Continuous blood pressure measurement using the pulse transit time: Comparison to intra-arterial measurement.

Continuous blood pressure (BP) measurement allows the investigation of transient changes in BP and thus may give insights into mechanisms of BP control. We validated a continuous, non-invasive BP measurement based on the pulse transit time (PTT), i.e., BP(PTT), by comparing it with the intra-arterial BP (BP(i.a.)) measurement. Twelve subjects (five females and seven males) were included. BP(i.a.) was obtained from the radial artery using a system from ReCor Medical. Systolic and diastolic BP were calculated using the PTT (BP(PTT), SOMNOscreen). (PTT) was determined from the electrocardiogram and the peripheral pulse wave. The BP was modulated by application of increasing doses of dobutamine (5, 10, 20 µg/kg body mass). Systolic BP(PTT) and systolic BP(i.a.) correlated significantly (R = 0.94). The limits of agreement in the Bland-Altman plot were ± 19 mmHg; the mean values differed by 1 mmHg. The correlation coefficient for the diastolic BP measurements was R = 0.42. The limits of agreement in the Bland-Altman plot were ± 18 mmHg, with a mean difference of 5 mmHg in favour of the BP(PTT). The study demonstrates a significant correlation between the measurement methods for systolic BP. The results encourage the application of PTT-based BP measurement for the evaluation of BP dynamics and pathological BP changes.

Analysis of interaction of acute atrial overdrive pacing with sleep-related breathing disorder.

Dose-related effects of atrial overdrive pacing (AOP) on sleep-related breathing disorder (SRBD) were studied. Fourteen patients with pacemakers with moderate to severe SRBD (mean screening apnea-hypopnea index [AHI] 35.2 +/- 21.9 events/hour) were randomized to 3 levels of pacing (50, 10, and 20 beats/min greater than the mean nocturnal heart rate) and studied by polysomnography, observing for changes in AHI. At the 2 AOP levels, no significant change was observed in the primary end point of reduction in AHI. Additionally, there was no observed impact on secondary end points of the study. Cyclic variation of heart rate was progressively abolished with higher levels of AOP without affecting AHI. Large variations were observed between the screening and control studies in SRBD indexes in a number of patients. In conclusion, AOP demonstrated no benefit to predominantly obstructive SRBD disorder of at least moderate severity.

Feasibility of automated detection of advanced sleep disordered breathing utilizing an implantable pacemaker ventilation sensor.

OBJECTIVES: This study tested the feasibility of automatically detecting advanced sleep disordered breathing (SDB) from a pacemaker trans-thoracic impedance sensor. BACKGROUND: SDB is prevalent yet under-diagnosed in patients with cardiovascular disease. The potential for automated detection of SDB in patients receiving pacemakers with respiration sensors has not been fully explored. We hypothesized that the trans-thoracic impedance sensor could be utilized for automatic detection of advanced SDB. METHODS: Patients underwent overnight polysomnography (PSG). The pacemaker trans-thoracic impedance signal was simultaneously recorded and time synchronized with the polysomnograph. Cardiovascular health variables were abstracted from medical records. Apnea was defined as cessation of inspiratory airflow lasting 10 seconds or longer. Hypopnea was defined as a reduction of tidal volume of at least 30% from baseline tidal volume, lasting 10 seconds or more. A computer algorithm (PM-A) was developed to automatically detect SDB from the pacemaker impedance sensor data. The performance of automated SDB detection was compared against PSG. RESULTS: Sixty patients (aged 69 +/- 12 years, 45 males) were studied. Advanced SDB (moderate or severe) was diagnosed in 40 patients. Severe SDB (apnea-hypopnea index [AHI]> or = 30) was diagnosed in 32 patients (53%), but only 5 patients had prior diagnosis of the disease. Moderate SDB (30 > AHI > 15) was diagnosed in 8 patients of whom only two were previously diagnosed. Cardiovascular health variables did not predict the presence of advanced SDB. PM-A derived AHI correlated with that of the PSG (r = 0.80, P < 0.01). The algorithm identified patients with advanced SDB with 82% sensitivity and 88% specificity. CONCLUSIONS: It is feasible to automatically measure SDB severity using a pacemaker trans-thoracic impedance sensor. Advanced SDB was frequently undiagnosed in this cohort of pacemaker patients.

Interaction of sleep disturbances and gastroesophageal reflux in chronic laryngitis.

BACKGROUND: A considerable percentage of patients with reflux laryngitis do not respond to conventional treatment with proton pump inhibitors or prokinetics. At the present time, the reasons for this are not well known. PURPOSE: To investigate whether nocturnal reflux associated with sleep-related respiratory disorders is the cause of refractory laryngitis. METHOD: The data from 227 patients (133 women, ages 18 to 75 years, body mass index 17.4 to 38.3, mean 32.1 kg/m(2)) with LG were analyzed retrospectively. All received laryngoscopy and gastroscopy. All patients initially received 40- to 80 mg omeprazole and underwent a follow-up laryngoscopy after 6 weeks. Of the patients, 202 showed a clear improvement, whereas 25 (11.1%) did not. All underwent 24-hour pH monitoring and cardiorespiratory polysomnography. RESULTS: All of the patients showed laryngoscopic signs of LG. Of the patients, 102 (45%) had a hiatal hernia and 53 (28%) suffered from reflux esophagitis. Forty-two patients (19%) were found to have Helicobacter pylori in the stomach. Among the 25 patients who failed to respond to omeprazole, pH monitoring showed nocturnal acid reflux in 15 (60%). Twenty-four patients (96%) showed a sleep-related respiratory disturbance manifesting as pathologic snoring (16 patients) or obstructive sleep apnea (8 patients, respiratory disturbance index [RDI] 11 to 33, mean 16.3/h). All received nasal continuous positive airway pressure (nCPAP) treatment, 16 with constant mask pressure (4 to 12, mean, 5.6 mbar) and 8 with autoadjusting pressure. One patient abandoned treatment; the other 23 showed clear subjective and objective improvement after 3 months of treatment. CONCLUSIONS: Even without pH monitoring evidence of nocturnal reflux, refractory LG is very often associated with sleep-related respiratory disorders and responds well to nCPAP treatment. Prospective studies are needed to clarify the details of this association.