Recruitment maneuver: Does it promote bacterial translocation?*
Nahit Cakar, MD; Ozkan Akinci, MD; Simru Tugrul, MD; Perihan Ergin Ozcan, MD; Figen Esen, MD;
Haluk Eraksoy, MD; Atahan Cagatay, MD; Lütfi Telci, MD; Avi Nahum, MD
A
nimal experiments have dem-
onstrated repeatedly that me-
chanical ventilatory settings
are an important determinant
of ventilator-associated lung injury (1).
Recently, a large clinical trial sponsored
by the National Institutes of Health that
included 861 patients with acute lung
injury and acute respiratory distress syn-
drome showed that a low tidal volume
(V
˙
T, 6 mL/kg) compared with a high tidal
volume (12 mL/kg) setting during me-
chanical ventilation significantly de-
creased mortality rates (2). Amato et al.
(3) were the first to demonstrate that the
mechanical ventilation strategy was an
important determinant of mortality rate
in patients with acute respiratory distress
syndrome. They proposed that positive
end-expiratory pressure (PEEP) be based
on the lower inflection point of the infla-
tion pressure-volume curve and that V
˙
T
be limited to maintain end-inflation pla-
teau pressures below the upper inflection
point of the pressure-volume curve. In
this study, sustained inflation maneuvers
were used to recruit collapsed lung units
after suctioning or loss of PEEP (3).
In the last few years, experimental and
clinical studies have shown beneficial ef-
fects of recruitment maneuvers (sus-
tained inflation and/or sigh) on ventila-
tory and gas exchange variables (4, 5).
However, recent experimental studies
also have shown that large V
˙
T with high
inspiratory peak airway opening pres-
sures (Pao) can promote bacterial trans-
location of intratracheally inoculated
bacteria into the systemic circulation
rather quickly (6, 7). In rats intratrache-
ally inoculated with Klebsiella pneu-
moniae, Verbrugge et al. (6) observed
positive blood cultures after 180 mins,
whereas Nahum and colleagues (7) ob-
served positive blood cultures only after
30 mins in a dog model of Escherichia
coli pneumonia. Given the right experi-
mental conditions, translocation of bac-
teria from the alveoli to the systemic cir-
culation can occur within minutes (8).
Potentially, recruitment maneuvers
applied as sighs or sustained inflations
may damage the integrity of the alveolar-
epithelial barrier. In this study, we ex-
plored whether recruitment maneuvers
applied as a sustained inflation disrupt
the alveolar-epithelial barrier as judged
*See also p. 2161.
From the Department of Anesthesiology and Inten-
sive Care (NC, OA, ST, PEO, FE, LT) and the Depart-
ment of Clinical Bacteriology and Infectious Diseases
(HE, AC), Istanbul Medical Faculty, Istanbul, Turkey;
and the Department of Pulmonary and Critical Care
(AN), University of Minnesota, Regions Hospital, St.
Paul, MN.
This study was performed in the experimental
laboratory founded by Prof. Dr. Kutay Akpir in Istanbul
University in Department of Anesthesiology and Inten-
sive Care.
Supported, in part, by grant SCOR 35 HL-50152
from the National Institutes of Health, Bethesda, MD.
Copyright © 2002 by Lippincott Williams & Wilkins
DOI: 10.1097/01.CCM.0000026726.32713.0A
Objective: High peak airway opening pressures (Pao) are used
routinely during recruitment maneuvers to open collapsed lung
units. High peak Pao, however, can cause lung injury as evi-
denced by translocation of intratracheally inoculated bacteria. In
this study we explored whether recruitment maneuvers that used
high Pao could cause translocation of the intratracheally inocu-
lated Pseudomonas aeruginosa from the alveoli into the systemic
circulation.
Design: Prospective, randomized, animal study.
Setting: Experimental animal care laboratory.
Subjects: Eighteen male Sprague Dawley rats.
Interventions: Rats were anesthetized, tracheostomized, and
ventilated with 14 cm H
2
O peak Pao and 0 cm H
2
O positive
end-expiratory pressure (PEEP) in pressure-controlled ventilation
(frequency, 30 bpm; inspiratory/expiratory ratio, 1:2; FiO
2
, 1).
Intratracheal inoculation of 500 L of saline containing 1 10
5
colony forming units/mL P. aeruginosa was performed before
randomization into three groups (n 6 in each): a low-pressure
group (14 cm H
2
O peak Pao, 0 cm H
2
O PEEP), a high-pressure
group (45 cm H
2
O peak Pao, 0 cm H
2
O PEEP), and a recruitment
maneuver group (14 cm H
2
O peak Pao, 0 cm H
2
O PEEP, and a
recruitment maneuver sustained inflation of 45 cm H
2
O continu-
ous positive airway pressure for 30 secs every 15 mins). Blood
samples for blood gas analysis were obtained before intratracheal
instillation of bacteria and at the end of the experimental protocol
(2 hrs). Blood cultures were obtained before and after bacterial
instillation at 30-min intervals during the experiment. Blood sam-
ples were cultured directly in sheep blood, MacConkey, and
Iso-Sensitest agars and were observed on the second day. Bac-
teremia was defined as the presence of one or more colonies of
P. aeruginosa in 1 mL of blood.
Measurements and Main Results: The blood cultures were
positive for P. aeruginosa in only six rats in the high-pressure
group and remained negative throughout the study period in the
low-pressure and recruitment maneuver groups. Oxygenation de-
teriorated in all groups after intratracheal instillation of bacteria.
In the high-pressure group, oxygenation decreased from 417 67
mm Hg to 79 20 mm Hg (p .004), whereas in the low-
pressure and recruitment maneuver groups PaO
2
decreased from
410 98 mm Hg and 383 78 mm Hg to 287 105 mm Hg (p
.031) and 249 59 mm Hg (p .11), respectively.
Conclusion: Intermittent recruitment maneuvers applied as a
sustained inflation superimposed on low-pressure ventilation
with 0 cm H
2
O PEEP did not cause translocation of intratracheally
inoculated P. aeruginosa. (Crit Care Med 2002; 30:2103–2106)
KEY WORDS: recruitment maneuver; bacterial translocation; me-
chanical ventilation; sustained inflation; Pseudomonas aerugi-
nosa; oxygenation; pneumonia; ventilation-associated lung injury
2103 Crit Care Med 2002 Vol. 30, No. 9