Defined as the impairment of the lungs ability to maintain adequate oxygen and carbon dioxide homeostasis Respiratory Failure Definition PaO 2 lt 60 mm Hg andor PaCO 2 gt 50 mm Hg ID: 776682
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Slide1
Respiratory Failure
Slide2Respiratory Failure
Defined as the impairment of the lung’s ability to maintain adequate oxygen and carbon dioxide homeostasis.
Slide3Respiratory Failure - Definition
PaO
2
< 60 mm Hg
and/or
PaCO
2
> 50 mm Hg
Slide4Respiratory Failure
Can be acute, sub acute, or chronic.
If chronic then compensation has developed to maintain pH.
Respiratory failure defined by pH < 7.25 in these patients.
Slide5Types of Respiratory Failure
Type 1 = Hypoxemic Respiratory Failure.
Type 2 = Hypercapnic/Hypoxemic respiratory failure.
Slide6Type 1 Respiratory Failure
Primarily a failure to maintain adequate oxygenation.
PaO
2
< 60 mm Hg.
Ventilation is not impaired.
PaCO
2
<= 40 mm Hg.
Slide7Type 1 Respiratory Failure Examples
Pneumonia – any etiology.
Acute (Adult) Respiratory Distress Syndrome (ARDS).
Reduced FiO
2
(High Altitude).
Slide8Examples – Patient A
A 24 y/o man with acute pneumonia.
ABG on room air
PaO
2
= 55 mm. Hg
PaCO
2
= 28 mm. Hg
pH = 7.49
Slide9Type 2 Respiratory Failure
Failure of the lungs to maintain ventilation.
PaCO
2
> 50 mm. Hg
Resulting hypercarbia may lead to hypoxemia alone.
Usually V/Q mismatch and/or shunt is also present.
Etiology more varied.
Slide10Example – Patient B
A 23 y/o woman presents in coma:
ABG on room air:
Pa02 = 62 mm Hg
PaCO2 = 86 mm Hg
pH = 7.04
Slide11Type 2 Respiratory Failure - Examples
Pneumonia – any etiology
Drug overdose
COPD
Upper airway obstruction
Slide12Type 2 Respiratory FailureEtiologic Locations
CNS
Peripheral nervous system
Chest wall disorders
Lung parenchyma
Extrapulmonic organs – heart etc.
Slide13Mechanisms of Hypoxemia
Hypoventilation
è
Check PaCO
2
V/Q mismatch
è
Resolves with 100% O
2
Shunt
è
Doesn't resolve with 100% O
2
Insufficient FiO
2
è
Check FiO
2
at mouth
Diffusion Block
è
Exceedingly rare
Slide14Symptoms of Respiratory Failure
Often nonspecific (and unrecognized)
Dyspnea
Headache
Chest pain
“Feeling of Impending Doom”
Slide15Signs of Respiratory Failure
Mental status changes.
Respiratory Distress.
Accessory muscle use.
Inability to speak.
Rate, depth and noise of breathing.
Slide16Treatment of Respiratory Failure
Immediate stabilization.
Determination of the inciting event.
Treatment of the precipitating event.
Treatment of co-existing lung disease.
Slide17Treatment of Respiratory Failure - Stabilization
Call for help.
Supplemental oxygen.
Tracheal intubation.
Mechanical ventilation.
Slide18Central Nervous System Causes of Respiratory Failure
Drugs
Hypothyroidism
Brainstem injury or tumor
Primary alveolar hypoventilation
Central sleep apnea
Slide19Extrapulmonary Respiratory Failure
Hypoxemic with normal A-a gradient
Hypercarbic acute or chronic
CNS
PNS
Respiratory muscles
Chest Wall
Pleura
Upper Airways
Slide20Pulmonary Causes of Respiratory Failure
Lower airway
Asthma, COPD
Parenchymal
Pulm. Edema, infections, interstitial lung dz
Pulmonary vasculature
PE, Primary pulmonary hypertension
Slide21Upper Airway Obstruction
Acute epiglottitisAcute laryngeal edemaAnaphylaxisTraumaForeign body aspirationRetropharyngeal hemorrhage
Bilateral vocal cord paralysis
Tracheal stenosis
Tracheomalasia
Tumors
Slide22Chest Wall and Pleural Disorders
Kyphoscoliosis
Obesity hypoventilation
Flail chest
Fibrothroax
Thoracoplasty
Ankylosing spondylitis
Slide23Respiratory Muscle Dysfunction
Muscular dystrophies
Myotonic dystrophies
Polymyositis
Periodic paralysis
Electrolyte disorders
Slide24Peripheral Nervous System Causes of Respiratory Failure
Spinal cordTetanusStrychnineALSGuillain Barre Synd.ShellfishBilateral phrenic nerve palsy
Diptheria
Pseudocholinesterase deficiency
Myasthenia Gravis
Eaton-Lambert
Botulism
Organophosphate poisoning
Slide25ARDS
Acute Respiratory Distress
Syndrome
History
Adult hyaline membrane diseaseDa nang lungPump lungShock lungTraumatic lungTransplant lungWet lungWhite lungPost transfusion lung
Adult respiratory distress syndrome:ARDS
(Ashbaugh 1967)
Acute respiratory distress syndrome:ARDS
(AECC 1994)
Slide27Definition(American-European Consensus Conferense: AECC 1994)
ARDSAcutePaO2/FiO2<200 mmHgBilateral interstitial or alveolar infiltratesPcwp <18 mmHg
ALI
Acute
<300 mmHg
Same
same
Slide28Etiology
Direct lung injuryAspiration of gastric contentsPulmonary contusionToxic gas inhalationNear drowningDiffuse pulmonary infectionFat embolism
Indirect lung injurySevere sepsisMajor traumaHypertransfusionAcute pancreatitisDrug overdoseReperfusion injuryPost cardiac bypass/lung transplants
Slide29Incidence
United States:
150,000 cases per year (75/100,000
population)
Recent studies:
Lower annual incidence of 3 to 5/100,000 population
Slide30Prognosis
its cause, the patient's age, and co- morbid factors
Low:
chronic disease, multiple organ dysfunction syndrome (MODS), and sepsis
Pathogenesis
systemic inflammatory response
complement system
coagulation cascade
cyclooxygenase
leukotriene pathways
cytokines
chemokines
nitric oxide (NO)
Slide32Pathology
diffuse alveolar damage (DAD)
Acute alveolar injury
Exudative phase
Pulmonary vascular lesions
Proliferative phase
(honeycomb lung)
Pathology Typical histologic findings with ARDS which includes alveolar inflammation, thickened septal from protein leak (pink), congestion and decreased alveolar volume
Slide34Infectious causesBacteria - Gm neg & pos , mycobacteriae, mycoplasma, rickettsia, chlamydiaViruses- CMV, RSV, hanta virus, adeno virus, influenza virusFungi- H.capsulatum, C.immitisparasites- pneumocytis carinii, toxoplasma gondii
Differential Diagnosis
Slide35Differential Diagnosis
Non infectious causes
Drugs & toxins
(paraquat, aspirin, heroin, narcotics, toxic gas, tricyclic anti depressants, acute radiation pneumonitis)
Idiopathic
(esinophilic pneumonia, Acute interstitial pneumonitis, sarcoidosis, rapidly involving idiopathic pulmonary fibrosis)
Immunologic
(acute lupus pneumonitis, Good Pastures syndrome, hypersensitivity pneumonitis)
Metabolic
(alveolar proteinosis)
Miscellaneous
(fat embolism, neuro/high altitude pulmonary oedema)
Neoplastic
(leukemic infiltration, lymphoma)
Slide36Differential Diagnosis
Slide37Physiology
Hypoxemia
Increased dead space
Low lung compliance
Low chest wall compliance
Measurement of respiratory compliance
Slide38Treatment of ARDS
General measures
Specific therapy
Mechanical ventilation
Ancillary ventilatory strategies
Slide39General measures
Diagnosis& Treatment of underlying condition
Hemodynamic management
Hemodynamic monitoring
Early treatment of sources of inflammation and sepsis
Treatment of infections
Nutrition
Avoidance of iatrogenic complications
Support of other organ system function
Slide40Support of other organ system function
Hemodynamics
Renal function
Skeletal muscle
GI tract
Slide41Specific therapy
Bronchodilator Anti inflammatory therapy corticosteroidsShort termLong term NSIDSProstaglandinsPGE1PGI2Immunotherapy Antiendotoxin Anticytokine antibodiesCytokine-receptor antagonistsCyclo oxygenase inhibitors
Antioxidant
Ketoconazole
Ketanserin
Almitrine
Pentoxiphyline
Slide42Mechanical ventilation
VALI
Traditional approach
V
T
=10-15 ml/kg, PEEP=10-20 CmH2O
Limiting the FIO
2
Normal ABG
This traditional philosophy has been challenged
Barotrauma
Diffuse nonhomogeneous lung injury
The ideal method of MV for these patients is still controversial
Slide43Mechanical ventilation
TPP≤30 CmH
2
O
Adequate lung expansion
Appropriate level of both EEAP and EIAP
Using semi-static compliance
Slide44Mechanical ventilation
Recruitment maneuvers
High and short term CPAP(40CmH
2
O, 30 min)
Pressure limited ventilation
The initial IFR is high and variable
The maximal AP is reached early in inspiration
Slide45Recruitment maneuvers Portable chest computed tomography of a patient withsevere acute respiratory distress syndrome (ARDS). On the left, thepatient is ventilated on 20 cm H2O positive end-expiratory pressure(PEEP). On the right, the patient is on 25 cm H2O PEEP after a recruit-ment maneuver consisting of PEEP 40 cm H2O, pressure control 20 cmH20, respiratory rate 10/min, inspiratory to expiratory (I:E) ratio 1:1for 2 minutes. (Courtesy of Dr. Benjamin Medoff, MassachusettsGeneral Hospital.)
Slide46Ancillary ventilatory strategies
ECMO
IVOX
Exogenous surfactant
HFV
Inhaled NO
Prone ventilation
Partial liquid ventilation
Slide47ECMO
Slide48Suggested algorithm for mechanical
ventilation in patients with ARDS and other
forms of severe respiratory failure
Secure the airway and deliver positive-pressure ventilation with
5-10 cm H
2
O PEEP
• Obtain hemodynamic stability and patient comfort
• Pursue diagnosis and therapy of the cause
Set FlO
2
to keep SpO
2
> 90% or PaO
2
> 60 mm Hg
With the ventilator in pressure-limited assist control mode, set
pressure control and PEEP:
A.
Empiric
way (fast):
• Set pressure control <20-25 cm H
2
O (vt = 500-600 ml)
and respiratory rate aiming for a PacO
2
and pH close to
normal or mild respiratory acidemia.
• Increase PEEP by 2.5 cm H
2
O steps every 20-30 min, as
long as SpO
2
and vt increase or stay the same. Consider
decreasing pressure control and increasing rate if the sum
of PEEP and pressure control settings is >35 cm H
2
O.
B.
Physiologic
way (slow):
• Perform a static P-V curve of the respiratory system, and
set PEEP and pressure control just above and below the
lower and upper inflection points, respectively.
• Reassess pressure control and PEEP settings daily.
Slide49•
If high ventilatory requirements persist (e.g., FiO
2
> 0.6, PEEP >
10 cm H
2
O), consider:
A. Increasing sedation, considering neuromuscular blockade.
B. Recruitment maneuver.
C. Permissive hypercapnia.
D. Increasing inspiratory time.
E. Prone ventilation.
F. Inhaled NO.
G. If beyond 7 days of ARDS and no evidence of infection,
consider corticosteroids.
•
If ventilatory requirements decrease and the patient is generally
stable, consider:
A. Decreasing FlO
2
by 0.05-0.1 steps every 2-4 h, keeping
SpO
2
> 90%.
B. Discontinuing neuromuscular blockade, decrease sedation.
C. Decreasing I: E ratio toward =1:3 (inspiratory time 1.0-1.5 s).
D. Decreasing respiratory rate to allow spontaneous
ventilation.
E. Setting ventilator mode to PSV.
Slide50