Dietary nitrate supplementation reduces low frequency blood pressure fluctuations in rats following distal middle cerebral artery occlusion.

It is known that high blood pressure variability (BPV) in acute ischemic stroke is associated with adverse outcomes, yet there are no therapeutic treatments to reduce BPV. Studies have found increasing nitric oxide (NO) bioavailability improves neurological function following stroke, but whether dietary nitrate supplementation could reduce BPV remains unknown. We investigated the effects of dietary nitrate supplementation on heart rate (HR), blood pressure (BP), and beat-to-beat BPV using wireless telemetry in a rat model of distal middle cerebral artery occlusion. Blood pressure variability was characterized by spectral power analysis in the low frequency (LF; 0.2-0.6 Hz) range prestroke and during the 7 days poststroke in a control group ( n = 8) and a treatment group ( n = 8, 183 mg/l sodium nitrate in drinking water). Dietary nitrate supplementation moderately reduced systolic BPV in the LF range by ~11% compared with the control group ( P = 0.03), while resting BP and HR were not different between the two groups ( P = 0.28 and 0.33, respectively). Despite systolic BPV being reduced with dietary nitrate, we found no difference in infarct volumes between the treatment and the control groups (1.59 vs. 1.62 mm3, P = 0.86). These findings indicate that dietary nitrate supplementation is effective in reducing systolic BPV following stroke without affecting absolute BP. In light of mounting evidence linking increased BPV with poor stroke patient outcome, our data support the role of dietary nitrate as an adjunct treatment following ischemic stroke. NEW & NOTEWORTHY Using a rat model of stroke, we found that dietary nitrate supplementation reduced low frequency blood pressure fluctuations following stroke without affecting absolute blood pressure values. Since blood pressure fluctuations are associated with poor clinical outcome in stroke patients, our findings indicate that dietary nitrate could be an effective strategy for reducing blood pressure fluctuations, which could help reduce stroke severity and improve patient recovery.

Food safety labelling of chicken to prevent campylobacteriosis: consumer expectations and current practices.

BACKGROUND: Campylobacter is the leading cause of bacterial gastroenteritis worldwide, and contaminated chicken is a significant vehicle for spread of the disease. This study aimed to assess consumers' knowledge of safe chicken handling practices and whether their expectations for food safety labelling of chicken are met, as a strategy to prevent campylobacteriosis. METHODS: We conducted a cross-sectional survey of 401 shoppers at supermarkets and butcheries in Wellington, New Zealand, and a systematic assessment of content and display features of chicken labels. RESULTS: While 89% of participants bought, prepared or cooked chicken, only 15% knew that most (60-90%) fresh chicken in New Zealand is contaminated by Campylobacter. Safety and correct preparation information on chicken labels, was rated 'very necessary' or 'essential' by the majority of respondents. Supermarket chicken labels scored poorly for the quality of their food safety information with an average of 1.7/5 (95% CI, 1.4-2.1) for content and 1.8/5 (95% CI, 1.6-2.0) for display. CONCLUSIONS: Most consumers are unaware of the level of Campylobacter contamination on fresh chicken and there is a significant but unmet consumer demand for information on safe chicken preparation on labels. Labels on fresh chicken products are a potentially valuable but underused tool for campylobacteriosis prevention in New Zealand.

Agreement between finger plethysmography- and brachial oscillometry-derived blood pressure measurements.

PURPOSE: Blood pressure (BP) is commonly assessed by brachial oscillometry in clinical practice, whereas in physiological studies, finger plethysmography is often employed. This study assessed the limits of agreement between BP metrics obtained from each device. METHODS: In 96 participants, we simultaneously recorded BP by brachial oscillometry (BP+; Uscom, Sydney, NSW, Australia) and finger plethysmography (Finometer MIDI, MLE1054-V; Finapres Medical Systems B.V., Amsterdam, the Netherlands). Agreement between the two devices was assessed by correlation and Bland-Altman analysis. We assessed average BP differences between the two devices using the criteria of the Association for the Advancement of Medical Instruments (AAMI), which require systolic and diastolic BP differences to be within ≤5 ± 8 (mean ± SD). RESULTS: Bland-Altman analysis showed wide limits of agreement (±~17 mmHg or greater) between finger-derived brachial and oscillometric BP. Both systolic and mean BP exhibited positive proportional biases (both P<0·05). Systolic BP differed significantly between devices (7·4 ± 17·7 mmHg, P<0·001), which did not meet the AAMI criteria. No mean bias was observed for diastolic BP (-1·5 ± 8·6 mmHg, P = 0·097), and the SD of ±8·6 mmHg is potentially acceptable given the finger signal may be expected to capture biological variability in BP. Mean BP showed poor concordance (3·7 ± 10·5 mmHg, P<0·001). CONCLUSIONS: These findings indicate that systolic and mean BP measurements made by brachial oscillometry do not agree with those from finger plethysmography. In contrast, diastolic BP values show acceptable agreement.

Compromised Cerebrovascular Regulation and Cerebral Oxygenation in Pulmonary Arterial Hypertension.

BACKGROUND: Functional cerebrovascular regulatory mechanisms are important for maintaining constant cerebral blood flow and oxygen supply in heathy individuals and are altered in heart failure. We aim to examine whether pulmonary arterial hypertension (PAH) is associated with abnormal cerebrovascular regulation and lower cerebral oxygenation and their physiological and clinical consequences. METHODS AND RESULTS: Resting mean flow velocity in the middle cerebral artery mean flow velocity in the middle cerebral artery (MCAvmean); transcranial Doppler), cerebral pressure-flow relationship (assessed at rest and during squat-stand maneuvers; analyzed using transfer function analysis), cerebrovascular reactivity to CO2, and central chemoreflex were assessed in 11 patients with PAH and 11 matched healthy controls. Both groups also completed an incremental ramp exercise protocol until exhaustion, during which MCAvmean, mean arterial pressure, cardiac output (photoplethysmography), end-tidal partial pressure of CO2, and cerebral oxygenation (near-infrared spectroscopy) were measured. Patients were characterized by a significant decrease in resting MCAvmean (P<0.01) and higher transfer function gain at rest and during squat-stand maneuvers (both P<0.05). Cerebrovascular reactivity to CO2 was reduced (P=0.03), whereas central chemoreceptor sensitivity was increased in PAH (P<0.01), the latter correlating with increased resting ventilation (R2=0.47; P<0.05) and the exercise ventilation/CO2 production slope (V˙E/V˙CO2 slope; R2=0.62; P<0.05) during exercise for patients. Exercise-induced increases in MCAvmean were limited in PAH (P<0.05). Reduced MCAvmean contributed to impaired cerebral oxygen delivery and oxygenation (both P<0.05), the latter correlating with exercise capacity in patients with PAH (R2=0.52; P=0.01). CONCLUSIONS: These findings provide comprehensive evidence for physiologically and clinically relevant impairments in cerebral hemodynamic regulation and oxygenation in PAH.

Hemodynamic variability and cerebrovascular control after transient cerebral ischemia.

We investigated if hemodynamic variability, cerebral blood flow (CBF) regulation, and their interrelationships differ between patients with transient ischemic attack (TIA) and controls. We recorded blood pressure (BP) and bilateral middle cerebral artery flow velocity (MCAv) in a cohort of TIA patients (n = 17), and age-matched controls (n = 15). Spontaneous fluctuations in BP and MCAv were characterized by spectral power analysis, and CBF regulation was assessed by wavelet phase synchronization analysis in the very low- (0.02-0.07 Hz), low- (0.07-0.20 Hz), and high-frequency (0.20-0.40 Hz) ranges. Furthermore, cerebrovascular CO2 reactivity was assessed as a second metric of CBF regulation by inducing hypercapnia with 8% CO2 inhalation followed by hyperventilation driven hypocapnia. We found that TIA was associated with higher BP power (group effect, P < 0.05), but not MCAv power (P = 0.11). CBF regulation (assessed by wavelet phase synchronization and CO2 reactivity) was intact in patients (all P ≥ 0.075) across both hemispheres (all P ≥ 0.51). Pooled data (controls and affected hemisphere of patients) showed that BP and MCAv power were positively correlated at all frequency ranges (R(2) = 0.20-0.80, all P < 0.01). Furthermore, LF phase synchronization index was a significant determinant of MCAv power (P < 0.05), while VLF and HF phase synchronization index, and TIA were not (all P ≥ 0.50). These results indicate that CBF stability and control is maintained in TIA patients, but BPV is markedly elevated. BPV attenuation may be an important therapeutic strategy for enhancing secondary stroke prevention in patients who suffer a TIA.