Respiratory physiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Respiratory physiology is the branch of human physiology focusing upon respiration.

Topics include:

• lung volumes
• vital capacity
• functional residual capacity
• dead space
• spirometry
• body plethysmography
• peak flow meter

Breathing in, or inhaling, is usually an active movement. The contraction of the diaphragm muscles cause a pressure variation, which is equal to the pressures caused by elastic, resistive and inertial components of the respiratory system.

<math> \begin{align} P &= P_{el} + P_{re} + P_{in} \\ P &= EV + R\dot{V} + I\ddot{V} \end{align} </math>

Where P_el equals the product of elastance E (inverse of compliance) and volume of the system V, P_re equals the product of flow resistance R and time derivate of volume V (which is equivalent to the flow), P_in equals the product of inertance I and second time derivate of V. R and I are sometimes referred to as Rohrer’s constants.

• Anatomy: pleural cavity, thoracic diaphragm, Intercostales externi muscles, Intercostales interni muscles
• inhalation and exhalation
• lung, pulmonary alveolus
• With insufficient pulmonary surfactant, the pulmonary alveoli collapse, causing atelectasis (in infants, infant respiratory distress syndrome)
• the law of Laplace,
• compliance (physiology) – decreased with fibrosis, increased with emphysema^[1]
• Poiseuille’s law
• asthma and COPD
• hysteresivity

• pulmonary circulation
• positive pressure ventilation
• hypoxic vasoconstriction
• ventilation (physiology), perfusion, ventilation/perfusion ratio (V/Q), and ventilation/perfusion scan
• shunts: right-to-left (tetralogy of fallot), left-to-right (patent ductus arteriosus)
• respiratory rate and respirometer

• gas exchange
• Dalton’s law
• hemoglobin
• oxygen-haemoglobin dissociation curve, Bohr effect, Haldane effect
• carbonic anhydrase
• oxyhemoglobin
• respiratory quotient
• arterial blood gas

• control of respiration
• reticular formation
• pons (apneuistic and pneumotaxic)
• chemoreceptors (medulla, carotid body, aortic body)
• Hering-Breuer reflex
• involuntary control of respiration
• exercise
• hyperoxia
• hypoxemia (hypoxic hypoxia)

• altitude sickness
• asthma
• carbon monoxide poisoning
• COPD
• emphysema
• infant respiratory distress syndrome
• pulmonary edema

• breath sounds
• pulmonology
• respiratory system
• Medical Subject Headings

• Overview at Johns Hopkins University
• Overview at Medical College of Georgia

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