Chapter8 Respiratory Terminology

Obstructive Pulmonary Diseases and Airway Pathologies

• Anoxia

  • Complete deprivation or absence of oxygen supply to arterial blood, tissues, or organs, representing the most extreme manifestation of hypoxia.

  • Pathophysiology involves the cessation of oxidative phosphorylation at the cellular level, causing immediate depletion of adenosine triphosphate (ATP), failure of sodium-potassium ATPase pumps, intracellular cellular swelling, and irreversible cellular injury or necrosis within minutes, particularly in high-metabolic neural tissue.

  • Clinical differentiation: Differs from hypoxemia (low oxygen tension in arterial blood) and hypoxia (insufficient tissue oxygenation) by denoting a total cessation of oxygen availability.

• Antitussive

  • Pharmacological class of medications formulated specifically to suppress, inhibit, or alleviate the coughing reflex.

  • Mechanistic classification:

  • Centrally acting antitussives (such as codeine, dextromethorphan) act directly on the cough center located within the medulla oblongata to increase the sensory threshold for coughing.

  • Peripherally acting antitussives (such as benzonatate) anesthetize stretch receptors localized within the respiratory passages, lungs, and pleura, dampening afferent vagal transmission.

  • Clinical indication: Primarily utilized for dry, non-productive coughs that interrupt rest or cause thoracic discomfort; contraindicated in productive coughs where retention of secretions can induce atelectasis and secondary pneumonia.

• Aphonia

  • Total loss or inability to produce vocal sounds using the vocal cords.

  • Etiology encompasses bilateral vocal cord paralysis (often secondary to recurrent laryngeal nerve trauma), acute severe inflammation or edema of the vocal folds, structural neoplasia, or psychogenic/conversion disorders.

  • Differential distinction: Differentiated from dysphonia, which represents partial phonatory impairment or vocal hoarseness without total voice extinction.

• Asbestosis

  • A progressive, fibrosing pneumoconiosis caused by the chronic inhalation and parenchymal deposition of microscopic asbestos mineral fibers.

  • Pathogenesis: Inhaled fibers penetrate distal alveolar spaces, where alveolar macrophages undergo frustrated phagocytosis, releasing pro-inflammatory cytokines, reactive oxygen species, and fibrogenic factors (e.g., transforming growth factor-beta). This cascade leads to diffuse interstitial pulmonary fibrosis, pleural plaques, and honeycombing.

  • Clinical hallmarks: Progressive exertional dyspnea, non-productive cough, end-inspiratory bibasilar dry crackles (crepitations), and digital clubbing, with marked long-term risk of malignant mesothelioma and bronchogenic carcinoma.

• Asphyxia

  • A life-threatening state of severe physiological oxygen starvation combined with hypercapnia, stemming from systemic impairment of respiration.

  • Mechanisms include external airway occlusion, mechanical thoracic compression, inhalation of toxic gases (e.g., carbon monoxide, cyanide), or acute neurological failure of the respiratory drive.

  • Pathological consequence: Progressive hypoxemia ($PaO_2$ decline) concurrent with acute respiratory acidosis ($PaCO_2 > 45\,\text{mmHg}$ and pH collapse), terminating in cardiac arrest, hypoxic-ischemic encephalopathy, and death if not emergently reversed.

• Asthma

  • Chronic inflammatory disorder of the conducting airways characterized by bronchial hyperresponsiveness, reversible airflow obstruction, and chronic inflammatory tissue remodeling.

  • Cellular mechanisms involve mast cells, eosinophils, T-helper 2 (Th2) lymphocytes, and immunoglobulin E (IgE), resulting in bronchial smooth muscle spasm, excessive mucus hypersecretion, mucosal edema, and epithelial shedding.

  • Symptom triad: Episodic wheezing, dyspnea, and chest tightness accompanied by cough (classically nocturnal or early morning); spirometry shows reversible airflow limitation with a significant increase in forced expiratory volume in 1 second ($FEV_1$) of at least $12\%$ and $200\,\text{mL}$ post-bronchodilator administration.

• Atelectasis

  • Complete or partial collapse of lung tissue, involving the deflation or non-aeration of alveoli within a segment, lobe, or entire lung.

  • Classifications:

  • Resorption (obstructive): Intrinsic obstruction of an airway (e.g., mucus plug, foreign body, neoplasm) prevents alveolar ventilation, causing entrapped air to resorb into the bloodstream.

  • Compression: External pressure exerted on lung parenchyma by pleural effusion, hemothorax, pneumothorax, or elevated hemidiaphragms.

  • Contraction (cicatrization): Localized or generalized pulmonary fibrotic changes that prevent full alveolar expansion.

  • Surfactant dysfunction (adhesive): Loss or inactivation of surfactant leading to high alveolar surface tension, seen in acute respiratory distress syndrome (ARDS).

• Retina

  • The light-sensitive neurosensory layer lining the inner posterior globe of the eye, directly vulnerable to systemic fluctuations in arterial oxygenation and blood flow.

  • Pulmonary relevance: Susceptible to structural and microvascular manifestations during severe systemic hypoxia, anoxia, hypercapnia, or respiratory failure, which can present as retinal vein dilation, retinal hemorrhages, or papilledema secondary to hypercapnia-induced intracranial hypertension.

• Bronchiectasis

  • Chronic, irreversible, abnormal dilatation and architectural destruction of the medium-sized and large bronchi caused by cycles of transmural airway infection and inflammation.

  • Pathogenesis follows Cole's vicious cycle hypothesis: Impaired mucociliary clearance or primary immunodeficiency allows microbial colonization, persistent neutrophilic inflammation, elastase release, and degradation of cartilage and muscular components of the bronchial wall.

  • Diagnostic features: High-resolution computed tomography (HRCT) demonstrates the "signet-ring sign" (bronchial lumen diameter exceeding the diameter of its adjacent pulmonary artery branch); symptoms include copious production of foul-smelling, purulent sputum, recurrent hemoptysis, and clubbing.

• Bronchodilator

  • Therapeutic agent designed to induce smooth muscle relaxation throughout the bronchial tree, reversing bronchoconstriction and increasing luminal airway caliber.

  • Major therapeutic categories:

  • Beta-2 adrenergic agonists (e.g., short-acting albuterol, long-acting salmeterol): Stimulate adenylyl cyclase, augmenting intracellular cyclic adenosine monophosphate (cAMP) and causing smooth muscle relaxation.

  • Anticholinergics/muscarinic antagonists (e.g., ipratropium, tiotropium): Block acetylcholine at muscarinic $M_3$ receptors, impeding parasympathetic bronchoconstriction and glandular mucus secretion.

  • Methylxanthines (e.g., theophylline): Inhibit phosphodiesterase enzymes and antagonize adenosine receptors.

• Bronchorrhea

  • Excessive, abnormal production and expectoration of watery bronchial secretions, formally defined as the daily production of more than $100\,\text{mL}$ of thin sputum.

  • Underlying conditions include invasive mucinous adenocarcinoma of the lung (formerly bronchioloalveolar carcinoma), severe chronic bronchitis, bronchiectasis, organophosphate poisoning, and asthma.

• Bronchoscopy

  • Endoscopic examination, visualization, and procedural intervention of the larynx, trachea, and tracheobronchial tree using an optical instrument.

  • Variations and utility:

  • Flexible bronchoscopy: Utilizes fiber-optic or video systems under conscious sedation for diagnostic inspection, bronchoalveolar lavage (BAL), endobronchial biopsies, and transbronchial needle aspiration.

  • Rigid bronchoscopy: Performed under general anesthesia; provides a patent airway to manage massive hemoptysis, extract foreign bodies, and perform laser photoresection or airway stenting.

• Bronchospasm

  • Acute, involuntary contraction of the smooth muscle encircling the bronchi and bronchioles, narrowing the airway lumen.

  • Clinical manifestations: Manifests as wheezing, tachypnea, cough, and sudden dyspnea; triggered by airway hyperreactivity to allergens, viral respiratory tract infections, cold dry air, chemical irritants, exercise, or pharmacological agents (e.g., non-selective beta-blockers, aspirin).

Clinical Manifestations, Respiratory Patterns, and Airway Interventions

• chain Stokes respiration

  • A distinct, cyclical breathing pattern (clinically known as Cheyne-Stokes respiration) marked by alternating periods of crescendo-decrescendo hyperpnea followed by central hypopnea or central apnea.

  • Pathophysiological mechanism: Driven by abnormal respiratory center sensitivity to arterial carbon dioxide ($PaCO_2$) combined with prolonged lung-to-brain circulation time, causing an overshooting and undershooting ventilatory feedback loop.

  • Associated states: Advanced congestive heart failure, severe neurological trauma, bilateral hemispheric stroke, uremia, and central nervous system depressant intoxication.

• Chronic obstructive pulmonary disease

  • A common, preventable, and treatable chronic lung disease characterized by persistent, progressive airflow limitation that is not fully reversible.

  • Pathological components: Integrates small airway disease (obstructive chronic bronchitis with mucus hypersecretion and peribronchiolar fibrosis) and parenchymal destruction (emphysema with alveolar wall loss), primarily driven by tobacco smoking and occupational exposure to biomass fuels.

  • Functional definition: Confirmed via post-bronchodilator spirometry when the ratio of $FEV_1$ to forced vital capacity ($FVC$) is fixed at $FEV_1/FVC < 0.70$.

• Croup

  • Acute pediatric viral laryngotracheobronchitis, most commonly triggered by human parainfluenza virus types 1 and 2.

  • Clinical manifestations: Subglottic edema leads to a characteristic barking (seal-like) cough, inspiratory stridor, hoarseness, and signs of respiratory distress; radiographically presents with subglottic narrowing known as the "steeple sign" on anteroposterior neck radiographs.

• Cyanosis

  • Bluish or purplish discoloration of the cutaneous and mucosal surfaces caused by an absolute concentration of reduced (deoxygenated) hemoglobin in capillary beds exceeding approximately $5\,\text{g/dL}$ ($50\,\text{g/L}$).

  • Types:

  • Central cyanosis: Involves core mucous membranes, lips, and tongue; indicates severe arterial hypoxemia ($SaO_2 < 85\%$) or right-to-left circulatory shunts.

  • Peripheral cyanosis: Affects extremities (fingers, toes, nail beds); results from local vasoconstriction, peripheral hypoperfusion, exposure to severe cold, or low cardiac output states.

• Cystic fibrosis

  • A lethal, multi-system, autosomal recessive genetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene located on chromosome 7.

  • Pathomechanism: Impairs epithelial chloride and bicarbonate transport across apical membranes, causing dehydrated, thick, hyperviscous secretions that block exocrine glands.

  • Systemic presentations: Persistent respiratory tract colonization by Pseudomonas aeruginosa and Staphylococcus aureus, bronchiectasis, chronic sinusitis, exocrine pancreatic insufficiency, fat malabsorption, meconium ileus, and congenital bilateral absence of the vas deferens (CBAVD).

• Dysphonia

  • Functional or structural impairment of the voice manifesting as abnormal pitch, volume, vocal quality, or hoarseness.

  • Caused by structural anomalies of the vocal folds (nodules, polyps, granulomas), acute laryngitis, vocal fold edema, laryngeal malignancy, or neuromuscular dysfunction.

• Dyspnea

  • A subjective, conscious experience of breathing discomfort composed of qualitatively distinct sensations that vary in intensity.

  • Etiology spans cardiovascular failure, airway obstruction, parenchymal lung diseases, chest wall deformities, neuromuscular weakness, severe anemia, and psychogenic conditions (panic disorders).

• Emphysema

  • A morphological component of chronic obstructive pulmonary disease characterized by abnormal, permanent enlargement of the respiratory airspaces distal to the terminal bronchioles, accompanied by the destruction of alveolar walls without gross fibrosis.

  • Subtypes:

  • Centriacinar (centrilobular): Predominantly involves respiratory bronchioles while sparing distal alveoli; classically affects upper lung lobes and strongly correlates with cigarette smoking.

  • Panacinar (panlobular): Involves all structures from respiratory bronchioles to alveoli; classically affects the lower lung zones and is pathognomonic for alpha-1 antitrypsin deficiency.

  • Paraseptal (distal acinar): Affects peripheral alveolar ducts and sacs near the pleura, predisposing to apical blebs and spontaneous pneumothorax.

• Empyema

  • Accumulation of frank pus or purulent exudate within an anatomical cavity, particularly within the pleural space (empyema thoracis).

  • Stages of development: Exudative stage (sterile parapneumonic fluid), fibropurulent stage (bacterial invasion, dense fibrin deposition, loculation), and organizing stage (fibroblastic pleural peel formation restricting lung expansion).

• Endotracheal intubation

  • Advanced airway management technique involving the insertion of a specialized flexible tube through the oral cavity (orotracheal) or nasal cavity (nasotracheal) into the lumen of the trachea.

  • Indications: Acute respiratory failure, inability to protect the airway against aspiration (Glasgow Coma Scale score $\le 8$), upper airway obstruction, and management of ventilation and oxygenation during general anesthesia.

• Epistaxis

  • Hemorrhage from the nasal cavity or nasopharynx.

  • Anatomical classification:

  • Anterior epistaxis: More frequent; originates from the Kiesselbach plexus (Little area) on the anterior nasal septum; usually manageable with direct pressure, topical vasoconstrictors, or cautery.

  • Posterior epistaxis: Originates from the sphenopalatine artery branches; presents higher risk of airway compromise and aspiration; frequently necessitates posterior balloon tamponade or surgical/endovascular ligation.

• Hemoptysis

  • The expectoration or coughing up of blood or blood-streaked sputum derived from the respiratory tract below the level of the vocal cords.

  • Etiologies: Bronchitis, bronchogenic carcinoma, bronchiectasis, tuberculosis, pulmonary embolism with infarction, and arteriovenous malformations; vascular origin is predominantly the high-pressure bronchial arterial circulation ($\sim 90\%$ of massive cases) rather than the low-pressure pulmonary arterial system.

• Hemothorax

  • Presence of an extravasated collection of blood within the pleural cavity, defined formally as a pleural fluid hematocrit equal to or greater than $50\%$ of the concurrent circulating peripheral blood hematocrit.

  • Etiologies: Blunt or penetrating chest trauma, thoracic surgery, central venous catheterization complications, or non-traumatic etiologies like aortic dissection, neoplasia, or coagulopathies.

• Hypercapnia

  • Pathological elevation of the partial pressure of carbon dioxide in the arterial blood, defined as a $PaCO_2 > 45\,\text{mmHg}$ ($>6.0\,\text{kPa}$).

  • Primary mechanism is alveolar hypoventilation, expressed by the relationship:     $PaCO_2 \propto \frac{\dot{V}_{CO_2}}{\dot{V}_A}$     where $\dot{V}_{CO_2}$ is carbon dioxide production and $\dot{V}_A$ is alveolar ventilation. Leads to systemic vasodilation, cerebral hyperperfusion, somnolence (carbon dioxide narcosis), and respiratory acidosis.

• Hyperpnea

  • An increase in both the depth (tidal volume) and rate of respiration that matches an increased metabolic demand, as seen during rigorous physical exercise, or non-metabolic compensation for systemic metabolic acidosis (e.g., Kussmaul respirations in diabetic ketoacidosis).

• Hyponia

  • State of decreased or abnormally shallow respiration (hypopnea/hyponia), characterized by reduced ventilation amplitude, partial airflow reduction, and diminished respiratory excursions, contributing to hypoxemic episodes and hypercapnic states.

• Hypoxemia

  • Subnormal oxygen tension within arterial blood, defined as an arterial partial pressure of oxygen $PaO_2 < 80\,\text{mmHg}$ ($<10.6\,\text{kPa}$) at sea level, or an arterial oxygen saturation $SaO_2 < 95\%$.

  • Five classic physiological mechanisms: Alveolar hypoventilation, ventilation-perfusion ($V/Q$) mismatch, right-to-left anatomical/physiological shunt, diffusion impairment, and low inspired partial pressure of oxygen ($P_I O_2$).

• Hypoxia

  • Inadequate oxygenation at the cellular and tissue level, preventing normal aerobic mitochondrial respiration and metabolic function.

  • Mechanistic classes:

  • Hypoxemic hypoxia (low $PaO_2$ causing insufficient tissue delivery).

  • Anemic hypoxia (normal $PaO_2$ but reduced functional hemoglobin concentration or capacity, e.g., carbon monoxide poisoning).

  • Circulatory/ischemic hypoxia (diminished tissue perfusion despite normal oxygenation, e.g., cardiogenic shock).

  • Histotoxic hypoxia (cellular inability to utilize oxygen due to enzymatic poisoning, e.g., cyanide inhibition of cytochrome c oxidase).

• Laryngitis

  • Acute or chronic inflammation of the laryngeal mucosa and vocal cords.

  • Features: Hoarseness, vocal fatigue, tickling throat sensations, and dry cough; predominantly caused by viral upper respiratory infections (rhinovirus, influenza, adenovirus) or mechanical vocal strain, with chronic forms exacerbated by gastroesophageal reflux disease (GERD) or environmental toxins.

• Laryngoscopy

  • Endoscopic or visual inspection of the laryngeal structures, epiglottis, and vocal folds.

  • Methodologies include indirect mirror laryngoscopy, flexible fiberoptic nasolaryngoscopy, and direct rigid laryngoscopy (utilized for difficult intubations, biopsy, and micro-laryngeal surgery).

• Laryngospasm

  • Sudden, involuntary muscular contraction and closure of the laryngeal vocal cords mediated by the adductor laryngeal muscles, resulting in transient partial or total upper airway obstruction.

  • Common triggers: Mechanical or chemical irritation of the laryngeal mucosa during perioperative extubation or intubation, light general anesthesia, hypocalcemia, or severe gastroesophageal reflux.

Pleural Effusion and Thoracic Cavity Pathologies

• Mediastinum

  • Central anatomical compartment of the thoracic cavity bounded laterally by the pleural cavities, anteriorly by the sternum, posteriorly by the thoracic vertebral column, superiorly by the thoracic inlet, and inferiorly by the diaphragm.

  • Anatomical subdivisions:

  • Superior mediastinum: Contains the thymus, brachiocephalic veins, superior vena cava, aortic arch, trachea, esophagus, thoracic duct, and vagus and phrenic nerves.

  • Anterior mediastinum: Contains thymic remnants, internal thoracic vessels, adipose tissue, and lymph nodes.

  • Middle mediastinum: Contains the pericardium, heart, ascending aorta, pulmonary trunk, superior and inferior vena cava terminations, and main bronchi.

  • Posterior mediastinum: Contains the descending thoracic aorta, esophagus, azygos and hemiazygos venous systems, thoracic duct, and sympathetic trunks.

• Nebulizer

  • Medical device that converts liquid pharmacological solutions or suspensions into an inhalable mist or aerosol of respirable droplets ($1\,\text{to}\,5\,\mu\text{m}$ in mass median aerodynamic diameter).

  • Mechanism allows direct deposition of therapeutic agents (e.g., beta-agonists, anticholinergics, corticosteroids, mucolytics, inhaled antibiotics) into the lower tracheobronchial tree in acute respiratory distress or when patients cannot coordinate metered-dose inhalers.

• Otolaryngologist

  • A surgical and medical specialist trained in otolaryngology-head and neck surgery (ENT), dedicated to managing disorders of the ears, nose, paranasal sinuses, pharynx, larynx, oral cavity, and adjacent structures of the neck and skull base.

• Pertussis

  • Highly contagious, acute bacterial respiratory infection of the upper and lower respiratory tracts caused by Bordetella pertussis.

  • Triphasic clinical course:

  • Catarrhal stage: Low-grade fever, rhinorrhea, and mild cough (highest infectivity).

  • Paroxysmal stage: Staccato coughing fits terminated by a high-pitched inspiratory "whoop" and post-tussive emesis.

  • Convalescent stage: Gradual reduction in coughing paroxysms spanning several weeks to months ("the 100-day cough").

• Pharyngitis

  • Acute or chronic inflammation of the pharyngeal mucous membranes, clinically manifesting as erythema, odynophagia, tonsillar exudates, and localized pharyngeal pain.

  • Etiology: Largely viral (rhinovirus, coronavirus, Epstein-Barr virus); the primary bacterial cause is group A beta-hemolytic Streptococcus (Streptococcus pyogenes), requiring diagnostic exclusion and antibiotic management to prevent acute rheumatic fever and glomerulonephritis.

• Pleural effusion

  • Pathological accumulation of excess fluid within the potential space of the pleural cavity between the visceral and parietal pleurae.

  • Classification via Light criteria (fluid is exudative if it meets at least one parameter):

  • Pleural fluid protein divided by serum protein $>0.5$

  • Pleural fluid lactate dehydrogenase (LDH) divided by serum LDH $>0.6$

  • Pleural fluid LDH $>\frac{2}{3}$ the upper limit of normal serum LDH

  • Transudates result from systemic imbalances in hydrostatic or oncotic pressure (e.g., congestive heart failure, cirrhosis, nephrotic syndrome); exudates result from local inflammation, infection, or malignancy altering capillary permeability.

• Pleurisy

  • Inflammation of the parietal and visceral pleural linings (pleuritis).

  • Clinical manifestation: Characterized by sharp, localized, lancinating pleuritic chest pain that exacerbates during inspiration, coughing, or sudden movements; auscultation often reveals a superficial, scratching pleural friction rub.

• Pleurodynia

  • Severe paroxysmal pain affecting the intercostal muscles and pleura.

  • Classic clinical presentation occurs in epidemic pleurodynia (Bornholm disease), an acute infectious illness caused by Group B Coxsackieviruses, characterized by sudden-onset, severe, spasmodic pain across the lower thorax and upper abdomen accompanied by fever.

• Pneumoconiosis

  • A non-neoplastic, chronic fibrotic reaction of the lung parenchyma triggered by the inhalation, accumulation, and biological retention of inorganic, mineral, or metallic dust particles.

  • Representative forms include silicosis (crystalline silica), asbestosis (asbestos fibers), and coal workers' pneumoconiosis (anthracosis/coal dust), which provoke macrophage recruitment, sustained inflammation, and widespread progressive pulmonary fibrosis.

• Pneumonectomy

  • Surgical intervention involving the total operative excision and removal of an entire lung.

  • Primary indications include central, locally invasive non-small cell lung carcinoma, extensive unilateral destruction from refractory tuberculosis or bronchiectasis, and severe pulmonary trauma.

• Pneumonia

  • Acute infectious consolidation and inflammatory process of the pulmonary parenchyma involving terminal bronchioles and alveolar spaces.

  • Pathological evolution classically demonstrates alveolar exudation with edema, red hepatization (erythrocyte and neutrophilic extravasation), gray hepatization (fibrin deposition and leukocyte disintegration), and resolution.

  • Manifestations include productive cough, purulent sputum, fever, chills, dyspnea, and dullness to percussion, with crackles and bronchophony on auscultation.

• Pneumothorax

  • Presence of free air or gas inside the pleural space between the visceral and parietal pleurae, which disrupts negative intrapleural pressure and causes partial or complete lung collapse.

  • Classifications:

  • Spontaneous: Primary (absence of overt underlying lung disease, often in tall, thin young individuals with apical subpleural blebs) or secondary (complication of underlying COPD, tuberculosis, cystic fibrosis).

  • Traumatic: Resulting from penetrating or blunt thoracic wall injuries.

  • Tension pneumothorax: Life-threatening one-way valve air entry leading to progressive intrapleural pressurization, mediastinal shift toward the contralateral side, compression of the great veins, and hemodynamic collapse.

• Polysomnography

  • Comprehensive multi-channel diagnostic sleep study monitoring physiological parameters during nocturnal sleep.

  • Measured parameters: Electroencephalography (EEG) for sleep staging, electrooculography (EOG) for rapid eye movements, electromyography (EMG) for submental/limb muscle tone, electrocardiography (ECG), continuous nasal-oral airflow, chest and abdominal respiratory effort bands, and pulse oximetry.

• Pulmonary edema

  • Pathological extravasation and accumulation of fluid in the interstitial spaces and alveolar air sacs of the lungs, impairing alveolar gas diffusion.

  • Etiological classes:

  • Cardiogenic (hydrostatic) edema: Caused by elevated pulmonary capillary wedge pressure ($PCWP > 18\,\text{mmHg}$) secondary to left ventricular systolic/diastolic failure, mitral stenosis, or volume overload.

  • Non-cardiogenic (permeability) edema: Caused by direct or indirect pulmonary microvascular endothelial damage and increased capillary permeability, characteristic of Acute Respiratory Distress Syndrome (ARDS).

• Pulmonologist

  • Internal medicine physician specialized in pulmonology, focusing on the diagnosis, management, and treatment of conditions of the respiratory system, pulmonary vasculature, and thoracic cavity.

Diagnostic Instrumentation, Interventions, and Pulmonary Infections

• Pulse oximeter

  • Non-invasive diagnostic device that monitors arterial hemoglobin oxygen saturation ($SpO_2$) and pulse rate via peripheral cutaneous sensors (finger, toe, or earlobe).

  • Mechanism: Operates via spectrophotometry and plethysmography, utilizing differential optical absorption characteristics of oxygenated hemoglobin (absorbs more infrared light at $940\,\text{nm}$) and deoxygenated hemoglobin (absorbs more red light at $660\,\text{nm}$) across arterial pulsations.

• Pyothorax

  • Purulent exudative accumulation of pus inside the pleural space; functionally and pathologically synonymous with thoracic empyema.

  • Etiology: Typically arises from the direct extension of parapneumonic infections, penetrating chest trauma, rupture of a pulmonary abscess, or post-thoracotomy surgical contamination; requires drainage via thoracostomy tube and antimicrobial therapy.

• Sinusitis

  • Inflammation of the mucosal tissue lining the paranasal sinuses (maxillary, frontal, ethmoid, or sphenoid sinuses), frequently occurring concurrently with rhinitis (rhinosinusitis).

  • Clinical features: Facial pressure, localized dental or sinus pain, nasal congestion, purulent rhinorrhea, and hyposmia; commonly initiated by viral upper respiratory tract pathogens and secondarily complicated by bacterial pathogens like Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.

• Sleep apnea

  • Chronic nocturnal respiratory sleep disorder characterized by repeated pauses, reductions, or interruptions in ventilation during sleep.

  • Variants:

  • Obstructive sleep apnea (OSA): Characterized by recurrent upper airway collapse and obstruction at the pharyngeal level despite persistent, active thoracic and abdominal respiratory efforts; associated with obesity, daytime hypersomnolence, hypertension, and oxygen desaturations.

  • Central sleep apnea (CSA): Characterized by transient cessation of neural output from the medullary respiratory center to respiratory muscles, resulting in absence of both airflow and respiratory effort.

• Spirometer

  • Diagnostic physiological apparatus utilized to measure the volume of air inhaled and exhaled as a function of time during standardized, forced respiratory maneuvers.

  • Core metrics recorded:

  • Forced vital capacity ($FVC$): Total volume of air forcefully exhaled following maximal deep inhalation.

  • Forced expiratory volume in 1 second ($FEV_1$): Volume of air expelled during the first second of maximal forced expiration.

  • Ratio of $FEV_1/FVC$: Used to distinguish obstructive patterns (reduced ratio) from restrictive patterns (preserved or elevated ratio with decreased absolute $FVC$).

• Tachypnea

  • Abnormally rapid resting rate of respiration, conventionally defined in adults as a persistent ventilatory frequency greater than $20\,\text{breaths/min}$.

  • Differentiated from hyperpnea (which indicates deeper breathing that may be rapid or slow) and hyperventilation (which implies ventilation exceeding metabolic needs resulting in reduced $PaCO_2$).

• Thoracentesis

  • Minor surgical procedure involving the percutaneous needle aspiration of fluid (or air) from the pleural cavity.

  • Clinical applications: Diagnostic evaluation to analyze pleural fluid chemistry (proteins, LDH, glucose, pH), cytology, and microbiology, or therapeutic decompression to relieve severe dyspnea caused by massive pleural effusions.

• Thoracotomy

  • Formal surgical incision entering the thoracic wall into the pleural space to achieve direct visualization, exposure, and access to the thoracic organs (lungs, heart, esophagus, thoracic aorta).

  • Standard approaches include posterolateral, anterolateral, or axillary incisions, commonly used for lung resections, trauma exploration, and mediastinal tumor excisions.

• Tracheostomy

  • Surgical or percutaneous creation of a stable, open artificial stoma on the anterior wall of the cervical trachea, through which an indwelling tracheostomy tube is inserted to establish an airway.

  • Clinical applications: Prolonged mechanical ventilation, failure of endotracheal extubation, management of severe chronic upper airway obstructions, and facilitation of airway pulmonary toilet.

• Tracheotomy

  • The operative incision made directly into the anterior cartilaginous wall of the trachea below the cricoid cartilage.

  • Terminology nuance: Represents the incisional surgical step that creates an opening into the trachea, whereas tracheostomy refers to the fashioned opening or stoma itself.

• Tuberculosis

  • Chronic infectious granulomatous disease caused primarily by the acid-fast bacillus Mycobacterium tuberculosis.

  • Pathophysiology: Airborne transmission leads to primary alveolar infection with macrophage ingestion, formation of the Ghon focus and Ghon complex, and development of caseating granulomas with central necrotic cores surrounded by multinucleated Langhans giant cells and lymphocytes.

  • Clinical features: Night sweats, persistent productive cough, hemoptysis, low-grade fevers, anorexia, and progressive cachexia; can remain dormant as latent tuberculosis infection (LTBI) or progress to secondary active pulmonary cavitary disease or disseminated extrapulmonary disease (miliary tuberculosis).