Norm of Hyperventilation
No elevation in ST segment of ECG.
Usage of Hyperventilation
Provocative noninvasive diagnostic study used to identify coronary vasospasm as a causal agent in clients with variant angina and as an adjuvant test for epilepsy.
Positive of Hyperventilation
The hyperventilation test is positive when one of the following conditions is present on the ECG: ST-segment elevation ≥0.2 mV in two leads of the ECG during or after the test; ST-segment depression ≥0.1 mV in two leads after the completion of the test; inverted U wave not present on the baseline ECG; variant angina.
Description of Hyperventilation
Hyperventilation causes cellular alkalosis, which in turn promotes movement of calcium ions intracellularly, which leads to an increase in the tone of vascular smooth muscle in the coronary vasculature. The intent of this study is to induce vasoconstriction in the coronary arteries to determine alterations in myocardial tissue perfusion and oxygenation demonstrated on the ECG. Hyperventilation can facilitate induction of supraventricular tachycardia (SVT).
Professional Considerations of Hyperventilation
Consent form IS required.
- Test is best performed during the early morning hours between 0600 and 0800.
- Vasodilators should not be administered 24–48 hours before the test.
- Perform baseline ECG.
- Have client perform respirations of 35–40 breaths per minute × 6 minutes.
- Arterial blood gas measurement should be completed at the end of the test to confirm an adequate alkalotic state (pH ≥7.55).
- Encourage client to rest after procedure.
Client and Family Teaching
- Obtain a medical history before the test. Clients who have a history of pulmonary disease may be adversely affected or unable to tolerate the test and should be excluded.
- Inform client to hold vasoactive medications before test.
- Encourage client to verbalize any discomfort throughout and after the test.
- Chest pain or ECG changes may not occur until completion of the 6 minutes of hyperventilation.
- Dysrhythmias may occur, most commonly in test-positive clients.
Factors That Affect Results
- Test becomes negative after abciximab administration.
- Calcium-channel blockers may be prescribed for clients having a positive hyperventilation test. Beta-adrenergic blockers should not be prescribed for clients having a positive hyperventilation test.