Physiology: Respiratory

Questions and Answers

What is the volume that remains in the lungs after a maximal expiration?

Residual volume

What is the functional measurement that is defined as the volume of the lungs that does not participate in gas exchange?

Physiologic dead space

What is the volume that can be inspired over and above the tidal volume?

Inspiratory reserve volume

What is the volume of the conducting airways?

Anatomic dead space Signup and view all the answers

What is the equation used to calculate physiologic dead space?

Vn = VT X PAco2 - PEco2 Signup and view all the answers

What is the normal approximate value of anatomic dead space?

150 mL Signup and view all the answers

What is the volume that can be expired after the expiration of a tidal volume?

Expiratory reserve volume Signup and view all the answers

What is the term for the difference between the volume of air that can be inspired and the tidal volume?

Inspiratory capacity Signup and view all the answers

What happens to the abdominal contents when the diaphragm contracts?

They are pushed downward Signup and view all the answers

During normal quiet breathing, which muscles are NOT used for inspiration?

External intercostals Signup and view all the answers

What is the process of expiration normally?

Passive Signup and view all the answers

What is the role of abdominal muscles during forced expiration?

They compress the abdominal cavity and push the diaphragm up Signup and view all the answers

What is the equation for compliance of the respiratory system?

C = VIP Signup and view all the answers

What is the relationship between compliance and elastance?

They are inversely related Signup and view all the answers

What is the units of compliance in the respiratory system?

mL/mm Hg Signup and view all the answers

What is the slope of the pressure-volume curve?

Compliance Signup and view all the answers

What is the sum of all four lung volumes?

Total lung capacity (TLC) Signup and view all the answers

What is the ratio of FEV1 to FVC in normal subjects?

FEV1/FVC = 0.8 Signup and view all the answers

What is the most important muscle for inspiration?

Diaphragm Signup and view all the answers

In restrictive lung disease, such as fibrosis, what is the effect on FEV1 and FVC?

FEV1 is reduced less than FVC Signup and view all the answers

What is the volume of air that can be forcibly expired after a maximal inspiration?

Forced vital capacity (FVC) Signup and view all the answers

What is the effect on FEV1/FVC in obstructive lung disease, such as asthma and COPD?

FEV1/FVC is decreased Signup and view all the answers

What is the unit of measurement for time in the figure illustrates FVC and FEV1?

Seconds Signup and view all the answers

In which type of lung disease is FEV1 reduced more than FVC?

Obstructive lung disease Signup and view all the answers

What is the difference in pressure that determines lung volume?

Alveolar pressure minus intrapleural pressure Signup and view all the answers

What occurs when the pressure outside of the lungs is negative?

Lung volume increases Signup and view all the answers

What is the term for the difference between the inflation and deflation curves of the lung?

Hysteresis Signup and view all the answers

At what range of pressures is lung compliance greatest?

Middle range of pressures Signup and view all the answers

What is the result of high expanding pressures on lung compliance?

Compliance decreases Signup and view all the answers

What is the relationship between the compliance of the lungs and chest wall separately and together?

Compliance of the lung-chest wall system is less than that of the lungs alone or the chest wall alone Signup and view all the answers

What is the shape of the pressure-volume curve at high expanding pressures?

Flat Signup and view all the answers

Why does the lung follow a different curve during inspiration and expiration?

Due to the need to overcome surface tension forces at the air-liquid interface Signup and view all the answers

What happens to the intrapleural pressure when air is introduced into the intrapleural space?

It becomes equal to atmospheric pressure Signup and view all the answers

What is the result of increased lung compliance in a patient with emphysema?

A higher FRC Signup and view all the answers

What is the tendency of the lungs in a patient with fibrosis?

To collapse more Signup and view all the answers

What is the relationship between the collapsing force on the lungs and the expanding force on the chest wall at FRC?

The two forces are equal and opposite Signup and view all the answers

What is the effect of decreased lung compliance in a patient with fibrosis?

The tendency of the lungs to collapse is increased Signup and view all the answers

What happens to the chest wall in a patient with emphysema?

It becomes barrel-shaped Signup and view all the answers

What is the result of the opposing forces at FRC?

The combined lung-chest wall system is in equilibrium Signup and view all the answers

What is the relationship between elastic recoil and lung compliance?

As elastic recoil increases, lung compliance decreases Signup and view all the answers

What is the relationship between surface tension and collapsing pressure in an alveolus?

Surface tension is directly proportional to collapsing pressure. Signup and view all the answers

What is the effect of surfactant on the collapsing pressure of small alveoli?

Surfactant reduces the collapsing pressure of small alveoli. Signup and view all the answers

What is the difference in collapsing pressure between large and small alveoli?

Small alveoli have a higher collapsing pressure than large alveoli. Signup and view all the answers

What is the role of surfactant in preventing alveolar collapse?

Surfactant reduces the surface tension of alveoli. Signup and view all the answers

What is the equation that relates collapsing pressure, surface tension, and alveolar radius?

P = 2T/r Signup and view all the answers

Why do small alveoli have a tendency to collapse?

Because of their high collapsing pressure. Signup and view all the answers

What is the effect of surfactant on alveolar compliance?

Surfactant increases alveolar compliance. Signup and view all the answers

What is the relationship between alveolar radius and collapsing pressure?

Collapsing pressure is inversely proportional to alveolar radius. Signup and view all the answers

What is the relationship between the radius of the airway and the resistance to airflow?

Inverse fourth-power Signup and view all the answers

What is the primary site of airway resistance in the respiratory system?

Medium-sized bronchi Signup and view all the answers

What is the effect of parasympathetic stimulation on airway resistance?

Decreases airway radius and increases resistance Signup and view all the answers

What is the effect of high lung volumes on airway resistance?

Decreases airway resistance Signup and view all the answers

What is the effect of sympathetic stimulation on airway resistance?

Decreases airway resistance Signup and view all the answers

What is the relationship between airway radius and airflow?

Directly proportional Signup and view all the answers

What is the effect of a 4-fold decrease in airway radius on resistance?

Increases resistance by a factor of 256 Signup and view all the answers

What is the mechanism by which lung volume affects airway resistance?

Radial traction on airways by surrounding lung tissue Signup and view all the answers

What is the reason why patients with COPD learn to expire slowly with 'pursed lips'?

To create a resistance at the mouth, increasing airway pressure and preventing airway collapse Signup and view all the answers

What is the characteristic of lung disease in patients with 'pink puffers'?

Mild hypoxemia and nonnocapnia Signup and view all the answers

What is the effect of increased lung compliance in a patient with COPD?

Increased air trapping and increased FRC Signup and view all the answers

What is the characteristic of lung disease in patients with fibrosis?

Restrictive lung disease with decreased lung compliance Signup and view all the answers

What is the effect of air trapping in patients with COPD?

Increased FRC Signup and view all the answers

What is the characteristic of patients with 'blue bloaters'?

Severe hypoxemia with cyanosis and hypercapnia Signup and view all the answers

What is the effect of COPD on FEV1, FVC, and FEV1/FVC?

Decreased FEV1, decreased FVC, and decreased FEV1/FVC Signup and view all the answers

What is the shape of the chest in a patient with COPD?

Barrel-shaped Signup and view all the answers

What is the main reason for the increase in FEV1/FVC in restrictive lung disease?

Decreased FVC Signup and view all the answers

What is the partial pressure of oxygen in humidified tracheal air at 37°C?

150 mm Hg Signup and view all the answers

What is the effect of physiologic shunt on the Po2 of arterial blood?

Decreases the Po2 of arterial blood Signup and view all the answers

What is the relationship between the amount of gas dissolved in a solution and its partial pressure?

The amount of gas dissolved is directly proportional to its partial pressure Signup and view all the answers

What is the characteristic of FEV1/FVC in obstructive lung disease, such as asthma and COPD?

Decreased FEV1/FVC ratio Signup and view all the answers

What is the correction factor for calculating the partial pressure of oxygen in humidified tracheal air?

47 mm Hg Signup and view all the answers

What is the effect of restrictive lung disease, such as fibrosis, on FEV1 and FVC?

Decreased FEV1, decreased FVC Signup and view all the answers

What is the equation for calculating the partial pressure of a gas?

Partial pressure = Total pressure x Fractional gas concentration Signup and view all the answers

What is the concentration of dissolved oxygen in blood when the partial pressure of oxygen is 100 mmHg?

0.3 mL O2/100 mL blood Signup and view all the answers

What is the partial pressure of oxygen in humidified tracheal air?

100 mmHg Signup and view all the answers

What is the partial pressure of carbon dioxide in alveolar air after equilibration with pulmonary capillary blood?

46 mmHg Signup and view all the answers

What is the effect of oxygen diffusion from alveolar air into pulmonary capillary blood on the partial pressure of oxygen?

It decreases the partial pressure of oxygen Signup and view all the answers

What is the reason for the difference in partial pressure of oxygen between arterial and mixed venous blood?

Oxygen diffusion from arterial blood into tissues Signup and view all the answers

What is the effect of the addition of water to inspired air on the partial pressure of oxygen?

It decreases the partial pressure of oxygen Signup and view all the answers

What is the primary factor that determines the diffusion rate of oxygen and carbon dioxide across the alveolar-pulmonary capillary membrane?

Partial pressure difference of the gases Signup and view all the answers

What is the equation that describes the diffusion of gases across the alveolar-pulmonary capillary membrane?

V = DL/AP Signup and view all the answers

What happens to the lung diffusing capacity (DL) during exercise?

It increases due to increased surface area for diffusion Signup and view all the answers

What type of gas exchange is illustrated by N2O and by O2 under normal conditions?

Perfusion-limited exchange Signup and view all the answers

What is the effect of emphysema on the lung diffusing capacity (DL)?

It decreases due to decreased surface area for diffusion Signup and view all the answers

What is the effect of fibrosis on the lung diffusing capacity (DL)?

It decreases due to increased diffusion distance Signup and view all the answers

What is the relationship between the lung diffusing capacity (DL) and the diffusion coefficient of the gas?

DL is directly proportional to the diffusion coefficient of the gas Signup and view all the answers

What is the equivalent of permeability of the alveolar-pulmonary capillary barrier?

Lung diffusing capacity (DL) Signup and view all the answers

What is the primary limiting factor in perfusion-limited gas exchange?

Blood flow Signup and view all the answers

In which type of gas exchange does the partial pressure difference between alveolar air and pulmonary capillary blood remain throughout the length of the capillary?

Diffusion-limited Signup and view all the answers

What is the effect of thickening of the alveolar membrane on oxygen diffusion?

Decreases diffusion rate Signup and view all the answers

Which of the following is an example of a diffusion-limited gas?

Oxygen during strenuous exercise Signup and view all the answers

What is the primary function of hemoglobin in oxygen transport?

Increasing oxygen-carrying capacity Signup and view all the answers

What is the result of decreased surface area for gas exchange in emphysema?

Decreased oxygen diffusion Signup and view all the answers

In diffusion-limited exchange, what happens to the partial pressure of the gas as blood flows through the pulmonary capillary?

It remains different from the partial pressure in alveolar air Signup and view all the answers

What is the primary mechanism of oxygen transport in the blood?

Oxygen bound to hemoglobin Signup and view all the answers

Which of the following is an example of a perfusion-limited gas?

Oxygen during normal conditions Signup and view all the answers

What is the primary cause of a high A-a gradient in a patient with fibrosis?

Decreased diffusion capacity Signup and view all the answers

What is the value of the respiratory exchange ratio (R) used in the alveolar gas equation?

0.8 Signup and view all the answers

What is the normal range of the A-a gradient?

0-10 mm Hg Signup and view all the answers

What is the equation used to calculate the A-a gradient?

PAo2 - Pao2 Signup and view all the answers

What is the primary factor that determines the A-a gradient?

Diffusion capacity Signup and view all the answers

What is the effect of a right-to-left shunt on the A-a gradient?

Increased A-a gradient Signup and view all the answers

What is the primary cause of increased A-a gradient?

Right-to-left shunt Signup and view all the answers

What is the effect of decreased hemoglobin concentration on oxygen delivery?

Decreases oxygen delivery Signup and view all the answers

What is the mechanism by which hypoxia-inducible factor 1a is produced in response to hypoxia?

Decreased oxygen delivery to the kidneys Signup and view all the answers

What is the effect of cyanide poisoning on oxygen delivery?

Decreases oxygen delivery Signup and view all the answers

What is the role of erythropoietin in response to hypoxia?

Increases hemoglobin synthesis Signup and view all the answers

What is the equation that describes oxygen delivery?

O2 delivery = Cardiac output x O2 content of blood Signup and view all the answers

What is the enzyme that facilitates the reaction between CO2 and H2O to form H2CO3 in the red blood cells?

Carbonic anhydrase Signup and view all the answers

What is the major form in which CO2 is transported to the lungs?

HCO3- Signup and view all the answers

What is the purpose of the chloride shift in red blood cells?

To exchange Cl- for HCO3- Signup and view all the answers

Why is deoxyhemoglobin a better buffer for H+ ions than oxyhemoglobin?

Deoxyhemoglobin has a higher buffering capacity Signup and view all the answers

What is the significance of the deoxygenation of hemoglobin by the time blood reaches the venous end of the capillaries?

It allows for more efficient transportation of CO2 Signup and view all the answers

What is the purpose of the hydration reaction of CO2 in the red blood cells?

To convert CO2 to H2CO3 Signup and view all the answers

What is the percentage of cardiac output that bypasses the lungs in right-to-left shunts under normal conditions?

2% Signup and view all the answers

What happens to the arterial P~ when a right-to-left shunt occurs?

It decreases Signup and view all the answers

What is the direction of blood flow in a left-to-right shunt?

From the right side of the heart to the left side of the heart Signup and view all the answers

What is the approximate V/Q ratio in a normal individual?

0.8 Signup and view all the answers

What is the effect of a left-to-right shunt on arterial P~?

It increases Signup and view all the answers

What is the purpose of having the patient breathe 100% O2 to estimate the magnitude of a right-to-left shunt?

To estimate the degree of dilution of oxygenated arterial blood by non-oxygenated shunted blood Signup and view all the answers

What is the effect of gravitational forces on arterial pressure in the upright lung?

It decreases arterial pressure at the apex and increases it at the base Signup and view all the answers

Which of the following statements is true about the V/Q ratio in the lung?

It is lowest at the base and highest at the apex Signup and view all the answers

What is the effect of a complete airway blockage on the V/Q ratio?

It makes the V/Q ratio zero Signup and view all the answers

What is the relationship between Po2 and Pco2 at the apex and base of the lung?

Po2 is highest at the apex and Pco2 is lowest at the base Signup and view all the answers

What is the primary reason for the regional differences in ventilation in the upright lung?

Gravitational forces Signup and view all the answers

What is the effect of the regional differences in V/Q ratio on gas exchange?

It increases the efficiency of gas exchange at the apex and decreases it at the base Signup and view all the answers

Which nerve relays information from peripheral chemoreceptors and mechanoreceptors in the lung?

Vagus nerve Signup and view all the answers

What is the effect of airway obstruction on the composition of systemic arterial blood?

It approaches the composition of mixed venous blood. Signup and view all the answers

What is the primary function of the dorsal respiratory group?

Generation of the basic rhythm for breathing Signup and view all the answers

Where is the pneumotaxic center located?

Upper pons Signup and view all the answers

What is the condition where blood flow to a lung is completely blocked, leading to zero blood flow, but ventilation is normal?

Dead space. Signup and view all the answers

What is the location of the medullary respiratory center?

Reticular formation. Signup and view all the answers

What is the role of central chemoreceptors in the medulla?

Detection of CO2 levels Signup and view all the answers

What is the primary function of the apneustic center?

Stimulation of inspiration Signup and view all the answers

What is the effect of a pulmonary embolus on the composition of alveolar gas?

It approaches the composition of inspired air. Signup and view all the answers

What is the term for the situation where ventilation is normal, but blood flow is zero?

Dead space. Signup and view all the answers

What is the role of the ventral respiratory group?

Regulation of expiration Signup and view all the answers

What is the effect of a ventilation-perfusion defect on gas exchange?

It decreases gas exchange. Signup and view all the answers

What is the effect of hyperventilation on breath-holding?

It increases the duration of breath-holding Signup and view all the answers

What is the coordinating center for sensory information in the brain?

Brainstem. Signup and view all the answers

What is the effect of a decrease in pH of the cerebrospinal fluid (CSF) on breathing rate?

Hyperventilation Signup and view all the answers

Why does CO2 diffuse from arterial blood into the CSF?

Because CO2 is lipid soluble Signup and view all the answers

What happens when CO2 combines with H2O in the CSF?

H+ and HCO3- are produced Signup and view all the answers

What is the effect of an increase in Pco2 and [H+] on breathing rate?

Stimulate breathing Signup and view all the answers

What is the response of peripheral chemoreceptors to a decrease in arterial Pco2?

Stimulate breathing Signup and view all the answers

Where are the carotid bodies located?

At the bifurcation of the common carotid arteries Signup and view all the answers

What is the effect of hyperventilation or hypoventilation on arterial Pco2?

Return Pco2 to normal Signup and view all the answers

Why do decreases in pH of the CSF produce increases in breathing rate?

Because H+ acts directly on the central chemoreceptors Signup and view all the answers

What is the role of the central chemoreceptors in regulating breathing?

Respond to changes in CSF pH Signup and view all the answers

Study Notes

Here are the study notes:

Respiratory Physiology*

Lung Volumes and Capacities

Tidal volume (VT): volume inspired or expired with each normal breath
Inspiratory reserve volume (IRV): volume that can be inspired over and above the tidal volume, used during exercise
Expiratory reserve volume (ERV): volume that can be expired after the expiration of a tidal volume
Residual volume (RV): volume that remains in the lungs after a maximal expiration, cannot be measured by spirometry
Dead space: volume of the lungs that does not participate in gas exchange
- Anatomic dead space: volume of the conducting airways (approximately 150 mL)
- Physiologic dead space: functional measurement of the volume of the lungs that does not participate in gas exchange (approximately equal to anatomic dead space in normal lungs, but may be greater in lung diseases with ventilation/perfusion defects)

Compliance of the Respiratory System

Compliance: describes the distensibility of the lungs and chest wall
Equation: C = ΔV / ΔP
Describes the change in volume for a given change in pressure
Inversely related to elastance and stiffness

Muscles of Inspiration and Expiration

Muscles of inspiration:
- Diaphragm: most important muscle for inspiration
- External intercostal muscles: not used for inspiration during normal quiet breathing, but used during exercise and in respiratory distress
Muscles of expiration:
- Abdominal muscles: compress the abdominal cavity, push the diaphragm up, and push air out of the lungs
- Internal intercostal muscles: pull the ribs downward and inward

Lung Disease

Asthma: obstructive disease, expiration is impaired, characterized by decreased FVC, FEV1, and FEV1/FVC
Chronic Obstructive Pulmonary Disease (COPD): obstructive disease with increased lung compliance, expiration is impaired, characterized by decreased FVC, FEV1, and FEV1/FVC
- Emphysema: "pink puffers" (mild hypoxemia, normal PCO2)
- Chronic bronchitis: "blue bloaters" (severe hypoxemia with cyanosis, hypercapnia, and right ventricular failure)
Fibrosis: restrictive disease, inspiration is impaired, characterized by a decrease in all lung volumes

Gas Exchange

Dalton's law of partial pressures: P = PT x F
Partial pressure of O2 and CO2 in inspired air, alveolar air, and blood
Dissolved gases: amount of gas dissolved in a solution is proportional to its partial pressure
Diffusion of gases: rates depend on partial pressure differences across the membrane and the area available for diffusion
Lung diffusing capacity (DL): equivalent to permeability of the alveolar-pulmonary capillary barrier

Oxygen Transport

Oxygen is carried in blood in two forms: dissolved or bound to hemoglobin
Hemoglobin increases the O2-carrying capacity of blood 70-fold
A-a gradient: difference in PO2 between alveolar gas and arterial blood
Causes of hypoxemia:
- High altitude
- Hypoventilation
- Diffusion defect
- V/Q defect
- Right-to-left shunt
Erythropoietin (EPO): a growth factor that is synthesized in the kidneys in response to hypoxia### Hypoxia-Inducible Factor and EPO
Hypoxia-inducible factor 1α directs the synthesis of mRNA for EPO, which promotes the development of mature red blood cells.

CO2 Transport

CO2 is transported in three forms: dissolved CO2, carbaminohemoglobin, and HCO3- (the major form, accounting for 90%)
In the RBCs, CO2 combines with H2O to form H2CO3, which dissociates into H+ and HCO3-
HCO3- leaves the RBCs in exchange for Cl- (chloride shift) and is transported to the lungs in the plasma
H+ is buffered inside the RBCs by deoxyhemoglobin, which is a better buffer for H+ than oxyhemoglobin

Shunts

Right-to-left shunts occur when 2% of the cardiac output bypasses the lungs, resulting in a decrease in arterial P02
May be as great as 50% of cardiac output in certain congenital abnormalities, such as tetralogy of Fallot
Left-to-right shunts are more common, caused by congenital abnormalities or traumatic injury, and do not result in a decrease in arterial P02

V/Q Defects

V/Q ratio is the ratio of alveolar ventilation (V) to pulmonary blood flow (Q)
Ventilation and perfusion (blood flow) matching is important for achieving the ideal exchange of O2 and CO2
Normal V/Q ratio is approximately 0.8, resulting in an arterial P02 of 100 mm Hg and an arterial Pco2 of 40 mm Hg
Regional variations in the lung of perfusion, ventilation, V/Q, P02, and Pco2 occur due to gravitational effects
V/Q ratio is higher at the apex and lower at the base of the lung
As a result, gas exchange is more efficient at the apex and less efficient at the base

Changes in V/Q Ratio

V/Q ratio in airway obstruction: If airways are completely blocked, then ventilation is zero, resulting in a V/Q ratio of 0
V/Q ratio in pulmonary embolism: If blood flow to a lung is completely blocked, then blood flow to that lung is zero, resulting in a V/Q ratio of infinity (dead space)

Control of Breathing

Central control of breathing involves the brainstem and cerebral cortex
Medullary respiratory center is located in the reticular formation and responds to changes in pH of the CSF
Peripheral chemoreceptors in the carotid and aortic bodies respond to changes in arterial P02

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the concept of forced vital capacity, FEV1, and spirometry in normal subjects and patients with lung diseases such as asthma, COPD, and fibrosis.