Lung: Anatomy & Physiology

1. Lung:Anatomy & Physiology William V Walker, MD, FACP MHIMA Branson, MO, 4/27/2011

2. What are these?And why do have them? Oxygenation Ventilation Elimination (Volatiles)

3. Gross Anatomy Epiglottis protects airway from esophageal contents Larynx allows phonation Tracheal rings (cartilage) prevent collapse The bronchial tree - Trachea - Mainstem bronchi - Segmental bronchi - Bronchioles - Alveoli

4. The Bronchial Tree

5. Alveoli (Leaves on the Tree)

6. Oxygenation – Intake • Oxygen is the currency that drives metabolism • FIO2 is fraction of inspired oxygen • Inspired air is 21% oxygen at sea level • Inspired air is > 21% oxygen when supplemented • Near 100% with 100% facemask and 15L NRB • Inspired air is < 21% • At higher altitudes • Fire • Non-ventilated areas (suffocation)

7. Oxygenation – Delivery • Oxygen is carried by blood • > 98% bound to hemoglobin • < 2% dissolved in the blood • Determinates • Inspired FIO2 • Diffusion capacity of the lung • Cardiac output • Red blood cell mass (Hg count/ effect of anemia) • Unloading (temperature, pH, 2-3DPG)

8. Oxygenation – Measurement • Measured directly by ABG • pO2 = partial pressure of oxygen • Measured indirectly by oximetry • SpO2 = hemoglobin saturation • Affected by other bound compounds such as carbon monoxide • “Normal” • Arterial pO2 ~ 100 • Venous pO2 ~ 40

9. Unloading OxygenOxygen-Hemoglobin Dissociation Oxygen Saturation Oxygen partial pressure (PaO2)

10. Unloading OxygenOxygen-Hemoglobin Dissociation Oxygen Saturation Oxygen partial pressure (PaO2)

11. Oximetry does not measure oxygen level directly Measures oxygen saturation on hemoglobin ‘Predicts’ oxygenation based on dissociation PaO2SpO2 100 98 90 97 80 95 70 93 60 89 50 84 40 75 30 57 Oxygenation – Measurement

12. Ventilation – Inhalation • Air rushes into region of lower pressure • Diaphragm contracts, causing it to descend • Intercostals contract, elevating sternum and ribcage • The volume of the chest increases, which lowers pressure

13. Ventilation – Exhalation • The muscles relax • Restores pre-inhalation volume which increases pressure • Forces air back out

14. Bellows

15. Ventilation – Measurement • Ventilation brings oxygen in and takes carbon dioxide out • Ventilation is more stimulated by carbon dioxide than hypoxemia • Measured directly by ABG • pCO2 = partial pressure of carbon dioxide • “Normal” • Arterial pCO2 ~ 40 • Venous pCO2 ~ 45

16. Some ABG Conclusions • pO2 • Has to be considered in light of the FIO2, which is usually also reported (eg, pO2 = 60 on room air vs NRB or facemask) • Lowered with insufficient intake or markedly increased demand (bronchial tree, alveoli, anemia, cardiac output, PE, sepsis…) • pCO2 • Reflects the bellows function • Higher with inability to exhale, increased production

17. Disease – Bronchial Tree • “-itis” is inflammation at the site described, due to infection or irritation (smoking) • May lead to structural damage or air trapping • Treated with antibiotics or anti-inflammatories (steroids)

18. Fixed Obstruction to Flow USBR.gov

19. Disease – Air Trapping • May be due to chronic bronchitis, hyperactive airways (eg, asthma, RAD) or collapse of airways (eg, emphysema) • Manifested as inadequate ventilation • Treated with bronchodilators or mucolytics

20. Disease – Pneumonitis • Inflammation at the alveolar level, due to infection or irritation • May involve airspace or the interstitial space • May lead to scarring or other structural disease • Treated with antibiotics, anti-inflammatories and support of ventilation

21. ICD Chapter 8 Diseases of the respiratory system (460-519) • 460-466 Acute respiratory infections • 470-478 Other diseases of the upper respiratory tract • 480-487 Pneumonia and influenza • 490-496 COPD and allied conditions • 500-508 Pneumoconioses, other lung disease due to external agents • 510-519 Other diseases of respiratory system

22. Contact Information William V Walker, MD, FACP 16715 Chesterfield Manor Drive Chesterfield, MO 63005 wvw817@gmail.com