Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Example input: Abstract: Some patients converted from ventricular fibrillation to organized rhythms by defibrillation - trained ambulance technicians(EMT - Ds) will refibrillate before hospital arrival.The authors analyzed 271 cases of ventricular fibrillation managed by EMT - Ds working without paramedic back - up.Of 111 patients initially converted to organized rhythms, 19(17 % ) refibrillated, 11(58 % ) of whom were reconverted to perfusing rhythms, including nine of 11(82 % ) who had spontaneous pulses prior to refibrillation.Among patients initially converted to organized rhythms, hospital admission rates were lower for patients who refibrillated than for patients who did not(53 % versus 76 % , P = NS), although discharge rates were virtually identical(37 % and 35 % , respectively).Scene - to - hospital transport times were not predictively associated with either the frequency of refibrillation or patient outcome.Defibrillation - trained EMTs can effectively manage refibrillation with additional shocks and are not at a significant disadvantage when paramedic back - up is not available.
Example output: Ventricular Fibrillation
Example explanation: This term is directly present in the abstract and it is one of the main topic in it. So can be chosen as the medical subject heading.
Q: Abstract: Transit times of radiopaque markers through the human gut were measured by published techniques and compared with a simplified method. Three sets of distinctive markers were ingested by 24 healthy persons on 3 successive days. In the first part of the study, daily abdominal x-rays were taken and individual stools were collected for radiography. Mouth-to-anus transits were assessed from the fecal output of markers and mean colonic and segmental colonic transits were calculated from the daily radiographs. These established methods were then compared with estimates of total colonic and segmental transits based on a single abdominal film, taken on the fourth day. The single-film technique correlated well with values obtained from the previous, but more inconvenient, methods. Using the simpler approach, colonic transit was assessed in 49 additional healthy subjects, for a total group of 73. Total colonic transit was 35.0 +/- 2.1 h (mean +/- SE); segmental transits was 11.3 +/- 1.1 h for the right colon, 11.4 +/- 1.4 h for the left colon, and 12.4 +/- 1.1 h for the rectosigmoid. Men had significantly shorter transits for the whole colon than did women (p less than 0.05), and this difference was apparent to some extent in the right (p = 0.06) and left colon (p = 0.07) but not in the rectosigmoid. Age did not influence transit significantly nor did a small dose of supplemental fiber. The technique is simple, convenient for clinical usage, and reduces the exposure to radiation to acceptable levels. There should be a role for this approach in the evaluation of colonic transit in selected patients.
A:
Adult