Brat K(, Stastna N, Merta Z, Olson LJ, Johnson BD, CundrleI Jr

PLoS One. 2019 Apr 23;14(4):e0215997. doi: 10.1371/journal.pone.0215997.
eCollection 2019

INTRODUCTION: Measurement of ventilatory efficiency, defined as minute
ventilation per unit carbon dioxide production (VE/VCO2), by cardiopulmonary
exercise testing (CPET) has been proposed as a screen for hyperventilation
syndrome (HVS). However, increased VE/VCO2 may be associated with other disorders
which need to be distinguished from HVS. A more specific marker of HVS by CPET
would be clinically useful. We hypothesized ventilatory control during exercise
is abnormal in patients with HVS.
METHODS: Patients who underwent CPET from years 2015 through 2017 were
retrospectively identified and formed the study group. HVS was defined as dyspnea
with respiratory alkalosis (pH >7.45) at peak exercise with absence of acute or
chronic respiratory, heart or psychiatric disease. Healthy patients were selected
as controls. For comparison the Student t-test or Mann-Whitney U test were used.
Data are summarized as mean ± SD or median (IQR); p<0.05 was considered
significant.
RESULTS: Twenty-nine patients with HVS were identified and 29 control subjects
were selected. At rest, end-tidal carbon dioxide (PETCO2) was 27 mmHg (25-30) for
HVS patients vs. 30 mmHg (28-32); in controls (p = 0.05). At peak exercise PETCO2
was also significantly lower (27 ± 4 mmHg vs. 35 ± 4 mmHg; p<0.01) and VE/VCO2
higher ((38 (35-43) vs. 31 (27-34); p<0.01)) in patients with HVS. In contrast to
controls, there were minimal changes of PETCO2 (0.50 ± 5.26 mmHg vs. 6.2 ± 4.6
mmHg; p<0.01) and VE/VCO2 ((0.17 (-4.24-6.02) vs. -6.6 (-11.4-(-2.8)); p<0.01))
during exercise in patients with HVS. The absence of VE/VCO2 and PETCO2 change
during exercise was specific for HVS (83% and 93%, respectively).
CONCLUSION: Absence of VE/VCO2 and PETCO2 change during exercise may identify
patients with HVS.