Apnea test by Hawra Owiwi

Apnea test is a procedure done on the ICU to confirm a brain death case. This test has to be performed by a qualified respiratory therapist with good ability to perform arterial blood gases.

1. Apnea Test
Presentad by :
Hawra Owiwi

2. Outline
 Apnea
The apnea test
Apnea producer
Apnea test interpretations
ancillary tests

3. Apnea
is a term for suspension of external breathing .

4. Causes of apnea
1- can be voluntarily achieved
2- drug-induced
3- mechanically induced
4- neurological disease
5- trauma

5. types of Apnea
There are three types of apnea:
1. obstructive
2. central
3. mixed

6. 
Complications

7. The apnea test

8. The apnea test is an examination for determining
brain death (BD)

9. Recommended patients :

severe brain injury
(large size intracranial hemorrhage, massive
stroke , diffuse brain edema with absent basal
fissures and sulci , multiple hemorrhagic
contusions )

10. Before Test :
1- Coma
The depth of coma is usually examined

11. 2- Absence of brain stem reflexes
pupils are examined
(pupils that are between 4-6 mm in size )
examination of facial sensation and facial motor
response , The jaw reflex , The oculocephalic reflex

12. The bulbar function is best tested by examining cough
response to bronchial suctioning.
A catheter should be inserted into the trachea
If these brain stem reflexes are absent, can proceed
with the apnea test

13. The apnea test
This procedure is based on disconnection
of the ventilator
Preconditions

14. Prerequisites
1- Core Temperature 36.5°C or 97°F
Correction of hypothermia facilitates CO2 production
and reduces the chances of hypotension

2- Systolic blood pressure 90 mm Hg

15. 3- Positive fluid balance
4- Normal PCO2 (Arterial PCO2 of 35-45 mm Hg)
5- Preoxygenate with 100% O
2
for 30 minutes
recommend maintenance of a normal PO2 or
preoxygenation to obtain an arterial PO2 ≥ 200
6- medication
such as pancuronium

16. Test :
1- Connect a pulse oximeter and disconnect the ventilator
techniques for ascertaining that there is sufficient
oxygenation during AT
insert a catheter or cannula
not disconnected from the respirator
BIPAP
continuous flow of 100 % oxygen and low (PEEP)

17. 2- Look closely for respiratory movements (abdominal
or chest excursions that produce adequate tidal
volumes)

3- Measure PO
2
, PCO
2
, and pH after 10 minutes and
reconnect the ventilator

18. Positive or negative
brain death indeterminate result
respiratory movements are
absent
arterial PCO2 is 60 mm Hg
(option: 20 mm Hg increase
in PCO2 over a baseline
normal PCO2)

the apnea test is positive

respiratory movements are
detected
If the PCO2 is < 60 mm Hg or
PCO2 increase is < 20 mm Hg
over baseline normal PCO2
the result is indeterminate and
an additional confirmatory test
can be considered

19. Duration of the apnea test
Apnea is concluded when no breathing effort is
observed at a PaCO2 of 60 mm Hg or with a 20 mm Hg
increment from baseline
if respiratory movements are detected, the AT is
classified as negative (i.e., not supportive of a BD
diagnosis)

20. Duration of the apnea test
arterial pressure drops to < 90 mm Hg
desaturation
cardiac arrhythmias

recommended that the test be stopped after 10–15 min,
even if blood gas levels cannot be determined

21.  Monitoring

22. Contraindication
hemodynamic instability
poor PaO2
inability to achieve target PaCO2 levels
Extensive thoracic trauma
presence of some pathologic condition
significant pulmonary disorders interfering with
ventilation are other conditions that may prevent the
use of the AT

23. Complications
severe hypotension
pneumothorax
excessive hypercarbia
hypoxia, acidosis
cardiac arrhythmia or asystole

24. Is the apnea test safe in BD diagnosis?

25. ancillary tests
cerebral blood flow by transcranial Doppler studies
CT angiography
multimodality evoked potential studies
atropine test

26. Video

27. References
1. Determination of brain death in children: A medical center experience. [PubMed]
2. SPECT in the diagnosis of brain death in children. [PubMed]
3. Ashwal S. Clinical diagnosis and confirmatory testing of brain death in children
4. Variability in brain death determination practices in children
5Apnea testing in suspected brain dead children-physiological and mathematical
modelling.. [PubMed]
6. A. Apnea documentation for determination of brain death in Thai children. J Med.
[PubMed]

28. Thank you