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2. Tortora & Grabowski 9/e 2000 JWS The Respiratory System

3. The Respiratory System • Cells continually use O2 & release CO2 • Respiratory system designed for gas exchange • Cardiovascular system transports gases in blood • Failure of either system • rapid cell death from O2 starvation

4. Bronchi and Bronchioles • Primary bronchi supply each lung • Secondary bronchi supply each lobe of the lungs (3 right + 2 left) • Tertiary bronchi supply each bronchopulmonary segment • Repeated branchings called bronchioles form a bronchial tree

5. Histology of Bronchial Tree • Incomplete rings of cartilage replaced by rings of smooth muscle & then connective tissue • sympathetic NS & adrenal gland release epinephrine that relaxes smooth muscle & dilates airways • asthma attack or allergic reactions constrict distal bronchiole smooth muscle therefore reduces diameter • nebulization therapy = inhale mist with chemicals that relax muscle & reduce thickness of mucus

6. Double Blood Supply to the Lungs • Deoxygenated blood arrives through pulmonary trunk from the right ventricle • Bronchial arteries branch off of the aorta to supply oxygenated blood to lung tissue • Venous drainage returns all blood to heart • Less pressure in venous system • Pulmonary blood vessels constrict in response to low O2 levels so as not to pick up CO2 on there way through the lungs

7. Breathing or Pulmonary Ventilation • Air moves into lungs when pressure inside lungs is less than atmospheric pressure • Air moves out of the lungs when pressure inside lungs is greater than atmospheric pressure

8. Control of respiration • Respiration is under involuntary central and autonomic control • However voluntary influence on breathing occurs via connections between cerebral cortex and motor neurons controlling respiration

9. Tortora & Grabowski 9/e 2000 JWS Peripheral control • Fear, pain stress sudden changes in blood pressure or body temp, irritation of the airway and blood levels of oxygen and carbon dioxide can all effect the respiratory centre

10. Tortora & Grabowski 9/e 2000 JWS An increase in CO2 tension of the blood (hypercapnia) directly stimulates inspiratory and expiratory centres which increases rate and depth of breathing This results in hyperventilation which increases loss of CO2 from the lungs

11. Tortora & Grabowski 9/e 2000 JWS If arterial oxygen concentration falls below 60% of normal (hypoxaemia) the chemoreceptors are stimulated and in turn stimulate the respiratory centre to increase alveolar ventilation. An example of this mechanism is chronic obstructive pulmonary disease.

12. Tortora & Grabowski 9/e 2000 JWS Compliance of the Lungs • Ease with which lungs & chest wall expand depends upon elasticity of lungs & surface tension • Some diseases reduce compliance • tuberculosis forms scar tissue • pulmonary edema --- fluid in lungs & reduced surfactant • paralysis

13. Carbon Dioxide • Colourless, odourless gas • CO2 stimulates cells of the sympathetic nervous system the respiratory center and peripheral chemoreceptors • To much CO2 in inhaled air may cause • A depressant effect • Acidosis • Unresponsiveness • Carbon dioxide narcosis

14. Types of Hypoxia • Deficiency of O2 at tissue level • Types of hypoxia • hypoxic hypoxia--low pO2 in arterial blood • high altitude, fluid in lungs & obstructions • anemic hypoxia--too little functioning Hb • hemorrhage or anemia • ischemic hypoxia--blood flow is too low • histotoxic hypoxia--cyanide poisoning • blocks metabolic stages & O2 usage

15. Tortora & Grabowski 9/e 2000 JWS Respiratory Influences & Reflex Behaviors • Quick breathing rate response to exercise • input from proprioceptors • Inflation Reflex (Hering-Breurer reflex) • big deep breath stretching receptors produces urge to exhale • Factors increasing breathing rate • emotional anxiety, temperature increase or drop in blood pressure • Apnea or cessation of breathing • by sudden plunge into cold water, sudden pain, irritation of airway

16. Tortora & Grabowski 9/e 2000 JWS Smokers Lowered Respiratory Efficiency • Smoker is easily “winded” with moderate exercise • nicotine constricts terminal bronchioles • carbon monoxide in smoke binds to hemoglobin • irritants in smoke cause excess mucus secretion • irritants inhibit movements of cilia • in time destroys elastic fibers in lungs & leads to emphysema • trapping of air in alveoli & reduced gas exchange

17. Aging & the Respiratory System • Respiratory tissues & chest wall become more rigid • Vital capacity decreases to 35% by age 70. • Diminished ciliary action • Decrease in blood levels of O2 • Result is an age-related susceptibility to pneumonia or bronchitis

18. Tortora & Grabowski 9/e 2000 JWS Disorders of the Respiratory System • Asthma • Chronic obstructive pulmonary disease • Emphysema • Chronic bronchitis • Lung cancer • Pneumonia • Tuberculosis • Influenza • Pulmonary Edema • Cystic fibrosis

19. Drugs used in the Respiratory system

20. Expectorant drugs Expectorants drugs are used to stimulate and aid in the removal of sputum from the bronchial passages They also act to reduce the viscosity of thick tenacious mucous facilitating its movement out of the respiratory tract

21. Expectorant drugs • A number of plant derivatives are used in expectorant drugs • Including liquorice (glycyrrhiza glabra) and extracts of senega or squill • Safe to use in children but not infants

22. Expectorant drugs Advantages of expectorant drugs • Dilute thickened secretion (diluents) • Chemically breaking down mucous (mucolytics) • Promoting expulsion of these secretions • Mucolytic drugs ( Duro Tuss, Mucomyst) • Mucokinetic drugs (Vicks cough syrup,Robitussin) • Dornase Alfa- respiratory inhalant used in cystic fibrosis

23. Expectorant drugs • OTC chest rubs contain mixtures of volatile oils, which are inhaled deep into the air passageways to activate mucosal glands • Potassium iodide and ammonium salts are compounds that when excreted by bronchial mucosal galnds, stimulate mucous secretion

24. Expectorants • Common adverse effects • Very few • Some are gastric irritants, nausea and vomiting may occur • Rash diarrhoea, dizziness and headache

25. Expectorant drugs • Clinical considerations • Effects promoted by adequate fluid intake • Regular coughing and deep breathing

26. Diluents • Saline solutions is a isotonic solution. • Therapy by nebulisation is well tolerated, resulting in hydration of respiratory secretions • 0.45% saline may provide deeper penetration into the more distal airways

27. Mucolytic agents • Exert a disintegrating effect on mucous, facilitating removal from the lung bronchi or trachea by postural drainage, coughing or spitting • Most common are acetylcysteine (Parvolex)

28. Mucolytic agents • Bromhexine, acetylcysteine and sodium chloride • Thought to alter the structure of viscous mucous • No serious side effects reported, occasional mild GIT disturbance

29. Mucolytic agents • Acetylcysteine • Is available as a nebuliser, used for cystic fibrosis • Also used for an antidote for paracetamol overdose • Must be diluted with saline for nebuliser

30. Mucolytic agents • Bromehexine • Present in many cough and cold preparations

31. Mucolytic Agent • Dornase Alfa • Mucolytic agent used in management of cystic fibrosis • It is an enzyme that breaks down DNA of decaying neutrophils. • Administered via a nebuliser

32. Mucolytic Agent • Dornase Alfa • Common adverse effects • Hoarse voice and pharyngitis • Never dilute or mix with other medications in the nebuliser, it reduces its effectiveness

33. Decongestants • Decongestants • Vasoconstriction in mucous membranes leading to decongestion • Topical application of sympathomimetic amine decongestants which stimulate adrenoceptors.

34. Decongestants • These include • Oxymetazoline,pseudoephedrine, tramazoline, and phenylephrine xylometazoline

35. Decongestants • Common adverse effects • Pupil dilatation, constipation and hypertension • Some may lead to restlessness, insomnia and agitation

36. Decongestants • Clinical consideration • Contra indicates with those on MAO and trycyclic antidepressants • Only used for a few days • Not to be taken in the evening

37. Anti muscarinic agents • Dry up excess mucous, by blocking parasympathetic muscarinic receptors • Hyoscine (scopolamine) can be used to dry up excess respiratory secretions post operatively

38. Anti muscarinic agents • Side effects • Dry mouth, facial flushing, tacycardia, pupil dilatation and constipation • Monitor blood pressure and heart rate when using hyoscine

39. Asthma Pathophysiology Passage of air in and out of lungs is obstructed because of • Reversible bronchoconstriction • Chronic inflammation of the epithelium of the airways • Increased mucous secretion

40. Asthma Early phase • Bronchoconstriction and excessive secretion of mucous Late phase • Inflammation • Proliferation of fibroblasts and fibrosis • Oedema of the airways mucosa

41. Bronchodilators • Used to treat asthma, chronic bronchitis and emphysema • Used for over 5000 years

42. Bronchodilators • Used in the treatment of respiratory disorders that are characterised by inflammation, bronchospasm or bronchoconstriction, mucosal oedema and excessive mucous production • Aim is relief of symptoms and prevention of more serious attack

43. Asthma Signs and symptoms • Wheezing and cough • Dyspnoea ( difficulty breathing) • Chest tightness • Tachycardia • Fatigue • Sweating and anxiety

44. Asthma Triggers • Allergens/ house dust mites, animal fur, protein in foods • Drugs Beta blockers, penicillin and aspirin • Exercise • Emotional stress • Respiratory infections • Environmental pollutants

45. Asthma • Asthma medications • 1. Relievers • 2. Symptom controllers • 3. Symptom preventers

46. Asthma • RELIEVER MEDICATIONS • (Bronchodilators: short acting) B2 receptor agonists Ventolin (Salbutamol Ephedrine (Ephidrine hydrochloride) Airomir, Asmol, Bricanyl, Epaq

47. Asthma • RELIEVER MEDICATIONS • Provide relief from asthma symptoms within minutes • Relax muscles around the airway for four hours

48. Asthma • RELIEVER MEDICATIONS • Floradile (pale blue) Oxis (green) • Long acting relievers help to relax muscles around the airway for up to 12 hours • Taken daily taken in those that are taking regular inhaled steroid preventers

49. Asthma • SYMPTON CONTROLLERS • (long acting B2 antogonist • Salmeterol (Serevent) • Oxis inhaler (eformoterol) • Half lives 6-12 hours administered once or twice daily

50. Asthma • SYMPTON CONTROLLERS • Inhaled medications Flixotide (orange) Intal Forte (white) Pulmicort, Qvar (brown) Tilade (yellow) • Oral medication Singulair • Used in conjunction with short acting B2 agonists • Inhibit release of mast cell mediators (histamines, leukotrienes ,prostoglandins) from human lung tissues