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Brazilian Journal of Cardiovascular Surgery

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ORIGINAL ARTICLE • Braz. J. Cardiovasc. Surg. 34 (06) • Nov-Dec 2019 • https://doi.org/10.21470/1678-9741-2019-0016 copy

Impact of Lung Expansion Therapy Using Positive End-Expiratory Pressure in Mechanically Ventilated Patients Submitted to Coronary Artery Bypass Grafting

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Objective:

To evaluate the impact of different levels of positive end-expiratory pressure (PEEP) on gas exchange in patients undergoing coronary artery bypass grafting (CABG).

Methods:

A randomized clinical trial was conducted with patients undergoing CABG surgery. Patients were randomized into three groups: Group 10, PEEP of 10 cmH₂O; Group 12, PEEP of 12 cmH₂O; and Group 15, PEEP of 15 cmH₂O. After the randomization, all patients underwent gas analysis at three moments: (1) before lung expansion therapy (LET); (2) 30 minutes after LET; and (3) one hour after extubation.

Results:

Sixty-six patients were studied, of which 61.7% were men, with mean age of 64 ± 8.9 years. Patients allocated to Group 15 showed a significant improvement in gas exchange comparing pre- and post-expansion values (239±21 vs. 301±19, P<0,001) and the increase was maintained after extubation (278±26). Despite the use of high levels of PEEP, no significant hemodynamic change was evidenced.

Conclusion:

It is concluded that high levels of PEEP (15 cmH₂O) are beneficial for the improvement of gas exchange in patients undergoing CABG.

Keywords:
Coronary Artery Bypass; Hemodynamics; Airway Extubation; Lung; Positive-Pressure Respiration

Abbreviations, acronyms & symbols
AMI	= Acute myocardial infarction		ICU	= Intensive care unit
ANOVA	= Analysis of variance		LET	= Lung expansion therapy
BMI	= Body mass index		MBP	= Mean arterial pressure
CABG	= Coronary artery bypass grafting		MV	= Mechanical ventilation
DBP	= Diastolic blood pressure		PEEP	= Positive end-expiratory pressure
DM	= Diabetes mellitus		PS	= Supportive pressure
EPAP	= Positive expiratory pressure		SaO₂	= Arterial oxygen saturation
FiO₂	= Inspired fraction of oxygen		SBP	= Systolic blood pressure
HR	= Heart rate		SPSS	= Statistical Package for the Social Sciences

Variable	PEEP 10 (n: 19)	PEEP 12 (n: 23)	PEEP 15 (n: 18)	P-value
Sex				0.56^a a Chi-square test;
Male	11 (58%)	13 (57%)	11 (61%)
Female	8 (42%)	10 (43%)	7 (39%)
Age (years)	62±11	62±9	64±7	0.23^b b analysis of variance (ANOVA); AMI=acute myocardial infarction; BMI=body mass index; CABG=coronary artery bypass grafting; DM=diabetes mellitus; MV=mechanical ventilation; PEEP=positive end-expiratory pressure
BMI (kg/m²)	23±3	22±4	23±4	0.89^b b analysis of variance (ANOVA); AMI=acute myocardial infarction; BMI=body mass index; CABG=coronary artery bypass grafting; DM=diabetes mellitus; MV=mechanical ventilation; PEEP=positive end-expiratory pressure
Comorbidities
Hypertension	12 (63%)	14 (61%)	12 (67%)	0.76^a a Chi-square test;
DM	8 (42%)	7 (30%)	8 (44%)	0.60^a a Chi-square test;
Dyslipidemia	7 (37%)	7 (30%)	8 (44%)	0.98^a a Chi-square test;
Smoking	2 (11%)	3 (13%)	3 (17%)	0.78^a a Chi-square test;
AMI	4 (21%)	3 (13%)	3 (17%)	0.87^a a Chi-square test;
Extracorporeal circulation time (min)	63±17	63±18	67±20	0.45^b b analysis of variance (ANOVA); AMI=acute myocardial infarction; BMI=body mass index; CABG=coronary artery bypass grafting; DM=diabetes mellitus; MV=mechanical ventilation; PEEP=positive end-expiratory pressure
Bypass	2.5±0.7	2.8±0.5	2.3±0.5	0.22^b b analysis of variance (ANOVA); AMI=acute myocardial infarction; BMI=body mass index; CABG=coronary artery bypass grafting; DM=diabetes mellitus; MV=mechanical ventilation; PEEP=positive end-expiratory pressure
MV time (hours)	6±2	7 ± 3	6 ± 3	0.87^b b analysis of variance (ANOVA); AMI=acute myocardial infarction; BMI=body mass index; CABG=coronary artery bypass grafting; DM=diabetes mellitus; MV=mechanical ventilation; PEEP=positive end-expiratory pressure

Variable	PEEP 10 (n: 19)	PEEP 12 (n: 23)	PEEP 15 (n: 18)	P^a-value
Oxygenation index
Before LET	230±23	246±17	239±21	0.93
After LET	250±19	262±19	301±19	0.03
After extubation	240±23	259±22	278±26	0.02
P^a a analysis of variance (ANOVA); CABG=coronary artery bypass grafting; LET=lung expansion therapy; PEEP=positive end-expiratory pressure; SaO2=arterial oxygen saturation	0.45	0.65	<0.001
SaO₂ (%)
Before LET	95±2.3	97±2	96±1.6	0.50
After LET	97±1.2	98±1.7	99±0.7	0.25
After extubation	96±1.9	97±1.4	98±1.1	0.54
P	0.66	0.38	0.49

Variable		PEEP 10 (n: 19)	PEEP 12 (n: 23)	PEEP 15 (n: 18)	P^a a analysis of variance (ANOVA); -value
SBP (mmHg)	Before LET	114±15	121±16	125±17	0.08
	After LET	106±8	111±17	119±17	0.28
	P ^b b paired Student's t-test; CABG=coronary artery bypass grafting; DBP=diastolic blood pressure; HR=heart rate; LET=lung expansion therapy; MBP=mean arterial pressure; PEEP=positive end-expiratory pressure; SBP=systolic blood pressure	0.06	0.16	0.35
DBP (mmHg)	Before LET	60±7	64±3	65±6	0.50
	After LET	57±7	61±9	59±7	0.28
	P ^b b paired Student's t-test; CABG=coronary artery bypass grafting; DBP=diastolic blood pressure; HR=heart rate; LET=lung expansion therapy; MBP=mean arterial pressure; PEEP=positive end-expiratory pressure; SBP=systolic blood pressure	0.41	0.35	0.48
MBP (mmHg)	Before LET	78±11	83±9	85±9	0.59
	After LET	73±8	78±11	79±9	0.76
	P	0.78	0.88	29
HR (bpm)	Before LET	104±9	102±21	104±8	0.86
	After LET	103±7	99±12	100±12	0.76
	P	0.31	0.56	0.24

Author's roles & responsibilities
ALLC	Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; drafting the work or revising it critically for important intellectual content; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved; final approval of the version to be published
SC	Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; final approval of the version to be published
MCL	Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; final approval of the version to be published
AVF	Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; final approval of the version to be published
BF	Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; final approval of the version to be published
LS	Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; final approval of the version to be published
QO	Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; final approval of the version to be published
ARG	Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; final approval of the version to be published

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