The Lungs IENG 431 Carter J. Kerk, PhD, PE, CSP, CPE Industrial Engineering Department South Dakota School of Mines Spring 2009
Chapter 2 Assignment • Read Plog Chapter 2 • Study ACB: Respiratory System • Color Plates 91, 94-97 • Due: ?
Outline • Anatomy • Respiration • Hazards • Natural Defenses • Evaluating Impairment
Introduction • Route of entry: Airborne hazards are the most serious concern • Processes: welding, grinding, spraying, hot processes, engine exhausts • Pollen, spores • Lungs: efficient transfer of gases in and out of the body • But also provide a route of entry for hazards
Anatomy & Function of the Lungs • Regions of the respiratory tract • Upper (nasopharyngeal) • Middle (tracheobronchial) • Lower (distal) • ACB Plates 91-97
Upper (Nasopharyngeal) • Head, nose, nasal passages, sinuses, mouth, tonsils, epiglottis, back of throat • Lined with mucous membrane • Moist, sticky substance captures materials • Many small hairs • Help to trap particles
Middle (Tracheobronchial) • Trachea (windpipe), bronchi • Rings of cartilage and muscle • Cartilage provides structural support • Muscles contract to help force air • Coughing, sneezing • Lined with mucous membrane and hairs (cilia) • Cilia move like waves to push mucus and particles upward • Cigarette smoking can paralyze the cilia • Particle-laden mucus is removed by coughing, expectorating, or swallowing
Lower (Distal) • Bronchi split (bifurcate) repeatedly into two smaller passages (17 times, 217 = 131,072) called bronchioles • Diameters decrease accordingly • Bronchioles end in microscopic sacs called alveoli (site of gas exchange) • Alveolar membrane is one cell thick (pneumocytes), surrounded by capillaries • Passive diffusion • Surface Area: 100 m2 (1080 ft2)
Surface Areas for 5’9” person
How does diffusion work?
Definition: Microns (Micrometer) • One thousandth of a millimeter • 0.001 mm = 1 mm • Greek letter, m • Useful in discussion of the size of inhaled particles • Visible to human eye • > 100 mm = 0.1 mm = 0.01 cm • Human hair diameter • 5 – 500 mm = 0.005 – 0.5 mm
Protective Mechanisms of the Respiratory Tract • Larger particles (>10 mm) • Removed in nose and upper airways • 5 – 10 mm • Captured in tracheal region • 3 – 5 mm • Contact mucus lining in tracheal or bronchi • 0.5 – 3 mm • Can reach alveolar region, but few do
Capture of particles • Mucus (moist, sticky) linings • Tortuous pathway • Multitude of branches and splits • Large surface area of the route • Once particles are captured in mucus, they are removed by the mucociliary elevator or ladder • Cough reflex
Protection in the Alveolar Region • Primary defense – macrophages (specialized white blood cells) • Engulf foreign objects and attempt to dissolve them • The smallest of particles may pass through cell membranes and lodge between cells (interstitial space)
Airborne Hazardous Materials • Aerodynamic Diameter • Useful for comparing particles with irregular shapes (dusts, fibers, etc.) to particles with regular shapes (droplets, mists, etc.) • The diameter of a reference spherical particle with a unit density of one (1) that has the same settling velocity as the contaminant particle
Classes of Airborne Materials • Particulates / aerosols • Solid particles, dusts, fibers, mists, droplets, fumes • Gases / vapors • Gaseous contaminants, vapors • Oxygen-deficient atmospheres • < 19.5% oxygen • Combination • Any combination of particulates and/or gases, including oxygen-deficient atmospheres
Effects of Inhaled Materials • Airborne toxins • Local effects on tissues • Ammonia irritation in respiratory tract • Systemic effects through blood transport • Carbon tetrachloride (liver) • Solubility • More soluble – upper respiratory tract, moist tissue around eyes – ammonia • Less soluble – penetrate to middle and lower respiratory tract – phosgene gas
Size-selective Sampling • Recall the relationship between particle size and site deposition? • Thus size-selective sampling becomes important • ACGIH has defined three ranges (or fractions) • Inhalable • Thoracic • respirable
Size-Selective Sampling
Size-Selective Sampling • Some OSHA PELs are established for the respirable fraction • Example: crystalline silica • Table Z-1, Silicon • Total Dust, 15 mg/m3 • Respirable fraction, 5 mg/m3
Occupational Diseases Associated with Airborne Particulates • Pneumoconiosis • Physiological Responses • Mineral Fibers and Other Fibers • Metals • Organic Particles
Evaluating Lung Impairments • Scarring and damage of lung tissue causes two distinct patterns of impairment of lung function • Obstructive • Restrictive • Spirometry • Lung function test
Obstructive Impairment of Lung Function • Results from damage to small airways or bronchioles • Decreased ability to exhale air • Coal deposits can cause permanent dilation of small air passages, reducing volume of air that can be forced out • Expiratory Volume – volume of air that can be exhaled – can be measured for evaluation
Restrictive Impairment of Lung Function • Vital Capacity – maximum volume of air that can be inhaled and then exhaled normally (see next slide) • Restrictive impairment – a reduction in this volume • Physically demanding tasks become more difficult • Caused by fibrotic lesions which reduce alveolar surface area
Reference • Nims DK. Basics of Industrial Hygiene. John Wiley & Sons, Inc., 1999.
Chapter 2 Assignment • Read Plog Chapter 2 • Study ACB: Respiratory System • Color Plates 91, 94-97 • Due: ?
