respiratory phys online

Copyright © 2011 Pearson Education, Inc.

BREATHING


Mechanics of Breathing

Pulmonary ventilation has two phases:

1. Inspiration - gases flow into the lungs

2.Expiration - gases exit the lungs

Boyle’s LawP1V1 = 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

Copyright © 2011 Pearson Education, Inc. Figure 21.13 (1 of 2)

Sequence of events

Changes in anterior-posterior and superior-

inferior dimensions

Changes in lateraldimensions

(superior view)

Ribs are elevatedand sternum flares

as externalintercostals

contract.

Diaphragmmoves inferiorly

during contraction.

Externalintercostalscontract.

Inspiratory muscles contract (diaphragm descends; rib cage rises).

2

1

Thoracic cavity volume increases.

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).


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

Copyright © 2011 Pearson Education, Inc. Figure 21.13 (2 of 2)

Sequenceof events

Changes in anterior-posterior and superior-

inferior dimensions

Changes inlateral dimensions

(superior view)

Ribs and sternumare depressed

as externalintercostals

relax.

Externalintercostalsrelax.

Diaphragmmovessuperiorlyas it relaxes.

1 Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages).

2 Thoracic cavity volume decreases.

3 Elastic lungs recoil 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 intra-pulmonary pressure is 0.

Copyright © 2011 Pearson Education, Inc. Figure 21.14

5 seconds elapsed

Volume of breath

Intrapulmonarypressure

Expiration

Intrapleuralpressure

Trans-pulmonarypressure

InspirationIntrapulmonary 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.


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

Copyright © 2011 Pearson Education, Inc. Figure 21.16b

Respiratoryvolumes

Tidal volume (TV) Amount of air inhaled or exhaled with each breath under resting conditions

3100 ml Inspiratory reservevolume (IRV)

Expiratory reservevolume (ERV)

Residual volume (RV) Amount of air remaining in the lungs after a forced exhalation

500 ml

Amount of air that can be forcefully inhaled after a nor-mal tidal volume inhalationAmount of air that can beforcefully exhaled after a nor-mal tidal volume exhalation

1200 ml

1200 ml

Measurement DescriptionAdult maleaverage value

1900 ml

500 ml

700 ml

1100 ml

Adult femaleaverage value

Respiratory Volumes


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

Copyright © 2011 Pearson Education, Inc. Figure 21.16b

Respiratorycapacities

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

Functional residualcapacity (FRC)

Volume of air remaining in the lungs after a normal tidal volume expiration: FRC = ERV + RV

Maximum amount of air contained in lungs after a maximum inspiratory effort: TLC = TV + IRV + ERV + RVMaximum amount of air that can be expired after a maxi-mum inspiratory effort: VC = TV + IRV + ERVMaximum amount of air that can be inspired after a normal expiration: IC = TV + IRV

Total lung capacity (TLC)

Vital capacity (VC)

Inspiratory capacity (IC)

6000 ml

4800 ml

3600 ml

2400 ml

4200 ml

3100 ml

2400 ml

1800 ml

Respiratory Capacities

Copyright © 2011 Pearson Education, Inc. Figure 21.16a

Inspiratoryreserve volume

3100 ml

Tidal volume 500 ml

(a) Spirographic record for a male

Expiratoryreserve volume

1200 ml

Residual volume1200 ml

Functionalresidualcapacity2400 ml

Inspiratorycapacity3600 ml Vital

capacity4800 ml

Total lungcapacity6000 ml

Respiratory Volumes and Capacities


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 160 mm HgP 0.3 mm Hg

Blood leavinglungs andentering tissuecapillaries:P 100 mm HgP 40 mm Hg

Alveoli of lungs:P 104 mm HgP 40 mm Hg

O2

Heart

Blood leavingtissues andentering lungs:P 40 mm HgP 45 mm Hg

Systemicveins

Systemicarteries

Tissues:P less than 40 mm HgP greater than 45 mm Hg

Internalrespiration

Externalrespiration

Pulmonaryveins (P100 mm Hg)

Pulmonaryarteries

CO2

O2

CO2

O2

CO2O2

CO2

O2

CO2

O2


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:

• Important in pH balance of blood

• How acidic or basic blood is

• Measurement of H+ ions

CO2 + H2O H2CO3 H+ + HCO3–

Carbondioxide

Water Carbonic acid

Hydrogen ion 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

• Airway obstruction or air trapping• Dyspnea• Frequent infections

• Abnormal ventilation- perfusion ratio• Hypoxemia• Hypoventilation

-1 antitrypsindeficiency

Continual bronchialirritation and inflammation

Breakdown of elastin inconnective tissue of lungs

Chronic bronchitisBronchial edema,chronic productive cough,bronchospasm

EmphysemaDestruction of alveolarwalls, loss of lungelasticity, air trapping



• 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

Business

pearson education

inspiration pressure

p2v2 pressure

pressure gradients

lung volume increases

pleural cavity pressure

air gases

air flows