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Evaluation of hyperoxia-induced hypercapnia in obese patients after cardiac surgery: a randomized crossover comparison of conservative and liberal oxygen administration

  • Marie-Hélène DenaultEmail author
  • Carolanne Ruel
  • Mathieu Simon
  • Pierre-Alexandre Bouchard
  • Serge Simard
  • François Lellouche
Reports of Original Investigations
  • 63 Downloads

Abstract

Purpose

Recent studies on patients with stable obesity-hypoventilation syndrome have raised concerns about hyperoxia-induced hypercapnia in this population. This study aimed to evaluate whether a higher oxygen saturation target would increase arterial partial pressure of carbon dioxide (PaCO2) in obese patients after coronary artery bypass grafting surgery (CABG).

Methods

Obese patients having CABG were recruited. With a randomized crossover design, we compared two oxygenation strategies for 30 min each, immediately after extubation: a peripheral oxygen saturation (SpO2) target of ≥ 95% achieved with manual oxygen titration (liberal) and a SpO2 target of 90% achieved with FreeO2, an automated oxygen titration device (conservative). The main outcome was end-of-period arterial PaCO2.

Results

Thirty patients were included. Mean (standard deviation [SD]) body mass index (BMI) was 34 (3) kg·m−2 and mean (SD) baseline partial pressure of carbon dioxide (PCO2) was 40.7 (3.1) mmHg. Mean (SD) end-of-period PaCO2 was 42.0 (5.4) mmHg in the conservative period, compared with 42.6 (4.6) mmHg in the liberal period [mean difference − 0.6 (95% confidence interval − 2.2 to 0.9) mmHg; P = 0.4]. Adjusted analysis for age, BMI, narcotics, and preoperative PaCO2 did not substantively change the results. Fourteen patients were retainers, showing an elevation in mean (SD) PaCO2 in the liberal period of 3.3 (4.1) mmHg. Eleven patients had the opposite response, with a mean (SD) end-of-period PaCO2 decrease of 1.8 (2.2) mmHg in the liberal period. Five patients had a neutral response.

Conclusion

This study did not show a clinically important increase in PaCO2 associated with higher SpO2 values in this specific population of obese patients after CABG. Partial pressure of carbon dioxide increased with liberal oxygen administration in almost half of the patients, but no predictive factor was identified.

Trial registration

www.clinicaltrials.gov (NCT02917668); registered 25 September, 2016.

Évaluation de l’hypercapnie induite par hyperoxie chez des patients obèses après une chirurgie cardiaque: comparaison avec devis croisé d’une administration d’oxygène conservatrice vs libérale

Résumé

Objectif

Des études récentes portant sur les patients atteints d’un syndrome obésité-hypoventilation stable ont soulevé des inquiétudes quant à l’hypercapnie induite par l’hyperoxie chez cette population. Notre étude avait pour objectif d’évaluer si une cible de saturation en oxygène plus élevée augmenterait la pression artérielle partielle de dioxyde de carbone (PaCO2) chez des patients obèses après une chirurgie de pontages aortocoronariens (PAC).

Méthode

Des patients obèses listés pour une chirurgie de PAC ont été recrutés. À l’aide d’une méthodologie d’étude randomisée avec devis croisé, nous avons comparé deux stratégies d’oxygénation pendant 30 min chacune, immédiatement après l’extubation : une cible de saturation périphérique en oxygène (SpO2) de ≥ 95 % atteinte avec une titration d’oxygène manuelle (stratégie libérale), et une cible de SpO2 de 90 % atteinte à l’aide d’un dispositif automatisé de titration de l’oxygène, FreeO2 (stratégie conservatrice). Le critère d’évaluation principal était la PaCO2 artérielle en fin de période d’étude.

Résultats

Trente patients ont été inclus dans notre étude. L’indice de masse corporelle (IMC) moyen (écart type [ÉT]) était de 34 (3) kg·m−2 et la tension partielle moyenne (ÉT) de dioxyde de carbone (PCO2) au départ était de 40,7 (3,1) mmHg. La PaCO2 moyenne (ÉT) à la fin de la période était de 42,0 (5,4) mmHg dans la période conservatrice, par rapport à 42,6 (4,6) mmHg dans la période libérale [différence moyenne − 0,6 (intervalle de confiance 95 %, − 2,2 à 0,9) mmHg; P = 0,4]. L’analyse ajustée pour tenir compte de l’âge, de l’IMC, des narcotiques et de la PaCO2 préopératoire n’a pas modifié les résultats de manière importante. Quatorze patients ont fait de la rétention de CO2, affichant une élévation de la PaCO2 moyenne (ÉT) pendant la période libérale de 3,3 (4,1) mmHg. Onze patients ont manifesté une réaction contraire, affichant une réduction moyenne (ÉT) de la PaCO2 en fin de période de 1,8 (2,2) mmHg dans la période d’administration libérale. Cinq patients ont eu une réponse neutre.

Conclusion

Cette étude n’a pas démontré d’augmentation cliniquement significative de la PaCO2 associée à des valeurs plus élevées de SpO2 dans cette population spécifique de patients obèses après une chirurgie de PAC. La pression partielle de dioxyde de carbone a augmenté lors d’une administration libérale d’oxygène chez près de la moitié des patients, mais aucun facteur prédictif n’a été identifié.

Enregistrement de l’étude

www.clinicaltrials.gov (NCT02917668); enregistrée le 25 septembre 2016.

Notes

Conflicts of interest

Mathieu Simon is a shareholder and administrator of Oxynov, the company that developed and is commercializing FreeO2. François Lellouche is a co-founder, shareholder, and administrator of Oxynov. He co-invented the FreeO2 device used in this study. François Lellouche receives financial support from the Canada Foundation for Innovation (Research program for automation of ventilation and oxygenation). Marie-Hélène Denault, Carolanne Ruel, Pierre-Alexandre Bouchard and Serge Simard declare no competing interests.

Editorial responsibility

This submission was handled by Dr. Philip M. Jones, Associate Editor, Canadian Journal of Anesthesia.

Authors contributions

Marie-Hélène Denault had full access to the data during the study and takes responsibility for data accuracy and study safety. Marie-Hélène Denault designed the study, wrote the protocol, contributed to data collection and analysis, and wrote the manuscript. Carolanne Ruel contributed to data collection. Mathieu Simon contributed to study design and reviewed the manuscript. Pierre-Alexandre Bouchard contributed to study design, data collection, and data analysis. Serge Simard oversaw the statistical analyses. François Lellouche designed the study, reviewed the protocol, and reviewed the manuscript.

Funding

Support was provided solely from institutional sources.

Supplementary material

12630_2019_1500_MOESM1_ESM.pdf (87 kb)
Supplementary material 1 (PDF 86 kb)
12630_2019_1500_MOESM2_ESM.pdf (165 kb)
eFig. 1 Working principles of FreeO2, automated oxygen titration and weaning. The device used in the study automatically titrates the oxygen flowrate (from 0 to 20 L·min−1 with minimal steps of 0.1 L·min−1), based on the SpO2 target set by the clinician and the measured SpO2. The oxygen flow rate is adjusted every second based on the difference between the measured and the targeted SpO2. In the present study, the SpO2 target was set at 90%. SpO2 = peripheral oxygen saturation. Supplementary material 2 (PDF 164 kb)
12630_2019_1500_MOESM3_ESM.pdf (204 kb)
eFig. 2 Oxygenation profiles during conservative and liberal oxygen administration periods. Upper panel represents the conservative period, bottom panel represents the liberal period. Peripheral oxygen saturation, oxygen flow rate (conservative, upper panel), and FIO2 (liberal, bottom panel) over time are shown during both periods for a typical patient. Peripheral oxygen saturation target is indicated by a black line, SpO2 by a red line, and oxygen flow or FIO2 by a green line. FiO2 = fraction of inspired oxygen; SpO2 = peripheral oxygen saturation. Supplementary material 3 (PDF 204 kb)

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Copyright information

© Canadian Anesthesiologists' Society 2019

Authors and Affiliations

  1. 1.Institut universitaire de cardiologie et de pneumologie de Québec - Université Laval Research CenterQuebecCanada

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