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

Definition: Dyspnea is an abnormally uncomfortable awareness of breathing ATS 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 Y HEART LUNGS 2012

Approach to the Patient with Dyspnea History Physical Examination Diagnostic Testing –chest x-ray –ECG, echocardiography –pulmonary function tests –pulse oximetry, arterial blood gases 2012

SatO 2 vs. PaO 2 SatO 2 –reflects the % of Hgb which binds O 2 PaO 2 –reflects the driving pressure for oxygen in blood => Both factors combined determine oxygen content (תכולה)in blood 2012

Hypoxia vs. Hypoxemia: Hypoxia: the reduction of oxygen availability in tissues Hypoxemia: arterial oxygen tension (PaO 2 ) < 60mmHg, or arterial oxygen saturation (SaO 2 ) < 90% 2012

Hypoxemia: Mechanisms Extrapulmonary: Low Inspired O 2 (high altitude) Hypoventilation (kyphoscoliosis, sedation) Pulmonary: Ventilation Perfusion Mismatch –Shunt (pulmonary A-V fistula) –Diffusion Impairment (ILD, pulm vascular dis) 2012

Arterial Blood Gases Normal Values PO mmHg PCO mmHg 2012

Arterial Blood Gases Normal Values PO mmHg PCO mmHg PO 2 can be expected to change depending on: Ambient conditions Alveolar ventilation, reflected by the PCO 2 ! 2012

Alveolar-Arterial Oxygen Gradient A-a gradient = P A O 2 - P a O 2 A – Alveolar a – arterial 2012

Alveolar-Arterial Oxygen Gradient A-a gradient = P A O 2 - P a O 2 A – Alveolar a – arterial A-a gradient is a measure of oxygen transfer at the alveolar- capillary level 2012

Alveolar Gas Equation A-a gradient = P A O 2 - P a O 2 A – Alveolar a – arterial 2012

Alveolar Gas Equation A-a gradient = P A O 2 - P a O 2 P A O 2 = F i O 2 x (P B – P H 2 O ) – P a CO 2 /R A – Alveolar a – arterial F I O 2 – Fractional oxygen content in inspired air P B - Barometric pressure PH 2 O – Water vapor pressure R – Respiratory quotient 2012 # P a CO 2 /R reflects O 2 removal from alveoli

P A O 2 = F i O 2 x (P B – P H 2 O ) – P a CO 2 /R A – Alveolar a – arterial F I O 2 – Fractional oxygen content in inspired air P B - Barometric pressure PH 2 O – Water vapor pressure R – Respiratory quotient Alveolar Gas Equation

Alveolar Gas Equation P A O 2 = 137 – P a CO 2 /0.8 A-a gradient = 137 – P a CO 2 /0.8 - P a O 2 Assumptions: 1.Room air (F i O 2 = 0.21 ) 2.Altitude of Jerusalem (P B = 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 2012

Case #1 28 yr. old male, found lying in the street, brought in by ambulance –PO 2 65 mmHg –PCO 2 49 mmHg –Sat O 2 92% What is the A-a gradient? 2012

Case #1 28 yr. old male, found lying in the street, brought in by ambulance –PO 2 65 mmHg –PCO 2 49 mmHg –Sat O 2 92% –A-a O 2 10 mmHg (predicted = 11) 2012

Case #1 28 yr. old male, found lying in the street, brought in by ambulance –PO 2 65 mmHg –PCO 2 49 mmHg –Sat O 2 92% –A-a O 2 10 mmHg (expected = 11) Pin-point pupils. Needle-marks on arm. Diagnosis: heroin overdose Treated with naloxone – excellent response 2012

Case #2 60 yr. old male, sudden onset of dyspnea 48h after hip replacement surgery –PO 2 72 mmHg –PCO 2 30 mmHg –Sat O 2 94% What is the A-a gradient? 2012

Case #2 60 yr. old male, sudden onset of dyspnea 48h after hip replacement surgery –PO 2 72 mmHg –PCO 2 30 mmHg –Sat O 2 94% –A-a O mmHg (predicted=19) 2012

Case #2 60 yr. old male, sudden onset of dyspnea 48h after hip replacement surgery –PO 2 72 mmHg –PCO 2 30 mmHg –Sat O 2 94% –A-a O mmHg (predicted=19) CT Pulmonary Angiogram: multiple pulmonary emboli 2012

–PO 2 72 mmHg –PCO 2 30 mmHg –Sat O 2 94% –A-a O (high) –PO 2 65 mmHg –PCO 2 49 mmHg –Sat O 2 92% –A-a O 2 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 2012

PO 2, PCO 2 A-a gradientInterpretation Normal “Normal” or Abnormal AbnormalPulmonary Abnormality AbnormalNormalExtra- 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 Intrapulmonary Increased ventilation-perfusion mismatch Impaired diffusion Increased inspired partial pressure of oxygen Decreased mixed venous partial pressure of oxygen Shift of oxyhemoglobin dissociation curve 2012

A-a Gradient F i O 2 must be known accurately to calculate A-a gradient correctly! Use appropriate P B R (respiratory quotient) increased in renal failure, exercise 2012

Diagnostic Procedures in Pulmonology: Fiberoptic bronchoscopy Pleurocentesis Closed Pleural Biopsy 2012

Fiberoptic Bronchoscopy 2012

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) 2012

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 2012

BAL fluid analysis Differential cell count (normal>85% macrophages) Pathogens / cytological signs of infection Malignant cells Foreign Bodies (Asbestos, Silica) 2012

Diffuse Infiltrates in Immunocompromised Host

Chest

Fiberoptic Bronchoscopy: Therapeutic Bronchial toilet Restoration of airway patency –Laser photo-coagulation / resection –Electro-cautery –Stent deployment –Brachy-radiotherapy –Foreign body removal 2012

Endobronchial brachytherapy 2012

Laser photoresection 2012

Endobronchial Electrcautery 2012

Endobronchial stents 2012

Pleurocentesis 2012

Pleurocentesis 2012

Abram’s Pleural Biopsy Needle 2012

!! בהצלחה 2012