The apnea test is a clinical procedure for assessing brainstem function, carried out when irreversible loss of brain function is suspected. The ventilation of the patient is paused under control; at the same time, oxygen supply is maintained via apneic oxygenation. If the arterial partial pressure of carbon dioxide (PaCO₂) rises to at least 60 mmHg without a respiratory response setting in, the brainstem respiratory center is taken to have failed.
The test belongs to the standard repertoire of brain death diagnostics according to the German Medical Association (BÄK) guideline (5th revision 2022) and the World Brain Death Project (Greer et al., JAMA 324, 2020, pp. 1078–1097).
A special constellation: ECMO
Under extracorporeal membrane oxygenation (ECMO), the apnea test is especially demanding, because the rise in CO₂ can be compensated by the ECMO device. The BÄK guideline 2022 contains a specific clarification on this: the gas flow rate of the ECMO device must be reduced under control during the test in order to permit the physiological rise in CO₂.
Confounders
The apnea test is valid only if metabolic and toxic confounders are excluded: severe hypothermia, sedation with hypnotics or opioids, severe electrolyte disturbances. Otherwise a false-positive finding threatens.
Substance-ontological classification
The apnea test is an irreversibility diagnostic procedure — it yields a medically diagnosed irreversibility, not the ontological irreversibility of the separation of body and spiritual substance. Even a comprehensive clinical and instrumental brain death diagnosis proves only that function does not return — it does not prove that the person as such has ceased to be.
International criticism of the apnea test
The apnea test stands internationally under broad medical, ethical, and philosophical criticism. The main lines are summarized in what follows.
Clinical criticism: risks, iatrogenesis, confounders
Clinical observational studies document considerable hemodynamic complications during the apnea test: hypotension, hypoxemia, acidosis, arrhythmias (Saposnik et al. 2000). Mechanistically, acidemia, auto-PEEP, and a drop in preload are held responsible.
Severe individual events are documented: tension pneumothorax and pneumomediastinum through catheter-based insufflation (Bar-Joseph et al. 1998 in Anesthesiology; Saposnik et al. 2000 in Neurology).
Iatrogenic worsening of brain injury: Joffe, Anton and Duff (2010) as well as Truog and Tasker (2017) argue that the test-induced hypercapnia and hypoxemia further raise intracranial pressure via cerebral vasodilation. Truog and Tasker speak of the test as a possible coup de grâce in the pathogenesis of brain death.
Underspecified confounders: Joffe et al. emphasize that standard confounder lists (hypothermia, sedation, electrolytes) underestimate central confounding factors — high cervical spinal cord lesions, central adrenal or thyroid failure, residual sedative levels in liver or kidney insufficiency, and chronic CO₂ retention.
Methodological criticism: self-fulfillment, circularity, validation problem
Self-fulfilling prophecy. Truog and Robinson (2003), Truog and Tasker (2017): the test checks whether respiratory function returns by producing conditions (hypercapnia, hypoxemia, hypotension) that themselves endanger this return. The diagnosis is thereby partly constituted by the diagnostics.
Validation problem. Verheijde, Rady and Potts (2009, 2018) and Tibballs (2010): there is no independent gold standard against which the apnea test would be validated; different guidelines require different PaCO₂ thresholds (50 versus 60 mmHg). D. Alan Shewmon (2021) has documented that spontaneous breathing in individual cases set in only at PaCO₂ of 71, 77, 91, and even 112 mmHg — beyond all common thresholds.
Legal-ethical criticism: consent, duty, transplantation pressure
Consent as a battery question. Truog and Tasker (2017), Berkowitz and Garrett (2020), Joffe (2020), Pope (repeatedly): since the apnea test has no therapeutic benefit for the patient but serves solely to issue a death certificate, and since it carries non-trivial risks, it requires, under classical informed-consent law, disclosure and consent. Without consent, in the common-law sense, battery (unlawful bodily harm) potentially obtains.
Counterposition. Lewis and Greer (2017, 2023) as well as the World Brain Death Project (Greer et al. 2020): diagnostic tests for the determination of death require — analogously to stethoscopy in cardiovascular death — no separate consent.
Inconsistent legal situation in the USA. Pope documents: consent was required in court cases in Montana and Kansas, not in Virginia and Nevada; Nevada amended its UDDA counterpart in 2017 (cf. Pope 2018).
Transplantation pressure. Verheijde and Rady (2009): the test is carried out in temporal and organizational connection with donor preparation — the threshold to iatrogenesis is ethically aggravated by the proximity to organ retrieval.
Ontological-philosophical criticism
Hans Jonas (1974): classical early criticism of the brain death concept as a “revenant” of body-soul dualism. The apnea test appears as a symptom of this dualism, because it reduces the holistic organism to a reflex brainstem function.
D. Alan Shewmon (1998, 2001, 2021): on the basis of chronically ventilated patients diagnosed with brain death (his case “TK,” surviving over 20 years), he demonstrates that somatic integration is possible without brain function. From this it follows for the apnea test: an absent respiratory response does not establish the death of the organism, but only a partial functional failure. The loss of a function is not the loss of the substance.
Ari Joffe (2010, 2020): the apnea test is “contraindicated, has no diagnostic value, and produces a self-fulfilling prognosis” — even with consent ethically indefensible, because it destroys the very function to be assessed.
Verheijde and Rady (2009, 2018): brain death is no biologically well-founded substance boundary; the apnea test is “scientifically flawed and burdened with the hypothesis of causing brain death itself,” with reference to the US President’s Council on Bioethics (2008).
Hypothalamus argument (Nair-Collins, Joffe, Shewmon 2023): persistent neurosecretory hypothalamic function (no diabetes insipidus, intact ADH secretion) is documented in a relevant proportion of patients diagnosed with brain death. The constitutive connection to the apnea-test criticism: if the hypothalamus continues to perform organismic regulation, then the apnea test — which assesses only brainstem respiratory centers — cannot answer the question “is the organism as a whole dead?” at all.
International variation
United Kingdom (brainstem-death concept): the Academy of Medical Royal Colleges (Code of Practice 2008) bases the diagnosis exclusively on the clinical brainstem examination plus apnea test; confirmatory tests are not obligatory. The apnea test thereby carries greater relative weight than in the USA.
Japan (Organ Transplantation Act 1997, amended 2010): brain death criteria apply only in the donation context, not generally as death. The apnea test is performed only after a flat EEG and auditory brainstem potentials, plus a second examination after at least 6 hours in adults, 24 hours in children (cf. Wijdicks 2002 and Greer et al. 2020 for the international overview).
Sweden / Scandinavia: since 1988 Sweden requires either two clinical examinations with an apnea test or cerebral angiography as a confirmatory test; the apnea test is substitutable. Norway relies on cerebral angiography as an obligatory confirmatory procedure (Wijdicks 2002).
ECMO patients worldwide: in a considerable proportion the apnea test is not carried out, owing to CO₂ elimination by the oxygenator; substitute strategies (reduction of the sweep-flow rate, exogenous CO₂ supply) are not standardized. The German BÄK guideline 2022 contains a specific clarification on this (reduction of the gas flow rate during the test).
Assessment in the light of the precautionary principle
The collection of criticisms shows what makes Benedict XVI’s precautionary principle (2008) clinically operationalizable: where a diagnostic procedure is methodologically circular, can do non-trivial clinical harm, pursues no therapeutic aim, and is handled inconsistently internationally, the assumption that the donor is still alive is the legally secure and morally appropriate position — until certainty is reached.
Ontological classification
Superclass: Irreversibility Diagnostic Procedure
Connected with: Brain-Based Criterion of Death, Irreversible Loss of Brain Function, Mechanical Life Support
Sources
Clinical and guideline-based foundations
- Greer, David M. et al. (2020): Determination of Brain Death/Death by Neurologic Criteria. The World Brain Death Project. JAMA 324(11): 1078–1097.
- Bundesärztekammer (2022): Richtlinie zur Feststellung des irreversiblen Hirnfunktionsausfalls — 5. Fortschreibung (with clarification of the apnea test under ECMO).
- Wijdicks, Eelco F. M. (2002): Brain death worldwide: accepted fact but no global consensus in diagnostic criteria. Neurology 58(1): 20–25.
Clinical complication studies
- Saposnik, Gustavo; Bueri, Julián A.; Mauriño, Jorge et al. (2000): Complications during apnea testing in the determination of brain death. Neurology 55(7): 1045–1048.
- Bar-Joseph, Gad; Bar-Lavie, Yaron; Zonis, Zinaida (1998): Tension pneumothorax during apnea testing for the determination of brain death. Anesthesiology 89(5): 1250–1251.
Methodological and ethical criticism
- Joffe, Ari R.; Anton, Natalie R.; Duff, Jonathan P. (2010): The Apnea Test: Rationale, Confounders, and Criticism. Journal of Child Neurology 25(11): 1435–1443.
- Joffe, Ari R. (2020): Apnea Testing Is Medical Treatment Requiring Informed Consent. American Journal of Bioethics 20(6): 42–44.
- Truog, Robert D.; Robinson, Walter M. (2003): Role of brain death and the dead-donor rule in the ethics of organ transplantation. Critical Care Medicine 31(9): 2391–2396.
- Truog, Robert D.; Tasker, Robert C. (2017): Counterpoint: Should Informed Consent Be Required for Apnea Testing in Patients With Suspected Brain Death? Yes. CHEST 152(4): 702–704.
- Lewis, Ariane; Greer, David (2017): POINT: Should Informed Consent Be Required for Apnea Testing in Patients With Suspected Brain Death? No. CHEST 152(4): 700–702.
- Lewis, Ariane; Greer, David (2023): Should the Brain Death Exam With Apnea Test Require Surrogate Informed Consent? No. Neurology (UDDA Revision Series).
- Berkowitz, Ilya; Garrett, Jeremy R. (2020): Legal and Ethical Considerations for Requiring Consent for Apnea Testing in Brain Death Determination. American Journal of Bioethics 20(6): 4–16.
- Tibballs, James (2010): A Critique of the Apneic Oxygenation Test for the Diagnosis of “Brain Death”. Pediatric Critical Care Medicine 11(4): 475–478.
Substance-ontological and philosophical criticism
- Jonas, Hans (1974): Against the Stream: Comments on the Definition and Redefinition of Death. In: Philosophical Essays: From Ancient Creed to Technological Man. Englewood Cliffs: Prentice-Hall.
- Shewmon, D. Alan (2001): The brain and somatic integration: insights into the standard biological rationale for equating “brain death” with death. Journal of Medicine and Philosophy 26(5): 457–478.
- Shewmon, D. Alan (2021): Statement in Support of Revising the Uniform Determination of Death Act and in Opposition to a Proposed Revision. Journal of Medicine and Philosophy 48(5): 453–477. (107 co-signatories.)
- Verheijde, Joseph L.; Rady, Mohamed Y.; Potts, Michael (2018): Neuroscience and Brain Death Controversies: The Elephant in the Room. Journal of Religion and Health 57(5): 1745–1763.
- Verheijde, Joseph L.; Rady, Mohamed Y.; McGregor, Joan L. (2009): Brain death, states of impaired consciousness, and physician-assisted death for end-of-life organ donation and transplantation. Medicine, Health Care and Philosophy 12(4): 409–421.
- Nair-Collins, Michael; Joffe, Ari R. (2023): Frequent Preservation of Neurologic Function in Brain Death and Brainstem Death. AJOB Neuroscience 14(3): 255–268.
- President’s Council on Bioethics (2008): Controversies in the Determination of Death: A White Paper. Washington, D.C.
Generated by querying the Personhood ontology.