Respiratory Physiology

1
Breakdown of Topics in Respiratory Physiology
Ventilation, Gas Exchange, Control of Respiration
Respiratory Physiology
2
Functions of the Respiratory System

• Respiration
• Acid-base balance
• Enabling vocalization
• Defense against pathogens and foreign particles
• Route for water and heat losses

3
General Concepts of Respiration

• Ventilate bring the oxygen to the blood
• Gas exchange diffusion of gasses from alveoli
  into blood then gasses go to/from erythrocytes
  to /from Hemoglobin
• O2 utilization Mitochondria need the oxygen to
  make ATP (cellular respiration)

4
Ventilation

• Ventilation is the process of bringing air into
  and out of the lungs.
• Lungs are the only organs that do not have smooth
  muscle in them. They are just elastic tissue.
• The lungs cannot inflate on their own. They need
  to be tethered to muscles in order to get volume
  changes, which causes pressure changes, which
  regulate air flow.
• There are pressure gradients from the partial
  pressures of gasses. If the partial pressure of a
  gas is increased, the concentration of that gas
  increases, too.
• Your lungs also contain millions of macrophages,
  so they are a good line of defense against
  pathogens. They also get rid of the dust and
  other debris that accumulates in the lungs.
• They are also a route of heat and water loss.
  When you exhale, you lose water vapor and heat.
  90 of the heat lost from your body is from
  exhaling.

5
Gas Exchange

• In the lungs, oxygen moves into the blood, driven
  by pressure gradients, which are similar to
  concentration gradients.
• Oxygen will diffuse down its concentration
  gradient (from the lungs, into the plasma, and
  into the cells) while CO2 moves down its
  concentration gradient (from the cells, into the
  plasma, and into the lungs).
• These two gas exchanges are called external
  respiration.

6
Oxygen Utilization

• When oxygen enters the cells, some of it enters
  the mitochondria, which uses oxygen as an
  electron acceptor (the mitochondria places
  hydrogen ions on the oxygen and turns it into
  water). This excess water leaves the cell and
  enters the tissues.
• The removal of oxygen from the plasma and the
  addition of water in the tissues creates a
  driving force (known as the Starling principle)
  to continuously draw oxygen into the tissues,
  since the water in the tissues has diluted the
  number of particles there, and oxygen, as a
  particle, will be sucked into the tissues.
• The gas exchange that occurs at the tissue
  capillary beds is called internal respiration.
• The actual use of oxygen as a final electron
  acceptor(during a process called oxidative
  phosphorylation) is called cellular respiration.

7
General Concepts Airway Anatomy
Surface area 70 sq meters- each lung (size of a
large lecture hall)! Barrier/ thickness to
diffusion 0.2 microns
8
Carbon Monoxide

• This is an odorless, colorless gas from
  incomplete burning of fuels.
• Carbon monoxide binds to hemoglobin 200x more
  strongly than oxygen, so it drives the O2 from
  the hemoglobin, and attaches in its place and
  stays there. Carbon monoxide decreases the amount
  of oxygen that can be transported by hemoglobin
• The person dies from suffocation it makes the
  lips cherry red.
• Cyanide poisoning kills in the same way, but the
  lips are blue (cyanosis).

9
CO2 Transport

• When oxygen is on the hemoglobin molecule, it is
  called oxyhemoglobin.
• Dissociation of oxyhemoglobin is when the oxygen
  is released and enters the tissues.
• This dissociation increases as the pCO2 levels
  increase.
• In other words, when the carbon dioxide levels
  rise, oxygen will jump off the hemoglobin and
  into the tissues. Therefore, the most effective
  stimulus to the respiratory center is an increase
  in pCO2.
• The waste product of cellular respiration is
  carbon dioxide.
• CO2 will then attach onto the hemoglobin and be
  taken to the lungs to be expelled.

10
CO2 Transport

• CO2 is carried to the lungs on the hemoglobin,
  after the oxygen has left to enter the tissues.
• The carbon dioxide reacts with water in the RBC
  to form carbonic acid, which then breaks apart
  into a hydrogen ion (which lowers blood pH) and a
  bicarbonate ion (which raises blood pH).
• CO2 H2O ? H2CO3 ? H
  HCO3-
• This reaction is reversible, and would go mainly
  to the right in the tissues and to the left in
  the lungs.
• CO2 is transported in the blood predominately in
  the form of bicarbonate.
• The number of H ions in the blood depends partly
  on the amount of CO2 in the blood. The more CO2
  in the blood, the more H in the blood, which
  makes the blood acidic. If the blood is too
  acidic, bicarbonate ions are absorbed to raise
  the pH. If the blood is to alkaline, bicarbonate
  ions are excreted by the kidneys.

11
Respiratory System Contribution to pH Balance in
the Blood

• If a person has excess H ions in the blood
  (acidosis), they will breathe more rapidly.
• If the person has an airway obstruction (such as
  asthma), they cannot exhale the excess CO2.
• Because the H are building up, the carbonic acid
  will also build up, causing a drop in pH
  (acidosis) in the blood.
• Enzymes in the body cannot work outside of their
  optimal pH range, so chemical reactions come to a
  halt.
• Hyperventilation results in too little CO2 in the
  blood, so the person has a high pH (alkalosis),
  which also denatures enzymes.

12
Control of Respiration

• Changes in lung volume, and thus ventilation, are
  dependent upon the change in thoracic cavity
  volume.
• Alterations in the space inside the thoracic
  cavity are the result mainly of the contraction
  of the diaphragm, intercostal muscles.
• These muscles are innervated by neurons in the
  respiratory centers of the brain stem (medulla
  and pons).

13
Respiratory Centers Medulla oblongata and Pons

• Pons (Pneumotaxic Center)
• decreases respiratory rate
• Medulla
• Dorsal respiratory group
• Increases inspiration rate
• Ventral Respiratory Group
• Inactive during quiet respiration
• Active during forced respiration

Figure 41-1 Guyton Hall
14
Chemoreceptors

• Carbon Dioxide, Hydrogen Ions
• Central chemosensitive area of medulla senses
  levels of CO2 and H in CSF (both are acids)
• Oxygen
• Peripheral chemoreceptors sense oxygen levels in
  blood
• Aortic chemoreceptors (CN X)?
• Carotid chemoreceptors (CN IX)?

15
Respiratory Chemoreceptors

• In the cardiovascular lecture, we learned about
  baroreceptors detecting blood pressure in the
  aortic arch and carotid sinus.
• The respiratory system has chemoreceptors in
  those areas, too. They function to detect the O2,
  CO2, and pH levels of the blood.
• The medulla oblongata also has chemoreceptors
  that monitor pH. This information is sent to the
  other parts of the respiratory centers (pons and
  other areas in the medulla oblongata) to allow
  them to alter breathing rate to maintain proper
  blood pH.

16
Control of Respiration

• Relaxed breathing only requires the diaphragm to
  contract for inspiration, and for the diaphragm
  to relax for expiration.
• Forced breathing requires the diaphragm plus
  muscles that raise and lower the ribs (external
  intercostals for inspiration, internal
  intercostals for expiration).
• The respiratory centers are most sensitive to the
  level of CO2 in the blood, rather than the levels
  of oxygen.

17
Control of Gas at Cellular Level

• The flow of blood through capillaries is
  controlled by sphincters on the arterioles and
  capillary beds to adjust the amount of blood
  flowing to particular tissues.
• Cells and tissues that are undergoing increased
  aerobic activity have less oxygen and more CO2,
  lower pH, and increased temperature.
• When CO2 levels in the tissues are too high, the
  smooth muscle sphincters relax to allow more
  blood flow to increase gas exchange.

18
Ventilation
Inspiration (inhalation) Expiration (exhalation)
Normal inhalation, normal exhalation Forced
inhalation, forced exhalation

• Concepts
• Pressure gradient created by volume changes
  (Boyles Law)
• Anatomy of lung and chest wall

19
Inhalation and Exhalation vs. Force

• Ventilation requires ATP during inhalation, but
  normal exhalation does not require ATP.
• Some people with respiratory problems need to
  work at exhalation as well by using skeletal
  muscle, and this means that they need to use more
  ATP. Lungs are not muscular structures. They
  need the skeletal muscles in the thoracic cage to
  change the thoracic volume, which changes the
  pressure gradients.
• Air flows from high pressure to low pressure.

20

• Boyle's Law P1V1P2V2
• Pressure and volume are inversely related (if
  other variables are kept constant.)

Boyles Law assumes normal circumstances, not a
person who is in high altitude or who has
variation in body temperature.
21
Air Pressure in Lungs

• Every time a molecule strikes the wall of a
  container, it causes pressure. In a larger
  container with fewer molecules, it takes a while
  to strike the wall randomly, so there is less
  pressure.
• The number of impacts on a container wall is the
  pressure.
• The lungs must have a volume change to create a
  pressure change, which is required to have air
  move into and out of the lungs.

22
Air Pressure in Lungs

• The diaphragm is the muscle that mostly
  contributes to the volume change. When it
  contracts, it pulls downward, and the volume of
  the thoracic cavity increases.
• The external intercostals elevates the ribcage,
  giving the lungs more room, so they also increase
  the lung volume.
• Those two muscles cause increased volume.

23
Air Pressure in Lungs

• Because the lungs are tethered to the thoracic
  cavity, when your chest wall expands, your lungs
  expand with it. The lungs are stuck to the chest
  wall because the serous fluid in the pleural
  cavity makes the lungs stick to the chest wall
  like two pieces of wet glass stuck together.
• When the lungs expand, their volume expands. That
  means there is less pressure in the lungs than
  there is in the outside air. Since air moves from
  high to low pressure, air flows into the lungs.
• As air flows in, the alveoli expand, so the
  volume in each air sac expands, so the pressure
  in the alveoli lowers. Air in the conducting
  passages (bronchi) is at higher pressure, so it
  will move from high to low pressure areas.
  Therefore, air will move into the alveoli.

24
Air Pressure in Lungs

• Air has weight atmospheric pressure is 760 mmHg
  at sea level (much less weight and pressure at
  high altitudes).
• Since air will flow from higher pressure to lower
  pressure areas, to get the air to flow into our
  lungs, we need to have a lower pressure in our
  lungs.
• We can decrease the pressure in our lungs by
  expanding the volume. As we expand the volume of
  our thoracic cavity (taking a breath), the
  pressure in the lungs drops, and air flows into
  the lungs.
• It is a small pressure difference, but it is
  enough to get 500 ml of air to come into your
  lungs.
• At higher altitudes, even though the amount of
  oxygen is the same (21) there is less air
  pressure. At 8,000 feet in elevation, there is ¼
  less pressure. This makes it harder to breathe.
• When you exhale, you simply relax the muscles,
  and if the lungs are not being pulled open any
  more, the elastic tissue there will recoil,
  making the lung volume smaller, so the pressure
  there increases.

25
Lung Compliance

• Lung Compliance is how much the lung volume
  changes when the pressure changes.
• Compliance can be considered the opposite of
  stiffness.
• A low lung compliance (increase in stiffness)
  would mean that the lungs would need a greater
  than average change in pressure to change the
  volume of the lungs. Instead of needing only 10
  mmHg pressure difference between the outside air
  and the lungs, would now need a 20 mm difference.
• A high lung compliance would indicate that little
  pressure difference is needed to change the
  volume of the lungs.
• More energy is required to breathe in a person
  with low lung compliance. Persons with low lung
  compliance due to disease therefore tend to take
  shallow breaths and breathe more frequently.

26
Gases move down pressure gradients
P atm 760 torr
Flow Rule Patm Palv Resistance
How are the pressure gradients changed? According
to Boyles law we will need to create volume
changes! PROBLEM! THE LUNGS ARE NOT MUSCULAR
STRUCTURES!
p alveolar 758 torr
Air moves from high to low pressure
27
Air Pressure in Lungs

• We are looking at two types of air pressures
  atmospheric pressure, and the pressure of air
  deep in the lungs, called the alveolar
  (pulmonary) pressure.
• As long as there is a difference in pressure
  between these two, there will be a pressure
  gradient, and air will flow.
• If they equal each other (such as during a
  punctured lung, called a pneumothorax), air will
  not flow.

28
Air Pressure in Lungs

• Take a breath in and stop. Enough air has come in
  now so that the air pressure in the alveoli
  equals the atmosphere, so you no longer get more
  air flowing in.
• When you relax, the lungs recoil, air comes out,
  and when the two pressures equal each other, air
  stops flowing out.
• You will get zero pressure differences upon
  maximum inhalation and exhalation.

29
Oxygen-Hbg Dissociation Curve

• X-axis is partial pressure of oxygen (pO2)
• Y-axis is saturation of Hgb with O2
• The partial pressures of respiratory gases found
  in arterial blood correspond most closely to
  those partial pressures found in the alveoli.

30
Oxygen-Hbg Dissociation Curve

• Hgb in the blood leaving the lungs is about 98
  saturated with O2.
• This graph demonstrates that 98 of Hbg is still
  saturated when pO2 is only 70 mm (when it first
  arrives in the tissues).
• By the time pO2 reaches 100mm (in the lungs), Hbg
  is already 100 saturated.

31
Significance

• In the lungs, pO2 is 100 mm Hg. Hemoglobin is
  still 100 saturated at this pO2 level.
• In the body cells, pO2 is 40 mm Hg. Hemoglobin is
  still about 75 saturated at this low pO2 level.
• The difference of 25 saturation means that
  hemoglobin gives up only about 25 of its O2 to
  body cells as it passes by.

32
Left shift
CAUSE pH increased CO2 decreased Temperature
decreased
33
Right shift
CAUSE pH decreased CO2 increased Prostaglandin
release (fever)
34
Shifts

• A left shift will increase oxygen's affinity for
  hemoglobin.
• In a left shift condition (alkalosis or
  hypothermia) oxygen will have a higher affinity
  for hemoglobin (it wont leave!).
• This can result in tissue hypoxia even when there
  is sufficient oxygen in the blood.
• A right shift decreases oxygen's affinity for
  hemoglobin.
• In a right shift (acidosis or fever) oxygen has a
  lower affinity for hemoglobin. Blood will release
  oxygen more readily.
• This means more O2 will be released to the cells,
  but it also means less oxygen will be carried
  from the lungs in the first place.

35
Vacuum in Lungs

• There is another anatomical structure you need to
  remember the plural cavity. Each lung is
  surrounded by a parietal and visceral serousal
  membrane.
• The serousal cells make a lubricating fluid so
  the lungs dont rub against the thoracic cavity,
  causing heat generation, which can denature
  proteins.
• This fluid has cohesive properties. If you put
  two pieces of wet glass together, you have to use
  more force to pull them apart than if they were
  dry. You have to break the vacuum.

36
Vacuum in Lungs

• The surface of the lungs are tightly stuck to the
  surface of the thoracic wall.
• If they are disengaged, they will recoil like
  deflated balloons.
• If the vacuum in the pleural cavity is broken,
  the lung will collapse.
• They need to be reinflated by the administration
  of oxygen.

37
Mechanics of Ventilation

• Normal Inspiration
• Is an active process (Its work! It uses ATP)
• Contract Diaphragm and it moves inferiorly to
  increase thoracic volume -60-75 of volume change
• Contract external intercostals

• Forced Inspiration
• Accessory muscles needed
• Sternocleidomastoid
• Scalenes
• Serratus anterior
• Others (erector spinae)

38
When the chest wall moves, so do the lungs! Why
are the lungs right up against the chest wall?

• Pleural Space or Cavity
• a vacuum (contains no air)
• pleural fluid (water) has surface tension

Result? Lung moves with the chest wall
Lungs are not muscular organs, they cannot
actively move. They move with the chest wall.
39
What happens if the lung dissociates from the
chest wall?

• Pneumothorax air in the pleural cavity
• Hemothorax blood in the pleural cavity
• How?
• Injury (Gun shot, stabbing)
• Spontaneous (tissue erosion, disease lung)
• Bleeding wound
• Chest wall recoils outward (barrel chest)
• Lung recoils inward (atelectasis alveolar, lung
  collapse)

40
Mechanics of Ventilation

• Normal Expiration-
• A Passive process
• Simply relax the muscles of inspiration
• Rely on the elastic properties of lung (like a
  balloon deflating on its own)
• Forced Expiration
• Relax muscles of inhalation AND
• Contract internal intercostals
• Contract Abdominal muscles
• Internal and external obliques
• Transverse abdominis
• Rectus abdominis

41
Emphysema

• COPD (chronic obstructive pulmonary disease) is
  emphysema plus chronic bronchitis.
• Emphysema is generally caused by smoking.
• The alveoli have broken, leaving spaces where gas
  exchange cannot take place.
• Compliance decreases, so It is difficult to expel
  the air in the lungs.
• Each inhalation is a forced inspiration also.
• When the ribs are continually raised with each
  breath, they eventually remain in the upright
  position, causing a barrel chest.

42
Exhalation Problem COPD

• Normal exhalation is passive, requires no ATP.
  But forced expiration (such as emphysema patient)
  recruits abdominal muscles. The muscles enlarge
  with time, creating a barrel-shaped chest,
  typical of emphysema patients and COPD.

43
COPD

• In everyone, the midsized bronchioles do not have
  cartilage rings to hold them open, and during
  exhalation, the sides of the bronchioles collapse
  and touch each other.
• If there is not enough surfactant, they stick to
  each other with greater strength (like two wet
  pieces of glass), and the person has to
  forcefully exhale with each breath to overcome
  the cohesiveness of the fluid.
• Surfactant is like adding soap to the fluid so
  the surfaces come apart easier.

44
Exhalation

• Giving oxygen in high concentration helps get air
  into their lungs, but it reduces the drive for
  them to breathe. CO2 is a powerful driving force
  for ventilation. When a person has COPD, they
  have less CO2, and oxygen becomes the driving
  force.
• If we give them oxygen, the drive for them to
  breathe becomes diminished. They eventually wind
  up on a positive pressure ventilator, but the
  disease progresses, and they die from
  suffocation.
• A continuous positive airway pressure machine is
  called a CPAP machine.

45
CPAP Machine
46
Both the Lung and Chest Wall are Elastic

• Both lung and chest wall have the tendency to
  recoil
• What is recoil? Tendency to snap back to resting
  position
• (like a stretched rubber band recoils when
  youlet go of one end)

The chest wall recoils outward (springs out) The
lung recoils inward (ie. it collapses!)
47

• Increase in lung volume decreases intra-alveolar
  pressure (we now have a pressure gradient) air
  goes in.
• Decrease in lung volume raises intra-alveolar
  pressure above atmosphere air goes out.

When the pressure at the alveoli are at 0 (no
difference between their pressure and atmospheric
pressure), no air flows in or out of the lungs.
48
Pressures
Patm and Palv create the pressure gradient that
drives ventilation

• Atmospheric Pressures (Patm)- pressure of the
  outside air (760mmHg760 torr 1 atm).
• Intra-alveolar pressure (Palv) pressure within
  the alveoli of the lungs. Equal to Patm (0mmHg)
  at rest, but varies during phases of ventilation.
• Intra-pleural pressure (Pip) pressure in the
  intra-pleural space.
• Pressure is negative because of the lack of air
  in the intrapleural space, lymph drainage, and
  opposing forces of lung and chest wall.

49
Air Flow

• If atmospheric pressure is greater than alveolar
  pressure, air flows into the lungs.
• If atmospheric pressure is less than alveolar
  pressure, air flows out of the lungs.
• Transpulmonary pressure is the difference between
  the alveolar and intra-pleural pressures.

50
Positive Pressure breathing
Negative Pressure breathing
51
Iron Lung

• This chamber is an iron lung, invented for polio
  patients, whose respiratory nerves were
  paralyzed. When we are normally breathing, we are
  changing thoracic volume, so we are using
  negative pressure breathing. But a paralyzed
  person cannot move their respiratory muscles.
• It works like a reverse vacuum. There is less air
  pressure in the tank, so there is less pressure
  on the chest, so the chest recoils more, to help
  get air in. The vacuum then reverses, increases
  pressure on the chest, air flows out.

52
Acute Mountain Sickness(Altitude Sickness)

• When you visit someone in a high elevation (5,000
  m) you might get acute mountain sickness.
• Symptoms
• Severe headache, fatigue, dizziness, palpitation
  and nausea.
• Cause
• Pulmonary edema.
• Why do you get pulmonary edema?
• High elevations have lower pO2 levels.
• This causes hypoxia (lack of oxygen) in the
  pulmonary capillaries
• This causes increased pulmonary arterial and
  capillary pressures (pulmonary hypertension)
• That causes the pulmonary edema

53
Respiratory Cycle
54
Ventilation Volume

• When you breathe in, you inhale about 500 ml. You
  exhale about 500 ml. Therefore, 500 ml is your
  TIDAL VOLUME.
• Not all 500 ml gets down deep to your alveoli.
  About 150 ml of it stays in the conductive zone
  (bronchi and trachea). About 350 ml reaches the
  alveoli. That is considered your alveolar
  ventilation volume.
• That is the amount of air that can undergo gas
  exchange. If you want to calculate how much air
  moves in and out per minute, take the tidal
  volume and multiply it by breathing rate (about
  12 breaths per minute for adult, 20 for
  children).
• 500 x 12 total ventilation
•  
• Tidal volume 150 x 12 alveolar ventilation

55
Lung function tests

• Lung volumes are assessed by spirometry.
• Subject breathes into a closed system in which
  air is trapped within a bell floating in H20.
• The bell moves up when the subject exhales and
  down when the subject inhales.

• Spirometry
• Static lung tests
• Volumes and capacities
• No element of time involved, ie. How long does it
  take you to push the air out? Normal expiration
  takes 2-3 x longer than inspiration
• Dynamic lung tests
• Time element, rate of exhale
• How much, how quickly?

56
Spirometry measures lung volumes

• The tidal volume, vital capacity, inspiratory
  capacity and expiratory reserve volume can be
  measured directly with a spirometer.
• Most air (80) is exhaled during the first second
  of exhalation. You take a maximum inhale, then a
  maximum exhale (vital capacity). The pen moves
  down the paper, showing time.
• You can calculate how much air you blew out
  (vital capacity), and the amount of air you blew
  out in one second (expiratory reserve volume in
  one second).
• Expiratory reserve volume divided by vital
  capacity should be 80. If you are less than 80,
  it is suggestive of an obstructive pulmonary
  disorder.

57
Dynamic Lung Tests
ERV
VC
ERV/VC 80
Someone with COPD takes longer than one second
to exhale 80.
ERV
ERV/VC 47
VC
58
Obstructive Lung Diseases

• Obstructive lung diseases are characterized by
  inflamed and easily collapsible airways,
  obstruction to airflow, and frequent
  hospitalizations. 
• Examples
• Asthma
• Bronchitis
• Chronic obstructive pulmonary disease (COPD)

59
Restrictive Lung Diseases

• These are extrapulmonary or pleural respiratory
  diseases that restrict lung expansion, resulting
  in a decreased lung volume (rapid, shallow
  breathing), an increased work of breathing, and
  inadequate ventilation and/or oxygenation.
  Decreased vital capacity.
• Cystic Fibrosis
• Infant Respiratory Distress Syndrome
• Weak respiratory muscles
• Pneumothorax

60
Capacities are two or more volumes added together
61
Capacities are two or more volumes added together
These are measured with a
spirometer This is estimated, based on
height and age These are
calculated FRC ERV RV TLC
RV ERV TV IRV
62
Quiz yourself (color version)
1
3
8
9
10
4
7
5
2
6
63
Quiz yourself (what the test will look like)
1
3
8
9
10
4
7
5
2
6
64

• You dont need to memorize the normal numbers,
  just the definitions
• Respiratory Cycle A single cycle of inhalation
  and exhalation
• Respiratory rate number of breaths per minute
  (usually about 12-18 children higher 18-20).
• Tidal Volume normal breath in and out. Usually
  about 500 ml.
• Inspiratory Reserve Volume take in a normal
  breath, stop, now inhale as much more as you can.
  In other words, this is the amount of air that
  can be forcefully inhaled after a normal
  inhalation.
• Expiratory Reserve Volume (Expiratory capacity)
  take a normal breath in, a normal breath out,
  then breathe out the most you can. In other
  words, this is the amount of air that can be
  forcefully exhaled after a normal exhalation.
  This is the air needed to perform the Heimlich
  maneuver. The maneuver decreases the thoracic
  cavity volume, causing increased pressure in
  lungs. That causes forced air with high pressure
  to be expelled from the lungs.
• Residual volume The amount of air left in your
  lungs after you exhale maximally. This air helps
  to keep the alveoli open and prevent lung
  collapse. This is estimated based on height and
  age.

65
Capacities are two or more volumes added together
66

• You dont need to memorize the normal numbers,
  just the definitions
• Vital capacity The volume of air a patient can
  exhale maximally after a forced inspiration.
  Maximum deep breath in, then exhale as much as
  possible. Vital capacity divided by expiratory
  reserve volume should be 80. If it is lower than
  that, the person has either obstructive or
  restrictive lung disease. To tell which one, look
  at VC. If it is normal, it is obstructive. If it
  is low, they have restrictive lung disease.
• Total Lung Capacity (TLC) the sum of all lung
  volumes
• Inspiratory Capacity amount of air for a deep
  breath in after normal exhalation
• Functional residual capacity amount of air left
  in your lungs after a normal exhale. You have to
  calculate this
• FRC ERV residual volume.
• In COPD, their FRC increases.
• They have a barrel chest
• The lungs dont have as much recoil, have
  decreased tidal volume, cannot exhale enough

67
Capacities are two or more volumes added together
68

• You dont need to memorize the normal numbers,
  just the definitions
• Dead Space Area where air fills the passageways
  and never contributes to gas exchange. Amounts to
  about 150 ml.
• Minute Respiratory Volume (MRV) tidal volume x
  respiratory rate. This calculation does not take
  into account the volume of air wasted in the dead
  space. A more accurate measurement of respiratory
  efficiency is alveolar ventilation rate.
• Alveolar Ventilation Rate (AVR)
• AVR (TV Dead Space) x Respiratory Rate

Summary of lung calculations
FRC ERV RV TLC RV ERV TV
IRV MRV TV x RR AVR (TV
Dead Space) x RR
You DO need to know these formulas.
69
Lung Capacity and Disease Summary

• Obstructive Disease
• Normal VC
• Increased TLC, RV, FRC.
• VC/ERV is less than 80

• Restrictive Disease
• Decreased VC
• Decreased TLC, RV, FRC
• VC/ERV less than 80

FRC ERV RV. Why is this important? Its the
volume of air in your lungs at the end of a
normal exhale. It represents the normal
equilibrium position of your chest wall trying to
spring out and lung to recoil, but forced
together due to pleural cavity.
70
Sample Questions

• Minute Respiratory Rate is the volume of air that
  enters the airways (passes the lips) each min.
• MRV Tidal volume x rate of breathing
• (500 ml/breath) x 12 breaths/min
• 6,000 ml/min
• Alveolar ventilation rate is the volume of air
  that fills all the lungs respiratory airways
  (alveoli) each min. In a normal, healthy lung,
  this might be
• AVR (tidal volume dead space volume) x rate
  of breathing
• (500 ml/breath 150 ml) x 12
  breaths/min
• (350 ml/breath) x 12 breath/ min
• 4, 200 ml/min
• In a diseased, poorly perfused lung, this value
  may well be much lower.
• Then, is panting an example of hyper, normal, or
  hypoventilation????

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Hyper and Hypo Ventilation

• The deeper regions of your lungs get more blood
  flow and the upper regions have more air flow.
• If you hyperventilate, the rate and depth of
  ventilations increases, so more air gets to
  alveoli. After voluntary hyperventilation, apnea
  (no breathing) may occur b/c the arterial blood
  contains less carbon dioxide
• Hypoventilation is dealing only with conductive
  zone. When you pant, you are just shifting air in
  the conducting zone. You are not increasing air
  to the alveoli. Panting is hypoventilation.

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Respiratory vs. Metabolic Acidosis and Alkalosis

• RESPIRATORY ACIDOSIS AND ALKALOSIS is abnormal
  blood pH which is caused by abnormal breathing
  rates. It is not necessarily a disease, since
  hyperventilating from stress is not a disease.
• Respiratory alkalosis is caused by
  hyperventilation. This increases the amount of
  CO2 that you are exhaling. CO2 is an acid, so if
  you hyperventilate, you are exhaling a lot of
  acid, so your blood plasma pH will increase
  (alkalosis)
• Respiratory acidosis is caused by
  hypoventilation. This decreases the amount of CO2
  that you are exhaling. If you hypoventilate, you
  are not exhaling enough acid, so your blood
  plasma pH will decrease (acidosis). Respiratory
  acidosis can also be caused by interference with
  respiratory muscles by disease, drugs, toxins.
• METABOLIC ACIDOSIS AND ALKALOSIS is abnormal
  blood pH which is not caused by abnormal
  breathing rate.
• Metabolic acidosis can be caused by
• Salicylate (aspirin) overdose
• Untreated diabetes mellitus (leading to
  ketoacidosis)
• Metabolic alkalosis can be caused by
• excessive vomiting (loss of acid from stomach)

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Compensations for Respiratory vs. Metabolic
Acidosis and Alkalosis

• Respiratory alkalosis can be compensated by
• excreting an alkaline urine (kidneys excrete
  more bicarbonate)
• Cannot hypoventilate since hyperventilation is
  the problem in the first place!
• Respiratory acidosis can be compensated by
• excreting an acidic urine (kidneys excrete more
  H)
• Cannot hyperentilate since hypoventilation is the
  problem in the first place!
• Metabolic acidosis can be compensated by
• excreting an acidic urine
• hyperventilation
• Metabolic alkalosis can be compensated by
• Excreting an alkaline urine
• Hypoventilation

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Acid-Base Conditions

• Excessive diarrhea
• Causes the problem of low HCO3
  (bicarbonate)
• Leads to ?pH in blood (acidosis)
• Lungs Compensate by
• ?pCO2 (hyperventilation, which decreases the
  CO2
• content in the blood,
  thereby removing acid
• from the blood)

75
Acid-Base Conditions

• Ingesting excessive stomach antacids
• Causes the problem of high HCO3
  (bicarbonate)
• Leads to ?pH in blood (alkalosis)
• Lungs Compensate by
• ?pCO2 (hypoventilation, which increases the CO2
  
• content in the blood,
  thereby adding acid
• from the blood)

76
Acid-Base Conditions

• Aspirin overdose
• Causes the problem of high acid, low
  HCO3 (bicarbonate)
• Leads to ?pH in blood (acidosis)
• Lungs Compensate by
• ?pCO2 (hyperventilation, which decreases the
  CO2
• content in the blood,
  thereby removing acid
• from the blood)

77
Acid-Base Conditions

• Anxiety or hysteria with panting
  (hypoventilation)
• The patient hypoventilates
• Causes the problem of high pCO2
• Leads to ? pH in blood (acidosis)
• Lungs Compensate by
• ? HCO3 (by hyperventilation, which decreases
  the CO2
• content in the blood,
  thereby removing acid
• from the blood)

78
Pulmonary Embolism

• Pulmonary Embolism blockage of the pulmonary
  artery (or one of its branches) by a blood clot,
  fat, air or clumped tumor cells. The most common
  form of pulmonary embolism is a thromboembolism,
  which occurs when a blood clot, generally in a
  vein, becomes dislodged from its site of
  formation, travels to the heart, goes into a
  pulmonary artery, and becomes lodged in the
  smaller artery in the lungs, blocking blood flow
  and oxygen to that region of the lung.
• Symptoms may include difficulty breathing, pain
  during breathing, and possibly death. Treatment
  is with anticoagulant medication.