Guyton and Hall Physiology Chapter 43 - Respiratory Insufficiency—Pathophysiology, Diagnosis, Oxygen Therapy
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Questions and Answers

What is the physiological effect of administering O2 in atmospheric hypoxia?

  • It leads to excess CO2 buildup.
  • It changes the color of deoxygenated hemoglobin.
  • It can completely correct the depressed O2 levels in inspired gases. (correct)
  • It has no measurable effect on O2 levels.

    • How does hypoventilation hypoxia affect the exchange of oxygen?

  • It results in an increased amount of CO2 in the alveoli.
  • O2 therapy provides minimal benefit.
  • It completely inhibits O2 exchange in the lungs.
  • Breathing 100% O2 can increase O2 transport into the alveoli significantly. (correct)

    • What does the presence of cyanosis indicate in a patient?

  • Excess oxygen in the blood.
  • Optimal oxygen transport to tissues.
  • Excessive amounts of deoxygenated hemoglobin. (correct)
  • Deficiency of oxygenated hemoglobin.

    • What is a key characteristic of tissue hypoxia in relation to oxygen therapy?

    <p>There is no abnormality in O2 pickup by the lungs.</p> Signup and view all the answers

    Why is oxygen therapy ineffective for tissue hypoxia?

    <p>The tissues cannot use the O2 that is delivered.</p> Signup and view all the answers

    What is the anticipated benefit of O2 therapy in cases of hypoventilation hypoxia?

    <p>It allows for a significant increase in O2 delivery to the alveoli.</p> Signup and view all the answers

    What is the primary cause of cyanosis in the skin?

    <p>Excessive deoxygenated hemoglobin in blood vessels.</p> Signup and view all the answers

    What is one method of delivering oxygen therapy?

    <p>Using a special mask to facilitate O2 delivery.</p> Signup and view all the answers

    What can cyanide interfere with in the body that leads to hypoxia?

    <p>Oxidative enzymes in tissues</p> Signup and view all the answers

    Which condition is specifically associated with a deficiency that compromises tissue utilization of oxygen?

    <p>Beriberi</p> Signup and view all the answers

    Which of the following effects is primarily associated with the release of histamine during an asthma attack?

    <p>Local edema in the walls of small bronchioles</p> Signup and view all the answers

    What is a common effect of severe hypoxia on the body?

    <p>Cell death</p> Signup and view all the answers

    What clinical characteristic is commonly observed in advanced tuberculosis?

    <p>Formation of abscess cavities in lung tissue</p> Signup and view all the answers

    What happens to oxygen levels in the alveoli when there is circulatory deficiency?

    <p>Oxygen levels remain normal</p> Signup and view all the answers

    Which of the following substances is primarily released by mast cells during an allergic reaction in asthma?

    <p>Histamine</p> Signup and view all the answers

    How does vitamin B deficiency affect pulmonary blood oxygen uptake in patients with pulmonary edema?

    <p>It increases uptake three to four times</p> Signup and view all the answers

    How does hypoxia primarily affect respiratory function?

    <p>Decreases oxygen transport to tissues</p> Signup and view all the answers

    Which symptom is NOT commonly associated with less severe degrees of hypoxia?

    <p>Increased oxygen saturation</p> Signup and view all the answers

    In which scenario is oxygen therapy likely to provide significant therapeutic benefits?

    <p>In severe cellular hypoxia</p> Signup and view all the answers

    What is the primary role of oxidative enzymes in tissues related to oxygen?

    <p>Utilize oxygen for cellular metabolism</p> Signup and view all the answers

    What mechanism is primarily impaired in hypoxia caused by abnormal hemoglobin?

    <p>Oxygen transport from lungs to tissues</p> Signup and view all the answers

    Which of the following best describes the effect of oxygen therapy in diffusion hypoxia?

    <p>It significantly enhances oxygen uptake</p> Signup and view all the answers

    What is a classic cause of inadequate tissue capability to use oxygen?

    <p>Cyanide poisoning</p> Signup and view all the answers

    What condition is primarily indicated by pulmonary edema with low oxygen therapy?

    <p>Diminished oxygen exchange</p> Signup and view all the answers

    Which factor is NOT associated with diminished cellular metabolic capacity for using oxygen?

    <p>High arterial Po2</p> Signup and view all the answers

    In what way can oxygen therapy influence hypoxia caused by impaired alveolar membrane diffusion?

    <p>By raising Po2 in the lung alveoli</p> Signup and view all the answers

    What is most likely to occur if there is inadequate tissue capability to utilize oxygen?

    <p>Decreased aerobic respiration</p> Signup and view all the answers

    What is a potential outcome of pulmonary edema without oxygen therapy?

    <p>Reduced tissue perfusion</p> Signup and view all the answers

    Which response is characteristic of tissue hypoxia caused by poisoning of cellular enzymes?

    <p>Cellular necrosis</p> Signup and view all the answers

    What is the effect of increased Po2 from oxygen therapy in hypoxic conditions?

    <p>Increased alveolar oxygen pressure</p> Signup and view all the answers

    Which factor would most likely lead to hypoventilation hypoxia?

    <p>Obstructed airways</p> Signup and view all the answers

    Which condition is primarily associated with diminished oxygen uptake in tissues?

    <p>Cellular hypoxia</p> Signup and view all the answers

    What physiological change occurs in the bronchioles during expiration in individuals with asthma?

    <p>Bronchiolar collapse</p> Signup and view all the answers

    Which of the following is NOT a cause of inadequate oxygenation of the blood in the lungs?

    <p>Obstruction of blood vessels</p> Signup and view all the answers

    How does asthma primarily affect expiratory airflow compared to inspiratory airflow?

    <p>Decreased expiratory airflow</p> Signup and view all the answers

    Which of the following conditions can lead to pulmonary disease causing hypoventilation?

    <p>Increased airway resistance</p> Signup and view all the answers

    Which factor describes a right-to-left cardiac shunt's role in hypoxia?

    <p>Inadequate O2 transport to tissues</p> Signup and view all the answers

    What effect does increased airway resistance have on maximum expiratory rates for asthmatic patients?

    <p>Decreases maximum expiratory rates</p> Signup and view all the answers

    Which of the following does NOT contribute to venous-to-arterial shunting?

    <p>Hyperventilation</p> Signup and view all the answers

    What condition refers to the sensation of 'air hunger' experienced by asthmatic patients?

    <p>Dyspnea</p> Signup and view all the answers

    What is a potential cause of hypoxia related to abnormal hemoglobin levels?

    <p>Anemia</p> Signup and view all the answers

    Which mechanism can lead to hypoxia by affecting the ventilation-perfusion ratio?

    <p>Physiological dead space</p> Signup and view all the answers

    What occurs alongside hypoxia in cases of hypoventilation?

    <p>Hypercapnia</p> Signup and view all the answers

    Which type of dyspnea may occur when a person's respiratory functions are otherwise normal?

    <p>Neurogenic dyspnea</p> Signup and view all the answers

    What primarily stimulates pulmonary ventilation in cases of hypercapnia?

    <p>High CO2 levels</p> Signup and view all the answers

    What is primarily affected in circulatory deficiency related to respiratory performance?

    <p>Tissue CO2 removal</p> Signup and view all the answers

    What condition enhances the feeling of dyspnea due to psychological factors?

    <p>Neurogenic dyspnea</p> Signup and view all the answers

    What is a significant effect of administering extra O2 during alveolar O2 increase?

    <p>It allows for a small amount of O2 to be transported dissolved in blood.</p> Signup and view all the answers

    In which hypoxia situation does O2 therapy provide no measurable benefit?

    <p>Tissue hypoxia due to enzyme dysfunction.</p> Signup and view all the answers

    What therapeutic benefit is observed when administering 100% O2 in hypoventilation hypoxia?

    <p>It increases O2 availability in the alveoli significantly.</p> Signup and view all the answers

    What causes the bluish discoloration of the skin known as cyanosis?

    <p>Excessive amounts of deoxygenated hemoglobin.</p> Signup and view all the answers

    In atmospheric hypoxia, how does O2 therapy impact inspired gases?

    <p>It completely corrects the depressed O2 level.</p> Signup and view all the answers

    What is the primary effect of the leather diaphragm moving inward in the tank respirator?

    <p>Generates negative pressure for inspiration</p> Signup and view all the answers

    How does the pressure change during the respiration process using a tank respirator?

    <p>Positive pressure rises to +5 cm H2O for expiration</p> Signup and view all the answers

    What is the reason for the tank respirator being considered largely obsolete in modern medicine?

    <p>Development of advanced mechanical ventilators</p> Signup and view all the answers

    What is the typical range of negative pressure achieved during inspiration with the use of a tank respirator?

    <p>-10 to -20 cm H2O</p> Signup and view all the answers

    What function do check valves serve in the tank respirator?

    <p>To control pressure changes</p> Signup and view all the answers

    What mechanical principle is utilized by the tank respirator to assist breathing?

    <p>Negative pressure assistance</p> Signup and view all the answers

    Which of the following refers to an outdated method of providing respiratory support?

    <p>Tank respirator</p> Signup and view all the answers

    What happens to pressures inside the tank respirator when the diaphragm moves outward?

    <p>Negative pressure creates inspiration</p> Signup and view all the answers

    In what way does the tank respirator affect the air pressure around the body?

    <p>Generates differential pressure for air movement</p> Signup and view all the answers

    What component of the tank respirator allows for controlled release of air pressure?

    <p>Check valves</p> Signup and view all the answers

    The leather diaphragm in a tank respirator creates negative pressure to cause expiration.

    <p>False</p> Signup and view all the answers

    Modern mechanical ventilators are superior to the tank respirator in pushing air into the airways.

    <p>True</p> Signup and view all the answers

    The pressures used in breathing can range from −20 to 0 cm H2O during inspiration.

    <p>True</p> Signup and view all the answers

    Check valves on a respirator help to maintain only positive pressure during the breathing cycle.

    <p>False</p> Signup and view all the answers

    The tank respirator is still widely used in modern medicine due to its effectiveness.

    <p>False</p> Signup and view all the answers

    Bronchiolar collapse during expiration leads to increased maximum expiratory rate in asthmatic patients.

    <p>False</p> Signup and view all the answers

    Inadequate O2 transport to the tissues by the blood can be caused by anemia.

    <p>True</p> Signup and view all the answers

    Pulmonary disease is often associated with an abnormal alveolar ventilation-perfusion ratio.

    <p>True</p> Signup and view all the answers

    During inspiration, an asthmatic person typically has more difficulty than during expiration.

    <p>False</p> Signup and view all the answers

    Dyspnea is a term used to describe the sensation of suffocation or 'air hunger' experienced by patients.

    <p>True</p> Signup and view all the answers

    The maximum expiratory flow is greater when the lungs are nearly empty than when they are filled with a large volume of air.

    <p>False</p> Signup and view all the answers

    Maximum expiratory flow cannot be increased further even with greater expiratory effort once it has been achieved.

    <p>True</p> Signup and view all the answers

    Asthma only affects the inspiratory phase of breathing.

    <p>False</p> Signup and view all the answers

    As lung volume decreases, the maximum expiratory flow rate also increases.

    <p>False</p> Signup and view all the answers

    Using a glass electrode pH meter can help determine blood CO2 levels.

    <p>True</p> Signup and view all the answers

    In respiratory diseases, maximum expiratory flow can sometimes be reduced due to increased resistance to airflow.

    <p>True</p> Signup and view all the answers

    The maximum expiratory airflow does not have a set limit and can continually increase with more effort.

    <p>False</p> Signup and view all the answers

    The maximum expiratory flow is particularly important for assessing the function of individuals with respiratory diseases.

    <p>True</p> Signup and view all the answers

    Breathing difficulty during expiration does not occur in healthy individuals.

    <p>True</p> Signup and view all the answers

    Maximum expiratory flow is achieved when the bronchi and bronchioles are completely constricted.

    <p>False</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Hypoxia = Deficiency of oxygen in the tissues Hypercapnia = Excess carbon dioxide in the body fluids Cyanosis = Bluish discoloration of the skin due to lack of oxygen Dyspnea = Difficult or labored breathing</p> Signup and view all the answers

    Match the following causes with their associated conditions:

    <p>Hypoventilation = Reduced airflow leading to increased CO2 levels Circulatory deficiency = Compromised blood flow affecting oxygen delivery Polycythemia vera = Excess red blood cells causing increased hemoglobin Anemia = Insufficient hemoglobin leading to less oxygen transport</p> Signup and view all the answers

    Match the following respiratory sensations with their triggers:

    <p>Dyspnea = Increased work of respiratory muscles Apnea = Voluntary breath-holding Cyanosis = High levels of deoxygenated hemoglobin Hypercapnia = Buildup of CO2 in body fluids</p> Signup and view all the answers

    Match the following symptoms with their potential causes:

    <p>Severe dyspnea = Excess buildup of CO2 Cyanosis = Deoxygenated hemoglobin levels Forceful breathing = Effort to normalize respiratory gases Hypoxia = Insufficient oxygen in the tissues</p> Signup and view all the answers

    Match the following medical conditions with their related factors:

    <p>Excessive red blood cells = Increased risk of cyanosis Anemia = Lower likelihood of cyanosis Hypoventilation = Increased CO2 levels Hypercapnia = Usually occurs with hypoxia from hypoventilation</p> Signup and view all the answers

    Match the type of hypoxia with its treatment method:

    <p>Atmospheric hypoxia = O2 administered via a 'tent' Hypoventilation hypoxia = Breathing pure O2 from a mask Tissue hypoxia = No measurable benefit from O2 therapy Cyanosis = Excessive deoxygenated hemoglobin in blood vessels</p> Signup and view all the answers

    Match the statement about O2 transport to its corresponding condition:

    <p>Increased alveolar O2 = Extra O2 transported in dissolved state High concentrations of O2 = Five times more O2 into alveoli Hypoventilation = Decreased O2 exchange Cyanosis = Blueness of the skin due to hypoxia</p> Signup and view all the answers

    Match the hypoxia type with its characteristic feature:

    <p>Atmospheric hypoxia = Complete correction by O2 therapy Hypoventilation hypoxia = Beneficial with 100% O2 Tissue hypoxia = Normal O2 pickup by lungs Cyanosis = Dark blue-purple color in skin</p> Signup and view all the answers

    Match the method of O2 therapy to its description:

    <p>Nasal tube = Delivery of O2 directly to nasal passages Mask = High concentration O2 for breathing Tent = Encloses patient in fortified air Intranasal = Administers O2 through nose</p> Signup and view all the answers

    Match the condition to its impact on oxygen utilization:

    <p>Tissue hypoxia = Incapable use of delivered O2 Hypoventilation = Excess CO2 affects exchange Atmospheric hypoxia = Depressed O2 levels in inspired gases Cyanosis = Presence of deoxygenated hemoglobin</p> Signup and view all the answers

    Study Notes

    Oxygen Therapy

    • Administering O2 can be done by placing the patient's head in an O2-enriched tent, having them breathe pure O2 or high concentrations of O2 from a mask, or through an intranasal tube.
    • O2 therapy can be effective in atmospheric hypoxia and hypoventilation hypoxia.
    • O2 therapy is ineffective in cases of hypoxia caused by inadequate tissue use of O2.
    • There are different types of hypoxia that affect how effective O2 therapy will be.

    Cyanosis

    • Cyanosis is a bluish discoloration of the skin caused by excessive amounts of deoxygenated hemoglobin in the blood vessels.
    • Cyanosis is generally noticeable when arterial oxygen pressure is below 60 mm Hg.

    Hypoxia and Oxygen Therapy

    • Hypoxia is a low oxygen level in the body.
    • Hypoxia can cause depressed mental activity, coma, and reduced muscle work capacity.
    • O2 therapy can be beneficial in hypoxia caused by impaired alveolar membrane diffusion, hypoventilation hypoxia, and pulmonary edema.
    • O2 therapy is less effective in hypoxia caused by anemia, abnormal hemoglobin transport, circulatory deficiency, or physiological shunt.

    Types of Hypoxia

    • Hypoxia caused by inadequate oxygenation of the blood in the lungs because of extrinsic reasons:
      • Deficiency of O2 in the atmosphere
      • Hypoventilation (neuromuscular disorders)
    • Hypoxia caused by pulmonary disease:
      • Hypoventilation caused by increased airway resistance or decreased pulmonary compliance
      • Abnormal alveolar ventilation-perfusion ratio (including increased physiological dead space or increased physiological shunt)
      • Diminished respiratory membrane diffusion
    • Hypoxia caused by venous-to-arterial shunts (right-to-left cardiac shunts)
    • Hypoxia caused by Inadequate O2 transport to the tissues by the blood:
      • Anemia or abnormal hemoglobin
      • General circulatory deficiency
    • Hypoxia caused by inadequate tissue capability of using O2:
      • Poisoning of cellular oxidation enzymes
      • Diminished cellular metabolic capacity for using oxygen due to toxicity, vitamin deficiency, or other factors

    Asthma

    • Asthma is a condition marked by bronchiolar collapse during expiration, making it difficult to breathe out.
    • This results in reduced maximum expiratory rate and reduced timed expiratory volume.
    • Asthma involves a complex interplay of immune responses and inflammatory mediators.

    Tuberculosis

    • Untreated tuberculosis can result in extensive lung damage, including fibrosis and abscesses.
    • This can lead to reduced lung capacity, decreased respiratory membrane surface area, and abnormal ventilation-perfusion ratios.

    Oxygen Therapy

    • Oxygen therapy can be administered by placing the patient's head in an oxygen-enriched tent, providing oxygen through a mask, or using an intranasal tube.
    • Oxygen therapy is most beneficial in cases of atmospheric hypoxia and hypoventilation hypoxia.
    • Oxygen therapy is ineffective in cases of hypoxia caused by inadequate tissue use of oxygen, as the issue lies in the metabolic enzyme system's inability to utilize available oxygen.

    Cyanosis

    • Cyanosis indicates a bluish discoloration of the skin caused by excessive deoxygenated hemoglobin in the capillaries.
    • Deoxygenated hemoglobin has a dark blue-purple color which is visible through the skin.

    Dyspnea

    • Dyspnea (difficulty breathing) can be caused by a psychological state, even if respiratory functions and blood gas levels are normal.
    • This is called neurogenic dyspnea or emotional dyspnea.
    • Individuals with a fear of insufficient air supply are more likely to experience this type of dyspnea.

    Artificial Respiration

    • Resuscitators utilize positive and negative pressure to assist with breathing.
    • Tank respirators are now largely obsolete due to the development of superior mechanical ventilators.

    Respiratory Disease: Effects on Ventilation

    • Chronic Emphysema: Bronchiolar obstruction increases airway resistance and work of breathing, particularly during expiration.
    • Pneumonia: In the early stages, pneumonia can affect one lung, reducing alveolar ventilation while blood flow remains normal. This leads to reduced respiratory membrane surface area and decreased ventilation-perfusion ratio, resulting in hypoxemia and hypercapnia.
    • Atelectasis: Lung collapse not only occludes the alveoli but also increases resistance to blood flow through the pulmonary vessels of the collapsed lung.

    Types of Hypoxia

    • Hypoxia is a condition where there's not enough oxygen available to the tissues. This can occur due to:
      • Low oxygen in the air
      • Low hemoglobin levels
      • Impaired oxidative enzymes
    • Hypercapnia (high carbon dioxide levels) is not associated with these types of hypoxia because oxygen and carbon dioxide are transported and utilized differently by the body.
      • Hypoxia caused by poor diffusion across the lung membrane or tissues is unlikely to cause hypercapnia because carbon dioxide diffuses much faster than oxygen.
      • Hypoxia due to hypoventilation involves impaired transfer of both oxygen and carbon dioxide, leading to hypercapnia.
      • Circulatory deficiency results in decreased blood flow, causing both tissue hypoxia and tissue hypercapnia. However, the blood's capacity to carry carbon dioxide is higher, leading to milder hypercapnia compared to hypoxia.

    Dyspnea

    • Dyspnea refers to difficulty breathing. It can be caused by:
      • Physical factors, such as hypoxia or hypercapnia.
      • Psychological factors, known as neurogenic or emotional dyspnea. This involves abnormal sensations and can be triggered by anxiety or the act of thinking about breathing.

    Artificial Respiration

    • Resuscitators are devices used for artificial respiration, providing supplementary oxygen or air.
    • They work by employing various mechanisms, such as tank supplies and pressure systems, to deliver air or oxygen to the lungs.

    Constricted Lung Diseases

    • These diseases involve narrowing of the airways or restriction of the chest wall:
      • Fibrotic diseases: Tuberculosis and silicosis, leading to scar tissue formation in the lungs.
      • Diseases affecting the chest cage: Kyphosis, scoliosis, and fibrotic pleurisy, which restrict chest expansion.

    Airway Obstruction

    • Airway obstruction causes difficulty in exhaling rather than inhaling due to increased closing tendency of airways during exhalation.
    • This is characterized by:
      • Increased resistance during expiration, requiring more forceful exhalation.
      • Entrapment of air in alveoli, leading to overstretching and damage.

    Emphysema

    • Emphysema is a chronic respiratory disease that causes progressive damage to the alveoli and airways, leading to significant reduction in lung function and increased breathing difficulty.
    • The condition is caused by a combination of factors including:
      • Chronic infection, causing airway obstruction.
      • Excess mucus, further contributing to obstruction.
      • Inflammatory edema, obstructing small airways.
    • Emphysema results in:
      • Increased airway resistance, leading to greater effort needed for breathing.
      • Hypoxia in collapsed alveoli, further restricting blood flow.
      • Destruction of alveolar walls, reducing lung capacity.
    • Physiological effects of emphysema include:
      • Increased work of breathing, due to increased resistance.
      • Hypoxia, due to reduced blood flow and poor gas exchange.
      • Reduced lung capacity, impacting breathing ability.

    Atelectasis

    • Atelectasis is a condition where alveoli collapse, impairing gas exchange and reducing lung capacity.
    • Common causes include:
      • Airway obstruction, preventing air from reaching the alveoli.
      • Lack of surfactant, the substance that helps to keep alveoli open.
    • Airway obstruction caused by mucous plugs, tumors, or other obstructions results in air absorption from the alveoli and subsequent collapse.
    • Surfactant deficiency hinders alveoli from remaining open, leading to collapse.

    Alveolar collapse:

    • When one lung collapses (atelectasis), the collapsed lung is unable to exchange gases, while the other lung compensates by increasing its ventilation.
    • O² saturation of the blood passing through collapsed lung is about 60%, while the blood passing through the aerated lung is about 95% saturated.
    • As a consequence, the overall saturation of blood pumped by the left ventricle into the aorta is about 78%, significantly lower than normal.
    • Blood flow through the atelectatic lung is reduced by vasoconstriction due to hypoxia.
    • Despite this, the majority of blood is diverted to the ventilated lung, resulting in relatively mild desaturation of blood.

    Hypoxia

    • Hypoxia is a condition where the body tissues do not receive enough oxygen.
    • Types of Hypoxia:
      • Hypoxic Hypoxia - Reduced oxygen pressure in the atmosphere
      • Anemic Hypoxia - Reduced ability of the blood to carry oxygen (e.g., anemia)
      • Stagnant Hypoxia - Reduced blood flow to the tissues (e.g., heart failure)
      • Histotoxic Hypoxia - Inability of the tissues to use oxygen (e.g., cyanide poisoning)
    • Cyanide Poisoning inhibits the enzyme cytochrome oxidase, preventing the use of oxygen by cells.

    Dyspnea

    • Dyspnea is a subjective sensation of breathlessness.
    • Causes of Dyspnea:
      • Hypercapnia: Increased carbon dioxide in the body fluids.
      • Hypoxia: Reduced oxygen in the body fluids.
      • Increased Respiratory Muscle Work: Effortful breathing.
      • State of Mind: Psychological factors.

    Respiratory Abnormalities

    • Constricted Lungs: Reduced lung volume, decreased maximum expiratory air flow.
    • Airway Obstruction: Collapsible airways, leading to reduced maximum expiratory flow rate.
    • Asthma: Spasmodic contraction of smooth muscle in bronchioles, partial obstruction, difficult breathing.
    • Prevalence of Asthma: Affects 7-8% of the US population, higher rates in some ethnic groups.
    • Causes of Asthma: Allergic hypersensitivity (especially in under 30s), non-allergenic irritants (including smog).

    Emphysema

    • Emphysema: Destruction of alveolar walls, enlargement of air spaces, difficulty expiring air.
    • Cause of Emphysema: Chronic obstruction of airways (due to infection, mucus, edema) leading to air trapping.
    • Consequences of Emphysema: Air trapping, overstretching alveoli, destruction of alveolar walls.

    Tuberculosis

    • Tuberculosis: Infectious disease caused by Mycobacterium tuberculosis.
    • Tissue Reaction: Invasion by macrophages, "walling off" of infection by fibrous tissue (tubercle).
    • Protective Mechanism: Walling off helps limit spread, preventing the infection from worsening.
    • Complications: In 3% of people, the disease can progress despite the protective response.

    Asthma and Bronchiolar Resistance

    • During expiration, bronchioles become smaller in the lungs of people with asthma due to their collapse.
    • This collapse is caused by the pressure exerted during expiration which further obstructs the bronchioles, already partially occluded in asthmatic lungs.
    • As a result, patients with asthma can inhale adequately but struggle to exhale.
    • This causes reduced maximum expiratory rate and reduced timed expiratory volume, leading to a feeling of 'air hunger' or dyspnea.

    Hypoxia - A Classification of Causes

    • Inadequate oxygenation of blood in the lungs due to:
      • Deficiency of oxygen in the atmosphere.
      • Hypoventilation caused by neuromuscular disorders.
    • Pulmonary disease:
      • Hypoventilation due to increased airway resistance or decreased lung compliance.
      • Abnormal ventilation-perfusion ratio caused by increased physiological dead space and/or increased physiological shunt.
      • Diminished respiratory membrane diffusion.
    • Venous-to-arterial shunts (right-to-left cardiac shunts).
    • Issues in oxygen transport to the tissues by the blood:
      • Anemia or abnormal hemoglobin
      • General circulatory deficiency.

    Atelectasis: Lung Collapse

    • It's a condition where the alveoli collapse either in localized areas or throughout the lung.
    • Two common causes:
      • Total airway obstruction.
      • Lack of surfactant in fluids lining the alveoli.
    • Airway obstruction causes lung collapse in the following scenarios:
      • Blockage of small bronchi by mucus.
      • Obstruction of a major bronchus by a mucous plug or foreign object (e.g., tumor).
    • The trapped air is absorbed by the blood in the pulmonary capillaries, leading to alveolar collapse.

    Surfactant and Lung Collapse

    • Surfactant is a substance secreted by alveolar epithelial cells to decrease surface tension in the alveoli.
    • Lack of surfactant can cause the alveoli to collapse.

    Tuberculosis Tissue Reaction in Lungs

    • Tuberculosis involves a specific tissue reaction in the lungs.
    • This reaction includes:
      • Invasion of infected tissue by macrophages.
      • ''Walling off'' of the lesion by fibrous tissue, known as a tubercle.
    • This "walling off'' process helps limit the spread of the tubercle bacilli and protects against the infection's progression.

    Oxygen Therapy

    • Oxygen therapy can be administered through various methods, including oxygen tents, masks, and nasal tubes.
    • Oxygen therapy is effective in atmospheric hypoxia by correcting the depressed oxygen level in the inspired gases.
    • Oxygen therapy is also beneficial in hypoventilation hypoxia as it allows for increased oxygen uptake in the alveoli.
    • Oxygen therapy does not provide benefit in cases where tissue hypoxia is caused by inadequate tissue oxygen utilization.

    Cyanosis

    • Cyanosis is the bluish discoloration of the skin due to high levels of deoxygenated hemoglobin in the blood vessels.
    • The presence of cyanosis generally indicates more than 5 grams of deoxygenated hemoglobin per 100 ml of blood.
    • Cyanosis is less likely to occur in individuals with anemia due to insufficient hemoglobin for deoxygenation.
    • Cyanosis can occur in individuals with polycythemia vera due to the excess of available hemoglobin that can become deoxygenated.

    Hypercapnia

    • Hypercapnia, or increased carbon dioxide in the body fluids, usually occurs in association with hypoxia caused by hypoventilation or circulatory deficiency.
    • The Henderson-Hasselbalch equation can be used to determine the pH of a solution based on the concentrations of carbon dioxide and bicarbonate ions.

    Dyspnea

    • Dyspnea is a sensation of shortness of breath.
    • Dyspnea can occur due to abnormalities in respiratory gases, particularly hypercapnia and, to a lesser extent, hypoxia.
    • Dyspnea can be caused by increased work required for breathing, even when respiratory gas levels are normal.

    Respiratory Insufficiency

    • Respiratory disorders can result from inadequate ventilation, abnormalities in diffusion across the pulmonary membrane, or abnormal blood transport of gases.
    • The diagnosis and treatment of respiratory insufficiency depend on understanding the underlying cause of the problem.

    Methods for Studying Respiratory Abnormalities

    • Measuring vital capacity, tidal air, functional residual capacity, dead space, physiologic shunt, and physiological dead space are among the methods for studying respiratory abnormalities.

    Chronic Emphysema

    • Chronic emphysema results in increased airway resistance, leading to difficult breathing, particularly during expiration.
    • The increased airway resistance is due to a combination of bronchiolar obstruction and compression of the bronchioles during expiration.
    • The increased work of breathing in chronic emphysema can lead to severe air hunger and ultimately death.

    Pneumonia

    • Pneumonia is an inflammatory condition of the lung in which alveoli are filled with fluid and blood cells.
    • Bacterial pneumonia is caused by infection in the alveoli, leading to inflammation and leakage of fluid and blood cells into the alveoli.
    • In severe cases of pneumonia, large areas of the lungs can become consolidated due to fluid and cellular debris filling the alveoli.

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    This quiz explores the concepts of oxygen therapy, cyanosis, and hypoxia. It delves into the effectiveness of O2 administration in different types of hypoxia, along with the physiological implications of reduced oxygen levels. Test your knowledge on how these elements interrelate in medical practice.

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