Bedside evaluation of the resistance of large and medium pulmonary veins in various lung diseases

Estimation of Pulmonary Artery Occlusion Pressure Using Doppler Echocardiography in Mechanically Ventilated Patients

OBJECTIVES

Evaluation of left atrial pressure is frequently required for mechanically ventilated critically ill patients. The objective of the present study was to evaluate the 2016 American Society of Echocardiography and the European Association of Cardiovascular Imaging guidelines for assessment of the pulmonary artery occlusion pressure (a frequent surrogate of left atrial pressure) in this population.

DESIGN

A pooled analysis of three prospective cohorts of patients simultaneously assessed with a pulmonary artery catheter and echocardiography.

SETTINGS

Medical-surgical intensive care department of two university hospitals in France.

PATIENTS

Mechanically ventilated critically ill patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 98 included patients (males: 67%; mean ± SD age: 59 ± 16; and mean Simplified Acute Physiology Score 2: 54 ± 20), 53 (54%) experienced septic shock. Using the 2016 American Society of Echocardiography and the European Association of Cardiovascular Imaging guidelines, the predicted pulmonary artery occlusion pressure was indeterminate in 48 of the 98 patients (49%). Of the 24 patients with an elevated predicted left atrial pressure (grade II/III diastolic dysfunction), only 17 (71%) had a pulmonary artery occlusion pressure greater than or equal to 18 mm Hg. Similarly, 20 of the 26 patients (77%) with a normal predicted left atrial pressure (grade I diastolic dysfunction) had a measured pulmonary artery occlusion pressure less than 18 mm Hg. The sensitivity and specificity of American Society of Echocardiography and the European Association of Cardiovascular Imaging guidelines for predicting elevated pulmonary artery occlusion pressure were both 74%. The agreement between echocardiography and the pulmonary artery catheter was moderate (Cohen's Kappa, 0.48; 95% CI, 0.39-0.70). In a proposed alternative algorithm, the best echocardiographic predictors of a normal pulmonary artery occlusion pressure were a lateral e'-wave greater than 8 (for a left ventricular ejection fraction ≥ 45%) or an E/A ratio less than or equal to 1.5 (for a left ventricular ejection fraction < 45%).

CONCLUSIONS

The American Society of Echocardiography and the European Association of Cardiovascular Imaging guidelines do not accurately assess pulmonary artery occlusion pressure in ventilated critically ill patients. Simple Doppler measurements gave a similar level of diagnostic performance with less uncertainly.

Prevalence of pulmonary hypertension in adults after atrial switch and role of ventricular filling pressures

OBJECTIVE

To assess the prevalence of elevated systemic right ventricular (sRV) end-diastolic pressure and pulmonary arterial hypertension in adults with transposition of the great arteries (TGA) who have undergone atrial switch operation.

METHODS

Forty-two adults (aged ≥18 years) with complete TGA and atrial switch palliation undergoing cardiac catheterisation between 2004 and 2018 at Mayo Clinic, MN, were identified. Clinical, echocardiographic and invasive haemodynamic data were abstracted from the medical charts and procedure logs.

RESULTS

Mean age was 37.6±7.9 years; 28 were male (67%). The Mustard operation was performed in 91% of individuals. Mean estimated sRV ejection fraction by echocardiography was 33.3%±10.9% and ≥moderate tricuspid (systemic atrioventricular valve) regurgitation was present in 15 patients (36%). Mean sRV end-diastolic pressure was 13.2±5.4 mm Hg. An sRV end-diastolic pressure >15 mm Hg was present in 35% of individuals whereas a pulmonary artery wedge pressure (PAWP) >15 mm Hg was seen in 59%. Mean pulmonary artery pressure ≥25 mm Hg was seen in 47.5% of patients with PAWP being >15 mm Hg in all but one patient.

CONCLUSION

In adults after atrial switch, elevated sRV end-diastolic pressure was present in only one-third of patients whereas increased PAWP was seen in almost 60%. These findings are most likely related to a combination of decreased pulmonary atrial (functional left atrium) compliance and, in a subset of patients, pulmonary venous baffle obstruction. Elevation in pulmonary pressures was highly prevalent with concomitant elevation in PAWP being present in essentially all patients.

Heart-lung interactions during neurally adjusted ventilatory assist

Introduction

Assist in unison to the patient’s inspiratory neural effort and feedback-controlled limitation of lung distension with neurally adjusted ventilatory assist (NAVA) may reduce the negative effects of mechanical ventilation on right ventricular function.

Methods

Heart–lung interaction was evaluated in 10 intubated patients with impaired cardiac function using esophageal balloons, pulmonary artery catheters and echocardiography. Adequate NAVA level identified by a titration procedure to breathing pattern (NAVAal), 50% NAVAal, and 200% NAVAal and adequate pressure support (PSVal, defined clinically), 50% PSVal, and 150% PSVal were implemented at constant positive end-expiratory pressure for 20 minutes each.

Results

NAVAal was 3.1 ± 1.1cmH₂O/μV and PSVal was 17 ± 2 cmH₂0. For all NAVA levels negative esophageal pressure deflections were observed during inspiration whereas this pattern was reversed during PSVal and PSVhigh. As compared to expiration, inspiratory right ventricular outflow tract velocity time integral (surrogating stroke volume) was 103 ± 4%, 109 ± 5%, and 100 ± 4% for NAVAlow, NAVAal, and NAVAhigh and 101 ± 3%, 89 ± 6%, and 83 ± 9% for PSVlow, PSVal, and PSVhigh, respectively (p < 0.001 level-mode interaction, ANOVA). Right ventricular systolic isovolumetric pressure increased from 11.0 ± 4.6 mmHg at PSVlow to 14.0 ± 4.6 mmHg at PSVhigh but remained unchanged (11.5 ± 4.7 mmHg (NAVAlow) and 10.8 ± 4.2 mmHg (NAVAhigh), level-mode interaction p = 0.005). Both indicate progressive right ventricular outflow impedance with increasing pressure support ventilation (PSV), but no change with increasing NAVA level.

Conclusions

Right ventricular performance is less impaired during NAVA compared to PSV as used in this study. Proposed mechanisms are preservation of cyclic intrathoracic pressure changes characteristic of spontaneous breathing and limitation of right-ventricular outflow impedance during inspiration, regardless of the NAVA level.

Trial registration

Clinicaltrials.gov Identifier: NCT00647361, registered 19 March 2008

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0499-8) contains supplementary material, which is available to authorized users.

Pulmonary artery catheter monitoring in 2011

PURPOSE OF REVIEW

Hemodynamic monitoring has gained widespread acceptance in intensive care units. Despite ongoing debate regarding its safety and efficacy, monitoring with the pulmonary artery catheter (PAC) remains used for the management of severe heart failure and shock.

RECENT FINDINGS

To reanalyze using the most recently published literature in the field, the role of the PAC to manage critically ill patients with right ventricular failure, pulmonary hypertension and weaning failure from cardiac origin. The role of PAC as a gold standard to validate new cardiac output monitoring devices was also reported.

SUMMARY

Despite competition with less invasive hemodynamic monitoring devices or ultrasonic methods, the PAC remains a useful monitoring device in situations in which the knowledge of pulmonary artery pressure, pulmonary artery occlusion pressure and oxygenation parameters are needed. The proper use of PAC requires, however, a perfect knowledge of the numerous pitfalls and difficulties in interpretation of its measurements.

Fluid management in acute lung injury and ards

ARDS is particularly characterized by pulmonary edema caused by an increase in pulmonary capillary permeability. It is considered that limiting pulmonary edema or accelerating its resorption through the modulation of fluid intake or oncotic pressure could be beneficial. This review discusses the principal clinical studies that have made it possible to progress in the optimization of the fluid state during ARDS. Notably, a randomized, multicenter study has suggested that fluid management with the goal to obtain zero fluid balance in ARDS patients without shock or renal failure significantly increases the number of days without mechanical ventilation. On the other hand, it is accepted that patients with hemodynamic failure must undergo early and adapted vascular filling. Liberal and conservative filling strategies are therefore complementary and should ideally follow each other in time in the same patient whose hemodynamic state progressively stabilizes. At present, although albumin treatment has been suggested to improve oxygenation transiently in ARDS patients, no sufficient evidence justifies its use to mitigate pulmonary edema and reduce respiratory morbidity. Finally, the resorption of alveolar edema occurs through an active mechanism, which can be pharmacologically upregluated. In this sense, the use of beta-2 agonists may be beneficial but further studies are needed to confirm preliminary promising results.

Assessing pulmonary permeability by transpulmonary thermodilution allows differentiation of hydrostatic pulmonary edema from ALI/ARDS

OBJECTIVE

To test whether assessing pulmonary permeability by transpulmonary thermodilution enables to differentiate increased permeability pulmonary edema (ALI/ARDS) from hydrostatic pulmonary edema.

DESIGN

Retrospective review of cases.

SETTING

A 24-bed medical intensive care unit of a university hospital.

PATIENTS

Forty-eight critically ill patients ventilated for acute respiratory failure with bilateral infiltrates on chest radiograph, a PaO(2)/FiO(2) ratio < 300 mmHg and extravascular lung water indexed for body weight >/= 12 ml/kg.

INTERVENTION

We assessed pulmonary permeability by two indexes obtained from transpulmonary thermodilution: extravascular lung water/pulmonary blood volume (PVPI) and the ratio of extravascular lung water index over global end-diastolic volume index. The cause of pulmonary edema was determined a posteriori by three experts, taking into account medical history, clinical features, echocardiographic left ventricular function, chest radiography findings, B-type natriuretic peptide serum concentration and the time-course of these findings with therapy. Experts were blind for pulmonary permeability indexes and for global end-diastolic volume.

MEASUREMENTS AND RESULTS

ALI/ARDS was diagnosed in 36 cases. The PVPI was 4.7+/-1.8 and 2.1+/-0.5 in patients with ALI/ARDS and hydrostatic pulmonary edema, respectively (p<0.05). The extravascular lung water index/global end-diastolic volume index ratio was 3.0 x 10(-2)+/-1.2 x 10(-2) and 1.4 x 10(-2)+/-0.4 x 10(-2) in patients with ALI/ARDS and with hydrostatic pulmonary edema, respectively (p<0.05). A PVPI >/= 3 and an extravascular lung water index/global end-diastolic index ratio >/= 1.8 x 10(-2) allowed the diagnosis of ALI/ARDS with a sensitivity of 85% and specificity of 100%.

CONCLUSION

These results suggest that indexes of pulmonary permeability provided by transpulmonary thermodilution may be useful for determining the mechanism of pulmonary edema in the critically ill.

Effects of levosimendan on right ventricular afterload in patients with acute respiratory distress syndrome: a pilot study

OBJECTIVE

Acute respiratory distress syndrome (ARDS) is frequently associated with increased pulmonary vascular resistance and thus with systolic load of the right ventricle. We hypothesized that levosimendan, a new calcium sensitizer with potential pulmonary vasodilator properties, improves hemodynamics by unloading the right ventricle in patients with ARDS.

DESIGN

Prospective, randomized, placebo-controlled, pilot study.

SETTING

Twenty-two-bed multidisciplinary intensive care unit of a university hospital.

PATIENTS

Thirty-five patients with ARDS in association with septic shock.

INTERVENTIONS

Patients were randomly allocated to receive a 24-hr infusion of either levosimendan 0.2 microg/kg/min (n = 18) or placebo (n = 17). Data from right heart catheterization, cardiac magnetic resonance, arterial and mixed venous oxygen tensions and saturations, and carbon dioxide tensions were obtained before and 24 hrs after drug infusion.

MEASUREMENTS AND MAIN RESULTS

At a mean arterial pressure between 70 and 80 mm Hg (sustained with norepinephrine infusion), levosimendan increased cardiac index (from 3.8 +/- 1.1 to 4.2 +/- 1.0 L/min/m) and decreased mean pulmonary artery pressure (from 29 +/- 3 to 25 +/- 3 mm Hg) and pulmonary vascular resistance index (from 290 +/- 77 to 213 +/- 50 dynes/s/cm(5)/m(2); each p < .05). Levosimendan also decreased right ventricular end-systolic volume and increased right ventricular ejection fraction (p < .05). In addition, levosimendan increased mixed venous oxygen saturation (from 63 +/- 8 to 70 +/- 8%; p < .01).

CONCLUSIONS

This study provides evidence that levosimendan improves right ventricular performance through pulmonary vasodilator effects in septic patients with ARDS. A large multiple-center trial is needed to investigate whether levosimendan is able to improve the overall prognosis of patients with sepsis and ARDS.

Left atrial pressure can be accurately transmitted to the pulmonary artery despite zone 1 conditions

Pulmonary arterial occlusion pressure is not thought to reflect left atrial pressure (Pla) when alveolar pressure (PA) exceeds pulmonary venous pressure because alveolar capillaries collapse and the required continuous fluid column between the pulmonary artery and left atrium is interrupted. However, arterial-to-venous flow can occur when PA exceeds both the pulmonary arterial pressure (Ppa) and pulmonary venous pressure (i.e., in Zone 1 conditions), indicating the existence of a continuous patent vascular channel. Accordingly, Ppa should reflect Pla under these conditions. To investigate this connection cannulas were placed in the pulmonary arteries and left atria of eight excised rabbit lungs. Ppa and Pla were set 5 cm H2O above PA, which ranged from 0 to 25 cm H2O. Pla was then reduced in 2 to 4 cm H2O decrements while recording Ppa when arterial-to-venous flow ceased. At all PAs greater than 0 cm H2O, Pla was accurately reflected by the Ppa when both were exceeded by PA. The greater the PA, the lower the Ppa could track Pla below PA. Pla can be accurately measured by a pulmonary arterial catheter under Zone 1 conditions.

Overestimation of pulmonary artery occlusion pressure in pulmonary hypertension due to partial occlusion

OBJECTIVE

To evaluate partial occlusion in patients with pulmonary hypertension with regard to a) the degree to which it leads to overestimation of pulmonary artery occlusion pressure (Ppao) and b) identification of factors that could enhance its recognition.

DESIGN

Observational descriptive study.

SETTING

Medical intensive care unit.

PATIENTS

Fourteen patients with pulmonary hypertension and an increased pulmonary artery diastolic pressure (Ppad) - Ppao gradient (> or = 10 mm Hg).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The Ppao was recorded during partial occlusion (partial Ppao) and after catheter repositioning to obtain a lower, more accurate value (best Ppao). The error due to partial occlusion, defined as the difference between the partial Ppao and the best Ppao, was 13 +/- 5 mm Hg (range, 6-21 mm Hg). The previously widened Ppad - Ppao gradient invariably narrowed during partial occlusion and then increased by 13 +/- 5 mm Hg (range, 5-23) during the best Ppao measurement. There was a moderate correlation between the error due to partial occlusion (partial Ppao - best Ppao) and both the mean pulmonary artery pressure (r =.77, <.01) and the Ppad - Ppao gradient (r =.79, <.01).

CONCLUSIONS

Partial occlusion in patients with pulmonary hypertension may lead to significant overestimation of the Ppao and should be suspected when there is a substantial increase in the Ppao without a concomitant increase in the Ppad, as reflected by a marked narrowing of a previously widened Ppad - Ppao gradient.

Effects of catecholamines on the pulmonary venous bed in sheep

OBJECTIVE

To assess the effects of various catecholaminergic agents on pulmonary venous tone.

DESIGN

Prospective, randomized, controlled, experimental study.

SETTING

Physiology laboratory of a university hospital.

SUBJECTS

Thirty anesthetized, mechanically ventilated adult sheep.

INTERVENTIONS

Four groups of six animals received 1-hr infusions of norepinephrine (0.5 microg/kg/min), epinephrine (0.5 microg/kg/ min), dopamine (10 microg/kg/min), or dobutamine (10 microg/kg/min).

MEASUREMENTS AND MAIN RESULTS

A 7-Fr pulmonary artery catheter was placed in a proximal location to measure cardiac output and pressure in a large pulmonary vein (Ppw) after balloon inflation. Another catheter wedged in a small pulmonary artery measured pressure in a small pulmonary vein (Pdw). A third catheter measured left atrial pressure (PLA ). This method was able to detect the pulmonary venoconstrictive effects of histamine in a separate group of six animals. Pdw-PLA increased from a mean of 2.0+/-1.7 to 3.0+/-1.5 (SD) cm H2O (p < .01), 2.3+/-1.6 to 4.4+/-1.3 cm H2O (p < .01), and 1.7+/-1.0 to 3.5+/-2.2 cm H2O (p < .05) with norepinephrine, epinephrine, and dopamine, respectively. All of these drugs increased Pdw-Ppw, but only norepinephrine and epinephrine increased Ppw-PLA . No change in either pressure difference was observed with dobutamine. Elevation of cardiac output alone could not account for these findings since the increase in cardiac output induced by fluid infusion did not change the pressure differences.

CONCLUSION

Norepinephrine, epinephrine, and dopamine at doses commonly used in humans increase pulmonary venous tone in sheep.

Right ventricular function during weaning from mechanical ventilation after coronary artery bypass grafting: effect of volume loading

OBJECTIVE

The study was designed to investigate the right ventricular (RV) reaction to weaning from mechanical ventilation (MV) in patients with and without volume loading after coronary artery bypass grafting (CABG).

DESIGN

Controlled study.

SETTING

Surgical intensive care unit in a university hospital.

PATIENTS

18 patients were randomized in two groups, Control group (n = 9) and Volume group (n = 9), when the established criteria for weaning from the respirator were satisfied.

INTERVENTION

During MV, patients in the Volume group received in rapid (10-min) 6 ml/kg infusion of a 6% hydroxyethyl starch preparation.

MEASUREMENTS AND RESULTS

Hemodynamic parameters were measured using a combined right ventricular (RV) ejection fraction-oximetry pulmonary artery catheter at T0 (during MV: baseline), T1 (during MV: 10 min after volume loading or at the same time in the Control group), T2 [after 20 min of spontaneous ventilation (SV)]. In the Control group, RV volumes did not differ throughout the study, while cardiac index (CI) and RV stroke work index (RVSWI) increased from T1 to T2. In the Volume group, RV volumes increased from T0 to T1, further increasing from T1 to T2, whereas CI increased only from T0 to T1. In this group, RVSWI increased from T0 to T1 in 8/9 patients and from T1 to T2 in 6/9 patients.

CONCLUSIONS

An increase in RV volumes with a concomitant increase in RVSWI was observed in high preload patients when going from MV to SV, suggesting a preserved RV function during weaning from MV in this group compared with control patients. The depression in RV contractility observed in some patients suggested that rapid volume expansion before weaning from MV in CABG patients must be done carefully.

Positive end-expiratory pressure increases pulmonary venous vascular resistance in patients after coronary artery surgery

OBJECTIVE

To investigate the effect of positive and-expiratory pressure (PEEP) on the longitudinal distribution of pulmonary vascular resistance in patients immediately after coronary artery bypass grafting.

DESIGN

Prospective, intervention study.

SETTING

Postcardiac surgery intensive care unit in a teaching institution.

PATIENTS

Twenty patients after elective coronary artery bypass grafting.

INTERVENTION

The effect of PEEP on pulmonary circulation, at four different levels (0, 5, 10, and 15 cm H2O), was analyzed in 20 patients.

MEASUREMENTS AND MAIN RESULTS

Mean pulmonary arterial pressure, left atrial pressure, pulmonary artery occlusion pressure, and pulmonary capillary pressure were measured at each PEEP level. A model consisting of two resistances in series was used to analyze the effect of PEEP on the pulmonary circulation. The pulmonary vascular resistance for each area (arterial and venous) of the circulation was calculated. Pulmonary vascular resistance increased from 216 +/- 70 dyne.sec/cm5 at a PEEP of 0 cm H2O to 308 +/- 125 dyne.sec/cm5 at a PEEP of 15 cm H2O (p < .001). This increase, however, resulted solely from an increase in the resistance of the venous part of the pulmonary circulation from 66 +/- 29 to 134 +/- 69 dyne.sec/cm5 (p < .001), without any change in pulmonary arterial resistance.

CONCLUSIONS

PEEP increases pulmonary vascular resistance solely by increasing pulmonary venous resistance. When applying PEEP, changes in pulmonary vascular resistance may impede the resorption of pulmonary edema fluid.