Search

Comorbidities (chronic obstructive pulmonary disease, hypertension, diabetes, coronary artery disease and heart failure) more frequent in obese patients, respiratory physiological changes such as decreased compliance of the respiratory system, atelectasis and hypoxemia related to decreased functional residual capacity and limitation of expiratory flow, and diaphragmatic dysfunction, contribute to difficulties or failures of weaning and extubation in obese patients. The half-sitting or sitting position is a necessary prerequisite for the weaning of these patients. Some pulmonary function tests performed at the bedside can help in the management of weaning: vital capacity and maximum inspiratory pressure to assess the readiness to wean. In difficult weaning, the same parameters and maximum expiratory pressure are suggested as a prerequisite before considering extubation. The PS-PEEP mode is preferred in difficult weaning. Because of the triad atelectasis / pulmonary shunt / hypoxemia and the need to counterbalance intrinsic PEEP, PEEP withdrawal will be gradual. The use of prophylactic NIV in these patients reduces extubation failure and may be recommended. An impact on survival is observed in some hypercapnic obese patients, and prophylactic NIV for 48 hours after extubation should be systematic in this situation.

Introduction Bien que l’efficacite clinique de la ventilation non invasive (VNI) soit clairement demontree, il n’existe aucune etude recente a propos des conditions de prescription et d’utilisation de celle-ci selon les differentes pathologies respiratoires. La cohorte ANTADIR–GAV a pour objectif d’analyser prospectivement les donnees en France des patients relevant d’une VNI a domicile. Methodes Etude multicentrique prospective et observationnelle. L’etiologie de l’insuffisance respiratoire chronique (IRC), les donnees demographiques, les comorbidites, les gaz du sang (GDS), les donnees fonctionnelles respiratoires, le type de ventilateur, le mode, les parametres ventilatoires et les interfaces ont ete collectees. Resultats De mai 2015 a decembre 2016, 964 patients (54 % hommes, âge 64 ± 14 ans, IMC 28 ± 10 kg/m2) ont ete inclus dans 19 centres. L’IRC etait d’origine neuromusculaire chez 51 % des patients, parenchymateuse chez 25 % ou due a une pathologie de la cage thoracique chez 24 %. Les etiologies les plus frequentes etaient : sclerose laterale amyotrophique (36 %), BPCO (22 %) et SOH (19 %). Les principales comorbidites etaient : hypertension (40 %), diabete (18 %), arythmie (13 %) et maladie coronaire (8 %). Les GDS avant VNI etaient : PaO2 73 ± 14 et PaCO2 49 ± 8 mmHg. La majorite des patients a ete ventilee par un ventilateur monobranche avec fuite (99 %). Au total, 83 % des patients etaient ventiles en mode ST, 10 % en mode S et 4 % avec un mode hybride. Chez 892 patients (89,4 %) un ventilateur a double niveau de pression a ete utilise, sans batterie chez 47 % des patients ou avec batterie chez 45 %. Un ventilateur support de vie a ete necessaire chez 8 % des patients. L’IPAP, l’EPAP et la frequence de securite ont ete respectivement 16 ± 4 cmH2O, 7 ± 3 cmH2O et 15 ± 3 c/min. L’interface la plus utilisee a ete un masque oronasal (80 % des patients). L’adjonction d’O2 a ete necessaire chez 32 % des patients. La VNI a ete mise en route apres un episode aigu chez 43 % des patients (26 % en reanimation, 23 % en SI de pneumologie et 50 % en salle de pneumologie) et a l’etat stable chez 57 % (58 % en hospitalisation conventionnelle, 36 % en hopital de jour, 6 % a domicile), Les criteres principaux pour l’initiation de la VNI ont ete les GDS (51,8 % des patients), les symptomes (33,3 %) et les explorations nocturnes (8,9 %). Conclusion Cette cohorte prospective offre une analyse fiable et representative de la realite de la VNI a domicile en France et ouvre de nouvelles perspectives pour l’organisation de sa prise en charge et la recherche clinique.

The assessment of severity. Severity assessment is a key element in the management of community-acquired pneumonia. This assessment will determine the level of diagnostic workup and treatment, as well as the site of care. Several tools have been developed to help this assessment. The Pneumonia Severity Index (PSI) or the CURB-65 can accurately identify patients with a low risk of death who might be considered for outpatient care while those with a high risk of death would be hospitalized. Nevertheless, PSI and CURB-65 are less accurate for identifying patients requiring admission to an intensive care unit (ICU). Different scores, such the American Thoracic Society criteria or the SMART-COP score, were built to predict need for admission to ICU, vasopressors or mechanical ventilation. Each score has its own strengths and weaknesses and physicians must be aware of these limitations. Although, severity assessment tools are useful guides in the management of patients with community acquired pneumonia, clinical judgment must remain decisive.

Resume Introduction La capacite inspiratoire (CI), reflet de la distension pulmonaire dynamique es t correlee au devenir du malade avec BPCO en exacerbation. Il n’y a pas d’etude en cas d’insuffisance respiratoire aigue (IRA). Methodes Cette etude prospective multicentrique (3 services de reanimation et 1 service de pneumologie) evalue la faisabilite, la reproductibilite et l’evolution de la CI et son lien avec le devenir des patients avec BPCO en IRA. Ont ete mesurees l’echelle visuelle analogique de dyspnee, la CI et l’evolution du patient classee en non favorable (deces ou intubation ou ventilation non invasive ou admission en reanimation) et favorable (absence des criteres precedents). Resultats Cinquante patients ont ete inclus et 48 analyses. La mesure de la CI a ete possible chez tous les malades sauf un et le coefficient de variation est de 9 ± 8 %. Entre admission et sortie, la CI passe de 39,9 ± 15,5 a 50,2 ± 14,5 % predit (p Conclusions Chez les BPCO en IRA, la mesure de la CI est faisable et reproductible. Il existe une tendance entre la variation de la CI et l’evolution du patient.

Resume Puisque l'interface est un determinant majeur de l'efficacite de la ventilation non invasive (VNI), il convient d'essayer d'optimiser son choix pour chaque patient. Cette optimisation repose sur plusieurs facteurs complementaires. Le choix du masque qui convient le mieux a un malade donne doit etre fait par quelqu'un d'experimente, un referent technique. Meme si un type d'interface satisfait la majorite des intervenants d'un service et est regulierement utilise, il faut continuer de tester les nouveaux modeles et d'enrichir la gamme des interfaces disponibles. En effet, de nombreux progres technologiques on ete realises dans la conception des interfaces pour ameliorer leur confort, reduire les complications et ainsi ameliorer leur tolerance et reduire les echecs de VNI. Concernant le choix de l'interface pour debuter la VNI dans l'insuffisance respiratoire aigue, l'efficacite ventilatoire reste la priorite et il nous parait logique de proposer le masque facial en premiere intention. Au meme titre qu'il convient d'evaluer precocement l'efficacite ventilatoire de la VNI, il faut evaluer rapidement la tolerance cutanee du masque et le niveau des fuites. Dans tous les cas il ne faut pas hesiter a changer d'interface. Le choix de deuxieme intention portera sur des masques faciaux de nouvelles generations ou les masques faciaux totaux. Le casque de ventilation connait un engouement considerable en Italie et d'excellents resultats ont ete rapportes. Cependant, cette interface peut etre responsable d'un surcroit de travail ventilatoire et de dyspnee, d'un risque potentiel de re-inhalation de CO2, a bien mettre en balance avec le benefice majeur obtenu en respectant l'integrite de la face. En pratique, dans de nombreuses unites incluant la notre, l' « helmet » n'est utilise qu'en deuxieme, voire troisieme, intention comme alternative au masque facial en cas de lesions cutanees responsables d'intolerance avec un risque d'echec de la methode.

Resume Malgre la frequence des asthmes aigus graves, les progres de la prise en charge ont rendu la ventilation mecanique exceptionnelle. Les indications de la ventilation mecanique comme pour toute insuffisance respiratoire aigue sont liees a l'existence de signes de detresse vitale non immediatement reversibles sous traitement ou a l'aggravation secondaire des patients chez lesquels le traitement s'est avere inefficace et qui s'epuisent. La ventilation mecanique des patients presentant un asthme grave est chargee de difficultes. L'objectif de la ventilation mecanique n'est plus l'amelioration ou la normalisation a tout prix des gaz du sang mais une solution de relais des muscles respiratoires sans autre objectif que d'assurer une PaO2 correcte en evitant un arret cardiorespiratoire par epuisement et en evitant tout risque barotraumatique. Ces conditions de ventilation aboutissent a une hypercapnie, dite permissive ou toleree, qui pourra atteindre parfois des niveaux tres eleves, en attendant que le traitement medical devienne efficace. Il s'agit donc d'une ventilation minimale de securite. Une surveillance etroite de l'etat du patient et un monitoring sont necessaires pour eviter les complications et pour identifier le moment approprie pour le sevrage.

Many small fish, including several juvenile Atlantic flatfish, are most abundant in shallow areas presumable because these habitats enhance survivorship and/or growth. In this study, we investigated size-dependent depth distributions and the role of shallow habitats as predator refuges for age-0 winter flounder (Pseudopleuronectes americanus) in a northwest Atlantic estuarine nursery. Analysis of trawl surveys performed during the larval settlement period throughout the Navesink River and Sandy Hook Bay, New Jersey, showed that as fish increased in size, depth of occurrence gradually decreased, so that individuals >35 mm standard length (SL) were concentrated in habitats ∼1 m deep. Tethering in structurally simple and adjacent shallow and deep habitats showed that predation risk for flounder (30–50 mm SL) was low in shallow water (

Acute asthma is well known to provoke complications. We report the case of a patient who needed intubation and mechanical ventilation for acute asthma. Despite a treatment with corticosteroids, bronchodilators, neuromuscular blocking drugs and magnesium sulfate, the situation remained uncontrolled and as a last resort, halothane became necessary. The patient then developed an episode of malignant hyperthermia with fever at 40 degrees C and rhabdomyolysis. At this time, halothane could be stopped and all the symptoms disappeared without modifying the rest of the treatment. Eight days later, he presented with a neuroleptic malignant syndrome following an injection of droperidol. Temperature rose to 42 degrees C, associated with muscle rigidity, sweating, tachycardia and severe circulatory collapse. The use of dantrolene in association with a symptomatic treatment of the collapse led to a favourable outcome in. Unfortunately, in vitro contracture test could not be performed in this case. The links between malignant hyperthermia and neuroleptic malignant syndrome remain unclear. Although these two pathologies share the same physiopathology, symptomatology and treatment, they are clearly individualized. This case seems to be the first description of their occurrence in the same patient.

Non-invasive ventilation (NIV) is increasingly used in patients with acute respiratory failure, but few data exist regarding current sedation practices during NIV. Mask intolerance or claustrophobia, and delirium and agitation, may lead to NIV failure, requiring endotracheal intubation. Judicious use of sedation during NIV could be one of the valuable options for some of these patients at risk of intubation. Although different sedatives have been used in published studies, the objectives of sedation are similar: allowing mitigation of patient discomfort and obtaining the desired level of sedation. Whatever the sedative used, the goal is to achieve sedation to a point where the patients are awake and arousable and comfortable. Pilot studies suggest that continuous infusion of a single sedative agent may decrease patient discomfort, with no significant effects on respiratory drive, respiratory pattern, or hemodynamics. In addition, gas exchange improved under NIV with sedation. While the current limited data available suggests that sedation during NIV is safe and feasible, more widespread application should await the results of randomized clinical trials.

Weaning patients with heart failure who have required mechanical ventilation remains challenging. We evaluated echocardiographic indexes and N-terminal pro-brain natriuretic peptide (NT-proBNP) as markers of acute cardiac dysfunction before and after spontaneous breathing trials (SBT) in such patients to assess their ability to predict subsequent successful extubation.Forty-four patients who underwent their first SBT were prospectively included. Plasma levels of NT-proBNP and transthoracic echocardiography indices including cardiac index, E/A ratio and E/Ea ratio were recorded immediately before commencing and just before the end of SBT.Ten patients (22.7%) failed their SBT. No significant difference was observed concerning baseline echocardiographic data and NT-proBNP level between the patients who succeeded the SBT or those that failed. Cardiac index increased significantly at end-SBT in patients who passed (3.3 [3.06-3.77] vs. 3 [2.68-3.3] L/min/m(2), P0.001), whereas it remained unchanged in those that failed. E/Ea ratio (16.8 [8.5-27.3] vs. 10.7 [6.7-20.5], P=0.006) and NT-proBNP level (8199 [3106-10949] vs. 4200 [1855-7125] pg/mL, P=0.004) increased significantly in those who failed the SBT, in contrast to the weaning success group where they remained unchanged.Neither NT-proBNP level nor the studied echocardiographic indices before SBT were able to predict SBT outcome in patients presenting with severe heart failure. Failure to increase the cardiac index and increases in both E/Ea ratio and NT-proBNP levels were seen at end-SBT in patients who failed the SBT, and may reflect failure of myocardial reserve to cope with the stress of SBT.

Currently, the assessment of ultrasonic methods on pumice bricks is not a state-of-the-art technology. The vault of a neo-Gothic church made of pumice brick showed large cracks resulting from World War II and the structure of other areas was damaged. Normally, tasks like these are solved by visual inspection combined with drilling cores at a few measuring points. By this means, only the surface and just a few areas of the structure can be inspected. With ultrasonic echo it is possible to study the internal structure of the vault laminar. The investigations are non-destructive and have no effect on the monument.

The assessment of severity. Severity assessment is a key element in the management of community-acquired pneumonia. This assessment will determine the level of diagnostic workup and treatment, as well as the site of care. Several tools have been developed to help this assessment. The Pneumonia Severity Index (PSI) or the CURB-65 can accurately identify patients with a low risk of death who might be considered for outpatient care while those with a high risk of death would be hospitalized. Nevertheless, PSI and CURB-65 are less accurate for identifying patients requiring admission to an intensive care unit (ICU). Different scores, such the American Thoracic Society criteria or the SMART-COP score, were built to predict need for admission to ICU, vasopressors or mechanical ventilation. Each score has its own strengths and weaknesses and physicians must be aware of these limitations. Although, severity assessment tools are useful guides in the management of patients with community acquired pneumonia, clinical judgment must remain decisive.

A major driving force behind the increasing use of non-invasive ventilation (NIV) has been the desire to avoid the complications of invasive ventilation. Although invasive mechanical ventilation is highly effective and reliable in supporting alveolar ventilation, endotracheal intubation is associated with numerous risks of complications. These include upper-airway injuries, tracheal stenosis, tracheomalacia, sinusitis, and ventilator-associated pneumonia [1]. Torres et al. considered the correlation between several risk factors and the development of nosocomial pneumonia: the presence of chronic obstructive pulmonary disease (COPD) and invasive ventilation for more than 3 days were significantly associated with an increased risk [2]. This complication of invasive ventilation is associated with a longer stay in the intensive care unit (ICU), increased costs and a worse outcome [2]. Furthermore, weaning difficulties are frequent in COPD patients [3], and the management of difficult-to-wean patients is a major clinical challenge that constitutes a large portion of the workload in an ICU [4].

Inspiratory Capacity (IC), which reflects dynamic pulmonary hyperinflation, correlates with outcome in moderate exacerbation of COPD. Whether this is also true in COPD with acute respiratory failure (ARF) has not been studied.A prospective multicenter assessment of IC measurement feasibility, reliability, time-course and relationship to outcome in COPD with ARF was conducted. Dyspnea (visual analogue scale) and IC were repeatedly measured. Outcome was classified as not favourable (death or intubation or non invasive ventilation increased or patient referred to ICU from respiratory ward) or favourable (none of the above criteria).Fifty patients were included and 48 analysed. IC measurement was possible in all but one patient and its coefficient of variation was 9+/-8%. Between inclusion into the study and discharge, IC increased from 39.9+/-15.5 to 50.2+/-14.5% pred (p0.001) and dyspnea declined from 48+/-23 to 33+/-22 mm (p0.001). Inclusion IC was not different on average between patients with or without favourable outcome.In COPD patients with ARF, IC measurement at bedside was feasible and reproducible. IC was low at entry and increased over time from inclusion to discharge tending to correlate with patient outcome.

In immunosuppressed patients with acute respiratory insufficiency (ARI) mechanical ventilation is associated with a high mortality. Therefore, in this situation, avoidance of intubation could be an important objective. However, experience of non-invasive ventilation (NIV) in the immunosuppressed remains limited.The first descriptive studies have shown that NIV could be an alternative to intubation, particularly in patients with malignant haematological disorders. In a prospective randomised controlled study Antonelli et al. showed that the use of NIV significantly improved the prognosis of patients with ARI following organ transplantation. We have carried out a prospective randomised controlled trial in 52 immunosuppressed patients to determine whether NIV improved the prognosis in patients admitted to intensive care with pulmonary infiltrates, fever and ARI. The use of NIV was associated with significant reductions in the intubation rate, serious complications and ICU and hospital mortality.Further studies are needed in order to better define the patients susceptible to benefit from NIV, and to establish variables predictive of the success or the failure of the method.NIV leads to an improvement in the prognosis of some immunosuppressed patients admitted to intensive care.

The combination of neurofibromatosis type I with hyperparathyroidism is classical but rare.Our report is on the original observation of a patient affected with Von Recklinghausen's disease complicated by chronic restrictive breathing deficiency. After an intense breathing decompensation and a spreading convulsive attack, hyperparathyroidism was diagnosed.The similarity of the bone lesions seen in type I neurofibromatosis and in hyperparathyroidism strongly suggests a genetic link between these two pathologies. Hence, hyperparathyroidism should be searched for in all patients affected with Von Recklinghausen's disease, since the adjustment of hypercalcemia can lead to partial reversibility of the bone abnormalities.

Bacterial resistance, encountered most often in intensive care units (ICUs) increases with time. This resistance is associated with a high death rate and a significant rise in cost. It is now recognized that resistance to antibiotics in the ICU is a problem, that influences the patients’ outcome [1]. This negative outcome could be due to a delay in prescribing a well-adapted and effective antibiotic.

The study of global and segmental left ventricular function forms part of every echocardiographic examination. However, this is only possible when the endocardial borders are well identified. The authors report the results of a study with Albunex, a first generation contrast agent used by intravenous injection. The object of this study was to assess the efficacy of Albunex in improving left ventricular endocardial detection compared with standard transthoracic echocardiography (TTE) and the dose-effect relationship. Forty-one patients were included prospectively at two cardiological hospital centres between 1995 and 1997, before the development of second harmonic imaging. Two patients were excluded from the study. Each patient underwent transthoracic echocardiography in the fundamental mode with an apical four-chamber view. The following procedure was adopted: 1) standard examination, 2) low dose Albunex (0.1 mg/Kg) injected via a peripheral vein, 3) high dose Albunex (0.2 mg/Kg) injected via a peripheral vein, 4) low dose Albunex injected via a central vein, 5) high dose Albunex injected via a central vein. The analysis of results was performed by two independent observers and showed that Albunex improved endocardial detection (p0.005); this detection was significantly better with high doses of Albunex and with central vein injection (p0.005); the septal border was better visualised than the lateral wall endocardium (p0.005) but the improvement in endocardial detection was greater for the lateral wall (p0.005). No complications were observed during the procedure. The authors conclude that Albunex improves left ventricular endocardial detection. This benefit is mainly due to improved lateral wall detection, and increases with higher doses of the contrast agent.

Different etiologies have been shown to underly lethal midline granuloma. Evidence of natural killer cell lymphoma is obtained by immunolabeling and molecular biology studies. The tumor has a characteristic immunophenotype and genotype. This clinicopathological entity is highly associated with Epstein-Barr virus (EBV). We present the case of a patient with EBV associated with nasal-type natural-killer cell lymphoma and a coexisting hemophagocytic syndrome.

The paper presents results of analyses of 4182 samples collected from January 1995 to December 1996 for the Danish National Pesticide Monitoring Program. The program basis is a random sample control supplemented with a target control. The objectives of the control are to monitor consumer exposure to health hazards and to enforce national and European Community regulations. The Danish Veterinary and Food Administration is responsible for establishing methods, data manipulation, and evaluation, but actual analyses are performed at 4 regional laboratories. In addition to a description of the Danish National Pesticide Monitoring Program on food, the effects of lowering the reporting limits are discussed. Pesticides included are those in current use as well as chlorinated pesticides like lindane, DDT, and HCB, occurring in food now primarily as a result of environmental contamination. Commodities analyzed are fruits, vegetables, cereals, bran, fish, and animal products such as meat, butter, cheese, fat, and eggs. In fruits and vegetables, residues were detected in 10% of 2515 samples, with higher incidences of detection for foreign commodities. Violation rate was 0.6%. In food of animal origin, low levels of organochlorine pesticides were detected in most fish samples and in more than half of the animal product samples. However, no results exceeding maximum residue limits were found. No residues of organophosphorus pesticides were detected in the 231 meat samples analyzed.

Acute asthma is well known to provoke complications. We report the case of a patient who needed intubation and mechanical ventilation for acute asthma. Despite a treatment with corticosteroids, bronchodilators, neuromuscular blocking drugs and magnesium sulfate, the situation remained uncontrolled and as a last resort, halothane became necessary. The patient then developed an episode of malignant hyperthermia with fever at 40 degrees C and rhabdomyolysis. At this time, halothane could be stopped and all the symptoms disappeared without modifying the rest of the treatment. Eight days later, he presented with a neuroleptic malignant syndrome following an injection of droperidol. Temperature rose to 42 degrees C, associated with muscle rigidity, sweating, tachycardia and severe circulatory collapse. The use of dantrolene in association with a symptomatic treatment of the collapse led to a favourable outcome in. Unfortunately, in vitro contracture test could not be performed in this case. The links between malignant hyperthermia and neuroleptic malignant syndrome remain unclear. Although these two pathologies share the same physiopathology, symptomatology and treatment, they are clearly individualized. This case seems to be the first description of their occurrence in the same patient.

Hepatitis due to Herpes Simplex Virus (HSV) is a rare and severe infection in patients with impaired immunity, as bone marrow transplanted. The antemortem diagnosis is often difficult to establish because the clinical features are nonspecific. We report an uncommon cause of fulminant hepatic failure in a neutropenic patient, 14 days after bone marrow transplantation. HSV-2 fulminant hepatitis occurred during acyclovir prophylactic treatment. No observation of HSV hepatitis in this context has been reported since prophylaxis is used. Because of the extremely high apparent mortality associated with HSV hepatitis, and the improved survival noted among the non-marrow-transplant recipients and prolonged survival seen in one marrow transplant recipient, it seems reasonable to urge early and aggressively acyclovir therapy. A liver biopsy seems to be indispensable in the case of hepatic failure in post-marrow-transplantation in order to make rapidly a diagnosis.

Fourty-six patients requiring mechanical ventilation and suspected of bacterial pneumonia were examined by fiberoptic bronchoscopy. Specimens recovered by bronchoalveolar lavage (BAL) and using a protected specimen brush (PSB) were quantitatively cultured and the results compared. An assessment of the percentage of cells with intracellular organisms present on cytocentrifuged preparations made from lavage fluid was made to evaluate the utility of this method in early diagnosis of pneumonia. BAL cultures made a correct diagnosis in 43 out of 46 patients and detected 10 false-negative cultures of the PSB. With a threshold of more than 3% of cells with intracellular bacteria, direct microscopic examination diagnosed bacterial pneumonia in 36 out of 46 patients and allowed appropriate antibiotherapy to be instituted earlier. These results demonstrate the ability of BAL to diagnose bacterial pneumonia in ventilated patients.

“Ready-to-use” grated carrots were packaged in different films (oxygen permeability from 950 to 22,000 cc/m2/day/atm at 25°C) and stored at 2, 6 or 10°C for 10 days. Gaseous atmosphere in packs and the following were monitored: lactic acid bacteria, yeast counts, exudate and potassium ion released, sugars, carotene, ethanol and lactic acid. The respiration rate of the packaged carrots was measured. Films with very low oxygen permeability resulted in anaerobic respiration, high leakage of potassium, and high lactic acid bacteria. With high-permeability films (between 10,000 and 20,000 cc/m2/day/atm at 25°C), grated carrots showed aerobic respiration and retained good quality. At 10°C, in carrots packed in the most permeable film, sucrose decreased markedly during storage. The gas permeabilities required for packaging grated carrots were evaluated in relation to storage temperature.

Water-soluble nitrogen compounds play an important role in the acidification and eutrophication of our environment. The most abundant species are NH3 and HNO3 which both are present in gaseous and particulate forms. They can both be transported over long distances, especially in particulate form. In order to study this transport a network of stations in different countries has to be used. A prerequisite is of course that all laboratories involved use comparable measurement techniques. Another prerequisite is that the methods are so simple and inexpensive to use that a dense network can be established even at remote places. Several field experiments have been performed in which techniques to measure the gaseous and particulate forms separately are compared. However, they have not been very successful. In this study three techniques to measure the total (gaseous and particulate) concentrations of NH4+ and NO3− were compared in field experiments. Comparison of measurements made by different laboratories in different countries using the same sampling technique at a given place yielded a relative standard deviation of 20% for total NH4+ and 15% for total NO3−. The same relative standard deviations were obtained when different sampling techniques (denuder, total filter, filter pack) were compared.