BRS - Respiratory Physiology_1 Flashcards

Terms Definitions
What is atelectasis?
Alveolar collapse
What is hypoxemia?
Decreased arterial PO2
Can VC be measured by spirometry?
Is fibrosis an example of obstructive or restrictive lung disease?
What is hypoxic vasoconstriction?
Hypoxia causes vasoconstriction (unlike in other organs, where hypoxia causes vasodilation)This directs blood away from poorly ventilated regions
What factors cause the bronchial smooth muscle to contract?
Parasympathetic stimulationIrritantsSlow-reacting substance of anaphylaxis (asthma)
what molecule causes off-loading of O2 from Hb in tissues?
What gases exhibit perfusion-limited exchange?
N2OO2 (under normal conditions)
What is COPD?
A combination of chronic bronchitis and emphysemaObstructive disease with increased lung compliance, so expiration is impairedDecreased FEV1/FVCAir that should be expired is trapped, leading to increased FRC and a barrel-shaped chest
What is hypoxia?
Decreased oxygen delivery to the tissues
What is the inspiratory capacity?
Tidal volume + IRV
Is asthma an example of obstructive or restrictive lung disease?
What is the normal value for FEV1/FVC?
0.8 (80%)
what is the earliest time surfactant is produced in the fetus?
24 weeks
what is the normal FEV1?
80% of the FVC
what happens to physiologic dead space during exercise?
it decreases
What factors cause the oxygen dissociation curve to be shifted to the right (that is, decrease the affinity of hemoglobin for O2)?
Increased PCO2Decreased pHIncreased temperatureIncreased 2,3-BPG concentration
What are "blue boaters?"
COPD patients who primarily have bronchitisSevere hypoxemia with cyanosisHypercapnia because alveolar ventilation is not maintainedRight ventricular failure and systemic edema
How do irritant receptors work?
Found between airway epithelial cellsStimulated by noxious substances
How do J receptors work?
Found in the alveolar wallsEngorgement of pulmonary capillaries stimulates them and causes rapid, shallow breathing
Which of the standard lung volumes is in the lungs at rest?
What is respiratory compliance?
Describes the distensibility of the lungs and chest wallIt is inversely related to elasticity (that is, as elasticity increases, compliance decreases)Inversely related to stiffnessCompliance is the change in volume or a given change in pressure. The higher the compliance, the greater the change in volume for that pressure value
What is the percent saturation of Hb at 100 mmHg (arterial blood)?
100% saturated
what limits gas exchange in emphysema?
surface area is decreased
definition of tidal volume
volume inspired with each normal breath
what is the normal P(O2) in normal humidified tracheal air?
150 mmHg
Formula for minute ventilation
Minute ventilation = tidal volume x (breaths/min)
How is CO2 transported in the blood?
DissolvedBound to hemoglobin (carbaminohemoglobin)Bicarbonate (major form of transport)
What is the A-a gradient?
The difference between arterial and alveolar air PO2 concentrations
What respiratory groups are found in the respiratory medullary centers?
Dorsal respiratory groupVentral respiratory group
What does the pneumotaxic center do?
Inhibits inspiration to regulate respiratory volume and respiration rate
Can TLC be measured by spirometry?
No, because it includes RV
What are the expiratory muscles?
Abdominal muscles -- compress the abdominal cavity and push the diaphragm upwardInternal intercostals -- pull the ribs downNote that these muscles only participate during exercise or when airway resistance is increased due to lung disease
What is the relationship between airway resistance and radius of the airway?
Resistance is inversely proportional to the fourth power of the airway
How do the peripheral chemoreceptors work?
Decreased arterial PO2 causes hyperventilationIncreased arterial PCO2 causes hyperventilationArterial H stimulates the carotid body receptors directly to cause hyperventilation
What is intrapleural pressure?
The pressure outside of the lungs, inside the thoracic cavity
How does surfactant reduce alveolar surface tension?
Disrupts the intermolecular forces between liquid moleculesThis prevents small alveoli from collapsing and increases compliance
what are characteristics of 'blue bloaters?'
primarily bronchitis, have severe hypoxemia with cyanosis, do not maintain alveolar ventilation --> hypercapnia; right ventricular failure and systemic edema. must have productive cough for >3 consecutive months in >= 2 years
What structures perforate the diaphragm and at what levels?
IVC (T8), esophagus (T10), vagus (T10), aorta (T12), thoracic duct (T12), azygous vein (T12).
What causes a left-shift in the Hb-O2 dissociation curve?
decreased P(CO2)increased pHdecreased temperaturedecreased 2,3-DPG
Describe the pressure and perfusion relationships in Zone 1 alveoli
alveolar pressure > arterial pressure > venous pressureQ is greatly decreased, V is decreased and V/Q is increasedblood flow is lowest
what are characteristics of pulmonary fibrosis?
restrictive disease with decreased lung compliance. inspiration is impaired; decrease in ALL lung volumes, FEV1/FVC is increased
definition of IRV
volume that can be inspired over and above the tidal volume (with exercise)
where are the peripheral chemoreceptors for breathing and what stimuli increase breathing rate?
carotid and aortic bodies; decreased P(O2) (if <60mmHg), decreased pH, increased P(CO2)
What causes a right-shift in the Hb-O2 dissociation curve?
increased P(CO2)decreased pHincreased temperatureincreased 2,3-DPG
what is hysteresis
the difference in the P-V curves of inspiration and expiration
What are general characteristics of COPD?
obstructive disease with increased lung compliance. FEV1 is markedly decreased, FVC is decreased, FEV1/FVC is decreased and FRC is increased
Formula for A-a gradient
Gradient = alveolar air PO2 - arterial PO2
What is the V/Q ratio?
The ratio of alveolar ventilation to perfusionIdeal exchange of O2 and CO2 depends upon ventilation and perfusion matching
What type of cardiac shunt is seen in tetralogy of Fallot?
Right to left
What is the tidal volume?
The volume inspired or expired during normal breathing
How is breathing altered in a patient with COPD?
Airway resistance is increasedPatients learn to expire slowly with pursed lipsThis prevents the airway collapse that can occur with a forced expiration
What factors impact the diffusion rates of O2 and CO2?
The partial pressure difference across the membraneThe surface area available for diffusion
What is anatomic dead space?
The volume of the conducting airways, because they do not participate in gas exchangeApproximately 150 ml (or about 1 ml/lb of body weight)
What are the thoracic pressures at rest, before inspiration begins?
Alveolar pressure = atmospheric pressure = 0Intrapleural pressure is negative due to the opposing forces of the lungs trying to collapse and the chest wall trying to expand
what happens to the mean values of arterial P(O2) and P(CO2) during exercise
they do not change
where are left-to-right shunts seen and what is the result?
paten ductus arteriosus or traumatic injury; do not result in decrease in arterial P(O2). most are asymptomatic.
From where does the input to the dorsal respiratory group come?
vagus (chemoreceptors and mechanoreceptors) and glossopharyngeal (chemoreceptors) nerves
Formula for dissolved gas in solution
Dissolved gas = partial pressure of gas x solubility in blood
Can FRC be measured by spirometry?
No, because it includes the residual volume
How does isoproterenol affect bronchodilation?
It is a sympathetic agonist, and this causes the bronchioles to dilate
What is neonatal respiratory distress syndrome?
Occurs in premature infants who have not manufactured sufficient amounts of surfactantThese infants have atelectasis (collapsed lungs), difficulty reinflating the lungs because of decreased compliance, and hypoxemia (decreased V/Q)
What happens to lung compliance in a patient with fibrosis?
Lung compliance decreasesThe tendency of the lungs to collapse is increasedA new, lower FRC is established because the tendency of the lungs to collapse exceeds the tendency of the chest wall to expand
What is the forced expiratory volume?
Abbreviated as FEV1This is the volume of air that can be expired in the first second of a forced maximal expiration
How does lung volume contribute to airway resistance?
Lung tissue exerts radial traction upon the airwaysHigh lung volumes are associated with greater traction and decreased resistanceLow lung volumes exert less traction, and there can be resistance to the point of airway collapse
What are some adaptations to high altitude?
Decreased alveolar PO2, resulting in hypoxemiaHypoxemia stimulates hyperventilationHypoxemia also stimulates RBC production, which increases the Hb concentratio in the bloodMore 2,3-BPG is produced to right-shift the oxygen dissociation curvePulmonary vasoconstriction due to hypoxemia, causing increased pulmonary arterial pressure and hypertrophy of the right ventricle
What is an adaptation to chronic hypoxemia at high altitudes?
Increased production of 2,3-BPG to facilitate oxygen unloading in the tissues
What happens to the thoracic pressures during inspiration?
The inspiratory muscles contract and increase the thoracic volumeThis causes the intrapleural pressure to become more negativeThe increased transmural pressure on the alveoli causes the alveolar pressure to become negativeThe pressure gradient between the alveoli and the air causes air to flow into the lungs
Formula for alveolar air PO2
Alveolar air PO2 = PIO2 - [arterial PCO2 / R)PIO2 = PO2 of the inspired airR = 0.8 usually
What is the order of the alveolar, arterial, and venous pressures (from highest to lowest) in zone 3 of the lung?
Arterial > venous > alveolar
What happens to arterial pressure as you move down the lung?
It increases due to hydrostatic pressure
What is the residual volume?
The volume that remains in the lungs after a maximal expiration
What part of the CNS contains the various centers that neurally control respiration?
Sensory information (PCO2, lung stretch, irritants, etc) is coordinated in the brain stemBrain stem output controls respiratory muscles and the breathing cycle
Why can people tolerate changes in atmospheric pressure and oxygen without compromising the oxygen-carrying capacity of Hb?
Because the oxygen dissociation curve is almost flat between PO2 of 60 and 100 mmHgHowever, below 60, the slope decreases sharply and small decreases in oxygen produce large changes in oxygen-carrying capacity
What is the function of the ventral respiratory group and when is it activated?
function is expiration, activated during exercise
at what point in the breathing cycle is alveolar pressure equal to 0?
at FRC, just before inspiration.
why do patients with COPD expire through pursed lips?
during forced expiration a positive intrapleural pressure is created that collapses the airways. Pursing the lips creates enough back-pressure to maintain airway patency
definition of physiologic dead space
volume of the lungs that does not participate in gas exchange
Calculation of pulmonary vascular resistance?
PVR = [P(pulm artery) - P(wedge)] / Cardiac outupt
What is the inspiratory reserve volume?
The volume that can be inspired beyond the tidal volume
What is the total lung capacity?
The sum of all lung volumes; the volume in the lungs after a maximal inspiration
What do we measure when we want to know about the dynamic compliance of the lungs?
Changes in intrapleural pressure during inspiration
How do the joint and muscle receptors work?
They are activated during limb movementInvolved in the early stimulation of breathing during exercise
Equation for airflow
Q = delta P / RQ = airflowdelta P = pressure gradientR = resistance
What is physiologic dead space?
It is the total dead space (the volume of the lungs that doesn't participate in gas exchange)In normal lungs, physiologic dead space is approximately equal to anatomic dead space, but when there are V/Q defects, it is greater than anatomic dead space
What happens to oxygen and hemoglobin in the lungs?
Oxygen diffuses from alveolar gas to pulmonary capillary bloodThe PO2 of alveolar gas is 100 mmHg, and oxygen affinity of Hb is very high at this concentrationThis facilitates the diffusion processBy tightly binding oxygen, the free oxygen concentration and O2 partial pressure are kept low, which maintains the partial pressure gradient
How does high alveolar pressure affect blood flow in zone 1 of the lung?
It may compress the capillaries and reduce blood flowThis can occur if arterial pressure is decreased from hemorrhageCan also occur if positive-pressure ventilation has artificially increased the alveolar pressure
What is Dalton's law of partial pressure?
Partial pressure = total pressure x fractional gas concentration
Formula for airway resistance
R = (8nl) / (pi x r^4)n = viscosityl = length of airwayr = radius
what is the equation for physiologic dead space?
Vd = Vt * (PaCO2 - PeCO2)/PaCO2
By what is the diaphragm innervated?
phrenic nerve (C3, 4, 5) (keeps the diaphragm alive)
according to Poiseuille's law, what is the relationship between resistance of an airway and the radius?
R is inversely proportional to the r^4
How do the density and viscosity of an inspired gas affect airflow?
They change the resistance to airflowDuring deep-sea diving, air density increases and resistance increasesLow-density gases such as helium reduce airflow resistance
What does the cerebral cortex do (in the context of breathing)?
Allows you to voluntarily control your breathing to a certain extentVoluntary hypoventilation is limiting by increasing PCO2
Describe the state of pressure and lung volume at rest
Lung volume is at FRCPressure in the airways and lungs is equal to atmospheric pressure (0 mmHg)There is a collapsing force on the lungs and an expanding force on the chest wallThese forces are equal and opposite, so the chest-wall system does not collapse or expandThese two opposing forces generate negative intrapleural pressure
which binding site of Hb has the highest affinity for O2? Why is this important?
the fourth binding site --> it allows maximal loading of O2 in the lungs and unloading in the tissues
what happens to the FRC in a patient with emphysema and why?
FRC increases due to increased compliance of the lung. The lung reduces its tendency to collapse and "traps" the air that failed to be expired from a normal cycle.
What are the partial pressures of CO2 and O2 in pulmonary capillaries of obstructed airways?
in a physiologic shunt, Pa values approach venous values: Pa(O2) = 40 mmHg and Pa(CO2) = 46 mmHg
What is the oxygen-binding capacity of blood?
The maximum amount of O2 that can be bound to hemoglobin in the bloodIs dependent upon the hemoglobin concentration of the bloodLimits the amount of O2 that can be carried in the blood
What is the status of gas exchange in a region of the lung that is perfused but not ventilated?
There is no gas exchangeV/Q = 0Therefore, PO2 and PCO2 of the capillary blood approach their values in venous blood
What are the zones of the lung?
Zone 1 -- apex of the lungZone 2 -- middle of the lungZone 3 -- base of the lung
How does airway obstruction alter the V/Q ratio?
V = 0, so V/Q = 0This is a shunt
what is the equation for O2 content of blood?
O2 content = (O2-binding capacity * % saturation) + dissolved O2
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