Fluid input control in burned patients with the aid of ultrasonic arterial blood pressure monitoring.

Arterial blood pressure is nowadays easily and reliably measured with ultrasonic equipment. It correlates well with blood volume, and may therefore be used to guide fluid infusion in burned patients. Monitoring of blood pressure, instead of application of old-fashioned recipes, helps to avoid dangerous situations of hypovolemia or overload.     

Noninvasive positive-pressure ventilation in acute respiratory failure

Noninvasive positive-pressure ventilation is a type of mechanical ventilation that does not require an artificial airway. Studies published in the 1990s that evaluated the efficacy of this technique for the treatment of diseases as chronic obstructive pulmonary disease, congestive heart failure and acute respiratory failure have generalized its use in recent years. Important issues include the selection of the ventilation interface and the type of ventilator. Currently available interfaces include nasal, oronasal and facial masks, mouthpieces and helmets. Comparisons of the available interfaces have not shown one to be clearly superior. Both critical care ventilators and portable ventilators can be used for noninvasive positive-pressure ventilation; however, the choice of ventilator type depends on the patient''s condition and therapeutic requirements and on the expertise of the attending staff and the location of care. The best results (decreased need for intubation and decreased mortality) have been reported among patients with exacerbations of chronic obstructive pulmonary disease and cardiogenic pulmonary edema.Noninvasive positive-pressure ventilation is the delivery of mechanical ventilation to patients with respiratory failure without the requirement of an artificial airway. The key change that led to the recent increase in the use of this technique occurred in the early 1980s with the introduction of the nasal continuous positive airway pressure mask for the treatment of obstructive sleep apnea. Studies published in the 1990s that evaluated the efficacy of noninvasive positive-pressure ventilation for treatment of diseases such as chronic obstructive pulmonary disease, congestive heart failure and acute respiratory failure have generalized its use in recent years.¹ In 1998, an international study on the use of mechanical ventilation found that 5% of patients admitted to intensive care units received noninvasive positive-pressure ventilation.²Noninvasive positive-pressure ventilation includes various techniques for augmenting alveolar ventilation without an endotracheal airway. The clinical application of noninvasive ventilation by use of continuous positive airway pressure alone is referred to as “mask CPAP,” and noninvasive ventilation by use of intermittent positive-pressure ventilation with or without continuous positive airway pressure is called noninvasive positive-pressure ventilation.     

Opioid peptides attenuate blood pressure increase in acute respiratory failure

Plasma opioid peptides, norepinephrine, atrial natriuretic factor (ANF) and blood pressure (BP) were assessed in 24 chronic obstructive pulmonary disease patients with acute respiratory failure. Hypoxemic-hypercapnic patients had high BP, beta-endorphin, Met-enkephalin and dynorphin B, whereas hypoxemic-normocapnic and hypoxemic-hypocapnic patients showed normal BP, high beta-endorphin, and normal Met-enkephalin and dynorphin B. Norepinephrine and ANF were high in all patients, particularly in hypoxemic-hypercapnic patients. Infusion with the opioid antagonist naloxone hydrochloride significantly increased systolic blood pressure (SBP) in hypoxemic-hypercapnic (182.0 +/- 3.2 versus 205.1 +/- 3.0 mmHg; P < 0.01), hypoxemic-normocapnic (149.3 +/- 1.8 versus 169.1 +/- 2.2 mmHg; P < 0.01) and hypoxemic-hypocapnic (147.3 +/- 1.3 versus 166.8 +/- 2.2 mmHg; P < 0.01) patients, norepinephrine in hypoxemic-hypercapnic patients (3583.2 +/- 371.8 versus 5371.3 +/- 260.0 fmol/ml; P < 0.01), and reduced ANF in hypoxemic-normocapnic (18.3 +/- 0.8 versus 11.9 +/- 1.0 fmol/ml; P < 0.05) and hypoxemic-hypocapnic (18.1 +/- 1.2 versus 12.1 +/- 2.1 fmol/ml; P < 0.05) patients. These results indicate that the endogenous opioid system attenuates SBP responses in acute respiratory failure by affecting norepinephrine or ANF release.     

Determinants of an elevated pulmonary arterial pressure in patients with pulmonary arterial hypertension

Given the difficulty of diagnosing early-stage pulmonary arterial hypertension (PAH) due to the lack of signs and symptoms, and the risk of an open lung biopsy, the precise pathological features of presymptomatic stage lung tissue remain unknown. It has been suggested that the maximum elevation of the mean pulmonary arterial pressure (P_pa) is achieved during the early symptomatic stage, indicating that the elevation of the mean P_pa is primarily driven by the pulmonary vascular tone and/or some degree of pulmonary vascular remodeling completed during this stage. Recently, the examination of a rat model of severe PAH suggested that the severe PAH may be primarily determined by the presence of intimal lesions and/or the vascular tone in the early stage. Human data seem to indicate that intimal lesions are essential for the severely increased pulmonary arterial blood pressure in the late stage of the disease.However, many questions remain. For instance, how does the pulmonary hemodynamics change during the course of the disease, and what drives the development of severe PAH? Although it is generally acknowledged that both pulmonary vascular remodeling and the vascular tone are important determinants of an elevated pulmonary arterial pressure, which is the root cause of the time-dependent progression of the disease? Here we review the recent histopathological concepts of PAH with respect to the progression of the lung vascular disease.     

烧伤合并急性肾功能衰竭的早期指标检测

目的:探讨烧伤合并急性肾功能衰竭(ARF)的早期指标检测以及各种危险因素.方法:选择本院2008年1月～2009年6月收治的75例中重度热烧伤患者.Ⅱ度或ⅡⅢ度烧伤面积累计20%-70%TBSA.所有患者在入院时、入院后3d、7d、14d和21d检测血清肌酐(Scr)、血尿素氮(BUN)、尿微量白蛋白(mALB)和滤过钠排泄分数(FeNa).结果:75例烧伤患者中有14例(18.7%)并发ARF,其中10例进行了血液净化治疗.烧伤合并ARF组烧伤面积和脓毒症发生率均明显高于烧伤未合并ARF组(P均＜0.05).烧伤合并ARF组Scr和BUN水平分别在住院7d和14d后明显高于烧伤未合并ARF组(P均＜0.05).烧伤合并ARF组入院时mALB水平已达到正常值34倍,21d时达到最大值,在观察期间一直高于烧伤未合并ARF组(P均＜0.05).烧伤合并ARF组滤过钠排泄分数均大于2%.烧伤面积与脓毒症是烧伤后ARF发生的主要危险因素(复相关系数R分别为0.52和0.23,P均＜0.05).结论:烧伤合并ARF与烧伤面积与脓毒症相关,mALB是早期监测ARF的有用指标.     

Lower inflection point and recruitment with PEEP in ventilated patients with acute respiratory failure.

The lower inflection point (LIP) on the total respiratory system pressure-volume (P-V) curve is widely used to set positive end-expiratory pressure (PEEP) in patients with acute respiratory failure (ARF) on the assumption that LIP represents alveolar recruitment. The aims of this work were to study the relationship between LIP and recruited volume (RV) and to propose a simple method to quantify the RV. In 23 patients with ARF, respiratory system P-V curves were obtained by means of both constant-flow and rapid occlusion technique at four different levels of PEEP and were superimposed on the same P-V plot. The RV was measured as the volume difference at a pressure of 20 cm H(2)O. A third measurement of the RV was done by comparing the exhaled volumes after the same distending pressure of 20 cm H(2)O was applied (equal pressure method). RV increased with PEEP (P < 0.0001); the equal pressure method compares favorably with the other methods (P = 0.0001 by correlation), although individual data cannot be superimposed. No significant difference was found when RV was compared with PEEP in the group of patients with a LIP < or =5 cm H(2)O and the group with a LIP >5 cm H(2)O (76.9 +/- 94.3 vs. 61.2 +/- 51.3, 267.7 +/- 109.9 vs. 209.6 +/- 73.9, and 428.2 +/- 216.3 vs. 375.8 +/- 145.3 ml with PEEP of 5, 10, and 15 cm H(2)O, respectively). A RV was found even when a LIP was not present. We conclude that the recruitment phenomenon is not closely related to the presence of a LIP and that a simple method can be used to measure RV.     

Seasonal variation in arterial blood pressure.

Blood pressure measurements recorded during the medical Research Council''s treatment trial for mild hypertension have been analysed according to the calendar month in which the readings were made. For each age, sex, and treatment group systolic and diastolic pressures were higher in winter than in summer. The seasonal variation in blood pressure was greater in older than in younger subjects and was highly significantly related to maximum and minimum daily air temperature measurements but not to rainfall.     

Intravenous naloxone in acute respiratory failure.

A 58-year-old man presented with acute on chronic respiratory failure. In the acute stage of his illness an infusion of the opiate antagonist naloxone caused an improvement in oxygen saturation as measured by ear oximetry from 74% to 85%, while a saline infusion resulted in a return of oxygen saturation to the original value. When he had recovered from the acute episode the same dose of naloxone had no effect on oxygen saturation. These findings suggest that in acute respiratory failure there may be overproduction of, or increased sensitivity to, endorphins.     

Noninvasive assessment of pulmonary arterial hypertension by MR phase-mapping method.

We describe a magnetic resonance (MR) imaging method that emphasizes pressure wave velocity to noninvasively assess pulmonary arterial hypertension. Both the blood flow and the corresponding vessel cross-sectional area (CSA) were measured by MR phase mapping in the main pulmonary artery (MPA) in 15 patients. MPA pressures were also measured, in the same patients, by right-side heart catheterization. Two significant relationships were established: 1) between the pressure wave velocity in the MPA and the mean pressure in the MPA (Ppa) writing pressure wave velocity = 9.25 Ppa - 202.51 (r = 0.82) and 2) between the ratio of pressure wave velocity to the systolic blood velocity peak in the MPA (R) and the mean pressure in the MPA writing R = 0.68 Ppa - 4.33 (r = 0.89). Using these relationships, we estimated two pressure values to frame the actual Ppa value in each patient from the present series with a reasonable reliability percentage (87%).     

Relation between peripheral chemoreceptors stimulation and pulmonary arterial blood pressure in rats

As interactions between peripheral chemoreceptors stimulation (PCS) and pulmonary vasomotor tone remain controversial, experiments were made in rats in order to clear up the effects of PCS on pulmonary arterial pressure (PAP). Different stimulations varying in intensities were used, in rats nervously intact (IR-rats), after vagotomy (XT-rats), after chemodenervation obtained without vagotomy (CDN not XT-rats) or with XT (CDN + XT) and finally after alpha 1-receptors blockade (P-rats = pretreated rats). The observed variations were analysed in view of disentangling reflex part of PCS from a direct activity on the pulmonary vascular bed. Ventilation, PAP and systemic blood pressure (BP) were studied in anaesthetized rats. N2 test, NaCN test, 20 s of 5% O2 inhalation and almitrine bismesylate (ALM) were used as PCS, ranged in the order of their relative intensities, from the ventilatory responses observed in IR-rats. In IR-rats, N2-and CN test produced a similar transient increase of PAP, slightly more extended than the hyperventilation. After XT, the responses were prolonged, but amplified only in CN test. Ventilatory responses disappear after CDN, but as far as pulmonary hypertension is concerned, CDN + XT is more potent than CDN without XT to reduce or even suppress them. This fact is particularly evident with ALM who is the strongest PCS used. Similar reduction of PAP rise was also produced in P-rats in which ventilatory responses remain unchanged. Prolonged hypoxic inhalation induced a progressive fall of systolic BP and of PAP. The return to normal air breathing is followed by BP restoration and a long-lasting PAP increase.(ABSTRACT TRUNCATED AT 250 WORDS)     

综合护理模式对慢性阻塞性肺疾病急性加重合并Ⅱ型呼吸衰竭患者的影响

目的探讨综合护理模式对无创呼吸机治疗慢性阻塞性肺疾病急性加重(AECOPD)合并Ⅱ型呼吸衰竭患者的临床疗效。方法选取2013年1月~2016年1月我院收治行无创呼吸机治疗的AECOPD合并Ⅱ型呼吸衰竭患者120例,随机分为对照组和实验组各60例,对照组采用常规护理模式,实验组在常规护理模式的基础上给予综合护理干预,分别采用焦虑自评量表(SAS)、抑郁自评量表(SDS)对AECOPD合并Ⅱ型呼吸衰竭患者护理前后进行评分,分析护理前后两组患者血气分析指标、SAS评分、SDS评分及护理满意度情况。结果护理前,两组患者的动脉血气分析指标(PO2、PCO2、pH)、SAS评分、SDS评分比较,差异无统计学意义(P0.05)。护理后,两组患者动脉血气分析指标(PO2、PCO2、pH)均有改善,实验组的各项指标改善程度显著优于对照组,SAS评分和SDS评分均低于对照组,患者满意度(96.7%)显著高于对照组(78.3%),差异均有统计学意义(均P0.01)。结论综合护理可显著提高无创呼吸机治疗AECOPD合并Ⅱ型呼吸衰竭患者的临床疗效,有效缓解其焦虑及抑郁情绪,提高患者护理满意度。     

Analysis of pulmonary arterial pressure profile after occlusion of pulsatile blood flow

In isolated canine lung lobes perfused with a pulsatile pump, arterial occlusions were performed and the postocclusion arterial pressure profiles were analyzed to estimate the pulmonary capillary pressure. A solenoid valve interposed between the pump and the lobar artery was used to perform arterial occlusions at several instants equally distributed within a pressure cycle. Double occlusions were also accomplished by simultaneously activating the solenoid valve and clamping the venous outflow of the lung lobe. To analyze an arterial occlusion pressure profile, we computed the best monoexponential fit of the pressure decay over a short period of time after the occlusion maneuvers. Two estimates of the capillary pressure were derived from this analysis: 1) the extrapolation of the exponential fit to the instant of occlusion, and 2) the point at which the recorded pressure decay curve merges with the exponential fit. The pressures thus determined were compared with the double occlusion pressure that provided an independent estimate of the pulmonary capillary pressure. Our results show that, under a wide range of conditions, the estimates of the capillary pressure obtained from the arterial occlusion data are nearly equal to the double occlusion pressures. Additionally, we estimated the capillary pressure variations within a pressure cycle by examining the occlusion pressures sampled at different instants of the cycle. The pulsatility of the pulmonary microvascular pressure varied with the pump frequency as well as the state of arterial and venous vasoaction. These variations are consistent with the representation of the lung vasculature as a low-pass filter.     

Possibilities of using non-invasive techniques to predict pulmonary arterial pressure in chronic respiratory diseases]

The value of non-invasive procedures for predicting pulmonary arterial pressure (PAP) was assessed in 297 patients with chronic obstructive lung disease (COLD) and in 73 patients with alveolitis in multicenter trials at 9 centres in 6 European countries. FEV1, blood gases, ECG, radiographic dimensions of the pulmonary artery, right ventricle dimensions measured with M-mode echocardiography, and 201Ta heart scintigraphy together with clinical examinations served the purpose. No single variable was correlated closely enough to allow precise prediction of PAP. In patients with COLD multiple stepwise analysis of regression explained 49% of the variance in PAP but was not useful for prediction. Discriminant analysis allowed patients allocation to PAP bands similarly to 2 non-parametric procedures in which decision trees were established with the aid of either Kolmogoroff-Smirnoff statistics or Fishers' exact test. Patients with PAP of 30 mm Hg or higher were identified with sensitivity of 83% and specificity of 91%. Non-parametric tests produced better results than discriminant functions. Additional 54 patients were tested to validate these functions. Ninety percent of them with PAP > 20 mm Hg, and 80% with PAP > 29 mm Hg were identified correctly. Similar results were achieved in patients with fibrosing alveolitis. These mathematical functions allow the use of non-invasive procedures combinations to select those individuals out the populations at risk of pulmonary hypertension in whom direct PAP measurements are required. These mathematical functions may further be widen by addition of other variables obtained from newer non-invasive techniques.     

Increases in intramuscular pressure raise arterial blood pressure during dynamic exercise.

This investigation was designed to determine the role of intramuscular pressure-sensitive mechanoreceptors and chemically sensitive metaboreceptors in affecting the blood pressure response to dynamic exercise in humans. Sixteen subjects performed incremental (20 W/min) cycle exercise to fatigue under four conditions: control, exercise with thigh cuff occlusion of 90 Torr (Cuff occlusion), exercise with lower body positive pressure (LBPP) of 45 Torr, and a combination of thigh cuff occlusion and LBPP (combination). Indexes of central command (heart rate, oxygen uptake, ratings of perceived exertion, and electromyographic activity), cardiac output, stroke volume, and total peripheral resistance were not significantly different between the four conditions. Mechanical stimulation during LBPP and combination conditions resulted in significant elevations in intramuscular pressure and mean arterial pressure from control at rest and throughout the incremental exercise protocol (P < 0.05). Conversely, there existed no significant changes in mean arterial pressure when the metaboreflex was stimulated by cuff occlusion. These findings suggest that under normal conditions the mechanoreflex is tonically active and is the primary mediator of exercise pressor reflex-induced alterations in arterial blood pressure during submaximal dynamic exercise in humans.