Given the task definition, example input & output, solve the new input case.
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: 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.
Output: Ventricular Fibrillation
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.

New input case for you: Abstract: Slowly adapting pulmonary stretch receptors have been hypothesized to be the afferents mediating the vagally dependent, volume-related prolongation of expiratory time (TE) during expiratory loading. It has been further suggested that the vagal component of this prolongation of TE is due to the temporal summation of pulmonary stretch receptor (PSR) activity during expiratory loading. This hypothesis was tested in rabbits exposed to resistive and elastic single-breath expiratory loading while PSR's were simultaneously recorded. Both types of loads resulted in a decreased expired volume (VE) and increased expiratory duration (TE). The TE for resistive loads were significantly greater than for elastic loads for equivalent VE. Thus two different VE-TE relationships were found for resistive and elastic loads. When TE was plotted against the area under the expired volume trajectory, a single linear relationship was observed. PSR activity recorded during expiratory loading increased as VE decreased and TE increased. A single linear relationship resulted when the number of PSR spikes during the expiration was plotted against the associated TE for all types of loads. These findings demonstrate that the volume-related prolongation of TE with single-breath expiratory loads is associated with an increase in PSR discharge. These results support the hypothesis that the vagal component of load-dependent prolongation of TE is a function of both the temporal and spatial summation of PSR activity during the expiratory phase.
Output:
Action Potentials