Prognostic Value of Pulmonary Artery Oxygen Saturation in Pulmonary Embolism Requiring Endovascular Intervention.

This retrospective study evaluates the prognostic value of pulmonary artery oxygen saturation (PA O2) among patients who undergo mechanical intervention for pulmonary embolism (PE). Patients who died within 90 days had less PA O2, and a greater percentage of patients with a PA O2 of <50 died within 90 days of intervention. Regression analysis revealed an association of PA O2 with mortality that held true despite accounting for Pulmonary Embolism Severity Index (PESI) score and type of endovascular intervention. Receiver operator curve testing revealed PA O2 <50% to be inferior to PESI score but superior to Bova score in predicting mortality after mechanical PE intervention, with the combination of PA O2 <50% and PESI outperforming PESI and PA O2 in predicting mortality. Our pilot evaluation suggests preintervention PA O2 <50% to be associated with increased risk of all-cause mortality and may help identify patients at greatest risk of deterioration.

Temporary diaphragm pacing for patients at risk of prolonged mechanical ventilation after extensive aortic repair.

Objective: Prolonged mechanical ventilation (MV) after extensive aortic reconstructive surgery is common. Studies have demonstrated that diaphragm pacing (DP) improves lung function in patients with unilateral diaphragm paralysis. The goal of this study is to determine whether this technology can be applied to complex aortic repair to reduce prolonged MV and other respiratory sequelae. Methods: A retrospective review was performed of patients who underwent temporary DP after extensive aortic reconstructive surgery between 2019 and 2022. The primary end point was prolonged MV incidence. Other measured end points included diaphragm electromyography improvement, length of hospitalization, duration of intensive care unit stay, and reintubation rates. Results: Fourteen patients deemed at high risk of prolonged MV based on their smoking and respiratory history underwent DP after extensive aortic repair. The mean age was 70.2 years. The indications for aortic repair were a thoracoabdominal aortic aneurysm (n = 8, including 2 ruptured, 2 symptomatic, and 1 mycotic), a perivisceral aneurysm (n = 4), and a perivisceral coral reef aorta (n = 2). All patients had a significant smoking history (active or former) or other risk factors for ventilator-induced diaphragmatic dysfunction and prolonged MV. The mean total duration of MV postoperatively was 31.9 hours (range, 8.1-76.5 hours). The total average pacing duration was 4.4 days. Two patients required prolonged MV, with an average of 75.4 hours. Two patients required reintubation. No complications related to DP wire placement or removal occurred. Conclusions: DP is safe and feasible for patients at high risk of pulmonary insufficiency after extensive aortic reconstructive surgery.

The heart of the matter: Right heart imaging indicators for treatment escalation in pulmonary arterial hypertension.

Right heart (RH) structure and function are major determinants of symptoms and prognosis in pulmonary arterial hypertension (PAH). RH imaging provides detailed information, but evidence and guidelines on the use of RH imaging in treatment decisions are limited. We conducted a Delphi study to gather expert opinion on the role of RH imaging in decision-making for treatment escalation in PAH. A panel of 17 physicians with expertise in PAH and RH imaging used three surveys in a modified Delphi process to reach consensus on the role of RH imaging in PAH. Survey 1 used open-ended questions to gather information. Survey 2 contained Likert scale and other questions intended to identify consensus on topics identified in Survey 1. Survey 3 contained Likert scale questions derived from Survey 2 and summary information on the results of Survey 2. The Delphi panel reached consensus that RH imaging is likely to improve the current risk stratification algorithms and help differentiate risk levels in patients at intermediate risk. Tricuspid annular plane systolic excursion, right ventricular fractional area change, right atrial area, tricuspid regurgitation, inferior venae cavae diameter, and pericardial effusion should be part of routine echocardiography in PAH. Cardiac magnetic resonance imaging is valuable but limited by cost and access. A pattern of abnormal RH imaging results should prompt consideration of hemodynamic evaluation and possible treatment escalation. RH imaging is an important tool for decisions about treatment escalation in PAH, but systematically collected evidence is needed to clarify its role.

Control of tissue oxygenation by S-nitrosohemoglobin in human subjects.

S-Nitrosohemoglobin (SNO-Hb) is unique among vasodilators in coupling blood flow to tissue oxygen requirements, thus fulfilling an essential function of the microcirculation. However, this essential physiology has not been tested clinically. Reactive hyperemia following limb ischemia/occlusion is a standard clinical test of microcirculatory function, which has been ascribed to endothelial nitric oxide (NO). However, endothelial NO does not control blood flow governing tissue oxygenation, presenting a major quandary. Here we show in mice and humans that reactive hyperemic responses (i.e., reoxygenation rates following brief ischemia/occlusion) are in fact dependent on SNO-Hb. First, mice deficient in SNO-Hb (i.e., carrying C93A mutant Hb refractory to S-nitrosylation) showed blunted muscle reoxygenation rates and persistent limb ischemia during reactive hyperemia testing. Second, in a diverse group of humans-including healthy subjects and patients with various microcirculatory disorders-strong correlations were found between limb reoxygenation rates following occlusion and both arterial SNO-Hb levels (n = 25; P = 0.042) and SNO-Hb/total HbNO ratios (n = 25; P = 0.009). Secondary analyses showed that patients with peripheral artery disease had significantly reduced SNO-Hb levels and blunted limb reoxygenation rates compared with healthy controls (n = 8 to 11/group; P < 0.05). Low SNO-Hb levels were also observed in sickle cell disease, where occlusive hyperemic testing was deemed contraindicated. Altogether, our findings provide both genetic and clinical support for the role of red blood cells in a standard test of microvascular function. Our results also suggest that SNO-Hb is a biomarker and mediator of blood flow governing tissue oxygenation. Thus, increases in SNO-Hb may improve tissue oxygenation in patients with microcirculatory disorders.

Membrane bending and sphingomyelinase-associated, sulfatide-dependent hypoxic adhesion of sickle mature erythrocytes.

Abnormal erythrocyte adhesion owing to polymerization of sickle hemoglobin is central to the pathophysiology of sickle cell disease (SCD). Mature erythrocytes constitute >80% of all erythrocytes in SCD; however, the relative contributions of erythrocytes to acute and chronic vasculopathy in SCD are not well understood. Here, we showed that bending stress exerted on the erythrocyte plasma membrane by polymerization of sickle hemoglobin under hypoxia, enhances sulfatide-mediated abnormal mature erythrocyte adhesion. We hypothesized that sphingomyelinase (SMase) activity, which is upregulated by accumulated bending energy, leads to elevated membrane sulfatide availability, and thus, hypoxic mature erythrocyte adhesion. We found that mature erythrocyte adhesion to laminin in controlled microfluidic experiments is significantly greater under hypoxia than under normoxia (1856 ± 481 vs 78 ± 23, mean ± SEM), whereas sickle reticulocyte (early erythrocyte) adhesion, high to begin with, does not change (1281 ± 299 vs 1258 ± 328, mean ± SEM). We showed that greater mean accumulated bending energy of adhered mature erythrocytes was associated with higher acid SMase activity and increased mature erythrocyte adhesion (P = .022, for acid SMase activity and P = .002 for the increase in mature erythrocyte adhesion with hypoxia, N = 5). In addition, hypoxia results in sulfatide exposure of the erythrocyte membrane, and an increase in SMase, whereas anti-sulfatide inhibits enhanced adhesion of erythrocytes. These results suggest that the lipid components of the plasma membrane contribute to SCD complications. Therefore, sulfatide and the components of its upregulation pathway, particularly SMase, should be further explored as potential therapeutic targets for inhibiting sickle erythrocyte adhesion.

"Digital Tomosynthesis" As a Technique for the Evaluation of Endobronchial Stents in Lung Transplant Recipients.

Lung transplant patients often suffer from posttransplant airway pathologies that require placement of endobronchial stents. In addition to surveillance bronchoscopy, patients often undergo radiographic stent evaluations. Chest x-rays are extremely limited in their ability to diagnose stent complications, so many patients require chest computed tomography (CT) scans for stent evaluation. Chest CT scans are costly and expose patients to higher cumulative radiation doses. Digital tomosynthesis (DTS) is an imaging modality that provides high-resolution images using limited angle tomography. The costs and radiation doses are comparable to conventional x-ray. We present a series of 4 postlung transplant patients with bronchial stents in whom we performed DTS and chest x-ray simultaneously. The DTS images were far superior to chest x-ray and comparable with CT in evaluating the placement and patency of the stents, especially in the case of silicone stents. Furthermore, the improved resolution provided clinically relevant diagnostic information that resulted in therapeutic bronchoscopy for suctioning of mucus impaction in one of the patients.

Percutaneous mechanical thrombectomy and extracorporeal membranous oxygenation: A case series.

BACKGROUND: Massive or high-risk pulmonary embolism (PE) is a potentially life-threatening diagnosis with significant morbidity and mortality if treatment is delayed. Extracorporeal membrane oxygenation (ECMO) and large bore thrombectomy (LBT) in isolation have been used to stabilize and treat patients with massive PE, however, literature describing the combination of both modalities is lacking. We present a case series involving 9 patients who underwent combined ECMO and LBT and their outcomes. METHODS: This was a retrospective chart review of patients with confirmed PE, who underwent LBT and ECMO. We retrospectively captured clinical, therapeutic, and outcome data at the time of pulmonary embolism response team (PERT) activation and during the follow-up period for up to 90 days. RESULTS: Nine patients who had PERT activation with confirmed PE diagnosis have undergone combined LBT and ECMO initiation since the advent of our PERT program. The median age was 57 (range 28-68) years. Six patients out of 9 (55%) had cardiac arrest before therapy. All patients exhibited right heart strain on computed tomography and echocardiogram. The median ECMO duration was 5 days (range 2.3-11.6 days), with mean hospitalization of 16.1 days (range 1.5-30.9). Mortality was 22% at 90-day follow-up period. CONCLUSION: Patients with massive pulmonary embolism who suffer cardiac arrest have significant morbidity and mortality. ECMO in combination with LBT is a viable treatment option for patients with significant hemodynamic compromise.

Expiratory Peak Flow and Minute Ventilation Are Significantly Increased at High Altitude versus Simulated Altitude in Normobaria.

Simulated altitude (normobaric hypoxia, NH) is used to study physiologic hypoxia responses of altitude. However, several publications show differences in physiological responses between NH and hypobaric conditions at altitude (hypobaric hypoxia, HH). The causality for these differences is controversially discussed. One theory is that the lower air density and environmental pressure in HH compared to NH lead to lower alveolar pressure and therefore lower oxygen diffusion in the lung. We hypothesized that, if this theory is correct, due to physical laws (Hagen-Poiseuille, Boyle), resistance respectively air compression (Boyle) at expiration should be lower, expiratory flow higher, and therefore peak flow and maximum expiratory flow (MEF) 75-50 increased in hypobaric hypoxia (HH) vs. normobaric hypoxia (NH). To prove the hypothesis of differences in respiratory flow as a result of lower alveolar pressure between HH and NH, we performed spirography in NH at different simulated altitudes and the corresponding altitudes in HH. In a cross over study, 6 healthy subjects (2 f/4 m, 28.3 ± 8.2 years, BMI: 23.2 ± 1.9) performed spirography as part of spiroergometry in a normobaric hypoxic room at a simulated altitude of 2800 m and after a seven-hour hike on a treadmill (average incline 14%, average walking speed 1.6 km/h) to the simulated summit of Mauna Kea at 4200 m. After a two-month washout, we repeated the spirometry in HH on the start and top of the Mauna Kea hiking trail, HI/USA. Comparison of NH (simulated 4200 m) and HH at 4200 m resulted in increased pulmonary ventilation during exercise (VE) (11.5%, p < 0.01), breathing-frequency (7.8%, p < 0.01), peak expiratory flow PEF (13.4%, p = 0.028), and MEF50 (15.9%, p = 0.028) in HH compared to NH, whereas VO2max decreased by 2%. At 2800 m, differences were only trendy, and at no altitude were differences in volume parameters. Spirography expresses higher mid expiratory flows and peak flows in HH vs. NH. This supports the theory of lower alveolar and small airway pressure due to a lower air density resulting in a lower resistance.

Predictors and potential advantages of PERT and advanced therapy use in acute pulmonary embolism.

OBJECTIVES: We sought to examine predictors of pulmonary embolism response team (PERT) utilization and identify those who could benefit from advanced therapy. BACKGROUND: PERT and advanced therapy use remain low. Current risk stratification tools heavily weight age and comorbidities, which may not always correlate with presentation's severity. METHODS: We prospectively studied patients with CT-confirmed PE between January 2019 and December 2019 at our hospital. PERT activation was left to the treating physician. Multivariable analyses were utilized to identify predictors of PERT activation and advanced therapy. Using the log odd ratio of each significant predictor of advanced therapy, we created a scoring system and a score of 2 was associated with the highest use. Primary outcomes were 30- and 90-day all-cause mortality, readmission, and major bleed. RESULTS: Of the 307 patients, PERT was activated in 22.5%. While abnormal vital signs and right ventricular (RV) strain were associated with PERT activation, pulmonary embolism severity index (PESI) was not. Advanced therapy use was significantly higher in the PERT cohort (35% vs 2%). Predictors of advanced therapy use were composite variable (heart rate > 110 or systolic blood pressure < 100 or respiratory rate > 30 or oxygen saturation < 90%) and right-to-left ventricular ratio > 0.9. PERT patients with advanced therapy use, when compared to the no-PERT patients who could have qualified (score of 2), had significantly lower 30- and 90-day mortality and 30-day readmission without difference in major bleed. CONCLUSION: PERT has important therapeutic impact, yet no guidelines to direct activation. We recommend a multidisciplinary approach for higher acuity pulmonary embolism cases and physician education regarding PERT and the scope of advanced therapy use.

Prospective Experience of Pulmonary Embolism Management and Outcomes.

OBJECTIVE: We sought to evaluate the impact of pulmonary embolism (PE) response teams (PERTs) on all consecutive patients with PE. BACKGROUND: Multidisciplinary PERTs have been promoted for the management and treatment of (PE); however, the impact of PERTs on clinical outcomes has not been prospectively evaluated. METHODS: We prospectively studied 220 patients with computed tomography (CT)-confirmed PE between January, 2019 and August, 2019. Baseline characteristics, as well as medical, interventional, and operational care, were captured. The total population was divided into 2 groups, ie, those with PERT activation and those without PERT activation. PERT activation was left at the discretion of the primary team. Our primary outcome was 90-day composite endpoint (rate of readmission, major bleeds, and mortality). Using 2:1 propensity-matched and multivariable-adjusted Cox proportional hazard analyses, we examined the impact of PERT activation on primary outcome, treatment approach, and length of stay. RESULTS: Of the total 220 patients, PERT was activated in 47 (21.4%). The PERT cohort, as compared with the non-PERT cohort, was more likely to present with dyspnea, syncope, lower systolic blood pressure, higher heart rate, higher respiratory rate, lower oxygen saturation, higher troponin levels, and higher right ventricular to left ventricular ratio. PERT activation was associated with increased use of advanced therapies (36.2% vs 1.2%; P<.001) and catheter-directed inventions (25.5% vs 0.6%; P<.001). In multivariable-adjusted analysis of propensity-matched cohorts, PERT activation was associated with lower 90-day outcomes (hazard ratio, 0.40; 95% confidence interval, 0.21-0.75; P<.01). CONCLUSION: At our institution, PERT had a clinically significant impact on therapeutic strategies and 90-day outcomes in patients with PE.

Evaluation of dyspnea of unknown etiology in HIV patients with cardiopulmonary exercise testing and cardiovascular magnetic resonance imaging.

AIM: Human Immunodeficiency Virus (HIV) patients commonly experience dyspnea for which an immediate cause may not be always apparent. In this prospective cohort study of HIV patients with exercise limitation, we use cardiopulmonary exercise testing (CPET) coupled with exercise cardiovascular magnetic resonance (CMR) to elucidate etiologies of dyspnea. METHODS AND RESULTS: Thirty-four HIV patients on antiretroviral therapy with dyspnea and exercise limitation (49.7 years, 65% male, mean absolute CD4 count 700) underwent comprehensive evaluation with combined rest and maximal exercise treadmill CMR and CPET. The overall mean oxygen consumption (VO2) peak was reduced at 23.2 ± 6.9 ml/kg/min with 20 patients (58.8% of overall cohort) achieving a respiratory exchange ratio > 1. The ventilatory efficiency (VE)/VCO2 slope was elevated at 36 ± 7.92, while ventilatory reserve (VE: maximal voluntary ventilation (MVV)) was within normal limits. The mean absolute right ventricular (RV) and left ventricular (LV) contractile reserves were preserved at 9.0% ± 11.2 and 9.4% ± 9.4, respectively. The average resting and post-exercise mean average pulmonary artery velocities were 12.2 ± 3.9 cm/s and 18.9 ± 8.3 respectively, which suggested lack of exercise induced pulmonary artery hypertension (PAH). LV but not RV delayed enhancement were identified in five patients. Correlation analysis found no relationship between peak VO2 measures of contractile RV or LV reserve, but LV and RV stroke volume correlated with PET CO2 (p = 0.02, p = 0.03). CONCLUSION: Well treated patients with HIV appear to have conserved RV and LV function, contractile reserve and no evidence of exercise induced PAH. However, we found evidence of impaired ventilation suggesting a non-cardiopulmonary etiology for dyspnea.

Cyclic compression increases F508 Del CFTR expression in ciliated human airway epithelium.

The mechanisms by which transepithelial pressure changes observed during exercise and airway clearance can benefit lung health are challenging to study. Here, we have studied 117 mature, fully ciliated airway epithelial cell filters grown at air-liquid interface grown from 10 cystic fibrosis (CF) and 19 control subjects. These were exposed to cyclic increases in apical air pressure of 15 cmH2O for varying times. We measured the effect on proteins relevant to lung health, with a focus on the CF transmembrane regulator (CFTR). Immunoflourescence and immunoblot data were concordant in demonstrating that air pressure increased F508Del CFTR expression and maturation. This effect was in part dependent on the presence of cilia, on Ca2+ influx, and on formation of nitrogen oxides. These data provide a mechanosensory mechanism by which changes in luminal air pressure, like those observed during exercise and airway clearance, can affect epithelial protein expression and benefit patients with diseases of the airways.

Periodic breathing in healthy young adults in normobaric hypoxia equivalent to 3500 m, 4500 m, and 5500 m altitude.

PURPOSE: The occurrence of periodic breathing (PB) at high altitude during sleep and the quality of sleep are individually different and influenced by multiple factors including sex. Although poor sleep quality at high altitude might not be directly linked to oxygen desaturations, the PB upsurge at high altitude leads to significant oscillations in oxygen saturation. METHODS: Thirty-three students were recruited. Participants were randomly assigned to three groups (A, B, C) sleeping one full night in a dormitory with normobaric hypoxia at a FIO2 of 14.29% (A), a FIO2 of 12.47% (B), or a FIO2 of 10.82% (C). Full polysomnography was performed in each participant. RESULTS: Mean total sleeping time decreased significantly with increasing hypoxia (p < 0.001). Respiratory events changed from central hypopneas to central apneas (CA) with increasing hypoxia: CA = 17.8%, 50.0%, 92.2% of AHI (37.96 events per hour (n/h), 68.55 n/h, 93.44 n/h). AHI (p = 0.014) and time duration of respiratory events (p = 0.003) were significantly different between sexes, both greater in men. REM sleep was reduced. CONCLUSIONS: Men tend to be more prone to PB in normobaric hypoxia. Further research should implicate a longer acclimatization period around simulated 4500 m in order to find out if the exponential increase in PB between 4500 m and 5500 m could be shifted to lower hypoxic levels, i.e., higher altitudes.

Long-term experience with diaphragm pacing for traumatic spinal cord injury: Early implantation should be considered.

BACKGROUND: Cervical spinal cord injury can result in catastrophic respiratory failure requiring mechanical ventilation with high morbidity, mortality, and cost. Diaphragm pacing was developed to replace/decrease mechanical ventilation. We report the largest long-term results in traumatic cervical spinal cord injury. METHODS: In this retrospective review of prospective institutional review board protocols, all patients underwent laparoscopic diaphragm mapping and implantation of electrodes for diaphragm strengthening and ventilator weaning. RESULTS: From 2000 to 2017, 92 patients out of 486 diaphragm pacing implants met the criteria. The age at time of injury ranged from birth to 74 years (average: 27 years). Time on mechanical ventilation was an average of 47.5 months (range, 6 days to 25 years, median = 1.58 years). Eighty-eight percent of patients achieved the minimum of 4 hours of pacing. Fifty-six patients (60.8%) used diaphragm pacing 24 hours a day. Five patients had full recovery of breathing with subsequent diaphragm pacing removal. Median survival was 22.2 years (95% confidence interval: 14.0-not reached) with only 31 deaths. Subgroup analysis revealed that earlier diaphragm pacing implantation leads to greater 24-hour use of diaphragm pacing and no need for any mechanical ventilation. CONCLUSION: Diaphragm pacing can successfully decrease the need for mechanical ventilation in traumatic cervical spinal cord injury. Earlier implantation should be considered.

Completed FDA feasibility trial of surgically placed temporary diaphragm pacing electrodes: A promising option to prevent and treat respiratory failure.

BACKGROUND: Etiologies contributing to failure to wean from mechanical ventilation (MV) are multiple, resulting in morbid and costly outcomes. Diaphragm pacing (DP) is used in spinal cord injury to replace MV. Temporary DP could be utilized in acute respiratory failure to reduce MV. METHODS: A prospective FDA feasibility trial evaluated temporary DP electrodes implanted in each hemi-diaphragm during a subject's primary procedure. Objectives included: ability to provide ventilation, stability analysis with diaphragm electromyography, and adverse event monitoring. RESULTS: Twelve patients underwent successful implantation via median sternotomy, laparoscopy or laparotomy. Electrode stimulation exceeded ideal tidal volumes by an average of 37% (0%-95%) confirming ability to prevent atrophy. Daily electromyography confirmed stability of placement and was useful in evaluating hypoventilation. There were no complications and all 48 study electrodes remained intact until complete removal. CONCLUSION: This trial demonstrates ease of placement, removal, functionality and safety of temporary DP electrodes which therapeutically decreases diaphragm atrophy.

The Role of Echocardiography in the Evaluation of Pulmonary Arterial Hypertension.

The evaluation of pulmonary arterial hypertension (PAH) requires a multimodality approach that combines invasive and noninvasive imaging studies to ensure accurate diagnosis and classification. Given the complexity of the hemodynamic relationships between the left heart, pulmonary circulation, and right heart, the diagnosis of PAH is often a challenging task. Right heart catheterization is the gold standard for diagnosis, providing the hemodynamic information that defines the disease. Nonetheless, echocardiography continues to be a valuable tool in the approach to the patient with suspected PAH. Echocardiographic assessment generates a wealth of information about the response of the right heart to elevated pulmonary pressures and provides essential diagnostic and prognostic data to the clinician. Numerous measurements can be used to identify alterations in right heart morphology, pressure, and function; although each variable in isolation may have little utility, meaningful information is revealed when multiple parameters are considered together. In this article, we will review the echocardiographic measurements employed in assessment of the right heart and seek to clarify the role of echocardiography in the diagnostic workup of PAH.