The Respiratory System

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The Respiratory System

• Chapter 10

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  related

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Introduction

• Main job of respiratory system is to bring oxygen
  (O2) into the body and to carry carbon dioxide
  (CO2) out of body.
• Bodys cells need a constant supply of oxygen to
  burn nutrients to produce energy.
• How does this take place in a simple, single
  celled animal?
• How does this differ from a complex animal such
  as a dog or cat?

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Two types of Respiration

• External Respiration
• Occurs in the lungs.
• Is the exchange of oxygen and carbon dioxide
  between the air that is inhaled into the lungs
  and the blood flowing through the pulmonary
  capillaries.
• Without which, there would be no oxygen in the
  blood to be transmitted to the system.
• Internal Respiration
• Takes place between the bodys cells and the
  blood.
• Cells receive oxygen and dispose of their carbon
  dioxide

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External Respiration
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Internal Respiration
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The Respiratory System

• Composed of
• Lungs
• Nostrils
• Nasal passages
• Pharynx
• Larynx
• Trachea
• Bronchi
• Bronchioles
• Alveolar ducts
• Alveoli

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Functions of the Respiratory System

• Primarily
• Oxygen- carbon dioxide exchange.
• Secondarily
• Voice production
• Body temperature regulation
• Acid-base balance regulation
• Sense of smell

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Voice Production

• Also called phonation.
• Begins in the larynx (voice box).
• Two fibrous connective tissue bands called the
  vocal cords (or vocal folds) stretch across the
  lumen of the larynx and vibrate as air passes
  over them.
• Other structures such as thorax (chest cavity),
  nose, mouth, pharynx (throat), and sinuses may
  contribute resonance and other characteristics to
  the vocal sounds.

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Body Temperature Regulation

• Cold conditions
• Superficial blood vessels just under the
  epithelium of the nasal passages helps warm
  inhaled air before it reaches the lungs.
• Keeps chilled air from circulating through the
  lungs.
• What could be the problem with this?
• Hot Conditions
• Aids in cooling through panting.
• Rapid respiration movements caused during panting
  cause increased evaporation of fluid from the
  lining of the respiratory passages and mouth,
  which helps to cool the blood just under the
  epithelium.

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Acid Base Balance

• Important homeostatic mechanism in the body.
• pH- unit used to measure relative acidity or
  alkalinity.
• Lower the pH, the more acidic the environment
• Higher the pH, the more alkaline the environment.
• A pH of 7 is neutral, neither acidic or alkaline.
• Normal pH of the blood is 7.4 (acceptable range
  of 7.35-7.45).

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Acid-Base Balance Continued

• Respiratory system contributes to the process of
  acid-base control by its ability to influence the
  amount of CO2 in the blood.
• Higher CO2, lower the blood pH, more acidic the
  blood.
• Respiratory system can alter CO2 content in the
  blood by adjusting how fast air is breathed in
  and out.

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Sense of Smell

• Also called the olfactory sense.
• Receptors are contained in patches of sensory
  epithelium located up high in the nasal passages.

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Structure of Respiratory System

• Consists of lungs and system of tubes that
  connects them with the external environment.
• Upper Respiratory Tract
• All of the respiratory structures outside the
  lungs.
• Lower Respiratory Tract
• All of the respiratory structures within the
  lungs.

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Upper Respiratory Tract

• Includes
• (all air that enters and leaves lungs does so
  through the upper respiratory structures).
• Nose
• Pharynx (throat)
• Larynx (voice box)
• Trachea (wind pipe)

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Nose

• Begins with nostrils also known as nares.
• Are external openings of the respiratory tube
  that lead into the nasal passages.

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Nasal Passages

• Located between the nares and the pharynx.
• Nasal Septum- a wall that separates the left
  nasal passage from the right.
• Hard and Soft palates- separates the nasal
  passages from the mouth.
• Contain turbinates (nasal conchae)-thin,
  scroll-like bones covered with nasal epithelium
  that occupy most of the lumen of the nasal
  passages.

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Nasal Turbinates

• Two sets are found in each nasal passage.
• Dorsal Turbinate
• Ventral Turbinate
• These divide each nasal passage into 3 main
  passageways, each called a nasal meatus.
• Ventral nasal meatus is located between the
  ventral turbinate and the floor of the nasal
  passage
• Middle nasal meatus is located between the two
  turbinates.
• Dorsal nasal meatus is located between the dorsal
  turbinate and the roof of the nasal passage.
• Common nasal meatus is located on either side of
  the nasal septum, is continuous with other 3
  meatuses.

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Lining of the nasal passages

• Consists of pseudostratified columnar epithelium
  with cilia projecting from the cell surfaces up
  into a layer of mucus that is secreted by many
  mucous glands and goblet cells.
• Cilia project from the cell surfaces up into a
  layer of mucus
• Extensive complex of large blood vessels lies
  just beneath the nasal epithelium.

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Functions of the Nasal Passages

• Housing receptors for sense of smell.
• Condition the inhaled air
• Warming
• Warmed by blood flowing in blood vessels
• Humidifying
• By the mucus and other fluids on the epithelial
  surface
• Filtering
• Helps to remove particulate matter before it
  reaches lungs.
• Due to twists and turns of turbinates.
• Respiratory infections cut down on this
  filtering. Why?

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Paranasal Sinuses

• Usually just called sinuses
• Outpouchings of the nasal passages that are
  contained within spaces in certain skull bones.
• Each sinus is named after the skull bone that
  houses it.
• Most animals have two frontal sinuses and
  maxillary sinuses.
• Some animals (including humans) have two more.
• Sinuses have same ciliated lining as the nasal
  passages. Cilia keep fluid and debris from
  accumulating in sinuses and obstructing the
  openings of the nasal passages.

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Sinusitis

• Inflammation of the sinuses. Due to infection,
  tumors, etc.
• Build up of pressure can be very uncomfortable
  for the animal.
• Can be treated with medication but if
  ineffective, hole may need to be drilled into the
  sinus to allow drainage.

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Pharynx (Throat)

• Common passageway for both respiratory and
  digestive systems.
• Rostral end is divided into
• Nasopharynx (respiratory passageway)
• Oropharynx (digestive passageway)
• Caudal end is divided into
• Esophagus (digestive passageway)
• Larynx (respiratory passageway)

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Breathing and Swallowing

• Pharynx has to stay open to allow airflow.
• Larynx and pharynx work together to prevent
  swallowing from interfering with breathing and
  vice versa.
• Swallowing requires
• stopping the process of breathing,
• covering the opening of the larynx,
• moving material to rear of pharynx,
• open the esophagus,
• move material into it,
• open covering to larynx,
• breathing resumes.

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GOropharynx HLarynx JNasopharynx KEsophagus I
Trachea
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Larynx

• Commonly called the voice box .
• Short, irregular tube that connects the pharynx
  with the trachea.
• Made of segments of cartilage that are connected
  to each other and the surrounding tissues by
  muscles.
• Supported in place by the hyoid bone.

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Cartilage components of the Larynx

• Epiglottis
• single, leaf-shaped projects forward from the
  ventral portion of the larynx
• During swallowing, the epiglottis is pulled back
  to cover the opening of the larynx
• Arytenoid cartilages
• paired attachment site of the vocal cords
• Muscles adjust the tension of the vocal cords by
  moving the cartilages.
• Arytenoid cartilages and the vocal cords form the
  boundaries of the glottis-the opening into the
  larynx.
• Thyroid cartilages
• Shaped as a V that forms and supports the ventral
  portion of the larynx.
• Cricoid cartilage
• Ring-shaped, helps from and support the caudal
  portion of the larynx.

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Larynx continued

• Vestibular folds (false vocal cords) - are found
  in nonruminant animals. Are a second set of
  connective tissue bands.
• Not involved in voice production.
• Each side of larynx, blind pouches called lateral
  ventricles project laterally into the space
  between the vocal cords and the vestibular folds.
  
• These lateral ventricles are often involved in
  the treatment of a condition in horses called
  roaring (laryngeal hemiplegia).

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Laryngeal Hemiplegia (Roaring) or Laryngeal
paralysis

• Occurs when muscles that tighten cartilage are
  paralyzed.
• At rest usually does not cause a problem
• When animal exercises , may result in obstruction
  of the glottis.
• Surgery may remove ventricle to allow scar tissue
  to tighten cartilage.

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Laryngeal Intubation

• Process in which an endotracheal tube is placed
  through the glottis to the trachea.
• May be helped by the use of a laryngoscope- an
  instrument that helps to hold down epiglottis.
• Laryngospasms sometimes seen in cats, when
  glottis is touched, larynx slams shut. Is reflex.

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Aspiration Pneumonia

• Inflammation of the lungs produced by inhalation
  of a foreign material.
• Use caution when administering liquids to animals
  (remember the swallowing process).
• May see during anesthesia.
• May potentially be fatal.

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Laryngeal Functions

• 1. Voice Production
• Originates at vocal cords in the larynx.
• Vocal cords are attached to arytenoid cartilages
  and stretch across the lumen of the larynx.
• As air passes over vocal cords, they vibrate and
  produce sounds.
• Muscles attached to arytenoid cartilages control
  the tension of the vocal cords.
• Lessening tension of the vocal cords allows for
  lower pitched sounds.
• Tightening of the vocal cords allows for higher
  pitched sounds.

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Laryngeal Functions

• 2. Prevention of Foreign material being inhaled.
• Accomplished by trapdoor action of the
  epiglottis.
• The moving up and down of the adams apple is
  part of this process.
• 3. Control of airflow to and from lungs.
• Partially through epiglottis action when
  swallowing occurs but also through adjustments in
  the size of the glottis.
• Adjustments in the size of the glottis.
• May even be helpful in straining.

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Coughing

• Cough is generated behind a closed glottis.
• Breathing muscles contract, compressing the
  thorax.
• Builds pressure behind the closed glottis.
• When glottis suddenly opens, the forceful release
  of air results in a cough.
• Purpose of coughing is to clear mucus and other
  matter from lower respiratory passages.

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Trachea

• Windpipe- short, wide tube that extends from the
  larynx down through the neck region into the
  thorax.
• Lined with ciliated epithelium.
• Bifurcation of the Trachea- occurs at about the
  level of the heart.

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Trachea

• Structurally, trachea is a tube of fibrous tissue
  and smooth muscle held open by hyaline cartilage
  rings and lined by the same ciliated epithelium
  that is present in the nasal passages.
• Hyaline cartilage rings are C shaped.

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Trachea continued

• Ciliated lining of the trachea is similar to the
  nasal passages.
• The mucous layer on its surface traps tiny
  particles of debris that have made it down this
  far into the respiratory tube.
• Eventually reaches pharynx and is swallowed.

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Collapsing Trachea

• Pushing down of the cartilage area, obstructs air
  flow.
• Causes dry, honking cough.

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Lower Respiratory Tract

• Consists of
• Bronchi
• Bronchioles
• Alveolar ducts
• Alveoli

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Bronchial Tree

• Air passageways that lead from the bronchi to the
  alveoli.
• Divide into smaller and smaller passageways.
• After enters the lung, each main bronchus divide
  into smaller bronchi, which divide into smaller
  bronchi, eventually getting to bronchioles.
• Bronchioles continue to subdivide down to
  alveolar ducts.
• Alveolar ducts end in alveolar sacs.

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Bronchial Tree continued

• Bronchial tree are not just rigid tubes.
• Diameter of each can be adjusted by smooth muscle
  fibers in the wall.
• What kind of smooth muscle is this?
• Autonomic Nervous system controls this smooth
  muscle.
• During times of intense physical activity,
  bronchial smooth muscle relaxes, allowing air
  passageways to dilate to their maximum. Called
  Bronchodilation
• During relaxed time, smooth muscle partially
  contracts, reducing size of air passageway.
  Called Bronchoconstriction.

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Asthma

• Bronchioles are sometimes overly sensitive to
  certain irritants
• Results in bronchoconstriction
• Can range from mild and annoying to
  life-threatening
• More common in humans
• Occurs most commonly in cats in the summer

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Alveoli

• Where external respiration takes place.
• Where oxygen and carbon dioxide are exchanged.
• All respiratory structures exist to move air in
  and out of alveoli.
• Tiny, thin walled sacs surrounded by capillaries.
  
• Walls are composed of simple squamous epithelium.
• These thin layers allow for easy movement of
  oxygen and carbon dioxide.

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Alveoli Continued

• Each alveolus is lined with surfactant a fluid
  that helps reduce surface tension of the fluid.
• This prevents the alveoli from collapsing as air
  moves in and out during breathing.

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Lungs

• Two lungs form a shape like a cone.
• Base of lungs are on the diaphragm.
• Apex of the lung is near the top (pointed like
  area).
• Mediastinum- area between the two lungs, also
  called what??

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Lobes of the Lungs

• Left Lung
• Cranial lobe
• Caudal lobe
• Right Lung
• Cranial lobe
• Middle lobe
• Caudal lobe
• Accessory lobe
• Horse lung is different How?

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Lungs continued

• Hilus- where air, blood, lymph, and nerves enter
  and leave the lung.
• Only area of lung that is fastened in place.

1. Oblique fissure2. Vertebral part3. Hilum of
lung4. Cardiac impression5. Diaphragmatic
surface
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Lungs Continued
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Circulation through the lungs

• Blood supply to and from the lungs is called
  pulmonary circulation
• Blood enters via pulmonary artery
• Blood reenters heart via pulmonary vein

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Consistency of Lungs

• Light and have a spongy consistency
• Fetal lungs have a solid consistency. Why??
• Testing used to determine if a breath was taken.

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Thorax

• Also known as the thoracic cavity chest cavity.
  
• Bound by thoracic vertebrae dorsally, ribs and
  intercostal muscles laterally, and the sternum
  ventrally.
• Contains
• Lungs
• Heart
• Large blood vessels
• Nerves
• Trachea
• Esophagus
• Lymphatic vessels
• Lymph nodes

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Thorax Continued

• Pleura- thin membrane that covers the organs and
  structures in the thorax and lines the inside of
  the thoracic cavity.
• Visceral layer of pleura- covers the thoracic
  organs and structures.
• Parietal layer of pleura- lines the cavity
• Between pleural layers is a lubricating fluid.

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Diaphragm

• Dome shaped.
• Thin sheet of skeletal muscle that forms caudal
  boundary of the thorax.
• When diaphragm contracts, dome flattens out and
  enlarges thorax.
• Helps with inspiration

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Respiration

• Process requires effective movement of air into
  and out of lungs at an appropriate rate and in
  sufficient volume to meet the bodys needs at any
  particular time.
• Pressure within the thorax is negative with
  respect to atmospheric pressure.
• Pulls lungs tight against the thoracic wall
• Flexible nature of lungs allows them to conform
  with shape of the thoracic wall.
• Pleural fluid provides lubrication.
• Lungs follow thoracic wall.

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Respiration continued

• Negative pressure also aids in the return of
  blood to the heart.
• Helps to pull blood into the large veins of the
  mediastinum.
• Helps to draw blood from the midsize veins and
  then dump these into the atria.

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Pneumothorax

• Loss of air into thorax.
• Disrupts the negative pressure.
• Causes can be due to trauma or lung disease.

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Inspiration

• Process of drawing air into the lungs.
• Also called inhalation
• Basic process is enlargement of the volume of the
  thoracic cavity by the inspiratory muscles.
• Main inspiratory muscles
• Diaphragm
• External Intercostal muscles.
• Located in the external portion of the spaces
  between the ribs (intercostal spaces).

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Expiration

• Process of pushing air out of the lungs.
• Also called exhalation.
• Thoracic cavity is decreased in size, compresses
  lungs and pushes air out through the respiratory
  passages.
• Main muscles are the internal intercostal muscles
  and the abdominal muscles.
• How do muscles work??
• Does not require as much work as inspiration

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Respiratory Volumes

• Tidal volume volume of air inspired and expired
  during one breath.
• Varies according to bodys needs.
• Smaller when animal is at rest and larger when
  excited and active.
• Minute volume volume of air inspired and
  expired during one minute.
• Calculated by multiplying the tidal volume by
  breaths per minute.
• Measured in mL or Liters
• Residual volume volume of air remaining in the
  lungs after maximum expiration.
• Residual volume always remains.
• Lungs will never be completely emptied of air.

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Lung volumes continued

• Measured with a spirometer.

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Exchange of Gases in Alveoli

• Simple diffusion process from areas of high
  concentration to areas of low concentration.
• Atmospheric air contains 21 oxygen and 0.03
  carbon dioxide.
• Blood in lungs is high in carbon dioxide and low
  in oxygen.
• Oxygen diffuses from alveolar air to blood,
  carbon dioxide diffuses to alveolus which is
  refreshed with oxygen from next breath.

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Partial Pressure of Gases

• Daltons law- states that the total pressure of a
  mixture of gases is the sum of the pressure of
  each individual gas.
• Partial pressure- the pressure of each individual
  gas.
• Partial pressure is expressed with a P before
  chemical symbol for gas.
• Partial pressures of O2 and CO2 in the blood of
  alveolar capillaries is determined by the partial
  pressures of O2 and CO2 in alveolar air
• the greater the amount of a gas in the air you
  breath, the more concentrated it will be in the
  blood.

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Control of Breathing

• Breathing does not require conscious effort
  although use skeletal muscles that are under
  voluntary control.
• Is controlled by an area in the medulla oblongata
  of the brain stem.
• Known as the respiratory center.
• Houses control systems for inspiration,
  expiration, and breath holding.
• Subconsciously sends nerve impulses to the
  muscles to direct them how to contract.
• Usually can only control breathing consciously
  for a short period of time before autonomic
  system kicks back in.

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Two systems to control breathing

• 1. Mechanical system
• Sets routine inspiration and expiration limits.
• 2. Chemical system
• Monitors that the levels of certain substances in
  the blood and directs adjustments in breathing
  if they get out of balance.

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Mechanical Control

• Operates through stretch receptors in the lungs
  that set limits on routine expiration and
  inspiration.
• When lungs inflate to a certain point, nerve
  impulse says that lungs are full and stops muscle
  contractions that allow lungs to fill.
• Then will notify muscles to contract to start
  expiration

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Chemical Control

• Monitors blood and affects breathing if something
  gets out of balance.
• Monitors
• CO2 content
• The pH
• O2 content
• Blood level of CO2 and blood pH are linked. As
  CO2 rises, pH goes down. If this occurs, chemical
  control system signals to increase rate and depth
  of breathing to even it out.
• Vice versa if pH goes up.

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Chemoreceptors

• Peripheral- aortic bodies and carotid bodies
• Central- found in the medulla of the brain.
• Normal respiratory rates
• 10-30 breaths per minute in dog
• 20-30 breaths per minute in cat.

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Bagging a Patient

• Term used to describe manual control of an
  anesthetized patients breathing by squeezing and
  releasing the rebreathing bag.
• May cause more CO2 than normal to be removed from
  lungs, so may trigger that patient will not
  breathe once bagging stops.
• Hypoxia- Decrease in blood O2.
• If this occurs, chemical control system signals
  the respiratory center to increase rate and depth
  of breathing so more O2 will be taken in.

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Terms

• Sneeze- similar to a cough, but originates in the
  nasal passages, burst of air is directed through
  the nose and mouth in effort to eliminate the
  irritant.
• Yawn- slow, deep breath taken through a wide-open
  mouth. May be stimulated by slight decrease in
  oxygen levels, drowsiness, fatigue, and boredom.
• Sigh- slightly deeper than normal breath. May
  serve to expand lungs more than normal. May hear
  sighing patient under anesthesia.
• Hiccups- spasmodic contractions of the diaphragm
  accompanied by sudden closure of the glottis.
  Usually self-limiting

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• http//www.med.ucla.edu/wilkes/lungintro.htm