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Stack #681116
Respiratory A & P Chapter 2 flashcards
| Question | Answer |
|---|---|
| what is ventilation | the process that moves gases between the external environment and the aveoli. mechanism by which oxygen is carried from the atmosphere to the aveloi and by which carbon dioxide is carried from the aveoli |
| Pressure difference across the lungs | relative to the atmospheric pressure and is an essential buling block in the study of ventilation and pulmonary mechanics |
| Pressure gradient | Difference between 2 pressures |
| What is pressure gradient responsible for | moving air in and out of the lung |
| gas always flows from | high to low pressures |
| No gas flows between | 2 equal points |
| Driving pressure | pressure difference between 2 points in a tube or vessel. It is the force moving gas or fluid through the tube or vessel |
| Transairway pressure or transrespiratory pressure | the barometric pressure difference between the mouth pressure Pm and the alveolar pressure (Palv) |
| Transairway pressure is written | Pta = Pm - Palv (mmHg) |
| Transmural pressure | the pressure differences that occur across the airway wall (Ptm) |
| How is the transmural pressure calculated | by subtracting the intra-airway pressure (Piaw) from the Pressure on the outside of the airway (Poaw) |
| Transmural pressure is written | Ptm = Piaw - Poaw |
| Define Positive transmural pressure | Said to exist when pressure is greater within the airway than the pressure outside the airway |
| Define Negative transmural pressure | Said to exist when pressure is greater outside the airway than the pressure inside the airway |
| Transpulmonary pressure | difference between the alveolar pressure (Palv) and the pleural pressure (Ppl) |
| Transpulmonary pressure is writeen | Ptp = Palv - Ppl |
| Transthoracic pressure | (Ptt)the difference between the alveolar pressure (Palv) and the body surface pressure (Pbs) |
| Transthoracic pressure is written | Ptt = Palv - Pbs |
| the flow of gas in and out of the lungs is caused by the | transpulmonary and transairway pressure changes that occur in response to the action of the diaphragm |
| When the diaphragm moves down | thoracic volume increases and intrapleural and intra-alveolar pressure decreases |
| When the diaphragm moves up | Thoracic volume decreases and intraplueral and intra-alveolar pressure increase |
| Define end-inspiration | During inspiration gas from the atmosphere moves down the trachea-bronchial tree until the intra-alveolar pressure ant he barometric pressure are in equalibrium (pre-expiration) |
| Define end-expiration | gas flows out of the lungs until the intra-alveolar pressure and the barometric pressure are once again in equilibrium (pre-inspiration) |
| at rest normal excursion (movement) of the diaphragm is about | 1.5 cm |
| normal intra pleural change is about | 3 to 6 cm H20 pressure (2 to 4 mmHg) |
| during deep inspiration the diaphragm may move | 6 to 10 cm |
| during food expiration the intrapleural pressure may climbe between | 70 and 100 cmH2O above atmospheric pressure |
| when the patient receives a positive pressure breath from a mechanical ventilator... | the intra-alveolar pressure progressively rises above atmospheric pressure |
| during exhalation... | the intra-alveolar pressure decreases toward atmospheric pressure |
| at end-expiration the intra-alveolar pressure is in | equilibrium with atmospheric pressure |
| botht he lungs and the chest wall each have their own | elastic properties |
| the chest wall has a natural tendancy properties of the lung tissue to | move outward or expand as a result of the bones of the thorax and surrounding muscles |
| The lungs have a natural tendancy to | move inward or collapse, because of the natural elastic |
| What is lung compliance | how readily the elastic force of the lungs accepts a volume of inspired air, defined as the change in lung volume per unit pressure change (CL) |
| mathematically lung compliance is expressed in | liters per centimeter of water pressure (L/cm H2O) |
| at rest the average CL for each breath is about | 0.1 L/cm H2O (Approximately 100mL of air is delivered into the lungs per 1 cm H2O pressure change) |
| when lung compliance is increased | the lungs accept a greater volume of gas per unit of pressure change |
| Both in the normal and abnormal lung CL | progressively decreases as the alveoli approach their total filling capacity |
| What is FRC | Functional residual capacity |
| Hooke's law provides another way to explain compliance by describing | the physical properties of an elastic substance |
| What is Elastance | The natural ability of matter to respond directly to force and to return to its original resting position or shape after external force no longer exists (change in pressure per change in volume) |
| Elastance is the reciprocal of | compliance |
| Hookes law states when a truely elastic body | like a spring is acted on by 1 unit of force, the elastic body will stretch 1 unit of length, and when acted on by 2 units of force it will stretch 2 units of length and so forth |
| When Hookes law is applied to the elastic properties of the lungs, volume is substituted for _________ and pressure is substituted for _________ | length, force |
| tension pneumothorax is a condition | if the presssure during mechanical ventilation (positive pressure breath) causes the lung unit to expand beyond its elastic capability the lung unit could rupture allowing alveolar gas to move into intrapleural space and thus causing the lungs to collapse |
| Define surface tension | When a liquid-gas interface exists the liquid molecues at the liquid-gas interface are strongly attracted to the liquid molecues within the liquid mass This molecular cohesive force at the liquid-gas interface is called surface tension |
| surface tension is measured in | dynes per centimeter |
| one dyne/cm is the force necessary to cause | a tear 1 cm long in the surface layer of a liquid. |
| 1 cm H2O pressure equals | 980 dynes/cm |
| laplace's law describes | how the distending pressure of a liquid bubble(not an alveolus) is influenced by (1) the surface tension of the bubble and (2) the size of the bubble itself. |
| WHen laplaces law is applied to a sphere with one liquid-gas interface the equasion is written as | 2 ST P = ---- r where P is the pressure difference (dynes/cm2), ST is surface tension (dynes/cm) and r is the radius of the liquid sphere (cm) The factor 2 is required when the law is applied to a liquid sphere with one liquid-gas interface |
| when laplace's law is applied to a bubble with two liquid-gas interfaces the numerator contains the factor | 4 rather than 2 |
| Laplace's law shows that the distending pressure of a liquid sphere is | directly proportional to the surface tension of the liquid, inversely proportional to the radius of the sphere |
| the numerator of laplaces law shows | as the surface tension of a liquid bubble increases the distending pressure necessary to hold the bubble open increases, or the opposite-- when the surface tension of a liquid bubble decreases, the distending pressure of the bubble decreases |
| the denominator of laplace's law shows tht | when the size of a liquid bubble inccreases the distending pressure necessary to hold the bubble open decreases, or when the size of the bubble decreases the distending pressure of the bubble increases |
| Define critical opoening pressure | the high pressure (With little volume change) that is initially required to overcome the liquid molecular force during the formation of a new bubble |
| Before the bubble is formed the distending pressure is directly proportional to | the radius of the bubble (opposite of what laplace's law states) |
| define critical closing pressure | when the size of the bubble decreases beyond this point, the liquid molecular force of the bubble becomes greater than the distending pressure and the bubble collapses |
| Laplace's law can be restated as | k P = --- r K = constand (surface tension) P = pressure and is inversely proportional to R (radius) Can be stated as Pr = k |
| The liquid film that lines the alveolus resembles | a bubble or sphere |
| when the alveolar fluid is permitted to behave according to its natural tendency, | a high transpulmonary pressure must be generated to keep the small alveoli open |
| Pulmonary surfactand is an important and complex substance that | is produced and stored in the alveolar type II cells |
| Pulmonary surfactant is composed of | phospholipids (about 90 percent) and protein (about 10 percent) |
| the primary surface tension-lowering chemical in pulmonary surfactant is | the phospholipid dipalmitoyl phosphatidylcholine (DPPC) |
| The DPPC molecule at the alveolar gas-liquid interface causes | surface tension to decrease in proportion to its ratio to alveolar surface area |
| it is estimated that surface tension of the average alveolus varies from | 5 to 15 dynes/cm when the alveolus is small to about 50 dynes/cm when the alveolus is full distended |
| what are the 2 major elastic forces in the lungs that cause an inflated lung to recoil inward | the elastic properties of the lungs, the surface tension of the liquid film that lines the alveoli |
| define atelectasis | complete alveolar collapse |
| define dynamic | refers to the study of forces in action |
| in the lungs dynamic refers to | the movement of gas in and out of the lungs and the pressure changes required to move the gas. |
| general causes of pulmonary surfactant deficiency | acidosis, hypoxia, hyperoxia, atelectasis, pulmonary vascular congestion |
| specific causes of pulmonary surfactant deficiency | acute respiratory distress syndrome (ARDS), infant resporatory distress syndrome (IRDS), pulmonary edema, pulmonary embolism, pneumonia, excessive pulmonary lavage or hydration, drowning, extracorporeal oxygenation |
| What structures pierce the diaphragm | vena cava, esophagus, aorta |
| What are the 4 critical life functions in order of importance | Ventilation, Oxygenation, Circulation, perfusion |
| Ventilation includes the movement of air down to and including the | terminal bronchioles |
| the best ways to assess ventilation | Measure PaCO2 |
| Normal PaCO2 is | 35-45 mmHg |
| Any PaCO2 reading below 35 is | hypocapnea |
| hypocapnea is caused by | hyperventilation |
| any PaCO2 reading above 45 is | hypercapnea |
| hypercapnea is caused by | hypoventilation (Failure to ventilate well) |
| How is PaCO2 measured | ABG |
| Oxygenation is | oxygen moving into the blood and transported to the body tissue |
| define external respiration | oxygen getting to the bloodstream |
| define internal respiration | oxygen getting from the blood stream to the body tissues |
| what are 3 ways to measure oxygenation | SpO2, SaO2, PaO2 |
| What are the normals for SpO2, SaO2, and PaO2 | SpO2 and SaO2 norms are 95 to 98% and PaO2 is 80 to 100% |
| What is a critical factor of oxygenation | hemoglobin |
| What are two ways to check circulation | pulse, blood pressure |
| define circulation | movement of blood throughout the body |
| define perfusion | pushing or forcing of oxygenated blood into the tissues |
| shock is | a drop in blood pressure |
| what monitors CO2 levels | Medulla |
| What does FRC stand for | Functional Residual Capacity |
| Define FRC | amount of air left in your lungs following a normal exhalation |
| what creates transairway pressure | diaphragm moving downward |
| diaphragms natural tendency is to | relax and move upward |
| movement of intrathoracic airways tend to what when you breath | dialate when ou breath in and constrict womewhat when you exhale |
| intrapleural pressure is always | sub atmospheric (Negative) |
| compliance is | the ease at which lungs accept air |
| measurement of normal compliance | 100 ml per cm of water |
| during a normal inspiration, intrapleural pressure decreases from its normal resting level which causes the bronchial airways to | lengthen and to increase in diameter (passive dialation) |
| during expiration intrapleural pressure increases which causes the bronchial airways to | decrease in length and in diameter |
| poiseuille's law arranged for flow states | flow is directly proportional to P and r4 and inversely proportional to l and n (Flow will decrease in response to decreased P andn tube radius |
| flow is profoundly affected by | the radius of the tube |
| poiseuille's law arranged for pressure states | pressure is directly proportional to v, l, and n (presssure will increase in response to a decreased tube radius and decreased in response to a decreased flow rate, tube length, or viscosity) |
| pressure is a function of | the radius to the forth power and therefore is profoundly affected by the radius of a tube |
| based on the proportionality for flow, it can be stated that | because gas flow varies directly with r4 of teh bronchial airway, flow must diminish during exhalation because radius of the bronchial airways decreases |
| airway resistance (Raw) | teh pressure difference between the mouth and the alveoli divided by flow rate. |
| normal Raw in the tracheobronchial tree is | about .5 to 1.5 cm H2O/L/sec |
| the movement of gas through a tube or bronchial airway can be classified as | laminar flow, turbulent flow, or a combination of laminar flow and turbulent flow (tracheobronchial flow) |
| define laminar gas flow | gas flow that is streamlined |
| define turbulent flow | gas molecules that move through a tue in random manner |
| tracheobronchial or transitional flow | occurs in the areas where the airways branch. one or the other may be dominant |
| dynamic compliance | clinically how readily a lung region fills with gas during a specific timie period |
| frequency dependent | the alveoli distal to the obstruction do not have enough time to fill to their potiential filling capacity as the breathing frequency increases. The compliance of such alveoli is said to be frequency dependent |
| positive end-expiratory pressure (PEEP) | the pressure in the alveoli distal to the airways with Raw may still be positive when the next inspiration begins |
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