美国重症医学（FCCM）的基础教程 急性呼吸衰竭的诊断和管理

nullDiagnosis and Management of Acute Respiratory FailureDiagnosis and Management of Acute Respiratory FailureARF * ®ObjectivesObjectivesDefine and classify acute respiratory failure Describe pathophysiology of acute respiratory failure Discuss clinical manifestations Review oxygen supplementation strategies Discuss noninvasive positive-pressure ventilation ARF * ®Acute Respiratory FailureAcute Respiratory FailureHypoxemic Room air PaO2  50 torr (6.7 kPa) Hypercapnic PaCO2  50 torr (6.7 kPa) Acute vs chronic –Pathophysiology of HypoxemiaPathophysiology of HypoxemiaVentilation/perfusion mismatch Shunt effect Decreased diffusion of O2 Alveolar hypoventilation High altitude Pathophysiology of HypercapniaPathophysiology of HypercapniaDecreased tidal volume and/or respiratory rate Inability to sense elevated PaCO2 Inability to signal effector mechanisms Inability to effect a response from respiratory musclesIncreased Dead SpaceIncreased Dead SpaceHypovolemia Low cardiac output Pulmonary embolus High airway pressures Short-term compensation by increasing tidal volume and/or respiratory rateManifestations of Respiratory DistressManifestations of Respiratory DistressAltered mental status Increased work of breathing Tachypnea Accessory muscle use, retractions, paradoxical breathing pattern Catecholamine release Tachycardia, diaphoresis, hypertension Abnormal arterial blood gas values ARF * ®Acute Respiratory Failure ManagementAcute Respiratory Failure ManagementOxygen supplementation Increase FIO2 Match flow between delivery device and inspiratory demand High- vs. low-oxygen systems High- vs. low-flow systemsARF * ®Nasal CannulaNasal Cannula100% oxygen delivered Low flow <0.5–5.0 L/min Low oxygen FIO2 <0.4–0.5Air-Entrainment Face Mask Air-Entrainment Face Mask 100% O2 + entrainment device High flow Variable oxygen FIO2 0.24–0.5Aerosol Face Mask Aerosol Face Mask 100% O2 + large-bore tubing Nebulizer/O2 blender Flow matching If mist disappears in inspiration, air is entrained Moderate-flow, variable FIO2 deviceReservoir Face Mask Reservoir Face Mask Reservoir bag filled with 100% O2 High oxygen High flow Resuscitation Bag-Mask-Valve DeviceResuscitation Bag-Mask-Valve Device100% O2 High flow (> 15 L/min) Emergency equipment Little to no air entrainment with firm fit Noninvasive Positive-Pressure Ventilation (NPPV)Noninvasive Positive-Pressure Ventilation (NPPV)Ventilatory assistance with controlled FIO2 Unilevel or bilevel pressure support Nasal or face mask Volume or pressure-cycled ventilator Most effective with alert, oriented and cooperative patient Successful in hypoxemic and hypercapnic failure ARF * ®Relative Contraindications for NPPVRelative Contraindications for NPPVDecreased level of consciousness Poor airway protective reflexes Copious secretions Cardiovascular instability Progressive pulmonary decompensation Upper gastrointestinal hemorrhageARF * ®Initiation of NPPVInitiation of NPPVSet FIO2 at 1.00 Hypoxemic failure Inspiratory pressure (IPAP) 10 cm H2O Expiratory pressure (EPAP) 5 cm H2O Titrate EPAP in 2 cm H2O increments Ventilatory failure IPAP 10 and EPAP 2 cm H2O Titrate IPAP in 2 cm H2O incrementsInitiation of NPPVInitiation of NPPVMake changes every 15-30 minutes Monitor vital signs, appearance, pulse oximetry and blood gases Head of bed at 45 angle Consider gastric decompression Intubation if patient deteriorates Pharmacologic Adjuncts Pharmacologic AdjunctsBronchodilators 2-agonists Anticholinergics (ipratropium) Corticosteroids Theophylline Antibiotics Key PointsKey Points