Download 3_ Ventilation - Trinity College Dublin

The Respiratory System
Lecture 3: Ventilation
Human form & Function - Physiology 08-09
Mikel Egaña
Trinity College Dublin
Copyright © 2005 Pearson Education, Inc., publishing as Benj amin Cummings.
Lecture Outline
I.
Alveolar minute ventilation
II.
Respiratory diseases:
I.
Obstructive
II.
Restrictive
Physiology 08-09. Respiratory System. Lecture 2.
1
Pulmonary Minute Ventilation
Total volume of air entering and leaving
respiratory system each minute
•
Minute ventilation = VT x RR
•
Normal respiration rate = 12 breaths/min
•
Normal VT = 500 mL
•
Normal minute ventilation =
–
500 mL x 12 breaths/min = 6000 mL/min
Physiology 08-09. Respiratory System. Lecture 2.
Anatomical Dead Space
•
Air in conducting zone does not participate in gas exchange
•
Thus, conducting zone = anatomical dead space (~150 ml)
Expiration:
-500ml expired to atmosp:
-- 350ml old air
--150ml fresh air
--150ml old air in
conducting zone
Inspiration:
--150ml fresh air in
conducting zone
-500ml enter alveoli:
-- 350ml fresh air
--150ml old air
Physiology 08-09. Respiratory System. Lecture 2.
2
Alveolar Ventilation
•More important than pulmonary ventilation
•Volume of air exchanged between the atmosphere and the
alveoli per minute
•Less than pulmonary ventilation due to anatomic dead
space
•
Volume of air in conducting airways that is useless for
exchange
•
Averages about 150 ml in adults
Alveolar ventilation = (tidal volume – dead space) x
respiratory rate = (500-150 mL/br) x 12 br/min =
4200ml/min
Physiology 08-09. Respiratory System. Lecture 2.
Effect of Different Breathing Patterns on Alveolar
Ventilation
Physiology 08-09. Respiratory System. Lecture 2.
3
Airway resistance
Physiology 08-09. Respiratory System. Lecture 2.
Flow-Volume Loop
Physiology 08-09. Respiratory System. Lecture 2.
Berne & Levy, fig 13.14
4
Forced Expired Volumes
•FEV1.0: Force expired volume in 1 sec
•FVC: Forced vital capacity
•FEV1.0/FVC: disease index
Physiology 08-09. Respiratory System. Lecture 2.
Costanzo 3rd Ed., fig 5-6
Respiratory Diseases
•Two main classifications
• Obstructive
–
–
–
–
Airway narrowing
Increased airway resistance
Reduced flow during expiration
Examples:
• Restrictive
–
–
–
–
Reduced compliance
Scar tissue formation
Fibrosis
Examples:
Physiology 08-09. Respiratory System. Lecture 2.
5
Obstructive - I
•
•
•
•
•
Airway hyper-reactivity
Reversible airway narrowing
Mucous thickening
Smooth muscle constriction
Causes
• Allergens, pollens, animal fur, dusts
• Smoking, smog & airborne pollutants
• Changes in air temperature, humidity, pressure
• Exercise
• Emotional stress, anxiety
Physiology 08-09. Respiratory System. Lecture 2.
Obstructive - II
• Irreversible
• Destruction of alveolar walls
• Enlargement of air spaces
• Primarily distal to terminal bronchioles
• Increased lung compliance via
• Destruction of elastic fibres
• Excessive release of enzymes: trypsin
• Reduced elastic recoil of the lung
• Causes
• Smoking induced inflammation
• Cilia destruction, tar accumulation
• Airborne contaminants
• NO TREATMENT!
Physiology 08-09. Respiratory System. Lecture 2.
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Obstructive - III
•Inflammation of airway walls
•Excessive mucous production
•Airway narrowing and coughing
•Reversible and chronic
•Causes
•
Bacterial & viral infections
•
Smoking
•
Airborne pollutants
•
Chronic irritation (eg: miners)
Physiology 08-09. Respiratory System. Lecture 2.
Restrictive – I
•
•
•
•
•
•
•
Diffuse Interstitial Lung Disease (DILL)
Results from over 130 disorders
Reduced elasticity
Reduced compliance of lung and chest wall
Increased work of breathing
Slim patients
Causes
• No known cause in 2/3 of all cases
• Asbestos fibre breathing
• Inflammation
• Scar tissue formation
Physiology 08-09. Respiratory System. Lecture 2.
7
Disease Characteristics
Total Lung Capacity
Residual Volume
Vital Capacity (FVC)
FEV1.0
FEV1.0/FVC
Obstructive
Normal; 6l
" 2.5-3l
! 4l
!! 2-2.5l
! 50%
Restrictive
! 4-5l
Normal; 1.2l
! 3l
! 2.5-3l
" 90-100%
Physiology 08-09. Respiratory System. Lecture 2.
Abnormal Spirograms Associated with Obstructive and
Restrictive Lung Diseases
Physiology 08-09. Respiratory System. Lecture 2.
8
Spirometry I
Physiology 08-09. Respiratory System. Lecture 2.
Netter’
Netter’s Atlas, fig 5.27
Spirometry - II
Physiology 08-09. Respiratory System. Lecture 2.
Netter’
Netter’s Atlas, fig 5.26
9
Disease state Flow-Volume loops
Physiology 08-09. Respiratory System. Lecture 2.
10