Respiratory Physiology

1
Respiratory Physiology

• CHAPTER 17

2
Respiratory Physiology

• 2 components
• Muscle driven pump
• Thin moist exchange surface

3
Respiratory Function

• 1. Exchange of gases between the atmosphere and
  the blood
• 2. Homeostatic regulation of body pH.
• 3. Protection from inhaled pathogens
• 4. Vocalization

4
External Respiration

• 1. Ventilation
• Inspiration
• Expiration
• 2. Gas exchange lungs/blood
• 3. Gas transport
• 4. Gas exchange blood/cells

5
(No Transcript)
6
Respiratory System

• 1. Conducting system Airways
• 2. Exchange surface alveoli
• 3. Physical and Mechanical Support for
  Respiratory pump

7
Fig 17-2b
8
(No Transcript)
9
Fig 17-2g
10
(No Transcript)
11
(No Transcript)
12
Ventilation

• Movement of air between the environment and
  alveoli
• Upper airways
• Warm air
• Humidify
• Filter

13
Fig 17-7a
14
Ventilation

• Air flows into the lungs because of pressure
  gradients created by a pump.
• Flow ? ?P / R
• Respiratory Cycle Inspiration/Expiration

15
Pressures

• Alveolar Pressure
• Intrapleural Pressure

16
(No Transcript)
17
Inspiration

• During inspiration
• Contraction of the diaphragm movement downward
  of 1.5 cm
• 60-75 of inspiratory volume
• 25-40 rib cage moves up and out increasing
  volume-External intercostal scalene muscles

18
Expiration

• Passive expiration
• Elastic recoil of the lungs returns the diaphragm
  and rib cage to original position
• Active expiration internal intercostals and
  abdominal muscles pushes up on diaphragm

19
(No Transcript)
20
(No Transcript)
21
Factors Affecting Pulmonary Ventilation

• 1.) Stretchability or Compliance of the lungs
  (fibrotic lung disease Decreased compliance)
• 2.) Elastance (Elasticity or elastic recoil)
  (emphysema High compliance, low elastance)
• 3.) Resistance of the airways to air flow

22
Compliance

• A. Stretchability Elastin fibers
• Lung compliance DV/ D (Palv Pip)
• A large lung compliance is advantageous because a
  smaller change in transpulmonary pressure is
  needed to bring in a given volume of air,
  therefore less work or muscle contraction is
  required.

23
Compliance

• B.) Surface Tension
• Presence of fluid lining in the lung creates
  surface tension that increases the resistance of
  the lungs to stretch
• Surfactants disrupts cohesive forces between
  water molecules, decreasing surface tension of
  the fluid lining of the alveoli
• Dipalmitoylphosphatidylcholine lipoproteins

24
Surfactant

• Produced and secreted into the alveolar airspace
  by alveolar Type II cells
• Begins week 25 of fetal development in humans
  reaching functional levels at 32 weeks, eight
  weeks before normal delivery
• Respiratory distress syndrome Premature infants
  born before 32 weeks

25
Surfactant

• Increases compliance
• Decreases surface tension in alveoli and prevents
  small alveoli from collapsing, equalizing
  pressure between large and small alveoli

26
Figure 17-13 - Overview
27
Resistance

• 1. Length
• 2. Viscosity of substance
• 3. Radius
• R ? L?/r4

28
Airway Resistance

• 90 due to trachea and bronchi
• Mucus accumulation from allergies and infections
• BronchiolesBronchoconstriction increases
  resistance to air flow and decreases the amount
  of fresh air that reaches the alveoli

29
Smooth muscle in Bronchioles

• Bronchodilation increased carbon dioxide in
  expired air relaxes bronchiolar smooth muscle
• Histamine Paracrine that acts as a
  bronchoconstrictor Allergy-induced asthma
  Atopy
• Parasympathetic neurons Bronchoconstriction to
  protect lower respiratory tract acetylcholine
  on muscarinic receptors
• Sympathetic B2 receptors that respond to
  epinephrine Relaxes airway smooth muscle and
  results in bronchodilationB2 agonist albuterol
  treatment in asthma

30
Pulmonary Function

• Spirometry
• Pulmonary Function Tests

31
(No Transcript)
32
Fig 17-14
33
Total Pulmonary Ventilation

• Minute volume ventilation rate (breaths per
  minute) x tidal volume

34
Alveolar Ventilation

• Ventilation rate x (tidal volume anatomical
  dead space volume) alveolar ventilation
• Anatomical dead space averages 150 mL

35
Table 17-5