Mechanics of Breathing

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Mechanics of Breathing
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Introduction

• Pulmonary ventilation
• Moving air into and out of the lungs
• Breathing
• Inspiration moving air into the lungs
• Expiration moving air out of lungs

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Pressure Relationships

• Intrapulmonary pressure
• Pressure within the alveoli (lungs)
• Changes with phases of breathing
• Always equalizes itself with atmospheric pressure
• Intrapleural pressure
• Pressure within intrapleural space
• Always 4mmHg less than intrapulmonary pressure

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Atalectasis

• Any conditions that causes intrapulmonary
  pressure to equal intrapleural pressure will
  cause the lungs to collapse
• This means they lose the ability to move air
  since there is NO more pressure difference
• pneumothorax air in the intrapleural space due
  to trauma

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Atelectasis
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Pulmonary ventilation

• Question Why does breathing happen?
• ONLY acceptable answer Volume changes lead to
  pressure changes which lead to the flow of gases
  to equalize the pressure

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Inspiration

• Main inspiratory muscles
• Diaphragm external intercostals
• Thoracic dimensions change to increase volume of
  thoracic cavity by 0.5 liters
• Intrapulmonary pressure drops 1-3 mmHg and air
  rushes info normal quiet inspiration
• A deep forced inspiration requires activation of
  accessory muscles

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Expiration

• A passive process dependent on natural lung
  elasticity
• The lungs recoil, volume decreases, alveoli
  compress, intrapulmonary pressure rises, gas
  outflows to equalize the pressure with
  atmospheric pressure
• Forced expiration requires contraction of muscles
  of the abdominal wall

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Physical factors influencing

• Pulmonary ventilation can be influenced by 4
  physical factors
• Respiratory passage resistance
• Lung compliance
• Lung elasticity
• Alveolar surface tension forces

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Respiratory passage resistance

• Friction as air moves through passages
• Smooth muscle bronchoconstriction and,
• Local accumulations of mucus, infectious
  material, and tumors will cause the air flow to
  be reduced
• Disorders such as asthma

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Lung compliance

• The ease with which lungs can readily expand
• Affected by the elasticity of the lungs and the
  thoracic cage
• Diminished by 3 main factors
• Fibrosis of the lung tissue
• Ossification and/or muscle paralysis impairs
  flexibility of the thoracic cage
• Blockage of the passageways

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Lung fibrosis
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Lung Elasticity

• Essential for normal expiration
• Emphysema tissue becomes less elastic and more
  fibrous
• Read ALL the imbalances and info about emphysema
  within your handout

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Page 415 in text
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Alveolar Surface Tension Forces

• Surface tension molecules of liquid hold
  together with hydrogen bonds
• Surfactant substance which interferes with
  cohesion of water molecules so less energy is
  needed to expand the lungs
• IRDS Infant Respiratory Distress Syndrome
  read imbalance

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Type II Cells
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End of Quiz 3 Material
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Gas Exchanges in the Body
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Gas Exchanges

• Occur
• Between the blood and the alveoli AND
• Between the blood and the tissue cells
• Takes place by simple diffusion
• Depends on partial pressures of oxygen carbon
  dioxide
• That exist on opposite sides of the exchange
  membrane
• Diagrams on page 416-417 of text

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Daltons Law

• Total pressure exerted by a mixture of gases is
  equal to the sum of the partial pressures of each
  individual gas
• (Ptotal P1 P2 P3 )
• The partial pressure of each gas is directly
  proportional to its in the mixture

N2 78.08, O2 20.95, CO2 0.04
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Henrys law

• Each gas will dissolve in a liquid in proportion
  to its partial pressure and solubility
  coefficient of the liquid
• CO2 .57
• O2 .024
• N2 .012
• Solubility increases with increasing partial
  pressure
• Solubility decreases with increasing temperature

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Hyperbaric Conditions

• Hyperbaric oxygen chambers designed to force
  greater amounts of oxygen into patients blood

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Life Applications

• Write down in detail the things we discuss!!!!
• Oxygen toxicity
• Nitrogen narcosis
• Decompression sickness
• High altitude sickness

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Now what would happen if you breathed 100 percent
oxygen?

• Exposed to 100 percent oxygen at normal air
  pressure for 48 hours
• A highly reactive form of the oxygen molecule,
  called a free radical destroys proteins and
  membranes in the epithelial cells.

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In humans breathing 100 percent oxygen at normal
pressure, here's what happens

• Fluid accumulates in the lungs.
• Gas exchange in the alveoli slows down so person
  has to breathe more to get enough oxygen.
• Volume of exchangeable air decreases by 17
  percent.

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SCUBA

• In contrast, when 100 percent oxygen is breathed
  under high pressure (more than four times that of
  atmospheric pressure), acute oxygen poisoning can
  occur with these symptoms
• Nausea
• Dizziness
• Muscle twitches
• Blurred vision
• Seizures/convulsions
• Such high oxygen pressures can be experienced by
  military SCUBA divers using rebreathing devices,
  divers being treated for the bends in hyperbaric
  chambers or patients being treated for acute
  carbon monoxide poisoning. These patients must be
  carefully monitored during treatment.

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Nitrogen Narcosis

• As the total gas pressure increases with
  increasing dive depth,
• the partial pressure of nitrogen increases
• more nitrogen becomes dissolved in the blood.
• This high nitrogen concentration impairs the
  conduction of nerve impulses and mimics the
  effects of alcohol or narcotics.

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Symptoms of nitrogen narcosis include

• Wooziness
• Giddiness
• Euphoria
• Disorientation
• loss of balance
• loss of manual dexterity

• slowing of reaction time
• fixation of ideas
• impairment of complex reasoning.
• These effects are exacerbated by cold, stress,
  and a rapid rate of compression.

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Decompression Sickness (the bends)

• As pressure increases, solubility of gases
  increase
• Larger quantities of Nitrogen are forced into the
  body fluid/blood but not used by the body
• Ascending rapidly causes nitrogen gas to become
  less soluble and bubble out of the blood too
  fast to be exhaled

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Decompression sickness

• Gas collected in joint spaces and can also cause
  air embolisms which can lead to heart attack
  stroke
• Treatment
• Hyperbaric chamber
• Take back down to depth bring up slowly

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Internal External Respiration
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Factors influencing internal external
respiration

• Partial pressure gradients and gas solubilities
  cont
• Oxygen has low solubility but steep partial
  pressure gradient (104 mmHg in alveoli 40 mmHg
  in blood 64 mmHg pressure gradient)
• Carbon dioxide has solubility 20x greater than
  oxygen but partial pressure gradient is only 5
  mmHg

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Factors influencing internal external
respiration

• Partial pressure gradients and gas solubilities
• Due to the ratios of solubility coefficients and
  pressure gradients
• Equal amounts of gases are exchanged
• pH is not affected
• H2O CO2 H2CO3 (carbonic acid)

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Factors influencing internal external
respiration

• Thickness of respiratory membranes
• 0.5 to 1.0 micrometers
• Hypoxia oxygen deprivation
• Thickness edematous (swollen) tissue can be
  caused by congestion and pneumonia
• Emphysema infections can thicken membranes

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Factors influencing internal external
respiration

• Surface Area
• 70-80 square meters for gas exchange
• Emphysema
• Walls of alveoli break down
• Less surface area to volume ratio

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Transport of respiratory gases
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Oxygen Transport

• Most oxygen is bound to hemoglobin for transport
  (blood is cherry red)
• Vocabulary to understand
• Loading binding oxygen to hemoglobin for
  transport
• Unloading releasing oxygen from hemoglobin to
  go into tissue cells

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• http//ems.lchospital.com/education/respiration.ht
  m
• http//www.stemnet.nf.ca/dpower/resp/exchange.htm
  
• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter25/

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Factors affecting hemoglobin transport

• PO2
• Affects unloading rate
• 20-25 of oxygen unloaded to tissues in one
  systemic circuit
• Leaves a venous reserve of 75
• This is why brain death will begin to occur 3-4
  minutes after your heart stops
• CPR must begin ASAP!!

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Factors affecting hemoglobin transport

• As the temperature increases oxygen unloading
  increases
• Hard working tissues high metabolism rate
  heat produced more oxygen unloaded
• Hard working tissues need more oxygen to produce
  more ATP the heat is one way the tissues signal
  the body to bring more oxygen
• Cold tissues low metabolism less oxygen
  unloaded
• Nose Cheeks are red when cold because the body
  is trying to bring them a little more heat no
  additional oxygen is unloaded in this case

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Factors affecting hemoglobin transport

• Active tissues made lots of ATP so lots of
  carbon dioxide and hydrogen ions have been
  produced as a waste product acidosis
  increased oxygen unloading
• CO2 H2O H2CO3 (carbonic acid)
• Know the types of hypoxia and the symptoms
  treatment of CO (fix this in notes) poisoning
  see handout
• Also read the bracketed info on page 743 of
  handout

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Carbon Monoxide poisoning
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Carbon dioxide transport

• 7 dissolved in plasma
• 20 bound to hemoglobin aka.
  Carbaminohemoglobin
• 70 is in the form of the bicarbonate ion (HCO3-)
• Carbonic acid and bicarbonate ion work together
  as a buffer system to resists changes in pH

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Hypoventilation

• Slow shallow respiration
• Not adequate expiration so
• CO2 is not vented out of the body
• Production of excess acid
• H2O CO2 H2CO3 (carbonic acid)
• Respiratory acidosis results

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Hyperventilation

• Deep rapid respiration
• Too much CO2 is vented out of the body
• Not enough acid production
• H2O CO2 H2CO3 (carbonic acid)
• Respiratory alkalosis results
• Treatment trap the CO2 and rebreathe it till
  breathing returns to normal

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Imbalances

• Pages 744-745 of handout

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Chronic Bronchitis

• Symptoms inflammation of mucosa chronic mucus
  production
• Impairs ventilation and gas exchange
• Reduction of airway diameter
• blue bloater hypoxia leads to cyanosis CO2
  retention leads to hyperinflation of chest wall
• Causative factors cigarette smoking

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• Normal
• Bronchitis

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Obstructive Emphysema

• pink puffer
• Gas exchange adequate until end stage so stay
  oxygenated and pink
• Breathing is very labored due to lack of alveolar
  recoil
• Barrel chest from hyperinflation of lungs
• Alveolar walls collapse loss of surface area
• Causative factor cigarette smoking

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4 features in common

• Both emphysema and chronic bronchitis have
• Smoking history
• Dyspnea air hunger due to disfunctional
  breathing
• Apnea no breathing
• Eupnea normal breathing
• Coughing pulmonary infections
• Will develop respiratory failure, hypoxia,
  acidosis

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Lung Cancer

• Basic Info
• 1/3 of all cancer deaths are due to lung cancers
• 90 have a smoking history
• Metastasizes very rapidly due to vascularity of
  lungs

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3 types

• Know the descriptions of these 3 types of lung
  cancers from your handout
• Squamous cell carcinoma
• Adenocarcinoma
• Oat cell (small cell) carcinoma

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Squamous cell carcinoma
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Adenocarcinoma
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Oat cell carcinoma
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Treatments

• Resection of diseased portion of lung
• Radiation therapy
• Chemotherapy

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Lung Resection
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Developmental Aspects
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READ your handout

• Read through the Developmental Aspects section of
  your notes and your handout
• Know the related clinical terms on the back page
  of your handout

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STUDY