Cardiopulmonary Anatomy & Physiology PDF

RINALIZA P. BOGSULEN, RTRP CARDIOPULMONARY ANATOMY & PATHOPHYSIOLOGY STRUCTURE & FUNCTION  Thorax 1. Structure a. shape – conical b. boundaries – diaphragm & thoracic inlet c. formed by: - rib cage - thoracic vertebra - sternum...

RINALIZA P. BOGSULEN, RTRP CARDIOPULMONARY ANATOMY & PATHOPHYSIOLOGY STRUCTURE & FUNCTION  Thorax 1. Structure a. shape – conical b. boundaries – diaphragm & thoracic inlet c. formed by: - rib cage - thoracic vertebra - sternum d. has 3 compartments - mediastinum - right pleural cavity - left pleural cavity Thorax 2. Function a. protection of the vital organs b. helps attain changes in lung volumes Thorax 3. Bones of the Thoracic Cage a. Ribs - 1- 7 ribs – true ribs - 8 – 10 – false ribs - 11 – 12 – floating ribs *1st rib and its cartilage – connected to the manubrium directly beneath the clavicle *2nd rib and its cartilage – adjacent to the sternal angle Thorax Rib Movement – Ribs 2 – 7 – plays an important role in ventilation Movement increases the AP and transverse diameters of the chest – Ribs 8 – 10 Elevation of the anterior end reduces the thoracic AP diameter  Ribs 11 – 12 – point of muscle insertion and protection of the contents of the upper abdomen  1st Rib – increases the AP diameter during increased ventilation Thorax b. Thoracic Vertebrae - 12 in numbers - common structure with the cer-vical and lumbar vertebrae * transverse process have facets that function as point of articulation of each rib to allow for rotation and elevation Thorax c. Sternum 1. shape – dagger shape 2. function - point of attachment - protection 3. components - manubrium - body - xiphoid Muscles of Ventilation A. Primary –active during quiet effortless breathing and exercise 1. diaphragm 2. intercostal muscles B. Accessory –assist the primary muscles when ventilatory demand increases 1. scalene 2. sternocleidomastoid 3. pectoralis 4. abdominal muscles Muscles of Ventilation 1. Diaphragm a. Structure - Large dome shaped muscle that arises from the lumbar vertebrae - Has 2 “leaves”(R & L hemidiaphragm) - innervated by the phrenic nerves b. Function - accounts for 75% increase in thoracic volume Muscles of Ventilation 2. Intercostal Muscles a. external – arise from the lower edge of each rib b. internal – lie beneath the external intercostal muscles Function: 1. elevates the ribs thus increasing the thoracic volume Muscles of Ventilation Accessory Muscles 1. Scalene origin: transverse processes of the 2nd – 6th cervical vertebrae insertion: 1st & 2nd ribs Function: 2. Primary function – elevate the 1 st and 2nd ribs and flex the neck 2. Accessory – elevation of the 1 st & 2nd ribs Muscles of Ventilation 2. Sternocleidomastoid - Located on each side of the neck - Origin: sternum and the clavicle - Insertion: mastoid process and occipital bone of the skull Function: 1. Primary – rotation and upward move- ment of the head 2. Accessory – elevation of the sternum thus increasing the AP diameter of the chest Muscles of Ventilation 3. Pectoralis Major - Powerful fan shaped muscles - Origin: clavicle and sternum - Insertion: upper part of the humerus Function: 1. Primary – pull the arm to the body 2. Accessory – elevates the chest thus increasing the AP diameter Muscles of Ventilation 4. Trapezius - large, flat triangular muscle located in the upper part of the back and the back of the neck - Origin: occipital bone, liagmentum nuchae, spinous process of the 7th cervical vertebrae - Insertion: spine of the scapula Function: 1. Primary – shrugging the shoulders 2. Accessory – elevate the thoracic cage Muscles of Ventilation 5. Rectus Abdominis - Assist in compressing the abdominal contents thus pushing the diaphragm into the thoracic cage 6. External & Internal Oblique - Assist in compressing the abdominal contents Anatomic Deadspace Volume of air in the conducting airways Does not participate in the process of gas exchange Approx= 1mL per pound of ideal body weight Alveolar Ventilation Amount of gas reaching the alveoli Depends on RR, dead space and tidal volume VA = RR (Vt – VDanat) Alveolar Deadspace Volume of gas in the alveoli which are unperfused Wasted ventilation VDalv Physiologic Deadspace Sum of anatomic and alveolar deadspace Vdphys = Vdanat + Vdalv Total volume of wasted ventilation VENTILATION Pressure Differences Across the Lungs: Pressure gradient – difference between 2 pressures Functions: 1. moving air in and out of the lungs 2. maintain the lungs inflated Driving Pressure - the force required to move gas through a tube  Trans airway Pressure / Trans respiratory Pressure (Pta / Prs) - pressure difference between the mouth pressure and alveolar pressure - Pta = Pm – Palv / Prs = Palv – Pao Transpulmonary pressure ( Ptp / PL) - difference between the alveolar pressure and pleural pressure - Ptp / PL = Palv – Ppl Transthoracic pressure (Ptt / Pw) - pressure difference between the alveolar pressure and the body surface pressure - Ptt / Pw = Palv – Pbs Lung Compliance (CL) - change in lung volume per pressure change - measured in L/cmH20 - at rest – the average compliance for each breath is about 0.1L/ cmH20 - Chest wall compliance = 0.1L/cmH20 Elastance - ability of a matter to return to its original resting position or shape after the external force no longer exist - change in pressure per change in volume - opposite of compliance - * Hooke’s Law - when an elastic body is acted upon by 1 unit of force, the elas- tic body will stretch 1 unit of length until the force goes beyond the elastic limit causing it to break or burst Surface Tension - cohesive force at the liquid – gas interface - * La Place’s Law - pressure varies directly with the surface tension of the liquid and inversely with its radius P=4st r where: P = pressure ST = surface tension r = radius Airway Resistance - ratio of driving pressure responsible for gas movement - accounts for 80% of the frictional resistance to ventilation Raw = Palv – Pao V - normal airway resistance in adult in the tracheobronchial tree is 0.5 – 2.5cmH20/L/sec Factors Affecting Airway Resistance 1. Pattern of Flow a. Laminar flow - streamlined gas flow - gas molecules move trough a tube in a pattern parallel to the sides of the tube - occurs at low flow rates and low pressure gradients Poiseuille’s Law P=V r4 * the driving pressure to maintain the same air flow must increase by 16 fold when the radius of the airway is reduced by half its original size. b. Turbulent Flow - gas molecules that move through a tube in a random manner - gas flow encounters resistance from both sides of the tube and collision with the other gas molecules - occurs at high flow rates and high pressure gradients Factors Affecting Airway Resistance 2. Viscosity 3. length GAS EXCHANGE Blood – Gas Barrier Extremely thin (0.2–0.3 μm) over much of its area Enormous surface area of 50 to 100 m2 Large area obtained by having about 500 million alveoli So thin that large increases in capillary pressure can damage the barrier Diffusion Process of gas molecules moving from area of greater concentration to an area of lesser concentration Factors affecting diffusion: a. alveolar epithelium b. interstitium c. capillary endothelium Fick’s Law of Diffusion Vgas = [(AxD) ÷ T ] (P1 – P2) Where: A – cross sectional area available for diffusion D – diffusion coefficient of the gas T – thickness of the membrane P1-P2 = partial pressure gradient Ventilation vs. Perfusion V/Q ratio = 0.8 Regional differences in ventilation and perfusion Causes of Hypoxemia 1. Low PIO2 / FIO2 – Breathing gases with low O2 concentration at sea level – Pressure less than the atmospheric pressure E.g. high altitude – “mountain sickness” to illustrate: PO2 of air = (760- 47) x 0.21 = 149.73 ≈ 150 PO2 in the alveoli = 100 What will happen to the atmospheric pressure at higher altitude? What about the PiO2? 735 – 47 mmHg x 0.21 = 144.48 ≈ 144 2. Hypoventilation High PaCO2, decrease VA Add PaO2 and PaCO2 = 110 – 130 Causes: – COPD, SIDS, obesity, OSA, CSA, upper airway obstruction – CNS depression – Head trauma, poliomyelitis, muscular dystrophy – Neuromuscular disorders 3. V/Q Mismatch Most common cause of hypoxemia  Increased V/Q – Increased ventilation or decreased perfusion ↑ PAO2 & ↓PACO2 Decreased V/Q – decreased ventilation or increased perfusion ↓PAO2 & ↑PACO2 o Wasted Ventilation – ventilation is good but O perfusion – Causes: Pulmonary emboli Partial /complete obstruction within the pulmonary capillary Extrinsic pressure on the pulmonary vessels Destruction of the pulmonary vessels Decrease CO  Shunted blood – good perfusion in the absence of ventilation Causes: – COPD – RLD – hypoventilation  A. Anatomic Shunt Normal physiologic shunt = 3% (bronchial venous drainage, thebesian veins) 4. Shunt Causes: congenital heart disease, intrapulmonary fistula, vascular lung tumors B. Capillary Shunt Causes: alveolar collapse or atelectasis, alveolar fluid accumulation, alveolar consolidation C. Shunt-Like Effect True Shunt- refractory to OT 1. alveoli cannot accommodate any form of ventilation 2. blood cannot carry more O2 if fully saturated Cardiovascular System The Heart A hollow muscular organ Approximately the size of a person’s fist Apex – formed by the tip of the left ventricle Base – formed by the atria 1. Layers of the Wall of the Heart Pericardium – loose membranous sac – Parietal – Visceral Epicardium – visceral pericardium Myocardium – bulk of the heart Endocardium – thin layer of tissue 2. The Heart’s Chambers Chambers of the Heart 2 Atria – receiving chambers – Right Atrium – Left Atrium – 2 ventricles – pumping chambers Right Ventricles Left Ventricles 3. The Heart’s Valves  Heart’s Valves Atrioventricular Valves (AV Valves) – Tricuspid Valve – between the RA & RV – Bicuspid (Mitral) Valve – between the LA & LV Semilunar Valves Aortic Valve – between the LV and aorta Pulmonic Valve – between the RV and PA 4. Blood Supply to the Heart 1. right and left coronary arteries – first branches of aorta, supplies blood to the heart - major branches – anterior interventricular and circumflex arteries on the left and the posterior interventricular and marginal arteries on the right Blood Supply to the Heart Left Anterior Descending Artery – supplies blood to the anterior wall of the LV, interventricular septum, RBB, left anterior fasciculus of the LBB Circumflex artery – supplies blood to the lateral walls of the LV, LA and left posterior fasciculus of the bundle branch Blood Supply to the Heart 2. coronary sinus – collects venous blood from the heart & empties to the right atrium – both are embedded in fat within the coronary sulcus – coronary sulcus – encircles the heart, indicates border between atria and ventricles 5. Nerve Supply to the Heart Heart is supplied by the 2 branches of the ANS – Sympathetic (Adrenergic) – heart’s accelerator increase HR, automaticity, AV conduction and contractility – Parasympathetic (Cholinergic) – heart’s brakes decrease HR 6. Functions of the Heart A. Cardiac Cycle  Phases of the Cardiac Cycle 1. Isovolumetric ventricular contraction - increase tension in the ventricles - AV and semilunar valves are closed 2. Ventricular ejection - ventricular pressure exceed aortic and pulmonary arterial pressure Phases of the Cardiac Cycle 3. Isovolumetric relaxation - semilunar valves and AV valves are closed - atrial filling (atrial diastole) 4. Ventricular filling - Av valves open - blood flow into the ventricles (70%) Phases of the Cardiac Cycle 5. Atrial systole - atrial kick - the remaining 30% of blood will move to the ventricles  Functions of the Heart B. Cardiac Output – total amount of blood pumped per minute CO = HR x SV Factors affecting SV 1. preload (ventricular stretch)- results in SV 2. afterload (force the heart must pump against) - results in SV 3. contractility - results in SV - hypoxia and acidosis contractility 7. Blood Circulation Electrophysiology of the Heart Absolute refractory period Relative refractory period Phases of an Action Potential Phase 0 – cell receives an impulse (depolarization), Na moves rapidly into the cell, Ca moves slowly into the cell Phase 1 – early repolarization, Na channels close Phase 2 – plateau phase, Ca continues to flow in, K flows out of the cell Phase 3 – rapid repolarization, Ca channels close, K flows out rapidly Phase 4 – resting phase, active transport through the Na-K pump begins restoring K inside and Na outside, cell membrane is impermeable to Na, K may move out of the  The space between phase 2 & 3 represent the S-T segment , phase 3 represent T wave , phase 0& 1 represent the QRS complex. In resting period the potassium ion return back into the cell to have an equilibrium with sodium ion out side the cell represent phase 4 Leads and Their Positions BIPOLAR LEADS L1: has the positive electrode attached to Left arm & negative to Right arm; positive deflection - Helpful in monitoring atrial rhythms and hemiblocks L2 :positive to Left leg & negative to Right arm; positive deflection - commonly used for routine monitoring and detecting sinus node and atrial rhythms L3 : positive to Left leg & negative to Left arm; positive deflection - useful in detecting changes associated Leads and their positions UNIPOLAR Augmented : AVR : positive electrode on the Right arm; no specific view of the heart; negative deflection AVL : positive electrode on the Left arm; electrical activity coming from heart’s lateral wall; positive deflection AVF : positive electrode on the Left leg; electrical activity from the heart’s inferior wall; positive deflection Chest Leads V1- right sternal border, 4th intercostal space V2 – Left sternal border, 4th intercostal space V3 – between v2 & v4 V4 - Left mid clavicular line, 5th intercostal space V5 – Left anterior axillary line , 5th intercostal space V6 – Left mid axillary line, 5th intercostal space ECG Regions THINGS TO PONDER