An Hybrid 70% Plus 85% Predicted Heart Rate Bicycle Stress Test Performed on Two Consecutive Days
James N. Baraniuk, M.D. Christian R. Timbol, Yin Zheng, Amber Surian, Rania Esteitie, Murugan Ravindran, Samantha J. Merck, Rakib Rayhan, Oluwatoyin Adewuyi, and Sharon O’Brien
Pain and Fatigue Research Alliance, Georgetown University
Objective:
Determine the merits of submaximal and maximal bicycle stress tests for Gulf War Illness (GWI), CFS and healthy veterans and controls (HC) for tandem, 2 day testing.
Methods:
Subjects exercised on a Schwinn bicycle ergometer.
Cardiopulmonary function was measured using mouthpieces and Vmax software.
27 GWI and 8 HC participated in 3 bicycle exercise stress test protocols:
#1. 13 GWI and 2 HC had standardized ramped VO2max tests with exercise until physical limitations caused the test to end (85%HR).
#2. 6 GWI and 4 HC cycled at 70% of maximum predicted heart rate for 25 min then accelerated to 85% without cardiopulmonary testing (70%+85%).
#3. 11 GWI and 5 HC had VO2max tests that began with 25 min at 70% maximum heart rate that was followed by acceleration to 85% (70%+85% plus VO2max).
Symptomatic Responses:
Borg Dyspnea Scores were significantly higher for GWI subjects on DAY 1 (3.9; 2.8 to 4.9 [mean; 95% C.I.]; n=25) and DAY 2 (4.1; 3.1 to 5.0) than HC (1.4; 0.1 to 2.6; n=9; p=0.016 by t-test; and 1.3; -0.1 to 2.6; p=0.0053; n=8; respectively).
On DAY 1, whole body pain and fatigue scores at rest and after exercise were in the 3 to 15 range on the 20 point anchored ordinal Gracely Scale for GWI (n=15) compared to 0 to 3 for HC (0.032≥p≥0.00005; n=8).
DAY 2 results were marginally higher at 6 to 16 for GWI and 0 to 5 for HC (0.043≥p≥0.0000004).
None of the HC subjects complained of pain or fatigue on either day.
Adverse Events:
Protocol #1.
Three GWI had to stop because of fatigue and dyspnea with VO2max at 25%, 32% and 50% of predicted.
A fourth had dyspnea and oxygen desaturation (88% by pulse oximetry).
A fifth GWI subject stopped because their systolic blood pressure dropped by 22% as they neared 70% HR.
Protocol #2.
Two GWI had to stop after 25 min at 70% of maximum HR because of fatigue or muscle pain.
A third GWI subject increased their HR by only 29% before stopping.
Protocol #3.
One GWI became so exhausted after 70% HR that within 15 minutes he had fallen asleepfor 1 hour.
One veteran who was otherwise healthy on examination could only exercise to VO2max of 48% of predicted before stopping because of dyspnea on both DAYs.
This subject and another otherwise healthy appearing veteran both demonstrated orthostatic tachycardia (ΔHR>30 bpm).
Energy Expenditures:
In the two 70%+85% protocols, HC expended more METs to reach 85%HR (7.95; 7.08 to 8.82) thanGWI (4.94; 4.16 to 5.72; p=0.0015).
On DAY 2, this significant difference was found for 70% HR in HC(5.00; 4.26 to 5.74; n=4 vs. 3.17; 2.54 to 3.80; n=6; p=0.0064).
At 85% HR the variance of the GWI data was too large for a significant difference to be detected.
Expenditures by GWI subjects were different on DAY 2 from DAY 1. Watts needed to reach 85% HR inramped exercise for GWI were higher on DAY 1 (202; 160 to 245; n=13) than DAY 2 (170; 138 to 202; n=12; p=0.015 by paired t-test).
In contrast, the 70%+85% protocol required more calories on DAY 2 (179; 155 to 203; n=12) than DAY 1 (162; 132 to 191; p=0.033) in a different group of GWI subjects.
HC had no differences in energy requirements between DAY 1 and DAY 2.
Conclusion:
The 70%+85% VO2max test was the optimal provocation.
James N. Baraniuk, M.D.
gwiresearch@georgetown.edu Room 3004F3-PHC Building, 3800 Reservoir Road, N.W., Washington DC 20007-2197 USA
Supported by NIEHS RO1 ES015382 and DoD W81XWH-07-1-0618 and W81XWH-09-1-0526.