Intrapleural pressure

In physiology, intrapleural pressure is the pressure within the pleural cavity. Normally, it is slightly less than the atmospheric pressure,^[1] about −4 mm Hg while neither inspiring or expiring; during normal breathing, it normally cyclically changes ±2 mm Hg, decreasing with inspiration and increasing with expiration. During strenuous breathing however, it may change by as much as ±50 mm Hg.^[2] ITP depends on the ventilation phase, atmospheric pressure, and the volume of the intrapleural cavity.^[3]

ITP is normally always slightly negative to prevent lungs from collapsing, and is maintained by the tendency of the lungs and chest to recoil away from each other. When air is sucked into the pleural cavity, the negative ITP is lost, a condition known as pneumothorax.

Physiology

Determinants

Physiological:

Müller's maneuver (forced inspiration against a closed glottis results in negative pressure) can temporarily but significantly decrease the intrapleural pressure.^[1]
Deep inspiration

Pathological:

Emphysema
Pneumothorax Condition

Cardiovascular effects

Cardiac filling depends upon the pressure outside the heart. The cyclical changes in ITP during inspiration and expiration promote or hamper cardiac filling, respectively.^[2]

References

^ ^a ^b Khanorkar, p. 205
^ ^a ^b Hall, John E.; Hall, Michael E. (2021). "Chapter 55 - Spinal Cord Motor Functions; the Cord Reflexes". Guyton and Hall Textbook of Medical Physiology (14th ed.). Philadelphia, PA: Elsevier. p. 250. ISBN 978-0-323-59712-8.
^ Blom, p. 7

Books

Blom, J. A. (2004). Monitoring of Respiration and Circulation. CRC Press. ISBN 978-0-8493-2083-5.
Khanorkar, Sudha Vinayak (1 February 2012). Insights in Physiology. JP Medical Ltd. ISBN 978-93-5025-516-2.

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[Khanorkar_p205-1] Khanorkar, p. 205

[:022-2] Hall, John E.; Hall, Michael E. (2021). "Chapter 55 - Spinal Cord Motor Functions; the Cord Reflexes". Guyton and Hall Textbook of Medical Physiology (14th ed.). Philadelphia, PA: Elsevier. p. 250. ISBN 978-0-323-59712-8.

[3] Blom, p. 7

[1]

[2]

[3]

v t e Respiratory physiology
Respiration	breath inhalation exhalation obligate nasal breathing 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 receptor 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	ventilation (V) Perfusion (Q) Ventilation/perfusion ratio V/Q scan zones of the lung gas exchange pulmonary gas pressures alveolar gas equation alveolar–arterial gradient hemoglobin oxygen–hemoglobin 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 death zone oxygen toxicity hypoxia