Arterial oxygen saturation during Cheyne-Stokes respiration in heart failure patients: does measurement site matter?

Enhancement of oxygen sensing performance of metalloporphyrin film modified with nano Al2O3 powder

In this work, the metalloporphyrin film of PtOEP/Poly (St-co-TFEMA) modified by nano Al₂O₃ powder was prepared, and the enhancement performance of oxygen sensing was studied in detail. It was verified that the modified film extended the residence time of oxygen through the characterization of SEM. The phosphorescence intensity changes with the content of Al₂O₃ and PtOEP were studied. The Stern-Volmer equations before and after modification of Al₂O₃ powder was compared. It was found that the linearity of the calibration curve was still high, but the oxygen sensitivity value of K_SV was significantly improved due to the increase of quenching probability between indicator and oxygen. Finally, the stability test shows that the Al₂O₃@PtOEP/Poly (St-co-TFEMA) oxygen sensing film presents a strong anti-photo-bleaching ability, and the response time is shortened.

Computer-Assisted Assessment of the Interaction Between Arousals, Breath-by-Breath Ventilation, and Chemical Drive During Cheyne-Stokes Respiration in Heart Failure Patients

Transient increases in ventilation induced by arousal from sleep during Cheyne-Stokes respiration in heart failure patients are thought to contribute to sustaining and exacerbating the ventilatory oscillation. The only possibility to investigate the validity of this notion is to use observational data. This entails some significant challenges: (i) accurate identification of both arousal onset and offset; (ii) detection of short arousals (<3 s); (iii) breath-by-breath analysis of the interaction between arousals and ventilation; (iv) careful control for important confounding factors. In this paper we report how we have tackled these challenges by developing innovative computer-assisted methodologies. The identification of arousal onset and offset is performed by a hybrid approach that integrates visual scoring with computer-based automated analysis. We use a statistical detector to automatically discriminate between dominant theta–delta and dominant alpha activity at each instant of time. Moreover, a statistical detector is used to validate visual scoring of K complexes, delta waves or artifacts associated with an EEG frequency shift, as well as frequency shifts to beta activity. A high-resolution (250 ms) state-transition diagram providing continuous information on the sleep-wake state of the subject is finally obtained. Based on this information, arousals are automatically identified as any state change from sleep to wakefulness lasting ≥2 s. The assessment of the interaction between arousals and ventilation is performed using a breath-by-breath, case-control approach. The arousal-associated change in ventilation is measured as the normalized difference between minute ventilation in the case breath (i.e., with arousal) and that in the control breath (i.e., without arousal), controlling for sleep stage and chemical drive. The latter is estimated by using information from pulse oximetry at the finger. In the last part of the paper, we discuss main potential sources of error inherent in the described methodologies.

Interaction Between Arousals and Ventilation During Cheyne-Stokes Respiration in Heart Failure Patients: Insights From Breath-by-Breath Analysis

Study Objectives: Arousals from sleep during the hyperpneic phases of Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) in patients with heart failure are thought to cause ventilatory overshoot and a consequent longer apnea, thereby sustaining and exacerbating ventilatory instability. However, data supporting this model are lacking. We investigated the relationship between arousals, hyperpnea and post-hyperpnea apnea length during CSR-CSA. Methods: Breath-by-breath changes in ventilation associated with the occurrence of arousal were evaluated in 18 heart failure patients with CSR-CSA, apnea-hypopnea index ≥15/h and central apnea index ≥5/h. The change in apnea length associated with the presence of arousal during the previous hyperpnea was also evaluated. Potential confounding variables (chemical drive, sleep stage) were controlled for. Results: Arousals were associated with a large increase in ventilation at the beginning of the hyperpnea (+76 ± 35%, p < 0.0001), that rapidly declined during its crescendo phase. Around peak hyperpnea, the change in ventilation was -8 ± 26% (p = 0.14). The presence of arousal during the hyperpnea was associated with a median increase in the length of the subsequent apnea of +4.6% (Q1, Q2: -0.7%, 20.5%; range: -8.5%, 36.2%) (p = 0.021). The incidence of arousals occurring at the beginning of hyperpnea and mean ventilation in the region around its peak were independent predictors of the change in apnea length (p = 0.004 and p = 0.015, respectively; R² = 0.78). Conclusions: Arousals from sleep during CSR-CSA in heart failure patients are associated with a rapidly decreasing ventilatory overshoot at the beginning of the hyperpnea, followed by a tendency toward a slight ventilatory undershoot around its peak. On average, arousals are also associated with a modest increase in post-hyperpnea apnea length; however, large increases in apnea length (>20%) occur in about a quarter of the patients.

Sinusoidal changes in transcutaneous oxygen pressure, suggesting Cheyne-Stokes respiration, are frequent and of poor prognosis among patients with suspected critical limb ischemia

BACKGROUND AND AIMS

Transcutaneous oxygen pressure (TcpO₂) is used in patients with suspected critical limb ischemia (CLI). Sinusoidal changes (SC~) in TcpO₂ are found in patients with Cheyne-Stokes respiration (CSR). We aimed to determine the characteristics of TcpO₂ changes at rest in patients with suspected CLI, define the objective criteria for SC ~ TcpO₂ patterns (SC+), and estimate the prevalence of SC+ in our population and its impact on the outcome.

METHODS

We retrospectively analyzed 300 chest TcpO₂ recordings performed in a 16-month period. We determined the presence/absence of SC ~ TcpO₂ by visual analysis. We determined the acceptable error in the regularity of peaks of the cross-correlation with ROC curve analysis, among patients with typical SC ~ TcpO₂ and non-sinusoidal patterns. Then, we defined SC + as a minimum of five peaks, a standard deviation of TcpO₂ >1.25 mmHg, an error in regularity of peaks of the cross-correlation < 10%, and a cycle length between 30 and 100 s. In patients included until October 2019, we compared the outcome as a function of SC + or SC- with Cox models.

RESULTS

Mathematical detection of SC + found that 43 patients (14.3%) fulfilled all four defined criteria at the chest level, but only 23 did so at the limb level. In the follow-up of 207 patients, the presence of Sc ~ TcpO₂ at the chest significantly increased the risk of mortality: hazard ratio: 2.69 [95%CI: 1.37-5.30]; p < 0.005.

CONCLUSIONS

SC ~ TcpO₂ is frequent, and is associated with a poor outcome in patients with suspected CLI.