摘要:

We evaluated changes in left ventricular (LV) geometry in ten dogs during intermittent positive-pressure ventilation (IPPV) with and without 10 cm H2O of positive end-expiratory pressure (PEEP). The dimensions during expiration and inspiration decreased in all three orthogonal axes during PEEP, consistent with decreased LV end-diastolic (ED) and end-systolic (ES) volumes. Within a respiratory cycle, the anterior-posterior (AP) ED dimension during inspiration increased with IPPV alone but decreased when PEEP was added, consistent with presumed differences in pulmonary venous return. This caused opposite changes in AP percent regional shortening. Septal-lateral free wall (SL) percent regional shortening decreased during inspiration with both IPPV and PEEP, but the respiratory variation was significantly less during PEEP. Thus, PEEP did not simply produce a smaller version of the same events seen during IPPV alone. The larger decreases with PEEP observed in ED compared to ES – dimensions in the AP and SL axes suggest a dominant – regional preload effect, whereas the larger fall in the long axis ES compared to ED dimension suggests a primary regional decrease in afterload. Measurements of the right ventricular SL axis in three dogs showed an overall reduction with PEEP, with the inspiratory dimensions being minimal during both IPPV alone and with PEEP. Thus, ventricular interdependence cannot account for the diminished LV SL dimension with PEEP during any part of the respiratory cycle. These findings suggest that the motion of the LV free wall influenced by changes in lung volume may be at least as important as septal motion in determining LV geometry with PEEPWe conclude that it is possible to consider the respiratory effects of ventilation on LV performance as the sum of multiple regions, in a manner analogous to that presently used with arteriosclerotic heart disease.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

We followed 1018 patients admitted consecutively to a multidisciplinary respiratory ICU (RICU), with special attention to patients aged 75 yr and over. The elderly had a higher RICU (11/49) and in-hospital (21/49) mortality than younger patients. The 28 survivors of hospitalization had a lower acute physiology score (APS) than nonsurvivors on admission (16.1 ± 7.8 vs. 21.8 ± 8.9, respectively), indicating less severe illness. The quality of long-term survival (12 to 24 months) was assessed using an open-ended questionnaire. Eighteen hospital survivors were alive at the time of follow-up and the quality of life was deemed satisfactory by 10 of 13 patients who were living independently. Only two of 28 survivors had been transferred to nursing home care, and two were in acute care hospitalsWe conclude most elderly patients discharged from the RICU consider their lifestyle satisfactory and are not a large drain on community health care resources. Further studies of the screening process which determines RICU admission are necessary, because unimodal criteria such as age and APS after admission were not of prognostic value.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Transcutaneous Pco2(PtcCO2) measurements were used to monitor changes in systemic lactate levels during exercise. Ptcco2increased in all 17 male volunteers, and this increase was significantly correlated with increases in measured plasma lactate concentration. In six volunteers, the Ptcco2increase was greatest during the last minutes of work, indicating rapid lactic acid elimination from the muscles. In these six subjects, the rate of this increase also correlated significantly with the lactate increase.This technique is potentially of interest for detecting fatigue in athletes and for monitoring lactoacidosis as an indicator of circulatory impairment in shock patients.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

A constant-volume plethysmograph was used to measure functional residual capacity (FRC) in anesthetized dogs before, during, and after high-frequency oscillatory ventilation (HFO). The phrenic nerves were electrically stimulated to provide the necessary respiratory effort. In addition to FRC, mean alveolar pressure (PA) was obtained from the pressure axis of the static pressure/volume (P/V) curve at FRC. In eight dogs, the first min of HFO at 22 ml, 20 Hz, and a 4 L/ min bias flow of air increased FRC by an average of 63.6% above the apneic value, where it remained for the subsequent 15 min. PA values were significantly higher than mean airway pressures (Paw) measured in the endotracheal tube, indicating higher pressure in the terminal lung units. In five other dogs, FRC, Paw, and mean pleural pressure increased as HFO was increased from 15 to 30 Hz with 1 and 4 L/min bias flows of air. We speculate that these increases may account for both the impairment of cardiovascular function and improvements in oxygen tensions often seen with HFO.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The mean airway pressure difference within a respiratory cycle at end-inspiration was measured at different tidal volumes (Vt) in 59 patients treated with mechanical ventilation, and plotted in a pressure-volume (P-V) diagram. Regression analysis revealed three types of regression lines which were clearly correlated with clinical pulmonary condition and outcome. The slope of such regression lines may be a more realistic representation of lung elasticity than conventional total static compliance, which is measured at only one Vt, and the intercept of these lines may be a more appropriate reflection of operating lung volume than functional residual capacity. Ventilator settings should put the patient's lungs on the steepest part of the P-V curve with the smallest intercept, while maintaining acceptable arterial blood gas tensions.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

High-frequency positive-pressure ventilation (HFPPV) was compared to intermittent positive-pressure ventilation (IPPV) during unilateral atelectasis with and without halothane anesthesia. Dogs with electromagnetic flow probes chronically implanted on their main (Qt) and left (Qt) pulmonary arteries were ventilated via Carlen's dual-lumen endotracheal tubes. In eight closed-chest dogs, about 43% of the cardiac output perfused the left lung during bilateral ventilation by either a Harvard animal respirator (IPPV) or a Healthdyne model 300 high-frequency ventilator (HFPPV). Unilateral atelectasis decreased blood flow (Qt/Qt) to that lung. Q1/Qtwas 19 ± 1% with HFPPV during leftlung atelectasis and right-lung ventilation, compared to 32 ± 1% with unilateral IPPV. This suggests that HFPPV permits stronger hypoxic pulmonary vasoconstriction. Addition of 1% halothane increased blood flow to the atelectatic left lung during unilateral ventilation with IPPV but not with HFPPV. This suggests that halothane decreases the effects of hypoxic pulmonary vasoconstriction during conventional ventilation but not during HFPPV.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

We compared the blood culture results obtained either by venipuncture or through an arterial catheter in 51 critically ill patients with 217 clinically suspected episodes of bacteremia. During each episode, three blood culture samples, two arterial and one venous, were drawn within 1 h. One or more cultures were positive in 42 (19%) of the episodes, but there were great discrepancies between the results obtained by the two methods. In only eight cases did both methods give the same microorganism. In eight other episodes, the two arterial cultures were positive while the venous sample was negative, probably indicating a continuous contamination of the catheter system.Pseudomonas aeruginosaandStaphylococcus epidermidiswere the two most common microbes. The frequency of positive arterial catheter blood cultures did not increase with the length of catheter use. We conclude that an arterial catheter is not a reliable sampling site for blood cultures and does not replace the conventional venipuncture method.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Sixty-five surgical ICU patients at high risk of developing acute erosive gastritis and bleeding received prophylactic antacid treatment to maintain a gastric pH of at least 5.0. A similar control group of 61 patients received no specific prophylaxis.All patients in both groups developed microscopic bleeding; however, microscopic bleeding did not influence outcome. In the control group, eight (13.1%) patients developed moderate visible bleeding, as compared to seven (10.8%) patients in the antacid group, an insignificant difference. A single patient in the control group developed severe GI bleeding due to acute erosive gastritis.Antacid prophylaxis did not prevent macroscopic bleeding and there was no correlation between the number of risk factors in individual patients and the rate of upper GI bleeding. We conclude that antacid is not required to prevent upper GI bleeding in high-risk critically ill patients.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

In a prospective study of pH control for stress ulcer prophylaxis, intermittent iv infusion of the anticholinergic drug pirenzepine maintained the intragastric pH above 4 in only one of 17 ICU patients, while similar administration of the H2-receptor antagonist ranitidine was successful in seven of 32 patients. This difference was not statistically significant. Of 15 patients in whom a maximum dose of 600 mg/day of ranitidine or 90 mg/day of pirenzepine failed to maintain pH, combination therapy was successful in 11, a significant (p< .01) improvement.We conclude that neither ranitidine nor pirenzepine provides adequate control of pH for stress ulcer prophylaxis when used alone. If used together they are the most effective combination so far described for parenteral control of gastric pH in the critically ill. Regular monitoring of gastric pH is nevertheless essential to allow detection of therapeutic failures.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Preliminary studies indicate that nicergoline, a new alpha-antagonist, can lower HR at doses which decrease arterial BP. The present animal study was designed to quantitate the systemic and carotid (pulsed Doppler) hemodynamic and renin release consequences of nicergoline ventricular unloading, and to investigate the hemodynamic mechanisms of hypotension. In 11 anesthetized dogs, nicergoline infusion induced progressive, moderate, and prolonged hypotension associated with reduced vascular resistance and capacitance. Hypotension resulted from decreased HR and cardiac output, without an increase in plasma renin activity. The effects on carotid hemodynamics were less marked than those on the systemic circulation. Hypotension was caused primarily by vasoplegia, and was magnified subsequently by inhibition of the reflex rapid pressor control mechanisms. This suggests that repeated iv doses of nicergoline are preferable to prolonged infusion.

ISSN:0090-3493    

出版商:OVID    

年代:1985

数据来源: OVID