Holger Kraiczi

Blood pressure, cardiac structure and severity of obstructive sleep apnea in a sleep clinic population.

Objectives We investigated whether the severity of obstructive sleep apnea (OSA) predicts blood pressure or cardiac left ventricular thickness in a clinical population of OSA patients, if adjustments are made for age, gender, use of antihypertensive agents, smoking, body mass index, history of coronary artery disease, hypercholesterolemia and circulating C-peptide concentrations. Design Relationships in this cross-sectional study were investigated with correlation analysis and multiple regression procedures. Patients and methods Apnea–hypopnea index (AHI, polysomnography) and office systolic and diastolic blood pressures (SBP and DBP) were measured in 81 subjects referred to a university hospital sleep laboratory. Ambulatory blood pressures were recorded during one 24 h cycle. Left ventricular (LV) muscle size was quantified as two-dimensionally directed M-mode-derived end-diastolic thickness of interventricular septum and posterior chamber wall. Results After adjustment for separate or the entire set of covariates, AHI predicted office SBP and DBP as well as daytime ambulatory DBP and night-time ambulatory SBP and DBP, but not daytime ambulatory SBP. In contrast, associations between AHI and LV muscle thickness reflected complex inter-relationships with confounding variables. Smoking and age suppressed, whereas body mass index (BMI) and hypertension inflated the relationship between OSA severity and LV muscle thickness in this study. Conclusions AHI is an independent predictor of several measures of blood pressure. OSA severity and LV muscle thickness appear to be primarily linked via increased blood pressure.

Finger plethysmography*/a method for monitoring finger blood flow during sleep disordered breathing

We investigated a non-invasive measurement for changes in finger blood flow during wakefulness and sleep. Changes in finger blood flow, reflected by pulse wave amplitude (PWA) derived from finger plethysmography, were compared with changes in forearm vascular flow assessed by venous occlusion plethysmography after intra-arterial infusion of norepinephrine (NE), phentolamine, and isoproterenol (n=15, 15, 14 subjects, respectively). Moreover, PWA was assessed during obstructive breathing during sleep (n=8 patients). Vasoconstriction in the finger (PWA) was stronger than that obtained in the forearm vascular bed in the higher NE dose range both without (ANOVA, P=0.002) and with concomitant phentolamine-induced alpha-receptor blockade (P=0.02). Isoproterenol increased forearm blood flow but did not induce flow changes detectable by the finger plethysmographic technique (P<0.001). PWA was significantly reduced during arousal from obstructive sleep apnea (-37.5+/-16.1%, P=0.002, n=6 patients), suggesting vasoconstriction in the digital vascular bed. PWA derived from finger plethysmography allows continuous, non-invasive measurement of changes in finger blood flow during wakefulness and sleep. However, as may be expected from the anatomical and functional differences between the finger and forearm vascular beds and demonstrated by the lack of response to beta(2)-receptor stimulation, PWA does not mimic forearm vascular flow characteristics. Thus, finger plethysmography may be a useful complement to current vascular research techniques, in particular to monitor sympathetic influences on skin blood flow in the finger.

Analytical extraction of regulatory peptides from rat lung tissue.

We evaluated protocols for the extraction of calcitonin gene-related peptide, neuropeptide Y, substance P, peptide YY and beta-endorphin from rat lung tissue for subsequent radioimmunoassay. The effects of varying acidity of the extraction solution and repeating extraction on the recovery of peptide immunoreactivity and non-specific tracer-binding were compared by analysis of variance. Moreover, variability of immunoreactivity was quantified for comparison. Considering all three criteria, the optimal acidity for extraction was: 0.1 M or 1 M acetic acid for CGRP and beta-endorphin, 0.1 M acetic acid for NPY, 1 M acetic acid for substance P and phosphate buffer for peptide YY. Double or combined extraction unambiguously improved assay results only for substance P. Reversed-phase high-performance liquid chromatography of CGRP-, NPY- and SP-immunoreactivity obtained from selected extracts suggested that differences in recovery of these peptides are not explainable by differential peptide fragmentation during extraction.