Arterial blood-gas (ABG) measurements are the gold standard to evaluate pulmonary gas exchange. However, arterial punctures are more painful than venous punctures and, in ICU patients, cause greater anxiety than tracheal aspiration. The only technique that has been shown to effectively reduce pain during arterial punctures is the subcutaneous injection of lidocaine. However, this technique is more time consuming and is poorly used.

Topical anesthesia is widely used during arterial punctures despite the lack of proof of efficacy.

While performing arterial punctures with small gauge needles is feasible, to the best of the investigators knowledge no studies have assessed the effect of needle gauge on arterial puncture related pain.

The aim of the present study was to compare the pain experienced during arterial punctures performed with a 25 G or 23 G needle. The secondary endpoints were the characterization of the pain and the anxiety associated with the arterial punctures.

Inclusion Criteria:

• patients who had a planned assessment of arterial blood gas in our Respiratory Department

Exclusion Criteria:

• under the age of 18
• inability to provide consent
• the presence of a contraindication to arterial punctures based on the American Association of Respiratory Care Guidelines