[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › Respiratory # Respiratory Mechanics, volumes, ventilation/perfusion, gas transport and the control of breathing. 34 pages ## Exam priority: high - [**CO₂ transport and the Haldane effect** Mechanism · CO₂ travels in blood mostly as bicarbonate](https://durgical.com/en/physiology/co-transport-and-the-haldane-effect/) - [**Control of breathing, chemoreceptors and lung reflexes** Regulation · The brainstem sets the rhythm of breathing](https://durgical.com/en/physiology/control-of-breathing-chemoreceptors-and-lung-reflexes/) - [**Dead space and alveolar ventilation** Concept · Part of every breath stays in the airway tubes and never reaches the alveoli](https://durgical.com/en/physiology/dead-space-and-alveolar-ventilation/) - [**Lung volumes, capacities and spirometry** Measurement · The lung has four basic volumes; their sums are the capacities](https://durgical.com/en/physiology/lung-volumes-capacities-and-spirometry/) - [**Mechanics of breathing: pressures and muscles** Mechanism · To breathe in, muscles enlarge the chest, pressure inside the lungs drops and air flows in by…](https://durgical.com/en/physiology/mechanics-of-breathing-pressures-and-muscles/) - [**Obstructive and restrictive patterns, and flow–volume loops** Measurement · In obstruction the air comes out slowly; in restriction the lung is small](https://durgical.com/en/physiology/obstructive-and-restrictive-patterns-and-flow-volume-loops/) - [**Oxygen transport and the dissociation curve** Mechanism · Almost all oxygen rides bound to hemoglobin](https://durgical.com/en/physiology/oxygen-transport-and-the-dissociation-curve/) - [**Oxygenation: SpO₂, PaO₂, cyanosis and oxygen therapy** Measurement · A pulse oximeter shows how full of O₂ hemoglobin is; a blood gas measures O₂ pressure](https://durgical.com/en/physiology/oxygenation-spo-pao-cyanosis-and-oxygen-therapy/) - [**The alveolar gas equation and the A–a gradient** Measurement · A formula estimates how much oxygen is in the alveoli](https://durgical.com/en/physiology/the-alveolar-gas-equation-and-the-a-a-gradient/) - [**The causes of hypoxemia** Mechanism · There are only a few ways to end up with too little oxygen in the blood](https://durgical.com/en/physiology/the-causes-of-hypoxemia/) - [**Types of hypoxia and what hypoxia does to the body** Table to know · Hypoxia means cells get too little oxygen](https://durgical.com/en/physiology/types-of-hypoxia-and-what-hypoxia-does-to-the-body/) - [**Ventilation–perfusion matching and West zones** Mechanism · To exchange gas, air and blood must reach the same alveolus](https://durgical.com/en/physiology/ventilation-perfusion-matching-and-west-zones/) ## Exam priority: medium - [**Abnormal breathing patterns and sleep apnea** Regulation · How someone breathes says a lot: cycles that swell and fade, deep breaths from acid, or pauses…](https://durgical.com/en/physiology/abnormal-breathing-patterns-and-sleep-apnea/) - [**Airway resistance** Concept · The narrower a tube, the harder it is to push air through](https://durgical.com/en/physiology/airway-resistance/) - [**Alveolar air: composition, slow renewal and how ventilation sets PAO₂ and PACO₂** Concept · The air deep in the lungs is not fresh air](https://durgical.com/en/physiology/alveolar-air-composition-slow-renewal-and-how-ventilation-sets-pao-and-paco/) - [**Carbon monoxide, methemoglobin and cyanide** Mechanism · Three poisons starve tissues of oxygen even when the lungs work: two spoil hemoglobin and one…](https://durgical.com/en/physiology/carbon-monoxide-methemoglobin-and-cyanide/) - [**Diffusion across the respiratory membrane and DLCO** Mechanism · Oxygen crosses from the air sac into the blood through a very thin wall](https://durgical.com/en/physiology/diffusion-across-the-respiratory-membrane-and-dlco/) - [**Gas laws of breathing: partial pressure, solubility and water vapour** Concept · Each gas in air pushes with its own share of the pressure](https://durgical.com/en/physiology/gas-laws-of-breathing-partial-pressure-solubility-and-water-vapour/) - [**Hypercapnia and dyspnea: what excess CO₂ does and why breathlessness is felt** Mechanism · Too much CO₂ makes the blood acid and, at high levels, sedates the brain](https://durgical.com/en/physiology/hypercapnia-and-dyspnea-what-excess-co-does-and-why-breathlessness-is-felt/) - [**Hypoxemic and hypercapnic respiratory failure** Mechanism · The lungs can fail in two ways: they can't get oxygen into the blood (type 1), or they can't…](https://durgical.com/en/physiology/hypoxemic-and-hypercapnic-respiratory-failure/) - [**Lung and chest wall compliance** Concept · Compliance is how much the lung inflates for each unit of pressure](https://durgical.com/en/physiology/lung-and-chest-wall-compliance/) - [**Oxygen at the tissue level: interstitial and cellular PO₂** Mechanism · Oxygen steps down from blood to tissue fluid to cells](https://durgical.com/en/physiology/oxygen-at-the-tissue-level-interstitial-and-cellular-po/) - [**Oxygen content, delivery and extraction** Measurement · Tissues care not just about saturation but about how much oxygen the blood carries and how much…](https://durgical.com/en/physiology/oxygen-content-delivery-and-extraction/) - [**Physiology of positive-pressure ventilation** Mechanism · A ventilator pushes air in with positive pressure](https://durgical.com/en/physiology/physiology-of-positive-pressure-ventilation/) - [**Physiology of pulmonary edema** Mechanism · When lung capillaries leak more fluid than the lymphatics can drain, the air sacs flood and…](https://durgical.com/en/physiology/physiology-of-pulmonary-edema/) - [**Pleural fluid: formation and drainage** Mechanism · A tiny layer of fluid between lung and chest wall lets them glide](https://durgical.com/en/physiology/pleural-fluid-formation-and-drainage/) - [**Surface tension, surfactant and Laplace's law** Concept · A thin film of fluid lines the air sacs and pulls them shut](https://durgical.com/en/physiology/surface-tension-surfactant-and-laplace-s-law/) - [**The pulmonary circulation and hypoxic vasoconstriction** Regulation · The right heart pumps all the blood through the lungs at low pressure](https://durgical.com/en/physiology/the-pulmonary-circulation-and-hypoxic-vasoconstriction/) - [**The work of breathing** Concept · Breathing costs energy: the lung must be stretched and airway resistance overcome](https://durgical.com/en/physiology/the-work-of-breathing/) - [**Ventilatory responses to CO₂, pH and O₂ and how the carotid body senses O₂** Measurement · Breathing rises steeply when CO₂ goes up, less with acid and only late when O₂ falls](https://durgical.com/en/physiology/ventilatory-responses-to-co-ph-and-o-and-how-the-carotid-body-senses-o/) ## For completeness - [**Airway defenses, cough and mucociliary clearance** Concept · The nose filters, mucus traps, cilia sweep upward and cough throws it out: that is how the lung…](https://durgical.com/en/physiology/airway-defenses-cough-and-mucociliary-clearance/) - [**How voice is produced: phonation, articulation and resonance** Mechanism · Air from the lungs makes the vocal folds vibrate; the throat, mouth and nose shape that buzz…](https://durgical.com/en/physiology/how-voice-is-produced-phonation-articulation-and-resonance/) - [**The bronchial circulation** Concept · The lung has two blood supplies: the pulmonary one to oxygenate blood, and the bronchial one…](https://durgical.com/en/physiology/the-bronchial-circulation/) - [**The CO₂ dissociation curve and the respiratory exchange ratio** Concept · Blood carries CO₂ almost in proportion to its pressure](https://durgical.com/en/physiology/the-co-dissociation-curve-and-the-respiratory-exchange-ratio/) ## A to Z - [A](https://durgical.com/en/physiology/a-z/a/) - [B](https://durgical.com/en/physiology/a-z/b/) - [C](https://durgical.com/en/physiology/a-z/c/) - [D](https://durgical.com/en/physiology/a-z/d/) - [E](https://durgical.com/en/physiology/a-z/e/) - [F](https://durgical.com/en/physiology/a-z/f/) - [G](https://durgical.com/en/physiology/a-z/g/) - [H](https://durgical.com/en/physiology/a-z/h/) - [I](https://durgical.com/en/physiology/a-z/i/) - [L](https://durgical.com/en/physiology/a-z/l/) - [M](https://durgical.com/en/physiology/a-z/m/) - [N](https://durgical.com/en/physiology/a-z/n/) - [O](https://durgical.com/en/physiology/a-z/o/) - [P](https://durgical.com/en/physiology/a-z/p/) - [R](https://durgical.com/en/physiology/a-z/r/) - [S](https://durgical.com/en/physiology/a-z/s/) - [T](https://durgical.com/en/physiology/a-z/t/) - [U](https://durgical.com/en/physiology/a-z/u/) - [V](https://durgical.com/en/physiology/a-z/v/) - [W](https://durgical.com/en/physiology/a-z/w/) [← Physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given. Representative model, for educational purposes only. --- Source: https://durgical.com/en/physiology/areas/resp/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/areas/resp/