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Page 2 of 12 Echeverria-Villalobos et al. Vessel Plus 2019;3:33 I http://dx.doi.org/10.20517/2574-1209.2019.12

mechanical ventilation (PMV) strategies such as the use of continuous positive airway pressure (CPAP)
[2]
have shown benefits in non-cardiac surgeries . Likewise, CPAP, low tidal volume (V ) and recruitment
T
maneuvers have been used in patients undergoing cardiac surgeries under CPB aiming to ameliorate lung
[5,6]
mechanics and to decrease postoperative pulmonary complications (PPCs) .
Mild respiratory dysfunction is commonly reported after cardiac surgery under CPB with a small
[7]
percentage of patients developing severe lung dysfunction . Even though protective ventilation strategies
have been associated with decreased levels of pro-inflammatory cytokines and improved lung mechanics,
its impact on other postoperative long-term outcomes such as PPCs and hospital length of stay (LOS)
remains unclear.

A comprehensive review of current literature was carried out aiming to describe the pulmonary physio-
pathological changes experienced by patients undergoing cardiac surgery with and without CPB and
treated under different ventilation strategies. Likewise, the incidence of PPCs in patients with and without
continuous MV during CPB was analyzed.

METHODS
A literature search on PubMed, Embase, and Cochrane Library databases was carried out in order to
identify manuscripts published between 01 Jan 2014 and 31 Jan 2019 describing MV and pulmonary
complications in patients undergoing CPB surgery. We used Medical Subject Headings involving the terms
“MV” (combined with “CPB”, “CPB and lung injury”, “CPB and morbidity”, “CPB and mortality”, “CPB
and pulmonary perfusion”, “cardiac surgery and oxygen diffusion”), “CPB” [combined with “pulmonary
complications”, “CPAP”, “positive end-expiratory pressure (PEEP)”, “lung injury”, “lung mechanics”], and
“lung protective ventilation in CPB surgery”. Our search was limited to manuscripts in English language,
involving adult patients only, clinical trials (including phase I-IV studies), narrative reviews, and systematic
reviews (with or without meta-analysis). Case reports were only considered if they were needed to support
specific clinical findings not previously discussed. Moreover, we excluded manuscripts referring to CPB
surgery outside the scope of this review, conference abstracts, thesis, and trials involving children or
patients undergoing other cardiac surgeries different from CPB.

RESULTS
Initially, we identified 207 manuscripts out of which 46 were duplicates. After title/abstract screening, 113
manuscripts were out of the scope of this review and thereby excluded. Therefore, 48 articles qualified
for full-test revision. Thirty-five (n = 35) articles were excluded due to no CPB surgery or intraoperative
ventilation was discussed (n = 27), case reports (n = 2), protocol design (n = 2), trials involving cardiac
surgeries in children (n = 1), thesis (n = 1), and no full-text available (n = 2). Therefore, 13 articles were
[2]
included for further description in our qualitative analysis: systematic review and meta-analysis (n = 1) ,
[12]
[8]
meta-analysis (n = 1) , randomized clinical trials or RCTs (n = 3) [9-11] , prospective observational (n = 1) ,
and reviews (n = 7) [4-6,13-16] . Figure 1 describes the flow diagram corresponding to our search.

MV during CPB and serum inflammatory markers
A total of 3 RCTs and 1 prospective observational trial (n = 157 patients) studied the impact of
intraoperative MV on inflammatory markers such as cytokines in patients undergoing cardiac surgery
with CPB [Table 1] [9-12] . Two RCTs involved one group with low V (3-4 mL/kg) MV and PEEP whereas
T
no ventilation was administered in a second group [9,10] . Another RCT assigned patients to either one of
the following groups: patients without MV (MV group), patients receiving protective ventilation with
[11]
continuous low V ventilation (LTV), and patients with CPAP of 10 cmH O (CPAP group) . Moreover,
T
2
one prospective observational study allocated patients into 2 groups based on: MV or apnea with PEEP