Dr. Alfred Chan Specialist in respiratory medicine

81 Pages·2013·2.87 MB·English

Dr. Alfred Chan
Specialist in respiratory medicine
Associate Consultant, ICU of TMH
20th August 2013
In the beginning
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1816, RTH Laennec invented the first stethoscope
In 1821
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Combining necropsy
and physical finding,
diseases of lung were
described
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“Idiopathic anasarca of
lung—pulmonary edema
without heart failure”
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Universally fatal
Ashbaugh 1967
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“Acute Respiratory Distress Syndrome”
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“Rapid onset of tachypnea and hypoxemia, with loss
of lung compliance, diffuse CXR alveolar infiltrates”
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“Closely resembles respiratory distress seen in infants”
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Pathology is related to diminished surfactant
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PEEP may help
IDEAL DIFFERENCE BETWEEN CARDIOGENIC & NONCARDIOGENIC PULMONARY EDEMA
CARDIOGENIC
PULMONARY EDEMA NONCARDIOGENIC PULMONARY EDEMA
History
Acute cardiac event Usually Uncommon (but possible)
Physical Examination
Cardiac output state Low-flow state (cool periphery) High-flow state (warm periphery, bounding pulses)
S3 gallop Present Absent
Jugular venous distention Present Absent
Crackles Wet Dry
Underlying non-cardiac disease (e.g., peritonitis) Usually absent Present
Laboratory Tests
Electrocardiogram Ischemia/infarction Usually normal
Chest x-ray Perihilar distribution Peripheral distribution
Cardiac enzymes May be elevated Usually normal
Pulmonary capillary pressure >18 mm Hg <18 mm Hg
Intrapulmonary shunting Small Large
Edema fluid/serum protein <0.5 >0.7
Sibbald WJ et al. Chest 84:460, 1983.
American European Consensus
Conference (AECC) 1994
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Acute onset
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Hypoxemia
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Bilateral infiltrates on CXR consistent with odema
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No evidence of left atrial hypertension
≤
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Problems unanswered by AECC
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Heterogeneous disease
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Widely possible etiology
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Lacking gold standard to validate
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pathology?
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diffuse alveolar damage?
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Routine use of pulmonary artery catheter?
Specific issues unsettled
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“Acute” not defined explicitly
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Subsequent trials often arbitrarily fixed at 72 hours
after pulmonary insults
Hypoxemia quantified
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Not standardized he conditions when the PaO2/ FiO2
should be calculated
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PaO2/ FiO2 ratio varied with ventilator setting and
FiO2 being used, and may improve with PEEP
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Other causes possible e.g. low cardiac output
Analyzed published ARDS cases
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With relatively low
shunt
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higher PaO2/ FiO2 ratio
at the extreme of FiO2
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With more shunt
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Higher PaO2/ FiO2 at
lower FiO2
Gowda et al. Crit Care Med 1997