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1、Respiratory Failure,1.Abstracts,Respiratory failure,whether acute or chronic,is a frequently faced problem and a major cause of death in our country.For example,mortality from COPD,which ends in death from respiratory failure,continues to increase.More than 70%of the deaths in patients with pneumoni
2、a are attributed to respiratory failure.,2.Definition,Respiratory failure is functional acute or chronic disorder caused by any condition that affects the lungs ability to maintain arterial oxygenation or carbon dioxide(CO2)elimination.It is defined as a condition in which this gas exchange deterior
3、ates below the usual level,so that arterial oxygen tension decreases,with or without an abnormal rise in arterial carbon dioxide tension.,3.Classifications,Generally both acute and chronic respiratory failure may be divided into two main categories:,Type respiratory failure,Type respiratory failure
4、is also called hypoxic respiratory failure,which means that severely reduces arterial oxygen tension(PaO260mmHg),CO2 retention is not exist.This type of respiratory failure is caused by a failure of gas exchange.,Type respiratory failure,Type respiratory failure is also meant that hypercapnic-hypoxi
5、c respiratory failure.Arterial blood gas values shows that arterial carbon dioxide tension is more than 50 mmHg and arterial oxygen tension is less than 60 mmHgType respiratory is mainly caused by hypoventilation.,Pathogenesis,Mainly discuss chronic respiratory failurewe have known that the lungs ab
6、ility is gas exchange.The gas exchange involves not only oxygenation but also carbon dioxide elimination.,Pathogenesis,Respiratory failure is mainly associated with pulmonary gas exchange and pulmonary ventilation.,1.pulmonary gas exchange is mainly determined by ventilation-perfusion(V/Q)ratios and
7、 diffuse ability,V/Q mismatch:An effective lung gas exchange needs not only sufficient lung ventilation and lung blood volumes but also an adequate V/Q ratios.Usually,the volume of ventilation is 4 liters/min.The volume of lung blood is 5 liters/min.So the ratios is 0.8,Any of the factors influenced
8、 the ratios may mainly cause hypoxemia respiratory failure.For example,V/Q0.8,including emphysema,pulmonary embolism.V/Q0.8,including atelectasis,severe COPD.,Diffuse ability Diffusion abnormality mainly influence oxygen exchange.,2.Pulmonary hypoventilation,It may cause hypercapnic-hypoxic respirat
9、ory failure.Pulmonary hypoventilation includes restrictive hypoventilation and obstructive hypoventilation.Some diseases influenced central nervous system,peripheral nervous system,chest wall respiratory muscles and pulmonary compliance may all cause restrictive hypoventilation.,Some common conditio
10、ns that may cause ventilatory failure with hypercapnea,These conditions include brain stem lesion,altered neuromuscular transmission(guillain-barre syndrome),muscle weakness(malnutrition,shock,hypoxemia,hypokalemia),increased airway resistance(upper airway obstruction,increased bronchial secretions
11、and edema),decreased lung compliance(infection,atelectasis,interstitial fibrosis,acute lung injury),decreased chest wall compliance(chest wall trauma,pleural effusion,pneumothorax).,COPD and asthma are the most common disease associated to obstructive hypoventilation.In our clinical work,multifactor
12、s involve in the course of respiratory failure.For example,a COPD patient with severe pulmonary infection,his pulmonary gas exchange ability and pulmonary ventilation are all abnormal.,Pathophysiology,Hypoxia and hypercapnic may influence functions of many important organs and systems,including resp
13、iratory system,cardiovascular system,central nerve system,blood system and digestive system and renal function.,Clinical manifestations,Clinical signs include not only symptoms associated with primary diseases but also those caused by hypoxic and hypercapnic-hypoxic respiratory failure.Hypoxemia and
14、 hypercapnia mainly influence the function of important organs,including respiratory system,central nervous system,cardiovascular system,digestive system,renal functions.,The unbalance of acid-alkalose metabolic and dielectric abnormality are usually exist in the course of respiratory failure.Table
15、1.Clinical manifestations of hypoxia and hypercapnia.,Clinical manifestations of hypoxia and hypercapnia HYPOXEMIA HYPERCAPNIA Tachycardia Somnolence Tachypnea Lethargy Anxiety Restlessness Altered mental status Slurred speech Confusion Headache Cyanosis Asterixis Hypertension Papilledema Hypotensio
16、n Coma Bradycardia Seizures Lactic acidosist,Diagnosis,According to history,clinical manifestations,physical examinations and blood gas analysis,we can diagnose respiratory failure.Especially arterial blood gas analysis may reveal hypoxemia and hypercapnia.,Diagnosis,The diagnosis standard include:T
17、ype respiratory failure:PaO2 50mmHg,PaO2 60mmHg.In the condition of oxygen therapy,PaO2/Fi O2300mmHg indicates respiratory failure.,Treatment,The principle of treatment includes primary disease treatment,airway maintenance,correction of hypoxemia and hypercapnia and management of symptoms caused by
18、hypoxemia and hypercapnia.,(1)Airway maintenance and enhance the volume of ventilation,Assurance of an adequate airway is key in the patient with respiratory failure.For patients with chronic respiratory insufficiency,the need for intubation depends on critical arterial blood gas values and the pati
19、ents early acute course.When progressive hypoxemia or hypercapnia is observed,intubation and mechanical ventilation are used.,To most of the chronic respiratory failure,correctly use of bronchodilators is very important.Table 2.Bronchodilators Route DoseAlbuterol MDI and spacer 400-600g q1-4h Aeroso
20、l solution 2.5-7.5mg q1-4hIpratropium MDI and spacer 80-120g q4-6h Theophylline,Mechanical ventilation The aim of mechanical ventilation is to improve hypoxemia and to prevent hypercapnia.When do you select mechanical ventilation?This is a question we always meet in our clinical work.1.progressive e
21、levation in PaCO270-80mmHg2.severe hypoxemia,after oxygen therapy,PaO235 per minute or severe breathlessness4.severe metabolic acidosis or pulmonary encephalopathy,(2)Antiinfectious therapy,Repeated bronchial and pulmonary infection is a major cause of chronic respiratory failure.About 90%of COPD pa
22、tients with respiratory failure is caused by acute bronchial or pulmonary infection.Infection may also increase bronchial secretion and CO2 production.So antiinfectious therapy is an important method to treat respiratory failure.,Select effective antibiotics According to sputum culture,we can select
23、 sensitive antibioticsUsing combined antibiotics Because of multibacteria infection,it needs several kind of antibiotics.For example,we may combine second or third generation cephalosporin to aminoglycoside or fluoroguinolone.,(3)Oxygen therapy,The goal of oxygen therapy is to improve PaO2.It makes
24、PaO260%.In general,the lowest FiO2 achieving adequate oxygenation.sometimes,arterial oxygen saturation90%should be used.,The methods of oxygen therapy:nasal prongs 1-3L/min to chronic respiratory failure venti mask 1-3L/minFor type 1 respiratory failure,we can elevate the percentage of oxygen to mai
25、ntain the PaO2.We can use higher inspirated fration of oxygen in type 1 respiratory failure oxygen therapy.But in type 2 respiratory failure we must select lower inspirated fration of oxygen.,(4)Acid-base and electrolytes disturbance,There are many factors lead to acid-base and electrolytes disturba
26、nce.These factors include severe pulmonary infection,hypoxemia or(and)hypercapnia.So airway maintenance,antibiotic therapy and use of bronchodilators are beneficial to treat it.,(5)Use of respiratory stimulant drugs,(6)Corticosteroids,Methyprednisone is usually used to reduce the airway inflammation
27、,and to improve FEV!.The treatment is recommended in all patients but it is not used for a longer time.,(7)Gastrointestinal bleeding treatment,Because of hypoxemia,hypercapnia and by using corticosteroids,gastrointestinal bleeding always be happened.The treatment mathod include correct hypoxemia and
28、 hypercapnia,use of H2-blocker and some block bleeding drugs.,(8)Nutritional support therapy,Acute Respiratory Distress Syndrome,ARDS,1.Definition,ARDS,which is a from of acute lung injury often seen in previously healthy patients,is characterized by rapid respiratory rates and a sensation of profou
29、nd shortness of breath,and accompanied by severe arterial hypoxemia.,2.Pathogenesis,ARDS can result from many disorders,including systemic or pulmonary infection,(viral,bacterial,fungal,ects.),aspiration,inhalation of toxins,metabolic disorders and severe sepsis or septic shock.The initial insult ca
30、use release of cytokines,mediators from cell membranes and activation of a number of cascades with injury to the pulmonary endothelium.,ARDS is invariably associated with increased liquid in the lungs.It is a form of pulmonary edema,distincts from cardiogenic pulmonary edema.Since hydrostatic pressu
31、re are not elevated.,3.Clinical manifestations,The early manifestations are an increased respiratory rates.Usually respiratory rates are more then 28 per minute.Some times the patient may be free of respiratory signs.Cough and sputum production.Because of severe hypoxemia,cyanosis is a common physic
32、al signs in ARDS patients.,X-ray shows a progressive,usually symmetrical,fluffy alveolar infiltrate that progresses to involve all potions of the lung.X-ray features of ARDS may be divided into three stages:First stage-sometimes normal,sometimes small patches may be existSecond stage-diffused small
33、or large patches,usually in lower lung fieldThird stage-pulmonary infiltrate involved all potions of the lung,called white lungArterial blood gas analysis shows PaO2/FiO2300mmHg and PaO260mmHg.(ALI),PaO2/FiO2200mmHg(ARDS),4.Diagnosis,There is a disorder which may lead to ARDS.For example,severe infe
34、ction ects.According to clinical manifestation,X-ray,arterial blood gas analysis,we can make a diagnosis.,The main diagnosis standard includes:,A factor which may leads to ARDSThe onset is acute.Tachypnea is exist.HypoxiaChest X-ray shows pulmonary infiltrate involved two lungs.PCWP=18mmHg or except
35、 cardiogenic pulmonary edema.,5.Treatment,Treatment of initial disorders which lead to ARDSImprove hypoxemia Severe arterial hypoxemia is a characteristic clinical sign of ARDS.In general,the lowest inspired fration of oxygen(FiO2)should be used to give the desired result.There are multiple means fo
36、r delivering O2,including soft nasal prongs,simple face masks.But in the condition of ARDS,these methods are not effective.Mechanical ventilatory support should be used early to improve hypoxemia.,Use of PEEPPEEP means positive end expiratory pressure.,Use of PEEP,The physiologic effects of PEEP inc
37、lude:1.redistribution of capillary blood flow,resulting in improved V/Q matching;2.The recruitment of previously collapsed alveoli and prevention of their collapse during exhalation.,Another treatments are similar to those chronic respiratory failure,including antiinfectious therapy,administration o
38、f corticosteroid,acid-base and electrolytes disturbance.,Mechanical ventilatory support,(1)Artifical airwaysEndotracheal intubation is usually adopted during mechanical ventilation.Intubation should be by the orotracheal or nasotracheal route is highly controversial.,Orotracheal tubes are larger and
39、 easier to place in an emergency but are harder to stabilizer and are more uncomfortable.Nasotrached tubes are better tolerated and oral hygiene,but have greater airway resistance and more difficult to suctionwhen tracheotomy must be used,the period of mechanical ventilatory is more than 4 to 6 week
40、s.Ventilatory support may be achieved by nasal mask.Nasal mask include an awake,cooperative patient.,(2)The common modes of mechanical ventilatoryAssisted ventilation,AVControlled ventilation,CVAssist-control ventilation,A-CVIntermittent mandatory ventilation,IMVSynchronized intermittent mandatory ventilation,SIMVPressure support ventilation,PSV or Inspiratory pressure support,IPSMandatory minute ventilation,MMV Continuous positive airway pressure,CPAP/positive end-expiratory pressure,PEEPBiphasic positive airway pressure,BiPAP,
