Computed tomography in adult respiratory distress syndrome: what has it taught us?

Computed tomography (CT) has played an important role in improving our knowledge of the pathophysiology of the adult respiratory distress syndrome (ARDS), and in determining the morphological and functional relationships of different manoeuvres commonly used in the therapeutic management of this syndrome (changes in body position, application of positive end-expiratory pressure (PEEP) and mechanical ventilation). During the early phase of the disease, the ARDS lung is characterized by a homogenous alteration of the vascular permeability. Thus, oedema accumulates evenly in all lung regions with a nongravitational distribution (homogenous lung). The increased lung weight, due to increased oedema, causes a collapse of the lung regions along the vertical axis, through the transmission of hydrostatic forces (compression atelectasis). Thus, the lesions appear mainly in the dependent lung regions (dishomogeneous lung). During inspiration, at plateau pressure, the pulmonary units reopen and, if the PEEP applied is adequate, they stay open during the following expiration. Adequate PEEP is equal to or higher than the hydrostatic forces compressing that unit. Prone position is another manoeuvre which allows previously collapsed lung regions to reopen and, conversely, compresses previously aerated regions, reversing the distribution of gravitational forces. During late ARDS, there is less compression atelectasis and the lung undergoes structural changes, due to the reduced amount of oedema. This is usually associated with CO2 retention and the development of emphysema-like lesions. In conclusion, computed tomography is not only a research tool, but a useful technique which allows a better understanding of the progressive change in strategy needed to ventilate the adult respiratory distress syndrome lung at different stages of the disease.

This article has been cited by other articles:

				I. Galvin, G. B. Drummond, and M. Nirmalan Distribution of blood flow and ventilation in the lung: gravity is not the only factor Br. J. Anaesth., April 1, 2007; 98(4): 420 - 428. [Abstract] [Full Text] [PDF]

				S. D. Mentzelopoulos, C. Roussos, and S. G. Zakynthinos Prone position reduces lung stress and strain in severe acute respiratory distress syndrome Eur. Respir. J., March 1, 2005; 25(3): 534 - 544. [Abstract] [Full Text] [PDF]

				C. Rylander, M. Hogman, G. Perchiazzi, A. Magnusson, and G. Hedenstierna Functional Residual Capacity and Respiratory Mechanics as Indicators of Aeration and Collapse in Experimental Lung Injury Anesth. Analg., March 1, 2004; 98(3): 782 - 789. [Abstract] [Full Text] [PDF]

				L. Magnusson and D. R. Spahn New concepts of atelectasis during general anaesthesia Br. J. Anaesth., July 1, 2003; 91(1): 61 - 72. [Full Text] [PDF]

				M. Prella, F. Feihl, and G. Domenighetti Effects of Short-term Pressure-Controlled Ventilation on Gas Exchange, Airway Pressures, and Gas Distribution in Patients With Acute Lung Injury/ARDS: Comparison With Volume-Controlled Ventilation Chest, October 1, 2002; 122(4): 1382 - 1388. [Abstract] [Full Text] [PDF]

				S. Afifi Lung Protective Ventilation Strategies Seminars in Cardiothoracic and Vascular Anesthesia, September 1, 2002; 6(3): 259 - 269. [Abstract] [PDF]

				T. A. Murray and L. A. Patterson Prone Positioning of Trauma Patients With Acute Respiratory Distress Syndrome and Open Abdominal Incisions Crit. Care Nurse, June 1, 2002; 22(3): 52 - 56. [Full Text] [PDF]

				E. Kondili, G. Prinianakis, H. Athanasakis, and D. Georgopoulos Lung emptying in patients with acute respiratory distress syndrome: effects of positive end-expiratory pressure Eur. Respir. J., May 1, 2002; 19(5): 811 - 819. [Abstract] [Full Text] [PDF]

				J Dakin and M Griffiths The pulmonary physician in critical care 1: Pulmonary investigations for acute respiratory failure Thorax, January 1, 2002; 57(1): 79 - 85. [Abstract] [Full Text] [PDF]

				A. S. Slutsky The Acute Respiratory Distress Syndrome, Mechanical Ventilation, and the Prone Position N. Engl. J. Med., August 23, 2001; 345(8): 610 - 612. [Full Text] [PDF]

				H.-D. HELD, S. BOETTCHER, L. HAMANN, and S. UHLIG Ventilation-Induced Chemokine and Cytokine Release Is Associated with Activation of Nuclear Factor-{kappa}B and Is Blocked by Steroids Am. J. Respir. Crit. Care Med., March 1, 2001; 163(3): 711 - 716. [Abstract] [Full Text] [PDF]

				S. R. Desai, A. U. Wells, G. Suntharalingam, M. B. Rubens, T. W. Evans, and D. M. Hansell Acute Respiratory Distress Syndrome Caused by Pulmonary and Extrapulmonary Injury: A Comparative CT Study Radiology, March 1, 2001; 218(3): 689 - 693. [Abstract] [Full Text]

				J DAKIN and T W EVANS Progress in ARDS research: a protection racket? Thorax, January 1, 2001; 56(1): 2 - 3. [Full Text]

				K. E. Thomas, C. M. Owens, J. Britto, S. Nadel, P. Habibi, and R. Nicholson Efficacy of Chest CT in a Pediatric ICU : A Prospective Study Chest, June 1, 2000; 117(6): 1697 - 1705. [Abstract] [Full Text] [PDF]

				P. NEUMANN, J. E. BERGLUND, L. G. ANDERSSON, E. MARIPU, A. MAGNUSSON, and G. HEDENSTIERNA Effects of Inverse Ratio Ventilation and Positive End-Expiratory Pressure in Oleic Acid-Induced Lung Injury Am. J. Respir. Crit. Care Med., May 1, 2000; 161(5): 1537 - 1545. [Abstract] [Full Text]

				P. W. A. Kunst, A. V. Noordegraaf, E. Raaijmakers, J. Bakker, A. B. J. Groeneveld, P. E. Postmus, and P. M. J. M. de Vries Electrical Impedance Tomography in the Assessment of Extravascular Lung Water in Noncardiogenic Acute Respiratory Failure* Chest, December 1, 1999; 116(6): 1695 - 1702. [Abstract] [Full Text] [PDF]

				P. W. A. Kunst, P. M. J. M. de Vries, P. E. Postmus, and J. Bakker Evaluation of Electrical Impedance Tomography in the Measurement of PEEP-Induced Changes in Lung Volume Chest, April 1, 1999; 115(4): 1102 - 1106. [Abstract] [Full Text] [PDF]

				A. N. von BETHMANN, F. BRASCH, R. NÜSING, K. VOGT, H. D. VOLK, K.-M. MÜLLER, A. WENDEL, and S. UHLIG Hyperventilation Induces Release of Cytokines from Perfused Mouse Lung Am. J. Respir. Crit. Care Med., January 1, 1997; 157(1): 263 - 272. [Abstract] [Full Text]