• Ida-Maria Forsberg, Jonathan Al-Saadi, Albin Sjöblom, Lisa Grape, Johan Petersson, Johan Lundberg, Ase Lodenius, Lars I Eriksson, and FagerlundMalin JonssonMJ.
• From the Department of Physiology and Pharmacology, Section for Anesthesiology and Intensive Care Medicine (IMF, AS, JP, AL, LIE, MJF), Department of Perioperative Medicine and Intensive Care, Karolinska University Hospital (IMF, AS, LG, JP, LIE, MJF), Department of Clinical Neuroscience, Karolinska Institutet (JAS, JL) and Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden (JL).
• Eur J Anaesthesiol. 2023 Aug 1; 40 (8): 568577568-577.

BackgroundApnoeic oxygenation with high-flow nasal oxygen prolongs the safe apnoeic period during induction of general anaesthesia. However, central haemodynamic effects and the characteristics of central gaseous exchange remain unexplored.ObjectiveTo describe mean pulmonary arterial pressure along with arterial and mixed venous blood gases and central haemodynamic parameters during apnoeic oxygenation with low-flow and high-flow nasal oxygen in pigs.DesignExperimental crossover study.SettingAnimal study of 10 healthy Swedish landrace pigs at Karolinska Institutet, Sweden, April-May 2021.InterventionThe pigs were anaesthetised, their tracheas intubated and their pulmonary arteries catheterised. The animals were preoxygenated and paralysed before apnoea. Apnoeic periods between 45 and 60 min were implemented with either 70 or 10 l min -1 100% O 2 delivered via nasal catheters. In addition, seven animals underwent an apnoea without fresh gas flow. Cardiopulmonary parameters and blood gases were measured repeatedly.Main Outcome MeasuresMean pulmonary arterial pressure during apnoeic oxygenation with high-flow and low-flow oxygen.ResultsNine pigs completed two apnoeic periods of at least 45 min with a Pa O 2 not lower than 13 kPa. The mean pulmonary arterial pressure increased during 45 min of apnoea, from 18 ± 1 to 33 ± 2 mmHg and 18 ± 1 to 35 ± 2 mmHg, at 70 and 10 l min -1 O 2 , respectively ( P  < 0.001); there was no difference between the groups ( P  = 0.87). The Pa CO 2 increased by 0.48 ± 0.07 and 0.52 ± 0.04 kPa min -1 , at 70 and 10 l min -1 O 2 , respectively; there was no difference between the groups ( P  = 0.22). During apnoea without fresh gas flow, the SpO 2 declined to less than 85% after 155 ± 11 s.ConclusionDuring apnoeic oxygenation in pigs, the mean pulmonary arterial pressure increased two-fold and Pa CO 2 five-fold after 45 min, while the arterial oxygen levels were maintained over 13 kPa, irrespective of high-flow or low-flow oxygen.Copyright © 2023 European Society of Anaesthesiology and Intensive Care. Unauthorized reproduction of this article is prohibited.

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