Shelbye's CSON Notes Blog



Respiratory AssessmentGeneral assessment Respiratory function (VITAL)Lung capacities (pulmonary function test)Principles of gas exchangePrinciples of oxygen transportVentilation / Perfusion ratiosREAD ON THESE TOPICS IN CH 21Lung volumes & lung capacities Pulmonary functionBreath soundsGas exchange and oxygen transportVentilation-perfusion ratios Oxyhemoglobin dissociation curve Assessment ReviewFour Factors in Respiratory FunctionNeurochemical control of ventilationMechanics of breathing Gas Transport (diffusion)Control of pulmonary circulationNeurochemical Control of VentilationRespiratory center in the brainstem.- Dorsal respiratory group (DRG) – control rhythm of breathingVentral respiratory group (VRG) – comes into play with excitement (exercise.etc.)Both on a feedback group of the lungs called afferant nervous systemLung ReceptorsIrritant receptors - detect noctious stimuli, broncho irritantStretch receptors – keeps you from over stretching the lungsJ-receptors – juxtapulmonary capillary - associated with the alveoli of the lungs and the cough receptors. AssociatedChemoreceptors - regulatorsMonitor pH, PaCO2, and PaO2.Central chemoreceptors* - monitor changes in arterial blood and CSF. - CO2 readily crosses the BBB. - may be “reset” by long term conditions. -results in poor response to PaCO2 changes.*Constantly detecting changes in CSFMechanics of BreathingMajor and accessory muscles(key components) - diaphragm - external intercostal musclesAveolar Surface Tension (inner lung) - Surfactant - Structure and protects against fluid influx.Elastic Recoil - tendency of the lungs to return to rest. - compromised by high ventilation volumes - diseases create resistance to expansion Compliance - measure of distensibility - determined by aveolar surface tension and elastic recoilAlterations: Aging, emphysema, ARDS, pneumonia, pulmonary edemaWork of Breathing** - muscular effort required for ventilation. - requires oxygen and energy - normally very low - various alterations. - increases oxygen demandHypoxic will cause work of breathing to increaseGas Transport / Pulmonary CirculationDistribution of ventilation and perfusionOxygen transportCarbon dioxide transportImportant capacitiesTidal volume – normal volume with each breath (5-10mL/kg)Minute ventilation – Combination of RR and tidal volume over one minute (4-8 L/min)Vital Capacity – maximum amount of air expired following maximum inhalationInspiratory Force – effort during inspiration. Function Residual CapacityGeneral InspectionPosition.Position of comfort?Effort to breathe.Accessory muscle use.Unequal chest wall movement.Nasal flaring.*pursing lips helps to keep the lungs open naurally Examination of Chest WallSize & shape.AP diameter.Bilateral symmetry.Excursion.Abnormal retraction or bulging.Paradoxical movement.E.g.. Flail Chest.Respiratory Paradox:Abdomen pulled in with every breath. Skin & Mucous Membranes Central Cyanosis.Peripheral Cyanosis.Never assume that O2 levels are okay just because color is okay – varies with Hgb & CO.ClubbingChronic Hypoxic Conditions: Musculoskeletal DevelopmentKyphosis Barrel ChestPectus Carinatum Pectus Excavatum Kyphosis Elevation of scapular & outward curvature of spine. Hunchback. (airtrapping in the back)Barrel ChestIncreased AP diameter of thorax. 1:2 to 5:7*Lackiing in elastic reoil, often seen in COPD also causing air trapping. Eveerything is expanded and stiff Pectus Excavatum (Funnel Chest)Depression in lower portion of sternum.Pectus Carinatum (Pigeon Chest) Sternum protrudes forward.Tracheal PositionNormal.Deviation.Tension PTX.Away from affected side.Severe Atelectasis.Towards affected side.Neck Vein DistentionInspect with HOB elevated.What do the neck veins do with respirations?(COPD)Inspiration:Collapse.Expiration:Distend.Respiratory Rate & QualityEupnea. Normal. WOB.Bradypnea. Rate.Tachypnea (Dyspnea!). Rate & Depth.Hypoventilation. Depth. Irregular.Hyperventilation. Rate & Depth.Respiratory PatternsKussmaul’s: (DKA) Rate, Depth. Labored. Metabolic acidosis.Apnea:Period of cessation of breathing.Cheyne Stokes: (seen in neurological disorders)Alt. periods of deep & shallow, with apnea.Biot or Ataxic: (seen in neurological injuries)No pattern. Irregular with apnea.Tactile Fremitus Vibration of chest wall with vocalization.Increased:Consolidation.Disorders:Decreased:air/unit volume of lung.Disorders: Subcutaneous EmphysemaAir in subcutaneous tissue. (can go anywhere in the body) Causes:Large leak. Ventilator pressure (PEEP). Chest tube (CT) not patent. CT drainage port located beneath the skin & not in pleural space.Res. Auscultation Topics… Normal Breath Sounds.Adventitious Breath Sounds.Transmitted Voice Sounds.Normal Breath SoundsVesicular: Heard over majority of lung fields. Low, soft sound.Bronchovesicular: Heard over the main stem bronchus. Medium pitched. Tracheobronchial: Heard over the trachea only. High pitched & hollow.Adventitious Breath SoundsFine Crackles:Caused by accumulation of fluid, mucus or pus in alveoli & smaller airways.Wheezes:Musical, squeaky sound caused by bronchospasm.Coarse Crackles:Caused by narrowing of the larger airways by mucus or bronchospasm.Pleural Friction Rub:Caused by inflamed pleural membranes rubbing against one another.Diminished Breath Sounds:Breath sounds which are not heard well.Stridor:Crowing sound associated with upper airway obstruction. Often caused by intubationRhonchi:Consolidation sounds: Chest hair:Absent breath sounds: Transmitted Voice SoundsEgophonyBronchophony.Whispered Pectoriloquy.Oxygen TransportReview Concept Topics…Inspiration & ExpirationGas exchangeOxygen transportAlveoliHypoxiaPulmonary ShuntingVentilation-Perfusion RatiosOxyhemoglobin Dissociation CurveInspiration: Active. Diaphragm (60% – 70% Vt). Expiration: Passive.Concepts of gas exchangePartial pressure of a gas dissolved in a liquidGas is dissolved until an equalibrium is a achieved Based on the principle of diffusion (higher to lower concentration) – taking oxygen in diffuses into the cellsConcepts of gas exchangeGas is dissolved until an equilibrium is a achievedBased on the principle of diffusionOxygen and CO2 diffuse readily until equilibrium is achieved.Partial Pressure SymbolsPO2 – Partial pressure of oxygenPAO2 – partial pressure of aveolar oxygenPaO2 – partial pressure of arterial oxygen***PACO2 – partial pressure of aveolar carbon dioxidePaCO2 – partial pressure of arterial carbon dioxide Pulmonary CirculationEntire CO reaches the pulmonary circulation.Low pressure system. (because of fluctuation in fluids that goes to the lungs)Pulmonary artery enters at hilus (sm opening in medial part of lungs). Branch along bronchial structures.Capillary exchange through diffusion.Lung Zones – see additional notes given by Mr. HollandAlveoliApproximately 300 million alveoli – arranged in clusters of 15 – 20. Function: Gas exchange. – Acinus – cluster of alveoliAlveolar CellsType I alveolar cells:Structure. (protect against overloading of fluids)Fluid barrier. Type II alveolar cells:Surfactant. surface tension. Work of breathing. Type III alveolar cells:Macrophages. (cleaners)Effect of Surfactant (decreases surface tension)Lipoprotein Facilitates expansion during inspirationContain macrophage componentsEmpties into lymphatics Hypoxia Alveolar hypoxia pulmonary vasoconstriction.Pulmonary ShuntingBlood that shunts by alveoli without picking up oxygen. Anatomical Shunts: Blood moves from R to L without passing through the lungs. Physiological Shunts:Blood is shunted past alveoli without picking up sufficient amounts of oxygen.Ventilation-Perfusion (V/Q)Ventilation:Flow of gas in & out of lungs.Perfusion:Pulm. capillary blood flow.Gas Exchange:Depends on V/Q ratio.V/Q Balance:Ventilation = Perfusion (1:1).V/Q Imbalance:Ventilation < ≠ > Perfusion.Shunting.V/Q ImbalancePhysiological Shunt (Low V/Q Ratio): PneumoniaAtelectasis TumorsMucous plugAlveolar Dead Space (High V/Q Ratio):PEPulmonary InfarctCardiogenic shockMechanical vent.Silent Unit:Both ventilation & perfusion are decreased.Examples:Pneumothorax Severe ARDSOxygen Transport Oxygen-Hemoglobin Dissociation CurveShift to the Right: acidotic Shift to the Left: alkalotic Putting it togetherVentilation-neurochemical control -mechanics of breathing - elasticity -compliance Perfusion -gas exchange -oxygen transport -CO2 transport -pulmonary circulationAssessing OxygenationSaO2 (Arterial O2 saturation): Hemoglobin O2 saturation.97% is carried by Hgb.Normal > 95%.O2 Carrying Capacity:Hemoglobin: 12 – 18 g/dL.Tissue Perfusion (O2 Delivery):Cardiac Output (CO): 4 – 8 L/min. Heart Rate: 60 – 100 bpm. Stroke Volume: 55 – 100 ml/beat/m2. CO O2 delivered to tissues.However, in normal conditions, approx. only 250 ml of O2 is used per minute.PaO2 / FiO2 Ratio:Normal Lung: > 400 Acute Lung Injury: 200 – 300.ARDS: < 200 is significant. Examples:PaO2 90 mmHg; FiO2 21% = 90 / 0.21 =PaO2 85 mmHg; FiO2 40 % = 85 / 0.40 =PaO2 80 mmHg; FiO2 80 % = 80 / 0.80 = ................
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