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CHAPTER 21 CONTROL OF RESPIRATORY FUNCTION Essentials of Pathophysiology.

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Presentation on theme: "CHAPTER 21 CONTROL OF RESPIRATORY FUNCTION Essentials of Pathophysiology."— Presentation transcript:

1 CHAPTER 21 CONTROL OF RESPIRATORY FUNCTION Essentials of Pathophysiology

2 PRE LECTURE QUIZ  Pulmonary ventilation is the movement of blood through the lungs.  Deoxygenated blood leaves the right heart through the pulmonary veins.  The peripheral chemoreceptors monitor arterial oxygen levels and will stimulate respirations when the PO 2 has dropped below 60 mm Hg.  Lung compliance refers to the ease with which the lungs can be inflated.  The effects of airway resistance on airflow can be illustrated by using Poiseuille’s law, which states that resistance to flow is inversely related to the fourth power of the radius. F F T T T

3 PRE LECTURE QUIZ  __________ exerts very important effects on lung inflation, including lowering the surface tension, increasing lung compliance and ease of inflation, and assisting in preventing pulmonary edema by keeping the alveoli dry.  The relation between the oxygen carried in combination with hemoglobin and the PO 2 of the blood can be described using the oxygen–hemoglobin __________ curve.  The most important chemoreceptors for sensing changes in blood carbon dioxide content are the __________ chemoreceptors.  __________ refers to the movement of gases in the alveoli and across the alveolar–capillary membrane.  The blood vessels in the pulmonary circulation undergo marked ________________ when they are exposed to hypoxia. Diffusion dissociation peripherial Surfactant Vasoconstriction

4 LUNG FUNCTIONS  Gas exchange  Moves O 2 into blood  Removes CO 2 from blood  Blood storage  Regulate vasoconstricting substances  Bradykinin-  Angiotensin II  Heparin- formed locally in injured tissue, acts in vasodilation of small arterioles, is considered to play a part in inflammatory processes sulfuric acid ester that occurs especially in the liver and lungs, that prolongs the clotting time of blood by preventing the formation of fibrin obtained from the liver and lungs of domesticated food animals protamine sulfate- is a heparin antagonist

5 CONDUCTING AIRWAYS  Move air into lungs  Warm and humidify air  Trap inhaled particles (Mucus escalator)

6 CONDUCTING & RESPIRATORY AIRWAYS Note Change of Cell Type & Thinning of Air to Blood Distance

7 MEMBRANES AND CAVITIES  Parietal pleura  Visceral pleura  Pleural space (between pleurae)  Mediastinum

8 RESPIRATORY AIRWAYS  Bronchioles  Alveoli  Gas is exchanged with the blood

9 QUESTION Which serous membrane lines the thoracic cavity? a. Viscera pleura b. Parietal pleura c. Visceral mediastinum d. Parietal mediastinum

10 ANSWER b. Parietal pleura The organs and walls of the thoracic and abdominal cavities are covered with serous membranes. Visceral membranes cover the organ; parietal membranes line the cavity walls. The two membranes and the space between them allow for ease of movement. The thoracic cavity is lined by parietal pleura; the lungs are covered by visceral pleura.

11 RESPIRATORY MUSCLES  Diaphragm  Accessory muscles of inhalation  External intercostals  Scalene  Sternocleidomastoid  Accessory muscles of exhalation  Internal intercostals  Abdominal muscles

12 QUESTION Tell whether the following statement is true or false: During inhalation, the diaphragm contracts and flattens.

13 ANSWER True The diaphragm is the main muscle of inhalation/inspiration. During inhalation, the diaphragm contracts and flattens (it moves downward in order to accommodate the volume of air you are taking in, allowing space for the lungs to expand). During exhalation, the diaphragm relaxes and moves back up.

14 COMPLIANCE  How easily lungs can be inflated depends on:  Elastin and collagen fibers  Water content  Surface tension

15 SURFACTANT REDUCES SURFACE TENSION

16 SCENARIO:  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 Question :  What had happened to his lung compliance?  Why was he given positive-pressure ventilation?

17 LUNG VOLUMES Time

18 LUNG CAPACITIES  Vital capacity  Inspiratory capacity  Functional residual capacity  Total lung capacity

19 LUNG VOLUMES  Tidal volume  Inspiratory reserve  Expiratory reserve  Residual volume

20 DYNAMIC LUNG FUNCTION  Forced vital capacity  Forced expiratory volume  FEV 1.0  Minute volume  Maximum voluntary ventilation

21 FORCED VITAL CAPACITY  MMEF =Mean Mid Expiratory Flow  Matching:  Normal expiration  Obstructive expiration  Restricted Lungs A A B C B C Flow diagram Volume diagram

22 QUESTION Which measure of lung function indicates the total amount of air that the lungs can hold? a. Tidal volume b. Functional residual capacity c. Vital capacity d. Total lung capacity

23 ANSWER d. Total lung capacity is the maximum amount of air that the lungs can hold—everything (volume- wise) at the end of a maximal inhalation (the deepest breath one can possibly take). Normal TLC is approximately 6 L.

24 GAS EXCHANGE  Oxygen moves from alveolar air into blood  Carbon dioxide moves from blood into alveolar air

25 VENTILATION AND PERFUSION Scenario: A child has inhaled a peanut, blocking her left primary bronchus. Question: 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?

26 VENTILATION–PERFUSION MISMATCHING  In mismatch Blood goes to parts of the lung that do not have oxygen, and  Blood does not go to parts of the lung that have oxygen  In normal function blood perfusion is routed opposite of other body tissues. Blood with no air Air with no Blood Air and blood

27 QUESTION Tell whether the following statement is true or false: Ventilation-perfusion mismatch results in hypoxia.

28 ANSWER True In either case (ventilation without perfusion or perfusion without ventilation) oxygen is not picked up by the capillaries and delivered to the tissues. The result of decreased oxygen at the tissue level is termed hypoxia.

29 BLOOD GASES—OXYGEN  Dissolved oxygen = PaO 2 or PO 2  Normal value >80 mm Hg  Oxygen bound to hemoglobin = oxyhemoglobin  Normal value 95% to 97% saturation

30 HEMOGLOBIN HOLDS 4 OXYGEN MOLECULES How saturated is this molecule of hemoglobin? How could a person have a hemoglobin saturation of 95%?

31 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? mg/dL

32 OXYGEN 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?

33 OXYGEN RELEASE (CONT.)  Most body tissues have a PO 2 of mm Hg  How much oxygen does the normal blood release at a PO 2 of 40 mm Hg?  The anemic blood?

34 OXYGEN 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? A B C PO2PO2 Factors that shift the curve: CO 2, pH, DPG, Fetal Hb

35 BLOOD GASES—CARBON DIOXIDE  Dissolved carbon dioxide = PaCO 2 or PCO 2  Normal value 35–45 mm Hg  Carbon dioxide bound to hemoglobin = carbaminohemoglobin  Carbonic acid  bicarbonate ion and H +  When you exhale you remove CO 2 from your blood and also decrease the amount of carbonic acid, raising your blood pH  CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 -

36 QUESTION Tell whether the following statement is true or false: The relationship between PCO 2 and pH is direct.

37 ANSWER False The relationship is indirect. As PCO 2 levels rise, the amount of carbonic acid in the blood increases, making the pH more acidic (decreasing it). CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 -

38 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 Respiratory Control

39 CHEMORECEPTORS CAN ADJUST RESPIRATION RATE  Central chemoreceptors  Measure PCO 2 and pH in cerebrospinal fluid  Increase respiration when PCO 2 increases or pH decreases  Peripheral chemoreceptors  Measure PO 2 in arterial blood  Increase respiration when PO 2 <60 mm Hg

40 SCENARIO You are caring for a COPD client…  He has chronically high PCO 2  He is being given low-flow oxygen and complains all the time that he “needs more air,” so you turn up his oxygen. Question:  When you check on him later, he is unconscious and not breathing. What happened?


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