Tuba players reproduce a Valsalva maneuver while playing high notes.

Playing wind instruments requires expiratory efforts. Blowing low notes on a tuba means a low resistance to expiration while playing high notes requires a strenuous expiratory strain. The resulting high intrathoracic pressure may reproduce a Valsalva maneuver. Ten tuba players were asked to blow medium loud long (15 seconds) notes at three different pitches (low, middle, and high) and to perform Valsalva maneuvers at 10, 40, and 60 mmHg. Blood pressure (BP) was measured continuously with a Finapres monitor. The four classic phases of the Valsalva maneuver were reproduced with the notes. The expiratory effort produced systolic BP and pulse pressure falls reaching about 24 mmHg with the high note or the Valsalva 60. BP and pulse pressure falls were linearly related to stroke volume reductions. Reflex heart rate (HR) changes were inversely related to BP falls, with maximal increases for the high notes (24 beats/minute) and Valsalva 60 (33 beats/minute). High baroreflex sensitivity was associated with a high HR response. Total peripheral resistance was reflexly elevated to counteract cardiac output reductions. During rebreathing, BP overshoots reached 30 mmHg for the high note and 53 mmHg for the Valsalva 60. Altogether, these findings indicate that blowing notes on a tuba reproduces the cardiovascular changes seen with a Valsalva maneuver with the effects of blowing high notes being close to a classic (40 mmHg) Valsalva maneuver. In addition, the baroreflex sensitivity might be a predictor of the ability to surmount the BP intolerance that could occur during wind instrument playing.

Short-term blood pressure and heart rate variability in congenital central hypoventilation syndrome (Ondine's curse).

The effect of CCHS (congenital central hypoventilation syndrome, or Ondine's curse) on short-term BP (blood pressure) and HR (heart rate) variability was evaluated in 16-year-old subjects presenting a form of CCHS requiring night ventilatory assistance. The 12 patients were compared with 12 age- and gender-matched healthy volunteers. Recordings were obtained during daytime while the subjects were breathing spontaneously. Continuous BP was measured with a Finapres device in the supine, head-up tilt and standing positions. The manoeuvre of actively standing was also analysed. HR levels were elevated in CCHS subjects at supine rest (+23%) with a reduced HR overall variability (-88%). The low- and high-frequency components of HR variability were affected. BP levels were preserved at rest, but the manoeuvres demonstrated a limited capacity to elevate BP. There was no overshoot in BP during the manoeuvre of actively standing, and steady standing BP levels in patients were not higher than supine BP levels as usually observed in healthy controls. The spontaneous baroreflex sensitivity estimated using the sequence technique or the cross-spectral analysis fell in the patients to approx. one-third of the sensitivity estimated in the healthy controls whatever the position. This cardiovascular profile suggests a predominant vagal dysfunction with signs of vagal withdrawal and baroreflex failure, and relative preservation of the cardiac and vascular sympathetic function. It is likely that the impaired ontogeny of the visceral reflexes, considered now to cause CCHS syndrome, includes the baroreceptive pathway and mainly its vagal component.

Stroke volume monitored by modeling flow from finger arterial pressure waves mirrors blood volume withdrawn by phlebotomy.

Rate-controlled blood withdrawal was used to reduce cardiac preload and consequently stroke volume in patients with normal cardiac function. Twelve patients with asymptomatic hereditary hemochromatosis, undergoing regular phlebotomy therapy, volunteered for the study. An average volume of 375 ml was withdrawn in an average period of 6.4 min. Finger pressure was continuously measured by a Finometer device which includes the Beatscope software for deriving the stroke volume from the blood pressure waveform. Blood withdrawal resulted in reduction of the stroke volume estimates (from 94.0 +/- 5.2 to 80.7 +/- 5.3, P < 0.05) together with a reduced pulse pressure (from 53.0 +/- 3.5 to 47.1 +/- 3.2, P < 0.05). No significant changes in heart rate (75.2 +/- 3.7 versus 78.3 +/- 4.5 beats/min) were observed. Calculated cardiac output was reduced while calculated total peripheral resistance was elevated after blood withdrawal. Beat-to-beat analysis demonstrated a significant linear regression between most of the hemodynamic indices and the volume withdrawn. The highest correlation coefficients were found for the stroke volume (0.88 +/- 0.01, P < 0.001) and the pulse pressure (0.80 +/- 0.04, P < 0.001) corresponding also to the highest slopes for the lines relating these measures to the relative blood volume withdrawn. The non-invasive estimation of finger blood pressure can be used to derive simple on-line indices (pulse pressure, stroke volume using the Modelflow) of cardiac preload, which are of major interest in the monitoring of cardiovascular status.

Comparison of various techniques used to estimate spontaneous baroreflex sensitivity (the EuroBaVar study).

This study compared spontaneous baroreflex sensitivity (BRS) estimates obtained from an identical set of data by 11 European centers using different methods and procedures. Noninvasive blood pressure (BP) and ECG recordings were obtained in 21 subjects, including 2 subjects with established baroreflex failure. Twenty-one estimates of BRS were obtained by methods including the two main techniques of BRS estimates, i.e., the spectral analysis (11 procedures) and the sequence method (7 procedures) but also one trigonometric regressive spectral analysis method (TRS), one exogenous model with autoregressive input method (X-AR), and one Z method. With subjects in a supine position, BRS estimates obtained with calculations of alpha-coefficient or gain of the transfer function in both the low-frequency band or high-frequency band, TRS, and sequence methods gave strongly related results. Conversely, weighted gain, X-AR, and Z exhibited lower agreement with all the other techniques. In addition, the use of mean BP instead of systolic BP in the sequence method decreased the relationships with the other estimates. Some procedures were unable to provide results when BRS estimates were expected to be very low in data sets (in patients with established baroreflex failure). The failure to provide BRS values was due to setting of algorithmic parameters too strictly. The discrepancies between procedures show that the choice of parameters and data handling should be considered before BRS estimation. These data are available on the web site (http://www.cbi.polimi.it/glossary/eurobavar.html) to allow the comparison of new techniques with this set of results.

Elastin mutation is associated with a reduced gain of the baroreceptor--heart rate reflex in patients with Williams syndrome.

Microdeletion of chromosome 7q, encompassing the elastin locus, has been identified in patients with Williams syndrome (WS). This study tested the hypothesis that loss of medial elastin affects the discharge of baroreceptors and consequently the baroreflex sensitivity (BRS). Eight untreated patients with WS (14.8 +/- 2.4 y, m +/- SEM) were compared to 8 healthy subjects (15.1 +/- 2.3 y). Blood pressure (BP) was recorded using a Finapres monitor in the supine position. Systolic BP (SBP) levels were 117.8 +/- 4.4 mmHg in WS compared to 110.9 +/- 5.7 in controls (ns). Pulse rate (PR, taken as a surrogate for heart rate) was higher in the WS (89.6 +/- 1.0 vs 74.1 +/- 2.3 beats/min in controls, P < 0.01). The variance (total power) of PI variability was reduced in WS subjects. The amplitudes of the low frequency (LF, 0.1 Hz) and high frequency (HF, respiratory) PI component (modulus) were reduced in WS (210.5 +/- 4.3 vs 34.6 +/- 2.6 ms, P = 0.02 for LF, for HF). The gain of the SBP-PI transfer function was diminished in the low frequency (LF, 0.1 Hz) and the HF range as well (5.8 +/- 0.7 vs 12.1 +/- 1.8 ms/mmHg for LF, P < 0.01 and 6.2 +/- 1.0 vs 21.7 +/- 4.6 ms/mmHg for HF, P < 0.01). The BRS obtained with the sequence technique was also reduced in WS (8.2 +/- 0.9 vs 21.5 +/- 2.9 ms/mm Hg in controls, P < 0.001). The percent of beats involved in baroreflex sequences observed in WS was also diminished to 20% compared to 48% in controls (P < 0.001). In conclusion a BRS reduction associated with a PR elevation was observed in normotensive WS subjects. It is likely abnormal elastic fiber assembly at the arterial level alters baroreceptor discharges.