Respiratory physiology

A highly diagrammatic illustration of the process of gas exchange in the mammalian lungs, emphasizing the differences between the gas compositions of the ambient air and the alveolar air (light blue) with which the pulmonary capillary blood equilibrates. The blood gas tensions in the pulmonary arterial (blue blood entering the lung on the left) and pulmonary venous blood (red blood leaving the lung on the right, which will circulate throughout the body) are indicated in the diagram. Note that the blood leaving the lungs has the same

P_{{\mathrm{O}}_2}

and

P_{{\mathrm {CO} }_{2}}

values as the alveolar air (light blue). The ventilation of the lungs replaces only about 15% of the functional residual capacity (the 3 liter of air, in light blue, remaining in the lungs after a normal exhalation) per breath. The composition of that air therefore changes very little with each breath. The entire system is regulated by the arterial blood gas homeostat, which keeps the systemic arterial

P_{{\mathrm {CO} }_{2}}

and

P_{{\mathrm{O}}_2}

constant (within very narrow bounds). All the gas tensions are in kPa. To convert to mm Hg, multiply by 7.5.

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

Topics include:

Volumes

Mechanism

Front view of thorax.

Inhalation (breathing in) 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. In contrast, expiration (breathing out) is usually a passive process.

${\begin{aligned}P&=P_{{el}}+P_{{re}}+P_{{in}}\\P&=EV+R{\dot {V}}+I{\ddot {V}}\end{aligned}}$

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

Circulation, ventilation, and perfusion

Pulmonary circulation

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/transport (primarily oxygen and carbon dioxide)

Oxygen-hemoglobin dissociation curve

Control and response

Pons

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)

Disorders

Additional images

References

↑ Compliance

External links

Overview at Johns Hopkins University
Clinical Sciences - Respiratory An iPhone app covering detailed respiratory physiology and anatomy

Respiratory physiology

Respiration	breath inhalation exhalation respiratory rate respirometer pulmonary surfactant compliance elastic recoil hysteresivity airway resistance bronchial hyperresponsiveness constriction dilatation mechanical ventilation

Control	pons pneumotaxic center apneustic center medulla dorsal respiratory group ventral respiratory group chemoreceptors central peripheral pulmonary stretch receptors Hering–Breuer reflex

Lung volumes	VC FRC Vt dead space CC PEF calculations respiratory minute volume FEV1/FVC ratio Lung function tests spirometry body plethysmography peak flow meter nitrogen washout

Circulation	pulmonary circulation hypoxic pulmonary vasoconstriction pulmonary shunt

Interactions	Perfusion (V) ventilation (Q) ventilation/perfusion scan zones of the lung gas exchange pulmonary gas pressures alveolar gas equation alveolar–arterial gradient hemoglobin oxygen–haemoglobin dissociation curve (Oxygen saturation 2,3-BPG Bohr effect Haldane effect) carbonic anhydrase (chloride shift) oxyhemoglobin respiratory quotient arterial blood gas diffusion capacity (DLCO)

Insufficiency	high altitude oxygen toxicity hypoxia

This article is issued from Wikipedia - version of the 9/23/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.