The classical Guyton view that mean systemic pressure, right atrial pressure, and venous resistance govern venous return is/is not correct.
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Atrial Function, Right↗
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Results for “Pressure”
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Randomised, controlled trial of alternating pressure mattresses compared with alternating pressure overlays for the prevention of pressure ulcers: PRESSURE (pressure relieving support surfaces) trial.
OBJECTIVE: To compare whether differences exist between alternating pressure overlays and alternating pressure mattresses in the development of new pressure ulcers, healing of existing pressure ulcers, and patient acceptability. DESIGN: Pragmatic, open, multicentre, randomised controlled trial. SETTING: 11 hospitals in six NHS trusts. PARTICIPANTS: 1972 people admitted to hospital as acute or elective patients. INTERVENTIONS: Participants were randomised to an alternating pressure mattress (n = 982) or an alternating pressure overlay (n = 990). MAIN OUTCOME MEASURES: The proportion of participants developing a new pressure ulcer of grade 2 or worse; time to development of new pressure ulcers; proportions of participants developing a new ulcer within 30 days; healing of existing pressure ulcers; and patient acceptability. RESULTS: Intention to treat analysis found no difference in the proportions of participants developing a new pressure ulcer of grade 2 or worse (10.7% overlay patients, 10.3% mattress patients; difference 0.4%, 95% confidence interval--2.3% to 3.1%, P = 0.75). More overlay patients requested change owing to dissatisfaction (23.3%) than mattress patients (18.9%, P = 0.02). CONCLUSION: No difference was found between alternating pressure mattresses and alternating pressure overlays in the proportion of people who develop a pressure ulcer. TRIAL REGISTRATION: ISRCTN 78646179.
Adult↗
By the way, doctor. I read in your July 2003 article on the new blood pressure guidelines with interest because I have high blood pressure. But one thing bothers me about articles on blood pressure: they always seem to talk about blood pressure as if it were the same number all day long. In my case, the systolic pressure can vary by 30 points and the diastolic by 15. So which should you use as your blood pressure reading: the average, the highest, or the lowest?
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Blood Pressure↗
[Pulse pressure and mean pressure relationship of intracranial pressure and lumbar cerebrospinal fluid pressure].
Intracranial pressure fluctuates due to heart beat, respiration, neuro-regulation, etc. Traditional intracranial pressure study focuses on the static pressure and related factors, putting emphasis on mean intracranial pressure, while paying little attention to the pulse components. This study was composed of two parts: animal experiment and theoretical analysis. The animal experiment was performed on 14 mongrel dogs, studying the variation of intracranial pressure wave form under different intracranial pressure level. The dogs were installed epidurally with latex sacculus to establish models of increased intracranial pressure. The degree of intracranial pressure and volume could be altered by changing the volume of fluid in the sacculus. During the process, pressure transducers were arranged to monitor and record the variations of the pressure of intracranial ventricle and lumbar subarachnoid cavity. The result demonstrated that, with the continual increase of intracranial pressure, intracranial pulse pressure increased correspondingly, showing a linear relationship with the change of intracranial pressure. After the sacculus was emptied and reinfused, the slope of the linear relationship was determined to be greater than the former slope. The same result was obtained in the lumbar cerebrospinal fluid pressure. Therefore, the lumbar cerebrospinal fluid pressure is consistent with the intracranial pressure. Intracranial pulse pressure is in linear relationship with mean pressure, and the slope of their linear relationship predicts the perform of intracranial autoregulation.
Animals↗
Interactions of high hydrostatic pressure, pressurization temperature and pH on death and injury of pressure-resistant and pressure-sensitive strains of foodborne pathogens.
The objective of this study is to determine the interactions between high hydrostatic pressure, pressurization temperature, time and pH during pressurization on death and injury of pressure-resistant and pressure-sensitive strains of four foodborne pathogens: Staphylococcus aureus 485 and 765, Listeria ,monocytogenes CA and OH2, Escherichia coli O157:H7 933 and 931, Salmonella enteritidis FDA and Salmonella typhimurium E21274. Among these strains S. aureus 485, L. monocytogenes CA, E. coli O157:H7 933 and S. enteritidis FDA were reported to be more pressure-resistant than the respective strain of the same species (Alpas et al., 1999). In general, viability loss of all pathogens was enhanced significantly as the level of pressure and temperature were increased (P < 0.05). All the strains except S. aureus 485 demonstrated more than 8 log cycle reduction when pressurized at 345 MPa at 50 degrees C for 5 min. This strain seemed to be the most pressure-resistant strain within the conditions of the study. Pressurization in the presence of either citric or lactic acid increased the viability loss by an additional 1.2-3.9 log cycles at pH 4.5 for both acids at 345 MPa. This study has indicated that high hydrostatic pressure applied in conjunction with mild heat and acidity can be an effective method for inactivating pressure-resistant and pressure-sensitive strains of four foodborne pathogens in organic acid solutions. This combination treatment indicates possible pressure pasteurization applications to liquid foods that have low pH. reserved.
Analysis of Variance↗
[The relationship between mouth pressure or tracheal pressure and esophagus pressure and diaphragmatic pressure].
OBJECTIVE: To investigate the relationship between mouth pressure (Pmo) or tracheal pressure (Ptr) and esophagus pressure (Pes) or transdiaphragmatic pressure. METHODS: Seventeen patients were involved in the study. Maximal inspiratory pressure (MIP), maximal transdiaphragmatic pressure (Pdi(max)), maximal esophagus pressure (Pes(max)), twitch mouth pressure (TwPmo), twitch transdiaphragmatic pressure (TwPdi) and twitch esophagus pressure (TwPes) were measured before narcotization as a normal procedure for the abdominal operation and twitch tracheal pressure (TwPtr(nar)), twitch esophagus pressure (TwPes(nar)) and twitch transdiaphragmatic pressure (TwPdi(nar)) were dynamically monitored during narcotization. RESULTS: (1) The correlation coefficient (r) values between Pdi(max) and MIP, TwPdi and TwPmo, TwPdi(nar) and TwPtr(nar), Pes(max) and MIP, TwPes and TwPmo, TwPes(nar) and TwPtr(nar) were 0.976 +/- 0.030, 0.816 +/- 0.155, 0.923 +/- 0.446, 0.981 +/- 0.185, 0.829 +/- 0.168 and 0.955 +/- 0.292, respectively. (2) The coefficient variation (CV) of MIP, Pes(max), Pdi(max), TwPmo, TwPes and TwPdi were (14.2 +/- 4.7)%, (15.2 +/- 4.3)%, (15.5 +/- 4.1)%, (30.4 +/- 15.9)%, (10.8 +/- 5.1)% and (9.9 +/- 4.0)%, respectively. The CV of TwPmo was the highest (compare with others, all P < 0.05) and that of TwPes and TwPdi was the lowest (compare with others, all P < 0.05). There was no significant difference among MIP, Pes(max) and Pdi(max) (P > 0.05). (3) The r value between the changing values of TwPtr(nar) and TwPdi(nar) or TwPes(nar) during narcotization were 0.839 or 0.894 (P = 0.000, respectively). CONCLUSION: The measurement of MIP and TwPmo should be repeated and the highest value should be chosen in order to reduce the possibility of underestimating the function of diaphragm, which could be dynamically monitored by TwPtr(nar).
Abdomen↗
Relationship between valve opening pressure, body position, and intracranial pressure in normal pressure hydrocephalus: paradigm for selection of programmable valve pressure setting.
OBJECTIVE: There is little scientific basis for guidance in selecting the optimal valve for the treatment of normal pressure hydrocephalus. The aim of this study was to determine the programmable valve opening pressure setting that would result in a slight reduction in intracranial pressure (ICP) after a ventriculoperitoneal shunt is implanted. We also assessed whether shunt-induced ICP could be predicted on the basis of a simple hydrodynamic equation. METHODS: In this prospective study of 11 patients with normal pressure hydrocephalus, ICP was measured before and after implantation of a shunt incorporating a programmable valve without an antisiphon device. Pressure measurements, including intraperitoneal pressure, were recorded at body angles ranging from 0 to 55 degrees and at valve settings ranging from 30 to 200 mm H(2)O. Measured ICP values were compared with values computed using a simple hydrodynamic equation. RESULTS: Even at a valve setting greater than the mean baseline ICP (200 mm H(2)O), the supine ICP was significantly lower than the baseline value (baseline ICP, 164 +/- 64 mm H(2)O; postoperative ICP, 125 +/- 69 mm H(2)O, P = 0.04). Valve pressure did not equate 1:1 with the measured postoperative ICP. Comprehensive ICP measurements at upright body positions demonstrated a stepwise reduction in ICP rather than a precipitous decline as a result of so-called siphoning. CONCLUSION: This study indicates that very high valve opening pressure settings may be optimal for the initial treatment of normal pressure hydrocephalus. The relationship between ICP and opening pressure valves is linear but not predicted by simple hydrodynamics.
Aged↗
Nasal intermittent positive pressure ventilation (NIPPV) versus nasal continuous positive airway pressure (NCPAP) for apnea of prematurity.
BACKGROUND: Apnea of prematurity is almost universal in infants who are born before 34 weeks gestation. Previous randomised trials and systematic reviews have found methylxanthines to be effective in preventing apnea of prematurity. However, recent concerns about potential long term side effects of methylxanthines on the neurodevelopment of low birth weight infants have led to an increased interest in alternate methods of treating apnea of prematurity. Nasal continuous positive airway pressure (NCPAP) is a useful method of respiratory support which reduces the incidence of obstructive or mixed apnea. However, apneic infants managed with NCPAP, with or without methylxanthines, sometimes require endotracheal intubation with its attendant morbidity and cost. Nasal intermittent positive pressure ventilation (NIPPV) is a simple, effective mode of respiratory support for older children and adults. It has been used to treat apnea in preterm infants but case reports of gastrointestinal perforations have limited its widespread use. OBJECTIVES: In preterm infants with recurrent apnea, does treatment with NIPPV lead to a greater reduction in apnea and need for intubation and mechanical ventilation, as compared with treatment with NCPAP? Does NIPPV increase the incidence of gastrointestinal complications, i.e. gastric distension leading to cessation of feeds, or perforation? SEARCH STRATEGY: Medline was searched (1966-2000) using the MeSH terms: infant, newborn (exp) and positive-pressure respiration (exp). Other sources included the Cochrane Controlled Trials Register and CINAHL (search terms: infant, newborn and intermittent positive pressure ventilation); also used were expert informants, previous reviews including cross-references, and conference and symposia proceedings. SELECTION CRITERIA: All randomised and quasi-randomised trials were included. Participants included unventilated preterm infants experiencing apnea of prematurity. Interventions compared were intermittent positive pressure ventilation administered via the nasal route, either by short nasal prongs or nasopharyngeal tube, and nasal CPAP delivered by the same methods. Types of outcome measures: - failure of therapy as defined by apnea that is frequent or severe requiring additional ventilatory support - rates of endotracheal intubation - rates of apnea and bradycardia expressed as events per hour - gastrointestinal complications i.e. abdominal distension requiring cessation of feeds, or GI perforation DATA COLLECTION AND ANALYSIS: Data were extracted independently by the three reviewers. The trials were analysed using relative risk (RR), risk difference (RD) and number needed to treat (NNT) for dichotomous data; means and weighted mean difference (WMD) were used for continuous data. MAIN RESULTS: Two trials, enrolling 54 infants in total, fulfilled the inclusion criteria. Both reported only the short term results (4 to 6 hours) of the interventions. Only one infant (randomised to NCPAP) required intubation during this period. Ryan (1989), in a cross over study of 20 infants, showed no significant difference in rates of apnea (events/hr) between the 2 interventions (WMD -0.10 (-0.53,0. 33)). Lin (1998) randomised 34 infants and demonstrated a greater reduction in frequency of apneas (events/hr) with NIPPV compared to NCPAP (WMD -1.19 (-2.31,-0.07)). Meta-analysis of both trials showed no difference in pCO2 (mmHg) at the end of the 4-6 hour study period (WMD 0.95 (-3.05,4.94)). No data were reported on gastrointestinal complications. REVIEWER'S CONCLUSIONS IMPLICATIONS FOR PRACTICE: NIPPV may be a useful method of augmenting the beneficial effects of NCPAP in preterm infants with apnea that is frequent or severe. Its use appears to reduce the frequency of apneas more effectively than NCPAP. Additional safety and efficacy data are required before recommending NIPPV as standard therapy for apnea. IMPLICATIONS FOR RESEARCH: Future trials with sufficient power should assess the efficacy (reduction in failure of therapy) and safety (GI complications) of NIPPV. Outcomes should be assessed throughout the entire period during which the infant requires assisted ventilation. The recent ability to synchronise NIPPV with an infant's spontaneous respirations is a promising development requiring further assessment.
Apnea↗
Extubation from low-rate intermittent positive airways pressure versus extubation after a trial of endotracheal continuous positive airways pressure in intubated preterm infants.
BACKGROUND: Failure of extubation and subsequent reintubation may result in additional stress and trauma to the premature infant. Testing infants about to be extubated with a period of endotracheal CPAP has been suggested as a method of demonstrating readiness for extubation. However, this process has been criticized as increasing the neonate's work of breathing and perhaps increasing the likelihood of extubation failure. OBJECTIVES: In premature infants having their endotracheal tube removed, is direct extubation from low rate intermittent positive pressure ventilation (IPPV) more successful than that following a period of endotracheal continuous positive airway pressure (CPAP)? SEARCH STRATEGY: The standard search strategy of the Neonatal Review Group as outlined in the Cochrane Library was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register, MEDLINE, previous reviews including cross references, abstracts, conferences, symposia proceedings, expert informants and journal hand searching mainly in the English language. SELECTION CRITERIA: All trials using random or quasi-random allocation of premature infants to endotracheal CPAP or direct extubation following a period of IPPV were included. DATA COLLECTION AND ANALYSIS: Data were extracted using standard methods of the Cochrane Collaboration and its Neonatal Review Group, with separate evaluation of trial quality and data extraction by each author and synthesis of data using relative risk. MAIN RESULTS: Direct extubation from low rate ventilation is associated with a trend to increased chance of successful extubation when compared to extubation after a period of endotracheal CPAP, RR 0.45 (0.19,1.07), RD -0.103 (-0.200,-0.006), NNT 10 (5,167). When only truly randomized trials are considered, this result becomes both statistically significant and clinically important, RR 0.10 (0.01,0.78), RD -0.201 (-0.319,-0.083), NNT 5 (3, 12). Similar differences are seen for the secondary outcome, apnea. REVIEWER'S CONCLUSIONS: Preterm infants no longer requiring endotracheal intubation and IPPV should be directly extubated without a trial of ETT CPAP.
Humans↗
Central venous pressure and pulmonary capillary wedge pressure as estimates of left atrial pressure: effects of positive end-expiratory pressure and catheter tip malposition.
We compared CVP and pulmonary capillary wedge pressure (WP) measurements with left atrial pressure (LAP) in postcoronary bypass surgical patients with preserved cardiopulmonary function. Measurements were obtained under normal conditions and conditions likely to induce WP-LAP discrepancies (PEEP and catheter tip malposition). Patients were in both supine and lateral positions; the catheter tip was placed vertically below (tip down; n = 12) or above (tip up; n = 5) the left atrium. Our data showed that both CVP and WP correlated well with LAP at all PEEP levels in the supine and tip down lateral positions. However, in the tip up lateral position, WP overestimated LAP (13.3 +/- 3.4 vs. 8.0 +/- 2 mm Hg; p less than .01) at 20 cm H2O of PEEP, whereas CVP (8.8 +/- 2.1 mm Hg) closely reflected LAP. Thus, by placing the catheter tip vertically below the left atrium in supinely and laterally positioned patients, CVP and WP both produced reliable estimates of LAP despite an acute increase in alveolar pressure. When the pulmonary artery catheter tip was vertically above the left atrium, WP overestimated LAP. Under these conditions, CVP remained a reliable estimate of LAP. We conclude that CVP measurement as an estimate of LAP in this patient population could be used and not ignored. This is true in patients with previously documented good LAP-CVP correlation who are subjected subsequently to conditions which may produce an LAP-WP discrepancy (high PEEP and catheter tip malposition).
Aged↗
Heart rate variability and hemodynamic alterations in canines with normal cardiac function during exposure to pressure support, continuous positive airway pressure, and a combination of pressure support and continuous positive airway pressure.
Variations in intrathoracic pressure generated by different ventilator weaning modes may significantly affect intrathoracic hemodynamics and cardiovascular stability. Although several investigators have attributed cardiovascular alterations during ventilator weaning to augmented sympathetic tone, there is limited investigation of changes in autonomic tone during ventilator weaning. Heart rate variability (HRV), the analysis of beat-to-beat changes in heart rate, is a noninvasive indicator of autonomic tone that might be useful in the identification of patients who are at risk for weaning difficulty due to underlying cardiac dysfunction. The authors describe HRV and hemodynamics in response to 3 ventilatory conditions: pressure support (PS) 10 cmH2O, continuous positive airway pressure (CPAP) 10 cmH2O, and a combination of PS 10 cmH2O and CPAP 10 cmH2O (PS + CPAP) in a group of canines with normal ventricular function. Six canines were studied in the laboratory. Continuous 3-lead electrocardiographic data were collected during baseline (controlled mechanical ventilation) and following transition to each of the ventilatory conditions (PS, CPAP, PS + CPAP) for analysis of HRV. HRV was evaluated using power spectral analysis to define the power under the curve in a very low frequency range (0.0033 to < 0.04 Hz, sympathetic tone), a low frequency range (0.04 to < 0.15 Hz, primarily sympathetic tone), and a high frequency range (0.15 to < 0.40 Hz, parasympathetic tone). A thermodilution pulmonary artery catheter measured cardiac output and right ventricular end-diastolic volume to describe global hemodynamics. There were significant increases in very low frequency power (sympathetic tone) with a concomitant significant reduction in high-frequency power (parasympathetic tone) with exposure to PS + CPAP. These alterations in HRV were associated with significantly increased heart rate and reduced right ventricular end-diastolic volume. Although there was a small but significant increase in cardiac output with exposure to PS, HRV was unchanged. These data indicate that there was a relative shift in autonomic balance to increased sympathetic and decreased parasympathetic tone with exposure to PS + CPAP. The increase in intrathoracic pressure reduced right ventricular end-diastolic volume (preload). This hemodynamic alteration generated a change in autonomic tone, so that cardiac output could be maintained. Individuals with autonomic and/or cardiovascular dysfunction may not be capable of this type of response and may fail to successfully wean from mechanical ventilation.
Analysis of Variance↗
When is a pressure ulcer not a pressure ulcer? ... external pressure versus internal pressure.
This case study presents a nontraditional explanation for recurring and difficult to heal pressure ulcers: internal pressure rather than external pressure. The authors are hopeful that this discussion will assist colleagues in recognizing this alternative diagnosis.
Female↗
The use of peridialysis blood pressure and intradialytic blood pressure changes in the prediction of interdialytic blood pressure in haemodialysis patients.
OBJECTIVE: It is uncertain which blood pressure values (pre- or post-haemodialysis) best represent the average daily blood pressure in haemodialysis patients. The purpose of this study was to verify the power of peridialysis blood pressure to predict interdialytic blood pressure, and to ascertain the influence of blood pressure fluctuations during dialysis on this predictive ability. METHODS AND RESULTS: We performed ambulatory blood pressure monitoring during the interdialytic period on 60 stable haemodialysis patients (mean age 53 +/- 16 years, 33 male) between two mid-week haemodialysis sessions. Pre- and post-haemodialysis blood pressures were 154/82 and 142/77 mmHg, respectively, and 44-h interdialytic blood pressure was 136/77 mmHg. Overall, post-haemodialysis blood pressure values correlated with interdialytic ambulatory blood pressure marginally better than did pre-haemodialysis values (r = 0.52 versus 0.61 for pre- and post-dialysis systolic pressure, respectively; r = 0.67 versus 0.72 for pre- and post-dialysis diastolic pressure, respectively). The average of the pre- and post-haemodialysis values showed a slightly better correlation with interdialytic blood pressure (r = 0.65 and 0.75 for systolic and diastolic pressure, respectively). When we stratified patients according to systolic blood pressure behaviour during dialysis, pre-dialysis blood pressure was the stronger predictor of interdialytic blood pressure in the quartile with greatest intradialytic blood pressure fall (r = 0.67 versus 0.44 for pre- and post-dialysis systolic blood pressure, respectively), whereas post-dialysis values were substantially better in the group with a rise in systolic pressure during dialysis (r = 0.26 versus 0.59 for pre- and post-dialysis systolic blood pressure, respectively). CONCLUSIONS: These data demonstrate that peridialysis blood pressure values are of limited accuracy in predicting interdialytic blood pressure, post-dialysis values are minimally better predictors than pre-dialysis blood pressures, and the average of pre- and post-haemodialysis values is marginally better than both. In addition, blood pressure fluctuations during dialysis have a sizable impact on this predictive ability. Clinical decisions related to blood pressure management and research design in haemodialysis hypertension should take these factors into account.
Blood Pressure↗
Systolic blood pressure at end-expiration measured by the automated systolic pressure variation monitor is equivalent to systolic blood pressure during apnea.
OBJECTIVE: It is necessary to define a reference systolic arterial blood pressure (RP) to calculate delta-Up (dUp) and delta-Down (dDown) for systolic pressure variation. Most studies define the reference pressure as the average systolic blood pressure during a short period of apnea. We describe an automated systolic pressure variation monitor that measures airway pressure and defines the reference pressure as the systolic blood pressure at end-expiration. The present study compares the reference systolic blood pressure measured at end-expiration by the automated systolic pressure variation monitor and the reference systolic blood pressure measured during apnea to test whether the end-expiration value is an adequate substitute for the value during apnea. METHODS: After obtaining informed consent, 108 sets of measurements of systolic pressure variation (SPV) were made in 20 intubated, mechanically-ventilated, anesthetized patients by the automated SPV monitor and during apnea. Measurements were taken during periods of hemodynamic stability defined as three consecutive end-expiratory systolic blood pressures within four mmHg of each other. The three systolic pressures at end-expiration were averaged (RPmonitor). Immediately following these measurements, the ventilator was turned off and the systolic blood pressure was measured at 6, 8, 10 and 12 seconds of apnea. The reference pressure during apnea (RPapnea) was defined as the average of the systolic blood pressure at 8, 10 and 12 seconds of apnea. For each measurement set, RPmonitor and the systolic blood pressure at 6 seconds of apnea (SBP6) were compared to RPapnea using Bland-Altman analysis. RESULTS: Bland-Altman analysis for the difference between SBP6 and RPapnea yielded a small bias of -0.3 mmHg with standard deviation of 1.3, indicating that the systolic pressure tends to continue to increase slightly after 6 seconds of apnea. Results were similar for the difference between RPmonitor and RPapnea (-0.2 +/- 3.1 mmHg). CONCLUSIONS: dUp and dDown are calculated using the reference pressure. RPmonitor is an average of 0.2 mm Hg less than RPapnea, thus dUp calculated by the automated SPV monitor is an avenge of 0.2 mm Hg greater than dUp measured by the reference pressure during apnea and dDown is 0.2 mm Hg less. Since the bias of -0.2 mmHg is clinically insignificant, there is acceptable agreement between the reference pressure obtained during apnea and that obtained by the automated SPV monitor at end-expiration. The mean difference between RPmonitor and RPapnea is explained by the continued rise in systolic pressure during the period of apnea as demonstrated by the difference between SBP6 and RPapnea.
Anesthesia↗
Effects of varying levels of positive end-expiratory pressure on intracranial pressure and cerebral perfusion pressure.
OBJECTIVE: To determine the influence of positive end-expiratory pressure (PEEP) on intracranial pressure and cerebral perfusion pressure. DESIGN: Neurosurgical intensive care patients requiring intracranial pressure monitoring and mechanical ventilation were studied in a randomized, controlled study. SETTING: Tertiary care, neurosurgical intensive care unit. PATIENTS: Eighteen patients were enrolled in the study. Patients had posttraumatic head injuries (n = 9), subarachnoid hemorrhage (n = 7), obstructive hydrocephalus (n = 1), and intracerebral hemorrhage of unknown cause (n = 1). INTERVENTIONS: Patients had PEEP levels of 5, 10, and 15 cm H2O applied to their lungs. MEASUREMENTS AND MAIN RESULTS: Changes in intracranial pressure, mean arterial pressure, and cerebral perfusion pressure were measured. The results were analyzed separately for patients with normal and increased intracranial pressure (> 15 mm Hg). PEEP at 5 cm H2O had no effect on intracranial pressure in the group with normal intracranial pressure. However, PEEP at 10 and 15 cm H2O produced a significant (p < .05) increase in intracranial pressure (1.9 and 1.5 mm Hg, respectively). In the group with increased intracranial pressure, no significant change in intracranial pressure occurred at any of the PEEP levels used. In both groups, cerebral perfusion pressure was unchanged throughout. CONCLUSIONS: In patients with normal intracranial pressure, PEEP at 5 cm H2O did not significantly alter intracranial pressure. The clinical relevance of the intracranial pressure increase at PEEP levels of 10 and 15 cm H2O is questionable because cerebral perfusion pressure did not change and remained > 60 mm Hg. In patients with increased intracranial pressure, higher levels of PEEP did not significantly change intracranial pressure or cerebral perfusion pressure.
Adult↗
Peak volume history and peak pressure-volume curve pressures independently affect the shape of the pressure-volume curve of the respiratory system.
OBJECTIVE: To determine the specific effect of peak volume history pressure on the inflation limb of the pressure-volume curve and peak pressure-volume curve pressure on the deflation limb of the pressure-volume curve. DESIGN: Prospective assessment of pressure-volume curves in saline, lung lavage injured sheep. SETTING: Large animal laboratory of a university-affiliated hospital. SUBJECTS: Eight female Dorset sheep. INTERVENTIONS: : The effect of two volume history pressures (40 and 60 cm H2O) and three pressure-volume curve peak pressures (40, 50, and 60 cm H2O) were randomly compared. MEASUREMENTS AND MAIN RESULTS: Peak volume history pressure affected the inflation curve beyond the lower inflection point but did not affect the inflection point (Pflex). Peak pressure-volume curve pressure affected the deflation curve. Increased peak volume history pressure increased inflation compliance (p <.05). Increased peak pressure-volume curve pressure increased the point of maximum compliance change on the deflation limb and deflation compliance and decreased compliance between peak pressure and the point of maximum curvature on the deflation limb (p <.05). CONCLUSION: Peak volume history pressure must be considered when interpreting the inflation limb of the pressure-volume curve of the respiratory system beyond the inflection point. The peak pressure achieved during the pressure-volume curve is important during interpretation of deflation compliance and the point of maximum compliance change on the deflation limb.
Animals↗
[The determination of arterial pressure by the physician or the nurse: its relation to ambulatory pressure and left ventricular mass. The MAPA-Madrid Group. Monitorización Ambulatoria de la Presión Arterial (Ambulatory Monitoring of Arterial Pressure)].
BACKGROUND: In the present study we evaluated the influence of the observer's status--physician or nurse--on blood pressure levels and the relationship among clinic blood pressure measurement with ambulatory blood pressure and left ventricle mass. PATIENTS AND METHODS: Cross sectional study performed in seven primary care centers. Participating physicians and nurses were trained for blood pressure measurement prior to the study and subsequently retrained at 3 month intervals during the study. Patients included in the study were 122 subjects with mild to moderate hypertension who underwent the following study protocol: a) measurement of clinic blood pressure by physician and nurse, in an independent fashion, on 3 visits; b) clinic-epidemiologic questionnaire; c) conventional hematological and biochemical study; d) electrocardiogram; e) 24-hour ambulatory blood pressure monitoring, f) M-mode and Doppler echocardiography (only in 58 subjects). RESULTS: Nurse-measured blood pressure levels were higher than those determined by physicians (mean differences: 3.9 [6.7] mmHg in systolic blood pressure and 2.6 [5.4] mmHg in diastolic blood pressure). The blood pressure level differences between the two observers were higher in female patients and subjects with low educational level, independently of the observer's gender. Nurse-measured blood pressure was more closely related to ambulatory blood pressure and left ventricle mass than physician-measured blood pressure. CONCLUSIONS: Nurse-measured blood pressure levels are lower than those determined by physicians and more closely related to ambulatory blood pressure and left ventricle mass than physician-measured blood pressure. These data support that nurses, instead of doctors, should routinely measure blood pressure in primary care centers.
Adolescent↗
Continuous distending airway pressure for respiratory distress syndrome in preterm infants.
BACKGROUND: Respiratory distress syndrome (RDS) is the single most important cause of morbidity and mortality in preterm infants (Greenough 1998, Bancalari 1992). Intermittent positive pressure ventilation (IPPV) with surfactant is the standard treatment for the condition. The major difficulty with IPPV is that it is invasive, resulting in airway and lung injury and contributing to the development of chronic lung disease. OBJECTIVES: In spontaneously breathing preterm infants with RDS, to determine if continuous distending airway pressure (CDAP) reduces the need for IPPV and associated morbidity without adverse effects. SEARCH STRATEGY: The standard search strategy of the Neonatal Review group was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register, MEDLINE, previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, journal hand searching mainly in the English language. SELECTION CRITERIA: All trials using random or quasi-random patient allocation of newborn infants with RDS were eligible. Interventions were continuous distending airway pressure including continuous positive airway pressure (CPAP) by mask, nasal prong, nasopharnygeal tube, or endotracheal tube, or continuous negative pressure (CNDP) via a chamber enclosing the thorax and lower body, compared with standard care. DATA COLLECTION AND ANALYSIS: Standard methods of the Cochrane Collaboration and its Neonatal Review Group, including independent assessment of trial quality and extraction of data by each author, were used. MAIN RESULTS: CDAP is associated with a lower rate of failed treatment (death or use of assisted ventilation), overall mortality, and mortality in infants with birthweights above 1500 g. The use of CDAP is associated with an increased rate of pneumothorax. REVIEWER'S CONCLUSIONS: In preterm infants with RDS the application of CDAP either as CPAP or CNDP is associated with some benefits, particularly in infants with birthweights over 1500 gms. The extent of this benefit is difficult to assess given the outdated methods to administer CDAP, low use of antenatal corticosteroids, non-availability of surfactant and the intensive care setting of the 1970's in which these trials were done. Where resources are limited, such as in developing countries, CPAP for RDS may have a clinical role. Further research is required to determine the best mode of administration and its role in modern intensive care settings
Humans↗