"The doctor is saving the patient."
Translation:SID toDtaH Qel.
-taH refers to the action as something that is currently ongoing without any reference to when it started or when it will end, but it is definitely going on during the time frame being discussed. So the sentence given here says that the doctor is working right now on saving the patient, but does not indicate if or when that will stop.
-lI' is very similar, but adds a small amount of information about the end of the action. It states that there is a definite and known end and the action is getting things closer to that end point. Using -lI' would have implied that there is a way to know when the saving will have been accomplished and that the current saving is moving towards that point.
Most of the time -lI' would be appropriate for a sentence like this, but there are situations where it might be hard for a doctor to tell if his efforts are even helping or when he'll be able to stop and -lI' would probably not be appropriate in that kind of situation.
SID toDtaH Qel and SID toDlI' Qel express the idea that the doctor is in the middle of an ongoing procedure. SID toD Qel can be used to describe the doctor in the moment of saving a patient, without reference to it being an ongoing activity (even if it's not instantaneous), or it can be used to describe a general truth about doctors saving patients (a doctor saves a patient; that's what they do).
Don't think of the aspect suffixes as being used to define how long an action objectively takes. They allow the speaker to express different... er... aspects of a situation. The same event can be described many different ways depending on the context.
SID toD Qel The doctor saves the patient.
Said in the middle of an unfolding story that puts you right in the action. "The orderly rushes the patient into the operating room. The nurse declares that the patient's heart has stopped. Then the doctor, in a miraculous feat of medical skill, saves the patient. When the patient wakes up, he looks into the doctor's eyes and thanks him."
SID toDtaH Qel The doctor is saving the patient.
Said to focus on a particular moment in the middle of an ongoing event. "Don't worry, kid. He'll come out of this all right. Even now, the doctor is saving the patient." SID toDlI' Qel is the progressing-toward-an-endpoint version of this.
SID toDpu' Qel The doctor saved the patient.
Said after the fact, to describe the event as a completed whole. "Nurse Janice, how did it go?" "The doctor saved the patient." SID toDta' Qel is the set-out-to-accomplish-and-did-it version of this.
And all of these could be used of past or future events. SID toD Qel The doctor saved patients (it was his job in the past); The doctor will save the patient; SID toDtaH Qel The doctor was saving the patient (in a past moment, which was in the middle of the ongoing procedure); The doctor will be saving the patient (focusing on a moment in the future in which the procedure is ongoing); SID toDpu' Qel The doctor had saved the patient (when describing a past event, someone refers to something that had already been completed); The doctor will have saved the patient (looking forward to a time after the procedure that is anticipated to be successful).