Changes in lung to finger circulation time measured via cardiopulmonary polygraphy in patients with varying types of heart disease

Lung-to-finger circulation time can be measured stably with high reproducibility by simple breath holding method in cardiac patients

Lung to finger circulation time (LFCT) has been used to estimate cardiac function. We developed a new LFCT measurement device using a laser sensor at fingertip. We measured LFCT by measuring time from re-breathing after 20 s of breath hold to the nadir of the difference of transmitted red light and infrared light, which corresponds to percutaneous oxygen saturation. Fifty patients with heart failure were enrolled. The intrasubject stability of the measurement was assessed by the intraclass correlation coefficient (ICC). The ICC calculated from 44 cases was 0.85 (95% confidence interval: 0.77–0.91), which means to have “Excellent reliability.” By measuring twice, at least one clear LFCT value was obtained in 89.1% of patients and the overall measurability was 95.7%. We conducted all LFCT measurements safely. High ICCs were obtained even after dividing patients according to age, cardiac index (CI); 0.85 and 0.84 (≥ 75 or < 75 years group, respectively), 0.81 and 0.84 (N = 26, ≥ or < 2.2 L/min/M²). These results show that our new method to measure LFCT is highly stable and feasible for any type of heart failure patients.

Prolonged Circulation Time Is Associated With Mortality Among Older Men With Sleep-Disordered Breathing

BACKGROUND

Conventional metrics to evaluate sleep-disordered breathing (SDB) have many limitations, including their inability to identify subclinical markers of cardiovascular (CV) dysfunction.

RESEARCH QUESTION

Does sleep study-derived circulation time (Ct) predict mortality, independent of CV risks and SDB severity?

STUDY DESIGN AND METHODS

We derived average lung to finger Ct (LFCt) from sleep studies in older men enrolled in the multicenter Osteoporotic Fractures in Men (MrOS) Sleep study. LFCt was defined as the average time between end of scored respiratory events and nadir oxygen desaturations associated with those events. We calculated the hazard ratio (HRs) for the CV and all-cause mortality by LFCt quartiles, adjusting for the demographic characteristics, body habitus, baseline CV risk, and CV disease (CVD). Additional models included apnea-hypopnea index (AHI), time with oxygen saturation as measured by pulse oximetry (SpO₂) < 90% (T90), and hypoxic burden. We also repeated analyses after excluding those with CVD at baseline.

RESULTS

A total of 2,631 men (mean ± SD age, 76.4 ± 5.5 years) were included in this study. LFCt median (interquartile range) was 18 (15-22) s. During an average ± SD follow-up of 9.9 ± 3.5 years, 427 men (16%) and 1,205 men (46%) experienced CV death and all-cause death, respectively. In multivariate analysis, men in the fourth quartile of LFCt (22-52 s) had an HR of 1.36 (95% CI, 1.02-1.81) and 1.35 (95% CI, 1.14-1.60) for CV and all-cause mortality, respectively, when compared with men in the first quartile (4-15 s). The results were similar when additionally adjusting for AHI, T90, or hypoxic burden. Results were stronger among men with no history of CVD at baseline.

INTERPRETATION

LFCt is associated with both CV and all-cause mortality in older men, independent of baseline CV burden and SDB metrics. LFCt may be a novel physiologic marker for subclinical CVD and adverse outcomes in patients with SDB.