Dyspnea, Hypoxemia & Respiratory Failure 2012 Pulmonary Medicine Introductory Course 4 th year...
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Dyspnea, Hypoxemia & Respiratory Failure 2012 Pulmonary Medicine Introductory Course 4 th year Workshop Dr. Samir Nusair, MD Dr. Nissim Arish, MD
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Transcript of Dyspnea, Hypoxemia & Respiratory Failure 2012 Pulmonary Medicine Introductory Course 4 th year...
Dyspnea, Hypoxemia & Respiratory Failure
2012
Pulmonary Medicine Introductory Course4th year Workshop
Dr. Samir Nusair, MDDr. Nissim Arish, MD
Definition:Dyspnea is an abnormally uncomfortable
awareness of breathingATS definition:
Subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity.
The experience derives from interactions among multiple physiological, psychological, social, and environmental factors and may induce secondary physiological and behavioral responses
2012
Differential Diagnosis of Dyspnea
Pulmonary veins
Pulmonary arteries
YHEART LUNGS
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Approach to the Patient with Dyspnea
• History• Physical Examination• Diagnostic Testing
– chest x-ray– ECG, echocardiography– pulmonary function tests– pulse oximetry, arterial blood gases
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SatO2 vs. PaO2
• SatO2
– reflects the % of Hgb which binds O2
• PaO2
– reflects the driving pressure for oxygen in blood
• => Both factors combined determine oxygen content (תכולה)in blood
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Hypoxia vs. Hypoxemia:
• Hypoxia: the reduction of oxygen availability in tissues
• Hypoxemia: arterial oxygen tension (PaO2) < 60mmHg, or arterial oxygen saturation (SaO2) < 90%
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Hypoxemia: Mechanisms
Extrapulmonary:• Low Inspired O2 (high altitude)
• Hypoventilation (kyphoscoliosis, sedation)
Pulmonary:• Ventilation Perfusion Mismatch
– Shunt (pulmonary A-V fistula)
– Diffusion Impairment (ILD, pulm vascular dis)
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Arterial Blood Gases Normal Values
PO2 75-100 mmHg
PCO2 35-45 mmHg
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Arterial Blood Gases Normal Values
PO2 75-100 mmHg
PCO2 35-45 mmHg
PO2 can be expected to change depending on:•Ambient conditions•Alveolar ventilation, reflected by the PCO2!
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Alveolar-Arterial Oxygen Gradient
A-a gradient = PAO2 - PaO2
A – Alveolar
a – arterial
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Alveolar-Arterial Oxygen Gradient
A-a gradient = PAO2 - PaO2
A – Alveolara – arterial
A-a gradient is a measure of oxygen transfer at the alveolar-
capillary level2012
Alveolar Gas Equation
A-a gradient = PAO2 - PaO2
A – Alveolar
a – arterial
2012
Alveolar Gas Equation
A-a gradient = PAO2 - PaO2
PAO2 = FiO2 x (PB – PH2O) – PaCO2/R
A – Alveolar
a – arterial
FIO2 – Fractional oxygen content in inspired air
PB - Barometric pressure
PH2O – Water vapor pressure
R – Respiratory quotient 2012
# PaCO2/R reflects O2 removal from alveoli
PAO2 = FiO2 x (PB – PH2O) – PaCO2/R
A – Alveolar
a – arterial
FIO2 – Fractional oxygen content in inspired air
PB - Barometric pressure
PH2O – Water vapor pressure
R – Respiratory quotient
Alveolar Gas Equation
0.21 700 47 0.8
2012
Alveolar Gas Equation
PAO2 = 137 – PaCO2/0.8
A-a gradient = 137 – PaCO2/0.8 - PaO2
Assumptions:1. Room air (FiO2 = 0.21)2. Altitude of Jerusalem (PB = 700)3. Normal renal function (R = 0.8)4. At rest (R = 0.8)
2012
A-a Gradient
Upper limit of normal A-a gradient =
4 + ¼ age
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Case #1
28 yr. old male, found lying in the street, brought in by ambulance
– PO2 65 mmHg
– PCO2 49 mmHg
– Sat O2 92%
What is the A-a gradient?
2012
Case #1
28 yr. old male, found lying in the street, brought in by ambulance– PO2 65 mmHg – PCO2 49 mmHg – Sat O2 92%– A-a O2 10 mmHg (predicted = 11)
2012
Case #1
28 yr. old male, found lying in the street, brought in by ambulance– PO2 65 mmHg – PCO2 49 mmHg – Sat O2 92%– A-a O2 10 mmHg (expected = 11)Pin-point pupils. Needle-marks on arm.Diagnosis: heroin overdoseTreated with naloxone – excellent response
2012
Case #2
60 yr. old male, sudden onset of dyspnea 48h after hip replacement surgery
– PO2 72 mmHg
– PCO2 30 mmHg
– Sat O2 94%
What is the A-a gradient?
2012
Case #2
60 yr. old male, sudden onset of dyspnea 48h after hip replacement surgery– PO2 72 mmHg – PCO2 30 mmHg – Sat O2 94%– A-a O2 27.5 mmHg (predicted=19)
2012
Case #2
60 yr. old male, sudden onset of dyspnea 48h after hip replacement surgery– PO2 72 mmHg – PCO2 30 mmHg – Sat O2 94%– A-a O2 27.5 mmHg (predicted=19)
CT Pulmonary Angiogram: multiple pulmonary emboli
2012
– PO2 72 mmHg
– PCO2 30 mmHg
– Sat O2 94%
– A-a O2 27.5 (high)
– PO2 65 mmHg
– PCO2 49 mmHg
– Sat O2 92%
– A-a O2 10 (normal)
Pulmonary Emboli
Morphine Overdose
Extra-pulmonary disorder: Pulmonary disorder:
Case #1 Case #2
2012
• Is hypoxemia a result of
parenchymal or extraparenchymal
lung disease?
• A means of follow-up
Alveolar-Arterial Oxygen Gradient: Application
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PO2, PCO2 A-a gradient Interpretation
Normal Normal Normal
“Normal” or Abnormal
Abnormal Pulmonary Abnormality
Abnormal Normal Extra-pulmonary Abnormality
Alveolar-Arterial Oxygen Gradient: Interpretation
2012
Alveolar-Arterial Oxygen Gradient: Interpretation
Causes of Increased Alveolar-Arterial Oxygen Difference
Increased right-to-left shunt Anatomic
IntrapulmonaryIncreased ventilation-perfusion mismatchImpaired diffusionIncreased inspired partial pressure of oxygenDecreased mixed venous partial pressure of oxygenShift of oxyhemoglobin dissociation curve
2012
A-a Gradient
• FiO2 must be known accurately to calculate A-a gradient correctly!
• Use appropriate PB
• R (respiratory quotient) increased in renal failure, exercise
2012
Diagnostic Procedures in Pulmonology:
Fiberoptic bronchoscopy
Pleurocentesis
Closed Pleural Biopsy
2012
Fiberoptic Bronchoscopy
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Fiberoptic Bronchoscopy:
Diagnostic
• Inspection of the bronchial tree– Ostia of sub-segmental bronchi
• Bronchoalveolar lavage• Endobronchial biopsy
– Forceps– Brush
• Transbronchial biopsy– Forceps (lung parenchyma)– Needle (lymph nodes)
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Bronchoalveolar Lavage (BAL)
• BAL serves for alveolar sampling
• Procedure:– Bronchoscope is wedged at a distal
point in the bronchial tree
– Saline is instilled through the bronchoscope
– Fluid is collected for analysis
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BAL fluid analysis
• Differential cell count (normal>85% macrophages)
• Pathogens / cytological signs of infection
• Malignant cells• Foreign Bodies (Asbestos, Silica)
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Diffuse Infiltrates in Immunocompromised Host
Chest 2000 2012
Fiberoptic Bronchoscopy:
Therapeutic
• Bronchial toilet• Restoration of airway patency
– Laser photo-coagulation / resection– Electro-cautery– Stent deployment– Brachy-radiotherapy– Foreign body removal
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Endobronchial brachytherapy
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Laser photoresection
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Endobronchial Electrcautery
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Endobronchial stents
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Pleurocentesis
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Pleurocentesis
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Abram’s Pleural Biopsy Needle
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בהצלחה !!
2012
