What I mean is something like this (I do not know whether this will work / this is probably not corrrect or not the best way to do it, but maybe it better illustrates what I want to achieve)
$sql1 = "SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED";
$sql2 = "SELECT * FROM sometable";
$sql3 = "COMMIT";
$connection = $this->db;
$connection->query($sql1);
$data = $connection->query($sql2);
$connection->query($sql3);
$data->setFetchMode(\Phalcon\Db::FETCH_ASSOC);
$results = $data->fetchAll();