BJA Advance Access published online on March 8, 2007
British Journal of Anaesthesia, doi:10.1093/bja/aem036
Distribution of blood flow and ventilation in the lung: gravity is not the only factor
1 University Department of Anaesthesia and Critical Care Medicine, Manchester Royal Infirmary, Manchester, UK
2 University Department of Anaesthesia, Critical Care and Pain Medicine, Royal Infirmary of Edinburgh, Edinburgh, UK
* Corresponding author: University Department of Anaesthesia and Critical Care Medicine, Manchester Royal Infirmary, Oxford Road, Manchester M13 9PT, UK. E-mail: m.nirmalan{at}manchester.ac.uk
Current textbooks in anaesthesia describe how gravity affects the regional distribution of ventilation and blood flow in the lung, in terms of vertical gradients of pleural pressure and pulmonary vascular pressures. This concept fails to explain some of the clinical features of disturbed lung function. Evidence now suggests that gravity has a less important role in the variation of regional distribution than structural features of the airways and blood vessels. We review more recent studies that used a variety of methods: external radioactive counters, measurements using inhaled and injected particles, and computer tomography scans. These give a higher spatial resolution of regional blood flow and ventilation. The matching between ventilation and blood flow in these small units of lung is considered; the effects of microgravity, increased gravity, and different postures are reviewed, and the application of these findings to conditions such as acute lung injury is discussed. Down to the scale of the acinus, there is considerable heterogeneity in the distribution of both ventilation and blood flow. However, the matching of blood flow with ventilation is well maintained and may result from a common pattern of asymmetric branching of the airways and blood vessels. Disruption of this pattern may explain impaired gas exchange after acute lung injury and explain how the prone position improves gas exchange.
Keywords: fractals; gravity; model, structural; ventilation, perfusion
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  R. Glenny Counterpoint: Gravity is not the major factor determining the distribution of blood flow in the healthy human lung J Appl Physiol, May 1, 2008; 104(5): 1533 - 1535. [Full Text] [PDF]
|
|
|
|
 |
|
 A. Kozian, T. Schilling, F. Freden, E. Maripuu, C. Rocken, C. Strang, T. Hachenberg, and G. Hedenstierna One-lung ventilation induces hyperperfusion and alveolar damage in the ventilated lung: an experimental study Br. J. Anaesth., April 1, 2008; 100(4): 549 - 559. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Edgcombe, K. Carter, and S. Yarrow Anaesthesia in the prone position Br. J. Anaesth., February 1, 2008; 100(2): 165 - 183. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Drummond Variation in time and space: what is the resolution? J. Physiol., September 1, 2007; 583(2): 417 - 417. [Full Text] [PDF]
|
|
|
|
|
|
K. Melarkode, M. Nirmalan, I. Galvin, and G. B. Drummond Distribution of blood flow and ventilation in the lung: gravity is not the only factor Br. J. Anaesth., August 1, 2007; 99(2): 300 - 301. [Full Text] [PDF]
|
|
E-letters:
Read all E-letters
- Distribution of blood flow and ventilation in the lung
- Krishnan Melarkode
- British Journal of Anaesthesia, 11 Apr 2007 [Full text]
- Distribution of blood flow and ventilation in the lung: gravity is not the only factor. Br J Anaesth
- Mahesh Nirmalan, et al.
- British Journal of Anaesthesia, 15 May 2007 [Full text]