Index: suite_leahi/tst_blood_prime/test.py
===================================================================
diff -u -r535c5a49b6d814e8531fa43fc816f0658d1bafef -rbb0ea45aa227631363b51145e918c5f1d446918e
--- suite_leahi/tst_blood_prime/test.py	(.../test.py)	(revision 535c5a49b6d814e8531fa43fc816f0658d1bafef)
+++ suite_leahi/tst_blood_prime/test.py	(.../test.py)	(revision bb0ea45aa227631363b51145e918c5f1d446918e)
@@ -13,14 +13,15 @@
 
 
 import names, re
-from configuration                import utility, config
-from leahi_dialin.ui              import utils
-from leahi_dialin.ui.td_messaging import TD_Messaging
-from leahi_dialin.common.td_defs  import TDOpModes, TDTreatmentStates
-from leahi_dialin.common.ui_defs  import TXStates
-from leahi_dialin.common.msg_defs import MsgIds, MsgFieldPositions
-from leahi_dialin.protocols       import CAN
-from leahi_dialin.utils           import conversions
+from configuration                  import utility, config
+from leahi_dialin.ui                import utils
+from leahi_dialin.ui.td_messaging   import TD_Messaging
+from leahi_dialin.common.td_defs    import TDOpModes, TDTreatmentStates
+from leahi_dialin.common.ui_defs    import TXStates
+from leahi_dialin.common.msg_ids    import MsgIds
+from leahi_dialin.common.constants  import MSG_HEADER_SIZE
+from leahi_dialin.protocols         import CAN
+from leahi_dialin.utils             import conversions
 
 td_simulator            = TD_Messaging()
 can_interface           = td_simulator.can_interface
@@ -44,7 +45,7 @@
     @return: None
     """
     message = message["message"]
-    index = MsgFieldPositions.START_POS_FIELD_1
+    index = MSG_HEADER_SIZE
 
     state, index = conversions.bytearray_to_integer(message, index)
     global salineBolusStartState
@@ -446,7 +447,7 @@
     @return: None
     """
     message = message["message"]
-    index = MsgFieldPositions.START_POS_FIELD_1
+    index = MSG_HEADER_SIZE
 
     state, index = conversions.bytearray_to_integer(message, index)
     global bloodFlowrate
@@ -459,7 +460,7 @@
     @return: None
     """
     message = message["message"]
-    index = MsgFieldPositions.START_POS_FIELD_1
+    index = MSG_HEADER_SIZE
 
     state, index = conversions.bytearray_to_integer(message, index)
     global bloodPrimeState
Index: suite_leahi/tst_end_of_treatment/test.py
===================================================================
diff -u -r535c5a49b6d814e8531fa43fc816f0658d1bafef -rbb0ea45aa227631363b51145e918c5f1d446918e
--- suite_leahi/tst_end_of_treatment/test.py	(.../test.py)	(revision 535c5a49b6d814e8531fa43fc816f0658d1bafef)
+++ suite_leahi/tst_end_of_treatment/test.py	(.../test.py)	(revision bb0ea45aa227631363b51145e918c5f1d446918e)
@@ -24,12 +24,13 @@
 
 import names
 import can
-from leahi_dialin.ui              import utils
-from leahi_dialin.common.msg_defs import MsgIds, MsgFieldPositions
-from leahi_dialin.ui.td_messaging import TD_Messaging
-from configuration                import utility, config
-from leahi_dialin.common.td_defs  import TDOpModes,TDTreatmentStates
-from leahi_dialin.protocols       import CAN
+from leahi_dialin.ui                import utils
+from leahi_dialin.common.msg_ids    import MsgIds
+from leahi_dialin.common.constants  import MSG_HEADER_SIZE
+from leahi_dialin.ui.td_messaging   import TD_Messaging
+from configuration                  import utility, config
+from leahi_dialin.common.td_defs    import TDOpModes,TDTreatmentStates
+from leahi_dialin.protocols         import CAN
 td =TD_Messaging()
 
 endTreatmentState = "-1"
@@ -91,7 +92,7 @@
     @return: None
     """
     message = message['message']
-    index = MsgFieldPositions.START_POS_FIELD_1
+    index = MSG_HEADER_SIZE
     state,index = conversions.bytearray_to_integer( message, index)
     global endTreatmentState
     endTreatmentState = str(state)
Index: suite_leahi/tst_main_treatment/test.py
===================================================================
diff -u -r535c5a49b6d814e8531fa43fc816f0658d1bafef -rbb0ea45aa227631363b51145e918c5f1d446918e
--- suite_leahi/tst_main_treatment/test.py	(.../test.py)	(revision 535c5a49b6d814e8531fa43fc816f0658d1bafef)
+++ suite_leahi/tst_main_treatment/test.py	(.../test.py)	(revision bb0ea45aa227631363b51145e918c5f1d446918e)
@@ -26,7 +26,8 @@
 from configuration                import utility, config
 from leahi_dialin.common.td_defs  import TDOpModes,TDTreatmentStates
 from leahi_dialin.common.ui_defs  import TXStates
-from leahi_dialin.common.msg_defs import MsgIds, MsgFieldPositions
+from leahi_dialin.common.msg_ids    import MsgIds
+from leahi_dialin.common.constants  import MSG_HEADER_SIZE
 from leahi_dialin.utils           import conversions
 from leahi_dialin.protocols       import CAN
 
@@ -59,7 +60,7 @@
     @return: None
     """
     message = message["message"]
-    index = MsgFieldPositions.START_POS_FIELD_1
+    index = MSG_HEADER_SIZE
 
     state, index = conversions.bytearray_to_integer(message, index)
     global newTreatmentDuration