The Lungs

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The Lungs

• IENG 431
• Carter J. Kerk, PhD, PE, CSP, CPE
• Industrial Engineering Department
• South Dakota School of Mines
• Spring 2009

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Chapter 2 Assignment

• Read Plog Chapter 2
• Study ACB Respiratory System
• Color Plates 91, 94-97
• Due ?

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Outline

• Anatomy
• Respiration
• Hazards
• Natural Defenses
• Evaluating Impairment

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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

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Anatomy Function of the Lungs

• Regions of the respiratory tract
• Upper (nasopharyngeal)
• Middle (tracheobronchial)
• Lower (distal)
• ACB Plates 91-97

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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

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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

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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)

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Surface Areas for 59 person
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How does diffusion work?
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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
• gt 100 mm 0.1 mm 0.01 cm
• Human hair diameter
• 5 500 mm 0.005 0.5 mm

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Protective Mechanisms of the Respiratory Tract

• Larger particles (gt10 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

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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

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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)

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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

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Classes of Airborne Materials

• Particulates / aerosols
• Solid particles, dusts, fibers, mists, droplets,
  fumes
• Gases / vapors
• Gaseous contaminants, vapors
• Oxygen-deficient atmospheres
• lt 19.5 oxygen
• Combination
• Any combination of particulates and/or gases,
  including oxygen-deficient atmospheres

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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

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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

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Size-Selective Sampling
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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

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Occupational Diseases Associated with Airborne
Particulates

• Pneumoconiosis
• Physiological Responses
• Mineral Fibers and Other Fibers
• Metals
• Organic Particles

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Evaluating Lung Impairments

• Scarring and damage of lung tissue causes two
  distinct patterns of impairment of lung function
• Obstructive
• Restrictive
• Spirometry
• Lung function test

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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

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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

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Reference

• Nims DK. Basics of Industrial Hygiene. John
  Wiley Sons, Inc., 1999.

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Chapter 2 Assignment

• Read Plog Chapter 2
• Study ACB Respiratory System
• Color Plates 91, 94-97
• Due ?