Heart rate variability and cardiorespiratory coupling in obstructive sleep apnea: elderly compared with young.

INTRODUCTION: Aging is known to be a major contributing factor to the increased risk of obstructive sleep apnea (OSA). With aging, breathing undergoes significant changes during sleep, increasing the prevalence of apnea events, which affects heart rate variability (HRV) and cardiorespiratory coupling (CRC). OBJECTIVES: To compare HRV and CRC during wakefulness and sleep between young and elderly patients with and without OSA; and to determine whether the presence of OSA in young and elderly patients has a different impact on HRV and CRC during sleep. METHODS: One hundred subjects, 50 young (mean age, 27 ± 9; 20 normal and 30 OSA) and 50 elderly (mean age, 65 ± 7; 20 normal and 30 OSA), underwent polysomnography. Spectral, cross-spectrum, and HRV parameters were analyzed during wakefulness and sleep. RESULTS: The spectral analysis indicated that age affected HRV, with higher values of low frequency (P < 0.05) in elderly subjects during wakefulness and an interaction between the presence of OSA and age. OSA influenced HRV during sleep with lower LF/HF ratios during stage 2 (S2) and rapid eye movement (REM) sleep (P <0.05), with an interaction between the presence of OSA and age in REM sleep. Elderly patients had significantly lower percent tachogram power coherent with respiration (%TPCR) during wakefulness (P < 0.05), and OSA led to lower %TPCR during S2. CONCLUSIONS: Age and OSA have an unfavorable impact on HRV, with reduced autonomic modulation during wakefulness, S2, and REM sleep. Age affects CRC during wakefulness and the presence of OSA affects CRC during sleep.

Pleural opening impairs respiratory system compliance and resistance in off-pump coronary artery bypass grafting.

AIM: This study evaluated the effect of pleurotomy on respiratory system compliance and resistance in off-pump coronary artery bypass (OPCAB) using the left internal thoracic artery (LITA). METHODS: Thirty-two patients were prospectively allocated into two groups: OP group (n = 16 patients with open left pleural cavity); IP group (N.=16 patients with intact pleural cavity). Static and dynamic lung compliance and total respiratory system resistance calculation were recorded at anesthesia induction (before chest opening) and immediately after chest closure. RESULTS: Static lung compliance values significantly decreased after chest closure in both groups (P < 0.0001), but the OP group had a significantly greater decline (P = 0.0007). Dynamic lung compliance decreased in either groups after chest closure (P < 0.0001), however, no significant difference was found between groups (P = 0.228). Total respiratory system resistance increased in both groups (P < 0.05), however the OP group had a higher increase (P = 0.0005). Orotracheal intubation time (P = 0.041) and hospital stay (P = 0.0004) were higher in the OP group. CONCLUSION: Pleura opening and need of chest tube insertion induced significant reduction in static lung compliance and increase in total respiratory system resistance, furthermore contributing to impair pulmonary dysfunction in the early postoperative period after OPCAB.