Daily changes in cardiac and vascular blood pressure components during breath holding episodes in obstructive sleep apnea patients after day-shift and night-shift work.

We evaluated daily variability in the cardiovascular response to arterial chemoreceptors activation during breath holding in shift workers who were obstructive sleep apnea patients. Ten patients and 10 weight and age-matched control subjects were enrolled in the study. The experimental sessions consisted of 10 episodes of breath holding on inspiration interspersed with 1 min free breathing periods, repeated every 6 h: at 0.00, 6.00, 12.00, 18.00 hours. The subjects were examined under two experimental protocols: after day-shift work and after night-shift work (36 h of sleep deprivation). Blood pressure (System Portapres), ECG, and arterial hemoglobin oxygen saturation were monitored continuously. Data analysis were based on Smietanowski procedures written in the 4-th generation script language of MATLAB environment. The two methods introduced by Smietanowski a enabled symbolic description of cardiovascular regulatory mechanisms as cardiac, vascular, or mixed type control (BBC), and allowed quantifying relative contributions of cardiac and vascular components in the blood pressure variability. During the part of the study conducted after day-shift work, repetitive apneas led to a significantly greater increase in blood pressure in the sleep apnea patients, as compared with the controls. BBC analysis demonstrated that in the patients the domination of vascular influences during breath holding periods reached 70+/-2.0% and was significantly greater in comparison with the control group: 56+/-2.8 (P<0.01). However, contribution of cardiac component in the blood pressure response to breath holding was greater in the control group: 32+/-2% as compared with the 18+/-2% in the group of patients (P<0.01). Under the conditions of sleep deprivation (night-work shift), greater blood pressure responses to breath holding were observed in all subjects, but they were larger in the group of sleep apnea patients. The cardiovascular responses to hypoxia during breath holding showed daily variability: greater responses at 12.00 and 18.00 declined at 0.00 and 6.00 h. BBC analysis indicated a greater domination of vascular component in the blood pressure response in patients: 71+/-2.8% vs. 58+/-2% in controls. The contribution of cardiac component predominated in the control group: 27+/-3% vs. 19+/-1% in patients.