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Br J Anaesth. 2017 Dec 1;119(6):1194-1205. doi: 10.1093/bja/aex192.

Individualized positive end-expiratory pressure in obese patients during general anaesthesia: a randomized controlled clinical trial using electrical impedance tomography.

Author information

1
Department of Anaesthesia and Intensive Care Medicine, University of Leipzig, Liebigstraße 20, 04103 Leipzig, Germany.
2
Integrated Research and Treatment Centre (IFB) AdiposityDiseases.
3
Clinical Trial Centre.
4
Department of Surgery, University of Leipzig, Leipzig, Germany.
5
Laboratory of Pulmonary Engineering, Biomedical Engineering Program, Alberto Luis Coimbra Institute of Post-Graduation and Research in Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
6
Department of Electronic Engineering and Postgraduate Program of Electrical Engineering, Federal University of Minas Gerais, Belo Horizonte, Brazil.
7
Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

Abstract

Background:

General anaesthesia leads to atelectasis, reduced end-expiratory lung volume (EELV), and diminished arterial oxygenation in obese patients. We hypothesized that a combination of a recruitment manoeuvre (RM) and individualized positive end-expiratory pressure (PEEP) can avoid these effects.

Methods:

Patients with a BMI ≥35 kg m -2 undergoing elective laparoscopic surgery were randomly allocated to mechanical ventilation with a tidal volume of 8 ml kg -1 predicted body weight and (i) an RM followed by individualized PEEP titrated using electrical impedance tomography (PEEP IND ) or (ii) no RM and PEEP of 5 cm H 2 O (PEEP 5 ). Gas exchange, regional ventilation distribution, and EELV (multiple breath nitrogen washout method) were determined before, during, and after anaesthesia. The primary end point was the ratio of arterial partial pressure of oxygen to inspiratory oxygen fraction ( P aO 2 / F iO 2 ).

Results:

For PEEP IND ( n =25) and PEEP 5 ( n =25) arms together, P aO 2 / F iO 2 and EELV decreased by 15 kPa [95% confidence interval (CI) 11-20 kPa, P <0.001] and 1.2 litres (95% CI 0.9-1.6 litres, P <0.001), respectively, after intubation. Mean ( sd ) PEEP IND was 18.5 (5.6) cm H 2 O. In the PEEP IND arm, P aO 2 / F iO 2 before extubation was 23 kPa higher (95% CI 16-29 kPa; P <0.001), EELV was 1.8 litres larger (95% CI 1.5-2.2 litres; P <0.001), driving pressure was 6.7 cm H 2 O lower (95% CI 5.4-7.9 cm H 2 O; P <0.001), and regional ventilation was more equally distributed than for PEEP 5 . After extubation, however, these differences between the arms vanished.

Conclusions:

In obese patients, an RM and higher PEEP IND restored EELV, regional ventilation distribution, and oxygenation during anaesthesia, but these differences did not persist after extubation. Therefore, lung protection strategies should include the postoperative period.

Clinical trial registration:

German clinical trials register DRKS00004199, www.who.int/ictrp/network/drks2/en/ .

KEYWORDS:

bariatric surgery; lung volume measurements; morbid; obesity; positive-pressure respiration; pulmonary gas exchange

PMID:
29045567
DOI:
10.1093/bja/aex192
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