Preventing heel pressure sores: a comparison of heel pressure relieving devices

• ? It has been widely recognized that elderly patients with an orthopaedic problem are predisposed to developing heel pressure sores.
• ? In this study four pressure-reducing devices, commonly used in the prevention of heel ulcers, were objectively compared for their ability to decrease or remove pressure on the heels of patients with fractured necks of femurs and fractured femurs.
• ? Forty-one patients were randomly allocated a pressure relieving device. The efficacy of the device was evaluated by continuously assessing the skin integrity of both heels on a daily basis over a period of 12 days. Data were collected over a 30 month period.
• ? The four devices were foam splints, eggshell foam, duoderm and heel protector boots. Foam splints and eggshell foam proved to be more effective devices in relieving pressure exerted on the heel.
• ? This study recognizes that meticulous nursing care remains the critical clement in prevention of heel ulcers; however, the use of eggshell foam and foam splints in conjuction with this enhances the maintenance of skin integrity.

     

外源性呼气末正压对气道压力的影响

目的探讨外源性呼气末正压（PEEP）对气过压力影响的规律。方法通过模拟肺（静态顺应性为28ml／cmH2O,气道阻力为0．8cmH2O·L－1·S-1）试验,设置不同的PEEP,观察气道压力（修压、平均压、平台压）的变化。结果外源性PEEP从0增加至3cmH2O时,气过压力增幅最大,平均每增加1cmH2OPEEP,气道峰压、平台压增加3．5～4．1cmH2O,当PEEP增加至12cmH2O时,气道峰压和平台压增加了20cmH2O以上。结论外源性PEEP对气造压力的影响,可产生一种“扩大”效应,这种“扩大”效应在低水平的PEEP时尤为显著。在使用人工机械通气时,如需设置外源性PEEP时,必须严密监测气道压力的变化,以防止肺损伤。     

Comparative accuracies of a finger blood pressure monitor and an oscillometric blood pressure monitor

A noninvasive blood pressure monitor (Finapres) that uses the methodology of Peaz to continuously display the arterial waveform from the finger has been introduced recently. The Finapres monitor overestimated systolic pressure by 5.8±11.9 mm Hg, while the Dinamap monitor underestimated systolic pressure by –6.9±9.2 mm Hg (P=0.003). Dinamap mean and diastolic pressure biases were less than 2 mm Hg, while the Finapres biases for these variables were significantly greater (7.7±10.0 and 8.2±9.8 mm Hg, respectively). There was no difference in systolic or mean pressure precision between the two devices (approximately 10 mm Hg), but the diastolic precision of the Dinamap unit was superior to that of the Finapres. While in most patients the Finapres monitor provided continuous blood pressure data equivalent to the data from the radial artery, marked bias (>15 mm Hg) was exhibited in 2 patients for all three pressure variables. Despite this bias, blood pressure changes were tracked closely in these 2 patients. We conclude that, in its current form, the Finapres monitor cannot be relied upon independently to accurately measure blood pressure in patients undergoing general anesthesia. Since the Dinamap monitor measures mean pressure reliably and accurately, we suggest that mean blood pressure values between the Finapres and Dinamap monitors be compared to guide one in interpreting Finapres data.Supported in part by a grant from Ohmeda Company, Boulder, CO.Presented in part at the annual meeting of the American Society of Anesthesiologists, New Orleans, October 1989.     

Influence of tissue pressure on central venous pressure/peripheral venous pressure correlation: An experimental report

BACKGROUND: Peripheral venous pressure (PVP) has been shown to correlate with central venous pressure (CVP) in a number of reports. Few studies, however, have explored the relationship between tissue pressure (TP) and PVP/CVP correlation.METHODS: PVP and CVP were simultaneously recorded in a bench-top model of the venous circulation of the upper limb and in a single human volunteer after undergoing graded manipulation of tissue pressure surrounding the intervening venous conduit. Measures of correlation were determined below and above a point wherein absolute CVP exceeded TP.RESULTS: Greater correlation was observed between PVP and CVP when CVP exceeded TP in both models. Linear regression slope was 0.975 (95% CI: 0.959-0.990); r² 0.998 above tissue pressure 10 cmH₂O vs. 0.393 (95% CI: 0.360-0.426); and r² 0.972 below 10 cmH₂O at a flow rate of 2000 mL/h in the in vitro model. Linear regression slope was 0.839 (95% CI: 0.754-0.925); r² 0.933 above tissue pressure 10 mmHg vs. slope 0.238 (95% CI: -0.052-0.528); and r²0.276 in the en vivo model.CONCLUSION: PVP more accurately reflects CVP when absolute CVP values exceed tissue pressure.     

Positive end-expiratory pressure (PEEP) and cerebrospinal fluid pressure during normal and elevated intracranial pressure in dogs

The effect of up to 15 cm H₂O positive end-expiratory pressure (PEEP) on cerebrospinal fluid pressure (Pcsf) was investigated in five anaesthetised, mechanically ventilated dogs during normal and then elevated (40–50 cm H₂O) intracranial pressure (ICP). Stepwise elevations of PEEP in 5 cm H₂O increments resulted in small rises in Pcsf at normal ICP and in significantly larger rises when ICP was elevated. The regression equations for the relationships between Pcsf and end-expiratory pressure (EEP) were as follows: Pcsf=12.95+0.82 EEP for normal ICP, and Pcsf=46.41+2.06 EEP for elevated ICP. Mean PaCO₂ rose from 39.7±2.5 to 47.6±5.0 torr during normal ICP, and from 34.2±2.9 to 50.9±5.3 torr at elevated ICP as PEEP was elevated to 15 cm H₂O. We conclude that PEEP raised Pcsf, and that this increase is more severe under conditions of elevated ICP. The rise in Pcsf due to PEEP may be explained by either the rise in intrathoracic pressure or the rise in PaCO₂, or both.Dedicated to Professor Dr. Johannes Linzbach, Göttingen, on the occasion of his 70th birthday     

The risk of pressure sores: a conceptual scheme

? Based on a review of the literature related to the prediction and prevention of pressure sores, a conceptual scheme on pressure sores is introduced. ? The article highlights the four elements of the scheme: pressure, shearing force, tissue tolerance for pressure and tissue tolerance for oxygen. Factors influencing pressure and shearing forces, the pressure distribution capacity of tissue, the oxygen need of tissue and oxygen supply to tissue are discussed.     

Pulse pressure variation is not a valid predictor of fluid responsiveness in patients with elevated left ventricular filling pressure

Purpose

The purpose of this study was to test the hypothesis that the predictive ability of pulse pressure variation (PPV) for fluid responsiveness would be altered in patients with elevated left ventricular (LV) filling pressure.

Materials and methods

According to the preoperative echocardiographic assessment of the ratio of early transmitral flow velocity to early diastolic velocity of the mitral annulus (E/E′), patients undergoing surgical coronary revascularization were classified into normal (n = 34, E/E′ < 8) and high (n = 34, E/E′ > 15) LV filling pressure group. After anesthetic induction, PPV and hemodynamic data were measured before and after 6 mL/kg of colloid administration. Fluid responsiveness was defined as 12% or more increase in stroke volume index assessed by pulmonary artery catheter and tested by the area under the receiver operating characteristic curve (AUROC).

Results

The AUROCs of PPV in the normal and high filling pressure group were 0.829 (95% confidence interval [CI], 0.661-0.963; P < .001) and 0.583 (95% CI, 0.402-0.749; P = .110), respectively. The AUROCs of cardiac filling pressures and right ventricular end-diastolic volume index did not show statistical significance in both groups.

Conclusions

None of the assessed preload indices including PPV were able to predict fluid responsiveness in patients with elevated LV filling pressure.     

机械通气患者呼气末正压对膀胱压的影响

目的：探讨机械通气患者呼气末正压（PEEP）对膀胱压的影响。方法选取我院重症医学科机械通气且监测膀胱压的患者40例,将膀胱压正常＜1．47 kPa（15 cmH2 O）的患者23例作为A组,膀胱压增高≥1．47 kPa （15 cm H2 O ）的患者17例作为 B 组,采用自身对照法,观察患者在断开呼吸机及使用呼气末正压0 kPa （0 cmH2O）、0．294 kPa （3 cmH2O）、0．490 kPa（5 cmH2O）、0．981 kPa（10 cmH2O）和1．47 kPa（15 cmH2O）时的膀胱压变化。结果A组患者在不同呼气末正压时膀胱压的变化差异无统计学意义（P＞0．05）。B组患者在呼气末正压＞0．294 kPa（3 cmH2 O）时随着呼气末正压的增高膀胱压也会随之增高,差异有统计学意义（P＜0．05）,呼气末正压为≤0．294 kPa（3 cmH2 O）时与断开呼吸机时测得的膀胱压比较,差异无统计学意义（P＞0．05）。结论膀胱压＜1．47 kPa（15 cm H2 O ）时,可保持呼吸机的呼气末正压正常调整,以保证患者的氧合,保障患者的安全。膀胱压≥1．47 kPa（15 cmH2 O）时,应保持呼吸机的呼气末正压≤0．294 kPa（3 cmH2 O）的水平,以保证患者的氧合,保障患者的安全。     

呼气末正压对机械通气患者中心静脉压及髂总静脉压的影响

目的 观察不同呼气末正压(PEEP)水平对机械通气患者中心静脉压(CVP)和髂总静脉压(CIVP)及两者相关关系的影响.方法 将2007年2-8月收住重症加强治疗病房(ICU),无心肺疾患、循环稳定、无腹胀、无凝血功能异常,需机械通气的20例成年患者列为观察对象,采用自身对照,随机加用0、5和10 cm HzO(1 am H2O=0.098 kPa)PEEP,评估在此条件下,CVP、CIVP和两者压力阶差变化及其与机械通气压力变化间的相关关系.结果 CVP及CIVP随PEEP增加而增高,差异有统计学意义(P0.05);CVP及CIVP与机械通气各压力值变化呈正相关,但CVP及CIVP仅与平均气道压(Pmean)及PEEP有统计学意义(CVP与PEEP r=0.751,CIVP与PEEP r=0.685,CVP与Pmean r=0.634,CIVP与Pmena r=0.603,P均相似文献   

Intervention studies to reduce the prevalence and incidence of pressure sores: a literature review

Much has been written about the prevention of pressure sores. However, electronic and manual searches located only 10 studies within the literature in the UK that described interventions able to reduce either their incidence or prevalence. All the studies located contained serious methodological flaws. Apparent success in reducing the number or severity of pressure sores could have resulted because staff involved in data collection were aware that the study was being undertaken and thus took more interest in pressure area care. From the review findings it is apparent that there is a dearth of research evidence upon which to base practice in the sphere of pressure sore prevention and further research is urgently required.     

Cerebral perfusion pressure and intracranial pressure in relation to neuropsychological outcome

Objective: The study attempted to examine the relationship between neuropsychological functioning and reduced cerebral perfusion pressure (CPP), raised intracranial pressure (ICP), and reduced mean arterial pressure (MAP), monitored during intensive care treatment. Design: This prospective follow-up study included consecutive pa- tients and evaluated outcome at 6 months postinjury by the administration of a neuropsychological test battery. Setting: The study was conducted at the University Hospital of Gent, Belgium. Patients and participants: Over a 30-month period, 43 patients were included. Inclusion criteria were the following: hospital admission following closed head injury, ICP monitoring, no medical history of central nervous system disease or mental retardation, survival for at least 6 months, and informed consent for participation. Interventions: All patients received the hospital's standard treatment for head injury, which remained unchanged during the study period. Measurements and results: Reduced CPP was analyzed using the number of observed values below 70 mmHg, raised ICP using the number of values above 20 mmHg, and MAP using the number of values below 80 mmHg. The neuropsychological test battery included 11 measures of attention, information processing, motor reaction time, memory, learning, visuoconstruction, verbal fluency, and mental flexibility. No linear relationships were found between overall neuropsychological impairment and episodes of reduced CPP, raised ICP, or reduced MAP. Conclusions: Although reduced CPP and raised ICP are frequent, often fatal, complications of head injury, in survivors they do not seem to be related to later neuropsychological functioning. Received: 6 June 1997 Accepted: 4 December 1997     

Clinical experience with a fiberoptic intracranial pressure monitor

Retrospective clinical experience with our first 46 patients monitored with a fiberoptic intracranial pressure device is described. In 43 of 46 patients, the transducer was introduced into brain parenchyma. A ventriculostomy system was used in 3 of 46 patients. The monitoring system was generally characterized by ease of placement and system maintenance and by technical simplicity. Several problems were encountered, including breakage of system components (12%), erroneous readings requiring transducer repositioning (8.6%), epidural hematoma (3.4%), and infection (1.7%). No infections or hematomas occurred in the 3 cases in which the ventriculostomy system was used. Overall, our experience with the Camino intracranial pressure fiberoptic monitoring system confirms previous reports of its favorable features.     

Development and evaluation of a self-regulating alternating pressure air cushion

Purpose: To investigate the effect of alternating air cells of a newly developed dynamic cushion on interface pressure and tissue oxygenation levels. Method: This cross-over experimental study included 19 healthy volunteers. The dynamic cushion used has an automatic self-regulating alternating pressure air-cell system with 35 small and four large air cells for maintaining posture while seated. This cushion also has 17 bottoming-out detectors that automatically inflate the air cells to release a high interface pressure. To assess the effect of this alternating system, participants sat on the new cushion with an alternating system or static system for 30?min and then performed push-ups. The interface pressure was monitored by pressure-sensitive and conductive ink film sensors and tissue oxygenation levels were monitored by near-infrared spectroscopy. A reactive hyperaemia indicator was calculated using tissue oxygenation levels as an outcome measure. Results: The peak interface pressure was not significantly different between the groups. The reactive hyperaemia indicator was significantly higher in the static group than in the alternating group. Conclusions: An alternating system has beneficial effects on blood oxygenation levels without increasing interface pressure. Therefore, our new cushion is promising for preventing pressure ulcers with patients with limited ability to perform push-ups.

• Implications for Rehabilitation

• A dynamic cushion was developed, which consists of a uniquely-designed air-cell layout, detectors for bottoming out, and an alternating system with multiple air-cell lines.

• The alternating system did not increase interface pressure and it significantly reduced reactive hyperaemia after 30?min of sitting in healthy volunteers.

• This cushion is a new option for individuals who require stable posture but have limitations in performing scheduled push-ups for prevention of pressure ulcers.

     

Myocardial transmural pressure in ventilated patients

The validity of oesophageal pressure measurement as an indicator of intrathoracic pressure changes during IPPV and CPPV was evaluated in 14 patients after open heart surgery. Simultaneously recorded pressures from the airway, pericardium, oesophagus and left atrium all demonstrated an increase following IPPV and CPPV directly proportional to the increasing PEEP level. A significant positive correlation was found between the pressure increase in the pericardium and oesophagus. Therefore the measurement of oesophageal pressure closely reflected the changes in intrathoracic pressure, in recumbent, ventilated patients and enables the cardiac transmural pressure to be calculated. However, during CPPV the increase in oesophageal pressure did not fully reach the corresponding pressure changes in the pericardium and resulted in an over-estimation of the cardiac transmural pressures. Transmural left atrial pressure appeared to decrease as the lung was inflated during mechanical ventilation with increasing PEEP. This decrease is probably due to the direct effect of regional lung pressure on the pericardium and heart, an effect that cannot be recognized by measurement of oesophageal pressure. Such constraints limit the evaluation of myocardial performance according to the Starling relationship during mechanical ventilation with high airway pressures.With the support of the Swiss National Fund for the advancement of Scientific Research, Berne. Application no. 3.831-0.79     

Alternating pressure air mattresses as prevention for pressure ulcers: a literature review

OBJECTIVES: The purpose of this paper is to examine and synthesise the literature on alternating pressure air mattresses (APAMs) as a preventive measure for pressure ulcers. DESIGN: Literature review. DATA SOURCES: PubMed, Cinahl, Central, Embase, and Medline databases were searched to identify original and relevant articles. Additional publications were retrieved from the references cited in the publications identified during the electronic database search. RESULTS: Thirty-five studies were included. Effectiveness and comfort of APAMs were the main focuses of the studies evaluating APAMs. Pressure ulcer incidence, contact interface pressure, and blood perfusion were the most frequently used outcome measures to evaluate the effectiveness of APAMs. Fifteen randomised controlled trials (RCTs) analysed the pressure ulcer incidence. One RCT compared a standard hospital mattress with an APAM and found that the APAM was a more effective preventive measure. RCTs comparing APAMs with constant-low-air mattresses resulted in conflicting evidence. There was also no clear evidence as to which type of APAM performed better. All RCTs had methodological flaws. The use of contact interface pressure and blood perfusion measurements to evaluate the effectiveness of APAMs is questionable. Comfort of APAMs was the primary outcome measure in only four studies. Different methods for assessment were used and different types of APAMs were evaluated. Better measures for comfort are needed. A few studies discussed technical problems associated with APAMs. Educating nurses in the correct use of APAMs is advisable. CONCLUSION: Taking into account the methodological issues, we can conclude that APAMs are likely to be more effective than standard hospital mattresses. Contact interface pressure and blood perfusion give only a hypothetical conclusion about APAMs' effectiveness. Additional large, high-quality RCTs are needed. No conclusions can be drawn regarding the comfort of APAMs. A number of technical problems associated with APAMs are related to nurses' improper use of the devices.     

Human gallbladder pressure and volume: validation of a new direct method for measurements of gallbladder pressure in patients with acute cholecystitis

Summary. Increased gallbladder (GB) pressure is probably a part of the pathogenesis of acute cholecystitis, and measurements of GB pressure might therefore be of interest. The aim of this study was to validate a microtip pressure transducer for intraluminal GB pressure measurements. In vitro precision and accuracy was within 0.2 mmHg, (SD) and 0.6±0.1 mmHg (mean±SD), respectively. Pressure rise rate was 24.8±5.5 mmHgs^-1. Zero drift was in the range 0.3±0.4 to 0.8±0.9 mmHg (mean±SD). GB pressure was investigated in 16 patients with acute cholecystitis treated with percutaneous ultrasonically guided cholecystostomy. Basal intraluminal GB pressure was 8.9 mmHg (2.1–12.2 mmHg; n =9, open cystic duct) and 1.8 and 5.8 mmHg (n =2, closed cystic duct). There was no significant difference between two different measurements in the same patients (n =5). The pressure was significantly influenced by respiration (n =8) and the pressure seems to be higher in the sitting position than in the supine position (n =5). Cystic duct opening pressure was 10.4,11.2 and 16.8 mmHg (n =3). Pressure-volume responses showed that the GB up to a certain volume could accommodate increases in intraluminal volume with only slight changes in intraluminal pressure (n =4). Except for the zero drift, this piece of equipment seemed to fulfil the requirements of being able to measure pressure in the GB. In vivo measurements showed a good clinical reproducibility of the method, and also that respiration and patient posture influenced the pressure measurements. Further, a GB pressure-volume relationship was demonstrated, and the possibility of a cystic duct opening pressure was described.     

An exploration of the occurrence of pressure ulcers in a British spinal injuries unit

Spinal cord injury (SCI) is associated with increased risk of pressure ulcers, but there are few published data about this in the United Kingdom (UK). This article represents a quantitative exploration of the occurrence of pressure ulcers in a UK spinal injuries unit (SIU). The technique used is a retrospective review of records: details of 144 completed first admissions for SCI between 1998 and 2000 were entered on to a database (SPSS) for analysis. Thirty-two per cent of patients already had pressure ulcers on admission to the SIU, while a total of 56% experienced an ulcer at some stage between injury and discharge from the SIU. Four pressure ulcer risk assessment scales were used (Waterlow, Braden, Norton and SCIPUS-A). These appeared to have moderate predictive power in this population. Pressure ulcers were found to be associated with increased length of hospital stay, density of lesion, surgical stabilization of neck injury before transfer to the SIU, tracheostomy on admission to the SIU and delayed transfer to the SIU after injury. Implications for practice are discussed.     

Auscultatory mean blood pressure

This study examined the relationship between direct mean arterial blood pressure and cuff pressure for the maximum acoustic index calculated from the Korotkoff sounds in the dog. The acoustic index was computed by summing the squares of amplitudes in each Korotkoff sound complex, thereby providing a measure of acoustic energy content. Mean arterial pressure was compared with cuff pressure for the maximum acoustic index. Ten mongrel dogs were fitted with appropriately sized blood-pressure cuffs containing a microphone mounted inside the bladder and positioned over the brachial artery. The Korotkoff sounds, cuff pressure, and direct arterial pressure were recorded over a range of mean arterial pressures (23 to 155 mm Hg), achieved by manipulating the depth of anesthesia with halothane. It was found that cuff pressure at the maximum acoustic index overestimated mean arterial blood pressure by a mean of 14% (range, -8 to + 30%). Supported by grant HL31089 from the National Heart, Lung, and Blood Institute and sponsored in part by the Kendall Company, Barrington, IL.