低氧与呼吸衰竭（级）.ppt

* * Other mechanisms may contribute, including increased VA/Q mismatching by the removal of hypoxic vasoconstriction. As these patients are on the steep part of the ODC, significant improvements in O2 content can usually be achieved by small increases in FiO2. The resulting small improvement in PaO2 does not cause respiratory depression. * * * * * * * * * The Berlin Definition may assist future trials of novel treatments by improving diagnostic reliability and allowing more precise stratification of patients according to severity. * * * * * * * * * * * * * * * * * Patients with advanced COPD usually experience periods of clinical stability punctuated by recurrent exacerbations. These exacerbations take the form of acute-on-chronic respiratory failure, characterized by worsening dyspnea and increasing production of purulent sputum. * COPD is a progressive illness and will ultimately result in severe disability and death. Patients with advanced disease may present with respiratory failure in the absence of an identifiable precipitant. Around 25% of patients with stable COPD show evidence of tracheobronchial colonisation. During exacerbations, bacteria are present in 50% of patients and viral infections in 10-20%. * * * * * * Many diseases cause dysfunction of several of the essential components of the respiratory system, and ultimately this leads to abnormalities of gas exchange. Identifying the cause of respiratory failure is essential to develop an effective management plan quickly. * * It has been said the body is like a chain composed of links that represent the brain, the peripheral nervous system, the upper airway, the lower airway, the respiratory muscles, the cardiovascular system, and the lungs. Respiratory failure may result when any of the links become sufficiently dysfunctional or weak. Like a chain the body is only as strong as its weakest link, and respiratory failure may result when a component of the chain becomes sufficiently compromised. * * *