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Questions and Answers
Which condition is characterized by airway obstruction due to broncho spasm and expiratory dyspnea?
What type of hypoventilation is characterized by increased pulmonary vessel tone reflex?
Which of the following is NOT a cause of obstructive hypoventilation?
Chronic bronchitis results from prolonged irritation of which part of the respiratory tract?
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What is one of the significant effects associated with obstructive hypoventilation?
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Chronic bronchitis can lead to the development of which of the following conditions over time?
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Which mechanism is primarily associated with cardiogenic pulmonary edema?
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Which type of ventilation issue is caused primarily by the expansion of the bronchial lumen due to infection?
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What is the observed condition when the ventilation/perfusion index (V/P) is less than 0.8?
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What is a common outcome of impaired bronchial obstruction in the context of pulmonary health?
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Which condition is categorized under restrictive types of hypoventilation?
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What stage of pulmonary edema is characterized by plasma entering the alveoli?
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Which pathology is associated with impaired mobility of the diaphragm?
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What is a significant consequence of prolonged pulmonary hypertension?
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Which condition is associated with an increase in norepinephrine levels?
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What does a V/P ratio greater than 1 indicate?
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In pulmonary edema, what causes compression of the bronchi and alveoli?
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Which mechanism is primarily associated with asthma that develops due to profession?
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What pathological feature characterizes emphysema?
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Which type of atelectasis involves the blockage of bronchi lumen leading to the reabsorption of air in the alveoli?
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What condition occurs when air accumulates in the pleural cavity, resulting in lung compression?
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Which type of pneumonia is characterized by bacterial invasion leading to strong exudation and alveolar infiltration?
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Which inflammatory disease of the pleura can develop from a variety of causes?
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In emphysema, an imbalance in which system contributes to alveolar damage?
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Which type of pneumothorax allows air to enter and exit the pleural cavity freely?
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What type of allergic reaction is associated with pneumonitis (allergic alveolitis)?
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What is the primary consequence of untreated atelectasis?
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What occurs during the first stage of asphyxia?
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What characterizes the third stage of asphyxia?
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Which physiological change is associated with the second stage of asphyxia?
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What initiates the increased breathing and heart activity during asphyxia?
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What can happen if respiratory arrest occurs during the fourth stage of asphyxia?
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Which of the following statements about carbon dioxide levels during asphyxia is true?
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In the context of asphyxia, what is mydriasis indicative of?
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What is the role of increased sympathetic tone in the first stage of asphyxia?
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Which type of respiratory rhythm disturbance is characterized by rapid, shallow breathing often observed with pulmonary pathology?
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Which breathing pattern is specifically marked by periods of apnea interspersed with gradual changes in breath depth?
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What is the primary sign of respiratory failure that does not occur during an unconscious state?
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Which respiratory condition is characterized by a decrease in the respiratory rate and involves deep breaths due to narrowing of the upper respiratory tract?
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Which type of cough is primarily reflexogenic and serves to remove mucus and foreign substances from the respiratory tract?
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What term describes the temporary cessation of breathing due to severe hypocapnia?
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Which of the following breathing patterns is characterized by prolonged inspiration followed by a short expiration and may occur due to brain injury?
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Which respiratory condition typically results from increased resistance to airflow due to upper respiratory tract narrowing?
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What type of dyspnea is primarily associated with restrictive diseases such as pneumonia and pneumothorax?
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Which of the following is NOT a disturbance affecting internal respiration?
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Which mechanism primarily mediates the reflex of sneezing?
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What is the primary consequence of prolonged coughing on the respiratory system?
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Which condition involves a feeling of air deprivation, often accompanied by rapid breathing due to increased inspiratory center activity?
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What happens to the resistance in the bronchial lumen if it is narrowed two times?
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Which characteristic is associated with atopic asthma?
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Which of the following factors is NOT associated with the development of non-atopic asthma?
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In the context of asthma, what typically occurs during chronic irritation?
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What is a common effect on the bronchial epithelium due to hyperergic inflammatory reactions in asthma?
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What is the role of the pneumotaxic center in the regulation of respiration?
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What effect does increased blood pressure have on respiratory rate according to peripheral baroreceptors?
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What type of breathing is triggered by irritation of J-receptors in the lungs?
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Which receptors are primarily responsible for narrowing of the airways in response to toxic substances?
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How does the Hering-Breuer reflex function during high pressure in the alveoli?
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What is the primary physiological change that occurs during the first stage of asphyxia?
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What characterizes the second stage of asphyxia?
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What happens during the third stage of asphyxia?
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Which sign indicates severe hypotension during the fourth stage of asphyxia?
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What is the consequence of a significant rise in carbon dioxide levels during asphyxia?
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What physiological response explains the increased sympathetic tone during the first stage of asphyxia?
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What is a primary factor contributing to the development of emphysema?
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What distinguishes closed pneumothorax from open pneumothorax?
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What characterizes valvular pneumothorax?
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Which type of pneumonia involves inflammation primarily located in the alveolar space?
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Which mechanism is involved in the pathophysiology of asthma related to aspirin?
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How does emphysema primarily affect the alveolar structure?
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What is a significant indicator of pneumonia on a clinical level?
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What type of inflammatory reaction is pneumonitis classified under?
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What characterizes Cheyne-Stokes breathing?
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Which of the following breathing patterns is indicative of severe hypercapnia?
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Which type of dyspnea is associated with obstructive diseases such as asthma?
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What is a key aspect of inspiratory dyspnea?
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What is the primary physiological response during apnea?
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Which of the following conditions is characterized by abnormal breathing patterns and significant alterations in airflow?
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What are the primary roles of coughing within the respiratory system?
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Which disturbance involves a trigger in the diaphragmatic muscle and is associated with hiccups?
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What effect does hypercapnia have on cerebral blood vessels?
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What characterizes terminal breathing?
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What is the primary purpose of yawning?
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What primarily leads to the sensation of dyspnea?
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What is the primary difference between dry pleurisy and exudative pleurisy?
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What causes hypoxemia to develop while normocapria is preserved?
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Which condition can lead to pulmonary hypertension through increased resistance in the pulmonary vessels?
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What is the most significant mechanism that affects gas diffusion in cases of pulmonary edema?
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Which peripheral receptor is triggered by decreased blood pH?
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What is the main effect of the Hering-Breuer reflex?
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Which receptor type is irritated during lung congestion and leads to rapid breathing?
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What is the primary function of mechanoreceptors in the respiratory system?
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Study Notes
Lung Disease and Hypoventilation
- Hypoventilation can be categorized as obstructive or restrictive.
- Obstructive hypoventilation is caused by difficulty exhaling and may be a result of airway obstruction in the upper or lower respiratory tract.
- Restrictive hypoventilation is caused by difficulty inhaling and can originate from pulmonary or extra-pulmonary sources.
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Common causes of Obstructive hypoventilation:
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Upper Tract:
- Fluids (water, sputum)
- Tumors
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Lower Tract:
- Asthma: Impaired bronchial obstruction
- Chronic bronchitis: Prolonged irritation of respiratory tract mucous membrane leading to airway narrowing
- Bronchiectasis: Persistent respiratory infection and airway obstruction leading to dilation of bronchi and bronchioles.
- Emphysema: Destructive changes in distal airway walls (acini) and alveolar cavity expansion leading to obstructed airflow.
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Upper Tract:
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Common causes of Restrictive hypoventilation:
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Pulmonary causes:
- Pneumonia: Exudate formation in alveoli caused by infection.
- Tuberculosis (TB): Infection leading to inflammation of lung tissue.
- Atelectasis: Alveolar collapse due to bronchi blockage, external pressure, or scarring.
- Pneumosclerosis: Scar tissue formation in lung parenchyma.
- Pulmonary edema: Fluid buildup in the lungs.
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Extra-pulmonary causes:
- Pleural Pathology (pleurisy, pneumothorax, hydrothorax, hemothorax): Effusion of fluid or air in the pleural space.
- Diaphragm mobility damage: Compromised diaphragmatic function due to phrenic nerve injury, tumors, or surgery.
- Respiratory muscle disorders: Muscle weakness or disorders affecting breathing (e.g., myositis).
- Chest excursion difficulties: Impaired thoracic expansion due to kyphosis, lordosis, or other conditions.
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Pulmonary causes:
Emphysema Pathophysiology
- Protease-Anti-protease system imbalance: Proteases (elastase, collagenase) break down proteins (like elastin) in the lungs, while anti-proteases (like α-1 antitrypsin) protect lung tissue. This imbalance can lead to alveolar destruction.
- Oxidant-antioxidant system imbalance: Oxidants (reactive oxygen species) damage lung tissue, while antioxidants (glutathione, superoxide dismutase) protect against this damage. An imbalance can contribute to emphysema development.
- Chronic irritation of the alveolar wall: Chronic exposure to irritants (like smoke) can lead to inflammation in the alveoli which releases leukocytes (neutrophils, macrophages) that further exacerbate damage.
- Anti-protease deficiency: Insufficient levels of α-1 antitrypsin can make the lung tissue more vulnerable to protease activity.
- Smoking: Smokers have decreased antioxidant capacity and increased protease activity.
Atelectasis
- Characterized by alveolar collapse and closure of the lumen.
- Three types:
- Resorption atelectasis: Bronchi blockage causes reabsorption of alveolar air, leading to collapse.
- Compression atelectasis: External pressure on the lungs, such as from tumors or fluid accumulation, causes collapse.
- Contraction atelectasis: Scarring (pneumosclerosis) in the lung parenchyma leads to permanent collapse.
Pneumothorax
- Occurs when air enters the pleural space (space between the lung and chest wall), collapsing the lung.
- Three Types:
- Closed pneumothorax: Air in the pleural space does not communicate with the external environment.
- Open pneumothorax: Air can freely enter and leave the pleural space through an open wound.
- Valvular pneumothorax: Air enters during inhalation and is trapped in the pleural space during exhalation, progressively increasing pressure.
Pneumonia
- An inflammatory process in the lung tissue caused by infection.
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Types of pneumonia:
- Bacterial (typical): Bacteria like pneumococcus, streptococcus, staphylococcus, and klebsiella multiply in the alveoli, causing strong exudation (fluid build-up) and infiltration.
- Non-bacterial (atypical): Organisms like mycoplasma, chlamydia, adenoviruses, and influenza viruses infect the lung tissue, leading to inflammation and often alveolar infiltration.
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Pneumonia can be:
- Acute or chronic
- Community-acquired or nosocomial
Pneumonitis (Allergic Alveolitis)
- Inflammation of the alveoli caused by a hypersensitivity reaction to foreign antigens.
- Characterized by gradual fibrosis (scarring) of the alveolar and interstitial tissue.
Pleurisy
- Inflammation of the pleura.
- Can be caused by lung infections, cancer, autoimmune diseases, or other conditions.
Pulmonary Hypertension
- High blood pressure in the pulmonary arteries.
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Types:
- Precapillary: Compression of pulmonary arterioles due to conditions like emphysema, chronic obstructive pulmonary disease (COPD) or pulmonary embolism.
- Postcapillary: Caused by compression of pulmonary veins, often seen in mitral stenosis or left ventricular failure
- Mixed: Combinations of precapillary and postcapillary factors.
- Complications: Right-sided heart failure (cor pulmonale).
Pulmonary Edema
- Fluid accumulation in the lungs.
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Mechanisms:
- Hydrostatic: Increased capillary pressure due to conditions like left ventricular failure.
- Oncotic: Decrease in blood protein levels, leading to fluid leaking into the alveoli.
- Membrane: Increased permeability of capillary walls due to infection, inflammation, or toxins.
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Stages:
- Interstitial edema: Fluid accumulates in the interstitial space causing compression of bronchi and alveoli.
- Alveolar edema: Fluid enters the alveoli causing dyspnea and even asphyxia in severe cases.
Ventilation Perfusion Index (V/P)
- Measures the effectiveness of gas exchange in the lungs.
- Normal V/P: 0.8-1.0
- V/P > 1: Increased alveolar ventilation relative to perfusion, suggesting conditions like dead space ventilation (e.g., pulmonary embolism)
- V/P < 0.8: Increased perfusion relative to ventilation, suggesting poor gas exchange (e.g., conditions affecting lung tissue like pneumonia or fibrosis).
Respiratory Rate
- Normal respiratory rate at rest: 16-20 breaths per minute.
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Types of respiratory rhythm disturbances:
- Tachypnea or Polypnea: Fast, shallow breathing often due to pulmonary conditions like pneumonia or pulmonary edema.
- Hyperpnea: Rapid, deep breathing caused by increased oxygen demand (exercise, anemia, etc.).
- Bradypnea: Slow, deep breathing due to upper airway obstruction (tumor, edema, foreign bodies).
- Apnea: Temporary cessation of breathing due to severe hypocapnia (low CO2 levels).
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Periodic breathing: Regularly recurring periods of apnea alternating with normal breathing. This can be divided into Cheyne-Stokes breathing and Biot breathing.
- Cheyne-Stokes breathing: Alternating periods of increased and decreased depth of respiration followed by apnea.
- Biot breathing: Short periods of deep breaths followed by periods of apnea.
Terminal Breathing
- Breathing patterns observed in dying patients.
- **Types: **
- Apneustic breathing: Prolonged inspiration followed by a brief exhalation, often due to brain injuries or poisoning.
- Gasping breathing (agonal breathing): Rare, shallow breaths, indicating extreme respiratory distress.
Dyspnea
- Feeling of shortness of breath or air hunger.
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Types:
- Inspiratory dyspnea: Difficulty inhaling.
- Expiratory dyspnea: Difficulty exhaling.
- Mixed dyspnea: Difficulty both inhaling and exhaling.
Coughing
- Protective reflex to clear airways of mucus, foreign substances, or irritants.
- Mechanism: A deep inhalation followed by a forceful exhalation, propelled by the closure of the epiglottis and vocal cords.
- Prolonged coughing: Can damage lung tissue and contribute to emphysema.
Sneezing
- Protective reflex to clear the nasal passages of irritants.
- Mechanism: Strong exhalation through the nose initiated by the trigeminal nerve.
Hiccups
- Sudden, involuntary spasms of the diaphragm causing a characteristic "hic" sound.
- Causes: Irritation of the diaphragm, diaphragmatic nerves, or central nervous system.
Yawning
- Deep, prolonged inhalation followed by an exhalation.
- Purpose: To increase oxygen supply to the brain and stretch the alveoli.
- Pathological yawning: Can be a sign of brain hypoxia.
Internal Respiration
- The exchange of gases between blood and tissues.
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Factors affecting oxygen transport:
- Oxygen capacity of the blood: The amount of oxygen that can be carried by 100 mL of blood.
- Ability of oxygen to bind to hemoglobin: Factors that influence oxygen binding to hemoglobin, like partial pressure of oxygen, body temperature, and blood pH level.
- Dissociation of oxyhemoglobin: How readily oxygen is released from hemoglobin in the tissues.
- Blood flow and microcirculatory network: Effective blood circulation to the tissues.
Carbon Dioxide Transport
- Primarily transported in the blood in the form of bicarbonate and carbhemoglobin (CO2 bound to hemoglobin).
- Hypercapnia (high CO2): Can lead to increased intracranial pressure and impaired cerebral circulation.
- Hypocapria (low CO2): Can cause cerebral vasospasm and brain hypoxia
Oxygen Utilization Index
- Measures the proportion of oxygen absorbed by tissues.
- Expressed as a percentage of the difference between oxygen content of arterial and venous blood.
- A decrease in blood flow velocity, arterial oxygen content, or oxygen extraction by tissues can lower the oxygen utilization index.
Disturbance of Biological Oxidation
- Impaired energy production in cells.
- Causes: Vitamin deficiencies (B1, B2, PP), inhibition of cytochrome oxidase (e.g., cyanide poisoning).
Stages of Asphyxia
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Stage 1:
- Increased respiratory activity, leading to difficulty inhaling (inspiratory dyspnea)
- Increased sympathetic tone
- This increase in respiratory activity is explained by rising CO2 levels.
-
Stage 2:
- Respiratory center starts to weaken
- Difficulty exhaling (expiratory dyspnea)
- Increased parasympathetic tone
- This stage is explained by hypercapnia’s effect on the parasympathetic system.
-
Stage 3:
- Respiratory arrest occurs due to the respiratory center's delayed activity
- This stage lasts for 1-2 minutes
- Significant decrease in blood pressure (hypotension)
- Reflexes are lost
- Pupils dilate (mydriasis)
- Gasping breaths
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Stage 4:
- Loss of consciousness
- Very slow pulse
- Severe hypotension
- Respiratory center paralysis leads to death
- This stage occurs 5-15 minutes after respiratory arrest, but a heart rate may continue within this time, meaning resuscitation is still possible.
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During asphyxia, increased carbon dioxide levels and decreasing oxygen levels initially stimulate the respiratory and vasomotor centers. This leads to increased breathing, heart activity, and blood pressure.
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However, as carbon dioxide continues to rise, it eventually inhibits these centers.
Bronchial Lumen Narrowing
- Narrowing bronchial lumen by two times increases resistance 16 times (Poiseuille's Law)
Asthma
- Asthma can be classified into atopic and non-atopic forms.
- Atopic asthma is associated with Type I hypersensitivity reactions and hereditary predisposition to allergic diseases.
- Non-atopic asthma does not involve allergic (immune) mechanisms, nor does it have a hereditary predisposition, and has normal IgE synthesis.
- Non-atopic asthma is associated with high eosinophils synthesis, bronchial epithelium damage, increased mucus secretion, and hypertrophy of the bronchial muscle layer wall.
- Non-atopic asthma is characterized by chronic irritation and a decreased threshold of subepithelial parasympathetic receptors.
- Infections can associate with allergic, pseudo-allergic, and non-allergic forms of asthma.
- Aspirin-related asthma develops in pseudo-allergic and non-allergic mechanisms.
- Asthma associated with the profession develops in non-allergic mechanisms
Emphysema
- Emphysema is characterized by terminal bronchiole obstruction and destructive changes in the wall of the distal part (acini).
- Emphysema leads to an expansion of the alveolar cavities due to the atrophy of interalveolar septa, resulting in large air bags.
- Emphysema is driven by an imbalance in the protease-antiprotease system and the oxidant-antioxidant system.
- Proteases, like elastase and collagenase, break down proteins in the lung tissue.
- Antiproteases, like α1 protease, protect lung tissue.
- Oxidants, like reactive oxygen species (ROS), damage lung tissue.
- Antioxidants, like glutathione and superoxide dismutase, protect lung tissue.
- Chronic irritation of the alveolar wall leads to increased protease release from leukocytes (neutrophils and macrophages) and increased ROS production, damaging the alveolar protein wall.
- A deficiency in antiproteases and smoking can also disrupt this balance and lead to emphysema.
Respiratory Disorders: Restrictive Hypoventilation
- Atelectasis is characterized by wrinkling of the alveoli and closure of their lumens.
- Resorption atelectasis occurs when blockage in the bronchi lumen leads to reabsorption of air in the alveoli, closing the lumens.
- Compression atelectasis occurs due to external compression of the lungs, leading to the growth of connective tissue in the lung parenchyma (pneumosclerosis) and irreversible contraction.
- Pneumothorax is characterized by air accumulation in the pleural cavity, compressing the lungs due to increased pleural cavity pressure.
- Three types of pneumothorax:
- Closed: air in the pleural cavity loses contact with the external environment.
- Open: air enters and leaves the pleural cavity freely.
- Valvular: air enters during inhalation, but cannot escape during exhalation due to a valve mechanism, leading to equalized pleural cavity pressure and stopped air flow.
Pneumonia
- Pneumonia is an inflammatory process in lung tissue that can be bacterial (atypical) or non-bacterial (atypical).
- Bacterial pneumonia is typically caused by bacteria like pneumococci, streptococci, staphylococci, and Klebsiella, which multiply in the alveolar cavity and cause inflammatory processes.
- Non-bacterial pneumonia is caused by microorganisms like Mycoplasma, chlamydia, adenoviruses, and influenza viruses and spreads from the alveolar cavity to the interstitial region.
Pneumonitis (Allergic Alveolitis)
- Pneumonitis is a hypersensitivity reaction of the alveoli and interstitial tissue to an exogenous antigen.
- This is a type 3 or 4 allergic reaction characterized by damage and gradual fibrosis of the alveolar wall and interstitial tissue.
- Alveolar or interstitial edema can occur.
- The Hering-Breuer reflex is enhanced.
- Dyspnea develops.
Pleurisy
- Pleurisy is an inflammatory disease of the pleura.
- It can develop due to various reasons, including atelectasis.
- Can cause an arteriovenous shunt.
Respiratory System Regulation
- The respiratory center in the medulla oblongata controls inspiration and expiration, receiving impulses from the pneumotaxic and apneustic centers in the pons.
- The pneumotaxic center inhibits inhalation and enhances exhalation.
- The apneustic center enhances inhalation.
- Exhalation center neurons are not involved in normal breathing.
- Peripheral receptors located in the synocarotid region include:
- Chemoreceptors: respond to changes in blood pH.
- Baroreceptors: regulate respiration according to blood pressure (increased BP decreases respiratory rate).
- Mechanoreceptors.
- Irritant receptors: found between epithelial cells of the respiratory tract, causing airway narrowing to protect the lung from toxic substances.
- J-receptors located in interstitial regions are stimulated during lung congestion, leading to shallow, rapid breathing.
- The Hering-Breuer reflex (infirmation reflex) triggers exhalation when alveolar pressure is high, preventing overinflation of the lungs and becoming more sensitive in rapid, shallow breathing.
Impaired Respiration
- Impaired respiration can be central (medulla oblongata) or efferent.
- Causes of impaired respiration include:
- Organic changes like edema and tumors.
- Functional changes like psychosis and anemia.
- Impaired respiration can slow down or inhibit impulses, disrupting voluntary and involuntary breathing.
- Afferent impulses can be increased or decreased, affecting normal respiratory rate (eupnea), which is 16-20 per minute at rest.
- Respiratory arrest can occur while sleeping (Ondine's curse).
Respiratory Rhythm Disturbances
- The following are different respiratory rhythm disturbances:
- Tachypnea (Polypnea): rapid, superficial respiration observed in pulmonary pathology.
- Hyperpnea: rapid, deep breathing observed in increased oxygen demand.
- Bradypnea: decreased respiratory rate and deep breaths, caused by narrowing of the lumen of the upper respiratory tract.
- Apnea: temporary respiratory arrest caused by severe hypocapnia.
- Periodic breathing: normal respiratory rhythm accompanied by regularly recurring apnea.
- Cheyne-Stokes breathing: inspiration gradually deepens and accelerates, reaching a maximum, then gradually decreases, and ends in apnea.
- Biot breathing: sudden accelerated deep breaths followed by apneic periods.
- Terminal breathing: occurs in the period between life and death.
- Apneustic breathing: prolonged acts of inspiration followed by short acts of exhalation.
- Gasping breathing (agonal breathing): separate (rare) acts of inspiration.
Dyspnea
- Dyspnea is the feeling of lack of air.
- It is a primary sign of respiratory failure.
- It can be inspiratory, expiratory, or mixed.
- It occurs due to increased activity of the inspiration center or weakening of the inhibition system.
- It can be fast and deep or slow and shallow.
Coughing
- Coughing is a reflexogenic zone located in the respiratory tract wall, lung tissue, pleura, diaphragm, and epiglottis.
- The inspiratory center is strongly stimulated, resulting in a deep, short inhalation that fills the lungs with air.
- The epiglottis closes, increasing pressure in the lungs.
- Exhalation opens the epiglottis and vocal cords and air explodes outward.
- Coughing acts as a protective function to remove mucus and foreign substances from the respiratory tract.
- Prolonged coughing damages the interalveolar septa, leading to emphysema and impaired general circulation.
- Coughing is mediated by the vagus nerve.
Sneezing
- Sneezing is a protective reflex triggered by receptors in the nasal mucosa.
- Signals are transmitted via the trigeminal nerve.
- The pharynx is squeezed, but not the epiglottis.
- Prolonged sneezing can cause dyspnea.
Hiccups
- Hiccups are intense acts of inspiration caused by the contraction of the diaphragm, stomach, and glottis.
- They occur due to irritation of the diaphragmatic muscle, diaphragmatic nerves, or damage to the central nervous system.
Yawning
- Yawning is a deep, long breath that stretches non-functional alveoli and increases air in the lungs, followed by energetic exhalation.
- Yawning aims to improve oxygen supply in the body and can be observed in pathological conditions like brain hypoxia.
Internal (Tissue) Respiration
- Internal respiration involves the transport of oxygen from the lungs to the tissues and carbon dioxide from tissues to the lungs.
- Oxygen transport depends on:
- Oxygen capacity of the blood: content of oxygen in 100 mL of blood (16.5-20.5 vol) and influenced by partial pressure of oxygen in the alveoli and blood, body temperature, blood pH, levels of 2,3-diphosphoglycerate (2,3 DPG), and ATP in erythrocytes.
- Ability of oxygen to bind to hemoglobin.
- Dissociation of oxyhemoglobin.
- Level of blood circulation and the microcirculatory network.
- Carbon dioxide is transported in the form of compounds with bicarbonate and hemoglobin (carbaminohemoglobin).
- Hypercapnia expands cerebral vessels, increasing intracranial pressure and impairing cerebral circulation.
- Hypocapria causes spasm of cerebral vessels and brain hypoxia.
- The oxygen utilization index is the amount of oxygen absorbed by the tissues.
- A decrease in blood flow velocity can cause a decrease in oxygen content in arterial blood and a lower index.
Disturbances in Biological Oxidation
- Disturbances in biological oxidation can be caused by:
- Deficiency in vitamins B1, B2, PP, etc.
- Inhibition of cytochrome oxidase.
Asphyxia Stages
- Asphyxia is characterized by stages that involve a progression of respiratory and circulatory changes:
- First Stage: acute increase in respiratory center activity, inspiratory dyspnea, and increased sympathetic tone.
- Second Stage: weakening of the respiratory center, expiratory dyspnea, and increased parasympathetic tone.
- Third Stage: respiratory arrest (1-2 minutes), no reflexes, mydriasis, severe hypotension, and gasping breathing.
- Fourth Stage: respiratory center paralysis, severe hypotension, very slow pulse, and death occurs 5-15 minutes after respiratory arrest.
Other Considerations
- During asphyxia, rising carbon dioxide levels and falling oxygen levels stimulate the respiratory and vasomotor centers, increasing breathing, heart activity, and blood pressure. However, continued carbon dioxide buildup eventually inhibits it all.
- The V/P index can remain within the normal range due to compensatory mechanisms, despite uneven ventilation or the presence of lung disease.
Pleural Cavity
- During exudative pleurisy, fluid accumulates in the pleural cavity, leading to hydrothorax.
- Hemothorax refers to blood accumulating in the pleural cavity.
- Chylothorax refers to lymph accumulating in the pleural cavity.
Alveolar Diffusion
- Alveolar diffusion is the process of oxygen transferring from the alveolar cavity to the pulmonary capillaries, while carbon dioxide moves in the opposite direction.
- The partial pressure of oxygen (PaO2) in the blood is lower than in the alveolar air.
- Blood entering the lungs has a PaO2 of 40 mmHg, while blood returning to the heart has a PaO2 of 100 mmHg.
- The partial pressure of carbon dioxide (PCO2) in the blood at the beginning of the pulmonary capillaries is 46 mmHg, decreasing to 40 mmHg at the end.
Disturbance of Alveolar Diffusion
- Factors that can disturb alveolar diffusion include:
- Reduced surface area due to conditions like pneumonia, allergic alveolitis, or pulmonary edema.
- Increased thickness of the alveolar-capillary membrane (ACM), as seen in respiratory distress syndrome of newborns.
- Altered solubility and molecular weight of gases, with carbon dioxide diffusing 20 times faster than oxygen.
- Increased blood flow velocity in the pulmonary capillaries, reducing time for red blood cells to bind with oxygen.
Disturbance of Lung Perfusion
- Reduced perfusion to the lungs can be caused by:
- Decreased pressure in the right ventricle (e.g., shock, collapse).
- Increased pressure in the left atrium (e.g., mitral stenosis).
- Increased resistance in the pulmonary vessels (e.g., reflex spasm, thromboemboli in pulmonary arterioles).
- Lung perfusion disturbances can lead to pulmonary hypertension.
Pulmonary Hypertension
- Six main causes of pulmonary hypertension include:
- Euler-Lillestrand reflex
- Kitayev reflex
- Increased intra-alveolar pressure
- Decreased total area of capillary network (e.g., atelectasis)
- Atriovenous shunt
- Compensatory mechanisms that can maintain a normal V/P index despite uneven lung ventilation.
Disturbance in Regulation of Respiratory System
- The respiratory center in the medulla oblongata controls inspiration and expiration, receiving impulses from:
- Pneumotaxic and apneustic centers in the Pons
- Peripheral chemoreceptors, baroreceptors, and mechanoreceptors
- Cerebral cortex
- The pneumotaxic center inhibits inhalation and enhances exhalation.
- The apneustic center enhances inhalation.
- Neurons of the exhalation center are inactive during normal breathing but become active during strenuous physical activity.
Peripheral Receptors
- Peripheral receptors are located in the:
- Sinocarotid region (chemoreceptors and baroreceptors)
- Respiratory tract (mechanoreceptors and irritant receptors)
- Interstitial regions (J-receptors)
- Peripheral chemoreceptors are stimulated by a decrease in blood pH.
- Peripheral baroreceptors regulate respiration based on blood pressure (increased BP decreases respiratory rate).
- The Hering-Breuer reflex triggers exhalation when alveolar pressure is high, preventing overinflation of the lungs.
Impaired Respiration
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Impaired respiration can be caused by:
- Central disturbances (medulla oblongata)
- Functional disturbances (psychosis)
- Organic changes (edema, tumors)
- Anemia
- Impaired respiration can lead to respiratory arrest in severe cases.
- The curse of Undine refers to the involuntary cessation of breathing during sleep due to a neurological impairment.
Types of Respiratory Rhythm Disturbances
- Common types of respiratory rhythm disturbances include:
- Tachypnea or Polypnea: Rapid, shallow breathing often associated with lung pathologies (e.g., pneumonia, pulmonary edema).
- Hyperpnea: Rapid, deep breathing observed during increased oxygen demands (e.g., exercise, anemia).
- Bradypnea: Decreased respiratory rate with deep breaths, often due to narrowing of the upper respiratory tract (tumor, edema, foreign body).
- Apnea: Temporary respiratory arrest occurring in severe hypocapnia.
- Pickwick syndrome: Apnea during sleep due to obesity.
Periodic Breathing
- Periodic breathing is characterized by recurring periods of apnea within a normal respiratory rhythm.
- Two forms of periodic breathing include:
- Cheyne-Stokes breathing: Graded increase in inspiration followed by gradual decrease and apnea.
- Biot breathing: Periodic deep breaths followed by periods of apnea.
- Periodic breathing can be caused by:
- Brain traumas
- Heat strokes
- Decompensated heart defects
Pathogenesis of Periodic Breathing
- The pathogenesis of periodic breathing often involves:
- Weakness or decrease in excitability of the respiratory center.
- Inability of carbon dioxide to stimulate the respiratory center, resulting in apnea.
- Increased carbon dioxide levels eventually stimulate the respiratory center again.
Terminal Breathing
- Terminal breathing is a sign of impending death.
- Two forms of terminal breathing include:
- Apneustic breathing: Prolonged inspiration followed by short exhalation, often associated with brain injuries and poisonings.
- Gasping breathing (agonal breathing): Rare, sporadic inspiration with all muscles working, suggesting the agonal stage of death.
Dyspnea
- Dyspnea is the subjective feeling of shortness of breath.
- It is a prominent sign of respiratory failure.
- Dyspnea can be caused by increased activity of the inspiratory center or weakening of the inhibitory system.
- Breathing can be rapid and deep or slow and superficial.
- Three types of dyspnea include:
- Inspiratory dyspnea: Often associated with restrictive lung diseases (pneumonia, atelectasis).
- Expiratory dyspnea: Often associated with obstructive lung diseases (asthma, emphysema).
- Mixed dyspnea: Can be caused by a combination of restrictive and obstructive lung diseases.
Coughing
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Coughing is a reflex triggered by receptors in:
- Wall of the respiratory tract
- Lung tissue
- Pleura
- Diaphragm
- Coughing involves:
- Deep inspiration filling the lungs with air
- Closing of the epiglottis
- Increased pressure in the lungs, with exhalation causing the epiglottis and vocal cords to open
- Closing of the nasal cavity by the soft palate
Sneezing
- Sneezing is a protective reflex triggered by receptors in the nasal mucosa.
- Signals are transmitted through the trigeminal nerve.
- It involves squeezing the pharynx (not the epiglottis).
Hiccups
- Hiccups are intense inspiratory spasms caused by contraction of the diaphragm, stomach, and glottis.
- They can be caused by:
- Irritation of diaphragmatic muscle receptors
- Irritation of diaphragmatic nerves
- Damage to the central nervous system
Yawning
- Yawning is a deep, long inspiration that stretches non-functioning alveoli, followed by a vigorous exhalation.
- It aims to improve oxygen supply.
- Yawning can also occur in pathological conditions (brain hypoxia).
Disturbance of Internal (Tissue) Respiration
- Internal respiration involves oxygen transport from the lungs to the tissues and carbon dioxide transport from tissues to the lungs.
- Oxygen transport depends on:
- Oxygen capacity of blood: Content of oxygen in 100 mL of blood.
- Ability of oxygen to bind to hemoglobin: Influenced by factors such as alveolar and blood oxygen partial pressure, temperature, pH, and levels of 2,3-diphosphoglycerate (2,3 DPG) and ATP in red blood cells.
- Dissociation of oxyhemoglobin: Release of oxygen from hemoglobin.
- Level of blood circulation and microcirculatory network: Efficient delivery of oxygen to tissues.
Carbon Dioxide Transport
- Carbon dioxide is transported in the blood as bicarbonate, carbhemoglobin, and dissolved gas.
- Hypercapnia dilates cerebral vessels, leading to increased intracranial pressure and impaired cerebral circulation.
- Hypocapnia causes cerebral vessel spasms and brain hypoxia.
Oxygen Utilization Index
- The oxygen utilization index measures the percentage of oxygen absorbed by tissues.
- It is calculated as the ratio of arteriovenous oxygen difference to arterial blood oxygen content.
- Decreased blood flow velocity or reduced arterial oxygen content can lead to a lower oxygen utilization index.
Disturbance of Biological Oxidation
- Disturbances in biological oxidation can be caused by:
- Deficiency of vitamins (B1, B2, PP)
- Cytochrome oxidase inhibition (e.g., cyanide poisoning, alcohol)
- Imbalance between oxidation and phosphorylation (e.g., thyrotoxicosis, nitrate poisoning)
- Mitochondrial damage and ATP deficiency (e.g., cachexia, sepsis, radiation sickness)
- These conditions can lead to histotoxic hypoxia, where oxygen is present in arterial blood but is not used by tissues.
Non-Respiratory Functions of Lungs
- The lungs play several non-respiratory functions, including:
- Metabolic functions: Formation of angiotensin II, inactivation of substances like bradykinin, norepinephrine, serotonin.
- Hemostasis functions: Synthesis of coagulation and anticoagulant factors (thromboplastin, heparin, plasminogen activator, prostacyclin, thromboxane A2).
- Protective functions: Air purification (alveolar macrophages, mucociliary apparatus, blood filtration), removing accumulated substances during pathological processes.
- Lymphatic drainage: Removing accumulated substances in the lungs during pathological processes.
Acute Lung Injury (ARDS)
- Acute respiratory distress syndrome (ARDS) is characterized by diffuse damage to the alveolar capillaries and alveolar epithelium.
- ARDS leads to pulmonary edema and acute respiratory failure.
- Adult ARDS: Characterized by diffuse lung tissue damage, necrosis of alveolar epithelium, increased capillary permeability, and alveolar edema.
- Neonatal ARDS (hyaline membrane disease): Primarily caused by surfactant deficiency, leading to alveolar collapse (atelectasis).
Causes of ARDS
- ARDS can occur due to:
- Direct injury to the lungs (infections, allergic responses, inflammatory processes).
- Extra-pulmonary pathologies (sepsis, pancreatitis, peritonitis, traumatic and burn shock, disseminated intravascular coagulation (DIC)).
- Damage to the alveolar capillary membrane is often due to dysregulation of the acute inflammatory response, leading to excessive inflammation and alveolar epithelium damage.
Asphyxia
- Asphyxia is a severe form of respiratory failure where oxygen transfer to the blood and carbon dioxide removal from the body become impossible.
- Asphyxia can occur due to:
- Squeezing the airway from outside
- Drowning
- Laryngeal edema
- Severe bronchospasm
- Respiratory muscle paralysis
- Glottis spasm
Stages of Asphyxia
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Asphyxia progresses through four distinct stages:
- First Stage: Acute increase in respiratory center activity, leading to inspiratory dyspnea and increased sympathetic tone.
- Second Stage: Weakening of the respiratory center, leading to expiratory dyspnea and increased parasympathetic tone.
- Third Stage: Respiratory arrest due to delayed activity of the respiratory center, loss of reflexes, mydriasis (pupil dilation), and severe hypotension.
- Fourth Stage: Respiratory center paralysis, complete respiratory arrest, very slow pulse, gasping breathing, loss of consciousness, and eventual death.
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During the initial stages of asphyxia, the rising carbon dioxide levels and falling oxygen levels stimulate the respiratory and vasomotor centers, leading to increased breathing, heart activity, and blood pressure.
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However, as carbon dioxide levels continue to rise, they eventually inhibit these centers.
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Explore the different types of hypoventilation, including obstructive and restrictive categories. Learn about common causes such as asthma, chronic bronchitis, and emphysema. This quiz will enhance your understanding of lung diseases and their impacts on ventilation.
