# Shared Flashcard Set

## Details

Egan's Chapter 10 - Ventilation
Egan's Chapter 10 - Ventilation - SJVC - Romero
80
Physics
10/04/2011

Term
 work In healthy lungs is...
Definition
 work is minimal and performed during the inspiratory phase. Expiration is normally a passive maneuver.
Term
 Pressure Outside Airway Pao
Definition
 is always 0
Term
 Alveolar pressure (Palv), often referred to as
Definition
 intrapulmonary pressure it varies during the breathing cycle
Term
 Pleural pressure (Ppl)  in the fluid of the pleural space is usually
Definition
 negative (i.e., subatmospheric) during quiet breathing.   Ppl also varies during the breathing cycle.
Term
 The trans-respiratory pressure gradient (Prs) represents
Definition
 the difference in pressure between the atmosphere (body surface) and the alveoli: P rs  = P alv  - P bs Note: Pbs same as Pao causes gas to flow in an out of alveoli
Term
 The transpulmonary pressure gradient, or PL, equals
Definition
 the pressure difference between the alveoli and the pleural space, as shown in the following equation: P L  = P alv  - P pl
Term
 PL is
Definition
 the pressure difference that maintains alveolar inflation. (PL is also commonly represented by the symbol PTP.) Note: has to keep pressure just slightly negative at all times P L  = P alv  - P pl
Term
 Pw is the pressure across the chest wall.
Definition
 P w  = P pl  - P bs represents total pressure necessary to expand or contract lungs and chest wall
Term
 During a normal breathing cycle,
Definition
 glottis remains open. Pbs and Pao remain at 0 (i.e., atmospheric)only changes in Palv and Ppl are of interest. Note: only ones that change are alveolar and pleural pressures
Term
 Thoracic expansion causes
Definition
 a decrease in pleural pressure
Term
 The “negative” (i.e., subatmospheric) transrespiratory pressure gradient causes
Definition
 air to flow from the airway opening to the alveoli, increasing their volume.
Term
 end-inspiration
Definition
 alveolar pressure back to 0transpulmonary pressure gradient reaches maximal value≈ −10 cm H2O
Term
 As expiration begins, the thorax
Definition
 recoils and Ppl start to rise
Term
 The transpulmonary pressure gradient narrows and
Definition
 alveoli begin to deflate.
Term
 As the alveoli become smaller
Definition
 alveolar pressure exceeds that at the airway opening
Term
 This positive transrespiratory pressure gradient causes
Definition
 air to flow from the alveoli toward the airway opening. Note: make sure to know which ones go more negative and positive - when
Term
 forces opposing lung inflation
Definition
 elastic forces and frictional forces
Term
 Elastic forces involve
Definition
 tissues of the lungs and thoraxsurface tension in the alveoli
Term
 Frictional forces
Definition
 resistance caused by gas flow and tissue movement during breathing
Term
 Elastic and collagen fibers found in
Definition
 lung parenchyma (lung tissue)
Term
 The tension developed when an elastic structure is stretched
Definition
 proportional to the degree of deformation produced
Term
 The recoil of the lung is
Definition
 a combination of tissue elasticity and its surface tension in the alveoli
Term
 pulmonary surfactant
Definition
 lowers surface tension in the lung
Term
 Alveolar type II cells probably produce
Definition
 pulmonary surfactant
Term
 What opposes lung inflation
Definition
 Tissue elastic forces and surface tension
Term
 Compliance
Definition
 measures the distensibility of the lung
Term
 Measurement of pulmonary compliance in a patient requires
Definition
 placement of a balloon-tipped catheter in the esophagus
Term
 emphysema causes
Definition
 overinflation
Term
 Chest Wall Compliance
Definition
 same volume as lung compliance chest wall wants to expand, lungs want to deflate
Term
 Total Compliance
Definition
 is 0.1L/cmH2O (half of each individual measure
Term
 Frictional (Nonelastic) Opposition to Ventilation
Definition
 tissue viscous resistance and airway resistance.
Term
 Tissue resistance accounts for only approximately
Definition
 20% of the total resistance to lung inflation.
Term
 ascites
Definition
 = fluid in the abdomen
Term
 Airway resistance (Raw) accounts for
Definition
 approximately 80% of the frictional resistance to ventilation.   RAW formula is opposite of compliance formula
Term
Definition
 ranges from approximately 0.5 to 2.5 cm H2O/L/sec
Term
 tracheobronchial
Definition
 same as transitional
Term
 A change in the caliber of an airway by a factor of 2 causes
Definition
 a 16-fold change in resistance
Term
 If the size of a patient's airway is reduced from 2 mm to 1 mm
Definition
 airway resistance increases by a factor of 16!
Term
 if a 4.5-mm tube is replaced with a 9-mm tube, the pressure required to cause a flow of 1 L/sec through the tube will
Definition
 decrease sixteenfold
Term
 Approximately 80% of the resistance to gas flow occurs (where?)
Definition
 in nose, mouth, and large airways, where flow is mainly turbulent
Term
 Resistance to gas flow in nose, mouth, upper airway
Definition
 50%
Term
 Resistance to gas flow in Trachea and bronchi
Definition
 30%
Term
 Resistance to gas flow in small airways (<2 mm)
Definition
 20%
Term
 In airways of healthy subjects, airway collapse occurs only with
Definition
 forced exhalation and at low lung volumes
Term
 The oxygen cost of breathing in healthy individuals averages
Definition
 from 0.5 to 1.0 ml of oxygen per liter of increased ventilationless than 5% of the oxygen consumption of the body.
Term
 Expansion of the lower chest is (less/more?)
Definition
 approximately 50% greater than that of the upper chest.
Term
 bases of lung receive approx four times as much ventilation as
Definition
 apicesBases ventilate morealveoli in bases less open
Term
 Lung units with high compliance have ______ elastic recoil than normal. These units fill and empty ______ than do normal units.
Definition
 less - more slowly
Term
 Lung units with low compliance (high elastic recoil) ______ their volume less. They fill and empty ______ than normal.
Definition
 increase/faster
Term
 A lung unit will have a long time constant if resistance or compliance is ______
Definition
 high
Term
 Lung units have a short time constant when resistance or compliance is ______ .
Definition
 low
Term
Definition
 Note: areas of the lung that don't participate in gas exchange Minute Ventilation   V(dot)E = RR • VT
Term
 Alveolar Ventilation Note: VA = RR x (VT x VD)
Definition
Term
 anatomic dead space and alveolar dead space. When these are considered together, they often are referred to as physiologic dead space.
Definition
Term
 anatomic dead space, or VDanat. VDanat averages approximately 1 ml per pound of ideal body weight (2.2 ml/kg).
Definition
Term
 Ideal Body Weight for a male calculates as: IBW Male = 106 + 6(H" - 60) IBW Female = 105 + 5(H" - 60) answer is in pounds - divide by 2.2 to get kg
Definition
Term
 Alveolar Dead Space alveoli are ventilated but not perfused with mixed venous blood
Definition
Term
Definition
 Anatomic dead space is composed of the conducting tubes leading to both alveoli. Left, Alveolus is normally perfused and ventilated. Right, Alveolus is ventilated but not perfused. The volume represents alveolar dead space. Physiologic dead space is the sum of the two components.
Term
 The volume of gas ventilating unperfused alveoli is called
Definition
Term
 Alveoli at the apices (top corners) of the lungs have how much perfusion?
Definition
 minimal or no perfusion Note: because of gravity - less blood flow
Term
 The sum of anatomic and alveolar dead space is called
Definition
Term
 VDphy is often expressed as a ratio to tidal volume
Definition
 VD/VT = (Paco2 - Peco2)/ Paco2 Note: paco minus peco divided by paco = dead space over tidal volume
Term
 High respiratory rates and low tidal volumes result in
Definition
 a high proportion of wasted ventilation per minute (low V(dot)A). Note: shallow & fast
Term
 most efficient breathing pattern is
Definition
 slow, deep breathing
Term
 normal adult at resting metabolic conditions produces how much CO2 per minute?
Definition
 approximately 200 ml of CO2 per minute.
Term
 Ventilatory Pattern Rate of Breathing (Breaths/min) Tidal Volume (ml) Minute Ventilation (ml) Physiological Dead Space (ml) Alveolar Ventilation (ml)
Definition
 Normal 12 500 6000 150 4200 High rate, low volume 24 250 6000 150 2400 Low rate, high volume 6 1000 6000 150 5100 Increased dead space 12 500 6000 300 2400 Compensation for increased dead space 12 650 7800 300 4200
Term
 hypoventilation
Definition
 Ventilation that does not meet metabolic needs (resulting in respiratory acidosis)
Term
 Hypoventilation is indicated by
Definition
 elevated Paco2 and pH level below normal range (7.35 to 7.45)
Term
 hyperventilation
Definition
 Ventilation in excess of metabolic needs
Term
 hyperpnoea
Definition
 increased breathing rate
Term
 Effectiveness of ventilation
Definition
 determined by the partial pressure of CO2
Term
 Anatomic dead space is composed of the conducting tubes leading to both alveoli. Left, Alveolus is normally perfused and ventilated. Right, Alveolus is ventilated but not perfused. The volume represents alveolar dead space. Physiologic dead space is the sum of the two components.
Definition
Term
 Anatomic dead space is composed of the conducting tubes leading to both alveoli. Left, Alveolus is normally perfused and ventilated. Right, Alveolus is ventilated but not perfused. The volume represents alveolar dead space. Physiologic dead space is the sum of the two components.
Definition
Term
 Anatomic dead space is composed of the conducting tubes leading to both alveoli. Physiologic dead space is the sum of the two components.
Definition
Term
 Pressure at the body surface
Definition
 (Pbs) equal to atmospheric pressure, usually 0
Term
 As pleural pressure rises
Definition
 alveolar pressure also increases
Term
 elastance
Definition
 is the property of resisting deformation
Term
 Compliance is
Definition
 a change in volume over a change in pressure
Term
 Compliance of a healthy adult lung
Definition
 0.2 L/cm H2O, or 200 ml/cm H2O.
Term
 pulmonary fibrosis causes
Definition
 underinflation
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