Diving physiology and pathophysiology

Summary. Divers have worked at 500 m depth in the sea and have reached 700 m in simulated chamber dives. A prerequisite for this has been extensive physiological studies of the body's reactions to pressure and pressure changes. This paper reviews such physiological and pathophysiological studies with emphasis on recent developments.     

中老年人24小时动态血压变化的研究

目的探讨血压正常老年患者和老年高血压患者24h动态血压波动规律及与靶器官损害的关系.方法采用无创伤袖带式动态血压监测仪检测36例中年人(对照组),50例血压正常老年患者,60例老年高血压患者的动态血压.结果血压正常老年患者较中年血压正常者24h动态血压呈杓型曲线的比例明显下降.血压正常老年患者,血压昼夜波动曲线与心、脑、肾损害无相关性.老年高血压患者,血压曲线呈非杓型者比例增高,血压昼夜节律消失较节律正常的高血压患者有更显著的靶器官损害.结论对于非高血压患者,随年龄的增加,血压昼夜节律消失者增多,血压曲线变化与心、脑、肾损害无关,可能与原发病有关.对于高血压患者,血压昼夜节律紊乱可作为靶器官损害的预测因子.     

Ten-year stability of cardiovascular responses to laboratory stressors

In this study we examined test-retest stability of cardiovascular stress responses over a decade of the life span. Participants were 55 male college undergraduates. 19 years of age at initial testing, and 29 years of age at follow-up testing Stressors were a foot cold pressor and an aversive reaction time task. Cardiovascular measures included systolic and diastolic blood pressure, heart rate, and preejection period. For cold pressor, the magnitude and pattern of cardiovascular responses remained unchanged at the 10-year follow-up. For the reaction time task, the characteristic cardiovascular response patterns was preserved but with significant attenuation of magnitude. The present findings are consistent with previous observations of temporal stability but over a substantially longer test-retest interval. The long-term stability of stress responses is discussed in the context of stress test methodology, behavioral response demands, and maturation of the physiological systems involved in cardiovascular response expression.     

Raised intracranial pressure,the syndrome of inappropriate antidiuretic hormone secretion,and arginine vasopressin in tuberculous meningitis

Intracranial pressure (ICP) monitored shortly after admission over a period of 1 h in 31 children with tuberculous meningitis (TBM) was significantly higher (median 22.5 mm Hg, range 8.4–50.9 mmHg) in 19 children with laboratory evidence of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) than in 12 children without such evidence (median 16.2 mmHg, range 5.8–42.5 mmHg; P = 0.027). Neither plasma nor cerebrospinal fluid arginine vasopressin (AVP) was related to ICP (r = 0.33 and 0.13 respectively). Mean arterial pressure (MAP) was measured in 23 children and a moderate correlation was found with plasma AVP (r = 0.62; P = 0.0019). In TBM, plasma AVP may be secreted as a response to raised ICP in an effort to raise MAP and maintain cerebral perfusion pressure. In this setting excess fluid may be inappropriately retained, leading to hyponatremia and hypo-osmolemia.     

The role of the chest X-ray in the evaluation of chronic severe heart failure: things are not always as they appear

The chest x-ray has become a standard clinical test to aid in the evaluation of patients with chronic severe heart failure. To evaluate just how useful this tool is in the routine assessment of pulmonary venous hypertension secondary to heart failure, we compared the radiologist's interpretation of the chest x-ray with hemodynamic data obtained from right heart catheterization in a group of patients undergoing protocol evaluation of an experimental treatment for heart failure. Of 23 patients with pulmonary venous hypertension (pulmonary capillary wedge pressure greater than 20 mmHg) and a complete data base, only 11 had chest x-rays showing evidence of pulmonary venous congestion or interstitial or alveolar edema. The sensitivity of the chest x-ray in selecting patients with a pulmonary capillary wedge pressure over 20 mmHg in this setting was only 48%. In other studies, where the radiologist was aware that his or her reading was being compared to hemodynamic assessments, the sensitivity of the chest film has approached 85%. We feel our analysis more closely parallels routine clinical practice. Clinicians should be aware that the chest x-ray may not be a very sensitive tool for the assessment of pulmonary hemodynamics in patients with severe heart failure.     

R波相关振动法血压测量

为了提高振地血压测量的准确性，提出了一咱基于心电Ｒ波与血压振动波之间相关性，识别振动信号的一种抗干扰方法＝－Ｒ波相关法，结合振动波形特征识别，该方法可有效地提取信号，消除干扰影响，该算法已在１６位８０９８单片机上实现，本文同时给出了程序的详细流程图。     

压力调节容量控制通气对肺损伤犬血流动力学、呼吸力学和呼吸功能的影响

目的 探讨压力调节容量控制(PRVC)通气模式对健康及急性肺损伤(ALI)模型犬的血流动力学、呼吸力学和呼吸功能的影响。方法 PRVC和间歇正压通气(IPPV)两种通气模式在呼气末压为0、0．5、1．0和1．5kPa时，分别测定健康犬及油酸诱发ALI犬的血流动力学、呼吸力学及血气参数。结果 健康犬PRVC较IPPV模式下除了在PEEP为0．5kPa时，气道峰压(PIP)、肺动态顺应性(Cdyn)和肺血管阻力(PVR)的影响差异有显著性，对血流动力学、呼吸力学及呼吸功能的影响差异均无显著性。ALI犬PRVC较IPPV模式下各PEEP水平的PIP、平均气道压(mPaw)、Cdyn、动脉血氧分压[pa(O2)]和氧耗(VO2)的影响均有显著意义，但两种通气模式对血流动力学的影响差异无显著性。结论 与IPPV相比，PRVC通气模式能降低PIP，增加Cdyn和提高pa(O2)，两模式对血流动力学的影响差异无显著性，PRVC更适用于ALI／ARDS的治疗。     

山莨菪碱和无创面罩正压通气治疗急性呼吸窘迫综合征的临床观察

目的比较山莨菪碱联合无创正压面罩通气（654-2＋NIPPV）和传统机械通气（CMV）治疗急性呼吸窘迫综合征（ARDS）的临床效果，评估山莨菪碱联合无创正压通气在ARDS治疗中的作用。方法将各种原因所致ARDS患者42例随机分为654-2＋NIPPV组（21例）和CMV组（21例），在给予病因治疗同时分别实施654-2＋NIPPV和CMV。观察分析两组患者在治疗过程中动脉血气变化、并发症的发生率及治疗效果。结果654-2＋NIPPV组有8例（38．1％）治疗失败转为气管插管实行CMV，其中6例（28．6％）死亡。CMV组死亡7例（33．3％），两组病死率无显著差异（P〉0.05）。两组治疗有效的患者在分别接受654-2＋NIPPV和CMV治疗后1h和6h动脉血气有相似的显著改善。654-2＋NIPPV组患者机械通气时间和住院时间短于CMV组（P〈0.05）。654-2＋NIPPV组的并发症发生率低于CMV组（P〈0.05）。结论在经过选择的ARDS患者中，应用654-2＋NIPPV治疗的临床效果与CMV相似。实施654-2＋NIPPV可缩短机械通气和住院时间，减少并发症。654-2＋NIPPV可作为经过选择的ARDS患者首选的通气支持治疗手段。     

Relative nocturnal hypertension in children with insulin-dependent diabetes mellitus

Twenty-four-hour blood pressure and heart rate measurements were carried out in 14 newly diagnosed diabetics and in 28 diabetics with 5–13 years' duration of the disease; 8 healthy children were used as controls. Mean arterial blood pressure increased at night in 5, decreased slightly (less than 10%) in 5 and decreased markedly (more than 10%) in 18 diabetics with longer duration of the disease. The diurnal-nocturnal differences in heart rates were significantly lower in diabetics with relative "nocturnal hypertension" compared to the control group ( p < 0.05). A significant negative correlation was found between maximal arterial blood pressure during physical exercise and the diurnal-nocturnal differences in mean arterial blood pressure in diabetics ( r =−0.58; p < 0.02). In conclusion, we found elevated nocturnal blood pressure in a subgroup of children with longer duration of diabetes and without increased albumin excretion. However, longitudinal studies of blood pressure profiles are needed to identify the candidates for diabetic vasculopathy among diabetic children.