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1、UTHSCSA Pediatric Resident Curriculum for the PICUUTHSCSA Pediatric Resident Curriculum for the PICURESPIRATORY FAILURE & ARDSRESPIRATORY FAILUREInability of the pulmonary system to meet the metabolic Inability of the pulmonary system to meet the metabolic demands of the body through adequate gas ex
2、change.demands of the body through adequate gas exchange.Two types of respiratory failure:Two types of respiratory failure: HypoxemicHypoxemic HypercarbicHypercarbicEach can be further divided into acute and chronic.Each can be further divided into acute and chronic.Both types of respiratory failure
3、 can be present in the same Both types of respiratory failure can be present in the same patient.patient.CENTRAL ETIOLOGIES Trauma: head injury, asphyxiation, hemorrhageTrauma: head injury, asphyxiation, hemorrhage Infection: meningitis, encephalitisInfection: meningitis, encephalitis TumorsTumors D
4、rugs: narcotics, sedativesDrugs: narcotics, sedatives Neonatal apneaNeonatal apnea Severe hypoxemia or hypercarbiaSevere hypoxemia or hypercarbia Increased ICP from any of the above causesIncreased ICP from any of the above causesOBSTRUCTIVE ETIOLOGIESUpper Airway Anatomic: choanal atresia, Anatomic
5、: choanal atresia, tracheomalacia, tonsillar tracheomalacia, tonsillar hypertrophy, laryngeal web, hypertrophy, laryngeal web, vascular rings, vocal cord vascular rings, vocal cord paralysis, macroglossiaparalysis, macroglossia Aspiration: mucus, foreign Aspiration: mucus, foreign body, vomitusbody,
6、 vomitus Infection: epiglottitis, Infection: epiglottitis, abscesses, laryngotracheitisabscesses, laryngotracheitis Tumors: hemangioma, cystic Tumors: hemangioma, cystic hygroma, papilloma, hygroma, papilloma, LaryngpospasmLaryngpospasmLower Airway Anatomic: bronchomalacia, Anatomic: bronchomalacia,
7、 lobar emphysemalobar emphysema Aspiration: FB, mucus, Aspiration: FB, mucus, meconium, vomitusmeconium, vomitus Infection: pneumonia, Infection: pneumonia, pertussis, bronchiolitis, CFpertussis, bronchiolitis, CF Tumors: teratoma, Tumors: teratoma, bronchogenic cystbronchogenic cyst BronchospasmBro
8、nchospasmRESTRICTIVE ETIOLOGIESLung Parenchyma Anatomic: agenesis, cyst, Anatomic: agenesis, cyst, pulmonary sequestrationpulmonary sequestration AtelectasisAtelectasis Hyaline membrane diseaseHyaline membrane disease ARDSARDS Infection: pneumonia, Infection: pneumonia, bronchiectasis, pleural bronc
9、hiectasis, pleural effusion, effusion, Pneumocystis Pneumocystis cariniicarinii Air leak: pneumothoraxAir leak: pneumothorax Misc: hemorrhage, edema, Misc: hemorrhage, edema, pneumonitis, fibrosispneumonitis, fibrosisChest Wall Muscular: diaphragmatic Muscular: diaphragmatic hernia, myasthenia gravi
10、s, hernia, myasthenia gravis, muscular dystrophy, muscular dystrophy, botulismbotulism Skeletal: hemivertebrae, Skeletal: hemivertebrae, absent ribs, fused ribs, absent ribs, fused ribs, scoliosisscoliosis Misc: distended abdomen, Misc: distended abdomen, flail chest, obesityflail chest, obesityHYPO
11、XEMIAV/Q mismatch Most common reason. Blood perfuses non-ventilated Most common reason. Blood perfuses non-ventilated lung. Seen in atelectasis, pneumonia, bronchiectasislung. Seen in atelectasis, pneumonia, bronchiectasisGlobal hypoventilation: apnea apneaRight-to-left shunt Intracardiac lesions, e
12、.g., tetralogy of FallotIntracardiac lesions, e.g., tetralogy of FallotIncomplete diffusion Oxygen must diffuse across increased distance secondary Oxygen must diffuse across increased distance secondary to interstitial edema, fibrosis, or hyaline membrane.to interstitial edema, fibrosis, or hyaline
13、 membrane.Low inspired FiO2: high altitudehigh altitudeHYPERCARBIAPump Failure Reduced central drive: apnea, metabolic alkalosis, drugs, Reduced central drive: apnea, metabolic alkalosis, drugs, brainstem injury, hypoxiabrainstem injury, hypoxia Muscle fatigue: muscular dystrophyMuscle fatigue: musc
14、ular dystrophy Increased pulmonary workload: decreased compliance, Increased pulmonary workload: decreased compliance, increased obstructionincreased obstructionIncreased CO2 production: fever, seizure, malignant fever, seizure, malignant hyperthermiahyperthermiaIncreased dead space: V/Q mismatch (v
15、entilation of V/Q mismatch (ventilation of non-perfused lung)non-perfused lung)PHYSICAL EXAMTachypneaDyspneaRetractionsNasal flaringGruntingDiaphoresisTachycardiaHypertensionAltered mental status ConfusionConfusion AgitationAgitation RestlessnessRestlessness SomnolenceSomnolenceCyanosis (need 5mg/dl
16、 of unoxygenated blood)CXR FINDINGSCXR may be normal if problem is with upper airwayCan see hyperinflation, atelectasis, infiltrate, cardiomegalyAdditional studies may be needed, e.g., chest CT, barium swallow, echocardiogramBLOOD GASFor any age patient, breathing room air, respiratory failure is de
17、fined as arterial pCO2 50mm Hg or arterial pO2 60mm Hg.If the patient is hyperventilating, a normal pCO2 is disturbing.The above definition assumes the absence of an anatomic shunt.Chronic hypercarbic respiratory failure will often have a normal pH because of compensatory metabolic alkalosis.MANAGEM
18、ENTREMEMBER PALSAirwayBreathingCirculationAIRWAYRepositioningRepositioning Position of comfortPosition of comfort Jaw thrust/chin liftJaw thrust/chin liftOral airwayOral airway Unconscious patients onlyUnconscious patients onlyNasal trumpetNasal trumpetNasal or mask CPAPNasal or mask CPAPBag-mask ve
19、ntilationBag-mask ventilation Use during preparation for intubationUse during preparation for intubationTracheal intubationTracheal intubationBREATHINGDecrease respiratory workloadDecrease respiratory workload -agonists-agonists Decadron or steroidsDecadron or steroids AntibioticsAntibiotics CPAPCPA
20、PSupplemental OSupplemental O2 2 Nasal cannulaNasal cannula Closed face maskClosed face mask Non-rebreatherNon-rebreatherCounteract drug effectsCounteract drug effectsBag-mask ventilationBag-mask ventilationMechanical ventilationMechanical ventilationCIRCULATIONSuppress anaerobic metabolism and acid
21、osisCorrect anemia to improve oxygen deliveryEnsure adequate cardiac output Inotropes: oxygen, vasopressors Fluid bolusesARDSA patient must meet all of the following: Acute onset of respiratory symptomsAcute onset of respiratory symptoms CXR with bilateral infiltratesCXR with bilateral infiltrates N
22、o evidence of left heart failureNo evidence of left heart failure PaOPaO2 2/FiO/FiO2 2 200mm Hg (regardless of PEEP) 200mm Hg (regardless of PEEP)FFAmerican-European Consensus Conference on ARDS (Am J Resp American-European Consensus Conference on ARDS (Am J Resp Crit Care Med 149:818, 1994)Crit Car
23、e Med 149:818, 1994)The following are implied: Previously normal lungsPreviously normal lungs Decreased lung complianceDecreased lung compliance Increased shuntingIncreased shunting Hypoxemic respiratory failureHypoxemic respiratory failureETIOLOGYARDS represents about 3% of PICU admissions.Numerous
24、 precipitating events: TraumaTrauma PneumoniaPneumonia BurnsBurns SepsisSepsis DrowningDrowning ShockShockPATHOPHYSIOLOGYAcute InjuryLatent PeriodEarly Exudative PhaseCellular Proliferative PhaseFibrotic Proliferative PhaseRoyall and LevinJ Peds 112:169-180;335-347, 1988PATHOLOGY OF ARDSGreen arrows
25、 point to hyaline membraneGreen arrows point to hyaline membraneBlue arrows point to type II pneumocytes and alveolar macrophagesBlue arrows point to type II pneumocytes and alveolar macrophagesMANAGEMENTMeticulous supportive care is the mainstay of therapy Prevent secondary lung injury Ensure adequ
26、ate cardiac output Limit secondary infections Drugs Good nutritionVENTILATOR STRATEGIESThe hallmark of ARDS is heterogeneous lung.The hallmark of ARDS is heterogeneous lung.Limit Barotrauma Keep PIP 35 cm HKeep PIP 35 cm H2 2OO Use pressure-control Use pressure-control ventilationventilation Use TV
27、of 6-10cc/kgUse TV of 6-10cc/kg Keep rate 30 bpmKeep rate 7.20keep pH 7.20Limit O2 Toxicity Give enough PEEP to Give enough PEEP to lower FiOlower FiO2 2 to 60% to 90%.90%. PEEP 15 cm HPEEP E) ventilation.ratio (IE) ventilation.CARDIAC OUTPUTKeep cardiac output 4.5 L/min/m2.Keep O2 delivery 600 ml O
28、2/min/m2.Keep Hct 30%, higher if signs of heart failure.Use inotropes to augment cardiac output.Ensure adequate preload.LIMIT SECONDARY INFECTIONSWash your hands.Use the gut as soon as possible for nutrition and meds.Discontinue indwelling catheters as soon as possible.Have high index of suspicion.T
29、reat infections early, but tailor antibiotics to culture results.DRUGSDiuretics: a dry lung is a good lung.InotropesSteroids: 2mg/kg/day begun after a week into the course may be of benefit, otherwise dont use.Pulmonary vasodilators (nitric oxide, prostaglandins, nitroprusside): of little benefit. N
30、O may be of benefit in some patients.Surfactant replacement: probably no benefitNSAIDs: no clinical benefitNUTRITIONEnsure adequate calories as soon as possible:50-60kcal/kg/day in infants50-60kcal/kg/day in infants35-45kcal/kg/day in older children.35-45kcal/kg/day in older children.After day 4, in
31、crease calories by 25-50% above baseline.Begin enteral feeds as soon as is safe.“Pulmonary” formulas probably of little benefit.MORTALITY/MORBIDITYPublished mortality is 50% in children.Pulmonary failure accounts for only 15% of the deaths. Lung function usually returns to normal within 18 months after leaving the hospital.
