Apnea TestPresentad by :Hawra Owiwi

Outline

Apnea The apnea testApnea producerApnea test interpretationsancillary tests

Apnea

is a term for suspension of external breathing .

Causes of apnea

1- can be voluntarily achieved 2- drug-induced 3- mechanically induced4- neurological disease 5- trauma

types of Apnea

There are three types of apnea:1. obstructive2. central3. mixed

Complications

The apnea test

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

Recommended patients : severe brain injury (large size intracranial hemorrhage,

massive stroke , diffuse brain edema with absent basal fissures and sulci , multiple hemorrhagic contusions )

Before Test :

1- ComaThe depth of coma is usually examined

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

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

The apnea test This procedure is based on disconnection

of the ventilator

Preconditions

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

3- Positive fluid balance

4- Normal PCO2 (Arterial PCO2 of 35-45 mm Hg)

5- Preoxygenate with 100% O2 for 30 minutes recommend maintenance of a normal PO2 or

preoxygenation to obtain an arterial PO2 ≥ 200

6- medication such as pancuronium

Test : 1- Connect a pulse oximeter and disconnect the

ventilator

techniques for ascertaining that there is sufficient oxygenation during ATinsert a catheter or cannulanot disconnected from the respiratorBIPAPcontinuous flow of 100 % oxygen and low (PEEP)

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

3- Measure PO2, PCO2, and pH after 10

minutes and reconnect the ventilator

Positive or negativebrain 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

Duration of the apnea testApnea 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)

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

Monitoring

Contraindicationhemodynamic 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

Complicationssevere hypotension pneumothorax excessive hypercarbia hypoxia, acidosis cardiac arrhythmia or asystole

Is the apnea test safe in BD diagnosis?

ancillary tests cerebral blood flow by transcranial Doppler

studies CT angiography multimodality evoked potential studies atropine test

Video

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]

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