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PubMed1993

The Bergen Blood Pressure Study: blood pressure changes, target organ damage and mortality in subjects with high and low blood pressure over 27 years.

Based on the Bergen population screening in 1963-64, 344 married couples (688 subjects), then aged 30-69 years, were included for studies in families with a history of hypertension or normotension. In 1990 430 subjects were available to a follow-up examination. The present paper describes 27-year mortality, blood pressure (BP) changes, cardiovascular disease and target organ damage in this population. In males who were hypertensive by the 1963-64 screening BP, the all-cause 27-year mortality was three times higher than in initially normotensive males (p < 0.05). From 1963-64 to 1990, the systolic BP was generally increased, whereas the diastolic BP was decreased in initially hypertensive and increased in initially normotensive subjects. In subjects who were hypertensive in 1963-64, the relative risk of hypertension in 1990 was more than seven times higher than in initially normotensive subjects (p < 0.05), cardiovascular events were reported more often (p < 0.001), and the mean electrocardiographic left ventricular voltage was higher (p < 0.01). Proteinuria was more frequent in initially hypertensive than normotensive males (p < 0.01). In summary, hypertension defined by a single BP recording at the 1963-64 screening was a risk factor for hypertension, cardiovascular morbidity and, for males, all-cause mortality 27 years later. With respect to offspring studies, our findings substantiate the classification of hypertensive and normotensive families. From 1963-64 to 1990, the BP status had changed in several couples, and the long observation period seems mandatory if a reliable definition of the family history of hypertension or normotension is to be obtained.

Adult↗
PubMed1987

[Blood pressure in children and adolescents aged 4 to 18. Correlation of blood pressure values with age, sex, body height, body weight and skinfold thickness (Essen Blood Pressure Study)].

1,165 randomly selected school children/adolescents and 306 preschool children living in Essen, West Germany, were examined for their systolic and diastolic (phase IV and V) blood pressure (BP), height, weight, and skinfold thickness. These are 97% of the original random sample school children/adolescents and 70.7% of the preschool children (under seven years old). Ages ranged from 4 to 18 years with 51% male and 49% female. Examination of the school children was performed in 20 different schools representative for the various types of school found in this city. BP was found to increase with age. In boys, the increase was significantly steeper during adolescence than in the preadolescence period (p less than 0.001). Adolescent boys had higher BP values than adolescent girls. In children younger than 10 years BP was similar to that reported in the Bogalusa study. The evaluation of partial correlation coefficients (rpart) identified body weight as the most important determinant of systolic BP (rpart = 0.25) and diastolic BP (rpart = 0.17) (p less than 0.0001).

Adolescent↗
PubMed1987

Effect of alveolar pressure on pulmonary artery pressure in chronically hypoxic rats.

The effect on pulmonary artery pressure of a rise in alveolar pressure differed in chronically hypoxic rats (10% O2 for 3-5 weeks) compared with control rats. Chronically hypoxic rats have newly muscularised walls in arterioles in the alveolar region. Isolated lungs of chronically hypoxic and control rats were perfused with blood under conditions in which alveolar pressure was greater than left atrial pressure during both normoxia and hypoxia. Alveolar pressure was the effective downstream pressure. Pressure-flow lines were measured at low and high alveolar pressure (5 and 15 mmHg). During normoxia pressure-flow lines of chronically hypoxic rats had a steeper slope (higher resistance) and greater extrapolated intercept on the pressure axis (effective downstream pressure) than control rats. In both groups of rats the change from low to high alveolar pressure during normoxia caused an approximately parallel shift in the pressure-flow line similar to the change in alveolar pressure. During hypoxia, which led to an increase in slope and intercept in both groups of rats, the effect of a rise in alveolar pressure differed in chronically hypoxic from control rats. In control rats there was a small parallel shift in the pressure-flow line that was much less than the increase in alveolar pressure; in chronically hypoxic rats there was a large parallel shift in the pressure-flow line that was greater than the increase in alveolar pressure. Thus in chronically hypoxic rats hypoxic vasoconstriction probably occurred mainly in muscular alveolar vessels, whereas in control rats it probably occurred upstream in extra-alveolar vessels. At constant blood flow the relation between pulmonary artery pressure and alveolar pressure was measured while alveolar pressure was reduced from approximately 15 mmHg to zero during both normoxia and hypoxia. In control and chronically hypoxic rats the slope of this line was less than 1. At an alveolar pressure of 2-3 mmHg there was an inflection point below which the line was nearly horizontal in control but negative in chronically hypoxic rats. During hypoxia the inflection point increased in control but not in chronically hypoxic rats, whereas the preinflection slope became negative. Apart from a rise in pulmonary artery pressure at all values of alveolar pressure, which occurred in both groups of rats, there was no change in the form of the curve in chronically hypoxic rats during hypoxia. These results also suggest constriction of extra-alveolar vessels in control rats and alveolar vessels in chronically hypoxic rats during hypoxia.

Animals↗
PubMed1997

Tracheal gas insufflation during pressure-control ventilation: effect of using a pressure relief valve.

OBJECTIVES: Pressure-control ventilation minimizes alveolar overdistention by limiting peak airway pressure, but a consequence of this pressure limitation may be a reduction in tidal volume with subsequent hypercarbia. Tracheal gas insufflation (TGI) can be used in combination with pressure-control ventilation to augment CO2 elimination. During pressure-control ventilation with continuous TGI, we observed that peak airway pressure increased above the set inspiratory pressure. Based on this observation, we investigated the ability of the pressure-control ventilator circuit to compensate for continuous TGI and the effect of insertion of a pressure relief valve to eliminate over-pressurization. SETTING: University research laboratory. DESIGN: Using an artificial lung model, we studied the effects of continuous TGI with varying catheter flows (0, 2, 6, and 10 L/ min); ventilator frequencies (10 and 20 breaths/min); inspiratory duty cycles (0.33, 0.50, and 0.67); lung compliance (0.01, 0.02, and 0.04 L/cm H2O); and airway resistance (5, 20, and 50 cm H2O/L/sec) on: a) peak airway pressure; b) total inspiratory tidal volume; c) ventilator-derived tidal volume; and d) intrapulmonary pressure at end-exhalation (auto-PEEP). Tests were performed with and without a pressure relief valve whose threshold "pop-off" pressure was adjusted to match the set inspiratory pressure (35 cm H2O) for a total of 432 experimental conditions. MEASUREMENTS AND MAIN RESULTS: Our data demonstrate that pressure-control ventilation augmented with continuous TGI can increase peak airway pressure above set inspiratory pressure due to delivery of a higher than intended tidal volume. Predisposing conditions include catheter flow rates of 6 and 10 L/min, long inspiratory time, low compliance, and low resistance. With the pressure relief valve, peak airway pressure was maintained at the set inspiratory pressure and total inspiratory tidal volume remained constant. CONCLUSION: A pressure relief valve is a necessary adjunct to maintain peak airway pressure at set inspiratory pressure and keep total inspiratory tidal volume constant when continuous TGI is administered in conjunction with pressure-control ventilation.

Airway Resistance↗
PubMed2004

Relationship between ambulatory blood pressure and follow-up clinic blood pressure in elderly patients with systolic hypertension.

BACKGROUND: Patients with elevated clinic blood pressure and normal ambulatory blood pressure have a better prognosis than patients with sustained ambulatory hypertension, and may not have to be treated with antihypertensive drugs. On the contrary, current guidelines emphasize repeated clinic blood pressure measurements for the initiation of antihypertensive therapy. OBJECTIVE: To examine the relationship between ambulatory blood pressure at baseline and clinic blood pressure after 6 months of follow-up in untreated hypertensive patients, and the relationships of these pressures with the subsequent incidence of cardiovascular events. METHODS: Patients who were > or = 60 years old, with systolic clinic blood pressure of 160-219 mmHg and diastolic pressure < 95 mmHg, participated in the Systolic Hypertension in Europe trial. The relationship between ambulatory blood pressure at baseline and clinic blood pressure after 6 months of follow-up was examined in 295 patients enrolled in the Ambulatory Blood Pressure Monitoring substudy and randomized to the placebo arm, and who were still on double-blind treatment and not taking other antihypertensive drugs after 6 months follow-up. RESULTS: Age averaged 70 +/- 6 years, 41% were men, and baseline daytime ambulatory blood pressure was 152 +/- 16/84 +/- 10 mmHg; clinic blood pressure decreased from 173 +/- 10/86 +/- 6 mmHg at baseline to 163 +/- 20/85 +/- 9 mmHg at month 6. Systolic daytime ambulatory blood pressure at baseline and systolic clinic blood pressure at month 6 were considered normal if < 140 mmHg. Of the 74 patients with normal systolic daytime ambulatory blood pressure at baseline, only seven (9.5%) had a normal systolic clinic blood pressure during follow-up. Conversely, of the 24 patients with normal follow-up clinic blood pressure, only seven (29%) had a normal systolic daytime ambulatory blood pressure at baseline. The incidence of cardiovascular events beyond the 6-month visit was significantly related to baseline ambulatory blood pressure but not to follow-up clinic pressure. CONCLUSIONS: Baseline daytime ambulatory blood pressure and follow-up clinic blood pressure do not identify the same patients for antihypertensive treatment. Baseline ambulatory pressure is a better predictor of cardiovascular events than follow-up clinic pressure.

Aged↗
PubMed2004

Positive pressure versus pressure support ventilation at different levels of PEEP using the ProSeal laryngeal mask airway.

We compared positive pressure ventilation with pressure support ventilation at different levels of positive end expiratory pressure (PEEP) using the ProSeal laryngeal mask airway (PLMA). Forty-two anaesthetized adults (ASA 1-2, aged 19 to 63 years) underwent positive pressure ventilation and then pressure support ventilation each with PEEP set at 0, 5 and 10 cmH2O in random order. Pressure support ventilation was with the inspired tidal volume (VTInsp) set at 7 ml/kg and the respiratory rate adjusted to maintain the end-tidal CO2 (ETCO2) at 40 mmHg. Pressure support ventilation was with pressure support set at 5 cmH2O above PEEP and initiated when inspiration produced a 2 cmH2O reduction in airway pressure. Tidal volumes were similar during positive pressure and pressure support ventilation with PEEP, but were higher for the former without PEEP Respiratory rate and peak inspiratory flow rate were higher during pressure support than positive pressure ventilation (all P < 0.001). Peak airway pressure (Ppaw), mean airway pressure (Mpaw), peak expiratory flow rate, and expired airway resistance were lower during pressure support than positive pressure ventilation (all P < 0.001). With PEEP set at 10 cmH2O, ETCO2 was lower for pressure support than positive pressure ventilation. During positive pressure ventilation, there was an increase in Ppaw, Mpaw and dynamic compliance (Cdyn) with increasing levels of PEEP (all P < 0.01). During pressure support ventilation, there was an increase in inspired and expired tidal volume, Ppaw, peak inspiratory and expiratory flow rates and Cdyn, and a reduction in ETCO2, work of breathing, and expired airway resistance with increasing levels of PEEP (all P < 0.01). There were no differences in SpO2, non-invasive mean arterial pressure, heart rate or leak fraction. We conclude that pressure support ventilation provides equally effective gas exchange as positive pressure ventilation during PLMA anaesthesia with or without PEEP at the tested settings. During pressure support, PEEP increases ventilation and reduces work on breathing without increasing leak fraction.

Adult↗
PubMed2005

Noninvasive assessment of local pulse pressure: importance of brachial-to-radial pressure amplification.

The advocated SphygmoCor procedure uses a radial-to-aorta transfer function with calibration on brachial instead of radial artery pressure to assess the central pulse pressure. We compared these values with carotid artery pulse pressures obtained from a validated calibration method, assuming mean minus diastolic blood pressure constant throughout the large artery tree. From 44 healthy subjects (21 males; 22 to 68 years) pressure waves were obtained at the radial, brachial, and carotid artery with applanation tonometry. Using the calibration method, radial and carotid artery pressures were assessed from brachial artery waves and pressures. The effect of brachial-to-radial pulse pressure amplification, brachial pulse pressure, mean pressure, age, gender, height, body mass index, and smoking on differences between the 2 methods was assessed. Brachial artery pressure was 118+/-12/72+/-10 mm Hg. SphygmoCor central pulse pressure was 9.7+/-4.6 mm Hg lower (P<0.001) than the carotid artery pulse pressure (33.0+/-6.8 versus 42.7+/-8.9 mm Hg). The difference between the 2 methods strongly depended (P<0.001) on brachial-to-radial artery pulse pressure amplification (5.8+/-5.1 mm Hg; 12+/-11%) and less on brachial artery pulse pressure (P=0.005). After calibration of the radial pressure wave with radial instead of brachial artery pressures, the difference between SphygmoCor central pulse pressure and carotid pulse pressure decreased with 4 mm Hg. The advocated SphygmoCor procedure systematically underestimates the central pulse pressure with brachial-to-radial pulse pressure amplification as important determinant. Therefore, calibration of radial artery pressure waves on brachial artery pressures should be avoided. The underestimation of central aortic pulse pressure caused by the radial-to-aorta transfer function itself is much less than previously reported.

Adult↗
PubMed1987

A physiological role for pressure-dependent renin release in long-term blood pressure control.

The relationship between pressure-dependent renin release and long-term blood pressure was studied in 14 conscious dogs on a normal salt diet. Stimulus-response curves were obtained by a controlled reduction of renal artery pressure in 5 or 10 mm Hg steps down to 70 mm Hg. Pressure-dependent renin release was characterized by a threshold pressure, a plateau above threshold pressure, and a steep slope below the threshold pressure. In each dog long-term blood pressure was higher than threshold pressure. Threshold pressure and slope were found to describe more than 90% of long-term blood pressure variability between conscious dogs. The following findings suggest that an on-off switch of pressure-dependent renin release stabilizes long-term blood pressure above the threshold pressure: (1) The intermittent activation of pressure-dependent renin release due to physiological variations in arterial blood pressure induced changes in plasma renin activity by as much as 300%. (2) The individual difference between threshold pressure and long-term blood pressure was highly dependent on the slope. (3) A systemic blockade of the renin-angiotensin system by converting-enzyme inhibition resulted in a slope-dependent fall of long-term blood pressure. (4) A spontaneous shift of threshold pressure was accompanied by equivalent changes in arterial blood pressure. Taken together, our results provide evidence for a major role of pressure-dependent renin release in the long-term control of blood pressure in conscious dogs. A chronic resetting of threshold pressure may be an important mechanism in the pathogenesis of hypertension.

Animals↗
PubMed1998

Clinical evaluation of tracheal pressure estimation from the endotracheal tube cuff pressure.

OBJECTIVE: Air flow through an endotracheal tube causes a pressure drop across the tube. This pressure drop creates a difference between air pressure measured in the trachea and the pressure measured in the breathing circuit, which can lead to errors when calculating pulmonary mechanics and when setting ventilators. We have developed a method of estimating tracheal pressure from the pressure in the endotracheal tube cuff and tested this system in clinical trials. METHODS: Pressure measurement ports were placed between the Y piece of the ventilator circuit and the ETT connector, in the trachea at the carinal end of the ETT, and in the ETT cuff inflation line. Tracheal pressures and cuff pressures were found at end-inspiration and end-expiration (no flow states) and used to define a linear relationship between cuff pressure and tracheal pressure. Using the estimated tracheal pressure (Ptrach) and the measured pressure at the Y piece of the breathing circuit (PY), the pressure drop across the ETT was found as a function of flow through the tube. Tracheal pressure was then calculated from the flow-dependent pressure drop and PY. Tests of this system were performed in six patients in the operating room and six patients in the intensive care unit. RESULTS: The flow-based tracheal pressure estimates were within 0.7 +/- 0.4 cm H2O of actual tracheal pressure (mean +/- SD). At peak inspiratory pressure the difference averaged 0.5 +/- 0.3 cm H2O. The difference between our estimate of tracheal pressure and actual tracheal pressure was always less than 1 cm H2O. CONCLUSION: The flow-based tracheal pressure estimates were accurate during intermittent spontaneous breathing, but not during spontaneous breathing or with a poorly inflated cuff. The estimates were more immune to noise than the cuff-based estimates of tracheal pressure. The estimates of tracheal pressure measured from the ETT cuff should be accurate enough for clinical use in the operating room.

Adolescent↗
PubMed1998

Intracranial pressure waveform analysis: computation of pressure transmission and waveform shape indicators.

We studied transmission of arterial blood pressure to intracranial pressure by observing how the two pressure waveforms varied from baseline conditions to after postural change or jugular compression. Such experiments may lead to pressure waveform-based estimates of intracranial compliance. Using a single database of arterial blood pressure, central venous pressure, and intracranial pressure waveforms collected during baseline, jugular compresison, and head-elevated conditions from six Yucatan minipigs, we computed several numerical indicators of waveform shape to find an estimator of intracranial compliance. Of these indicators, two were based on the Fourier-decomposition of all three waveforms, and one was based on a new method for approximating the systolic slope of the intracranial pressure waveform. We computed amplitude transfer functions for the first six harmonics of the Fourier spectrum, treating intracranial pressure as system output and independently treating arterial blood pressure and central venous pressure as system inputs. Using these same inputs and outputs, we computed a single quotient based on the Fourier coefficients of the first six harmonics of the input and output waveforms. Finally, applying a Gaussian high-pass filter, we computed systolic slope approximations for all intracranial pressure wave cycles contained in a single respiratory cycle. Our third indicator was the mean-normalized variation of the slope approximations over a respiratory cycle. We studied how each composite at baseline varied with baseline mean intracranial pressure and how each composite changed from baseline as a result of a physical manipulation. Our analysis suggests that the composite based on respiratory variation of systolic slope approximations was positively correlated with mean intracranial pressure during baseline. The quotient based on Fourier coefficients with arterial blood pressure input seemed to increase from baseline to jugular compression. Composites that treated central venous pressure as input were both less correlated with mean intracranial pressure during baseline and exhibited less predictable changes from baseline to a physical manipulation than their counterparts that used arterial blood pressure as input. However, none of these apparent trends was statistically significant. The lack of statistically significant results may be due to the nature of the composites and/or the small sample size (n = 6). However, we hope this study stimulates further investigation of both central venous pressure-to-intracranial pressure (in addition to arterial blood pressure-to-intracranial pressure) transfer and automated computation of intracranial pressure waveform systolic slope. Such research may lead to noninvasively determined estimators of intracranial compliance.

Animals↗
PubMed2006

Positive end-expiratory pressure and pressure support in peripheral airways obstruction : work of breathing in intubated children.

OBJECTIVES: Children with peripheral airways obstruction suffer the negative effects of intrinsic positive end-expiratory pressure: increased work of breathing and difficulty triggering assisted ventilatory support. We examined whether external positive end-expiratory pressure to offset intrinsic positive end-expiratory pressure decreases work of breathing in children with peripheral airways obstruction. The change in work of breathing with incremental pressure support was also tested. DESIGN AND SETTING: Prospective clinical trial in a pediatric intensive care unit. PATIENTS: Eleven mechanically ventilated, spontaneously breathing children with peripheral airways obstruction. INTERVENTIONS: Work of breathing (using pressure-rate product as a surrogate) was measured in three tiers: (a) Increasing pressure support over zero end-expiratory pressure. (b) Increasing applied positive end-expiratory pressure and fixed pressure support. The level of applied positive end-expiratory pressure at which pressure-rate product was least determined the compensatory positive end-expiratory pressure. (c) Increasing pressure support over compensatory (fixed) positive end-expiratory pressure. MEASUREMENTS AND RESULTS: Increases in pressure support alone decreased pressure-rate product from mean 724+/-311 to 403+/-192 cmH2O/min. Applied positive end-expiratory pressure alone decreased pressure-rate product from mean 608+/-301 to 250+/-169 cmH2O/min. The lowest pressure-rate product (136+/-128 cmH2O/min) was achieved using compensatory positive end-expiratory pressure (12+/-4 cmH2O) with pressure support 16 cmH2O. CONCLUSIONS: For children with peripheral airways obstruction who require assisted ventilation, work of breathing during spontaneous breaths is decreased by the application of either compensatory positive end-expiratory pressure or pressure support.

Airway Obstruction↗
PubMed1994

Timing of pressure release affects power of breathing and minute ventilation during airway pressure release ventilation.

OBJECTIVES: To evaluate the effects of interference between spontaneous and mechanical breaths on the power of breathing (rate at which work is done) and ventilatory support during airway pressure release ventilation. DESIGN: Multitrial tests under simulated clinical conditions using a mechanical respiratory system model. SETTING: A research laboratory at a university medical center. INTERVENTIONS: Simulated spontaneous breathing augmented with continuous positive airway pressure and airway pressure release ventilation. Variation in synchrony between spontaneous breathing and mechanical ventilation was accomplished by adjusting the time lag between detection of the spontaneous inspiration and the airway pressure release from 0 to 3 secs in increments of 0.25 secs. MEASUREMENTS AND MAIN RESULTS: Pressures and volumes were measured at the inlet of the lung and chest wall compartment of the respiratory system model. Pressure and volume changes measured at the inlet of the chest wall compartment were used to generate pressure/volume loops and to calculate the power of the spontaneous breathing. Minute ventilation was greater (p < .01) during all airway pressure release ventilation settings compared with those values of continuous positive airway pressure. Nonconflicting airway pressure release ventilation was associated with a higher minute ventilation (p < .001) than asynchronous airway pressure release ventilation. When spontaneous inspiration was synchronous with restoration of continuous positive airway pressure, minute ventilation was lower (p < .001) than during nonconflicting airway pressure release ventilation settings. Power of spontaneous breathing was highest when airway pressure release and spontaneous inspiration coincided, and lowest when spontaneous inspiration and restoration of continuous positive airway pressure were synchronized. Power of breathing was significantly lower during nonconflicting than during asynchronous airway pressure release ventilation (p < .01). No difference was observed between the power of spontaneous breathing and airway pressure release ventilation either with spontaneous expiration synchronized with airway pressure release or with nonconflicting airway pressure release ventilation. When calculated per liter of ventilation, power of spontaneous breathing was significantly lower (p < .01) during all airway pressure release ventilation settings compared with continuous positive airway pressure. CONCLUSION: Asynchronous airway pressure release may increase the power of spontaneous breathing and reduce effective mechanical ventilatory support during airway pressure release ventilation. A clinical study is required to assess the effect of synchronous and asynchronous interference between spontaneous and mechanical breaths during airway pressure release ventilation.

Airway Resistance↗
PubMed2003

Higher systemic arterial pressures are rarely associated with cerebral perfusion pressure deterioration in brain injury.

BACKGROUND: A computerized monitoring system was developed and utilized to evaluate the relationship between mean arterial pressure and intracranial pressure and its effect on cerebral perfusion pressure to determine how best to maximize cerebral perfusion pressure. METHODS: The monitoring system recorded mean arterial pressure and intracranial pressure, the values of which were used to calculate cerebral perfusion pressure. We developed the program for and utilized a "moving window" regression analysis to divide the total monitoring period into 2-hour overlapping epochs. The relationship between mean arterial pressure and intracranial pressure was then analyzed in each 2-hour epoch and classified into Types A, B, C, and D epochs, each with clinical significance. Type A epochs involved intracranial pressure increasing more than mean arterial pressure and resulted in deterioration of cerebral perfusion pressure. Type B epochs involved mean arterial pressure increasing more than intracranial pressure and resulted in an increase of perfusion pressure. Type C epochs involved mean arterial pressure increasing and intracranial pressure decreasing and also resulted in an increase in perfusion pressure. Type D epochs had no statistically significant relationship between mean arterial pressure and intracranial pressure. RESULTS: Forty-five patients with various pathologies were studied. The majority (n = 35) were patients with severe brain injury. Of 5,694 total hours monitored and 22,776 total epochs analyzed, 1.5% epochs were Type A, 5.9% were Type B, 2.1% were Type C, and 90.5% were Type D. CONCLUSION: In most patients, most of the time, increasing mean arterial pressure did not worsen cerebral perfusion pressure.

Aged↗
PubMed1992

Effect on sleep--but not on blood pressure--of nocturnal non-invasive blood pressure monitoring.

OBJECTIVE: Nocturnal non-invasive ambulatory blood pressure monitoring inevitably causes an undesirable external stimulus due to the cuff pressure and, for some monitors, disturbing compressor sound. The objective of the present study was to determine whether non-invasive automated blood pressure monitoring during sleep provokes arousal and changes in blood pressure and/or heart rate. DESIGN: Sleep response and blood pressure reaction during and immediately after blood pressure monitoring were studied by means of simultaneous electroencephalography and blood pressure recordings. METHODS: Blood pressure and electroencephalogram were recorded simultaneously in 24 subjects (10 hypertensive, 14 normotensive). Blood pressure was registered with a non-invasive automatic blood pressure monitor every 20 min. Inflation and deflation of the cuff were registered on one of the electroencephalogram channels by means of a small pressure meter attached to the cuff. For each subject, blood pressure during uninterrupted sleep was compared with that during arousal provoked by the recordings. RESULTS: Blood pressure recording caused an arousal in 67% of the recordings. During 33% of the recordings, sleep continued. Neither systolic nor diastolic blood pressure differed significantly for recordings during 'uninterrupted sleep' when compared with arousal. Heart rate was significantly faster during arousal than during uninterrupted sleep. Analysed separately, hypertensive subjects showed an overall blood pressure response close to that of normotensive subjects. There was a significant trend towards lower blood pressure, parallel with deeper sleep. CONCLUSIONS: The results of this study show that non-invasive ambulatory blood pressure monitoring during sleep accurately records basal blood pressure and can distinguish blood pressure during superficial sleep from blood pressure during deep sleep. Sleep is often disturbed by blood pressure monitoring but, irrespective of whether recording provokes arousal, monitored blood pressure is the same.

Adult↗
PubMed1997

Increased intra-abdominal pressure and cardiac filling pressures in obesity-associated pseudotumor cerebri.

OBJECTIVES: To determine whether intra-abdominal pressure (as estimated from urinary bladder pressure) is elevated in patients with central obesity (as measured by sagittal abdominal diameter) and pseudotumor cerebri and whether this increased intra-abdominal pressure is associated with increased pleural pressure and cardiac filling pressure, implying a resistance to venous return from the brain. DESIGN: Nonrandomized, prospective. SETTING: University hospital, operating room. MAIN OUTCOME MEASUREMENTS: Intracranial pressure, urinary bladder pressure, sagittal abdominal diameter, transesophageal pleural pressure, central venous pressure, pulmonary artery pressure, and pulmonary artery occlusion pressure. SUBJECTS: Six women with pseudotumor cerebri (one with CSF leak, one with lumboperitoneal shunt). RESULTS: Urinary bladder pressure (22 +/- 3 cm H2O) and sagittal abdominal diameter (29 +/- 3 cm) were significantly elevated in these patients with elevated intracranial pressure (293 +/- 80 mm H2O) compared with a previously reported group of nonobese control patients. The transesophageal pleural pressure (15 +/- 10 mm Hg), central venous pressure (20 +/- 6 mm Hg), mean pulmonary artery pressure (31 +/- 6 mm Hg), and pulmonary artery occlusion pressure (21 +/- 7 mm Hg) were all markedly elevated compared with published normal values and with previous data from obese patients without pseudotumor cerebri. CONCLUSIONS: These data support the hypothesis that central obesity raises intra-abdominal pressure, which increases pleural pressure and cardiac filling pressure, which impede venous return from the brain, leading to increased intracranial venous pressure and increased intracranial pressure associated with pseudotumor cerebri.

Abdomen↗
PubMed1998

Relationship between ambulatory blood pressure monitoring and response of blood pressure in male hypertensive adolescents to exercise.

BACKGROUND: High blood pressure in the young has been related to the development of hypertension in adults; hence the importance of identifying adolescents with the risk of developing it.OBJECTIVE: To investigate the relationship between 24 h ambulatory blood pressure monitoring and the response of blood pressure in adolescents to exercise. DESIGN: A prospective and cross-sectional study. METHODS: We classified 101 men aged 13-18 years as obese hypertensive, lean hypertensive, obese normotensive, and lean normotensive. Mean blood pressure and variability were measured with ambulatory blood pressure monitoring, and expressed as 24 h, awake, and sleeping periods. Treadmill tests were also performed. RESULTS: Hypertensives and obese normotensives had higher ambulatory blood pressure monitoring values (P< 0.0001). Systolic blood pressure during sleep in obese subjects was significantly higher than that in lean usbjects (119.9 +/- 9 versus 113.6 +/- 8 mmHg, P < 0.001, obese hypertensives versus lean hypertensives; and 113.6 +/- 2 versus 103.0 +/- 2 mmHg, P < 0.002, obese normotensives versus lean normotensives) and nocturnal drop of systolic blood pressure was lower in obese subjects. We found a significant correlation between systolic blood pressure during ambulatory blood pressure monitoring and systolic blood pressure during moderate and maximal exercise for all periods (P < 0.0001). Blood pressure variability during awake period was higher in subjects with maximum exercise systolic blood pressure >/= 200 mmHg (7.4 +/- 2 versus 6.4 +/- 2%, P < 0.01).CONCLUSION: Systolic blood pressure measured by ambulatory blood pressure monitoring is related to response of systolic blood pressure to exercise and ambulatory blood pressure monitoring can identify groups of subjects at greater than normal risk through their higher blood pressure during sleep. Greater than normal blood pressure variability in adolescents is an indicator of the risk of reaching abnormal exercise values of systolic blood pressure. Higher casual blood pressure than ambulatory blood pressure monitoring values for adolescents should be considered abnormal.

Journal Article↗
PubMed1985

Coronary sinus occlusion pressure and its relation to intracardiac pressure.

The hemodynamic components of coronary sinus (CS) occlusion pressure in humans have not been well described. If no other outflow for venous blood were present, then after acute occlusion of the coronary sinus the pressure would increase and equal aortic pressure. However, if thebesian vein drainage between the left ventricle and the coronary veins has an important role in humans, then CS occlusion pressure might reflect left ventricular (LV) pressure through transmitted LV pressure or intramyocardial pressure. To study this relation, 27 patients who underwent routine diagnostic cardiac catheterization were evaluated. Occlusion was accomplished by sudden inflation of a No. 7Fr balloon-tipped catheter placed into the CS. LV end-diastolic pressure and end-diastolic CS occlusion pressure were simultaneously recorded at rest. LV end-diastolic pressure (16.7 +/- 5.6 mm Hg) was not significantly different from end-diastolic CS occlusion pressure (15.9 +/- 5.4 mm Hg). LV end-diastolic and end-diastolic CS occlusion pressures were positively correlated (p less than 0.001) over the entire range of pressures (9 to 27 mm Hg). In contrast, systolic CS occlusion pressure was significantly lower than LV systolic pressure and unrelated to right-sided heart pressures. It is concluded that in humans, end-diastolic CS occlusion pressure closely parallels LV end-diastolic pressure, and measurement of CS occlusion pressure to assess LV end-diastolic pressure may have clinical use. These findings also suggest the existence of hemodynamically important thebesian vessel connections that may have implications for retroperfusion or pressure-controlled intermittent CS occlusion in humans.

Blood Pressure↗
PubMed1994

The influence of elevated intraocular pressure on vascular pressures in the cat retina.

PURPOSE: Elevated intraocular pressure is known to reduce retinal blood flow, although the effect of intraocular pressure on retinal vascular pressures is unknown. Direct measurements of intravascular pressures were taken in the cat retina at various intraocular pressures. METHODS: Micropipettes of 2- to 3-microns tip diameter were used in conjunction with a servonull pressure-measuring system to determine retinal intravascular pressures in supine anesthetized cats. Pressures in large (80 to 120 microns diameter) vessels near the optic disc were measured over a wide range of intraocular pressures. RESULTS: Measurements show that retinal artery pressure depends on both intraocular pressure and mean systemic blood pressure, and that retinal vein pressure is determined by, but generally is different from, intraocular pressure, with no significant correlation to mean systemic blood pressure. Empirical equations are presented that predict statistically significant retinal artery, vein, and microvascular perfusion pressures. CONCLUSIONS: Intraocular pressure is an important determinant of the microvascular perfusion pressure in the retina of the cat, particularly at low mean systemic blood pressure. It is also apparent that retinal vein pressure is always greater than intraocular pressure, which implies the existence of a high-resistance extraretinal segment of the retinal vein. The results suggest mechanisms for the loss of visual function in glaucoma and other retinal circulatory disorders.

Animals↗