitrosylation reaction was not significantly affected by DNA binding. These results show that NsrR regulates different promoters in response to different concentrations of NO. Spectroscopic evidence indicates that this is achieved by different NO-FeS complexes.

Effect of nitric oxide on postharvest quality of lime fruit (citrus aurantifolia swingle)

The effect of different concentrations of nitric oxide (NO) on postharvest life of lime (Citrus aurantifolia Swingle) was investigated. Lime was immersed with nitric acid at concentration 0, 5, 10 and 20 µg /l for 1 minute then kept at 4 C°. Changes in weight loss, total soluble solids (TSS), fruit firmness, ascorbic acid (vitamin C), and Chlorophyllase activity were evaluated periodically with 7 day intervals during storage. The results showed that lime immersed with 5µg/l SNP was significantly delayed the decrease of weight loss and firmness, also maintained the highest ascorbic acid and delayed the increase of total soluble solids contents during storage. Moreover, lime fruits treated with 20 ug/l SNP increased more slowly Chlorophyllase activity than the other treatments. This application of NO may be a useful method for extending shelf-life and maintaining quality of lime.

Beneficial Effects of Nitric Oxide Induced Mild Oxidative Stress on Post-Thawed Bull Semen Quality.

Cryopreservation of semen requires optimized conditions to minimize the harmful effects of various stresses. The main approach for protection of sperm against stress is based on the use of antioxidants and cryoprotectants, which are described as defensive methods. Recently, the application of controlled mild stressors has been de- scribed for activation of a temporary response in oocyte, embryo and somatic cells. In this study a sub-lethal oxidative stress induced by precise concentrations of nitric oxide (NO) has been evaluated for sperm during cryopreservation. In this experimental study, we used different concentrations of NO [0 µM (NO-0), 0.01 µM (NO-0.01), 0.1 µM (NO-0.1), 1 µM (NO-1), 10 µM (NO-10) and 100 µM (NO-100)] during cryopreservation of bull semen. Their effects on post-thawed sperm quality that included motility and velocity parameters, plasma mem- brane functionality, acrosome integrity, apoptosis status, mitochondrial activity and lipid peroxidation after freezing-thawing were investigated. Exposure of sperm before freezing to NO-1 significantly increased total motility (88.4 ± 2.8%), progressive motility (50.4 ± 3.2%) and average path velocity (VAP, 53.8 ± 3.1 µm/s) compared to other extenders. In addition, NO-1 significantly increased plasma mem- brane functionality (89.3 ± 2.9%) compared to NO-0 (75.3 ± 2.9%), NO-0.01 (78.3 ± 2.9%), NO-0.1 (76.4 ± 2.9%), NO-10 (64 ± 2.9%) and NO-100 (42 ± 2.9%). Sperm exposed to NO-1 produced the highest percentage of viable (85.6 ± 2.3%) and the lowest percentage of apoptotic (10.8 ± 2.4%) spermatozoa compared to the other extenders. Also, NO-100 resulted in a higher percentage of dead spermatozoa (27.1 ± 2.7%) compared to the other extenders. In terms of mitochondrial activity, there was no significant difference among NO-0 (53.4 ± 3.2), NO-0.01 (52.1 ± 3.2), NO-0.1 (50.8 ± 3.2) and NO-1 (53.1 ± 3.2). For acrosome integrity, no significant different was observed in sperm exposed to different concentrations of NO. Induction of sub-lethal oxidative stress with 1 µM NO would be beneficial for cryopreservation of bull semen.

A novel fluorescence probe 9-(4-(1,2-diamine)benzene-N1-phenyl)acridine for nitric oxide determination

A novel fluorescent probe 9-(4-(1,2-diamine)benzene-N1-phenyl)acridine (DABPA) was synthesized for the detection of nitric oxide (NO) and characterized by IR, 1H-NMR and EI-MS spectroscopy. Based on a photoelectron transfer mechanism, the fluorescence intensities of DABPA were investigated with the different concentrations of NO. Under the optimal experimental conditions, the fluorescence intensity of DABPA had a good linear relationship (R2=0.9977) with NO concentration in the range from 1×10−7 to 1.5×10−6 mol/L with a detection limit of 1×10−8 mol/L. The cytotoxicity induced by DABPA was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide) assay for biological application. Furthermore, the probe DABPA had also been successfully applied to real-time image NO produced in PC12 cells in the presence of L-arginine.

β-galactosyl-pyrrolidinyl diazeniumdiolate: an efficient tool to investigate nitric oxide functions on promoting cell death

Nitric oxide (NO) is an active free radical gas that plays crucial roles in a broad range of biological processes. Extremely short half-life makes it difficult to use NO directly in research. It has been suggested that different concentrations of NO may lead to quite opposite results on cytotoxicity. However, the net effect of intracellular NO on tumor cell death has been controversial, partly because it is hard to precisely control the amount of NO generated exclusively within the target cells. Therefore, we have developed a cell-specific NO donor, β-galactosyl-pyrrolidinyl diazeniumdiolate (β-Gal-NONOate), in hopes of simulating the actual effects of intracellularly derived NO on the patterns of cell death as well as investigating its underlying mechanisms. In this study, by using three different tumor cell models, we showed that β-Gal-NONOate could steadily transport NO into the target cells with similar delivery efficiencies and exerted a determinative effect on cell death. In addition, β-Gal-NONOate-derived intracellular NO could provoke both apoptosis and necrosis in a concentration-dependent manner. While lower NO concentration primarily induced apoptosis, higher NO concentration mainly triggered necrosis. Moreover, the intrinsic apoptotic pathway, characterized by rapid Ca²⁺ overload and subsequent mitochondrial damage, was the collective mechanism responsible for the apoptotic death in all the three tumor cell lines. Taken together, since this cell-specifically derived NO is cheap to use and easy to quantify, β-Gal-NONOate might be used as a novel and ideal tool to standardize intracellular NO generation and evaluate its net effects in different cellular and experimental settings in the coming future.

Label-Free Quantitative Proteomics Analysis of Cotton Leaf Response to Nitric Oxide

To better understand nitric oxide (NO) responsive proteins, we investigated the proteomic differences between untreated (control), sodium nitroprusside (SNP) treated, and carboxy-PTIO potassium salt (cPTIO, NO scavenger) followed by SNP treated cotton plants. This is the first study to examine the effect of different concentrations of NO on the leaf proteome in cotton using a label-free approach based on nanoscale ultraperformance liquid chromatography-electrospray ionization (ESI)-low/high-collision energy MS analysis (MS(E)). One-hundred and sixty-six differentially expressed proteins were identified. Forty-seven of these proteins were upregulated, 82 were downregulated, and 37 were expressed specifically under different conditions. The 166 proteins were functionally divided into 17 groups and localized to chloroplast, Golgi apparatus, cytoplasm, and so forth. The pathway analysis demonstrated that NO is involved in various physiological activities and has a distinct influence on carbon fixation in photosynthetic organisms and photosynthesis. In addition, this is the first time proteins involved in ethylene synthesis were identified to be regulated by NO. The characterization of these protein networks provides a better understanding of the possible regulation mechanisms of cellular activities occurring in the NO-treated cotton leaves and offers new insights into NO responses in plants.

Relationship between rate of change of DAF‐2T fluorescence and nitric oxide (NO) concentration in vitro

DAF‐2 has been used for measurements of NO in vitro and in vivo, by virtue of its reaction with an auto‐oxidation product of NO to form the strongly fluorescent product DAF‐2T. Previously, we reported that the rate of change of DAF‐2T fluorescence was proportional to [NO]2, as predicted by the reaction kinetics of NO and DAF‐2 in the presence of O2. In the present study we demonstrated the influence of light intensity that promoted photobleaching and the importance of [O2] on the reaction between DAF‐2 and NO. The generation of DAF‐2T was evaluated in mixtures of 10 μM DAF‐2 with different concentrations of NO (range 100–1200 nM) made by mixing appropriate proportions of PBS equilibrated with room air with PBS equilibrated with 800 ppm NO/balance N2 (1200 nM NO); this procedure produced mixtures with varied PO2. Sequences of fluorescence images (at 10‐sec intervals over 300 sec) were acquired with a digital camera. Light intensities normally used in microscopic measurements induced strong photobleaching when the solutions were illuminated at intervals of 1‐10 sec. To avoid photobleaching, the incident light was attenuated using a 10% transmission neutral density filter. The non‐linear relationship between DAF‐2T fluorescence and [NO] was adequately described by the chemical kinetic model when the PO2 of the mixture was taken into account. These results are being used to interpret DAF‐2T fluorescence in terms of [NO] in vitro. Supported by NIH grants HL18292 and HL 79087.

The Fundamental Experiments of Red Tide Chemical Forecast

Many food algae and red tide algae were cultivated in the f/2 medium, and the nitric oxide (NO) concentration of the medium and the cell density were determined. The experiments on algae were conducted when different concentrations of NO were added into the medium using two methods. The results show that low concentrations of NO were self-produced by marine algae during the exponential growth period and were about nmol/L level. But at the end of the period, i.e., 2 or 3 days before the cell density reaches the maximum, an NO peak appeared, with the NO concentration reaching 10 nmol/L. The NO threshold concentration exists according to the influence of exogenous NO on the marine phytoplankton growth. One type is the threshold concentration that can promote algae growth, and its value is between 10 and 1 nmol level, or even lower. The other type can inhibit the phytoplankton growth, which is about μmol level or higher. The results indicate that red tide algae are far more sensitive to NO than are food algae. The fundamental experimental outcome above may provide a new clue for red tide chemical forecast by inspecting the NO change.

Different Doses of Nitric Oxide Donor Prevent Osteoporosis in Ovariectomized Rats

Nitric oxide has important effects on bone cell function. To verify that nitric oxide can protect against bone loss associated with estrogen deficiency, which is dependent on different concentrations of nitric oxide, we applied different doses of nitric oxide to ovariectomized rats. Fifty 12-week-old Sprague-Dawley female rats had ovariectomies, and 10 rats had sham operations. The ovariectomized rats were randomized into five groups: ovariectomized only; 17-beta-estradiol; low-dose nitroglycerin; middle-dose nitroglycerin; and high-dose nitroglycerin. After 12 weeks, the bone mineral density, dry weight, ash weight, calcium content, and nitric oxide concentration were determined. Compared with these same measurements in the sham-operated group, the bone mineral density, dry weight, ash weight, calcium content, and nitric oxide concentration decreased in the control group. Treatment with low-dose nitroglycerin, middle-dose nitroglycerin, and 17-beta-estradiol maintained bone mineral density and reversed the effects of ovariectomy on dry weight, ash weight and calcium content when compared with those in the control group. There were no differences in the bone mineral density, dry weight, ash weight, or calcium concentration between the ovariectomized-only rats and the rats treated with high-dose nitroglycerin. Results of this study suggest that nitric oxide treatment can counteract bone loss in ovariectomized rats. Furthermore, supplementation with a similar or slightly greater than physiologic concentration of nitric oxide has a potentially positive impact on osteoporosis.

Production of nitrogen dioxide during nitric oxide therapy using the Servo Ventilator 300 during volume-controlled ventilation.

Inhaled nitric oxide may be useful in the treatment of pulmonary hypertension and hypoxaemia. Nitric oxide is rapidly oxidized to nitrogen dioxide, which is toxic and may adversely affect the airways of the patient. The aim of the present investigation was to examine factors that may affect the concentration of nitrogen dioxide, using the Servo Ventilator 300 nitric oxide delivery system, where nitric oxide is flow-proportionally mixed with the main ventilatory flow in the proximal part of the inspiratory limb. In this experimental study nitric oxide and nitrogen dioxide levels were measured at the inspiratory site of a Y-piece with a chemiluminescence analyzer and electrochemical fuel cells. The effects of different concentrations of nitric oxide and oxygen, minute volume, different tube lengths, a soda lime absorber, and a humidifier placed in the inspiratory limb were evaluated. The concentration of nitrogen dioxide was dependent on the concentrations and residence time of nitric oxide with oxygen and the minute volume ventilation used. A soda lime absorber reduced concentrations of nitrogen dioxide at the expense of almost corresponding reductions in inhaled concentrations of nitric oxide. A humidifier increased the concentration of nitrogen dioxide, to an extent depending on the water volume and temperature used. Concentrations of nitric oxide and oxygen, minute volume ventilation, and residence time in the inspiratory part of the ventilatory circuit were factors that affected the generation of nitrogen dioxide. A soda lime absorber in this system is not recommended.

Partial liquid ventilation combined with inhaled nitric oxide in acute respiratory failure with pulmonary hypertension in piglets.

This study was a prospective, randomized, controlled design to evaluate gas exchange, lung mechanics, and pulmonary hemodynamics during partial liquid ventilation (PLV) combined with inhaled nitric oxide (NO) in acute respiratory failure (ARF) with pulmonary hypertension (PH). ARF with PH was induced in 12 piglets weighing 9.7-13.7 kg by repeated lung lavages and the continuous infusion of the stable endoperoxane analog of thromboxane. Thereafter the animals were randomly assigned either for PLV or conventional mechanical ventilation (CMV) at a fractional concentration of inspired O2 (Fio2) of 1.0. Perfluorocarbon (PFC) liquid (30 mL kg-1) was instilled into the endotracheal tube over 5 min followed by 5 mL kg-1h-1. All animals were treated with different concentrations of NO (1-10-20 ppm) inhaled in random order. Continuous monitoring included ECG, right atrial (Pra), mean pulmonary artery (Ppa), pulmonary capillary (Ppc'), and mean arterial (Pa) pressures, arteria oxygen saturation, and mixed venous oxygen saturation measurements. During PLV Pao2/Fio2 increased significantly from 8.2 +/- 0.4 kPa to 34.8 +/- 5.1 kPa (p < 0.01), whereas Pao2/FiO2 remained constant at 9.5 +/- 0.4 kPa during CMV. The infusion of the endoperoxane analog resulted in a sudden decrease of Pao2/Fio2 from 34.8 +/- 5.1 kPa to 14.1 +/- 0.4 kPa (p < 0.01) in the PLV group and from 9.5 +/- 0.4 kPa to 6.9 +/- 0.2 kPa (p < 0.05) in the control group. Inhaled NO significantly improved oxygenation in both groups (Pao2/Fio2: 45.7 +/- 5.3 kPa during PLV and 25.9 +/- 4.7 kPa during CMV). During inhalation of NO mean Ppa decreased significantly from 7.8 +/- 0.26 kPa to 4.2 +/- 0.26 kPa (p < 0.01) in the PLV group and from 7.4 +/- 0.26 kPa to 5.1 +/- 0.13 kPa (p < 0.01) in the control group. As documented in the literature PLV significantly improves oxygenation and lung mechanics in severe ARF. In addition, when ARF is associated with severe PH, the combined treatment of PLV and inhaled NO improves pulmonary hemodynamics resulting in better oxygenation.