Pulmonary Artery Occlusion Pressure Measurements Research Articles

Lung ultrasound predicts well extravascular lung water but is of limited usefulness in the prediction of wedge pressure.

Pulmonary congestion is indicated at lung ultrasound by detection of B-lines, but correlation of these ultrasound signs with pulmonary artery occlusion pressure (PAOP) and extravascular lung water (EVLW) still remains to be further explored. The aim of the study was to assess whether B-lines, and eventually a combination with left ventricular ejection fraction (LVEF) assessment, are useful to differentiate low/high PAOP and EVLW in critically ill patients. The authors enrolled 73 patients requiring invasive monitoring from the intensive care unit of four university-affiliated hospitals. Forty-one patients underwent PAOP measurement by pulmonary artery catheterization and 32 patients had EVLW measured by transpulmonary thermodilution method. Lung and cardiac ultrasound examinations focused to the evaluation of B-lines and gross estimation of LVEF were performed. The absence of diffuse B-lines (A-pattern) versus the pattern showing prevalent B-lines (B-pattern) and the combination with normal or impaired LVEF were correlated with cutoff levels of PAOP and EVLW. PAOP of 18 mmHg or less was predicted by the A-pattern with 85.7% sensitivity (95% CI, 70.5 to 94.1%) and 40.0% specificity (CI, 25.4 to 56.4%), whereas EVLW 10 ml/kg or less with 81.0% sensitivity (CI, 62.6 to 91.9%) and 90.9% specificity (CI, 74.2 to 97.7%). The combination of A-pattern with normal LVEF increased sensitivity to 100% (CI, 84.5 to 100%) and specificity to 72.7% (CI, 52.0 to 87.2%) for the prediction of PAOP 18 mmHg or less. B-lines allow good prediction of pulmonary congestion indicated by EVLW, whereas are of limited usefulness for the prediction of hemodynamic congestion indicated by PAOP. Combining B-lines with estimation of LVEF at transthoracic ultrasound may improve the prediction of PAOP.

Validation of the Vascular Pedicle width as a Diagnostic Aid in Critically Ill Patients with Pulmonary Oedema by Novice Non-Radiology Physicians-in-Training

Assessing intravascular volume status in the critically ill patient remains a challenge for intensivists, and the accuracy of such estimation based on bedside examination alone is reported to be nearly a coin toss. In this retrospective study we sought to validate a previously recommended chest radiographic vascular pedicle width (VPW) ≥70 mm for identifying cardiogenic pulmonary oedema (CPO). We additionally assessed whether novice physicians-in-training can reliably measure the VPW. The study included intensive care patients with an existing pulmonary artery catheter. Three independent raters performed measurements of VPW from chest radiographs obtained within three hours of pulmonary artery occlusion pressure measurements. In 80 patients enrolled, a VPW cut-off of ≥70 mm had a 55% sensitivity, 88% specificity, 81% positive predictive value, 69% negative predictive value and 73% accuracy for identifying patients with CPO. Receiver operating characteristic curve analysis showed an area under the curve of 0.72 (95% confidence interval 0.61 to 0.84) for VPW in discriminating CPO from non-cardiogenic pulmonary oedema. Kappa statistics for inter-rater reliability showed Kappa=0.41, 0.42 and 0.85 for each pair of the three raters. In conclusion, the previously accepted VPW cut-off of ≥70 mm is reasonably accurate in discriminating CPO from non-cardiogenic pulmonary oedema. VPW can be measured by physicians-in-training with a comparable performance to previous studies utilising expert radiologists.

Hemodynamic Monitoring in the ICU

This review examines the most commonly used hemodynamic monitoring devices in the intensive care unit. After a brief review of some important issues in hemodynamic monitoring, a variety of monitoring systems are considered, including arterial catheters, pulmonary artery catheters (PACs), less invasive hemodynamic monitors, central venous oxygen saturation (ScvO2) monitors, and point-of-care (POC) echocardiography. For each system, the basic operating principles, indications and limitations of use, complications, key issues in data interpretation, and evidence regarding utility in patient care are reviewed. Figures depict the distinction between correlation and agreement, a representative Bland-Altman plot, a square wave test, PAC waveforms, principles of pulmonary artery occlusion pressure measurement, measuring pulmonary artery occlusion pressure at end-exhalation, right atrial and ventricular pressure waveform, pulmonary artery pressure waveform, potential pulmonary artery occlusion waveforms, west zones of the lung and the pulmonary artery occlusion pressure measurements, and POC echocardiography. Tables outline landmarks during insertion of the PAC from the internal jugular and subclavian vein insertion sites; indications, contraindications, and complications of PAC insertion; a comparison of less invasive hemodynamic monitors; reasons for decreased mixed or ScvO2; and indications and contraindications for transesophageal echocardiography. This review contains 12 highly rendered figures, 7 tables, and 95 references.

Effect of Balloon Inflation Volume on Pulmonary Artery Occlusion Pressure in Patients With and Without Pulmonary Hypertension

Pulmonary artery occlusion pressure (PAOP) is used to differentiate patients with pulmonary hypertension (PH) associated with left-sided heart disease from other etiologies. Technical errors in the measurement of PAOP are common and lead to incorrect classification of the etiology of PH. We investigated the agreement among PAOP measurements obtained from both pulmonary arteries with balloon full (1.5 mL) and half (0.75 mL) inflation in patients undergoing right-sided heart catheterization for suspected PH. Thirty-seven patients suspected or known to have PH who underwent right-sided heart catheterization were included. Seventy-six percent had PH (mean pulmonary arterial pressure > 25 mm Hg). The validity of the measurements was assessed by using five preestablished criteria based on hemodynamic, fluoroscopic, and gasometric data. For each patient, the measurement that most likely represented the left atrial pressure was labeled "best PAOP." Seventy percent of all the PAOP measurements met at least four of the five preestablished criteria for validity. In patients with PH (n = 28), the mean ± SE PAOP was 23.1 ± 2 and 19.1 ± 2 mm Hg for balloon full and half inflation, respectively, in the right pulmonary artery and 23.54 ± 2 and 19.07 ± 2 mm Hg for balloon full and half inflation, respectively, in the left pulmonary artery (P = .05). Bland-Altman analysis revealed lower bias and narrower limits of agreement with balloon half inflation. Wedge angiography showed that some balloon inflations failed to occlude upstream flow, whereas others had collateral vessels draining after the occlusion. PAOP can be falsely elevated in patients with PH according to the balloon inflation volume. Balloon half inflation was safe and correlated with higher precision and lower bias in the PAOP measurements.

Telemetric Catheter-Based Pressure Sensor for Hemodynamic Monitoring: Experimental Experience

The purpose of this study was to evaluate the technical and animal experimental feasibility of a percutaneously implantable pulmonary arterial implant for permanent hemodynamic monitoring. Two systems for measuring pulmonary artery pressure (PAP) as well as pulmonary artery occlusion pressure (PAOP) were developed by modifying a commercially available pulmonary artery catheter (PAC). First, a cable-bound catheter-based system was designed by implementation of a capacitive absolute-pressure sensor in the catheter tip. This system was developed further into a completely implantable telemetric system. The devices were tested in an acute setting in a total of 10 sheep. The implant was placed with its tip in the descending pulmonary artery via the right jugular approach. Results were compared with conventional PAC positioned in the contralateral pulmonary artery using Pearson's correlation coefficients and Bland-Altman plots. Implantation of the monitoring systems was uneventful in 10 animals. Data from two fully functional cable-bound and telemetric pressure monitoring systems were available, with a total of 18,506 measurements. There was an excellent correlation between reference data and the data obtained with the implants (r = 0.9944). Bland-Altman plots indicated a very good agreement between the techniques. We report the development and successful initial test of an implantable catheter-based device for long-term measurement of PAP and PAOP. Both devices may be applicable for hemodynamic monitoring. Further long-term studies for assessing reliability and durability of the device are warranted.

Pulmonary artery occlusion pressure estimation by transesophageal echocardiography: is simpler better?

The measurement of pulmonary artery occlusion pressure (PAOP) is important for estimation of left ventricular filling pressure and for distinction between cardiac and non-cardiac etiology of pulmonary edema. Clinical assessment of PAOP, which relies on physical signs of pulmonary congestion, is uncertain. Reliable PAOP measurement can be performed by pulmonary artery catheter, but it is possible also by the use of echocardiography. Several Doppler variables show acceptable correlation with PAOP and can be used for its estimation in cardiac and critically ill patients. Noninvasive PAOP estimation should probably become an integral part of transthoracic and transesophageal echocardiographic evaluation in critically ill patients. However, the limitations of both methods should be taken into consideration, and in specific patients invasive PAOP measurement is still unavoidable, if the exact value of PAOP is needed.

Systolic pressure variation: a dynamic measure of the adequacy of intravascular volume

Central venous pressure and pulmonary artery occlusion pressure measurements are complicated by ventilatory changes in intrathoracic pressure and have a poor record as a preload parameter. The hemodynamic changes of mechanical ventilation have the effect of withholding a volume of blood and then giving it back during each respiratory cycle. The inspiratory phase of mechanical ventilation reduces preload and increases afterload of the right heart, while the preload is increased and afterload is reduced. These changes are reversed during expiration. The systolic pressure variation (SPV) by mechanical ventilation is closely related to the intravascular volume according to Starling’s law. The effect of mechanical ventilation on the left ventricular stroke volume has given birth to dynamic monitors of preload obtained from the arterial side in the form of SPV and pulse pressure variation. Animal studies and numerous clinical studies in surgical and critically ill patients have shown the superiority of dynamic monitors over the venous and pulmonary artery occlusion pressures.

Are we any better at predicting pulmonary artery occlusion pressure?

The usefulness of pulmonary artery catheterization in the critically ill is questionable,1 but the measurement of haemodynamic variables permits a rational approach to management. The placement of pulmonary artery flotation catheters (PAFCs) is influenced by the perceived inability of the clinician to determine haemodynamic status from clinical evaluation alone.2 After 20 yr of experience in the use of the pulmonary artery catheter are we any better at predicting what we are measuring? Four intensive care units in the South East of Scotland participated over a 6-month period. Pulmonary artery occlusion pressure (PAOP) and cardiac index were estimated immediately before PAFC placement. This abstract is confined to the results of PAOP estimations and actual values. In advance of analysis a difference of ±3 mmHg was considered clinically insignificant. Actual values were divided into three bands: 16 mmHg. Data on 92 patients were suitable for analysis. Four patients were excluded due to incomplete information. The mean age was 61 yr. The PAFC was placed within 48 h of admission to the Intensive Care Unit in 87 patients. In 70 patients the placement of the PAFC was consultant directed. Sixty-one patients (66.3%) had a clinically insignificant difference between predicted and actual PAOP. Of the remaining 31 patients (33.6%), 11 patients were just out with the set criteria (4 mmHg difference) and this did not affect their management. Thirteen patients had estimations and actual measurements which were in different bands. Actual PAOP measurement revealed nine of these patients to be underfilled (six septic, three others). Two septic patients, estimated to be very underfilled, had elevated actual PAOP measurements (predicted PAOP 5 and 12 mmHg, actual PAOP 25 and 20 mmHg respectively). Prediction of pulmonary artery occlusion pressure is generally accurate, however clinical judgement may fail to diagnose significant underfilling in patients with sepsis. It is debatable whether PAOP accurately reflects volume status, but five of these patients had a measured PAOP of 4 mmHg or less, and only one of these patients was judged to be underfilled. Two patients who were shocked (meningococcal septicaemia and bowel obstruction) were judged to be underfilled, but both had a PAOP ≥20 mmHg. It is hard to believe that this did not represent undiagnosed myocardial dysfunction. PAFC placement remains a useful diagnostic and management tool in a small number of shocked septic patients.

Right heart catheterization in acute lung injury: an observational study.

Right heart catheterization (RHC) is commonly used in the diagnosis and management of acute lung injury (ALI). However, controversy exists regarding RHC. We examined RHC use during the first 3 d of ALI in an observational study of 135 patients defined by American-European Consensus Conference criteria. Study parameters examined for association with RHC included the Acute Physiology and Chronic Health Evaluation (APACHE) III score, lung injury score (LIS), and 20 additional epidemiologic, clinical, and laboratory parameters. RHC was performed in 70 patients (52%) within the first 3 d of ALI. RHC was positively associated (p < 0.05) with a diagnosis of sepsis, APACHE III score, blood urea nitrogen (BUN), creatinine, net fluid balance, and positive end-expiratory pressure. RHC was negatively associated (p < 0.05) with mean arterial pressure (Pa) and PaO2/FIO2. Logistic regression identified four predictors for RHC placement: sepsis, PaO2/FIO2, BUN, and Pa. Initial right atrial and pulmonary artery occlusion pressure measurements demonstrated a moderately strong correlation (r = 0.72). Use of RHC was associated with a change in one or more therapeutic interventions (intravascular fluids, vasopressors, diuretics) in 78% of patients. In summary, patients receiving RHC during the first 3 d of ALI were more severely ill than those who did not receive RHC, and RHC was associated with a change in therapy in most patients.

Early cardiorespiratory patterns in patients with major burns and pulmonary insufficiency

We examined the case records of 50 consecutive patients with major cutaneous burns who required early mechanical ventilation. In 22 patients full haemodynamic and respiratory data were available within 24 h of their injury. Unexpectedly the haemodynamic and oxygen transport patterns of survivors and non-survivors were essentially similar although pulmonary artery occlusion pressure measurements and estimations of net fluid input suggest that non-survivors were relatively underresuscitated compared with survivors. Both groups showed inadequate oxygen utilization in the early stages of their injury despite normal (or above normal) levels of oxygen delivery. Invasive monitoring could possibly help this subgroup of burns patients.

Invasive monitoring combined with two-dimensional echocardiographic study in septic shock

An investigation into the incidence and the clinical implication of discrepancies which may sometimes occur between invasive and non-invasive hemodynamic evaluation in septic patients. A prospective, consecutive comparison. Department of Intensive Care Medicine at a University Hospital. 32 patients undergoing therapy for an episode of septic shock. Conventional hemodynamic support (including volume expansion in all cases and inotropic support if necessary) required to obtain a stable hemodynamic status. Cardiac output (thermodilution method), cardiac pressures (right heart catheterization) and left ventricular (LV) volumes (two-dimensional echocardiography) were simultaneously recorded. A comparison was thus made between both procedures, particularly concerning preload evaluation and assessment of left ventricular systolic function. Pulmonary artery occlusion pressure measurement was evidence as an unreliable index of LV end-diastolic volume, determining preload. Assessment of LV systolic function by both methods was conflicting in 11 cases out of the 32. Frequent discrepancies between to invasive and non-invasive procedure were observed. The reasons for these discrepancies, including low vascular resistance, reduced LV compliance, and a possible overestimation of cardiac output by the thermodilution method, are examined in the light of data recorded. It was concluded that invasive hemodynamic evaluation by right heart catheterization in septic patients should be seriously questioned.

A bedside index assessing the reliability of pulmonary artery occlusion pressure measurements during mechanical ventilation with positive end-expiratory pressure

Pulmonary artery occlusion pressure (Ppao) represents the pressure in a pulmonary vein (Ppv) and reflects left atrial pressure (P la) provided alveolar pressure (Palv) does not exceed the pressure existing at the venous end of the collapsible alveolar vessels. Three major factors may influence the relationships between Palv and Ppv: mechanical ventilation with positive end-expiratory pressure (PEEP), vertical location of the pulmonary artery catheter (PAC) tip relative to the left atrium, and volemia. In an experimental and clinical study, we assessed a simple means to ensure meaningful measurements of Ppao during mechanical ventilation with PEEP, based on the following reasoning: if Ppao reflects Palv and not Ppv, it will increase during positive pressure inspiration by an amount (ΔPpao) similar to Palv; thus, ΔPpao will widely exceed the increase in pulmonary arterial pressure (ΔPpa), which approximates the increase in pleural pressure. Conversely, when Ppao actually reflects Ppv, ΔPpao will be close to ΔPpa. A preliminary experimental study in an animal with a left atrial catheter and PAC in place showed that Ppao widely exceeded P la when ΔPpao/ΔPpa widely exceeded 1 during mechanical ventilation with PEEP. After fluid infusion, P la and Ppao were almost identical and ΔPpao/ΔPpa was now close to 1. In 12 patients ventilated for adult respiratory distress syndrome and with a left ventricular catheter and PAC in place, we verified at four levels of PEEP (0, 10, 15, and 20 cm H 2O) that a Ppao close to left ventricular end-diastolic pressure was always associated with a ΔPpao/ΔPpa ratio close to 1 (38 measurements). In 34 additional patients ventilated for noncardiogenic pulmonary edema, we also tested the ΔPpao/ΔPpa ratio during the same incremental PEEP protocol and found that ΔPpao/ΔPpa was close to 1 at each level of PEEP in 30 of the patients (108 measurements). In five measurements in four hypovolemic patients, ΔPpao/ΔPpa widely exceeded 1; only one of these four patients was found to have a PAC tip located above the left atrium level on a lateral chest x-ray film. We conclude that the bedside determination of the ΔPpao/ΔPpa ratio should identify the cases in which Ppao measurements are not valid more reliably than lateral chest x-ray film, thus avoiding misleading interpretations of Ppao during PEEP ventilation.

Temporary Muscle Paralysis for Accurate Measurement of Pulmonary Artery Occlusion Pressure

Succinylcholine, a short-acting neuromuscular blocking agent, was used to accurately measure the pulmonary artery occlusion pressure (PAOP) in eight patients requiring mechanical ventilation for acute respiratory failure, in whom measurement was difficult because of significant respiratory variation in PAOP. The mean decrease in PAOP after paralysis was 9.8 +/- 5.3 mm Hg, with a range of 4 to 20 mm Hg (p less than 0.01). The magnitude of change was closely correlated to the degree of respiratory variation in PAOP observed during spontaneous breathing before paralysis (r = 0.889). Accurate measurement of PAOP affected subsequent management in five of these eight patients. Temporary muscle paralysis with succinylcholine is a useful means of eliminating artifactual elevations in PAOP in patients supported by mechanical ventilation when significant respiratory variation in PAOP is present.