【正文】 ? respiratory muscle fatigue ? difficult to clear airway secretion → infection deteriorate ? atelectasis → the surface area of gas exchange ? ? Complete airway obstruction → apnea, death Clear airway secretion : ? mucolytics ? manual suction 42 A: Airway (氣道通暢嗎？ ) ? Open airway, blind sweep inside mouth ? Look, listen, and feel ? Assist if patient is not breathing adequately (watch for neck injury) ? Head tilt ? Jaw thrust ? Intubation – best protection ? Airway confirmation: CO2 + BBS ? CO2 may be absent if patient has no circulation 43 Maneuvers to Open the Airway ? Head tilt ? Jaw thrust (preferred in trauma) ? Triple airway maneuver: chin lift, head tilt, separation of teeth 44 Treatment Keep airway open保持氣道通暢 ? Bronchodilators for patients with bronchospasm: ?β2adrenoreceptor agonist, anticholinergic, glucocorticoid, theophylline ?Mode of administration : parenteral first and then inhale ?Mechanical ventilation+ medications delivery ?Airway humidify amp。 excitability ? ? Consciousness: dizziness, asterixis, somnolence, a, convulsion ? Peripheral nerves: sympathetic nerve, adrenal gland, distal nerves， catecholamine(CA)? 27 Influence of hypercapnia Cardiovascular system ? HR?, CO ?, BP? ? With stimulation of sympathetic nerve, the skin and abdominal vessels contract while coronary vessels dilate ? Severe hypoxia and hypercapnia → directly inhibit cardiovascular center → depressed cardiac function, dilated vessels → BP↓, arrhythmia ? Acute severe hypercapnia → ventricular fibrillation or cardiac arrest especially during intubation procedure ? PaCO2 enhance cardiac inhibition by vagus 28 Influence of hypercapnia Respiratory system ? Stimulate respiratory center → strengthen respiratory movement, Ventilation ? ? (PaCO2 ? kPa， Ventilation volume? 2 L/min) ? Slight contraction of small pulmonary arteries ? Directly relax the bronchial smooth muscle ? PAO2? ? PaCO2? → rightward shift of the oxyhaemoglobin dissociation curve (ODC) 29 pH? pH ? 30 Influence of hypercapnia urinary system ? Mild CO2 retention →dilation of renal blood vessels → renal blood flow? → urine ? ? PaCO2 8 kPa, pH ? ? →renal blood vessels spasm → renal blood flow ? ? HCO3 and Na+ reabsorption? → urine ? 31 Influence of hypoxemia amp。 CO? ? hypoxemia and blood viscosity ? → the risk of DIC? 25 Influence of hypoxemia Renal amp。min ? If jugular vein PaO2 20mmHg: unconsciousness, a ? PaO2 20mmHg: irreversible damage to nerve cells in several minutes (4~5min) ? Mild hypoxemia: impaired concentration, disorientation, hypomnesia ? Severe hypoxemia: dysphoria, unconsciousness, a 22 Influence of hypoxemia Cardiovascular system ? Myocardium oxygen consumption: 10 ml/100g/min ? Early stage of acute hypoxia–stimulation of sympathetic nerve→HR?、 BP?、 CO ? ? Chronic hypoxia → small pulmonary arteries contraction → pulmonary hypertension?— Cor pulmonale 23 ? PaO2↓ (60mmHg) →stimulate the chemoreceptors → stimulate respiratory center → strengthen respiratory movement, MV ?, respiratory distress ? PaO2↓(30mmHg)→inhibition of respiratory centerstimulation of respiratory center → respiratory depression ? Hyperventilation→CO2↓→inhibition of respiratory center ? Severe hypoxemia → slow shallow irregular respiration or CheyneStokes respiration Influence of hypoxemia Respiratory system 24 Influence of hypoxemia haematological system ? Chronic hypoxemia →stimulate hematopoiesis of bone marrow → EPO production ? RBC ? ? haemoglobin saturation amp。 Pathophysiology ? Hypoxemia ? Alveolar ventilation ↓ ? FiO2↓ ? Diffusion abnormality ? V/Q mismatch ? AV shunt ? Hypercapnia(CO2 retention) ? CO2 production↑ ? Alveolar ventilation ↓ 14 15 Mechanisms of hypoxemia ? FiO2↓ ? Altiplano or under a deep well ? PAO2 amp。 Critical Care Medicine The first Affiliated Hospital of SunYat Set University 2 Male, 32 Fever, cough with sputum for 3 days No finding on physical examination Diagnosis: pneumonia X－ ray: shadow in left lower lobe August 16, 2022 August 20, 2022 Acute shortness of bre