Control Of Respiratory Function

Copyright © 2007 Lippincott Williams & Wilkins.

Chapter 20

Control of Respiratory Function


Lung FunctionsLung Functions

• Gas exchange

– Moves O2 into blood

– Removes CO2 from blood

• Blood storage

• Regulate vasoconstricting substances

– Bradykinin

– Angiotensin II

– Heparin


Conducting AirwaysConducting Airways

• Move air into lungs

• Warm and humidify air

• Trap inhaled particles


Respiratory Airways

Respiratory Airways

• Bronchioles

• Alveoli

• Gas is exchanged with the blood


Membranes and CavitiesMembranes and Cavities

• Parietal pleura

• Visceral pleura

• Pleural space (between pleurae)

• Mediastinum


Respiratory MusclesRespiratory Muscles

• Diaphragm

• Accessory muscles of inhalation

– External intercostals

– Scalene

– Sternocleidomastoid

• Accessory muscles of exhalation

– Internal intercostals

– Abdominal muscles


ComplianceCompliance

• How easily lungs can be inflated

• Depends on:

– Elastin and collagen fibers

– Water content

– Surface tension


Surfactant Reduces Surface TensionSurfactant Reduces Surface Tension


A Man’s Lungs Were Damaged During a Fire …

A Man’s Lungs Were Damaged During a Fire …

• He developed severe respiratory distress

• The doctor said smoke inhalation had caused an inflammation of his alveoli

• The damage had also destroyed some of his surfactant

• What had happened to his lung compliance?

• Why was he given positive-pressure ventilation?


Lung VolumesLung Volumes

• Tidal volume

• Inspiratory reserve

• Expiratory reserve

• Residual volume


Lung CapacitiesLung Capacities

• Vital capacity

• Inspiratory capacity

• Functional residual capacity

• Total lung capacity


Dynamic Lung FunctionDynamic Lung Function

• Forced vital capacity

• Forced expiratory volume

• FEV1.0

• Minute volume

• Maximum voluntary ventilation


Gas ExchangeGas Exchange

• Oxygen moves from alveolar air into blood

• Carbon dioxide moves from blood into alveolar air


Ventilation and PerfusionVentilation and Perfusion

• A child has inhaled a peanut, blocking her left primary bronchus

• How will the ventilation in her two lungs change?

• How will the composition of the air in her two lungs differ?

• Which lung should she send more blood to?

• How should her body alter perfusion of the lungs?


Ventilation-Perfusion MismatchingVentilation-Perfusion Mismatching

• Blood goes to parts of the lung that do not have oxygen to give it

• Blood does not go to parts of the lung that have oxygen


Blood Gases—OxygenBlood Gases—Oxygen

• Dissolved oxygen = PaO2 or PO2

– Normal value >80 mm Hg

• Oxygen bound to hemoglobin = oxyhemoglobin

– Normal value 95% to 97% saturation


Hemoglobin Holds 4 Oxygen MoleculesHemoglobin Holds 4 Oxygen Molecules

O2O2

O2

• How saturated is this molecule of hemoglobin?

• How could a person have a hemoglobin saturation of 95%?


Oxygen Capacity Oxygen Capacity

• Amount of oxygen the blood can hold

• What is the oxygen capacity of normal blood?

• What is the oxygen capacity of anemic blood?


Oxygen ReleaseOxygen Release• If the blood

released half of its oxygen to the tissues …

– How much oxygen would the normal tissues receive?

– How much would the anemic person's tissues receive?


Oxygen Release (cont.)Oxygen Release (cont.)

• Most body tissues have a PO2 of 40-60 mm Hg

• How much oxygen does the normal blood release at a PO2 of 40 mm Hg?

• The anemic blood?


Oxygen AffinityOxygen Affinity

• How tightly the hemoglobin holds onto the oxygen

• Which of these hemoglobin samples has the highest oxygen affinity?

• Which will release the most oxygen to the tissues?

AB

C


Blood Gases—Carbon DioxideBlood Gases—Carbon Dioxide

• Dissolved carbon dioxide = PaCO2 or PCO2

– Normal value 35–45 mm Hg

• Carbon dioxide bound to hemoglobin = carbaminohemoglobin

• Carbonic acid bicarbonate ion and H+

• When you exhale you remove CO2 from your blood and also decrease the amount of carbonic acid, raising your blood pH


Respiratory centers

pneumotaxic apneustic

stops inspiration; begins exhalation

lungs deflate

stretch receptors note decreased lung

volume

begins inspiration

lungs inflate

stretch receptors note increased lung

volume


Chemoreceptors Can Adjust Respiration Rate

Chemoreceptors Can Adjust Respiration Rate

• Central chemoreceptors

– Measure PCO2 and pH in cerebrospinal fluid

– Increase respiration when PCO2 increases or pH decreases

• Peripheral chemoreceptors

– Measure PO2 in arterial blood

– Increase respiration when PO2 <60 mm Hg


You Are Caring for a COPD Client …You Are Caring for a COPD Client …

• He has chronically high PCO2

• He is being given low-flow oxygen and complains all the time that he “needs more air,” so you turn up his oxygen

When you check on him later, he is unconscious and not breathing!

What happened?

When you check on him later, he is unconscious and not breathing!

What happened?

Control Of Respiratory Function

Health & Medicine

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