46 articles
Pulmonary Diffusing Capacity
Pulmonary diffusing capacity (DLCO, TLCO) measures carbon monoxide transfer from alveoli to blood, reflecting membrane area, capillary blood volume, and hemoglobin; developed by Marie Krogh in 1915 and standardized by Ogilvie in 1957.
Pulmonary surfactant
Pulmonary surfactant (lung surfactant) is a lipid-protein mixture secreted by type II alveolar cells that lowers alveolar surface tension to near 0 mN/m, preventing collapse; deficiency causes neonatal RDS, treated with animal-derived or synthetic surfactant replacement.
Residual Volume
Residual volume (RV) is the gas remaining in the lungs after maximal exhalation; measured indirectly as FRC minus ERV or TLC minus vital capacity, it prevents alveolar collapse and rises in obstructive air trapping.
Respiration (physiology)
Respiration (physiology): gas exchange supplying oxygen and removing carbon dioxide, covering pulmonary versus cellular respiration, diffusion, ventilation–perfusion matching, Bohr and Haldane effects, breathing control, and responses to exercise and altitude.
Respiratory rate
Respiratory rate (RR), breathing rate, breaths per minute: a core vital sign, normal 12–20 in adults, scored in NEWS2; manual counting is error-prone, capnography is the gold standard.
Respiratory system
Respiratory system: the organ system exchanging oxygen and carbon dioxide across the alveolar blood-gas barrier via ventilation and perfusion. Key facts: V/Q matching governs efficiency; COPD caused 3.4 million deaths in 2023.
Respiratory tract
Respiratory tract: the airways carrying air from nose and mouth to the alveoli. Divided into upper (nose, sinuses, pharynx, larynx) and lower (trachea, bronchi, lungs) tracts, with conducting and gas-exchange zones.
Sinus (anatomy)
In anatomy, a sinus is an air-filled cavity within a bone or tissue, most often one of the four paired paranasal sinuses around the nose, which all drain into it.
Thoracic diaphragm
Thoracic diaphragm: the dome-shaped musculofibrous partition between chest and abdomen, the primary mammalian inspiratory muscle, with T8, T10, and T12 openings and sternal, costal, and crural regions.
Tidal volume
Tidal volume (VT, TV) is the air moved in one normal breath, about 500 mL or 7 mL/kg ideal body weight in adults; a static lung volume in spirometry and, in ARDS ventilation, limited to 4–8 mL/kg predicted body weight.
Total Lung Capacity
Total lung capacity (TLC) is the lung gas volume at maximal inspiration, about 6 liters in healthy adults. Measured by plethysmography, gas dilution, or CT; reduced TLC defines restriction, elevated TLC indicates hyperinflation in COPD.
Trachea
Trachea (windpipe): midline cartilage-ringed airway from larynx to carina; 10-13 cm in adults, 16-20 C-shaped rings, trachealis muscle posteriorly, four wall layers, mucociliary clearance.
Ventilation/perfusion ratio
Ventilation/perfusion (V/Q) ratio: ratio of alveolar ventilation to pulmonary blood flow, about 0.8 overall, lower at lung bases; V/Q mismatch underlies hypoxemia, shunt, dead space, and the V/Q scan used to diagnose pulmonary embolism and CTEPH.
Vital Capacity
Vital capacity (VC), including forced (FVC), slow (SVC), and inspiratory (IVC) variants, is the maximum air exhaled after a maximal inspiration, defined by John Hutchinson in 1846 and central to spirometric diagnosis of restrictive and obstructive lung disease.
Vocal cords
Vocal cords, commonly known as vocal folds, are muscularized tissue in the larynx. They vibrate with lung air to produce sound and protect the airway during swallowing.
Work of Breathing
Work of breathing (WOB, Wb): mechanical work respiratory muscles expend to overcome elastic and resistive loads, measured via esophageal pressure–volume loops (Campbell diagram); resting values 2.4–4 J/min; method-dependent.