Critical care : the official journal of the Critical Care Forum
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Observational Study
Physiological predictors of survival during high-frequency oscillatory ventilation in adults with acute respiratory distress syndrome.
Data that provide clinical criteria for the identification of patients likely to respond to high-frequency oscillatory ventilation (HFOV) are scarce. Our aim was to describe physiological predictors of survival during HFOV in adults with severe acute respiratory distress syndrome (ARDS) admitted to a respiratory failure center in the United Kingdom. ⋯ HFOV is effective in improving oxygenation in adults with ARDS, particularly when instituted early. Changes in PaO2/FiO2 during the first three hours of HFOV can identify those patients more likely to survive.
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Healthy piglets ventilated with no positive end-expiratory pressure (PEEP) and with tidal volume (VT) close to inspiratory capacity (IC) develop fatal pulmonary oedema within 36 h. In contrast, those ventilated with high PEEP and low VT, resulting in the same volume of gas inflated (close to IC), do not. If the real threat to the blood-gas barrier is lung overinflation, then a similar damage will occur with the two settings. If PEEP only hydrostatically counteracts fluid filtration, then its removal will lead to oedema formation, thus revealing the deleterious effects of overinflation. ⋯ High PEEP (and low VT) do not merely impede fluid extravasation but rather preserve the integrity of the blood-gas barrier in healthy lungs.
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Editorial Comment
The brain after critical illness: effect of illness and aging on cognitive function.
Large numbers of patients who survive critical illness are left with significant new cognitive impairments that are often severe and remain years after hospital discharge. In the previous issue of Critical Care, Guerra and colleagues assessed risk factors for the development of dementia after an intensive care unit (ICU) admission in a sample of older beneficiaries of Medicare. Older age was strongly associated with a diagnosis of dementia. ⋯ This study has several limitations - including use of ICD-9-CM codes that identified primarily neurodegenerative types of dementia, the lack of a control group, and a high mortality rate during the first 6 months after hospital discharge - which the authors acknowledge. An important additional limitation of the study by Guerra and colleagues and all previous post-ICU cognitive outcome studies is the inability to determine what role, if any, cognitive impairments that existed before the critical illness contribute to the diagnosis of new post-ICU dementia and whether such cognitive impairments are stable over time or are progressive like those observed in neurodegenerative diseases. Research is needed to answer questions regarding mechanisms of injury, medical and personal risk factors, and importantly the effect of interventions administered either during or after ICU treatment that may prevent or ameliorate such impairments.