Correspondence

Lung Recruitment in Patients with ARDS

N Engl J Med 2006; 355:319-322July 20, 2006

Article

To the Editor:

In the April 27 issue, Gattinoni et al.1 suggest that the potential for lung recruitment in patients with acute lung injury is generally low and extremely variable among patients. We believe that a suboptimal recruitment maneuver explains such results, contradicting investigations2-4 that demonstrate a much larger potential for recruitment and greater homogeneity of response. Gattinoni et al. used an inspiratory plateau pressure of 45 cm of water, a pressure certainly below the critical opening pressures reported in recent studies2-4 in humans. The investigators also allowed expiratory pressures to repeatedly fall to 5 cm of water, a pressure certainly below the closing pressures of most lung units.5 This procedure is likely to have cyclically forced the energy provided by the next pulse of inspiratory pressure to be wasted in the opening of the recollapsed units, instead of promoting the recruitment of units. The application of the same inspiratory pressures but a higher expiratory pressure (e.g., 20 to 25 cm of water) could greatly enhance the efficacy of the maneuver (Figure 1Figure 1Computed Tomographic Images Obtained at the End-Expiratory Pause in a Patient with Pneumocystosis and the Acute Respiratory Distress Syndrome.), thus affecting the main conclusion.

João B. Borges, M.D.
Carlos R.R. Carvalho, M.D.
Marcelo B.P. Amato, M.D.
University of São Paulo, 01246-903 São Paulo, Brazil

5 References

1. 1

   Gattinoni L, Caironi P, Cressoni M, et al. Lung recruitment in patients with the acute respiratory distress syndrome. N Engl J Med 2006;354:1775-1786
   Full Text | Web of Science | Medline

2. 2

   Schreiter D, Reske A, Stichert B, et al. Alveolar recruitment in combination with sufficient positive end-expiratory pressure increases oxygenation and lung aeration in patients with severe chest trauma. Crit Care Med 2004;32:968-975
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3. 3

   Borges JB, Okamoto VN, Matos GF, et al. Reversibility of lung collapse and hypoxemia in early acute respiratory distress syndrome. Am J Respir Crit Care Med (in press).
   

4. 4

   Medoff BD, Harris RS, Kesselman H, Venegas J, Amato MB, Hess D. Use of recruitment maneuvers and high-positive end-expiratory pressure in a patient with acute respiratory distress syndrome. Crit Care Med 2000;28:1210-1216
   CrossRef | Web of Science | Medline

5. 5

   Gattinoni L, Pelosi P, Crotti S, Valenza F. Effects of positive end-expiratory pressure on regional distribution of tidal volume and recruitment in adult respiratory distress syndrome. Am J Respir Crit Care Med 1995;151:1807-1814
   Web of Science | Medline

To the Editor:

We were surprised by the level of lung recruitment observed by Gattinoni et al. We would have expected a higher percentage of recruitable lung, on the basis of the known response to recruitment maneuvers.1-3 One explanation for this lack of response may have been the length of time for which patients received ventilation (5±6 days) before being studied. A large percentage of patients must have received ventilation for more than one week and some for more than two weeks. Grasso et al.1 demonstrated virtually no lung recruitment in patients who received ventilation for an average of 7±1 days, as compared with a significant response in patients who received ventilation for only 1±0.3 day at the time of lung recruitment. Most recommend that lung recruitment be performed as early as is feasible in the course of the acute respiratory distress syndrome.1-3

Robert M. Kacmarek, Ph.D., R.R.T.
Massachusetts General Hospital, Boston, MA 02114
rkacmarek@partners.org

Jesus Villar, M.D., Ph.D.
Instituto Canario de Investigaçion Biomedica, 35003 Canary Islands, Spain

3 References

1. 1

   Grasso S, Mascia L, Del Turco M, et al. Effects of recruiting maneuvers in patients with acute respiratory distress syndrome ventilated with protective ventilatory strategy. Anesthesiology 2002;96:795-802
   CrossRef | Web of Science | Medline

2. 2

   Ferguson ND, Chiche JD, Kacmarek RM, et al. Combining high-frequency oscillatory ventilation and recruitment maneuvers in adults with early acute respiratory distress syndrome: the Treatment with Oscillation and an Open Lung Strategy (TOOLS) Trial pilot study. Crit Care Med 2005;33:479-486
   CrossRef | Web of Science | Medline

3. 3

   Lachmann B. Open up the lung and keep the lung open. Intensive Care Med 1992;18:319-321
   CrossRef | Web of Science | Medline

To the Editor:

In the Supplementary Appendix of the article by Gattinoni et al., I believe the formula provided to determine the alveolar dead-space fraction was not correct. The value of this variable was automatically computed by a CO₂SMO monitor (Novametrix). This monitor calculates the areas generated by the partial pressure of carbon dioxide curve against the expired volume curve to determine the alveolar dead-space fraction.1 The monitor therefore does not use the formula stated.

Barry Dixon, M.D., Ph.D.
St. Vincent's Hospital, Melbourne 3065, Australia
barry.dixon@svhm.org.au

1 References

1. 1

   Riou Y, Leclerc F, Neve V, et al. Reproducibility of the respiratory dead space measurements in mechanically ventilated children using the CO2SMO monitor. Intensive Care Med 2004;30:1461-1467
   CrossRef | Web of Science | Medline

To the Editor:

The article by Gattinoni et al. replicates, in principle, previously published data1-3 and conclusions.4 Patients with a higher or lower “percentage of potentially recruitable lung” are, in fact, patients with a diffuse or focal loss of aeration, involving predominantly the lower lobes.1-3 As previously demonstrated, as compared with patients with a lower percentage of potentially recruitable lung, patients with a higher percentage of potentially recruitable lung (diffuse loss of aeration) have a lower ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen, lower respiratory compliance, and a higher mortality rate and rate of direct lung injury and can be identified on the basis of an initial bedside chest radiograph that shows bilateral and diffuse infiltrates.2

The expression of lung overinflation as a percentage of hyperinflated lung tissue conceals the fact that many patients had regions of severely overdistended lung during the study. For example, if 10 percent of lung tissue is hyperinflated and lung tissue weighs 1500 g, the overinflated lung volume exceeds 1300 ml. This critical issue is not discussed by Gattinoni et al.; they overlook the fact that our group demonstrated that patients with focal loss of aeration who receive ventilation with a PEEP of 10 cm of water or more are at risk for lung overdistention.4 The authors should provide the overall volume of overinflated lung (in milliliters) identified on computed tomography (CT) in each patient at a pressure of 45 cm of water.

Jean-Jacques Rouby, M.D., Ph.D.
Louis Puybasset, M.D., Ph.D.
Qin Lu, M.D., Ph.D.
Pitié–Salpêtrière Hospital, 75013 Paris, France
jjrouby.pitie@invivo.edu

4 References

1. 1

   Puybasset L, Cluzel P, Gusman P, Grenier P, Preteux F, Rouby JJ. Regional distribution of gas and tissue in acute respiratory distress syndrome. I. Consequences for lung morphology. Intensive Care Med 2000;26:857-869
   CrossRef | Web of Science | Medline

2. 2

   Rouby JJ, Puybasset L, Cluzel P, Richecoeur J, Lu Q, Grenier P. Regional distribution of gas and tissue in acute respiratory distress syndrome. II. Physiological correlations and definition of an ARDS Severity Score. Intensive Care Med 2000;26:1046-1056
   CrossRef | Web of Science | Medline

3. 3

   Puybasset L, Gusman P, Muller JC, Cluzel P, Coriat P, Rouby JJ. Regional distribution of gas and tissue in acute respiratory distress syndrome. III. Consequences for the effects of positive end-expiratory pressure. Intensive Care Med 2000;26:1215-1227
   CrossRef | Web of Science | Medline

4. 4

   Rouby JJ, Lu Q, Goldstein I. Selecting the right level of positive end-expiratory pressure in patients with acute respiratory distress syndrome. Am J Respir Crit Care Med 2002;165:1182-1186
   Web of Science | Medline

Author/Editor Response

Dr. Borges and colleagues illustrate that plateau pressures of up to 60 cm of water associated with a PEEP of 25 cm of water could be used to increase lung recruitment. However, data from the most recent study by Borges et al.1 clearly indicate that the level of recruitment between plateau pressures of 45 and 60 cm of water is negligible, accounting for no more than 2 to 3 percent of nonaerated tissue. The price paid to obtain this result, which is of questionable clinical importance,2 is the retention of carbon dioxide (partial pressure of arterial carbon dioxide, 95±34 mm Hg), severe acidosis (pH, 6.94±0.11), and most important, the need for the infusion of a remarkably large volume to sustain hemodynamic function, right before the recruitment maneuver. We wonder whether the unusually homogeneous and large densities observed at a PEEP of 5 cm of water in Figure 1A of their letter (given that severe pneumocystosis is usually characterized by interstitial infiltrates and low levels of recruitment3) reflects increased edema owing to the sudden overload of fluid (up to 2 liters of colloids1) in inflamed, leaking lung parenchyma, as observed after a few minutes in experiments in animals.4 We believe that the risks associated with the use of pressures of 60 and 25 cm of water — possible barotrauma and volume overload5 — largely outweigh the modest increment in the level of potentially recruitable lung.

Drs. Kacmarek and Villar wonder about the recruitment–time dependency, referring to reports in which the amount of potentially recruitable lung was assessed on the basis of physiological variables. In our study (see the Supplementary Appendix for our article), which used whole-lung CT, we could not find any relationship between the number of days of mechanical ventilation before the study and lung recruitability.

We thank Dr. Dixon for his correct observation. Actually, in our study, we computed the physiological and alveolar dead-space fractions, including in the standard formulas the mixed expired partial pressure of carbon dioxide and the end-tidal carbon dioxide, respectively.

We disagree with Dr. Rouby and colleagues that in our study many patients had regions of severely overdistended lung. In fact, the volume of overdistended lung is not the correct tool to assess overdistention on CT, because the volume includes both gas volume and lung-tissue volume. The issue of lung injury during mechanical ventilation lies in the amount of tissue (not gas) subjected to excessive stress and strain. Indeed, the volume of overdistended lung at a PEEP of 15 cm of water was 198±514 ml (5±11 percent of lung volume) among patients with a lower amount of potentially recruitable lung and 145±469 ml (3±9 percent of lung volume) among those with a higher amount of potentially recruitable lung, but these volumes included 183±482 and 135±434 ml of gas, respectively, and only 14±32 and 11±35 g of tissue, respectively, accounting for 1±3 percent and 1±2 percent of the total lung tissue.

Luciano Gattinoni, M.D.
Pietro Caironi, M.D.
Fondazione Istituto di Ricovero e Cura a Carattera Scientifico, 20122 Milan, Italy
gattinon@policlinico.mi.it

V. Marco Ranieri, M.D.
Azienda Ospedaliera San Giovanni Battista-Molinette, 10126 Turin, Italy

5 References

1. 1

   Borges JB, Okamoto VN, Matos GF, et al. Reversibility of lung collapse and hypoxemia in early acute respiratory distress syndrome. Am J Respir Crit Care Med (in press).
   

2. 2

   Brower RG, Morris A, MacIntyre N, et al. Effects of recruitment maneuvers in patients with acute lung injury and acute respiratory distress syndrome ventilated with high positive end-expiratory pressure. Crit Care Med 2003;31:2592-2597[Erratum, Crit Care Med 2004;32:907.]
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3. 3

   D'Angelo E, Calderini E, Robatto FM, Puccio P, Milic-Emili J. Lung and chest wall mechanics in patients with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia. Eur Respir J 1997;10:2343-2350
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4. 4

   Quintel M, Pelosi P, Caironi P, et al. An increase of abdominal pressure increases pulmonary edema in oleic acid-induced lung injury. Am J Respir Crit Care Med 2004;169:534-541
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5. 5

   The National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network. Comparison of two fluid-management strategies in acute lung injury. N Engl J Med 2006;354:2564-75
   

Citing Articles (7)

Citing Articles

1. 1

   Claude Guerin, Sophie Debord, Véronique Leray, Bertrand Delannoy, Frédérique Bayle, Gael Bourdin, Jean-Christophe Richard. (2011) Efficacy and safety of recruitment maneuvers in acute respiratory distress syndrome. Annals of Intensive Care 1:1, 9
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2. 2

   V. Tomicic, A. Fuentealba, E. Martínez, J. Graf, J. Batista Borges. (2010) Fundamentos de la ventilación mecánica en el síndrome de distrés respiratorio agudo. Medicina Intensiva 34:6, 418-427
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3. 3

   Eduardo L. V. Costa, João Batista Borges, Alexandre Melo, Fernando Suarez-Sipmann, Carlos Toufen, Stephan H. Bohm, Marcelo B. P. Amato. (2009) Bedside estimation of recruitable alveolar collapse and hyperdistension by electrical impedance tomography. Intensive Care Medicine 35:6, 1132-1137
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4. 4

   João Batista Borges, Josué Almeida Victorino, Carlos Roberto Ribeiro Carvalho. (2008) Underestimation of Lung Collapse and Under Optimization of a PEEP Trial. Intensive Care Medicine 34:3, 584-584
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5. 5

   Guillermo M Albaiceta, Lluis Blanch, Umberto Lucangelo. (2008) Static pressure–volume curves of the respiratory system: were they just a passing fad?. Current Opinion in Critical Care 14:1, 80-86
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6. 6

   Claude Guerin, Jean-Christophe Richard. (2008) Current ventilatory management of patients with acute lung injury/acute respiratory distress syndrome. Expert Review of Respiratory Medicine 2:1, 119-133
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7. 7

   Malhotra, Atul, . (2007) Low-Tidal-Volume Ventilation in the Acute Respiratory Distress Syndrome. New England Journal of Medicine 357:11, 1113-1120
   Full Text