Arterial blood gas analysis
Arterial blood gas (ABG) does not replace physical diagnosis nor should treatment be delayed while awaiting results if symptomatic pneumothorax is suspected. However, ABG analysis may be useful in evaluating hypoxia, hypercarbia, and respiratory acidosis.
Electrocardiography
In left-sided pneumothorax electrocardiogram (ECG) shows: rightward shift of the frontal QRS axis, diminution of the precordial R voltage, decrease in QRS amplitude, and precordial T-wave inversion. With right pneumothorax ECG may show diminution of the precordial QRS voltage, right axis deviation, and a prominent R wave in V2 with associated loss of S wave voltage, mimicking posterior myocardial infarction. All these changes are thought to be due to mechanical effects and should not be taken for cardiac ischemia or infarction.