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Respiratory Physiology > Lexicon Terms > Flashcards

Lexicon Terms Flashcards

1
Q

Alveolar Dead Space

A

is represented by alveoli that are ventilated (air is moving in and out) but that are poorly perfused with blood. Alveolar dead space changes with varying metabolic requirements in normally functioning animals.

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2
Q

Alveolar Ducts

A

are completely lined with alveoli, but contain no cilia and little smooth muscle.

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3
Q

Alveolar Gas Equation

A

is used to predict the alveolar PO2, based on the alveolar PCO2 . The alveolar gas equation is expressed as:
PAO2 = PIO2 – PACO2/R + correction factor, where PAO2 = alveolar PO2; PIO2 = PO2 in inspired air; PACO2 = Alveolar PCO2; and, R = respiratory exchange ratio.

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4
Q

Alveolar Macrophages

A

are phagocytic cells contained within the alveoli. They keep the alveoli free of dust and debris since the alveoli have no cilia to perform this function. They also have regenerative capacity for the type I and type II pneumocytes.

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5
Q

Alveolar Sacs

A

are the outpouchings of groups of alveoli

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6
Q

Alveolar Surface Tension

A

The small size of alveoli presents a special problem in keeping them open. Alveoli are lined with a film of fluid. The attractive forces between adjacent molecules of the liquid are stronger than the attractive forces between molecules of liquid and molecules of gas in the alveoli, which creates a surface tension. As the molecules of liquid are drawn together by the attractive forces, the surface area becomes as small as possible, forming a sphere. The surface tension generates a pressure that tends to collapse the sphere. The pressure generated by such a sphere is given by the Law of LaPlace (P = 2T/r).

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7
Q

Alveolar Ventilation

A

is the minute ventilation corrected for the physiologic dead space:
VA = (VT – VD) x breaths/minute

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8
Q

Alveolar Ventilation Equation

A

The alveolar ventilation equation defines the inverse relationship between alveolar ventilation and alveolar PCO2

PACO2 = VCO2 x K/VA.

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9
Q

Alveoli

A

are pouch-like evaginations of the walls of the respiratory bronchioles, the alveolar ducts, and the alveolar sacs.

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10
Q

Anatomic Dead Space

A

is the volume of the conducting airways, including the nose (and/or
mouth), trachea, bronchi, and bronchioles. It does not include the respiratory bronchioles and
alveoli.

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11
Q

Anemia

A

a reduction below normal in the number of erythrocytes per cubic millimeter, in the
quantity of hemoglobin, or in the volume of packed red blood cells per 100 mls of blood.

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12
Q

Apnea

A
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13
Q

Atelectasis

A

Collapse of the small airways and alveoli which are not ventilated and therefore do
not participate in gas exchange.

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14
Q

Bohr Effect

A

When tissue metabolic activity increases, the production of CO2 increases. This
results in an increase in tissue acid content and a corresponding decrease in pH. Increased CO2
and lowering of the pH reduce the affinity of hemoglobin for oxygen, shifting the oxygenhemoglobin
dissociation curve to the right. This facilitates the unloading of oxygen from
hemoglobin in the tissues. This mechanism helps to ensure that oxygen delivery can meet
oxygen demand. The effect of CO2 and pH on the oxygen-hemoglobin dissociation curve is
referred to as the Bohr effect.

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15
Q

Boyle’s Law

A

At a given temperature, the product of pressure and volume of a gas is constant:
P1V1 = P2V2

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16
Q

Bronchial Circulation

A

is the blood supply to the conducting airways (which do not participate
in gas exchange) and is a very small fraction of the total pulmonary blood flow.

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17
Q

Carbaminohemoglobin

A

When CO2 binds to hemoglobin, it is referred to as
carbaminohemoglobin

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18
Q

Carbonic Anhydrase

A
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19
Q

Carboxyhemoglobin

A

Carbon monoxide binds to hemoglobin with an affinity that is 250 times
that of oxygen to form carboxyhemoglobin.

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20
Q

Chemoreceptors

A

The brainstem controls breathing by processing sensory (afferent)
information and sending motor (efferent) information to the diaphragm.

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21
Q

Compliance

A

describes the distensibility of the chest wall and lungs). Compliance defines the
pressure-volume relationship of the lung.

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22
Q

Conducting Zone (or Conducting Airways)

A

includes the nose, nasopharynx, larynx, trachea,
bronchi, bronchioles, and terminal bronchioles. These structures function to bring air into and out
of the respiratory zone for gas exchange and to warm, humidify, and filter the air before it
reaches the critical gas exchange region.

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23
Q

Cor pulmonale

A
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24
Q

Dalton’s Law of Partial Pressures

A

The partial pressure of a gas in a mixture of gases is the pressure that gas would exert if it occupied the total volume of the mixture

Px = PB x F, where Px = partial pressure of gas, PB = barometric pressure, and F = fractional concentration of gas.

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25
Q

Dead Space

A

is that volume of the airways and lungs that does not participate in gas exchange. Dead space is a general term that refers to both the actual anatomic dead space of the conducting airways and a functional, or physiologic, dead space.

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26
Q

Deoxyhemoglobin

A

Acid in the blood (academia) is buffered in the red blood cells by deoxyhemoglobin and is carried in the venous blood in this form.

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27
Q

Elastance

A

The compliance of the lungs and chest wall is inversely correlated with their elastic properties or elastance.

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28
Q

Emphysema

A

is associated with loss of elastic fibers in the lung and increases in compliance.

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29
Q

Expiratory Reserve Volume

A

The additional volume that can be expired below tidal volume is called the expiratory reserve volume.

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30
Q

Fibrosis

A

Is associated with stiffening of the lung and decreased compliance.

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31
Q

Fick’s Law

A

For gases, the rate of transfer by diffusion is directly proportional to the driving force, a diffusion coefficient, and the surface area available for diffusion. It is inversely proportional to the thickness of the membrane barrier:

Vx = D x A x ΔP/ΔX where V is the volume of gas transferred per unit time, D is the diffusion coefficient of the gas, A is the surface area, ΔP is partial pressure difference of the gas, and ΔX is the thickness of the membrane.

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32
Q

Forced Expiratory Capacity

A

is the total volume of air that can be forcibly expired after a maximal inspiration.

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33
Q

Functional Residual Capacity

A

FRC is composed of the expiratory reserve volume plus the residual volume. FRC is the volume remaining in the lungs after normal tidal volume is expired and can be thought of as the equilibrium volume of the lungs.

34
Q

Gas Exchange

A

Gas exchange in the respiratory system refers to diffusion of O2 and CO2 in the lungs and in the peripheral tissues. O2 is transported from alveolar gas into pulmonary capillary blood and, ultimately, delivered to the tissues, where it diffuses from systemic capillary blood
into the cells. CO2 is delivered from the tissues to venous blood, to pulmonary capillary blood, and is transferred to alveolar gas to be expired.

35
Q

Gas Transport

A

O2 is carried in two forms in blood: dissolved and bound to hemoglobin. Dissolved O2 alone is inadequate to meet the metabolic demands of the tissues; thus, a second form of O2 , combined with hemoglobin, is needed.

36
Q

General Gas Law

A

The product of pressure and volume of a gas is equal to the number of moles of the gas multiplied by the gas constant multiplied by the temperature:
PV = nRT where P is pressure, V is volume, n is moles of gas, R is the gas constant, and T is temperature.

37
Q

Hemoglobinemia

A

Is the presence of excessive hemoglobin in the plasma of blood

38
Q

Hemoglobin A (HbA)

A

Hemoglobin is a globular protein consisting of four subunits. Each subunit contains heme, and a polypeptide chain, which is designated either α or β. Adult hemoglobin (HbA) has an α2β2 conformation. Each subunit can bind one molecule of O2, for a total of four molecules of O2 per molecule of hemoglobin. When hemoglobin is oxygenated, it is called oxyhemoglobin; when it is deoxygenated it is called deoxyhemoglobin.

39
Q

Hemoglobin F (HbF)

A

is fetal hemoglobin. In fetal hemoglobin (HbF), the two β chains are replaced by γ chains, giving it the designation of α2γ2. The physiologic consequence of this modification is that HbF has a higher affinity for oxygen than HbA, facilitating movement of oxygen from the mother to the fetus. HbF is the normal variant present in the fetus and is replaced by HbA within the first year of life.

40
Q

Hemoglobin S (HbS)

A

is an abnormal variant of hemoglobin that causes sickle cell disease.

41
Q

Henry’s Law

A

The concentration of dissolved gas in blood is equal to the partial pressure of gas times its solubility:
Cx = Px x solubility, where Cx = concentration of dissolved gas, Px = partial pressure of gas, and solubility is the solubility of gas in blood.

42
Q

Hypercapnea

A

Is an excess of carbon dioxide in the blood.

43
Q

Hypercarbia

A

Is an excess of carbon dioxide in the blood.

44
Q

Hyperpnea

A

Is an abnormal increase in the depth and rate of the respiratory cycle.

45
Q

Hypocapnia

A
46
Q

Hypocarbia

A

Is a deficiency of carbon dioxide in the blood, resulting from hyperventilation and leading to alkalosis.

47
Q

Hyperventilation

A

Is a state in which there is an increased amount of air entering the pulmonary alveoli resulting in reduction of PCO2 and eventually leading to alkalosis

48
Q

Hypoventilation

A

Is a state in which there is a reduced amount of air entering the pulmonary alveoli.

49
Q

Hypoxemia

A

is defined as a decrease in arterial partial pressure of oxygen. The five (5) major causes of hypoxemia are high altitude, hypoventilation, diffusion defects, V/Q mismatch, and right-to-left shunts.

50
Q

Hypoxia

A

is defined as a decrease in oxygen delivery to, or utilization by, the tissues. Hypoxemia is one cause of tissue hypoxia, although it is not the only cause.

51
Q

Hypoxic Vasoconstriction

A

In the lungs, hypoxic vasoconstriction is an adaptive mechanism, reducing pulmonary blood flow to poorly ventilated areas where the blood flow would not be used efficiently. Thus, pulmonary blood flow is directed away from poorly ventilated regions of the lung, where gas exchange would be inadequate, and toward well-ventilated regions of the lung, where gas exchange would be more optimal

52
Q

Hysteresis

A

In a pulmonary pressure-volume curve, the slopes of the relationships for inspiration and expiration are different, a phenomenon referred to as hysteresis.

53
Q

Inspiratory Capacity

A

is composed of the tidal volume plus the respiratory reserve volume.

54
Q

Inspiratory Reserve Volume

A

The additional air that can be inspired above tidal volume is called the inspiratory reserve volume.

55
Q

Law of LaPlace

A

The pressure generated by a sphere is given by the Law of LaPlace. The pressure of a sphere equals 2 x tension divided by the radius of the sphere; P = 2T/r.

56
Q

Metabolic Acidosis

A

is caused by a decrease in HCO3- concentration that, according to the Henderson-Hasselbalch equation, leads to a decrease in pH.

57
Q

Metabolic Alkalosis

A

is caused by an increase in HCO3- concentration that, according to the Henderson-Hasselbalch equation, leads to an increase in pH.

58
Q

Methemoglobin

A

If the iron component of the heme is in the ferric (Fe3+) rather than the normal ferrous (Fe2+) state, it is called methemoglobin. Methemoglobin does not bind oxygen. Methemoglobinemia has several causes, including oxidation of Fe2+ to Fe3+ by nitrites and sulfonamides. There is also a congenital variant of the disease in which there is a deficiency of methemoglobin reductase, an enzyme in red blood cells that normally keeps iron in its reduced state.

59
Q

Minute Ventilation

A

is the tidal volume (TD) x breaths/minute.

60
Q

Mixed Venous Blood

A

Represents the partial pressure of O2 and CO2 in venous blood.

61
Q

Oxygen-binding capacity –

A

is the maximum amount of oxygen that can be bound to hemoglobin per volume of blood.

62
Q

Oxygen-Hemoglobin Dissociation Curve

A
63
Q

Oxyhemoglobin

A

Is the oxygenated form of hemoglobin.

64
Q

Physiologic Dead Space

A

is the total volume of the lungs that does not participate in gas exchange. Physiologic dead space includes the anatomic dead space of the conducting airways plus a functional dead space in the alveoli.

65
Q

Pneumocytes – Type I

A

Epithelial cells of the alveoli

66
Q

Pneumocytes – Type II

A

Synthesize pulmonary surfactant which is necessary for reduction of surface tension in the alveoli. Regenerate into Type I and Type II alveolar cells.

67
Q

Pulse Oximetry

A

is a non-invasive method allowing the monitoring of the oxygenation of a patient’s hemoglobin.

68
Q

Residual Volume

A

The volume of gas remaining in the lungs after a maximal forced expiration is the residual volume.

69
Q

Resistance

A

is determined by Poiseuille’s equation:
R = 8ηL/πr4, where R is the resistance to flow, η is the viscosity of inspired air, l is the length of the airway, r is the radius of the airway.

70
Q

Respiratory Acidosis

A

is caused by hypoventilation, which results in CO2 retention, increased PCO2 , and decreased pH.

71
Q

Respiratory Zone (or Respiratory Airways)

A

includes the structures that are lined with alveoli and, therefore, participate in exchange. Gas exchange structures include the respiratory bronchioles, the alveolar ducts, and the alveolar sacs.

72
Q

Respiratory Alkalosis

A

is caused by hyperventilation, which results in CO2 loss, decreased PCO2, and increased pH.

73
Q

Right-To-Left Shunts

A

Shunting of blood from the right side of the heart to the left side of the heart can occur if there is a defect in the wall between the right and left ventricles. As much as 50% of the cardiac output can be routed from the right ventricle directly to the left ventricle and never be pumped to the lungs for arterialization. In a right-to-left shunt, hypoxemia always occurs because a significant fraction of the cardiac output is not delivered to the lungs or oxygenation.

74
Q

Surfactant

A

is a mixture of phospholipids (e.g., phosphatidylcholine) that line the alveoli and reduce their surface tension. By reducing surface tension, surfactant reduces the collapsing pressure for a given radius

75
Q

Tidal Volume

A

includes the volume of air that fills the alveoli plus the volume of air that fills the airways.

76
Q

Total Lung Capacity

A

includes all of the lung volumes. It is the vital capacity plus the residual volume.

77
Q

Ventilation

A

is the process of exchange of air between the lungs and the ambient air.

78
Q

Ventilation-Perfusion Mismatch

A

A mismatch of ventilation and perfusion, called V/Q mismatch, results in abnormal gas exchange. A V/Q mismatch can be caused by ventilation of lung regions that are not perfused (dead space), perfusion of lung regions that are not ventilated (shunt), and every possibility in between.

79
Q

Ventilation/Perfusion Ratio

A

The ventilation/perfusion ratio is the ratio of alveolar ventilation to pulmonary blood flow. Matching ventilation to perfusion is critically important for ideal gas exchange.

80
Q

Vital Capacity

A

is composed of the inspiratory capacity plus the expiratory reserve volume. It is the volume that can be expired after maximal inspiration. Vital capacity increases with body size, male gender, and physical conditioning.

Respiratory Physiology (1 decks)

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