Pulmonary compliance

Pulmonary compliance

Pulmonary compliance (or lung compliance) can refer to either dynamic or static lung compliance. Static lung compliance is the change in volume for any given applied pressure.[1] Dynamic lung compliance is the compliance of the lung at any given time during actual movement of air.

The compliance of the lungs demonstrate hysteresis, that is the compliance is different on inspiration and expiration for identical volumes. See Hysteresis#Respiratory_physiology.

Compliance is greatest at moderate lung volumes, and much lower at volumes which are very low or very high.



Static compliance is calculated using the following equation, where ΔV is the change in volume, and ΔP is the change in pleural pressure:

C =  \frac{ \Delta V}{ \Delta P}

For example if a patient inhales 500 mL of air from a spirometer and intrapleural pressure before inspiration is – 5 cm H2O and -10 cm H2O at the end of inspiration. Then:
 Compliance = \frac{\Delta V}{\Delta P} = \frac{.5\;L}{(-5\;cmH_2O - (-10\;cmH_2O))} = \frac{.5\;L}{5\;cmH_2O} = 0.1\;L\;\times\;cmH_2O^{-1}

Dynamic lung compliance is ≤ static lung compliance. Dynamic lung compliance is calculated using the following equation, where CD = Dynamic compliance; VT = tidal volume; PIP = Peak inspiratory pressure; PEEP = Positive End Expiratory Pressure):

CD = \frac{ VT}{ PIP-PEEP}

Dynamic Compliance (Cdyn)

C_{dyn} = \frac{{V_T}}{{P_{IP}-P_{EEP}}}

Cdyn — VT / (PIP - P_{EEP}), where PIP = peak inspiratory pressure (the maximum pressure during inspiration). Alterations in airway resistance, lung compliance and chest wall compliance influence Cdyn.

Static Compliance (Cstat)

C_{stat} = \frac{{V_T}}{{P_{plat}-P_{EEP}}}

Cstat — Vt / (Pplat - PEEP), where Pplat = plateau pressure. Pplat is measured at the end of inhalation and prior to exhalation using an inspiratory hold maneuver. During this maneuver, airflow is transiently (~0.5 sec) discontinued, which eliminates the effects of airway resistance. Pplat is never > PIP and is typically < 3-5 cmH2O lower than PIP when airway resistance is not elevated.

Clinical significance

It is an important measurement in respiratory physiology.[2][3][4]

  • fibrosis is associated with a decrease in pulmonary compliance.
  • emphysema/COPD may be associated with an increase in pulmonary compliance due to the loss of alveolar and elastic tissue.

Pulmonary surfactant increases compliance by decreasing the surface tension of water. The internal surface of the alveolus is covered with a thin coat of fluid. The water in this fluid has a high surface tension, and provides a force that could collapse the alveolus. The presence of surfactant in this fluid breaks up the surface tension of water, making it less likely that the alveolus can collapse inward. If the alveolus were to collapse, a great force would be required to open it, meaning that compliance would decrease drastically.

Functional significance of abnormally high or low compliance

Low compliance indicates a stiff lung and means extra work is required to bring in a normal volume of air. This occurs as the lungs in this case become fibrotic, lose their distensibility and become stiffer.

In a highly compliant lung, as in emphysema, the elastic tissue has been damaged, usually due to their being overstretched by chronic overinflation. Patients with emphysema have a very high lung compliance due to the poor elastic recoil, they have no problem inflating the lungs but have extreme difficulty exhaling air. In this condition extra work is required to get air out of the lungs.

Compliance decreases in the following cases:


  1. ^ MeSH Lung+compliance
  2. ^ Compliance
  3. ^ Nikischin W, Gerhardt T, Everett R, Bancalari E (1998). "A new method to analyze lung compliance when pressure-volume relationship is nonlinear.". Am J Respir Crit Care Med 158 (4): 1052–60. PMID 9769260.  article
  4. ^ Physiology at MCG 4/4ch2/s4ch2_21

Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • Pulmonary surfactant — Diagram of the alveoli with both cross section and external view Pulmonary surfactant is a surface active lipoprotein complex (phospholipoprotein) formed by type II alveolar cells. The proteins and lipids that surfactant comprises have both a… …   Wikipedia

  • Compliance (physiology) — This article is about the physiological term. For other uses, see Compliance (disambiguation). Compliance is a measure of the tendency of a hollow organ to resist recoil toward its original dimensions upon removal of a distending or compressing… …   Wikipedia

  • compliance — 1. A measure of the distensibility of a chamber expressed as a change in volume per unit change in pressure. 2. The consistency and accuracy with which a patient follows the regimen prescribed by a …   Medical dictionary

  • Pulmonary contusion — Classification and external resources A CT scan showing a pulmonary contusion (red arrow) accompanied by a rib fracture (blue arrow) ICD 10 S …   Wikipedia

  • Pulmonary artery pressure — (PA pressure) is a measure of the blood pressure found in the pulmonary artery. Mean pulmonary arterial pressure is normally 9 18 mmHg.[1] Site Normal pressure range (in mmHg)[2] Central venous pressure 3–8 Right ventricular pressure systolic …   Wikipedia

  • Pulmonary wedge pressure — Diagram of Pulmonary artery catheter The pulmonary capillary wedge pressure or PCWP (also called the pulmonary wedge pressure or PWP, or pulmonary artery occlusion pressure or PAOP) is the pressure measured by wedging a pulmonary catheter with an …   Wikipedia

  • Pulmonary capillary wedge pressure — The Pulmonary capillary wedge pressure (abbreviated PCWP), as measured by a Swan Ganz catheter, is the pressure measured in a pulmonary artery after occlusion of that artery. Because of the large compliance of the pulmonary circulation, it… …   Wikipedia

  • Idiopathic pulmonary fibrosis — Classification and external resources Extensive lung fibrosis from usual interstitial pneumonitis ICD 10 J …   Wikipedia

  • Tracheobronchial injury — Classification and external resources Reconstruction of the trachea and bronchi with x ray computed tomography showing disruption of the right main bronchus with abnormal lucency (arrow) …   Wikipedia

  • Modes of mechanical ventilation — Contents 1 Positive and negative pressure ventilation 1.1 Negative pressure ventilation 1.1.1 Types of negat …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”