Sensitivity of peripheral chemoreceptors has been shown to be significantly enhanced in patients with arterial hypertension [1]. Enhanced chemoreception was suggested to result in alteration in the respiratory-sympathetic coupling and increased muscle vasoconstrictor activity which may contribute to the development of hypertension. These disturbances may lead to a hemodynamic instability during anesthesia [2]. Assessing the sensitivity of the peripheral chemoreflex (SPCR), we can predict the likelihood of developing respiratory and cardiovascular disorders during the treatment of these patients, during surgery and general anesthesia, to predict the course of the disease and its outcome. The aim of the study was to compare the breath-holding test to single-breath carbon dioxide test in the evaluation of the sensitivity of the peripheral chemoreflex in subjects with arterial hypertension.
Methods. The study involved 13 patients with essential arterial hypertension (H group) and 16 patients with normal blood pressure (C group). In all participants, breath-holding test was performed in the morning before breakfast: voluntary breath-holding duration was assessed three times, with 10 min intervals. After inspiration of a volume equal to 2/3 of the vital lung capacity, the participant was asked to hold their breath and the duration of voluntary apnea was measured from the beginning of the voluntary inspiration until reflex contractions of the diaphragm were noted by palpation. A mean value of the duration of the three samples was calculated. The single-breath carbon dioxide test [3] was performed the next day. The study was approved by the local ethics committee. All subjects provided signed informed consent to both tests. The reported study was funded by RFBR, research project No. 16-34-60147 mol_a_dk.
Results. The average sensitivity of peripheral chemoreflex measured with single-breath carbon dioxide test was 0.28 ± 0.14 L/min/mmHg in C group and 0.47 ± 0.15 L/min/mmHg in H group (p <0.05), the average breath-holding duration was 48 ± 13 seconds and 34 ± 12 seconds, respectively (p <0.05). During the correlation analysis a significant negative correlation between the results of two tests was noted in both groups (-0.79 in group C, (p <0.05) and -0,81 in group H).
Conclusion. Peripheral chemoreflex sensitivity is higher in patients with arterial hypertension. A breath-holding test reflects the sensitivity of the peripheral chemoreflex to carbon dioxide in patients with essential arterial hypertension.
Acknowledgements: 
1.	Giannoni A et al., J. Am. Coll. Cardiol. 53: 1975–80, 2009
2.	Trembach N et al, Resp. Physiol. And neurobiol. 235: 79–82, 2017 
3.	Chua TP et al., Eur. J. Clin. Invest. 25: 887–92, 1995

Breath-holding test in assessment of cardiorespiratory system in patients with arterial hypertension