Comparison of pulmonary artery and central venous pressure waveform measurements via digital and graphic measurement methods.

BACKGROUND: Techniques to measure pulmonary artery (PA) pressure waveforms include digital measurement, graphic measurement, and freeze-cursor measurement. Previous studies reported the inaccuracy of digital and freeze-cursor measurements. However, many of the previous studies were small and did not thoroughly examine the circumstances of when digital measurements might be inaccurate. OBJECTIVES: To compare digital measurements and graphic measurements of PA and central venous pressure (CVP) waveforms in patients with a variety of respiratory patterns, and to compare digital measurements and graphic measurements of CVPs in patients with abnormal or right ventricular waveforms. METHODS: A total of 928 patients were enrolled in this study. Waveforms from the PA and CVP were collected from each patient. The monitor pressure value (digital measurement) printed on the recorded waveform was compared with the pressure value obtained by a graphic strip recording and measured by one of the primary investigators (graphic measurement). RESULTS: Digital measurements were found to be inaccurate in measuring waveforms in all respiratory categories and in measuring right ventricular waveforms. PA diastolic values and CVP values were the most inaccurately measured waveforms. Digital errors of more than 4 mm Hg were common. CONCLUSION: There were instances in which the monitor's digital measurement was substantially different from the graphically measured value. This difference has the potential to mislead interpretation of clinical situations. The monitor's ability to occasionally give digital measurement values similar to the graphic measurements may lead to a false sense of security in clinicians. Because the accuracy of the monitor is inconsistent, the bedside clinician should interpret waveforms through use of a graphic recording rather than rely on the digital measurement on the monitor.

Clinical predictors and outcomes for patients requiring tracheostomy in the intensive care unit.

OBJECTIVE: To identify clinical predictors for tracheostomy among patients requiring mechanical ventilation in the intensive care unit (ICU) setting and to describe the outcomes of patients receiving a tracheostomy. DESIGN: Prospective cohort study. SETTING: Intensive care units of Barnes-Jewish Hospital, an urban teaching hospital. PATIENTS: 521 patients requiring mechanical ventilation in an ICU for >12 hours. INTERVENTIONS: Prospective patient surveillance and data collection. MEASUREMENTS AND MAIN RESULTS: The main variables studied were hospital mortality, duration of mechanical ventilation, length of stay in the ICU and the hospital, and acquired organ-system derangements. Fifty-one (9.8%) patients received a tracheostomy. The hospital mortality of patients with a tracheostomy was statistically less than the hospital mortality of patients not receiving a tracheostomy (13.7% vs. 26.4%; p = .048), despite having a similar severity of illness at the time of admission to the ICU (Acute Physiology and Chronic Health Evaluation [APACHE] II scores, 19.2 +/- 6.1 vs. 17.8 +/- 7.2; p = .173). Patients receiving a tracheostomy had significantly longer durations of mechanical ventilation (19.5 +/- 15.7 days vs. 4.1 +/- 5.3 days; p < .001) and hospitalization (30.9 +/- 18.1 days vs. 12.8 +/- 10.1 days; p < .001) compared with patients not receiving a tracheostomy. Similarly, the average duration of intensive care was significantly longer among the hospital nonsurvivors receiving a tracheostomy (n = 7) compared with the hospital nonsurvivors without a tracheostomy (n = 124; 30.9 +/- 16.3 days vs. 7.9 +/- 7.3 days; p < .001). Multiple logistic regression analysis demonstrated that the development of nosocomial pneumonia (adjusted odds ratio [AOR], 4.72; 95% confidence interval [CI], 3.24-6.87; p < .001), the administration of aerosol treatments (AOR, 3.00; 95% CI, 2.184.13; p < .001), having a witnessed aspiration event (AOR, 3.79; 95% CI, 2.30-6.24; p = .008), and requiring reintubation (AOR, 2.21; 95% CI, 1.54-3.18; p = .028) were variables independently associated with patients undergoing tracheostomy and receiving prolonged ventilatory support. Among the 44 survivors receiving a tracheostomy in the ICU, 38 (86.4%) were alive 30 days after hospital discharge and 31 (70.5%) were living at home. CONCLUSIONS: Despite having longer lengths of stay in the ICU and hospital, patients with respiratory failure who received a tracheostomy had favorable outcomes compared with patients who did not receive a tracheostomy. These data suggest that physicians are capable of selecting critically ill patients who most likely will benefit from placement of a tracheostomy. Additionally, specific clinical variables were identified as risk factors for prolonged ventilatory assistance and the need for tracheostomy.

Effect of a nursing-implemented sedation protocol on the duration of mechanical ventilation.

OBJECTIVE: To compare a practice of protocol-directed sedation during mechanical ventilation implemented by nurses with traditional non-protocol-directed sedation administration. DESIGN: Randomized, controlled clinical trial. SETTING: Medical intensive care unit (19 beds) in an urban teaching hospital. PATIENTS: Patients requiring mechanical ventilation (n = 321). INTERVENTIONS: Patients were randomly assigned to receive either protocol-directed sedation (n = 162) or non-protocol-directed sedation (n = 159). MEASUREMENTS AND MAIN RESULTS: The median duration of mechanical ventilation was 55.9 hrs (95% confidence interval, 41.0-90.0 hrs) for patients managed with protocol-directed sedation and 117.0 hrs (95% confidence interval, 96.0-155.6 hrs) for patients receiving non-protocol-directed sedation. Kaplan-Meier analysis demonstrated that patients in the protocol-directed sedation group had statistically shorter durations of mechanical ventilation than patients in the non-protocol-directed sedation group (chi-square = 7.00, p = .008, log rank test; chi-square = 8.54, p = .004, Wilcoxon's test; chi-square = 9.18, p = .003, -2 log test). Lengths of stay in the intensive care unit (5.7+/-5.9 days vs. 7.5+/-6.5 days; p = .013) and hospital (14.0+/-17.3 days vs. 19.9+/-24.2 days; p < .001) were also significantly shorter among patients in the protocol-directed sedation group. Among the 132 patients (41.1%) receiving continuous intravenous sedation, those in the protocol-directed sedation group (n = 66) had a significantly shorter duration of continuous intravenous sedation than those in the non-protocol-directed sedation group (n = 66) (3.5+/-4.0 days vs. 5.6+/-6.4 days; p = .003). Patients in the protocol-directed sedation group also had a significantly lower tracheostomy rate compared with patients in the non-protocol-directed sedation group (10 of 162 patients [6.2%] vs. 21 of 159 patients [13.2%], p = .038). CONCLUSIONS: The use of protocol-directed sedation can reduce the duration of mechanical ventilation, the intensive care unit and hospital lengths of stay, and the need for tracheostomy among critically ill patients with acute respiratory failure.

The use of continuous i.v. sedation is associated with prolongation of mechanical ventilation.

STUDY OBJECTIVE: To determine whether the use of continuous i.v. sedation is associated with prolongation of the duration of mechanical ventilation. DESIGN: Prospective observational cohort study. SETTING: The medical ICU of Barnes-Jewish Hospital, a university-affiliated urban teaching hospital. PATIENTS: Two hundred forty-two consecutive ICU patients requiring mechanical ventilation. INTERVENTIONS: Patient surveillance and data collection. MEASUREMENTS AND RESULTS: The primary outcome measure was the duration of mechanical ventilation. Secondary outcome measures included ICU and hospital lengths of stay, hospital mortality, and acquired organ system derangements. A total of 93 (38.4%) mechanically ventilated patients received continuous i.v. sedation while 149 (61.6%) patients received either bolus administration of i.v. sedation (n=64) or no i.v. sedation (n=85) following intubation. The duration of mechanical ventilation was significantly longer for patients receiving continuous i.v. sedation compared with patients not receiving continuous i.v. sedation (185+/-190 h vs 55.6+/-75.6 h; p<0.001). Similarly, the lengths of intensive care (13.5+/-33.7 days vs 4.8+/-4.1 days; p<0.001) and hospitalization (21.0+/-25.1 days vs 12.8+/-14.1 days; p<0.001) were statistically longer among patients receiving continuous i.v. sedation. Multiple linear regression analysis, adjusting for age, gender, severity of illness, mortality, indication for mechanical ventilation, use of chemical paralysis, presence of a tracheostomy, and the number of acquired organ system derangements, found the adjusted duration of mechanical ventilation to be significantly longer for patients receiving continuous i.v. sedation compared with patients who did not receive continuous i.v. sedation (148 h [95% confidence interval: 121, 175 h] vs 78.7 h [95% confidence interval: 68.9, 88.6 h]; p<0.001). CONCLUSION: We conclude from these preliminary observational data that the use of continuous i.v. sedation may be associated with the prolongation of mechanical ventilation. This study suggests that strategies targeted at reducing the use of continuous i.v. sedation could shorten the duration of mechanical ventilation for some patients. Prospective randomized clinical trials, using well-designed sedation guidelines and protocols, are required to determine whether patient-specific outcomes (eg, duration of mechanical ventilation, patient comfort) can be improved compared with conventional sedation practices.

Is nursing education adequate for pulmonary artery catheter utilization?

OBJECTIVE: To review the literature addressing the nursing education of pulmonary artery catheterization. DATA SOURCE: All pertinent English language articles dealing with nursing education and pulmonary artery catheterization were retrieved from 1983 through 1996. STUDY SELECTION: Clinical studies related to nursing education in this field were selected. Only two studies addressing nursing knowledge of pulmonary artery catheterization have been published to date. DATA EXTRACTION: Both studies suggest that an improvement in several areas of nursing knowledge is necessary. Unfortunately, these studies are limited in scope and depth. DATA SYNTHESIS: The adequacy of nursing education in hemodynamic monitoring, ranging from cognitive to technical issues, has not been addressed in a systematic fashion in the literature. CONCLUSION: Nurses need a standardized hemodynamic monitoring curriculum. At present, education of nurses is primarily institutionally based. While national guidelines exist for hemodynamic monitoring, no mechanisms are in place to verify the skills of individual nurses. Since physicians depend on the knowledge and skill of the bedside nurse to obtain accurate information, any study evaluating the impact of pulmonary artery catheterization should first control for nursing knowledge. Since this information is not currently known, the precise impact of pulmonary artery catheterization cannot be assessed at this time.

A randomized, controlled trial of protocol-directed versus physician-directed weaning from mechanical ventilation.

OBJECTIVE: To compare a practice of protocol-directed weaning from mechanical ventilation implemented by nurses and respiratory therapists with traditional physician-directed weaning. DESIGN: Randomized, controlled trial. SETTING: Medical and surgical intensive care units in two university-affiliated teaching hospitals. PATIENTS: Patients requiring mechanical ventilation (n = 357). INTERVENTIONS: Patients were randomly assigned to receive either protocol-directed (n = 179) or physician-directed (n = 178) weaning from mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: The primary outcome measure was the duration of mechanical ventilation from tracheal intubation until discontinuation of mechanical ventilation. Other outcome measures included need for reintubation, length of hospital stay, hospital mortality rate, and hospital costs. The median duration of mechanical ventilation was 35 hrs for the protocol-directed group (first quartile 15 hrs; third quartile 114 hrs) compared with 44 hrs for the physician-directed group (first quartile 21 hrs; third quartile 209 hrs). Kaplan-Meier analysis demonstrated that patients randomized to protocol-directed weaning had significantly shorter durations of mechanical ventilation compared with patients randomized to physician-directed weaning (chi 2 = 3.62, p = .057, log-rank test; chi 2 = 5.12, p = .024, Wilcoxon test). Cox proportional-hazards regression analysis, adjusting for other covariates, showed that the rate of successful weaning was significantly greater for patients receiving protocol-directed weaning compared with patients receiving physician-directed weaning (risk ratio 1.31; 95% confidence interval 1.15 to 1.50; p = .039). The hospital mortality rates for the two treatment groups were similar (protocol-directed 22.3% vs. physician-directed 23.6%; p = .779). Hospital cost savings for patients in the protocol-directed group were $42,960 compared with hospital costs for patients in the physician-directed group. CONCLUSION: Protocol-guided weaning of mechanical ventilation, as performed by nurses and respiratory therapists, is safe and led to extubation more rapidly than physician-directed weaning.

Experimental therapies to support the failing lung.

Many conventional therapies are designed to treat acute lung injury. Although evidence exists that improved outcomes are a result of these therapies, mortality remains high in this population. Perhaps one of the key reasons why mortality remains high in the failing lung population is that current therapies do not "cure" the problem; current therapies are designed to support the lung, rather than fix the pulmonary problem. In this paper, a review of new and experimental therapies to support the failing lung are presented. Therapies such as prone positioning, nitric oxide, and mediator therapies are addressed. It is likely that newer therapies offer the most hope for improving the high mortality associated with acute lung injury.

Effects of mechanical ventilation on hemodynamic waveforms.

Interpreting hemodynamic waveforms in the critically ill patient requires an understanding of the influence of breathing on waveform values. Included in this understanding is differentiating between physiologic changes associated with breathing and artifact associated with an atmospheric (not pleural) referenced transducer system. Techniques such as airway pressure measurement can aid the clinician in the identification of specific points in the respiratory cycle. This article provided a review of the major respiratory factors influencing waveform values, both physiologic and artifactual. Application of principles outlined in this article should improve the accuracy associated with interpreting hemodynamic waveforms.