The New Testament reveals that "the LORD" spoken of here is Jesus Christ. Paul applies verse 23 to Jesus.
Romans 14:When the Bible says that Jesus is Lord it is saying that he is the LORD God. To confess Jesus as the LORD is necessary to be saved. "if you confess with your mouth, "Jesus is LORD," and believe in your heart that God raised him from the dead, you will be saved." Rom 10:9
8 If we live, we live to the Lord; and if we die, we die to the Lord. So, whether we live or die, we belong to the Lord.
9 For this very reason, Christ died and returned to life so that he might be the Lord of both the dead and the living.
10 You, then, why do you judge your brother? Or why do you look down on your brother? For we will all stand before God’s judgment seat.
11 It is written: "‘As surely as I live,’ says the Lord, ‘every knee will bow before me; every tongue will confess to God.’" (Is 45;23) (Septuagint)
While it may appear that verse 11 is slightly different than Isaiah 43:13 quoted above as it ends with "to God", in fact it is exactly the same word for word as the Septuagint version. The New Testament writers consistently used the Septuagint over the Masoretic text when quoting the Old Testament.
There is no God apart from the LORD Jesus Christ. Jesus Christ is the body of God - God's outward manifestation. To bow to Jesus is to bow to God. There is no Savior apart from the LORD Jesus Christ. He is our righteousness, holiness and redemption.