1 Respiratory Physiology

2 Mechanics of Breathing

3 4 distinct events Pulmonary ventilation: air is moved in and out of the lungs External respiration: gas exchange between blood and alveoli Respiratory gas transport: CV system transports oxygen and carbon dioxide between lungs & tissues Internal respiration: gas exchange between blood & tissue cells

4 Cellular respiration: actual use of oxygen & production of carbon dioxide in the cells to make energy: C6H12O6 + 9O2  6CO2 + 6H2O

5 Pulmonary ventilation: Depends on pressure changesBreathing Inspiration = moving air into the lungs Expiration = moving air out of lungs Breathing Mechanism Animation

6 Pressure RelationshipsIntrapulmonary pressure Pressure within the alveoli (lungs) Changes with phases of breathing Always equalizes itself with atmospheric pressure Intrapleural pressure Pressure within intrapleural space Always 4 mmHg less than intrapulmonary pressure

7 Lung Pressure Atelectasis – term for lung collapsepneumothorax – air in the intrapleural space due to trauma causing lung collapse Pneumothorax

8 Atelectasis

9 Inspiration Main inspiratory musclesDiaphragm & external intercostals Thoracic dimensions change to increase volume of thoracic cavity by 0.5 liters Intrapulmonary pressure drops 1-3 mmHg and air rushes in for normal quiet inspiration A deep forced inspiration requires activation of accessory muscles

10 Expiration A passive process dependent on natural lung elasticityThe lungs recoil, alveoli compress, volume decreases,, intrapulmonary pressure rises, gas outflows to equalize the pressure with atmospheric pressure Forced expiration requires contraction of abdominal muscles

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12 Respiratory Sounds Bronchial sounds: produced by air rushing through trachea & bronchi Vesicular sounds: produced by air filling lungs Bronchial vs. Vesicular

13 Respiratory Sounds Wheezing: whistling sound Rales: rasping soundWheezing vs rales

14 Physical factors influencingPulmonary ventilation can be influenced by 4 physical factors Respiratory passage resistance Lung compliance Lung elasticity Alveolar surface tension forces

15 Respiratory passage resistanceFriction as air moves through passages Smooth muscle bronchoconstriction Disorders such as asthma Local accumulations of mucus, infectious material, and tumors will also cause the air flow to be reduced

16 Asthma

17 Lung compliance The ease with which lungs can readily expandAffected by the elasticity of the lungs and the thoracic cage Diminished by 2 main factors: Fibrosis of the lung tissue Ossification and/or muscle paralysis impairs flexibility of the thoracic cage

18 Lung fibrosis

19 Lung Elasticity Essential for normal expirationEmphysema: tissue becomes less elastic and more fibrous (alveolar walls break down and surface area is lost)

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21 Alveolar Surface Tension ForcesSurface tension – molecules of liquid hold together with hydrogen bonds Surfactant – substance which interferes with cohesion of water molecules so less energy is needed to expand the lungs IRDS – Infant Respiratory Distress Syndrome

22 Gas Exchanges in the Body

23 Gas exchanges occur: Between the blood and the alveoli ANDBetween the blood and the tissue cells Takes place by simple diffusion Depends on pressures of oxygen & carbon dioxide that exist on opposite sides of the exchange membrane Always move from high to low pressures

24 Factors influencing internal & external respiration

25 Factors that Influence: Ratio RelationshipsPartial pressure gradients and gas solubilities Oxygen = has low solubility but steep partial pressure gradient Carbon dioxide = has solubility ~20x greater than oxygen but very low partial pressure gradient

26 Factors influencing internal & external respirationThickness of respiratory membranes 0.5 to 1.0 micrometers edematous (swollen) tissue can be caused by congestion and pneumonia - hinders diffusion Hypoxia = oxygen deprivation

27 Edematous lung tissue

28 Factors influencing internal & external respirationSurface Area 50-70 square meters for gas exchange

29 Factors influencing internal & external respirationSurface Area Emphysema Walls of alveoli break down Less surface area to volume ratio

30 Control of Respiration

31 Nerves The two nerves that transmit to the respiratory muscles are the phrenic and intercostal nerves The neural centers that control respiration rate & depth are located in the medulla & pons Irritation to phrenic nerve is responsible for hiccups (spasm of diaphragm muscle)

32 Breathing Terms Eupnea = normal respiration rateApprox breaths per min Hyperpnea = higher than normal rate Apnea = No rate Dyspnea = general term for abnormal rate Physical factors, conscious control, emotional factors, and chemical factors all influence rate & depth

33 Hyperventilation Respiratory alkalosis resultsDeep & rapid respiration Too much CO2 is vented out of the body Respiratory alkalosis results

34 Hyperventilation treatmentTrap CO2 and rebreathe it – building back up the levels of CO2 until they are normal again.

35 Hypoventilation Slow & shallow respiration (usually caused by a disease process) Not adequate expiration so CO2 is not vented out of the body

36 Disorders of Respiratory System

37 COPD Chronic Obstructive Pulmonary Disorder A group of disorders that block airflow & make breathing difficult

38 Chronic Bronchitis chronic mucus productionImpairs ventilation and gas exchange Reduction of airway diameter Causative factors: cigarette smoking

39 Emphysema Alveolar walls collapse = loss of surface area so less gas diffusion Causative factor: cigarette smoking

40 4 features in common Both emphysema and chronic bronchitis have:Smoking history Dyspnea Coughing & pulmonary infections Will develop respiratory failure, hypoxia, acidosis

42 Lung Cancer Basic Info 1/3 of all cancer deaths are due to lung cancers 90% have a smoking history Metastasizes very rapidly due to vascularity of lungs

43 Metastasis

44 3 types of lung cancer Squamous cell carcinoma AdenocarcinomaSmall cell carcinoma

48 Treatments Resection of diseased portion of lung (thoracotomy)Radiation therapy Chemotherapy

50 Cystic Fibrosis Genetic disorder – recessiveCauses oversecretion of thick mucus that clogs respiratory passages & other organs Impairs food digestion by clogging ducts that secrete enzymes

51 Cystic Fibrosis

52 SIDS - Sudden Infant Death SyndromeSudden, unexplained death of an infant less than 1 year old Possibly caused by brain abnormalities that control respiration, heart rate, or consciousness Environmental factors to reduce risks – sleep on back not on stomach, firm crib with no blankets or stuffed animals or pillows Sudden infant death syndrome (SIDS): Risk factors - MayoClinic.com

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54 Asthma Bronchoconstriction of passageways in response to allergen, temperature changes, & exercise Can be managed with medication

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