Right Ventricular Pressure Waveform Analysis-Clinical Relevance and Future Directions.

Continuous measurement of pressure in the right atrium and pulmonary artery has commonly been used to monitor right ventricular function in critically ill and surgical patients. This approach is largely based upon the assumption that right atrial and pulmonary arterial pressures provide accurate surrogates for diastolic filling and peak right ventricular pressures, respectively. However, due to both technical and physiologic factors, this assumption is not always true. Accordingly, recent studies have begun to emphasize the potential clinical value of also measuring right ventricular pressure at the bedside. This has highlighted both past and emerging research demonstrating the utility of analyzing not only the amplitude of right ventricular pressure but also the shape of the pressure waveform. This brief review summarizes data demonstrating that combining conventional measurements of right ventricular pressure with variables derived from waveform shape allows for more comprehensive and ideally continuous bedside assessment of right ventricular function, particularly when combined with stroke volume measurement or 3D echocardiography, and discusses the potential use of right ventricular pressure analysis in computational models for evaluating cardiac function.

Stiffening of the human proximal pulmonary artery with increasing age.

Adverse effects of large artery stiffening are well established in the systemic circulation; stiffening of the proximal pulmonary artery (PPA) and its sequelae are poorly understood. We combined in vivo (n = 6) with ex vivo data from cadavers (n = 8) and organ donors (n = 13), ages 18 to 89, to assess whether aging of the PPA associates with changes in distensibility, biaxial wall strain, wall thickness, vessel diameter, and wall composition. Aging exhibited significant negative associations with distensibility and cyclic biaxial strain of the PPA (p ≤ 0.05), with decreasing circumferential and axial strains of 20% and 7%, respectively, for every 10 years after 50. Distensibility associated directly with diffusion capacity of the lung (R2 = 0.71, p = 0.03). Axial strain associated with right ventricular ejection fraction (R2 = 0.76, p = 0.02). Aging positively associated with length of the PPA (p = 0.004) and increased luminal caliber (p = 0.05) but showed no significant association with mean wall thickness (1.19 mm, p = 0.61) and no significant differences in the proportions of mural elastin and collagen (p = 0.19) between younger (<50 years) and older (>50) ex vivo samples. We conclude that age-related stiffening of the PPA differs from that of the aorta; microstructural remodeling, rather than changes in overall geometry, may explain age-related stiffening.

Management of Respiratory Failure in Hemorrhagic Shock.

Hemorrhagic shock results in acute respiratory failure due to respiratory muscle fatigue and inadequate pulmonary blood flow. Because positive pressure ventilation can reduce venous return and cardiac output, clinicians should use the minimum possible mean airway pressure during assisted or mechanical ventilation, particularly during episodes of severe hypovolemia. Hypoperfusion also worsens dead space fraction. Therefore, clinicians should monitor capnography during mechanical ventilation and recognize that hypercapnia may be treated with fluid resuscitation rather than increasing minute ventilation.

Pulmonary Hypertension and the Risk of 30-Day Postoperative Pulmonary Complications after Gastrointestinal Surgical or Endoscopic Procedures: A Retrospective Propensity Score-Weighted Cohort Analysis.

Background: Pulmonary hypertension (PH) patients are at higher risk of postoperative complications. We analyzed the association of PH with 30-day postoperative pulmonary complications (PPCs). Methods: A single-center propensity score overlap weighting (OW) retrospective cohort study was conducted on 164 patients with a mean pulmonary artery pressure (mPAP) of >20 mmHg within 24 months of undergoing elective inpatient abdominal surgery or endoscopic procedures under general anesthesia and a control cohort (N = 1981). The primary outcome was PPCs, and the secondary outcomes were PPC sub-composites, namely respiratory failure (RF), pneumonia (PNA), aspiration pneumonia/pneumonitis (ASP), pulmonary embolism (PE), length of stay (LOS), and 30-day mortality. Results: PPCs were higher in the PH cohort (29.9% vs. 11.2%, p < 0.001). When sub-composites were analyzed, higher rates of RF (19.3% vs. 6.6%, p < 0.001) and PNA (11.2% vs. 5.7%, p = 0.01) were observed. After OW, PH was still associated with greater PPCs (RR 1.66, 95% CI (1.05-2.71), p = 0.036) and increased LOS (median 8.0 days vs. 4.9 days) but not 30-day mortality. Sub-cohort analysis showed no difference in PPCs between pre- and post-capillary PH patients. Conclusions: After covariate balancing, PH was associated with a higher risk for PPCs and prolonged LOS. This elevated PPC risk should be considered during preoperative risk assessment.

Essential right heart physiology for the perioperative practitioner POQI IX: current perspectives on the right heart in the perioperative period.

As patients continue to live longer from diseases that predispose them to right ventricular (RV) dysfunction or failure, many more patients will require surgery for acute or chronic health issues. Because RV dysfunction results in significant perioperative morbidity if not adequately assessed or managed, understanding appropriate assessment and treatments is important in preventing subsequent morbidity and mortality in the perioperative period. In light of the epidemiology of right heart disease, a working knowledge of right heart anatomy and physiology and an understanding of the implications of right-sided heart function for perioperative care are essential for perioperative practitioners. However, a significant knowledge gap exists concerning this topic. This manuscript is one part of a collection of papers from the PeriOperative Quality Initiative (POQI) IX Conference focusing on "Current Perspectives on the Right Heart in the Perioperative Period." This review aims to provide perioperative clinicians with an essential understanding of right heart physiology by answering five key questions on this topic and providing an explanation of seven fundamental concepts concerning right heart physiology.

Differential cardiopulmonary haemodynamic phenotypes in PASC-related exercise intolerance.

Background: Post-acute sequelae of COVID-19 (PASC) affect a significant proportion of patients who have previously contracted SARS-CoV-2, with exertional intolerance being a prominent symptom. This study aimed to characterise the invasive haemodynamic abnormalities of PASC-related exertional intolerance using invasive cardiopulmonary exercise testing (iCPET). Study design and intervention: 55 patients were recruited from the Yale Post-COVID-19 Recovery Program, with most experiencing mild acute illness. Supine right heart catheterisation and iCPET were performed on all participants. Main results: The majority (75%) of PASC patients exhibited impaired peak systemic oxygen extraction (pEO2) during iCPET in conjunction with supranormal cardiac output (CO) (i.e., PASC alone group). On average, the PASC alone group exhibited a "normal" peak exercise capacity, V'O2 (89±18% predicted). ∼25% of patients had evidence of central cardiopulmonary pathology (i.e., 12 with resting and exercise heart failure with preserved ejection fraction (HFpEF) and two with exercise pulmonary hypertension (PH)). PASC patients with HFpEF (i.e., PASC HFpEF group) exhibited similarly impaired pEO2 with well compensated PH (i.e., peak V'O2 and CO >80% respectively) despite aberrant central cardiopulmonary exercise haemodynamics. PASC patients with HFpEF also exhibited increased body mass index of 39±7 kg·m-2. To examine the relative contribution of obesity to exertional impairment in PASC HFpEF, a control group comprising obese non-PASC group (n=61) derived from a historical iCPET cohort was used. The non-PASC obese patients with preserved peak V'O2 (>80% predicted) exhibited a normal peak pulmonary artery wedge pressure (17±14 versus 25±6 mmHg; p=0.03) with similar maximal voluntary ventilation (90±12 versus 86±10% predicted; p=0.53) compared to PASC HFpEF patients. Impaired pEO2 was not significantly different between PASC patients who underwent supervised rehabilitation and those who did not (p=0.19). Conclusions: This study highlights the importance of considering impaired pEO2 in PASC patients with persistent exertional intolerance unexplained by conventional investigative testing. Results of the current study also highlight the prevalence of a distinct high output HFpEF phenotype in PASC with a primary peripheral limitation to exercise.

Optimization of lung ventilation and perfusion in anesthetized horses using a ventilation mode with flow-limited expiration.

OBJECTIVE: To investigate the mechanisms underlying the improved arterial oxygenation described with flow-limited expiration (FLEX) ventilation in anesthetized horses. ANIMALS: 5 healthy adult research horses. METHODS: Horses underwent volume-controlled ventilation for 60 minutes (VCV1), followed by 60 minutes of FLEX, and 30 minutes of VCV (VCV2). Main outcomes included the arterial partial pressure of oxygen-to-Fio2 (PF) ratio and electrical impedance tomography (EIT)-derived functional indices at the end of each phase. The EIT data were used to create regional maps of relative lung ventilation and perfusion as well as regional maps of ventilation/perfusion (V/Q) ratios. Ventilation indices derived from EIT included the fraction of expired volume in 1 second (FEV1; %) and the time it took for the EIT signal to drop to 50% of the peak signal at end-inspiration (TClose50; seconds). Data were analyzed with 2-way ANOVA for repeated measures. P < .05 was considered significant. RESULTS: The PF ratio increased significantly with FLEX compared to both VCV1 and VCV2 (P < .01). There were no differences in the relative distribution of ventilation nor perfusion between ventilation strategies. However, when ventilation and perfusion were superimposed and V/Q ratio maps were constructed, FLEX had a homogenizing effect toward values of 1.0. The FEV1 was shorter (P < .01) and the TClose50 was longer (P < .001) in all regions during FLEX compared to both VCV1 and VCV2. CLINICAL RELEVANCE: Our findings suggest that FLEX ventilation in anesthetized horses enhances regional V/Q matching, likely by prolonging expiratory aeration and reducing airway closure.

Right Heart Failure in the Intensive Care Unit: Etiology, Pathogenesis, Diagnosis, and Treatment.

Right heart (RH) failure carries a high rate of morbidity and mortality. Patients who present with RH failure often exhibit complex aberrant cardio-pulmonary physiology with varying presentations. The treatment of RH failure almost always requires care and management from an intensivist. Treatment options for RH failure patients continue to evolve rapidly with multiple options available, including different pharmacotherapies and mechanical circulatory support devices that target various components of the RH circulatory system. An understanding of the normal RH circulatory physiology, treatment, and support options for the RH failure patients is necessary for all intensivists to improve outcomes. The purpose of this review is to provide clinical guidance on the diagnosis and management of RH failure within the intensive care unit setting, and to highlight the different pathophysiological manifestations of RH failure, its hemodynamics, and treatment options available at the disposal of the intensivist.

Continuous non-invasive hemodynamic monitoring in early onset severe preeclampsia.

OBJECTIVES: Continuous hemodynamic monitoring offers the opportunity to individualize management in severe preeclampsia (PEC). We compared cardiac output (CO) and total peripheral resistance (TPR) measured by bioreactance (NICOM), Clearsite™ Fingercuff [CS), and 3D-echocardiography (3DE). STUDY DESIGN: This prospective observational study included 12 pregnant patients with early PEC. CO and TPR were measured simultaneously by NICOM, CS, and 3DE antepartum and 1-2 days postpartum. Using 3DE as the standard, CS and NICOM interchangeability, precision, accuracy, and correlation were assessed. RESULTS: Compared to 3DE-CO, CS-CO was highly correlated (R2 = 0.70, p = <0.0001) with low percentage error (PE 29%) which met criteria for interchangeablity. CS-TPR had strong correlation (R2 = 0.81, p = <0.0001) and low PE (29%). While CS tended to slightly overestimate CO (bias + 2.05 ±1.18 L/min, limit of agreement (LOA) -0.20 to 4.31) and underestimate TPR (bias -279 ±156 dyes/sec/cm5; LOA -580 to 18.4) these differences were unlikely to be clinically significant. Thus CS could be interchangeable with 3DE for CO and TPR. NICOM-CO had only moderate correlation with 3DE-CO (R2 = 0.29, p = 0.01) with high PE (52%) above threshold for interchangeability. NICOM-CO had low mean bias (-1.2 ±1.68 L/min) but wide 95% LOA (-4.41 to 2.14) suggesting adequate accuracy but low precision in relation to 3DE-CO. NICOM-TPR had poor correlation with 3DE-TPR (R2 = 0.32, p = 0.001) with high PE (67%), relatively low mean bias (238 ±256), and wide 95% LOA (-655 to 1131). NICOM did not meet the criteria for interchangeable with 3DE for CO and TPR. CONCLUSIONS: Clearsite Fingercuff, but not NICOM, has potential to be clinically useful for CO and TPR monitoring in severe preeclampsia.

Integrating Right Ventricular Pressure Waveform Analysis With Two-Point Volume Measurement for Quantification of Systolic and Diastolic Function: Experimental Validation and Clinical Application.

OBJECTIVE: To define in an experimental model the variance, accuracy, precision, and concordance of single-beat measures of right ventricular (RV) contractility and diastolic capacitance relative to conventional reference standards, and apply the methods to a clinical data set. DESIGN: A retrospective, observational analysis of recorded pressure waveforms and RV volume measurements. SETTING: At a university laboratory. PARTICIPANTS: Archived data from previous studies of anesthetized swine and awake patients undergoing clinically-indicated right-heart catheterization. INTERVENTIONS: Recording of RV pressure with simultaneous measurement of RV volume by conductance (swine) or 3-dimensional (3D) echocardiography (humans) during changes in contractility and/or loading conditions. MEASUREMENTS AND MAIN RESULTS: Using experimental data, single-beat measures of RV contractility quantified as end-systolic elastance, and diastolic capacitance quantified as the predicted volume at an end-diastolic pressure of 15 mmHg (V15), were compared to multi-beat, preload- variant, reference standards using correlation, Bland-Altman analysis, and 4-quadrant concordance testing. This analysis indicated that the methods were not directly interchangeable with reference standards, but were sufficiently robust to suggest potential clinical utility. Clinical application supported this potential by demonstrating enhanced assessment of the response to inhaled nitric oxide in patients undergoing diagnostic right-heart catheterization. CONCLUSIONS: Study results supported the possibility of integrating automated RV pressure analysis with RV volume measured by 3D echocardiography to create a comprehensive assessment of RV systolic and diastolic function at the bedside.