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Safety of interhospital transfer for critically ill COVID-19 patients

During the COVID-19 pandemic, patients had to undergo interhospital transfer (IHT) for multiple reasons such as local shortages or requirement of advanced therapies. The aim of this study was to investigate the safety of ground-based IHT in critically ill COVID-19 patients performed by specifically trained experts.

This retrospective multicentre investigation includes eight hospitals from 1st February 2020 to 14th December 2022. Relocations were considered, when admitting ward was an ICU. All transfers were ground-based conducted by three specialists, with each transport being supervised entirely by one physician (trained for anaesthesia and intensive care) and a medically trained assistance. The PaO2/FiO2 ratios were obtained in the units before transfer and immediately after admission to the destination ward.

Continuous variables were tested by T test (normal distributed) or Mann-Whitney-U test (not-normal distributed), presented as median with interquartile range. χ2 test was used to analyse categorical variables, provided as numbers with corresponding percentages. Correlations were determined by the Pearson correlation coefficient (PaO2/FiO2 correlations) or the Spearman's rank correlation coefficient (survival correlations).

For comparison between transferred patients and non-relocated patients, a propensity score matching (PSM) (caliper width:  0.01) was applied. PSM included sex, age, IMV, prone positioning, vasopressors, RRT and the number of comorbidities.

We obtained transport data of 175 transfers in 148 patients. The median distance was 70 km (23–95) and the median duration was 50 min (30–85). The transferred cohort was mainly male (66.9%), 62 years (55–73) old and exhibits a SAPS III of 54 (49–63). Additional baseline characteristics of transferred patients and a propensity score matched control cohort are presented in Additional file 1: Table S1.

Table 1 Patient transfer characteristics and PaO2/FiO2 alterations

The majority of patients (41.7%) was suffering from severe acute respiratory distress syndrome (ARDS) at begin of transfer [1]. A total of 103 patients (n = 58.9%) were invasively mechanically ventilated during the entire transfer.

In the overall cohort, the median PaO2/FiO2 ratio obtained before start of transport was 111.0 mmHg (80.0–174.9) and 124.4 mmHg (85.8–195.0, p = 0.300) after relocation. In the subgroup of patients with moderate or severe ARDS, a statistically significant increase in the PaO2/FiO2 ratios was observed (100.0 vs. 108.0; p = 0.031). No correlation between the changes of PaO2/FiO2 ratios and duration or distance of transfers (distance: Pearson correlation: 0.086, p = 0.307; duration: Pearson correlation: 0.072, p = 0.394) was seen (Table 1). Additionally, no correlation between ICU survival and duration or distance was found (distance: correlation coefficient: 0.137, p = 0.071; duration: correlation coefficient: 0.125, p = 0.099). None of the transferred patients died during transport or within 24 h after transfer.

When comparing transferred patients to a PSM group which was not transferred both, ICU mortality (29.1% vs. 25.0%; p = 0.432) and hospital mortality (31.8% vs. 27.0%; p = 0.372) tended to be numerically higher. The same pattern was found for ICU and hospital length of stay (Additional file 1: Table S1).

Our analyses showed stable or rising values in PaO2/FiO2 ratios during transfer. These results are in contrast to previous investigations using air transport [2], which could be caused by a PaO2 drop in high altitude or the higher number of hand overs in the mentioned study. Neither the duration nor the distance of the IHTs affected the changes in PaO2/FiO2 ratios in our analysis, whereas the use of respirators commonly used in ICUs during transport could be one reason for the stable PaO2/FiO2 ratios. Additionally, the intensified monitoring and ventilatory support during transport may have resulted in better and more personalised care. The physician-to-patient ratio of 1:1 enabled a rapid response to deterioration of patients’ clinical status by adaptation of therapy. This may have a particular effect in moderate to severe ARDS patients and thus lead to a significant improvement. Though remarkable, the even higher PaO2/FiO2 ratios after transfer in patients with moderate or severe ARDS should be interpreted with caution, as it is unknown whether the improvement of respiratory status was sustainable.

The mortality rates were similar to previous analyses about relocations due to capacity or medical reasons [3, 4]. Higher rates of interventions may reflect a more severe disease state in our transferred patients compared to similar cohorts [5]. However, the fact that no deaths occurred 24 h following the transport indicates that a causal relationship between the transport itself and mortality is unlikely.

The strengths of this study are the comprehensiveness of our registry capturing all critically ill COVID-19 patients from the region during the observation period, the small number of experts having conducted all transfers and recorded PaO2/FiO2 ratios as respiratory marker. Additionally, the performed PSM (calliper width: 0.01) is precise and enables good comparability. We are aware of some limitations, which include the retrospective character and limited availability of data about administered drugs during IHTs.

This study shows that ground-based IHT can be performed safely and without deterioration of respiratory status by specialised personnel and equipment during a pandemic. These data support using ground-based IHTs as a fixed component of ICU resource optimisation in times of shortages.

Availability of data and materials

The datasets used and analysed in the current study are available from the corresponding author on reasonable request.


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Furthermore, we would like to thank all collaborators, who helped in the treatment of COVID-19 patients in Tyrol, Austria.


Romuald Bellmann1, Adelheid Ditlbacher1, Walter Hasibeder5, Christoph Krismer6, Hannah Antretter5, Julia Killian5, Stephan Eschertzhuber7, Stefanie Zagitzer-Hofer8, Eva Foidl9, Isabella Weilguni9, Stefanie Haslauer-Mariacher9, Alexandra Ribitsch10, Andreas Mayr11, Eugen Ladner12, Bernhard Mayr-Hueber13, Birgit Stögermüller13, Lukas Kirchmair13, Bruno Reitter14, Miriam Potocnik14, Simon Mathis15, Anna Fiala15, Jürgen Brunner16, Claudius Thomé17

5Department of Anaesthesiology and Critical Care Medicine, Hospital St. Vinzenz Zams, Zams, Austria; 6Department of Internal Medicine, Hospital St. Vinzenz Zams, Zams, Austria; 7Department of Anaesthesia and Intensive Care Medicine, Hospital Hall, Hall, Austria; 8Department of Internal Medicine, Hospital Hall, Hall, Austria; 9Department of Anaesthesia and Intensive Care Medicine, Hospital Kufstein, Kufstein, Austria; 10Department of Internal Medicine, Hospital Lienz, Lienz, Austria; 11Department of Anaesthesia and Intensive Care Medicine, Hospital Lienz, Lienz, Austria; 12Department of Anaesthesia and Intensive Care Medicine, Hospital Reutte, Reutte, Austria; 13Department of Anaesthesia and Critical Care Medicine, Hospital Schwaz, Schwaz, Austria; 14Department of Anaesthesia and Intensive Care Medicine, Hospital St. Johann in Tyrol, St. Johann in Tyrol, Austria; 15Department of General and Surgical Intensive Care Medicine, Medical University Innsbruck, Innsbruck, Austria; 16Department of Paediatrics, Medical University Innsbruck, Innsbruck, Austria; 17Department of Neurosurgery, Medical University Innsbruck, Innsbruck, Austria.


The Tyrolean COVID-19 intensive care registry was supported by the Tyrolean Government (Project F.45824).

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All authors contributed to the study conception and design. FP and MJ wrote the first draft of the manuscript. All authors collected data and read and approved the final manuscript.

Corresponding author

Correspondence to Michael Joannidis.

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Ethical approval

The study was approved by the Ethics Committee of the Medical University Innsbruck (Nr. 1099/2020). Informed consent was obtained according to local regulations. The study was performed in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines.

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The authors declare that they have no competing interests.

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Supplementary Information

Additional file 1. Table S1:

Comparison between propensity score matched group (critically ill, no transfer) and transferred group.

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Perschinka, F., Niedermoser, H., Peer, A. et al. Safety of interhospital transfer for critically ill COVID-19 patients. Crit Care 27, 456 (2023).

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