PA Catheters Research Articles

Alternative cardiac intensive care unit locations during the COVID-19 pandemic at an academic medical center

Alternative cardiac intensive care unit locations during the COVID-19 pandemic at an academic medical center

Inaugural Expert, Margaret Pisani, Talks Front-line COVID Care

Ask the Expert| July 2020 Inaugural Expert, Margaret Pisani, Talks Front-line COVID Care Zachary Deutch, MD, FASA Zachary Deutch, MD, FASA Search for other works by this author on: This Site PubMed Google Scholar ASA Monitor July 2020, Vol. 84, 22. https://doi.org/10.1097/01.M99.0000688724.71443.16 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn Email Cite Icon Cite Get Permissions Search Site Citation Zachary Deutch; Inaugural Expert, Margaret Pisani, Talks Front-line COVID Care. ASA Monitor 2020; 84:22 doi: https://doi.org/10.1097/01.M99.0000688724.71443.16 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentAll PublicationsASA Monitor Search Advanced Search Topics: beds, care of intensive care unit patient, covid-19, critical illness, health care systems, heart, hypoxemia, intensive care unit, intensivist, internship and residency Greetings, and welcome to the inaugural column of a recurring feature in the ASA Monitor. First, a crucial disclaimer: I (ZD) am not a Resident Expert, but instead a humble Master of Ceremonies who will provide access to clinicians and scientists across anesthesiology (and other fields of medicine). I will conduct print interviews with learned individuals, tap into their knowledge, and answer important questions relevant to anesthesia practice across the U.S. (and the world). Each column will have a specific area of interest (e.g., cardiac, regional, pediatric, practice management, medical ethics). To aid in this endeavor, I solicit all readers and ASA members – please send me questions you want answered or clinical conundrums you face. For example: “Are PA catheters still indicated in cardiac surgery? If so, which procedures, which patients?” “Are oral anxiolytic pre-medications worthwhile in... © 2020 American Society of Anesthesiologists (ASA), All Rights Reserved.2020 You do not currently have access to this content.

Systolic and Mean Pulmonary Artery Pressures: Are They Interchangeable in Patients With Pulmonary Hypertension?

Pulmonary hypertension (PH) is a common complication of numerous diseases, including left-sided heart diseases and chronic lung diseases and/or hypoxia, where PH is associated with exercise limitation and a worse prognosis. Other forms of PH include pulmonary arterial hypertension (PAH), chronic thromboembolic PH (CTEPH), and PH with unclear multifactorial mechanisms. Over the past decade, it has been documented that systolic pulmonary artery pressure (sPAP) may help estimate mean pulmonary artery pressure (mPAP) in adults with high accuracy and reasonably good precision (mPAP = 0.61 sPAP + 2 mm Hg). This strong linear relationship between sPAP and mPAP was unexpected from a classic physiologic point of view. Consistent results have been obtained from independent teams using either high-fidelity micromanometer-tipped PA catheters or fluid-filled catheters. Overall, the strong link between sPAP and mPAP has been documented over a wide range of PAPs, heart rate, cardiac output, wedge pressure, and causes of PH, during changes in posture and activity, and irrespective of patient's sex, age, and BMI. A review of available invasive data confirms that patients with CTEPH and idiopathic PAH matched for their mPAP exhibit essentially similar sPAP. Pressure redundancy may be explained by the dependence of PA compliance upon mPAP. The 25 mm Hg threshold used to define PH accurately corresponds to an sPAP of 38 mm Hg. Although the limits of the echocardiographic estimation of sPAP are widely documented, results from invasive studies may furnish an evidence-based sPAP-derived mPAP value, potentially useful in the multiparameter echocardiographic approach currently used to diagnose and follow patients with PH.

Comparison of complications and procedural activities of pulmonary artery catheter removal by critical care nurses versus medical doctors*

None of the nursing studies on PA catheter removal pointed out any differences in complications after removal and procedural activities for removal of PA catheter by CCNs vs MDs in Turkey. This quasi-experimental study was conducted to determine the occurrence and type of complications and to indicate the differences between CCNs and medical doctors' (MDs) activities for removal of PA catheter. Totally, 60 critical care unit patients were scheduled as a sample, and they were assigned randomly to the CCN (n = 30) or to the MD (n = 30) groups. For the comparison purposes of the different activities and complications of PA catheter removal procedure between the two groups, 'Instruction Form' was followed step by step. The differences in the prevalence of variables were tested using Student's t statistics. For categorical data, Fisher's exact test was used. Significance was declared by P value of <0.05. Preprocedural activities like patient positioning (P < 0.001) and instructing the patient for breathing (P = 0.001) demonstrated statistically significant differences between the two groups. The PA catheters were removed properly in both groups (P > 0.05). The majority of postprocedural activities were completed successfully. The complications of the catheter removal were documented more carefully by nurses compared with doctors (P < 0.01). Additionally, singular premature ventricular complexes were observed on electrocardiogram in both groups (P > 0.05). Instructing CCNs to remove a PA catheter has been highlighted in keeping the number of complications associated with removal procedure of PA catheter.

A SWINE MODEL OF HEMORRHAGIC SHOCK (HS) FOR THE DEVELOPMENT OF NOVEL MARKERS OF SHOCK SEVERITY

Currently available markers of shock severity are insensitive and fail to differentiate compensated from decompensated HS. OBJECTIVE: To develop a model of HS with a 5-hour mortality rate of near 50%, and to utilize this model to identify markers of shock severity and the transition from compensated to decompensated shock. METHODS: 25 anesthetized swine (20 - 25 kg) underwent splenectomy and placement of arterial, peripheral and portal venous, PA, and LV catheters, and liver microdialysis probes. Animals were bled to a mean arterial pressure (MAP) of 40mmHg, and maintained at that MAP for 90 minutes. After 90 min, animals were resuscitated to normal physiological parameters with shed blood and lactated Ringer's. Regional blood flow was measured via the microsphere technique. Animals were observed for 5 hrs following the 90- min shock period. RESULTS: 5-hour mortality was 56%. Mean survival times in Survivors (S) vs Nonsurvivors (NS) were 390(0) vs 174(77) minutes. Hemorrhage volumes were 29(7) and 28(7) ml/kg in S vs NS (p = 0.680; t-test). Standard parameters such as base deficit (BD) and arterial lactate (LAC) did not differ between S and NS (BD p = 0.380; LAC p = 0.365; rmANOVA). Cardiac output (CO) (p = 0.01), mixed venous O2 saturation (MVO2Sat) (p = 0.048), and O2 consumption (VO2) (p = 0.018) were significantly greater in S vs NS over time (rmANOVA). Ninety-minute CO, MVO2Sat, ileal blood flow (IBF), and VO2 were predictive of outcome (Table). Tissue and plasma cytokine data are pending. CONCLUSION: In this HS model, survival was not predicted by standard easily measured physiologic parameters, but was predicted by small bowel perfusion, CO, MVO2Sat, and VO2. These data suggest that future studies to define markers of shock severity should focus in these areas.Table

Cardiac anaesthesia: the last 10 years.

Cardiac anaesthesia: the last 10 years.

Thrombosis of Angiographic Catheters in Humans: Experimental Study

One of the major problems in the use of catheters is their thrombogenicity since the embolization of clots near the central nervous system or the coronary arteries can cause permanent damage. Catheter thrombogenicity was evaluated in humans during angiographic procedures by their tendency to become occluded. Characterization of catheters was achieved using roughness measurements, FTIR with ATR, DSC and ESCA. The catheters were 5 commercially available catheters, made mainly of polyethylene, Pebax or polyamide sterilized and ready for clinical use. Thirty-one patients due to have an angiographic procedure and with normal blood and hemodynamic parameters were included in the study. The 50 cm catheter test sample was inserted through an introducer into the femoral artery at the beginning of an angiographic procedure. The outcoming blood flow rate (BFR) was continuously monitored by a special computerized device for 15 min or until the total amount of blood reached 30 ml. The angiographic procedure was then normally resumed. DSC and FTIR showed results consistent with the expected composition of catheters. ESCA results showed very high Si/C ratios and could not be explained in all instances. Occlusion of the catheters occurred in 44% of the cases and the average time to obtain occlusion was 8.5 min (3-15 min). Values of the decrease rate of BFR in ml/min2 allowed separation of the catheters into 3 groups of low, medium and high thrombogenicity. However, occlusion occurred at least one time for each type of catheter. Blood volume and BFR curves vs. time allowed the determination of 3 main types of thrombotic behavior: type I shows no significant reduction of BFR; type II shows a progressive decrease in flow rate; type III is much less frequent and shows an abrupt decrease of BFR either quickly followed by a compensatory increase and resuming of a steady flow or by abrupt occlusion. In type II curves the pattern of occlusion follows a classical diffusion model because the Peclet number is greater than 1 and then the classical Higbie solution for diffusion could be used. The most thrombogenic material was the smoothest. There was no correlation between surface chemical composition and thrombogenicity. However, catheters that were based on PE appeared less thrombogenic than PA catheters in this study.

Continuous Mixed Venous (Svo2) Monitoring: Too Expensive or Indispensible?

Based on theoretic principles and clear literature support, SvO2 (mixed venous oxyhemoglobin) monitoring offers an important advantage over traditional hemodynamic parameters. SvO2 allows more precise understanding of the adequacy of cardiac and pulmonary function than traditional parameters. SvO2 values do not replace the need to measure individual parameters of oxygen delivery or consumption but serves as the standard for assessing the impact of each parameter on tissue oxygenation. SvO2 has the ability to reflect a threat to tissue oxygenation that is unmatched by other parameters. Its ability to give a real time indication of tissue oxygenation makes it a preferred parameter for monitoring the adequacy of hemodynamics. Its use as an end point for determining the adequacy of hemodynamics (BP, CO/CI), measurement of Qs/Qt, and prediction of potential hemodynamic instability make this parameter invaluable for the knowledgeable clinician. SvO2 catheters cost more than traditional PA catheters, a factor that has limited their acceptance as the standard PA catheter. The added cost of the SvO2 catheter has not been adequately addressed in the research literature. However, research does support SvO2 allows more rapid termination of drug therapies, may improve movement out of the ICU, and reduces the incidence of mechanical ventilator manipulation. These features increase the cost-effectiveness of SvO2 catheters. The cost-effectiveness of the catheter, like any technology, is predicated on the clinician. Clinicians++ must be educated to use SvO2 as a primary end point for treatment decisions regarding hemodynamic therapy and patient stability. If used properly, every PAC should use fiberoptic SvO2 capabilities.

A MULTI-FUNCTIONAL venous ACCESS DEVICE - A NEW ANSWER TO AN OLD PROBLEM?

S124 INTRODUCTION: Central venous access has become integral to the care of many surgical and medical patients. Historically, the decision was made to insert an introducer or multi-lumen catheter for access. However, the introduction of a new device from Baxter now offers the option of a single device to accomplish multiple functions with one stick. The object of this study was to compare maximal flow rates of this new device with other introducers utilizing the Haemonetics Rapid Infusion System (R.I.S.) and the more traditional pressurized I.V. system. TEST METHODS: The devices tested with the traditional I.V. system were: Baxter Advanced Venous Access (AVA) device which incorporates a 9F PA access with one distal (D) and two proximal lumens (P1&P2); Arrow 9F; Argon 9F. Test system consisted of blood, saline and D50W fluid bags pressurized to 300mmHg raised 40"; IV tubing was connected to each lumen tested and fluid volume measured after 1-2 min in a cylinder. with and without a PA catheter (Figure 1). Devices tested with the RIS were the Baxter AVA and the Arrow 9F, the most commonly used 9F introducer. Fluids measured were Saline and a Blood/Plasma mixture. The RIS was set up in a manner to continually infuse fluids through the device tested, using a cut-off pressure of 300 mmHg to judge maximum flow. Devices were tested with PA catheters (7.5F & 8F). Results for the AVA are shown in various configurations: AVA(1)=D+P1; AVA(2)=P1+P2; AVA(3)=D+P1+P2 (Figure 2).Figure 1: Saline with traditional systemFigure 2: RIS systemRESULTS: Flow rate results are below: DISCUSSION: In all categories, the Advanced Venous Access device delivered higher flows than the other introducers. Comparing AVA to previous triple lumen catheter studies, showed AVA delivered significantly higher flows. Therefore, the AVA device offers a new dimension in central access for trauma, critical care, and high blood loss surgeries (i.e., liver transplants). It now gives us the ability to monitor the circulation and infuse fluids with fewer venous punctures.

Improving the care of cardiothoracic surgery patients through advanced nursing skills

All the nurses in the cardiothoracic ICU are now certified in these advanced skills. The skills are reviewed with current staff members on a yearly basis during the annual evaluation. During their orientation to the cardiothoracic ICU, new staff nurses are certified by using the original process of attending an in-service training program and demonstrating the skill 3 times. The quality management department reviews medical records daily to detect complications. In addition, we (DRZ and MB) conducted a quality assurance review in which we monitored 20 patients being extubated and having PA catheters removed by nurses. No complications were noted during either review. The institution has seen improvements in quality of care and earlier discharge from the hospital. With earlier removal of endotracheal tubes and PA catheters, patients are more comfortable and their rehabilitation can be advanced sooner. Comparison of the mean length of stay for patients undergoing coronary artery bypass graft in March 1995 with the mean length of stay for such patients in March 1998 showed a 50.6% decrease, from 14.94 days to 7.38 days. These advanced skills have provided an increased autonomy for the nurses and have benefited the patients undergoing cardiac surgery in our institution.

ROUTINE ICU ADMISSION IS NOT REQUIRED AFTER CARDIAC SURGERY

S82 INTRODUCTION: Efficient resource utilization has resulted in a change in the way care is delivered to patients having cardiac surgery. [1] "Fasttrack" cardiac anesthesia allows early extubation and is part of any multidisciplinary "fasttrack" cardiac surgery program. Routine admission to ICU remains part of most "fasttrack" programs. Most patients are admitted because they are intubated and require cardiac monitoring. We present data that suggests that the admission to ICU after cardiac surgery is not required in the majority of cases. METHODS: In 1995, a "fasttrack" cardiac surgery protocol (we called our program a Facilitated Recovery Program; "fasttrack" may have some pejorative connotations) was developed in order to expand the program at our Centre. This includes "fasttrack" anesthesia, an initial 4-6 hour PACU-based recovery directed by both the Anesthesiologist and Cardiac Surgeon, elimination of routine ICU admission, and further recovery in a cardiac surgery stepdown unit (no facilities for IV vasodilators, vasopressors, mechanical ventilation, PA catheters, and maximum nurse:patient ratio 1:2). For this paradigm to become accepted, it was gradually introduced. In 1996, we initially selected 1 patient/week; by January 1997, most patients were being considered for this program. Final determination of recovery site is made after separation from CPB, and in some cases, after initial admission to PACU. We reviewed our OR, Health Records, ICU, and Cardiac Anesthesia databases for the years 1994-1997 for the pertinent data. Chi-square, Wilcoxon rank-sum, Mantel-Haenzel trend test, and ANOVA were used where appropriate to analyze the data. RESULTS: Most patients are extubated within 2 hours; the reintubation rate is low. There is a large reduction in ICU utilization (Table 1), shown as the % admissions and ICUdays/100cases/year (p<0.001, 1997 vs. all previous years and trend). The chance of ICU admission from stepdown is low. As expected, ICU LOS in 1997 was longer than in 1996 (p<0.01). APACHE II increased (p<0.01, 1997 vs. all previous yrs. as well as trend). There has been no significant change in mortality.Table 1DISCUSSION: A multidisciplinary program for cardiac surgery based on early extubation and PACU/stepdown-based recovery can dramatically and safely reduce ICU use. The acuity and LOS of patients admitted to the ICU increases, possibly reflecting a more prudent use of ICU resources. There may be large potential cost savings with this model of care. The majority of cardiac surgery patients can be considered for this type of Facilitated Recovery Program. As the number of patients in this study is relatively small, a ongoing analysis of the risk factors that may predict ICU admission is being done.

International Trauma Anesthesia and Critical Care Society (ITACCS)

International Trauma Anesthesia and Critical Care Society (ITACCS)

Effectiveness of Right Heart Catheterization: Time for a Randomized Trial

I agree with Dr Sharkey that our recommendation that the FDA issue a moratorium on the use of flow-directed PA catheters if an appropriately designed multicenter randomized controlled clinical trial of the use of PA catherization is not undertaken was a hard-line position. The statement by Dr Hoyt that the SCCM understands that it was our intent to stimulate the National Heart, Lung, and Blood Institute to undertake an appropriate randomized clinical trial is correct. It would appear from the response of the American College of Chest Physicians, the American College of Cardiology, and the Society of Critical Care Medicine that such a trial will be undertaken. It will be a very difficult and challenging trial. I hope that the trial will identify which subgroups of critically ill patients benefit from PA catherization and which subgroups do not.

Manipulating PA catheters carries responsibility

Articles| June 01 1995 Manipulating PA catheters carries responsibility TL Gomes TL Gomes Search for other works by this author on: This Site PubMed Google Scholar Crit Care Nurse (1995) 15 (3): 17. https://doi.org/10.4037/ccn1995.15.3.17 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Get Permissions Citation TL Gomes; Manipulating PA catheters carries responsibility. Crit Care Nurse 1 June 1995; 15 (3): 17. doi: https://doi.org/10.4037/ccn1995.15.3.17 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentCritical Care Nurse Search Advanced Search You do not currently have access to this content.

The RN's role in manipulation of pulmonary artery catheters.

Based on three surveys of critical care nursing practice around the United States, practice and opinion regarding the nurse's role in PA catheter manipulation is clearly varied. If it is determined that a change in practice is indicated, the scope of practice must be examined. The potential for risk to patients and a facility's cultural and political barriers require discussion and resolution. Policy guidelines, educational programming to teach the skills involved, and plans for competency verification are necessary. Our intention is not specifically to promote nurse manipulation of PA catheters. However, because some RNs perform this task, we advocate approved guidelines and adequate training.

Clinical utilization of pulmonary artery catheter monitoring.

Since the introduction of PA catheter monitoring in 1970, the applications for it have dramatically broadened. PA catheters are used to obtain hemodynamic data for the assessment, monitoring, and therapeutic management of critically ill, high-risk surgical patients. Because of potential complications associated with PA catheter monitoring, numerous editorials and articles have questioned the procedure's risk-to-benefit ratio. These articles address the inadequacy of outcome data and suggest no demonstrated benefit from PA monitoring. Subgroups of patients have been identified, however, in whom PA monitoring data altered clinicians' assessment and management. In spite of a study by Rao and colleagues implying that PA catheter monitoring can decrease the mortality rate in critically ill patients, no scientific study has confirmed this impression. A more recent article evaluated the impact of PA catheter monitoring on mortality with emphasis on how the information is used. This prospective study noted a potential benefit from PA catheter monitoring in a protocol group, but the limited sample size and selection criteria prevent definitive conclusions. Unfortunately, many of the reported studies are retrospective, nonrandomized, unblinded, limited in scope or size, and founded on subjective end points. Careful evaluation of individual studies is mandatory to avoid overinterpretation of the conclusions. Understanding the limits of PA monitoring is needed for therapy to be successful. Problems may stem not from technology but from the knowledge and expectations of clinicians. "Human" complications from inadequate understanding of the physiological data is not uncommon. Measured pressures by themselves can be misleading; indeed use of absolute numbers rather than trends or relative changes in the values monitored can compromise clinical assessment. Overzealous acceptance and utilization of any quantitative measurement without sound clinical judgment is fraught with failure.

Interobserver Variability in the Interpretation of Pulmonary Artery Catheter Pressure Tracings

We evaluated the ability of three independent reviewers (R1, R2, R3) using waveform analysis to accurately identify confirmed valid PCWP tracings, and their ability to consistently report the PCWP numerical value. Sixty PA and PCWP tracings were prospectively obtained and blindly reviewed by three independent critical care physicians. The medical ICU of Wilford Hall USAF Medical Center. Twenty mechanically ventilated patients with PA catheters inserted for hemodynamic assessment. Sixty PA and PCWP tracings were reviewed blindly and independently for acceptability using waveform criteria by three critical care physicians. While recording all 60 tracings, blood was aspirated from the distal port of the PA catheter with the balloon "wedged" and blood gas analysis was done. Each reviewer analyzed the PCWP tracings for validity using waveform criteria, and reported a numerical PCWP reading for those tracings judged valid by waveform criteria. Reviewer sensitivity, specificity and accuracy in performing waveform analysis were assessed by comparing their predictions with those tracings that were confirmed their predictions with those tracings that were confirmed valid by the aspiration of pulmonary capillary blood. Inter-reviewer agreement upon which validity of PCWP tracings was based and reviewer agreement on the numerical PCWP reading were also assessed. All tracings were blindly reviewed by each physician, first without and then with an AP tracing to define end-expiration. Thirty-eight of 60 PCWP tracings were confirmed valid by the aspiration of pulmonary capillary blood. In the remaining 22 tracings, mixed venous blood was aspirated with the balloon wedged, and tracing validity was unconfirmed. Reviewer accuracy in identifying was 50 percent for R1, 65 percent for R2 and 57 percent for R3. No reviewer's accuracy was significantly different from a random guess which would yield an accuracy of 50 percent. Agreement by all three reviewers in identifying valid PCWP tracings using waveform analysis varied from 37 percent in the absence of an AP tracing to 66 percent when an AP tracing was available to identify end-expiration (p less than 0.003). Agreement by all three reviewers on the PCWP numerical reading (within 4 mm Hg) was 79 percent without an AP tracing and 96 percent with an AP tracing (p = NS). The numerical reading reported by the ICU nurses and house staff correlated closely with the reviewers' readings. Agreement with the reported PCWP reading was improved only for R2 by the addition of an AP tracing. We conclude that the validation of PCWP tracings by waveform analysis is subject to interobserver variability, and reviewer accuracy in identifying confirmed valid tracings was no better than a random guess. Agreement on the numerical PCWP reading was high among the reviewers as was agreement by each individual reviewer with the reported PCWP. Finally, the presence of an AP tracing, to define end-expiration, adds little to the interpretation of the PCWP numerical reading by experienced physicians.

Pulmonary Artery Catheter Monitoring

Summary Since its introduction in 1970, the application for PA catheter monitoring has dramatically broadened. PA catheters provide the ability to obtain hemodynamic data for the assessment, monitoring, and therapeutic management of critically ill, high-risk surgical patients. Because of the potential complications associated with PA catheter monitoring, numerous editorials and articles have questioned the procedure’s risk-to-benefit ratio.36,66,67 These articles address the insufficient availability of adequate outcome data or suggest no demonstrated benefit from PA monitoring. Subgroups of patients have been identified in whom the data obtained from PA monitoring altered the clinicians’ assessment and management.20,28,41,82 In spite of the study of Rao et al,63 which implies that PA catheters can improve the mortality rate in critically ill patients, no scientific study of outcome has been able to confirm this impression. If an adequate understanding of the limitations of PA monitoring does not exist, appropriate selection and implementation of therapy cannot occur. The problem is not as much the technology as it is the knowledge and expectations of the clinician. “Human” complications from inadequate understanding of the physiologic data is quite common. Reliance on the measured pressure is often misleading. The use of “absolute numbers” rather than trends or relative changes in the values monitored can compromise clinical assessment. Overzealous utilization and acceptance of any quantitative measurement without coordination with clinical judgment is fraught with failure.

Invasive Cardiac Monitoring

Since its introduction in 1970, the application for PA catheter monitoring has dramatically broadened. PA catheters provide the ability to obtain hemodynamic data for the assessment, monitoring, and therapeutic management of critically ill patients. Because of the potential complications associated with PA catheter monitoring, numerous editorials and articles have questioned the procedure's risk to benefit ratio. These articles address the insufficient availability of adequate outcome data or suggest no demonstrated benefit from PA monitoring. Subgroups of patients have been identified in whom the data obtained from PA monitoring altered the clinician's assessment and management. In spite of the study of Rao, which implies that PA catheters can improve mortality in critically ill patients, no scientific study of outcome has been able to confirm this impression. If an adequate understanding of the limitations of PA monitoring does not exist, appropriate selection and implementation of therapy cannot occur. The problem is not as much the technology, as it is the knowledge and expectations of the clinician. "Human" complications from inadequate understanding of the physiologic data are quite common. Reliance on the measured pressure is often misleading. The use of "absolute numbers" rather than trends or relative changes in the values monitored can compromise clinical assessment. Overzealous utilization and acceptance of any quantitative measurement without coordination with clinical judgment is fraught with failure.

Effect of positive-end expiratory pressure on accuracy of thermal-dye measurements of lung water

The thermal-dye indicator dilution technique of measuring extravascular lung water (EVLW- TD) correlates well with gravimetric measurement of lung water (EVLW- GR) when no positive-end expiratory pressure (PEEP) is used in both normal and edematous lungs. PEEP is often used to raise arterial oxygen tension in acute respiratory failure. This study was designed to answer the question: Does PEEP have an effect on the accuracy of the EVLW measurement by thermal dye? Sixteen mongrel dogs were anesthetized and intubated. Arterial and PA catheters were placed. They were divided into three groups and ventilated at PEEP levels of 5, 10, or 15 cm H 2O. Fluids were given to minimize decrease in cardiac output with institution of PEEP. They were maintained for 5 hr with measurement of vital signs made hourly and measurement of blood gases and EVLW-TD made at baseline, 1, 3, and 5 hr. After final measurements, gravimetric determination of EVLW was done. Correlation between EVLW TD and EVLW GR remained good when low levels of PEEP were used. At 5 cm H 2O PEEP, EVLW TD was 7.5 ± 0.9 and EVLW GR was 5.4 ± .3. At 10 cm H 2O PEEP, they were 10.0 ± 0.9 and 6.5 ± 0.3. The correlations were 0.87 and 0.97, respectively. However, at 15 cm H 2O PEEP, EVLW TD was 11.4 ± 1.3 and EVLW GR was 7.5 ± 0.6, with a correlation of only 0.59. The correlation between the two techniques seems to break down with higher levels of PEEP in dogs with normal lungs.