【正文】 strong as its weakest link” 55 Treatment Oxygen therapy Indications of oxygen therapy : ? Pump failure: improve ventilation ? Pneumonia, Pulmonary embolism, acute attack of asthma ? Severe pulmonary edema, ARDS ? Acute deterioration or worsening of COPD (pay attention to CO2 retention when giving oxygen therapy! ) 56 Treatment Oxygen therapy Inspired oxygen concentration: ? Inspired oxygen concentration should be the lowest value that results in an oxygen saturation of over 90% (PaCO2 about 60mmHg). ? High concentrations of inspired oxygen (35%) are safe in patients with type Ⅰ respiratory failure, as there is no risk of CO2 retention. ? While in patients with type Ⅱ respiratory failure, who are dependent on hypoxic drive for ventilation, oxygen therapy must be carefully controlled so that sufficient oxygen is supplied but without precipitating severe respiratory acidosis. 57 Oxygen delivery device: ① Nasal cannula/prongs: ? Advantage: allow patients to eat, drink, expectorate and speak ? Disadvantage: FiO2 delivered is not stable and affected by breathing。 high flow rates irritate nasopharyngeal mucosa ? Guide: Delivers 4% Oxygen per liter flow。 FiO2 (%)=21+4 oxygen flow rate (L/min) ? Flow rates should be limited to less than 7L/min. ② Mask: ? Simple oxygen mask, nonrebreathing mask with reservoir bag, Venturi mask. ? Advantage: FiO2 delivered is paratively stable and is adjustable。 less irritative to nasopharyngeal mucosa ? Disadvantage: inconvenient for patients to expectorate, eat and drink Treatment Oxygen therapy 58 Nasal cannula/prongs 鼻導管吸氧 ? 鼻導管給氧的上限量為 6L/min，大于這一流量時，由于管道和鼻咽內產生渦流，吸氧濃度不再增加。 59 Simple oxygen mask 常規(guī)面罩 ? 常規(guī)面罩可提供較穩(wěn)定的氧濃度，其輸送的氧濃度大約為70% 80% ? 但是這兩種方法都不能精確地監(jiān)測 FiO2。因為隨呼吸頻率、每分鐘通氣量、室內空氣的流動、輸氧裝置的放置等因素的不同而改變。故影響糾正低氧血癥并防止高碳酸血癥的發(fā)生的治療觀察。 60 Venturi mask Venturi面罩 ? Venturi面罩可較精確地調整 FiO2，但面罩必須佩戴正確才能使預期的氧量得到輸送 61 Treatment Oxygen therapy Side effects ? Inhibition of respiratory center in patients with type Ⅱ respiratory failure, who are dependent on hypoxic drive for ventilation ? CO2 retention ↑ ? Absorption atelectasis/denitrogenisation 吸收性肺不張 ): nitrogen is replaced by more absorptive oxygen ? Oxygen poisoning : High concentrations of inspired oxygen ?injury of pulmonary capillary epithelium 62 Treatment Ensure adequate ventilation, correct CO2 retention Respiratory stimulant: mainly used in CNS depression ? Principles for respiratory stimulant (呼吸興奮劑 ) : ? Maintain potency of airway to avoid respiratory muscles fatigue and deteriorate CO2 retention ? Be cautious when used in patients with frequent convulsion caused by cerebral anoxia, cerebral edema ? Suitable for patients with normal respiratory muscle strength ? Not suitable for patients only with oxygenation failure ? Avoid sudden withdrawal ? Drug: coramine, lobeline, doxapram 63 Treatment Noninvasive positive pressure ventilation, NIPPV ? Indications ? Conscious and cooperative ? Stable circulation ? Be able to protect airway ? No facial trauma, injury and deformity ? Be endurable to mask 64 Different kind of masks 各款口鼻面罩 65 Treatment Mechanical ventilation ? Goals of Mechanical Ventilation: ? improve alveolar ventilation, decrease PaCO2。 ? improve pulmonary gas exchange。 ? Decrease work of breathing, reverse respiratory muscle fatigue. ? Indications for mechanical ventilation : ? apnea。 ? upper airway obstruction。 impaired airway protection。 ? inadequate handling of secretions。 ? acute hypercapnia that is not quickly reversed by appropriate specific therapy。 ? severe hypoxemia。 ? progressive patient fatigue despite appropriate treatment. ? Adjust modes and settings for mechanical ventilation according to blood gas analysis and clinical judgment 66 Treatment Management of electrolyte and acidbase disturbance ? Respiratory acidosis ? improve alveolar ventilation ? Respiratory acidosis + metabolic acidosis ? Etiology management of acidosis ? improve alveolar ventilation ? appropriate alkali supplement ? Respiratory acidosis + metabolic alkalosis ? Avoid Iatrogenic factors 67