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The impact of carp pond effluents on natural waters was investigated in the German federal states of Brandenburg, Saxony and Bavaria, and in Hungary. Data from 38 ponds (size = 0.25–122 ha) were available for the calculation of inlet–outlet differences. An average difference of 0.51 kg phosphorus (P) ha−1 year−1 was obtained. This means that every hectare of pond surface releases 510 g P less than it receives from the incoming water. This result was independent of the amount of fish harvested (≤ 1500 ha−1 year−1). The average retention of P (P‐balance) was 5.71 kg P ha−1 year−1. Phosphorus retention increased with increasing intensity of production. Nitrogen (N) retention increased with production intensity from 78.5 kg ha−1 year−1 in German standard ponds to > 290 kg N ha−1 year−1in pig‐cum‐fish ponds in Hungary. A predominantly mineralized sludge suspension is released during harvesting at loads below 1% of the retention capacity of the pond. Under usual pond management regimes, the sludge load during harvesting ranged from 50 to 200 L ha−1, equivalent to 0.3–9.3 g dry matter ha−1. The present study suggests that ponds are not a burden on the environment. By contrast, these water bodies improve water quality. Therefore, pressures to reduce the intensity of pond production cannot be justified on the basis of supposed impacts on water quality. However, even if loads during harvesting are low compared with the retention capacity of the pond, more effort should be carried out to reduce the pollution of streams by pond outlets downstream. This can be done by limiting pond drainage to periods when the suspended material has settled or by short‐term sedimentation of the sludge in a settling pond downstream of the rearing facility.

Mechanical ventilation is required if ventilatory insufficiency is present. This is typically indicated by hypercapnea. Hypoxemia occurs secondary to hypoventilation. Usually overload of the respiratory muscles (ventilatory pump) will be the underlying mechanism, for the most part caused by acute or chronic disease. In case of sole hypoxemia mechanical ventilation will only be indicated if the oxygen-content (equals oxygen saturation x haemoglobin x 1.39) drops below a critical threshold or if ventilatory pump failure is imminent on account of the underlying disease (eg. pneumonia). The background of our recommendations is to avoid potential damage caused by mechanical ventilation. Especially high inspiratory pressures and oxygen concentrations can be harmful to the lung. Therefore every case has to evaluated for individual target parameters of ventilation. The use of the oxygen-content instead of the arterial oxygen pressure as the target parameter will usually lead to a more careful ventilation. Cardiogenic pulmonary oedema is an exception to this rule since inspiratory positive pressure and PEEP will result in improved diffusion as well as reduction of preload and work of breathing. In recent years progress has been made on the field of ventilation access especially in severe and acute cases. Non-invasive ventilation is superior to invasive ventilation in patients with exacerbated COPD since it improves outcome effectively. This is being caused by a decline in ventilator associated pneumonias, most likely because non-invasive ventilation allows patients to clear their secretions by coughing, resulting in improved lung clearance. Controlled ventilation allows optimal unloading of the respiratory muscles which have been overloaded by the underlying disease. Application of a controlled ventilation mode in acute disease will usually require some kind of sedation. Assisted ventilation will result in improved gas exchange but only incomplete unloading of respiratory muscles and therefore delayed restitution. Permanent controlled ventilation under sedation for a prolonged period (days) requires intermittent periods of assisted- or spontaneous breathing in order to avoid atrophy of the respiratory muscles. This review summarizes background information on the nature of the derangement, the relation between oxygen supply and consumption under special consideration of respiratory muscle insufficiency and impact of different ventilation modes.

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The advances in intensive and critical care medicine have not only improved the prognosis of patients with acute respiratory failure but have also increased the number of ventilator-dependent patients. The continuously increasing number of patients, the differentiation of care-giving institutions and the technical progress make it necessary to re-evaluate the quality of health care in weaning centres and outpatient care of patients on long-term ventilation. Therefore, the German medical associations of pneumology and ventilatory support, "Deutsche Gesellschaft für Pneumologie und Beatmungsmedizin e. V." and the "Arbeitsgemeinschaft für Heimbeatmung und Respiratorentwöhnung e. V.", wish to present this actual position paper. However, scientific guidelines are in preparation.