Dyspnea, Hypoxemia & Respiratory Failure 2012 Pulmonary Medicine Introductory Course 4 th year Workshop Dr. Samir Nusair, MD Dr. Nissim Arish, MD.

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

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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

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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

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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)

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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?

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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%– A-a O2 10 mmHg (predicted = 11)

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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%– A-a O2 10 mmHg (expected = 11)Pin-point pupils. Needle-marks on arm.Diagnosis: heroin overdoseTreated with naloxone – excellent response

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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?

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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)

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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

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– 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

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• 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

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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

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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

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Diagnostic Procedures in Pulmonology:

Fiberoptic bronchoscopy

Pleurocentesis

Closed Pleural Biopsy

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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 !!

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