Experimental design and procedures: This prospective experimental study will be completed in one study visit taking between 1 and 3 hours. Verbal and written informed consent will be obtained by qualified members of the investigative team. Following informed consent, all participants will complete a health history questionnaire to assess inclusion/exclusion criteria. For patients with PD the consenting investigator will review the electronic medical record to ensure inclusion/exclusion criteria are met.
The experimental protocol will consist of 1.) Baseline pulmonary function measures, 2.) Baseline measures of depression and apathy, 3.) Presentation of resistive inspiratory loads via respiratory equipment, and 4.) Rating the perceived magnitude of respiratory sensations as measured on a modified Borg scale (ranging from 6 - no breathing difficulty - to 20 - maximal difficulty). For patients with PD only, the investigators will also review results of the rehabilitation barium swallow study performed as part of their standard clinical care.
Baseline Pulmonary function measures: The forced expired volume in the first second (FEV1) of a forced vital capacity (FVC) exhalation will be measured for each participant. Maximum inspiratory pressure (PiMax) will be measured with a manometer. The PiMax test will be repeated until 3 measurements within 10% variation are obtained, with at least 1 minute rest between trials.
Baseline depression and apathy: There is a significant impact for emotion on respiratory perceptual ratings. As such, we will measure baseline depression and apathy scores using 2 validated scales, the Beck Depression Index (BDI) and Marin Apathy Index (MAI). These are not outcome measures, but will be used to determine exclusion criteria.
Should depression (17 or greater on BDI) be detected in a participant, that participant will be provided with contact information for the University of Florida (UF) psychiatry and psychology clinic and encouraged to seek further evaluation. In the case severe depression is detected (31 or greater on BDI) the participant will not continue with the study, and will be provided with contact information for the UF psychiatry and psychology clinic and encouraged to seek further evaluation.
Inspiratory resistive load presentation:
The participant will be seated in a chair, separated from the investigator and experimental apparatus. The participant will be instructed to "relax and breathe" through a facemask connected to a non-rebreathing valve in line with a differential pressure transducer. The inspiratory port of the valve will be connected to the resistive loading manifold. The manifold consists of 5 differential resistors ranging from 5 - 40 centimeters/water (cmH2O) of resistive pressure, separated by stoppered ports, as well as a no load condition. The load is applied by removing the stop for an entire inspiratory breath, and then replacing the port to continue resting tidal breathing. The pressure transducer will provide measures of mouth pressure and airflow, which will be digitized and recorded to a desk top computer using LabChart software. Following each loaded breath, the participant will provide an estimate of the perceived difficulty of breathing using a modified Borg scale.
Participants will be familiarized with the loads in a practice session prior to initiating the experimental protocol. During the experimental session, participants will listen to music of their choice in order to mask experimental sounds. The resistive loads will be applied in a randomized block design, with each loaded breath separated by at least three unloaded breaths. Two blocks will be completed with each load presented between 3 and 5 times within each block. Therefore, there will be a total of between 15 and 25 loaded breaths (3-5 loads x 5 presentations) per block. Participants will be instructed that when they see a small light flash briefly on the table in front of them (which they will be familiarized with prior to beginning the experiment) a resistive load will be applied to the next breath. Following the loaded breath, the participant will be asked to estimate the perceived difficulty of breathing on the Borg scale.
Rehabilitation barium swallow study: Participants with PD who are referred for a rehabilitation barium swallowing evaluation will be recruited for this study. Therefore, the swallowing evaluation is part of the normal clinical care of the patients and may vary based on the clinical necessity as judged by the treating speech-language pathologist. Generally, the standard clinical evaluation protocol consists of multiple swallows of thin liquid barium, pudding-thick barium, and a cracker or cookie coated with barium. For the purposes of this study, the researchers will review the most recently recorded swallow study and identify the worst observed penetration-aspiration (PA) score (ranging from 1-8, where 1 is no penetration or aspiration, and 8 is silent aspiration). The PA score will be recorded in order to determine whether the participant has trouble swallowing (scores of 3-8) or not (scores of 1 and 2).
