Medicine & Science in Sports & Exercise:
Thursday Morning Poster Presentations: Posters displayed from 7:30 a.m.-12:30 p.m.: One-hour author presentation times are staggered from 8:30-9:30 a.m. and 9:30-10:30 a.m.: D-27 Free Communication/Poster - Respiratory Function: THURSDAY, JUNE 1, 2006 2:00 PM - 5:00 PM ROOM: Hall B
Wake Forest University School of Medicine, Winston-Salem, NC.
Supported by N.I.H. Grants AG18915, AG12257 and P60AG10484
Patients with systolic heart failure (SHF) have been shown to have abnormal ventilatory responses during acute submaximal exercise including: an increased minute ventilation (VE), and increased ventilatory equivalents for oxygen (VE/VO2) and carbon dioxide (VE/VCO2). While recent studies suggest that patients with SHF and diastolic heart failure (DHF) have generally similar acute exercise responses, the ventilatory responses of these two groups have not been compared.
PURPOSE: To compare VE, VE/VO2, VE/VCO2, end-tidal O2 and end-tidal CO2 at rest, submaximal (12 watts), and at peak exercise in older patients with SHF and DHF to normal older subjects (NOS).
METHODS: Symptom limited graded exercise tests were conducted on 147 patients (60 SHF, 59 DHF, 28 NOS) using a bicycle ergometer protocol that started at 12 watts and progressed to 25 watts after 2 minutes. The stages continued to increase by 25 watt increments every three minutes until maximal effort was achieved. Breath-by-breath expired gas analysis was performed using a commercially available system with online computer calculations. Values obtained for analyses were averaged from the last 4, 15-second data points during the final minute of each stage. Univariate analysis of covariance (adjusting for resting values, gender, and body surface area) was used to compare the three groups at rest, submaximal, and peak exercise.
RESULTS: There were no significant differences among the three groups at rest for the ventilatory measures of interest. However, VE/VO2 was significantly higher in the SHF vs. NOS at submaximal (34.4 ± 7.7 vs. 29.3 ± 3.8, p=0.000) and peak exercise (43.5 ± 8.4 vs. 40.3 ± 5.8, p=0.015). There were no significant differences in VE/VO2 at submaximal exercise between SHF and DHF (34.4 ± 7.7 vs. 31.8 ± 7.2) or DHF and NOS. VE/VCO2 was significantly (p=0.002) higher in SHF versus DHF and NOS at submaximal (39.0 ± 7.0, 36.5±6.8, 35.6 ±4.4, respectively) and peak exercise (40.9 ±7.2, 38.4±9.5, 35.1 ± 4.5, respectively) (p=0.000). As expected, peak VE was significantly higher in NOS vs. SHF and DHF due to higher peak workload achieved in NOS.
CONCLUSION: These data suggest that older SHF patients have an inefficient ventilatory pattern during exercise (i.e. elevated VE/VO2 and VE/VCO2) versus NOS and DHF. DHF also tend to an inefficient ventilatory pattern versus NOS, yet these do not reach statistical significance. It appears that SHF has a greater impact on ventilatory function during submaximal and peak exercise compared with DHF.