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Learning Occurs With Repetitions of Inspiratory Loading* FREE TO VIEW

Stasia Jastrzembski-Wieber, MD, FCCP; Marc Lavietes, MD, FCCP; Art Ritter, PhD; Tom C. Banwell, MD; John Ricci, PhD; Neil S. Cherniack, MD
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*From the University of Medicine and Dentistry of New Jersey, Newark, NJ.

Correspondence to: Stasia Jastrzembski-Wieber, MD, FCCP, 150 Bergen St, UHI354, Newark, NJ 07103; e-mail: jastrzsa@umdnj.edu

Chest. 2003;123(3_suppl):432S-433S. doi:10.1378/chest.123.3_suppl.432S
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The goal of this study was to determine whether sensations of dyspnea would change when inspiratory resistive loads were applied on several consecutive days in healthy subjects. We hypothesized that learning occurs with repetitions of inspiratory loading and would cause dyspnea to attenuate with repeated exposure to the same load.

We recruited four study groups, each with five subjects. All subjects underwent normal spirometry. Subjects breathed through a snugly fit facemask, and a one-way valve separated inspiratory and expiratory airflow. Airflow, frequency, and volume were measured continuously. Each session consisted of 90 min. For the first 30 min, the subjects breathed with no inspiratory load present. In the last 60 min, the load varied according to group assignment: group 1, no inspiratory load; group 2, low inspiratory load (1.3 cm H2O/L/s); or group 3, medium inspiratory load (3.4 cm H2O/L/s); or group 4, heavy inspiratory load (14.1 cm H2O/L/s). Trials were repeated on 3 consecutive days for the first three groups and for 4 days for the fourth group. Borg scores were obtained at the beginning and the end of the first 30 min, and at the beginning of loaded breathing and every 30 min thereafter. Anxiety was measured using the State-Trait Anxiety Inventory.

We found that dyspnea was significantly greater in subjects exposed to the heavy load, when compared to the control subjects and low-load group (Tukey-Kramer multiple comparison). We further investigated subjects exposed to the heavy-loaded group for a fourth day. We found that dyspnea was significantly improved in the heavy-loaded subjects on this fourth day. Anxiety did not change significantly throughout the protocol.

These findings indicate that there is a threshold of inspiratory loading where normal subjects experience dyspnea, and that normal subjects are able to overcome this dyspnea. This compensation occurs over days and represents learning.

This study was made possible by a grant from the American Lung Association/New Jersey Thoracic Society.




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