Respiratory phys online

BREATHING

Copyright © 2011 Pearson Education, Inc.

Mechanics of Breathing
Pulmonary ventilation has two phases:
1. Inspiration - gases flow into the lungs
2. Expiration - gases exit the lungs

Boyle’s Law
P1V1 = P2V2
Pressure and volume are inversely proportional


Pulmonary Ventilation
• Inspiration and expiration
• Depend on volume change
• Volume changes → pressure changes
• Pressure changes → gases flow


Pressure in the Thorax
• Atmospheric pressure (Patm)
• Outside pressure
• = ~1 atm
• Negative respiratory pressure < Patm
• Positive respiratory pressure > Patm
• Zero respiratory pressure = Patm


Alveolar Surface Tension
• Surfactant
• Detergent-like complex produced by alveolar
cells
• Helps keep lungs from collapsing.
• Insufficient quantity in premature infants
causes infant respiratory distress syndrome


Pressure Problems
• Atelectasis (lung collapse):
• Plugged bronchioles → collapse of alveoli
• pneumonia
• Chest wound
• Pneumothorax - air into pleural cavity


Muscles of Breathing
• Diaphragm – main muscle
• Produces large changes in lung volume

• External intercostals – lift ribs
• Internal intercostals – forces exhalation
• Abdominals - expiration


Inspiration
• An active process
• Inspiratory muscles contract
• Thoracic volume increases
• Pressure in the lungs decreases
• Air flows into the lungs, until Ppul = Patm


Sequence of events

Changes in anteriorposterior and superiorinferior dimensions

Changes in lateral
dimensions
(superior view)

1 Inspiratory muscles

contract (diaphragm
descends; rib cage rises).
2 Thoracic cavity volume

increases.

Ribs are elevated
and sternum flares
as external
intercostals
contract.
External
intercostals
contract.

3 Lungs are stretched;

intrapulmonary volume
increases.

4 Intrapulmonary pressure

drops (to –1 mm Hg).

5 Air (gases) flows into

lungs down its pressure
gradient until intrapulmonary
pressure is 0 (equal to
atmospheric pressure).


Diaphragm
moves inferiorly
during contraction.

Figure 21.13 (1 of 2)

Expiration
• Expiration is a passive process
• Inspiratory muscles relax
• Thoracic cavity volume decreases
• Pressure increases
• Air flows out of the lungs until Ppul = 0


Expiration

• Forced expiration is an active process
• abdominal and internal intercostal muscles
contract
• Decreases in pulmonary volume
• Increase in pulmonary pressure

• Forces air out


Sequence
of events
1 Inspiratory muscles

relax (diaphragm rises; rib
cage descends due to
recoil of costal cartilages).
2 Thoracic cavity volume

decreases.

Changes in anteriorposterior and superiorinferior dimensions

Changes in
lateral dimensions
(superior view)

Ribs and sternum
are depressed
as external
intercostals
relax.

3 Elastic lungs recoil

External
intercostals
relax.

passively; intrapulmonary
volume decreases.
4 Intrapulmonary pres-

sure rises (to +1 mm Hg).
5 Air (gases) flows out of

lungs down its pressure
gradient until intrapulmonary pressure is 0.


Diaphragm
moves
superiorly
as it relaxes.

Figure 21.13 (2 of 2)

Intrapulmonary
pressure. Pressure
inside lung decreases as
lung volume increases
during inspiration;
pressure increases
during expiration.
Intrapleural pressure.
Pleural cavity pressure
becomes more negative
as chest wall expands
during inspiration.
Returns to initial value
as chest wall recoils.
Volume of breath.
During each breath, the
pressure gradients move
0.5 liter of air into and out
of the lungs.

Inspiration Expiration
Intrapulmonary
pressure

Transpulmonary
pressure

Intrapleural
pressure

Volume of breath

5 seconds elapsed


Figure 21.14

Respiratory Volumes
• Tidal volume (TV)
• Normal air exchange

• Inspiratory reserve volume (IRV)
• Forced air in

• Expiratory reserve volume (ERV)
• Forced exhale

• Residual volume (RV)
• Air needed to maintain lungs

Respiratory Volumes

Measurement

Adult male
average value

Adult female
average value

Tidal volume (TV)

500 ml

Inspiratory reserve
volume (IRV)

3100 ml

1900 ml

Expiratory reserve
volume (ERV)

1200 ml

700 ml

Residual volume (RV)

Respiratory
volumes

500 ml

1200 ml

1100 ml


Description
Amount of air inhaled or
exhaled with each breath
under resting conditions
Amount of air that can be
forcefully inhaled after a normal tidal volume inhalation
Amount of air that can be
forcefully exhaled after a normal tidal volume exhalation
Amount of air remaining in
the lungs after a forced
exhalation

Figure 21.16b

Respiratory Capacities
• Two or more volumes:
• Inspiratory capacity (IC)
• IRV + TV

• Functional residual capacity (FRC)
• ERV + RV

• Vital capacity (VC)
• IRV + TV + ERV

• Total lung capacity (TLC)
• IRV + TV + ERV + RV


Respiratory Capacities

Total lung capacity (TLC)

4200 ml

Vital capacity (VC)

4800 ml

3100 ml

Inspiratory capacity (IC)

3600 ml

2400 ml

Functional residual
capacity (FRC)

Respiratory
capacities

6000 ml

2400 ml

1800 ml

Maximum amount of air
contained in lungs after a
maximum inspiratory effort:
TLC = TV + IRV + ERV + RV
Maximum amount of air that
can be expired after a maximum inspiratory effort:
VC = TV + IRV + ERV
Maximum amount of air that
can be inspired after a normal
expiration: IC = TV + IRV
Volume of air remaining in
the lungs after a normal tidal
volume expiration:
FRC = ERV + RV

(b) Summary of respiratory volumes and capacities for males and females


Figure 21.16b

Respiratory Volumes and Capacities

Inspiratory
reserve volume
3100 ml

Tidal volume 500 ml
Expiratory
reserve volume
1200 ml
Residual volume
1200 ml

Inspiratory
capacity
3600 ml

Vital
capacity
4800 ml

Total lung
capacity
6000 ml

Functional
residual
capacity
2400 ml

(a) Spirographic record for a male


Figure 21.16a

Nonrespiratory Air Movements
• Most result from reflex action
• Examples include: cough, sneeze, crying,
laughing, hiccups, and yawns


Gas Exchanges Between Blood, Lungs, and
Tissues
• External respiration
• Internal respiration
• Depends on composition of gasses and fluid


Composition of Alveolar Gas
• Alveoli contain more CO2 and water vapor
than atmospheric air


Gas Solubility
• Venous blood has much less oxygen than in
alveoli
• Oxygen diffuses into the veins
• Carbon dioxide is transfused the same way
• In the opposite direction


Inspired air:
P O2 160 mm Hg
P CO 0.3 mm Hg

Alveoli of lungs:
P O2 104 mm Hg
P CO 40 mm Hg

2

2

External
respiration
Pulmonary
arteries

Pulmonary
veins (PO2
100 mm Hg)

Blood leaving
tissues and
entering lungs:
PO2 40 mm Hg
PCO2 45 mm Hg

Blood leaving
lungs and
entering tissue
capillaries:
P O2 100 mm Hg
P CO2 40 mm Hg

Heart
Systemic
veins
Internal
respiration

Systemic
arteries
Tissues:
P O2 less than 40 mm Hg
P CO greater than 45 mm Hg
2


Figure 21.17

Ventilation-Perfusion Coupling
• Ventilation: amount of gas reaching the alveoli
• Perfusion: blood flow reaching the alveoli
• Ventilation and perfusion must be matched
(coupled) for efficient gas exchange


Internal Respiration
• Capillary gas exchange in body tissues
• Diffusion gradients are reversed compared to
external respiration
• Oxygen is low in tissues, high in blood
• Carbon dioxide is high in tissues, low in blood
• Gas exchange occurs


Transport of Respiratory Gases by Blood
• Oxygen (O2) transport
• 1.5% dissolved in plasma
• 98.5% loosely bound to Fe in hemoglobin (Hb)
• in RBCs
• 4 O2 per Hb


Transport of Respiratory Gases by Blood
• Carbon dioxide (CO2) transport
• Combines with water in plasma
• Forms Bicarbonate (HCO3–)


Transport and Exchange of CO2
• CO2 combines with water to form carbonic
acid (H2CO3), which quickly dissociates:
CO2

+

Carbon
dioxide

H2O
Water

↔

H2CO3

↔

Carbonic
acid

H+

+

Hydrogen ion

• Important in pH balance of blood
• How acidic or basic blood is
• Measurement of H+ ions

HCO3–

Bicarbonate ion

Influence of CO2 on Blood pH
• HCO3– in plasma is a buffer system
• Has the ability to add or remove H+ ions as
needed


Control of Respiration
• Main muscle is the diaphragm
• Innervated by the phrenic nerve
• Cervical nerve plexus


Breathing Abnormalities
• Hyperventilation: increased rate of breathing
• exceeds need
• May cause cerebral vasoconstriction and
cerebral ischemia

• Apnea: period of ceased breathing


Pulmonary Irritant Reflexes
• Receptors in the bronchioles respond to
irritants
• Promote constriction of air passages
• Receptors in the larger airways mediate the
cough and sneeze reflexes


Homeostatic Imbalances
• Chronic obstructive pulmonary disease (COPD)
• chronic bronchitis and emphysema
• Irreversible decrease in forced exhalation
• Increased risk when smoking


• Tobacco smoke
• Air pollution

α-1 antitrypsin
deficiency

Continual bronchial
irritation and inflammation

Breakdown of elastin in
connective tissue of lungs

Chronic bronchitis
Bronchial edema,
chronic productive cough,
bronchospasm

Emphysema
Destruction of alveolar
walls, loss of lung
elasticity, air trapping

• Airway obstruction
or air trapping
• Dyspnea
• Frequent infections

• Abnormal ventilationperfusion ratio
• Hypoxemia
• Hypoventilation

Figure 21.27

• Asthma
• Characterized by coughing, dyspnea, wheezing, and
chest tightness
• Active inflammation of the airways
• Constriction of airways
• Immune response


• Tuberculosis
• Infectious disease
• Mycobacterium tuberculosis
• Symptoms include spitting up blood
• Treatment entails a 12-month course of
antibiotics


• Lung cancer
• Leading cause of cancer deaths in North America
• 90% of cases result from smoking


Respiratory phys online

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Respiratory phys online

Similar to Respiratory phys online (20)

More from kmilaniBCC

More from kmilaniBCC (13)

Recently uploaded

Recently uploaded (20)

Respiratory phys online