Term
| What is the function of the respiratory system? |
|
Definition
| Exchange of CO2 and O2 between the environment and the cells of the body. |
|
|
Term
| What is involved during the inspiratory phase of respiration? |
|
Definition
| Fresh air comes in and oxygen and carbon dioxide are exchanged. |
|
|
Term
| What is involved during the expiratory phase of respiration? |
|
Definition
|
|
Term
| What structures are a part of the conducting zone? |
|
Definition
| Trachea, bronchi, bronchioles |
|
|
Term
| What structures are a part of the respiratory zone? |
|
Definition
| Respiratory bronchioles, alveolar ducts, alveolar sacs |
|
|
Term
| Describe the structure and functions of the conducting zone. |
|
Definition
| Cilia, mucus secreting cells, and smooth muscles line all of the conducting airways. Smooth muscle contains beta 2 receptors->respond to epinephrine to relax walls of airways. Also contain muscarinic receptors which respond to ACh to constrict. (Sympathetic and parasympathetic respectively). Airways filter, warm, and humidify incoming air. |
|
|
Term
| Describe the structure and functions of the respiratory zone. |
|
Definition
| Gas exchange takes place in this zone. Alveoli are evaginations of the bronchioles/ducts/sacs; about 300 million per lung. They have thin walls and large surface area. They contain type I and type II pneumocytes. Macrophages also reside in the alveoli. |
|
|
Term
| What is the difference between type I and type II pneumocytes? |
|
Definition
| Type I pneumocytes are the cells involved in gas exchange in the alveoli, while type II pneumocytes are involved in regeneration and producing surfactant. |
|
|
Term
| Describe pulmonary blood flow (source, distribution, regulation). |
|
Definition
Source: cardiac output from the right ventricle.
Distribution: gravity ensures uneven distribution (better flow at the base than the apex); while supine, the blood flow is even among all the parts of the lung. A small fraction goes to supply the metabolic needs of the bronchi/bronchioles. Regulation: local factors, but mainly the partial pressure of oxygen. |
|
|
Term
| What is tidal volume? What is a typical tidal volume? |
|
Definition
| Normal volume during quiet inspiration OR expiration. Includes the volume of air that fills the alveoli plus the volume that fills the airways. Approximately 500 mL. |
|
|
Term
| What is the inspiratory reserve volume? What is a typical volume? |
|
Definition
| The additional volume that can be inspired above tidal volume; approximately 3,000 mL. |
|
|
Term
| What is the inspiratory capacity? What is a typical volume? |
|
Definition
| Tidal volume + Inspiratory reserve volume. Approximately 3,500 mL. |
|
|
Term
| What is expiratory reserve volume? What is a typical volume? |
|
Definition
| The additional volume that can be expired below tidal volume; approximately 1200 mL. |
|
|
Term
| What is residual volume? What is a typical amount? |
|
Definition
| The volume of gas remaining in the lungs after a maximal forced expiration; approximately 1,200 mL. |
|
|
Term
| What is functional residual capacity? What is a typical volume? |
|
Definition
| Expiratory reserve volume + residual volume. Approximately 2,400 mL. |
|
|
Term
| What is vital capacity? What is a typical volume? |
|
Definition
| Tidal volume + inspiratory reserve volume + expiratory reserve volume. Also: inspiratory capacity +expiratory reserve volume. Approximatley 4,700 mL (500+3,000+1,200). |
|
|
Term
| What is total lung capacity? What is a typical volume? |
|
Definition
| Tidal volume +inspiratory reserve volume + expiratory reserve volume + residual volume. Approximately 6,900 mL. (500+3,000+1,200+1,200). |
|
|
Term
| What constitutes anatomic dead space in the lungs? |
|
Definition
| Conducting airways->no gas exchange can occur here! Approximately 150 mL. |
|
|
Term
| What constitutes physiologic dead space? |
|
Definition
| The volume of lungs that does no participate in gas exchange. There is no gas exchange that occurs within these alveoli. |
|
|
Term
| What are the assumptions when estimating physiologic dead space within a lung? |
|
Definition
1) All CO2 expired comes from exchange in functioning alveoli.
2)No CO2 in inspired air.
3) Physiologic dead space does not contribute CO2.
4) Alveolar CO2 is equal to arterial CO2. |
|
|
Term
| Explain the physiologic dead space equation. |
|
Definition
| The equation states that the volume of the physiologic dead space is the tidal volume multiplied by a fraction. The fraction represents the dilution of alveolar PCO2 by dead space air. |
|
|
Term
|
Definition
| The volume of air moved into and our of the lungs per unit time. |
|
|
Term
| What is minute ventilation? |
|
Definition
| Tidal volume x breaths/minute |
|
|
Term
| What is alveolar ventilation? |
|
Definition
| The minute ventilation corrected for the physiologic dead space: (tidal volume - phys. dead space) x breaths/minute. |
|
|
Term
| Describe the alveolar ventilation equation. |
|
Definition
| If CO2 production is constant, then the partial pressure of CO2 in the alveoli will be determined by alveolar ventilation. Increases in alveolar ventilation cause a decrease in the partial pressure of CO2 in the alveoli, and vice versa. |
|
|
Term
| What is the alveolar gas equation used for? |
|
Definition
| To predict the alveolar PO2 based on the alveolar PCO2. |
|
|
Term
| What is the normal value for the respiratory exchange ratio/respiratory quotient? |
|
Definition
|
|
Term
| What is forced vital capacity? |
|
Definition
| Volume of air that can be forcibly expired after maximal inspiration. |
|
|
Term
| Usually, one can expire entire vital capacity within what amount of time? |
|
Definition
|
|
Term
|
Definition
| The volume one can forcibly expire at 1 sec after a maximal inspiration. |
|
|
Term
| What is the normal ratio for FEV1/FVC? |
|
Definition
|
|
Term
| An obstructive disease such as asthma, chronic obstructive bronchitis, bronchiectasis, and emphysema all result in decreased air flow. What effect do these diseases have on FEV1, FVC, and FEV1/FVC? |
|
Definition
| FEV1: Decreased FVC: Decreased FEV1/FVC: Decreased |
|
|
Term
| Diseases such as fibrosis, severe scoliosis, and pleural effusions can cause restrictive diseases and smaller-than-normal lungs. What effect do these diseases have on FEV1, FVC, and FEV1/FVC? |
|
Definition
| FEV1: Decreased FVC: Decreased FEV1/FVC: Increased |
|
|
Term
| What is the hallmark of a restrictive ventilatory defect? |
|
Definition
| A reduction in lung volume below 80% of predicted value for that patient. |
|
|
Term
| What are the muscles of inspiration? |
|
Definition
| Diaphragm**, external intercostals. Accessory muscles include: SCMs, scalenes, small muscles of the head and neck. |
|
|
Term
| What are the muscles of expiration? |
|
Definition
| Internal intercostals, abdominal muscles |
|
|
Term
| In the lungs, compliance is inversely related to what? |
|
Definition
|
|
Term
| What is compliance as it pertains to the lungs? What is the equation? |
|
Definition
| Describes the distensibility of the lungs. C=V/P. Compliance is a measure of how volume changes as a result of a pressure change. |
|
|
Term
| What does hysteresis refer to? |
|
Definition
| The difference between the lung's inspiratory and expiratory pressure/volume slopes. |
|
|
Term
| What is the compliance of a normal human lung? |
|
Definition
|
|
Term
| T/F Compliance is measured on the inspiration limb of the pressure/volume curve. |
|
Definition
|
|
Term
| What causes the difference in the inspiration and expiration slopes of the compliance relationship? |
|
Definition
| Surface tension at liquid-air interface makes lungs less distensible when beginning inspiration. |
|
|
Term
| What are the consequences of a pneumothorax? |
|
Definition
| Air is introduced into the intrapleural space, and there is no longer a negative pressure keeping the lungs from collapsing. Pressure in the intrapleural space becomes 0, the lungs collapse, and the chest wall springs outward. |
|
|
Term
| What is the result of the situation where the collapsing force on the lungs and the expanding force on the chest wall are equal and opposite? |
|
Definition
| This situation occurs when the lungs are at rest; the combined chest-wall system neither wants to collapse or expand, and there is a negative intrapleural pressure. |
|
|
Term
| Describe the effect of emphysema on the pressure volume slopes of the chest wall-lung system. |
|
Definition
| Emphysema is associated with loss of elastic fibers; this leads to increased slope of lunge volume vs. pressure. There is a higher FRC. |
|
|
Term
| What is the result of a forced expiration on the pressure-volume curve of the chest wall-lung system? |
|
Definition
| Lower FRC; b/c the collapsing pressure is less, the expanding force on the chest wall is greater and the system 'wants' to expand. |
|
|
Term
| What is the result of a higher FRC on the pressure-volume curve of the chest wall-lung system? |
|
Definition
| There is more volume in the lungs than there is at equilibrium, and the collapsing (elastic) force of the lungs is greater. The expanding force on the chest wall is less. |
|
|
Term
| Does emphysema accompany an increased or decreased compliance of the lungs? |
|
Definition
| Increase (inverse relationship b/t compliance and elastance). |
|
|
Term
| Does fibrosis accompany an increase or decrease in compliance? |
|
Definition
| Decrease (greater elastance- inverse relationship). |
|
|
Term
| What effect does fibrosis have have on the pressure-volume loop of the chest wall-lung system? |
|
Definition
| Decreased slope and a lower FRC. |
|
|
Term
|
Definition
| The force of attraction b/t liquid molecules at surface of a solution in contact with gas. |
|
|
Term
| Do small or large alveoli have a tendency to collapse because of surface tension? |
|
Definition
|
|
Term
| What is dipalmitoyl phosphatidyl choline? |
|
Definition
|
|
Term
|
Definition
| It promotes the stability of alveoli of differing sizes and prevents alveolar collapse. The low surface tension of the alveoli increases the compliance of the lung and reduces the work it takes to expand them with each breath. |
|
|
Term
| What is neonatal respiratory distress syndrome? |
|
Definition
| It is a condition due to the lack of surfactant which causes atelectasis/difficulty inflating the lungs. Fetal synthesis of surfactant is variable, usually b/t 24-35 weeks. |
|
|
Term
| How is fetal synthesis of surfactant tested? |
|
Definition
| Measure the ratio of lecithin:sphingomyelin in amniotic fluid. Ratio >2 reflects mature levels of surfactant. |
|
|
Term
| What is the equation relating (collapsing) pressure to surface tension and radius? |
|
Definition
|
|
Term
| What is the equation relating airflow to pressure and resistance? |
|
Definition
|
|
Term
| What is the greatest site of resistance in the lungs? |
|
Definition
|
|
Term
| Describe sympathetic and parasympathetic effects on the airways. |
|
Definition
| Sympathetic: Beta 2 receptors respond to epinephrine and relax. Parasympathetic: Muscarinic receptors respond to ACh and constrict. |
|
|
Term
| An increase in the viscosity of air does what to resistance? |
|
Definition
|
|
Term
| High lung volumes are associated with high or low resistance? |
|
Definition
|
|
Term
| Low lung volumes are associated with high or low resistance? |
|
Definition
|
|
Term
| What is the general gas law? |
|
Definition
| PV=nRT P=pressure, V=volume, n=moles (constant), R=gas constant, and T=37 degrees. |
|
|
Term
| What does Boyle's law state? |
|
Definition
| At a given temperature, the product of pressure x volume is a constant. P1xV1=P2xV2. |
|
|
Term
| What occurs during inspiration? |
|
Definition
| The muscles of the diaphragm contract and volume of the thorax increases. Intrapleural and thus alveolar pressure decrease; the pressure gradient causes air to flow into the lung. |
|
|
Term
| What occurs during expiration? |
|
Definition
| Alveolar pressure becomes greater than atmospheric; elastic forces of the lungs compress gas and air flows out. |
|
|
Term
| What is Dalton's law of partial pressure (of dry gas and humidified gas)? |
|
Definition
Dry: Px=PB x F
Humidified gas: Px=(PB-PH2O) x F
Where Pb is barometric pressure and F is the fractional concentration of gas. |
|
|
Term
| What is Henry's law for dissolved gases? |
|
Definition
| It states that the partial pressure of a gas in the liquid phase is equal to the partial pressure of the gas in the gas phase. Cx=Px x solubility |
|
|
Term
| According to Henry's law, if alveolar air is 100 mm Hg, then capillary blood will have a pressure of what? |
|
Definition
|
|
Term
| What is Fick's law of diffusion? |
|
Definition
| Vx=DAdeltaP/deltaX Vx=volume of gas transferred per unit time; D=diffusion coefficient of the gas; A=surface area; delta P= partial pressure difference; delta X= thickness of the membrane |
|
|
Term
| What is the driving force for diffusion of a gas across a membrane? |
|
Definition
| Partial pressure difference (NOT concentration) |
|
|
Term
| What is lung diffusing capacity (DL)? |
|
Definition
| DL combines the diffusion coefficient of gas, the surface area of the membrane, and the thickness of the membrane. It is the time for gas to combine with proteins. |
|
|
Term
| What gas measures lung diffusion capacity? |
|
Definition
|
|
Term
| How does emphysema, fibrosis, anemia, and exercise effect lung diffusing capacity? |
|
Definition
| Emphysema- decreases b/c destruction of alveoli results in a decreased surface area for gas exchange. Fibrosis/pulmonary edema- DL decreases b/c the diffusion distance increases (membrane thickness). Anemia- decreases b/c the amt of hemoglobin in RBCs is reduced. Exercise- DL increases b/c additional capillaries are perfused with blood, which increases the surface area for gas exchange. |
|
|
Term
| What are three different ways gases are carried in solution? |
|
Definition
| 1) Dissolved gas (higher the solubility of the gas, the higher the concentration in solution; only dissolved gas contributes to partial pressure). 2) Bound gas- hemoglobin and plasma proteins. 3) Chemically modified gas (CO2 converts to HCO3- via carbonic anhydrase). |
|
|
Term
| What is the difference b/t diffusion and perfusion limited gas exchange? |
|
Definition
| Diffusion limited gas exchange- total gas exchange is limited by the diffusion process. Perfusion limited gas exchange- total gas exchange limited by blood flow through capillaries. |
|
|
Term
| What are examples of diffusion and perfusion limited gas exchange? |
|
Definition
| Diffusion limited gas exchange- CO, O2 during strenuous exercise, emphysema, fibrosis, and high altitude. Perfusion limited exchange- O2 transfer at rest, CO2, blood flow. |
|
|
Term
| How oxygen transported in the blood? |
|
Definition
| Dissolved and bound to hemoglobin (increases oxygen-carrying capacity 70 fold). |
|
|
Term
| How is oxygen carrying capacity calculated? |
|
Definition
| O2=(O2 binding capacity x % saturation) + dissolved O2 |
|
|
Term
| What is the structure of hemoglobin? |
|
Definition
| 4 subunits of globular proteins and heme which contains ferrous iron (Fe2+). |
|
|
Term
| Oxygen binding is dependent primarily on what? |
|
Definition
|
|
Term
| What is cooperativity in binding? |
|
Definition
| Affinity b/t hemoglobin and oxygen changes with the addition of each oxygen->facilitates loading in lungs and tissues. |
|
|
Term
| What causes a left shift in the dissociation curve of oxygen and hemoglobin? |
|
Definition
| When affinity is increased; for any given PO2 level, saturation is increased and unloading is more difficult. Occurs when there is a decrease in PCO2 and and increase in pH, decrease in temperature, decrease in 2,3-DPG concentration, and the presence of hemoglobin F. |
|
|
Term
|
Definition
| Byproduct of deoxyhemoglobin which binds to the beta chains and reduces their affinity for O2 (easier to deliver oxygen to tissues). |
|
|
Term
| What causes a right shift in the dissociation curve of oxygen and hemoglobin? |
|
Definition
| Right shifts occur when affinity of Hb for O2 is decreased (for any PO2 level, saturation is decreased and unloading is easier). Occurs when there are increases in PCO2, decreases in pH, increases in temperature, increases in 2,3-DPG. |
|
|
Term
| How is most of the CO2 in the blood transported? |
|
Definition
| Bicarbonate- hydration of CO2 in RBCs via carbonic anhydrase. |
|
|
Term
| Bicarbonate is exchanged for what to go to and from RBCs into the blood? |
|
Definition
|
|
Term
|
Definition
| Increased hydrogen ions cause O2 o dissociate more easily. Deoxygenated hemoglobin can bind excess hydrogen ions, which buffers better than oxyhemoglobin. |
|
|
Term
| What occurs in the pulmonary vasculature in the case of decreased PAO2? |
|
Definition
| Hypoxic vasoconstriction (for better V/Q matching). |
|
|
Term
| Thromboxane A2, prostacyclin, and leukotrienes have what effects in the pulmonary vasculature? |
|
Definition
| Thromboxane A2 and leukotrienes are both vasoconstrictors. Prostacyclin is a vasodilator. |
|
|
Term
| Which region of the lung is best ventilated? |
|
Definition
|
|
Term
| Which region of the lung has the best perfusion? |
|
Definition
|
|
Term
| What does a high V/Q ratio mean? Where is this often found? |
|
Definition
| A high level of ventilation relative to the perfusion. Often found at the apices of the lungs. |
|
|
Term
| Blood flow is driven by what in zone 2 of the lungs? |
|
Definition
| The difference in arterial and alveolar pressures. |
|
|
Term
| Blood flow is driven by what in zone 3 of the lungs? |
|
Definition
| The difference in arterial and venous pressures. |
|
|
Term
| What does a low V/Q ratio mean? Where is it often found? |
|
Definition
| A low level of ventilation relative to the perfusion. Often found at the base of the lungs. |
|
|
Term
| What is the normal value for the V/Q ratio? |
|
Definition
|
|
Term
| If V/Q ratio is normal, what will PaO2 and PaCO2 be? |
|
Definition
| 100 mm Hg and 40 mm Hg respectively. |
|
|
Term
| Airway obstruction causes what kind of V/Q deficit? |
|
Definition
| V/Q will be 0, PaO2 will be 40, PaCO2 will be 46 mm Hg. |
|
|
Term
| A pulmonary embolus will cause what kind of V/Q deficit? |
|
Definition
| There will be no blood flow, and therefore no perfusion, but regular ventilation. Therefore, PAO2 will be 150 and PACO2 will be 0. |
|
|
Term
|
Definition
| Brain stem control centers, chemoreceptors, mechanoreceptors, and respiratory muscles. |
|
|
Term
| Where is the inspiratory center found? |
|
Definition
| In the medulla respiratory center->reticular formation. Also called the dorsal respiratory group. It generates the basal rhythm of breathing; it has input from CN IX and X. Its output is via the phrenic nerve to the diaphragm. |
|
|
Term
| Where is the expiratory center found? |
|
Definition
| Medullary respiratory center->reticular formation. Also called the ventral respiratory group. It is responsible for expiration and is not active during normal, quiet breathing. It is activated when expiration becomes active. |
|
|
Term
| What is the apneustic center? Where is it located? |
|
Definition
| It stimulates inspiration/inspiratory gasps; prolongs contraction of the diaphragm. Located in the lower pons. |
|
|
Term
| What is the pneumotaxic center? Where is it located? |
|
Definition
| It turns off inspiration and limits the size of tidal volume. Located in the upper pons. |
|
|
Term
| What role does the cerebral cortex play in controlling breathing? |
|
Definition
| It can temporarily override brain stem stimulation; responsible for voluntary hyperventilation and hypoventilation. |
|
|
Term
| Where are central chemoreceptors located? What do they primarily respond to? |
|
Definition
| Located in brainstem; directly respond to changes in pH of CSF (an indirect response to change in PaCO2). |
|
|
Term
| Where are peripheral chemoreceptors located? What primarily stimulates them? |
|
Definition
| Located in the carotid bodies at the bifurcation of the common carotid arteries and in the aortic bodies above and below the aortic arch. Responds to O2, CO2, and H+. |
|
|
Term
| What nerves are responsible for input from peripheral chemoreceptors? |
|
Definition
|
|
Term
| What occurs when central chemoreceptors detect a decrease in CSF pH? |
|
Definition
|
|
Term
| What occurs when central chemoreceptors detect an increase in CSF pH? |
|
Definition
|
|
Term
| What is the most important factor that will stimulate the carotid bodies? |
|
Definition
| PaO2- primarily only when PaO2 drops to below 60 mm Hg. Responsible for hypoxic ventilatory drive. *Increase in CO2 is less important than O2 sensing or central chemoreceptor response to CO2. |
|
|
Term
| What is the Hering/Breuer reflex? |
|
Definition
| Distension of lungs causes an increase breathing rate (detected by lung stretch receptors and transmitted via CN X). |
|
|
Term
| What do irritant receptors do? |
|
Definition
| Located in the airways; stimulated by noxious substances. They are responsible for a reflex constriction of bronchial smooth muscles, cough reflex, and an increase in breathing rate. |
|
|
Term
| What are J receptors? Where are they located? |
|
Definition
| "Juxtacapillary" receptors detect engorgement of capillaries and stimulate rapid, shallow breathing. |
|
|
Term
| What do joint and muscle receptors do? |
|
Definition
| They are activated by limb movement and cause early stimulating of rapid breathing during activity. |
|
|
Term
| T/F Mean values for O2 and CO2 change during exercise. |
|
Definition
| False- venous PCO2 must increase, but increased ventilation eliminates excess. |
|
|
Term
| How does exercise affect the O2-hemoglobin dissociation curve? |
|
Definition
| Shifts it to the right, increases P50, and decreases affinity b/t O2 and Hgb. |
|
|
Term
| How does exercise affect pulmonary blood flow? |
|
Definition
| Because cardiac output increases, pulmonary blood flow increases also. V/Q is more even, and there is less physiologic dead space. |
|
|
Term
| What effect does high altitude have on pH of the blood? |
|
Definition
|
|
Term
| How does high altitude affect the O2-Hgb dissociation curve? |
|
Definition
| Shifts to the right; increase in 2,3-DPG, increased P50, and decreased affinity b/t O2 and Hgb. |
|
|
Term
| What are four adaptive responses to high altitude? |
|
Definition
| 1) Hyperventilation- PO2<60 mm Hg- peripheral chemoreceptors are stimulated. 2) Polycythemia- kidney produces eyrthropoietin which stimulates RBC proliferation->increases O2 content of blood. 3) O2-Hgb dissociation curve shifts to the right which enables O2 unloading at tissues. 4) Pulmonary vasoconstriction- low PO2 causes vvasoconstriction. Right heart must pump against increased pulmonary resistance and may hypertrophy over time. |
|
|
Term
| What is the difference b/t hypoxia and hypoxemia? |
|
Definition
| Hypoxia- decreased delivery or decreased utilization of O2. Hypoxemia- decrease in arterial PO2; can be one cause of hypoxia. |
|
|
Term
| What are some causes of hypoxemia? |
|
Definition
| High altitude, hypoventilation, diffusion defect, V/Q defect, right to left shunt defect. |
|
|
Term
| What is an example of a physiologic shunt? |
|
Definition
| Bronchial blood flow (about 2% of cardiac output) bypasses alveoli. |
|
|
Term
| Explain right to left shunts. |
|
Definition
| Blood goes from the right side of the heart to the left side of the heart without going to the lungs. Hypoxemia always occurs and cannot be corrected by breathing high concentration O2. Does not lead to big changes in PaCO2. |
|
|
Term
| What are left to right shunts? |
|
Definition
| They are more common; oxygenated blood from the left heart goes to the right heart to go back through the lungs. No hypoxemia results; ex: patent ductus arteriosus. |
|
|
Term
|
Definition
| The difference b/t PAO2 of alveolar gas and PaO2 of systemic arterial blood. A-a=(PIO2-(PACO2/R))-PaO2 |
|
|
Term
| How is the A-a estimated as the gradient changes with advancing age? |
|
Definition
| Estimated as 1/4 of the pt's age in years. An increased gradient signifies problems with oxygen transfer in the lung. |
|
|
Term
| How does high altitude and hypoventilation affect A-a gradient? |
|
Definition
| Normal A-a gradient; both PAO2 and PaO2 are similar in both situations. |
|
|
Term
| How does V/Q defects affect A-a gradient? |
|
Definition
| Increases gradient; always lead to hypoxemia. Supplemental oxygen raises the PO2 in low V/Q regions where blood flow is the highest. |
|
|
Term
| What is hypoxia caused by? |
|
Definition
| Decreased cardiac output, decreased oxygen content (hypoxemia, anemia, CO poisoning), and CN poisoning. |
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|
