My presumption is that you are speaking of the language barrier between international nurse and local patient:
Patient safety issues can be subdivided into two main groups: Firstly, planned patient safety procedures or activities and secondly, emergency patient safety procedures activities. Planned patient safety measures include routine Risk Assessment e.g. Waterlow Scale, VTE Risk Assessment, MRSA screening and so on. In these cases, language barriers caused by lack of knowledge of relevant vocab or medical terminology can be minimised by pre-teaching and practice off-site. This is especially important where Risk Management tools are unfamiliar.
Emergency Patient safety procedures are not as easy to prepare for and are especially difficult as there is often limited time to think of correct responses and, in addition, stress levels are high. Because of this, practice (e.g. rehearsal of simulated situations) of possible scenarios is very important. Patients who are unable to understand instructions in a crisis situation because of a language barrier are likely to become more distressed and less compliant. In these cases ,patient safety may be compromised.