CORPUS 1 pilot study: evaluating the impact of physical capacity on the quality of single operator continuous-chest-compression-only cardio pulmonary resuscitation

1. Average values of compression rate (ECCs/min) and compression depth (mm), obtained after 1 minute, 3 minutes, and for two consecutive time periods of 5 minutes (5 - 10’, 10 - 15’)
2. Heart rate during CCR, measured continuously by using a commercial heart rate monitor (Polar, Oy, Finland)
3. Blood lactate levels (mmol/L), measured with capillary blood samples taken at baseline and after 5, 10 and 15 minutes and using an automated lactate analyser

1. Cardiopulmonary exercise capacity. All subjects performed a maximal cardiopulmonary bicycle exercise test, designed to reach peak oxygen uptake capacity (VO2peak) within 8 - 12 minutes, as executed in previous studies from our laboratory. During the cycling test, an electronically braked Ergo 1500 cycle (ErgoFit, Pirmasens, Germany) was used. The cycling frequency was set at 70 cycles/min and the test was ended when the subject failed to maintain a cycling frequency of at least 60 cycles/min. Both the starting and incremental cycling resistance was set between 30 and 45 Watts, depending on age, height, weight, and gender. The cycling resistance increased every single minute. Before every test, a gas and volume calibration was done automatically. During the tests, environmental temperature was kept stable (20°C). During the exercise tests, pulmonary gas exchange analysis was performed by a cardiopulmonary ergospirometry device (Schiller CS200, Schiller AG, Switzerland). Oxygen uptake capacity (VO2), respiratory exchange ratio (RER), and carbon dioxide output (VCO2) were collected breath-by-breath and averaged every 10 seconds. By plotting exercise VO2 against exercise VCO2, ventilatory threshold was calculated by V-slope method, as executed in previous studies from our laboratory. A software programme of the ergospirometry device determined the break point of the two slopes. Maximal cycling power output (Wpeak) was reported.
2. Muscle strength. Muscle strength measurements of the upper body were performed using a standardised strength testing protocol on an isokinetic dynamometer (Biodex). Following a 5-minute standardised warming-up (Technogym Lat Pull, Pectoral, ArmCurl), subjects were positioned and fixated in a semi supine (15° backward inclination) sitting position (shoulder and thorax fixation). The rotational axis of the dynamometer was aligned with the transverse shoulder/elbow-joint axis and strapped to the distal end of the humerus/radius-ulna. The alignment of the dynamometer was systematically controlled using anatomical reference points. To test upper body strength each subject performed two maximal isometric shoulder flexions, extensions, adductions, abductions, internal and external rotations as well as elbow flexion and extensions (3 seconds) at respective shoulder/elbow angels of 45° and 90° interspersed by 45-second rest intervals. Maximal isometric torque at each angle was calculated as the average of the manually smoothed static torque curves. After a brief rest period upper body muscle fatigue was tested. Subjects performed one bout of 20 maximal isokinetic (180°/S) shoulder flexions, extensions, adductions, abductions, internal and external rotations and elbow flexions and extensions from 90° to 20° (ROM of 70°). After each contraction the upper/lower arm was returned passively to the 90° point. Muscle fatigue was calculated as the percentage total work decrease from the first three contractions to the last three. All tests were performed unilaterally. Immediately after the muscle strength measurements, the same examiner would ask subjects to perform dominant hand dynamometry (Jamar handgrip dynamometer; Sammons Preston Rolyan, Bolingbrook, IL) two times. Subjects were standing upright with their elbows at 90°.