Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements

Eduardo A Osawa^{1

2

3}, Salvatore L Cutuli^{4

5}, Fumitaka Yanase^{3

6}, Naoya Iguchi^{3

7

8}, Laurent Bitker⁹, Alexandre T Maciel^{1

2}, Yugeesh R Lankadeva^{8

10}, Clive N May^{8

10}, Roger G Evans^{8

11}, Glenn M Eastwood^{3

6}, Rinaldo Bellomo^{12

13

14}

Affiliations

¹ Imed Group Research Department, Sao Paulo, Brazil.
² Intensive Care Unit, Hospital Sao Camilo, Unidade Pompeia, Sao Paulo, Brazil.
³ Department of Intensive Care, Austin Hospital, Melbourne, VIC, 3084, Australia.
⁴ Dipartimento di Scienze dell'Emergenza, Anestesiologiche e della Rianimazione, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.
⁵ Università Cattolica del Sacro Cuore, Rome, Italy.
⁶ Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia.
⁷ Department of Anaesthesiology and Intensive Care Medicine, Graduate School of Medicine, Osaka University, Suita, Japan.
⁸ Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia.
⁹ Service de Médecine Intensive - Réanimation, Hôpital de La Croix Rousse, Hospices Civils de Lyon, Lyon, France.
¹⁰ Department of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC, Australia.
¹¹ Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia.
¹² Department of Intensive Care, Austin Hospital, Melbourne, VIC, 3084, Australia. rinaldo.bellomo@austin.org.au.
¹³ Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia. rinaldo.bellomo@austin.org.au.
¹⁴ Department of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC, Australia. rinaldo.bellomo@austin.org.au.

PMID: 36504004
PMCID: PMC9742069
DOI: 10.1186/s40635-022-00479-y

Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements

Eduardo A Osawa et al. Intensive Care Med Exp. 2022.

. 2022 Dec 12;10(1):52.

doi: 10.1186/s40635-022-00479-y.

Authors

Affiliations

¹ Imed Group Research Department, Sao Paulo, Brazil.
² Intensive Care Unit, Hospital Sao Camilo, Unidade Pompeia, Sao Paulo, Brazil.
³ Department of Intensive Care, Austin Hospital, Melbourne, VIC, 3084, Australia.
⁴ Dipartimento di Scienze dell'Emergenza, Anestesiologiche e della Rianimazione, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.
⁵ Università Cattolica del Sacro Cuore, Rome, Italy.
⁶ Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia.
⁷ Department of Anaesthesiology and Intensive Care Medicine, Graduate School of Medicine, Osaka University, Suita, Japan.
⁸ Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia.
⁹ Service de Médecine Intensive - Réanimation, Hôpital de La Croix Rousse, Hospices Civils de Lyon, Lyon, France.
¹⁰ Department of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC, Australia.
¹¹ Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia.
¹² Department of Intensive Care, Austin Hospital, Melbourne, VIC, 3084, Australia. rinaldo.bellomo@austin.org.au.
¹³ Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia. rinaldo.bellomo@austin.org.au.
¹⁴ Department of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC, Australia. rinaldo.bellomo@austin.org.au.

PMID: 36504004
PMCID: PMC9742069
DOI: 10.1186/s40635-022-00479-y

Abstract

Background: Continuous measurement of urinary PO₂ (PuO₂) is being applied to indirectly monitor renal medullary PO₂. However, when applied to critically ill patients with shock, its measurement may be affected by changes in FiO₂ and PaO₂ and potential associated O₂ diffusion between urine and ureteric or bladder tissue. We aimed to investigate PuO₂ measurements in septic shock patients with a fiberoptic luminescence optode inserted into the urinary catheter lumen in relation to episodes of FiO₂ change. We also evaluated medullary and urinary oxygen tension values in Merino ewes at two different FiO₂ levels.

Results: In 10 human patients, there were 32 FiO₂ decreases and 31 increases in FiO₂. Median pre-decrease FiO₂ was 0.36 [0.30, 0.39] and median post-decrease FiO₂ was 0.30 [0.23, 0.30], p = 0.006. PaO₂ levels decreased from 83 mmHg [77, 94] to 72 [62, 80] mmHg, p = 0.009. However, PuO₂ was 23.2 mmHg [20.5, 29.0] before and 24.2 mmHg [20.6, 26.3] after the intervention (p = 0.56). The median pre-increase FiO₂ was 0.30 [0.21, 0.30] and median post-increase FiO₂ was 0.35 [0.30, 0.40], p = 0.008. PaO₂ levels increased from 64 mmHg [58, 72 mmHg] to 71 mmHg [70, 100], p = 0.04. However, PuO₂ was 25.0 mmHg [IQR: 20.7, 26.8] before and 24.3 mmHg [IQR: 20.7, 26.3] after the intervention (p = 0.65). A mixed linear regression model showed a weak correlation between the variation in PaO₂ and the variation in PuO₂ values. In 9 Merino ewes, when comparing oxygen tension levels between FiO₂ of 0.21 and 0.40, medullary values did not differ (25.1 ± 13.4 mmHg vs. 27.9 ± 15.4 mmHg, respectively, p = 0.6766) and this was similar to urinary oxygen values (27.1 ± 6.17 mmHg vs. 29.7 ± 4.41 mmHg, respectively, p = 0.3192).

Conclusions: Changes in FiO₂ and PaO₂ within the context of usual care did not affect PuO₂. Our findings were supported by experimental data and suggest that PuO₂ can be used as biomarker of medullary oxygenation irrespective of FiO₂.

Keywords: Inspired oxygen fraction; Sepsis; Septic shock; Urinary oxygen tension; Urinary oxygenation.

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Conflict of interest statement

The authors have no conflicts of interest to declare.

Figures

**Fig. 1**
Schematic representation of the procedure used to obtain PaO₂ and PuO₂ measurements before and after an episode of FiO₂ change during the observation period. ABG: arterial blood gas; FiO₂: fraction of inspired oxygen; PuO₂: urinary oxygen tension

**Fig. 2**
Scatterplot of arterial and urinary oxygen tension measured in the ten patients enrolled in the study. PuO₂: urinary oxygen tension; PaO₂: arterial blood oxygen tension

**Fig. 3**
Box plot representation of arterial blood oxygen tension before and after changes in fractional inspired oxygen. FiO₂: fractional inspired oxygen; PaO₂: arterial blood oxygen tension

**Fig. 4**
Box plot representation of urinary oxygen tension before and after changes in fractional inspired oxygen. FiO₂: fractional inspired oxygen; PuO₂: urinary oxygen tension

**Fig. 5**
Relationship between the changes in arterial oxygen tension (Δ PaO₂) and urinary oxygen tension (Δ PuO₂)

See this image and copyright information in PMC

References

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Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements

Affiliations

Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements

Authors

Affiliations

Abstract

Conflict of interest statement

Figures

References

LinkOut - more resources

Full Text Sources