Hospital survival rates of patients with acute respiratory failure in modern respiratory intensive care units. An international, multicenter, prospective survey.

An international, multicenter, prospective survey has been conducted to determine the hospital survival rates of patients with potentially reversible acute respiratory failure (ARF) who are managed in sophisticated intensive care units by leading critical care specialists, using current (1991 to 1992) support and treatment techniques and protocols. Twenty-five clinical centers participated in the survey, 11 in the United States and 14 in Europe. A total of 1,426 patients with ARF were studied, all of whom had been receiving closed system positive pressure mechanical ventilation at an FIo2 of at least 0.50 for at least 24 h at the time of entry into the survey. Of the survey patients, 793 (55.6%) survived their hospitalization, while 633 (44.4%) died in the hospital. The 1,426 patients with ARF were prospectively divided into two groups: group A, containing 375 patients, who at the time of entry into the study were hypoxemic or hypercarbic while receiving mechanical ventilator assistance; and group B, containing 1,051 patients, who at the time of entry into the study were neither hypoxemic nor hypercarbic while receiving mechanical ventilator support at an FIo2 of 0.50 or greater. Hospital survival rate for group A patients was 33.3% and for group B patients it was 63.6%. Survival rates were higher in patients with ARF caused by pneumonia (63%) or post shock lung injury (67%) and lower in patients with ARF caused by sepsis (46%). Severity of lung injury at the time of entry into the survey was a major prognostic factor, varying from an 18% hospital survival rate for patients with ARF with far advanced lung injury to a survival rate of 67% for patients with ARF with less severe lung injury. Low survival rates (< 20%) were seen if mechanical ventilator FIo2 was 0.80 to 1.0, while 50% of the patients with ARF survived hospitalization whose FIo2 at entry was 0.50. Peak inspiratory pressure (PIP) > 50 cm H2O at entry into the survey was associated with survival rate of less than 20%, while PIP < 30 cm H2O was associated with survival rate of 60%. Shorter periods of mechanical ventilation (< 48 h) of group A patients before entering the survey were associated with higher survival rates (38%) than patients requiring mechanical ventilation for more than 2 weeks (30%). Patients with ARF with multiorgan failure had lower survival rates (10%) than those with pulmonary dysfunction alone (45%).(ABSTRACT TRUNCATED AT 400 WORDS)

Rate of thrombus accumulation on intravenacaval IVOX devices explanted from human clinical trial patients with acute respiratory failure.

The weight gain of IVOX devices removed from the first 49 human clinical trials patients after from 1 to 29 days of implantation into the venae caval blood stream has been assessed. Each patient had received sufficient systemic heparin to maintain activated clotting times between 150 and 200 s while the IVOX device was indwelling. The nature of the material accumulating on the IVOX device was documented histologically as being thrombus in various stages of development. The weight gain findings indicate that an average of 2.0 g of thrombus accumulates per 24 h on IVOX devices indwelling in the venous blood stream of moderately anticoagulated human acute respiratory failure patients. The rate of weight gain per 24 h of the IVOX device was more rapid during the first 96 h after its implantation than during its second, third, or fourth week of implantation. The accumulated thrombus on the IVOX hollow fibers was associated with a small but measurable decrease (approximately 1%/day) in gas transfer efficiency of the implanted device. The data support the conclusion that IVOX can function effectively and safely without major thrombus formation for up to 29 days in moderately anticoagulated human acute respiratory failure patients.

Major findings from the clinical trials of the intravascular oxygenator.

Major clinically relevant findings have been extracted and summarized from the database developed from the international multicenter clinical trials of the intravascular oxygenator (IVOX) as a means for augmenting the deficient blood gas transfer of patients in advanced acute respiratory failure (ARF). Between February 1990 and May 1993, a total of 164 IVOX devices were utilized in 160 clinical trial patients who were hypoxemic and/or hypercarbic while receiving closed system positive pressure mechanical ventilator support at or exceeding generally accepted minimum safe levels of intensity. The average rates of oxygen and carbon dioxide transfer into and out of circulating venous blood by means of the IVOX device varied from 40-70 ml/min. Evidence of patient benefit during IVOX utilization includes improvement in blood gas partial pressures associated with decreased intensity of mechanical ventilation, improved hemodynamics in patients with mechanical ventilator depressed cardiovascular function, and decreased indices of lung dysfunction. Clinically recognized IVOX-related complications or adverse events were reported in 24.5% of the clinical trials patients. At necropsy examination of 68 clinical trials patients who died during or after IVOX utilization, forensic pathologists reported 4 cases in which IVOX utilization could have been a primary or contributing cause of death. Significant IVOX device mechanical and/or performance malfunction problems were recognized in 29 (17.7%) of the IVOX devices utilized in clinical trials. IVOX clinical trials data collected and analyzed to date indicate IVOX utilization has a favorable risk/benefit ratio in patients in severe, acute, potentially reversible ARF.

In vivo biocompatibility of catheter materials.

The inflammatory response to four different catheter materials was quantitatively characterized using an in vivo cage implant system over a 21 d implantation period. The greatest differences between materials were observed at day 4, where the total leucocyte concentration in the exudate decreased in the following order: AE-PVC greater than A-PU greater than D-PU1 greater than D-PU2. Similar trends were observed for the polymorphonuclear leucocyte (PMN) and macrophage concentrations at day 4. At day 7, this trend continued, but by day 21 the total leucocyte concentration, PMN concentration and macrophage concentration had decreased to comparable values for all materials. The extracellular alkaline phosphatase activity at day 4 was lowest for the AE-PVC exudate samples. Similar results were observed for the extracellular acid phosphatase activity but after that time point no significant differences were observed. From these results, it appears that AE-PVC is least biocompatible compared with the other three catheter materials, which were polyurethanes.

A numerical identification system for airways in the lung.

A numerical system for identifying airways at any level in the tracheobronchial tree has been developed which appears to be simple, logical, and accurate. The system has been successfully used in the authors' laboratory to expedite morphometric studies of the conducting airways in the tracheobronchial tree. Three simple and direct criteria or rules have been formulated for assignment of an airway identification number (AIN) to any specific pulmonary airway, according to this identification system. Some specific applications of this AIN system have been enumerated and several limitations that the authors have recognized have been described. Workers in the fields of bronchial morphometry and anatomy are invited to consider the possible theoretic and practical utility of this airway identification system.

Immediate mucosal effects of short-term, soft-cuff, endotracheal intubation. A light and scanning electron microscopic study.

Little is known regarding the early pathogenesis of intubation-induced laryngotracheal damage or the effects of presently used soft-cuff endotracheal tubes. We have examined the pathological changes of short-term intubation (four hours) in six mongrel dogs. Interaction of the endotracheal tube with the mucosa produced a variety of lesions ranging from superficial abrasions to ulcerations with the most severe lesions in the respiratory epithelium. Changes are present at the free surfaces of ciliated cells that include flattening, fusion, and erosion of cilia of sufficient extent to compromise ciliary function. The ischemic and mechanical modes of injury are compared; the latter is considered causal with modern soft-cuff tubes. These studies reveal tube-induced mucosal damage of an extent and nature not previously appreciated.