ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The right ventricle (RV) is responsible for accepting venous blood and propelling it to the lungs where it is oxygenated and its CO2eliminated. Under normal conditions, at rest and during exercise, the pressure required by the RV to maintain the cardiac ouptut (CO) is modest. The functional significance of the RV in sustaining circulatory homeostasis, therefore, appears to be minimal. However, whenever pulmonary vascular resistance (PVR) is elevated (e.g., left heart failure or pulmonary vascular disease) or whenever venous return is reduced (e.g., hypovolemia, increased pleural pressure), the necessity of this pulsatile pump is without question.As a muscular pump, the thin-walled RV is not unlike the left ventricle (LV) except that during diastole it is twice as distensible as the LV and during systole its stroke volume is twice as sensitive to the level of ejection pressure. However, under conditions of chronic pressure overload, the RV will hypertrophy and become capable of generating systemic levels of pressure. This is particularly necessary during physical activity in patients with pulmonary vascular disease. Thus, the RV is an integral component of the body's gas transport system and its contribution to sustaining circulatory homeostasis is without question.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

This review evaluates noninvasive techniques for assessing cardiovascular performance in acute and chronic respiratory failure. Radiographic, radionuclide, and echocardiographic methods for determining ventricular volumes, right (RV) and left ventricular (LV) ejection fractions, and pulmonary artery pressure (PAP) are emphasized. These methods include plain chest radiography, radionuclide angiocardiography, thallium-201 myocardial imaging, and M mode and 2-dimensional echocardiography, which have recently been applied in patients to detect pulmonary artery hypertension (PAH), right ventricular enlargement, and occult ventricular performance abnormalities at rest or exercise. Moreover, radionuclide angiocardiography has proven useful in combination with hemodynamic measurements, for evaluating the short-and long-term cardiovascular effects of therapeutic agents, such as oxygen, digitalis, theophylline, β-adrenergic agents, and vasodilators.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

In critically ill patients, alterations in pulmonary vasomotor tone profoundly influence right ventricular (RV) function. An increase in end-diastolic volume (EDV) follows elevations in the RV afterload, this increase in preload probably subserving the increased RV stroke work (SW) required to ensure unchanged RV pump function. The maintenance of a normal left ventricular (LV) preload is essential in the cardiovascular adaptation to an acute illness. With volume overload of the RV consequent upon pulmonary artery hypertension (PAH), leftward septal shift occurs and reduces LV diastolic compliance. With extremely high levels of RV loading conditions, a depression in RV contractility and reduced RV pump function are eventually seen, both of which then become partially responsible for LV pump failure.Hence, abnormalities in RV function will have a marked clinical influence on the circulatory response seen in critically ill patients. Future investigation should be directed toward the effects of augmenting or improving RV function with pharmacologic agents in this patient population.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The pathophysiology and managements of right ventricular (RV) dysfunction in acute respiratory failure (ARF) is complicated. Results presented in this paper indicate that volume expansion may not be appropriate therapy to maintain or increase cardiac output (CO) when flow is reduced because of increased RV afterload. Volume will increase RV wall stress and O2requirements so that despite increased preload, CO may fall. If RV afterload is significantly increased, such changes can occur despite a relatively normal RV end-diastolic pressure (RVEDP). Further, increased RV afterload and/or volume expansion can result in increased RV volumes and secondary alteration in left ventricular (LV) diastolic mechanics. Such changes, especially if wedge pressure increases, would tend to increase pulmonary edema. Also, because of potential changes in viscosity and pulmonary vascular resistance (PVR), packed red blood cells may not be indicated to increase CO, arterial O2content and tissue O2delivery in the setting of ARF.Therapy designed to reduce PVR may be appropriate to increase flow in the setting of increased RV afterload. However, such therapy may also reduce systemic vascular resistance, blood pressure (BP) and RV perfusion pressure. Such changes could lead to RV ischemia and reduced CO. Alternatively, agents which increased RV perfusion and/or contractility will increase CO by reducing RV end-diastolic and end-systolic volumes and may be the treatment of choice to increase flow when RV afterload is elevated.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Anecdotal observations suggest that high frequency jet ventilation (HFJV) is beneficial in major airway disruption. Quantitative evaluation is, however, unavailable. In 12 healthy mongrel dogs, a tracheal window of increasing size, from 0.5 × 1 cm to 1.5 × 2 cm, was opened. Dogs were supported on volume-cycled ventilation (VCV) and on HFJV, using injector cannulas of 1.06 and 1.62 mm internal diameter. The tracheal window was then closed and an upper lobectomy performed, followed by total pneumonectomy. Arterial blood gases were obtained after 10 min in each experimental condition. VCV could maintain life-supporting blood gases only with the tracheal window of 0.5 × 1 cm. HFJV, delivered with a 1.06-mm injector cannula, was adequate with a tracheal window of 1 × 1 cm, or after a lobectomy. In all experimental conditions, HFJV delivered with a 1.62-mm injector effectively maintained alveolar ventilation and arterial oxygenation.Gas transport on HFJV is based, in part, on the principles of jet mixing and entrainment; increasingly large tidal volumes can be delivered under conditions of low and constant pressure. Air leaks through pathological openings remain constant even when tidal volume is increased, so that alveolar ventilation can be adequately maintained.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Ten randomly selected patients were ventilated for defined periods with 2 ventilatory modes: (a) high frequency positive pressure ventilation (HFPPV) (frequency 66–70 min; tidal volume 1–3 ml/kg body weight), (b) conventional IPPV (frequency 16/min; tidal volume (VT) 10–15 ml/kg). This was done successfully using conventional ventilators, and keeping other variables (FIO2, PEEP) constant. Various ventilatory and hemodynamic variables were measured and compared during both modes of ventilation.The most prominent finding was a considerable reduction of cardiac output (CO) and stroke volume (SV) during intermittent positive pressure ventilation (IPPV) compared with HFPPV. Peak tracheal pressure was significantly lower during HFPPV. An increase in mean systemic arterial pressure and in oxygen transport was observed during HFPPV, whereas transpulmonary shunt and pulmonary vascular resistance (PVR) decreased during HFPPV.These findings are in accordance with previously reported advantages of HFPPV, and might be of importance in the treatment of patients with bronchopleural fistula, adult respiratory distress syndrome (ARDS), left ventricular failure and other conditions in which conventional positive pressure ventilation (PPV) fails.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Retrospective analysis of pulmonary barotrauma incidence in 292 patients ventilated ≥24 h was conducted. From 1971–1973, 156 patients with acute respiratory insufficiency were managed with controlled mechanical ventilation (CMV) and PEEP. During 1973–1976, 136 patients were supported with IMV and CPAP. Despite higher mean peak and end-expiratory airway pressure, the IMV-CPAP group exhibited a significantly lower incidence of ventilator-induced barotrauma; 7% vs 22% (p< 0.01). We suspect the difference is related to fewer mechanical breaths with IMV and not to the level of end-expiratory pressure employed.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The purpose of this study was to assess the incidence, evolution and long-term effects of laryngotracheal lesions due to endotracheal intubation and to evaluate the import of factors in the genesis of laryngotracheal injury. Over a 12-month period, we performed fiberoptic bronchoscopy (FBS) in 19 critically ill patients with endotracheal intubation. Early laryngeal lesions, mainly true vocal cord granulomas and ulceration, appeared in 12 (63%) patients and were resolved by the 3rd month in all but 3 patients. In 6 (31%) patients, early tracheal lesions appeared in the form of ring-shaped tracheitis at the cuff level and granulomas at the tube-tip level; in 2 (10%) patients, an established tracheal stenosis developed and early detected ring-shaped tracheitis preceded circumferential fibrous stenosis. Severe respiratory failure, high cuff pressure, and secretion infection showed a statistical correlation to tracheal injury.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Intracranial pressure (ICP) was increased by hyperosmolar intracerebral infusion in dogs and the cardiopulmonary and catecholamine (CA) responses followed for 4 h. Increased ICP evoked persistent increases in endogenous CAs, pulmonary vascular pressures, pulmonary blood volume, and venous admixture. Other dogs similarly monitored were treated with a β-blocking dose of propranolol 25 min after the onset of increased ICP. Although catecholamines were increased, elevated pulmonary pressures and venous admixture returned to control levels. CO and heart rate (HR) were reduced after β blockade but systemic vascular resistance increased. It was concluded that increased ICP induces sustained increases in CAs which adversely affect pulmonary pressures and shunting. Selective β blockade reverses these effects and may be useful in patients with evidence of sympathetic overactivity and progressive hypoxemia after head injury.

ISSN:0090-3493    

出版商:OVID    

年代:1983

数据来源: OVID