高流量氧疗的生理效应-俞康龙

,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,高流量氧疗的生理效应,Physiological Effect of High Flow Nasal,Cannula,(HFNC)Therapy,上海交通大学第一人民医院急诊与危重病科 俞康龙,COI statement,The author has no conflict ofinterest to declare.,High Flow,an interesting oxygenation method,-novel,-magic,-gentle and moderate,So cool,HFNC shines during RSI,Put the big,cannulae,into your patients nose and,letr,rip.Add a face mask or NIV or whatever your,preoxygenation,pleasure,then push your meds and laugh to yourself as the saturation rises during apnea.Whistle sweetly as the intern illuminates every inch of the soft palate with great determination.Hell,go see another patient and tell him to call you when hes given up.,You remember,though,the days of the giants.When being regarded as a skilled,laryngoscopist,meant something.When the word,airway,made internists scatter like mice.When it wasnt so easy to save a life.,http:/ has promoted oxygen therapy,1891,-,E.,Bonnaire,described,O,2,inhalations in the newborn,1963,Patrick Bouvier Kennedy dies of respiratory distress syndrome(RDS),34 weeks gestation,birthweight 2100 gms.,1963,Maria Delivoria-Papadopoulos,First successful ventilation of a preterm infant with hyaline membrane disease(,Assisted ventilation in terminal hyaline membrane disease.Arch.Dis.Child.,39:481-484,1964,1971,Gregory,Use of continuous positive airway pressure(CPAP)for respiratory distress syndrome(RDS),Oxygen therapy&oxygen delivery devices,HFNC,The role of HFNC in respiratory therapy,What is HFNC?,a“new”methods of,oxygen therapy,air/oxygen applied to patient at,high flow,rates,air/oxygen run through a,nasal,cannula,air/oxygen is well conditioned by sufficient,warmth,and,humidification,-so called,heated,humidified high-flow nasal,cannula,(HHHFNC)therapy,2-70 L/min,Mechanisms of action for HFNC,Washout of nasopharyngeal dead space,Reduction of,inspiratory,resistance(work of breathing)by providing adequate flow,Improved mechanics by supplying adequately warmed and humidified gas,Reduction in the metabolic cost of gas conditioning,Provision of distending pressure,Washout of nasopharyngeal dead space,The,high volumetric flows,pouring from a small bore,cannula,cause,high velocity,flows which create,turbulent,energy to,flush the upper airway,of expiratory gas.,Dead space washout improves ventilation,anatomical dead space,in adults 30%of tidal volume,in neonates 50%of tidal volume,change the gas composition in nasopharyngeal space,reduce,rebreathing,expired CO,2,increase the fraction of inspired O,2,increase alveolar ventilation efficiency,MV=(V,T,V,D,)x RR PaCO,2,=PeCO,2,/(1 V,D,/V,T,),PaO,2,=(P,B,O,2,P,H2O,)x FiO,2,PaCO,2,/R P,A-a,O,2,CO,2,washout during HFNC with different flow rates,NHF rates 0 L/min 30 L/min 60 L/min,Midway,through,expiration,(t=1.2 s),End of,expiration,(t=2.2 s),Van Hove SC,et al.Ann Biomed Eng(2016)44:3007-3019.,High flow and high velocity increase alveolar ventilation efficiency,likely minimize the,inspiratory,resistance associated with the,nasopharynx,by providing nasopharyngeal gas flows that match or exceed a patients peak,inspiratory,flow,Coanda,effect,occuring,in the nasopharyngeal region during expiration potentially assist expiratory efforts,bring about a decrease in work of breathing,and respiratory rate,create more turbulent energy for more effective washout,flush the expiratory gas from the upper airway quickly during the exhalation phase of breathing,which is critical in patients with rapid breathing,Ventilatory,Responses to HFNC,Mndel,T et al.,Mechanisms of nasal high,ow,on ventilation during wakefulness and,sleep,J,Appl,Physiol,2013.114:10581065,Mucociliary,transport system,Health ciliated epithelium Damaged ciliated epithelium,https:/ functions dependent on inspired humidity,Williams,RB.Respire Care,Clin,N Am 1998 Jun;4(2):215-28,Temperature and humidity,Low temperature does mean insufficient humidity.,Enough water supplement does not always mean sufficient humidity.,An adult may require approximately 150 calories/min(10kcal/h)for conditioning,inspiratory,air from ambient to BTS.,Kacmarek,RM,et al.Egans Fundamentals of Respiratory Care.St.Louis,MO:Elsevier/Mosby,2013.,Inspired gas needs conditioning,Respiration with ambient gas,not warmed or humidified,induced,bronchoconstriction,response,and resulted in a significant decrease in both pulmonary compliance.,The nasal air passages expend,quite a few,energy to warm,and humidity,inspiratory,air from ambient to,BTS.,Studies from the 1990s demonstrated the negative effects of using non-warmed,non-humidified gas to support respiration.,Flow and Pressure fundamentals,HFNC is intended to be an open system,with flow delivered to a patient via nasal,cannula,where the,cannula,prongs do not occlude the,nares,and where the patients mouth is not held closed.In this open system,the pressure in each compartment is a function of the,resistor(s,),that lie in series downstream from that compartment.In this,regard,circuit pressures will always be substantially greater than