Apnea Test Safety in Brain Death: A Single-Center Retrospective Cohort Analysis
Bibliographic record
Abstract
Background: The apnea test, which is considered positive when no spontaneous breathing movements are observed following maximal hypercapnia (PaCO 2 > 55 mm Hg) respiratory center stimulation, was critically evaluated in this study by assessment of blood gas analyses performed during brain death protocols from 2010 to 2017, in the intensive care units of the Universidade Estadual de Campinas (UNICAMP). Methods: A retrospective cohort analysis based on the intensive care unit and Transplant Organ Search Organization data banks. Blood gas analyses before (pre-first and -second apnea tests) as after (after-first and -second apnea tests) were assessed. Descriptive statistical analyses of the numerical variables (such as pH, PaO 2 , PaCO 2 , HCO 3, SatO 2 ) with mean values and standard deviation, medians, and quartiles were performed. The Student’s t -test was used for pairwise group comparisons. A P < 0.05 level was adopted for significance. Results: Eighty-seven protocols were evaluated. The mean apnea test duration was 11 min. All of the patients were under vasoactive drugs. Only five apnea tests were interrupted before the end at 10 min due to rapid desaturation (SatO 2 < 90%), with no invalidated apnea test. Mean and standard deviation of blood gas tests assessed before the first apnea test were: pH 7.35(± 0.10), PaO 2 252.15 mm Hg (± 114.11), PaCO 2 42.78 mm Hg (± 10.84); after the first apnea test: pH 7.11(± 0.08), PaO 2 208.39 mm Hg (± 112), PaCO 2 82.43 mm Hg (± 16.91); before the second test: pH 7.33 (± 0.09), PaO 2 253.56 mm Hg (± 105.36), PaCO 2 43.76 mm Hg (± 9.67); following the second apnea test: pH 7.11 (± 0.10), PaO 2 200.1 mm Hg (± 116.45), PaCO 2 84.98 mm Hg (± 20.21). The pH, PaO 2 , and PaCO 2 values before and after the first and second apnea tests have shown statistically significant differences (P < 0.0001). Conclusions: The apnea test was safe, blood gas test results are similar to those described in the literature, severe hypoxemias were prevented by a quick reconnection to the mechanical ventilation; and marked hypercapnia and acidemia following the apnea test were found, but no test was invalidated. J Neurol Res. 2021;11(1-2):14-19 doi: https://doi.org/10.14740/jnr646
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".