Lung-to-finger Circulation Time Research Articles

Prolonged lung-to-finger circulation time indicates an increased risk of intermittent hypoxaemia in sleep apnoea patients.

Intermittent hypoxaemia is closely associated with cardiovascular dysfunction and may be a more accurate indicator of obstructive sleep apnoea (OSA) severity than conventional metrics. Another key factor is the lung-to-finger circulation time (LFCt), defined as the duration from the cessation of a respiratory event to the lowest point of oxygen desaturation. LFCt serves as a surrogate marker for circulatory delay and is linked with cardiovascular function. Yet, the specific associations between respiratory and hypoxaemia characteristics and LFCt in patients with OSA remain unclear. This study aims to investigate these associations, ultimately contributing to a more nuanced understanding of OSA severity. The study comprised 878 in-lab polysomnographies of patients with suspected OSA. The conventional OSA metrics were computed along with nine hypoxaemia metrics and then divided into quartiles (Q1-Q4) based on respiratory event duration. In addition, these were further divided into subquartiles based on LFCt. The empirical cumulative distribution functions (CDFs) and linear regression models were used to investigate the association between desaturation metrics and LFCt. The results showed that prolonged LFCt was associated with increased hypoxic severity. Based on CDFs, the hypoxic severity significantly increased with longer LFCt despite the duration of respiratory events. Furthermore, fall duration was elevated in patients with longer LFCt (Q1- desaturation fall duration (FallDur): 14.6 s; Q4-FallDur: 29.8 s; p<0.0001). The regression models also showed significant association between hypoxic severity and LFCt (Q1-desaturation fall slope (FallSlope): β=-3.224; Q4-FallSlope: β=-6.178; p<0.0001). Considering LFCt along with desaturation metrics might be useful in estimating the association between the severity of OSA, physiological consequences of respiratory events and cardiac health.

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.

Local temperature control improves the accuracy of cardiac output estimation using lung-to-finger circulation time after breath holding.

As timely measurement of the cardiac index (CI) is one of the key elements in heart failure management, a noninvasive, simple, and inexpensive method of estimating CI is keenly needed. We attempted to develop a new device that can estimate CI from the data of lung‐to‐finger circulation time (LFCT) obtained after a brief breath hold in the awake state. First, we attempted to estimate CI from the LFCT value by utilizing the correlation between 1/LFCT and CI estimated with MRI. Although we could obtain LFCT from 45 of 53 patients with cardiovascular diseases, we could not find the anticipated relation between 1/LFCT and CI. However, we realized that when we adopted only LFCT from patients with a finger temperature of ≥31°C, we could obtain a consistent and clear correlation with CI (correlation coefficient, r = .81). Thus, we next measured LFCT before and after warming the forearm. We found that LFCT decreased after the local temperature increased (from 27.5 ± 13.6 to 18.4 ± 5.3 s, p < 0.01). The correlation between the inverse of LFCT and CI improved after warming (1/LFCT vs. CI, from r = .69 to r = .82). The final Bland–Altman analysis between the measured and estimated CI values revealed that the bias and precision were −0.05 and 0.37 L min−1 m−2, respectively, and the percentage error was 34.3%. This study clarified that estimating CI using a simple measurement of LFCT is feasible in most patients and a low fingertip temperature strongly affects the CI‐1/LFCT relationship, causing an error that can be corrected by proper local warming.

Characterization of lung-to-finger circulation time in sleep study assessment: the Multi-Ethnic Study of Atherosclerosis

Objectives: Lung-to-finger circulation time (LFCT) measured from sleep studies may reflect underlying cardiac dysfunction. We aimed to examine the distribution of LFCT in community-dwelling men and women in order to better understand the factors determining LFCT between and within subjects. Approach: We included participants of the Multi-Ethnic Study of Atherosclerosis (MESA) Sleep with polysomnography-based evidence of sleep apnea (defined by apnea hypopnea index >15 hr−1). In a randomly selected subset of the analytical dataset, we tested an automated LFCT measurement method against the visual method. Using the automated method we then scored LFCTs from all eligible respiratory events for all included participants. A multiple regression model was constructed to determine factors independently associated with average LFCT across subjects. We also explored factors that are associated with LFCT within subjects using linear mixed-effect models. Main results: In a subset of the cohort (N = 39) there was a high correlation in average LFCT obtained by automated and visual methods (r = 0.96). In the analysis of 596 participants, men [19.6 (2.8)] (vs. women [17.9 (2.7) s], p < 0.0001) and older age (> 69 (vs. ≤ 69) had longer average LFCT (19.4 [2.8] vs. 18.5 [2.9] s, p < 0.0001). These associations persisted in multivariable analysis. No association was found with body habitus. Within subject analysis revealed trivial associations between apnea/hypopnea duration, apnea (vs. hypopnea), nadir O2 saturation and sleep stages (NREM vs. REM) and individual LFCT. Significance: Automated LFCT measurement was highly correlated with visual-based LFCT measurement. In this group of community-dwelling adults, male sex and older age were associated with higher average LFCT.

A Novel Method for Assessing Cardiac Output With the Use of Oxygen Circulation Time

We investigated whether a simple breath hold would yield dynamic oxygen (O2) saturation change and whether the derived circulation time would be useful in assessing cardiac function. Patients undergoing right heart catheterization for clinical indications (n = 48), including heart failure (HF; n = 24), were prospectively recruited. Each subject was instructed to hold their breath for 20-40 seconds. Lung to finger circulation time (LFCT), defined as the time from the point of rebreathing to nadir O2 desaturation, was correlated with cardiac output. Among 48 subjects recruited, 37 manifested ≥3% O2 desaturation allowing for an LFCT measurement. Mean LFCT was 38.5 ± 17.5 seconds (range 18.9-94.7 s). LFCT in patients with a clinical diagnosis of HF was significantly longer than those without (45.9 ± 19.9 s vs 31.5 ± 11.5 s; P = .01). Overall, the LFCT was inversely correlated with cardiac output (Fick: r = -0.56; P < .001 [n = 37]; thermodilution: r = -0.6; P = .001 [n = 27]). LFCT is prolonged in low cardiac output. LFCT is a novel method that may be useful to noninvasively assess cardiac function in HF.

PROLONGED LUNG TO FINGER OXYGEN CIRCULATION TIME PREDICTS LOW CARDIAC OUTPUT STATE

Based on indicator dilution method, using oxygen (O2) as an indicator and fingertip as a site of detection, lung to finger circulation time (LFCT) can be measured. We investigated whether simple breath hold followed by rebreathing of room air O2 would yield dynamic O2 saturation change and that the

Circulation time measurement from sleep studies in patients with obstructive sleep apnea.

Lung to finger circulation time (LFCT) can be estimated from polysomnography (PSG) in the presence of an apneic event by using oxygen as an indicator and a finger as the site of detection. The purpose of this study was to refine the methodology of LFCT measurement and to compare LFCT in patients with obstructive sleep apnea (OSA) with and without heart failure (HF). In a retrospective manner, 10 LFCT measurements per patient were made from the PSG in 171 consecutive patients with a diagnosis of OSA who were divided into two groups: (a) those with a clinical history of underlying HF (N = 42) and (b) those without HF (N = 129). Mean values were compared between the two groups. We also examined associations of LFCT with various factors in each group and the combined group separately using multiple regression analysis. Gender and age were significantly associated with LFCT in patients with OSA alone. Use of β-blockers was associated with LFCT in the group with OSA with HF. Among the entire cohort, HF, β-blocker, gender, and age were found to be significantly associated with LFCT. The presence of HF was the strongest predictor of a prolonged LFCT (adjusted mean LFCT: OSA only = 18.5 [95% CI: 17.2-19.7 sec] vs. OSA with HF = 26.1 [95% CI: 24.3-28.0 sec], p < 0.0001). LFCT can be reliably measured and is prolonged in patients with OSA and underlying HF. LFCT based on PSG may be a useful marker for detection of coexisting HF in patients with OSA.

Elimination of central sleep apnea by cardiac valve replacement: a continuous follow-up study in patients with rheumatic valvular heart disease

BackgroundRecent studies have suggested that cardiac surgery may affect sleep-disordered breathing (SDB) in chronic heart failure patients. However, the dynamic changes in sleep apnea and heart function after cardiac surgery and the mechanisms responsible for these changes remain unknown. MethodsPatients with rheumatic valvular heart disease (RVHD) and SDB were enrolled and followed up at three, six and 12months after cardiac valve replacement (CVR). Baseline and follow-up clinical data consisting of NYHA classification, 6min walk distance (6-MWD), medications, echocardiography, electrocardiography, chest X-ray, arterial blood gas, lung-to-finger circulation time (LFCT), and sleep data were collected and evaluated. ResultsTwenty-four central sleep apnea (CSA) patients and 15 obstructive sleep apnea (OSA) patients completed three follow-up assessments. Comparison of the baseline parameters between OSA patients and CSA patients showed that CSA patients had a worse baseline cardiac function assessed by higher NYHA class, shorter 6-MWD, larger left atrial diameter, longer LFCT, and enhanced chemosensitivity (higher pH and lower arterial carbon dioxide tension (PaCO2)). A continuous significant elevation in 6-MWD and left ventricular ejection fraction and decrease in NYHA class, plasma BNP, and left atrial diameter were found in both CSA and OSA patients. When comparing CSA and OSA patients, the CSA indices were remarkably reduced at month 3 post CVR and sustained throughout the trial, whereas there were no significant decreases in OSA index and hypopnea index. pH values and LFCT were markedly decreased and PaCO2 markedly increased in patients with CSA at the end of the third months following CVR. These changes were sustained until the end of the trial. ConclusionsCSA patients with RVHD had a worse baseline cardiac function, enhanced chemosensitivity and disordered hemodynamic as compared with OSA patients with RVHD. CSA were eliminated after CVR; however, there were no changes in OSA. The elimination of CSA, post CVR, is associated with the combined efficacies of improvement of cardiac function, normalized chemosensitivity, and stabilized hemodynamic.

Clinical characteristics of hospitalized heart failure patients with daytime cheyne-stokes respiration

Introduction Cheyne-Stokes respiration (CSR) frequently occurs in patients with heart failure (HF). CSR in HF patients is important because it may independently predict morbidity and mortality due to HF. In previous analyses of HF patients, CSR was observed not only in the nighttime but also in the daytime. Moreover, daytime CSR may also predict worse prognosis in HF patients. Most of these studies have evaluated HF patients only on chronic phase. Daytime CSR in patients with HF on sub-acute phase (during hospitalization) remains unknown. We therefore investigated prevalence and clinical characteristics of daytime CSR in hospitalized patients with worsening of HF. Materials and methods In consecutive patients who were hospitalized due to worsening of HF, breathing pattern was monitored with a portable respiratory polygraph continuously over 24 h after their condition was stabilized. The monitor comprised sensors for airflow and for respiratory effort and a pulse oximeter finger sensor. Body weight and blood test data were collected simultaneously. Results 28 HF patients were enrolled (age, 71.1_ plus/minus 11.4 years; 9 women; LVEF, 51.8_ plus/minus 15.1 %). Daytime CSR was highly prevalent (N = 22, 78.6%). In the nighttime, frequency of apneas and hypopneas per hour of recording expressed as nighttime apnea- hypopnea index (nAHI) was 19.0_ plus/minus 10.5 whereas AHI in the daytime (dAHI) was 8.8_ plus/minus 5.7. The patients were divided into two groups according to median value of the dAHI: higher dAHI group (dAHI ⩾ 8.4) and lower dAHI group (dAHI 8.4). We found no significant differences between two groups in baseline characteristics including age, sex, body mass index, plasma brain natriuretic peptide level, LVEF, New York Heart Association class, PaCO2 and the presence of atrial fibrillation or ischemic heart disease (IHD). We only found significant difference in lung-to-finger circulation time (LFCT) between two groups (38.0 vs 24.0 s; p 0.001) despite no difference in other cardiac parameters.In addition, LFCT was correlated with dAHI (r = 0.71, p 0.0001). LFCT was longer in men (men vs women, 33.8 vs 24.9 s, p 0.05) and patients with IHD (36.5 vs 26.5 s, p 0.01). Conclusion Daytime CSR is frequent in hospitalized patients with HF and is correlated with prolonged LFCT. Prolonged LFCT, which indicates impaired cardiac output, has an adverse effect on survival. Therefore, significant daytime CSR in hospitalized patients with HF might be a predictor of increased morbidity and mortality. Acknowledgements We express gratitude to all those who participated in this study.

A noninvasive method for estimating cardiac output using lung to finger circulation time of oxygen

To develop a safe, noninvasive, simple, inexpensive, and clinically adaptable method for estimating cardiac output, we evaluated the potential of lung to finger circulation time (LFCT) and buildup time (Tb) of oxygen as measured by pulse oximetry to estimate cardiac output. Significant correlation was found between cardiac output as measured by thermodilution and the inverse of LFCT (R = 0.76, p < 0.001, SEE = 0.9 L/min) as well as the inverse of Tb (R = 0.72, p < 0.001, SEE = 0.9 L/min).