Pulmonary Physiology Slides PDF

**Functions of respiration:** **Components of respiration:** **Functional Anatomy of the Respiratory System** Upper Airway Nose/nasopharynx Mouth/oropharynx Larynx/hypopharynx Lower Trachea Main/lobar/segmental bronchi Conducting/terminal/respiratory bronchioles Alveolar ducts Alveoli *...

**Functions of respiration:** **Components of respiration:** **Functional Anatomy of the Respiratory System** Upper Airway Nose/nasopharynx Mouth/oropharynx Larynx/hypopharynx Lower Trachea Main/lobar/segmental bronchi Conducting/terminal/respiratory bronchioles Alveolar ducts Alveoli **Nose - Structures** *  Ala nasae* (i.e., alar cartilage) forms the borders of the *anterior nares* *  Anterior nares* lead into the *nasal vestibules* and eventually the *nasal fossae*, which are separated by the *nasal septum*  The nasal septum consists of the vomer bones and the vomeronasal and nasal septal cartilages  The three *nasal conchae* are scroll-shaped prominences along the lateral walls that are involved in filtration  The *nasal fossae* leads into the *nasopharynx* via the *nasal choanae* and also communicates with the *paranasal air sinuses*  The paranasal air sinuses include the frontal, ethmoid, maxillary, and sphenoid sinuses **Nose -- Neurovascular Structures** - Arterial Perfusion - Venous Drainage - Lymphatic Drainage - Innervation **Nose - Functions** - Heating - Humidification - Filtration - Olfaction **Pharynx** - Muscular tube that extends from skull base to the esophagus at vertebral level C6 - Tonsils -- aggregations of lymphoid tissue **Larynx - Structures** - Protective structure to prevent aspiration during swallowing that extends from vertebral level C3 to C6 - Vestibular folds -- bands of fibrous tissue covered by mucous membranes; superolateral to true vocal cords - True vocal cords -- fibromembranous folds attach to thyroid cartilage and arytenoids - Composed of one bone and nine cartilages, as well as ligaments, muscles, and membranes **Larynx - Musculature** **Cormack-Lehane Classification** - Grade 1 -- full view of laryngeal inlet - Grade 2a -- partial view of vocal cords - Grade 2b -- view of posterior aspect of vocal cords or arytenoids - Grade 3 -- view of epiglottis only - Grade 4 -- no visible laryngeal structures **Larynx -- Neurovascular Structures** - Arterial Perfusion - Innervation - Superior laryngeal nerve - External branch of the superior laryngeal nerve -- inferior constrictor muscle of pharynx, cricothyroid muscles - Internal branch of the superior laryngeal nerve -- interarytenoid muscles, sensory innervation between inferior aspect of epiglottis and true vocal cords - Inferior laryngeal nerve (i.e., recurrent laryngeal nerve \[RLN\]) -- all intrinsic laryngeal muscles except cricothyroid muscles and part of interarytenoid muscles, sensory innervation between true vocal cords and trachea **Trachea** - Protective structure to prevent airway collapse consisting of incomplete rings of cartilage that extends from inferior larynx to carina - Arterial Perfusion - Venous Drainage - Innervation **Bronchi --Neurovascular Structures** - Arterial Perfusion - Venous Drainage - Innervation - Sympathetic stimulation produces bronchodilation - Parasympathetic stimulation produces bronchoconstriction - Histamine and slow reactive substance of anaphylaxis also induce bronchoconstriction **Respiratory Zone** - Respiratory bronchioles - Alveolar ducts - Alveolar sacs - Alveoli **Alveoli** - Area of respiratory zone which functions primarily in gas exchange **Pulmonary Hilum** - Conduit to the lung 1. Mainstem bronchus 2. Pulmonary circulation 3. Bronchial circulation 4. Lymphatics/lymph nodes 5. Pulmonary innervation (e.g., Vagus nerve, sympathetic nerves) **Thoracic Cavity** - Consists of left pleural cavity, mediastinum, and right pleural cavity - Pleura -- serous membrane that separates the lungs from the mediastinum and thoracic cage - Parietal -- lines the chest wall, mediastinum, diaphragm - Visceral -- lines the lungs **Mechanics of Breathing** - Diaphragm - Primary muscle of inspiration; bilateral domes function independently - Separates thoracic cavity from abdominal cavity **Boyle's Law** - [*P*~1~*V*~1~ = *P*~2~*V*~2~]{.math.inline} - Inspiration - Expiration **Pleural, Alveolar, and Transpulmonary Pressures** - Pleural pressure (Ppl) - Alveolar pressure (Palv) - Transpulmonary pressure 6. [*Transpulmonary* *pressure* = *Palv*  − *Ppl*]{.math.inline} **Lung Compliance** - Compliance is the amount of force required to cause elastic deformation (i.e., expand) of the lung; measure of lung stiffness - Elastic forces of the lung tissue (e.g., collagen, elastin) - Elastic forces caused by alveolar surface tension - [*C* = *V**h*]{.math.inline} 10. *Re* -- Reynold's number 11. [*ρνd**h*]{.math.inline} 13. [*ρνd**r*]{.math.inline} - Demonstrates relationship between radius and surface tension within a sphere 17. However, alveoli are polyhedrons, not spheres **Lung Volumes**  Tidal Volume- amount of air inspired or expired with each normal breath  Inspiratory Reserve Volume- extra amount of air that can be inspired when the person inspires with full force  Expiratory Reserve Volume- extra amount of air that can be expired by normal forceful expiration after the end of a normal tidal expiration  Residual Volume- amount of air remaining in the lungs after the most forceful expiration **Lung Capacities**  Inspiratory Capacity- amount of air that a person can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount  Functional Residual Capacity- amount of air that remains in the lungs at the normal end of normal expiration  Vital Capacity- maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring them to the maximum extent  Total Lung Capacity- maximum amount of air that the lungs can contain with the greatest possible effort **Helium Dilution Method** - Certain lung volumes/capacities cannot be measured directly (i.e., by spirometry) 18. Functional Residual Capacity (FRC) 19. Residual Volume (RV) 20. Total Lung Capacity (TLC) - Indirect measurement (i.e., helium dilution) may be used to determine these volumes 21. Spirometer of known volume is filled with air/helium mixture of known concentration 22. Person expires normally, then breathes in air/helium mixture 23. Mixing of gas from spirometer and lungs (i.e., FRC) causes measurable dilution of helium **Minute Ventilation** - [*Minute* *Ventilation* = *Tidal* *Volume* (*V*~*T*~) × *Respiratory* *Rate* (*RR*)]{.math.inline} **Dead Space** - Ventilated areas that do not receive adequate perfusion to participate in gas exchange - Alveolar ventilation -- total volume of air each minute that is available for gas exchange 24. [*VA* = *RR* × (*TV* −*VD*)]{.math.inline} **Pulmonary Circulation** Bronchial circulation High pressure (i.e. systemic), low-flow (i.e. 2% of CO) circulation Supplies oxygenated blood to the conducting zone of the respiratory system Thoracic aorta- bronchial arteries- bronchial veins- azygos, hemiazygos, posterior intercostal, pulmonary veins Pulmonary circulation Low-pressure (i.e., pulmonary), high flow (i.e., all of CO) circulation Supplies deoxygenated blood to the respiratory zone for gas exchange Right ventricle- pulmonary arteries-.... -pulmonary veins- left atrium Vessels of the pulmonary arterial system are shorter, wider, and more distensible than systemic arteries, resulting in large compliance and low pulmonary vascular resistance (PVR) **Pulmonary System Pressures** - Right Ventricular Pressure - Pulmonary Artery Pressure (PAP) - Pulmonary Capillary Pressure - Pulmonary wedge pressure \~ 5 mm Hg - Left Atrial/Pulmonary Venous Pressures **Hypoxic Pulmonary Vasoconstriction** - Systemic circulation - Pulmonary circulation - When the [PA~*O*~2~~ ]{.math.inline}decreases (i.e., \ - Pc -- 7 mm Hg - Π if -- 14 mm Hg - Pif -- 8 mm Hg - Πp -- 28 mm Hg - The same concepts apply to peripheral capillaries; however, the forces are quantitatively different Ventilation-Perfusion Relationship in the Lung - Ventilation-Perfusion Ratio -- normally 0.8 25. Describes the distribution of ventilation (i.e., airflow) relative to perfusion (i.e., blood flow) - V/Q varies in different regions of the lung - Ventilation \ Perfusion (i.e., V/Q = ∞) - Alveoli that are ventilated but not perfused result in *dead space* - Ventilation \< Perfusion (i.e., V/Q = 0) - Alveoli that are perfused but not ventilated result in *shunt* **Dalton's Law of Partial Pressures** - Total pressure of a gas mixture is equal to the sum of the partial pressures of each constituent gas - P = P~O2~ + P~N2~ - P = (0.21 x 760 mm Hg) + (0.79 x 760 mm Hg) - P = P~O2~ + P~N2~ + P~H2O~ - P = (0.21 x 713 mm Hg) + (0.79 x 713 mm Hg) + 47 mm Hg **Alveolar Gas Equation** - PA~O2~ = Pi~O2~ -- (PA~CO2~/RQ) - PA~O2~ = (0.21 X \[760 mm Hg -- 47 mm Hg\]) -- (40 mm Hg/0.8) = 99 mm Hg **Fick's Law** - Describes the diffusion of gases across the alveolocapillary membrane - V~gas~=A×D(P1−P2) / T - Directly proportional - Directly proportional - Directly proportional - Inversely proportional **Oxygen Transport** - Physical dissolution in plasma (0.3%) - Bound to hemoglobin (99.7%) **Oxyhemoglobin Dissociation Curve** - Rightward shift (i.e., enhances release of oxygen from hemoglobin) 26. Increased H^+^ (i.e., decreased pH) 27. Increased CO~2~ 28. Increased temperature 29. Increased 2,3-BPG - Leftward shift (i.e., reduces release of oxygen from hemoglobin) 30. Decreased H^+^ (i.e., increased pH) 31. Decreased CO~2~ 32. Decreased temperature 33. Decreased 2,3-BPG 34. Methemoglobin 35. Carbon monoxide **Carbon Dioxide Transport** - Physical dissolution in plasma (5-10%) - Carbamino compounds (5-10%) - Bicarbonate (80-90%) - Catalyzed by [carbonic anhydrase] in RBCs - HCO~3~^-^ formed and diffuses out of the RBC - CL^-^ diffuses into the RBC maintaining equilibrium (i.e., [Chloride shift]) - H^+^ buffered with the RBC binding to Hgb **Bohr & Haldane Effects** - Bohr Effect -- CO~2~/H^+^ affect the affinity of Hgb for O~2~ - Haldane Effect -- O~2~ affects the affinity of Hgb for CO~2~/H^+^ **Control of Breathing** - Function of respiration is to maintain homeostatic concentrations of O~2~, CO~2~, and H^+^ throughout the body Control of Breathing - Medullary respiratory center - Contains afferent projections of the glossopharyngeal nerve (CN IX) and vagus nerve (CN X) - Located in the nucleus of the tractus solitarius of the medulla oblongata - "Pacemaker" of normal breathing - Located in the nucleus ambiguous and nucleus retroambiguus of the medulla oblongata - Involved in both inspiration and expiration during periods of increased ventilation - Pneumotaxic center - Apneustic center **Central Chemoreceptors** - Central chemoreceptors are located in the medulla oblongata; exposed to cerebrospinal fluid - Charged ions (e.g., H^+^ ) do not readily cross the blood-brain barrier - Gases (e.g., CO~2~ ) readily diffuse across the blood-brain barrier - In CSF, CO~2~ reacts with H~2~O to form carbonic acid, which then dissociates into HCO~3~^-^ and H^+^ **Peripheral Chemoreceptors** - Peripheral chemoreceptors are located in the aortic bodies and carotid bodies; exposed to arterial blood - Glomus cells contain O2-sensitive potassium channels that are inactivated by hypoxemia, causing cellular depolarization - Hypoxemia generates afferent impulses that are transmitted to the medulla oblongata **Hering-Breuer Reflex** - Stretch receptors in the muscular walls of the bronchi and bronchioles transmit signals via the vagus nerve to the dorsal respiratory group - Serves to prevent overdistension of alveoli by inhibiting high tidal volumes (i.e., \> 1500 mL) **Cough and Sneeze Reflexes** - Stimulation of the nose, trachea, and bronchi may trigger reflex expulsion of irritants - Sneeze: afferent impulse transmitted via trigeminal nerve (CN V) - Cough: afferent impulse transmitted via vagus nerve (CN X) **Acid-Base Balance** - Acid-base balance is maintained by respiratory system, kidneys, and buffers (i.e., weak acid and conjugate base) **Arterial Blood Gas Interpretation** - Acid-base disturbances - Normal acid-base values 36. [Pa~*CO*~2~~]{.math.inline}: 35 -- 45 mm Hg 37. HCO~3~^-^ : 22 -- 26 mEq/L **Compensatory Mechanisms** Respiratory System- fast acting Acidosis: hyperventilation Alkalosis: hypoventilation Kidneys- slow acting Acidosis: increased excretion of nonvolatile acid, increased retention of HCO3 Alkalosis: decreased excretion of H+, decreased retention of HCO3 **Treatment of Blood Gas Abnormalities** - Mechanical ventilation - NaHCO~3~ 38. [HCO3− *Deficit* = (*desired* *HCO*3− *level* -- *patient*'*s* *HCO*3− *level*) *x* *weight* *in* *kg* *x* 0.3]{.math.inline} - Initial administration of half the calculated [HCO3− ]{.math.inline} deficit is recommended