Humidified high-flow nasal oxygen therapy (HFNO) has, in recent years, come to assume a key role in the management of hypoxemic acute respiratory failure (ARF). While non-invasive ventilation (NIV) currently represents the first-line ventilatory strategy in patients exhibiting hypercapnic ARF, the operating principles and physiological effects of HFNO could be interesting and useful in the initial management of hypercapnic ARF and/or after extubation, particularly in acute exacerbations of chronic obstructive pulmonary disease. Under these conditions, HFNO could be used either alone continuously or in combination with NIV during breaks in spontaneous breathing, depending on the severity and etiology of the underlying hypercapnic ARF.

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COVID-19 pneumonia presents several particularities in its clinical presentation (cytokine storm, silent hypoxemia, thrombo-embolic risk) and may lead to a number of acute respiratory distress syndrome (ARDS) phenotypes. While the optimal oxygenation strategy in cases of hypoxemic acute respiratory failure (ARF) is still under debate, ventilatory management of COVID-19-related ARF has confirmed the efficacy of high-flow oxygen therapy and restored interest in other ventilatory approaches such as continuous positive airway pressure (CPAP) and noninvasive ventilation involving a helmet, which due to patient overflow are sometimes implemented outside of critical care units. However, further studies are still needed to determine which patients should be given which oxygenation technique, and under which conditions they require invasive mechanical ventilation, given that delayed initiation potentially burdens prognosis. During invasive mechanical ventilation, ventral decubitus and extracorporeal membrane oxygenation have become increasingly prevalent. While innovative therapies such as awake prone position or lung transplantation have likewise been developed, their indications, modalities and efficacy remain to be determined.

Although standard oxygen is the first-line therapy in patients with acute hypoxemic respiratory failure, high-flow nasal oxygen has gained major popularity in ICUs due to its simplicity of application, good comfort for patients, and efficiency in improving oxygenation. Physiological effects of high-flow oxygen therapy can limit the physiological consequences of acute hypoxemic respiratory failure and may mitigate the deleterious effects of high and prolonged inspiratory efforts generated by patients. Although clinical studies have reported a decreased risk of intubation with high-flow oxygen therapy as compared with conventional oxygen therapy, its benefits with regard to survival are uncertain. However, a more precise definition of acute hypoxemic respiratory failure including a classification of severity levels based on oxygenation levels is needed, the objective being to better compare the efficiency of different non-invasive oxygenation supports (conventional oxygen therapy, high-flow oxygen and non-invasive ventilation). Moreover, other clinical trials are needed to confirm the place and the benefit of these oxygenation supports, particularly high-flow nasal oxygen therapy, in acute hypoxemic respiratory failure, especially in the severe forms.

First-line symptomatic treatment of acute respiratory failure (ARF) usually requires standard oxygen therapy, of which the limits have nonetheless led to the development of heated and humidified high-flow nasal oxygen therapy (HFNO). HFNO enables the delivery, through simple nasal cannula, of up to 100% of well-heated and humidified fraction of inspired oxygen (FiO2), at a maximum flow rate of 50 to 70 L/min of gas according to the devices chosen (specific or ventilator). The technical characteristics and operating principles of HFNO (coverage of the patient\'s spontaneous inspiratory flow, improved conditioning of the inspired gases, comfortable nasal cannula) yield a number of interdependent physiological effects that improve not only oxygenation conditions but also ventilatory mechanics. While it could be indicated in many clinical situations, including first-line hypoxemic ARF, the simplicity of HFNO implementation and the respiratory comfort it procures should in no way minimize the clinical monitoring of patients for whom endotracheal intubation may be required, and should not be unduly delayed.

High flow oxygen via nasal cannula (HFO2NC) has become the first-line reference symptomatic treatment for hypoxemic acute respiratory failure. This non-invasive technique can be addressed, as palliative therapeutic care, to frail patients near end-of-life with a do-not-intubate order. A distinction will be made between those with an imminent and inevitable fatal outcome (pallitative end-of-life management) and those with hope for transient clinical remission (meliorative management). This review focuses on the expected physiological benefits and technical benefits/risks incurred by HFO2NC use in this population. Its main purpose is to highlight the ethical principles governing the palliative management of patients in acute respiratory failure with a do-not-intubate order, and to discuss the various elements to be considered when defining the patient\'s palliative care plan, in a holistic, individual-centered approach.

BACKGROUND: The intrathoracic manifestations of IgG4-related disease include a range of conditions and severity, and can on occasion cause acute respiratory failure as reported in the case described here.
METHODS: A 69-year-old male former smoker, was admitted to our hospital with dyspnea, fever, cough, fatigue, and a 3-month history of weight loss. He received high flow oxygen therapy and non-invasive ventilation for severe respiratory failure. Chest computed tomography revealed multifocal condensations and ground glass opacities, accompanied by thickening of the perilymphatic interstitium, mediastinal lymphadenopathy and bilateral pleural effusion. Elevated serum concentrations of IgG4 suggested an IgG4-Related Disease. He developed renal failure and underwent a renal biopsy. Histopathological analysis of which supported the diagnosis by showing dense lymphocytic infiltrate with a count of IgG4+ cells/hpf higher than 60, and storiform fibrosis - a swirling, \"cartwheel\" pattern of fibrosis which may have a patchy distribution. The patient responded well to steroid therapy.
CONCLUSIONS: Although respiratory symptoms are usually mild in IgG4-relatd disease, thoracic features can evolve into acute respiratory failure with few extra thoracic manifestations.

As a result of the constantly increasing epidemic of obesity, it has become a common problem in the intensive care unit. Morbid obesity has numerous consequences for the respiratory system. It affects both respiratory mechanics and pulmonary gas exchange, and dramatically impacts on the patient\'s management and outcome. With the potential for causing devastating respiratory complications, the particular anatomical and physiological characteristics of the respiratory system of the morbidly obese subject should be carefully taken into consideration. The present article reviews the management of obese patients in respiratory failure, from noninvasive ventilation to tracheostomy, including postural and technical issues, and explains the physiologically based ventilatory strategy both for NIV and invasive mechanical ventilation up to the weaning from the ventilatory support.

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BACKGROUND: The shrinking lung syndrome (SLS) is a rare complication of systemic lupus erythematosus.
METHODS: A 69-year-old man presented with exertional dyspnoea, muscle weakness, and weight loss of 15kg in 6months. Pulmonary function tests revealed a restrictive lung disorder, with a dramatic decrease in maximal inspiratory pressure (17% of theoretical value), and alveolar hypoventilation (pH 7.43; PaCO2 55mmHg). A thoracic CT-scan showed bilateral diaphragmatic elevation. The creatinine phophokinase level was increased at 280U/L. Progress was marked by a rapidly increasing respiratory acidosis (pH 7.24, PaCO2 109mmHg) requiring invasive ventilation. Auto-immune studies revealed positive anti-nuclear antibodies (1/800) and positive anti-native DNA antibody at 45U/L. Treatment with systemic corticosteroids led to an initial improvement but it was not possible to discontinue mechanical ventilation. The outcome was fatal. Autopsy did not reveal any other cause and a diagnosis of the SLS associated with lupus was confirmed.
CONCLUSIONS: The interesting features of this case report consist of: 1) the presentation of the SLS as an alveolar hypoventilation with a fatal outcome, 2) the presentation of systemic lupus as SLS.