Term
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Definition
| process that moves gases b/t the ext environment & the alveoli. Mechanism by which oxygen is carried from the atmosphere to the alveoli & by which CO2 (delivered to the lungs in mixed venous bld) is carried from the alveoli to the atmosphere |
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Term
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Definition
| the difference b/t 2 pressures |
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Term
| Does gas flow from high to low or low to high |
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Definition
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Term
| What is the pressure gradient when there is no gas flow |
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Definition
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Term
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Definition
| pressure difference b/t 2 points in a tube or vessel; it is the force moving gas/fluid thru the tube or vessel |
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Term
| • Define transairway pressure (Pta) (Also called transrespiratory pressure) including the equation. |
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Definition
barometric pressure difference b/t the mouth pressure (Pm) & the alveolar pressure (Palv)
Equation: Pta = Pm - Palv |
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Term
| The _______ pressure causes air flow in and out of the conducting airways |
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Definition
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Term
| Define transmural (Ptm) pressure including the equation |
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Definition
The pressure differences that occur across the airway wall-calculated by subtracting the intra-airway pressure (Piaw) from the pressure on the outside of the airway (Poaw)
Equation: Ptm = Piaw - Poaw |
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Term
| • What is the difference between positive and negative transmural pressure? |
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Definition
(+) exists when the pressure is greater within the airway than the pressure outside the airway
(-) exists when the pressure is greater outside the airway than the pressure inside the airway |
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Term
| Define transpulmonary pressure including the equation |
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Definition
. Difference b/t the alveolar pressure (Palv) and the pleural pressure (Ppl)
Equation: Ptp = Palv - Ppl |
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Term
| In the normal lung, which is greater Palv or Ppl? |
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Definition
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Term
| Define transthoracic pressure (Ptt) including the equation. |
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Definition
Difference b/t the alveolar pressure (Palv) & the body surface pressure (Pbs)
Equation: Ptt = Palv - Pbs |
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Term
| Is there a difference between Ptt and Pta? |
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Definition
| Technically, no. The Ptt is merely another way to view the pressure differences across the lungs. |
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Term
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Definition
| the portion of a ventilatory cycle at which inspiration stops |
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Term
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Definition
| the portion of a ventilatory cycle at which expiration stops |
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Term
| What happens to the intra-alveolar pressure when the patient receives a positive pressure breath from a mechanical ventilator? |
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Definition
| Progressively rises above atmospheric pressure |
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Term
| What happens to the intra-alveolar pressure during exhalation? |
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Definition
| Decreases toward atmospheric pressure |
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Term
| What are some of the adverse side effects that can occur as a result of administration of positive pressure ventilation? |
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Definition
| Lung rupture and gas accumulation b/t the lungs & chest wall (tension pneumothorax) |
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Term
| The lungs and chest wall each have their own elastic properties. Do these properties work with or against each other? |
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Definition
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Term
| What is the natural tendency of the chest wall? |
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Definition
| Move outward or to expand |
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Term
| What is the natural tendency of the lungs? |
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Definition
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Term
| How are the elastic forces of the lungs evaluated clinically? |
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Definition
| By measuring lung compliance |
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Term
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Definition
| How readily the elastic force of the lungs accepts a volume of inspired air |
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Term
| What mathematical units are used for lung compliance? |
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Definition
| Mathematically, CL is expressed in liters per cm of H2O pressure (L/cm H2O) (CL determines how much air, in liters, the lungs will accommodate for each cm of water pressure change) |
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Term
| What is the average lung compliance at rest? |
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Definition
| 0.1 L/cm H2O (approx. 100 mL of air is delivered into the lungs per 1 cm H2O pressure change |
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Term
| What happens when the lung compliance is increased? |
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Definition
| The lungs accept a greater volume of gas per unit of pressure change |
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Term
| What happens when the lung compliance is decreased? |
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Definition
| The lungs accept a smaller volume of gas per unit of pressure change |
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Term
| Lung compliance progressively __________ as the alveoli approach their total filling capacity. |
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Definition
| Decreases (Both in normal & abnormal lung) |
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Term
| What is the normal compliance of both the lungs and chest wall? |
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Definition
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Term
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Definition
| Functional residual capacity-under normal conditions, the lungs & chest wall recoil to a resting volume |
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Term
| What are some disorders that decrease a patient’s lung compliance? Increase a patient’s lung compliance? |
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Definition
Decrease- Pneumonia, atelectasis, or acute respiratory distress syndrome
Increase- Pneumothorax |
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Term
| Define elastance, including equation |
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Definition
| Natural ability of matter to respond directly to force and to return to its original resting position or shape after the external force no longer exists (change in pressure per change in volume) |
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Term
| What is the relationship of elastance to compliance? |
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Definition
| Reciprocal (opposite) of compliance, (lungs w/high compliance have low elastance and lungs w/low compliance have high elastance) |
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Term
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Definition
| States that when a truly 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. This phenomenon is only true within the elastic body’s normal functional range. When the force exceeds the elastic limits of the substance, the ability of length to increase in response to force rapidly decreases. |
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Term
| Hookes law: If force continues to rise, what will happen? |
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Definition
| The elastic substance will ultimately break |
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Term
| What happens when Hooke’s law is applied to the elastic properties of the lungs? |
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Definition
| Volume is substituted for length and pressure is substituted for force. The lungs behave in a manner similar to the spring, & once the elastic limits of the lung are reached, little or no volume change occurs in response to pressure changes |
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Term
| Hookes law: What will happen if the change in pressure continues to rise? |
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Definition
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Term
| Define tension pneumothorax |
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Definition
| Occurs if the pressure during mechanical ventilation (+ pressure breath) causes the lung unit to expand beyond its elastic capability, the lung unit could rupture, allowing alveolar gas to move into the intrapleural space, thus causing the lungs to collapse |
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Term
| Does the fluid that lines the inner surface of the alveoli affect expansion? If so, how? |
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Definition
| It can profoundly resist lung expansion. |
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Term
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Definition
| When liquid molecules are completely surrounded by identical molecules the molecules are mutually attracted toward one another and, therefore move freely in all directions. Surface tension is when a liquid-gas interface exists, the liquid molecules and the liquid-gas interface are strongly attracted to the liquid molecules within the liquid mass |
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Term
| What is the mathematical unit used for surface tension |
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Definition
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Term
| Define Laplace’s law, including the equation. |
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Definition
| 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. Equation: P= 2ST/ r |
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Term
| What two things does Laplace’s law show for a liquid sphere? |
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Definition
| ? It shows that the distending pressure of a liquid sphere is (1) directly proportional to the surface tension of the liquid and (2) inversely proportional to the radius of the sphere |
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Term
| Using Laplace’s law, what is the relationship of surface tension of a bubble to it’s distending pressure? |
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Definition
| The numerator shows that (1) as the surface tension of a liquid bubble increases, the distending pressure necessary to hold the bubble open increases , or (2)the opposite- when the surface tension of a liquid bubble decreases, the distending pressure of the bubble decreases. The denominator show that (1) when the size of a liquid bubble increases, the distending pressure necessary to hold the bubble open decreases, or (2) the opposite-when the size of the bubble decreases, the distending pressure of the bubble increases. |
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Term
| What is the critical opening pressure? |
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Definition
| The high pressure (w/little volume change) that is initially required to overcome the liquid molecular force during the formation of a new bubble |
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Term
| • What is the relationship of distending pressure to the radius of a bubble? |
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Definition
| Directly proportional to the radius of the bubble (opposite of what Laplace’s law states) |
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Term
| • According to Laplace’s law, does the surface tension vary with the size of the bubble? |
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Definition
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Term
| Define pulmonary surfactant |
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Definition
| An important and complex substance that is produced and stored in the alveolar type II cells. An agent, such as soap or detergent, dissolved in water to reduce its surface tension or the tension at the interface b/t the water and another liquid |
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Term
| What is pulmonary surfactant composed of? |
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Definition
| About 90 % phospholipids and about 10 % proteins |
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Term
| What is the primary surface tension-lowering chemical in pulmonary surfactant? |
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Definition
| The phospholipid dipalmitoyl phosphatidylcholine (DPPC) |
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Term
| What is the difference between hydrophobic and hydrophilic |
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Definition
Hydrophobic- water insoluble
Hydrophilic- water-soluble |
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Term
| What is the natural alveolar surface tension? |
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Definition
| Varies from 5-15 dynes/cm (when the alveolus is very small) to about 50 dynes/cm |
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Term
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Definition
| complete alveolar collapse |
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Term
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Definition
| Refers to the study of forces in action |
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Term
| What does dynamic mean in terms of the lungs |
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Definition
| Refers to the movement of gas in and out of the lungs and the pressure changes required to move the gas |
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Term
| What two things best explain the dynamic features of the lungs? |
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Definition
| (1) Poiseuille’s law for flow and pressure and (2) the airway resistance equation |
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Term
| What happens during inspiration and expiration? |
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Definition
| During inspiration, intrapleural pressure decreases from its normal resting level (about -3 to -6 cm H2O pressure), which causes the bronchial airways to lengthen and to increase in diameter (passive dilation). During expiration, intrapleural pressure increases (or returns to its normal resting state), which causes the bronchial airways to decrease in length and in diameter (passive constriction) |
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Term
| Flow will decrease in response to what? |
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Definition
| In response to decreased P and tube radius (or in response to an increased tube length and fluid viscosity) |
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Term
| Flow will increase in response to what? |
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Definition
| In response to decreased tube length and fluid viscosity (or in response to an increased P and tube radius) |
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Term
| Flow is profoundly affected by what? |
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Definition
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Term
| If pressure remains constant, decreasing the radius of a tube by ½ will reduce the gas flow by ________ of its original flow |
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Definition
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Term
| What is the relationship of pressure to flow, length and viscosity |
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Definition
| ? Pressure will increase in response to a decreased tube radius and decrease in response to a decreased flow rate, tube length, or viscosity. (The opposite is also true: pressure will decrease in response to an increased tube radius and increase in response to an increased flow rate, tube length, or viscosity) |
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Term
| Pressure is profoundly affected by what? |
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Definition
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Term
| Define airway resistance including the equation. |
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Definition
| The pressure difference b/t the mouth and the alveoli (transairway pressure) divided by flow rate |
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Term
| What is the normal airway resistance of the tracheobronchial tree? |
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Definition
| About 0.5 to 1.5 cm H2O/L/sec adults |
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Term
| What are the three types of movement of gas through a tube? |
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Definition
| (1)laminar flow, (2)turbulent flow, or (3)a combination of laminar flow and turbulent flow-called tracheobronchial flow or transitional flow |
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Term
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Definition
| a gas flow that is streamlined. The gas molecules move thru the tube in a pattern parallel to the sides of the tube. This flow pattern occurs at low flow rates and at low pressure gradients |
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Term
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Definition
| gas molecules that move thru a tube in a random manner. Gas flow encounters resistance from both the sides of the tube and from the collision with other gas molecules. This flow pattern occurs at high flow rates and at high pressure gradients |
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Term
| tracheobronchial or transitional gas flow |
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Definition
| Occurs in areas where the airways branch. Depending on the anatomic structure of the branching airways, and the velocity of gas flow, either laminar flow or turbulent flow may predominate |
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Term
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Definition
| A product of airway resistance (Raw) and lung compliance (CL), Defined as the time (in seconds) necessary to inflate a particular lung region to about 60 % of its filling capacity. |
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Term
| What type of lung units require a long time constant? A short/decrease time constant? |
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Definition
Lung regions that have either an increased Raw or an increased CL require more time to inflate-these alveoli are said to have a long time constant.
Lung regions that have either a decreased Raw or a decreased CL require less time to inflate-these alveoli are said to have a short time constant. |
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Term
| Define dynamic compliance clinically and nonclinically. |
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Definition
| A product of the time constants. Defined as the change in the volume of the lungs divide by the change in the transpulmonary pressure (obtained via a partially swallowed esophageal pressure balloon) during the time required for one breath |
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Term
| How is lung compliance measured compared to dynamic compliance |
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Definition
| ? Lung compliance is determined during a period of no gas flow and dynamic compliance is measured during a period of gas flow |
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Term
| In the healthy lung, what is the relationship of dynamic compliance to lung compliance in all breathing frequencies? |
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Definition
| The dynamic compliance is about equal to lung compliance at all breathing frequencies (the ratio of dynamic compliance to lung compliance is 1 : 1) |
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Term
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Definition
| Positive end-expiratory pressure, the pressure in the lungs (alveolar pressure) above atmospheric pressure (pressure outside the body) that exists at the end of expiration |
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Term
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Definition
| Positive end-expiratory pressure caused by inadequate expiratory time |
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Term
| What is the relationship of auto-PEEP to lung compliance and the WOB? |
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Definition
| Air trapping and alveolar hyperinflation (auto-PEEP) decreases lung compliance, causing the WOB to increase |
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Term
| What happens when auto-PEEP produces air trapping and alveolar hyperinflation? |
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Definition
| The pt’s diaphragm is pushed downward; this causes the pt’s inspiratory efforts to become less efficient, causing WOB to increase |
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Term
| what three things compose the ventilator pattern? |
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Definition
| (1)tidal volume (VT), (2)the ventilatory rate, and (3)the time relationship b/t inhalation and exhalation (I : E ratio) |
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Term
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Definition
| The volume of air that normally moves into and out of the lungs in one quiet breath |
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Term
| What is the normal I:E ratio? |
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Definition
| The normal adult ventilatory rate is about 15 breaths per min. The I : E ratio is usually about 1 : 2 (The time required to inhale a normal breath is about ½ the time required to exhale the same breath) |
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Term
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Definition
| The time relationship b/t inhalation and exhalation |
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Term
| What are the three phases of the normal ventilatory cycle? |
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Definition
| (1)the inspiratory phase, (2)the expiratory phase, and (3)the pause phase at end-expiration |
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Term
| Define alveolar ventilation |
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Definition
| The portion of the inspired gas that reaches the alveoli and is effective in terms of gas exchange |
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Term
| Define deadspace ventilation |
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Definition
| The volume of inspired air that does not reach the alveoli and is not effective |
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Term
| What are the three types of dead space? |
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Definition
| (1)anatomic, (2)alveolar, and (3)physiologic |
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Term
| What is anatomic dead space? |
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Definition
| Volume of gas in the conducting airways: the nose, mouth, pharynx, larynx, and lower airways down to, but not including, the respiratory bronchioles |
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Term
| How is minute alveolar ventilation calculated? |
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Definition
(Va) is equal to the tidal volume (VT) minus the dead space ventilation (VD) multiplied by the breaths per minute (frequency)
Va = (VT – VD) X breaths/min |
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Term
| What is alveolar dead space? |
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Definition
| Occurs when an alveolus is ventilated but not perfused with pulmonary blood (Thus, the air that enters the alveolus is not effective in terms of gas exchange b/c theres no pulmonary capillary bld flow) |
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Term
| What is physiologic dead space? |
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Definition
| The sum of the anatomic dead space and alveolar dead space |
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Term
| Which alveoli are expanded more, those in the upper lung regions or lower lung regions? |
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Definition
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Term
| When a patient is in the upright position, where is ventilation usually greater and more effective? |
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Definition
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Term
| What is the ventilatory pattern? |
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Definition
| The respiratory rate & tidal volume presented by an individual |
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Term
| What is the effect of lung compliance on ventilatory rate? Airway resistance on rate? |
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Definition
| When lung compliance decreases, the pt’s ventilator rate generally increases while at the same time, the tidal volume decreases. When airway resistance increases, the pt’s ventilator frequency usually decreases while, at the same time, the tidal volume increases |
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Term
| What two things determine the ventilatory pattern? |
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Definition
| Ventilatory efficiency (to minimize dead space ventilation) and metabolic efficiency (to minimize the work or oxygen cost of breathing) |
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Term
| How can we quantitate the amount of work required to breathe? |
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Definition
| The changes in transpulmonary pressure (force) multiplied by the change in lung volume (distance) (work = pressure X volume) |
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Term
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Definition
| : complete absence of spontaneous ventilation. This causes the PAO2* & PaO2 to rapidly decrease and the PACO2 & PaCO2 to increase. Death will ensue in minutes. |
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Term
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Definition
| normal, spontaneous breathing |
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Term
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Definition
| Short episodes of rapid, uniformly deep inspirations, followed by 10-30 seconds of apnea. First described in pts suffering from meningitis |
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Term
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Definition
| : Increased depth (volume) of breathing w/ or w/o an increased frequency |
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Term
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Definition
| Increased alveolar ventilation (produced by any ventilatory pattern that causes an increase in either the ventilatory rate or depth of breathing) that causes the PACO2 , and therefore, the PaCO2 to decrease |
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Term
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Definition
| Decreased alveolar ventilation (produced by any ventilatory pattern that causes a decrease in either the ventilatory rate or depth of breathing) that causes the PACO2 , and therefore, the PaCO2 to increase |
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Term
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Definition
| A rapid rate of breathing |
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Term
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Definition
| 10-30 sec of apnea, followed by a gradual increase in the volume and frequency of breathing, followed by a gradual decrease in the volume of breathing until another apnea occurs. As the depth of breathing increases, the PAO2 and PaO2 fall and the PACO2 and PaCO2 rise. (Associated w/cerebral disorders and congested heart failure) |
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Term
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Definition
| Both an increased depth (hyperpnea) and rate of breathing. This ventilatory pattern cause the PACO2 and PaCO2 to decline and the PAO2 and PaO2 to increase. (Commonly associated w/diabetic acidosis) |
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Term
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Definition
| A condition in which an individual is able to breathe most comfortably only in upright position |
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Term
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Definition
| Difficulty in breathing, of which the individual is aware |
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