Pulmonary Endarterectomy Improves Dyspnea by the Relief of Dead Space Ventilation

doi:10.1016/j.athoracsur.2009.08.001

The Annals of Thoracic Surgery

Volume 89, Issue 2, February 2010, Pages 347-352

https://doi.org/10.1016/j.athoracsur.2009.08.001 Get rights and content

Background

In chronic thromboembolic pulmonary hypertension (CTEPH), dyspnea is considered to be related to increased dead space ventilation caused by vascular obstruction. Pulmonary endarterectomy releases the thromboembolic obstruction, thereby improving regional pulmonary blood flow. We hypothesized that pulmonary endarterectomy reduces dead space ventilation and that this reduction contributes to attenuation of dyspnea symptoms.

Methods

In this follow-up study we assessed dead space ventilation, hemodynamic severity of disease, and symptomatic dyspnea in 54 consecutive CTEPH patients, before and 1 year after pulmonary endarterectomy. Dead space ventilation was calculated using the Bohr-Enghoff equation. Dyspnea was assessed by Borg scores and the New York Heart Association functional classification.

Results

Preoperatively, dead space ventilation was increased (0.40 ± 0.07) and correlated with severity of disease (mean pulmonary artery pressure: r = 0.49, p < 0.001; total pulmonary resistance: r = 0.53, p < 0.001), and resting (r = 0.35, p < 0.05) and post-exercise Borg dyspnea scores (r = 0.44, p < 0.01). Postoperatively, dead space ventilation (0.33 ± 0.08, p < 0.001) and dyspnea symptoms decreased significantly. Changes in symptomatic dyspnea were independently associated with changes in pulmonary hemodynamics and absolute dead space.

Conclusions

Dead space ventilation in CTEPH is increased and correlates significantly with hemodynamic severity of disease and dyspnea symptoms. Pulmonary endarterectomy decreases dead space ventilation. The induced change in dead space upon surgical removal of chronic thromboembolism contributes to the postoperative recovery of symptomatic dyspnea.

Section snippets

Material and Methods

The research protocol for this study was approved by the local Institutional Review Board and the study was conducted in accordance with the principles of the Declaration of Helsinki.

Patient Characteristics

The study included 54 consecutive patients (21 men, 33 women) who were a mean age of 51 ± 13.9 (range, 16–77 years). Most of the 48 patients with pulmonary arterial hypertension at rest had moderate to severe pulmonary hypertension, with a median mPAP of 48 mm Hg (range, 26–75 mm Hg) and a median total pulmonary resistance (TPR) of 800 (dynes · s · cm⁻⁵ (range, 346 to 1875 dynes · s · cm⁻⁵). Six additional patients with exercise-induced pulmonary hypertension presented disabling impairment of exercise

Comment

In the present study, we demonstrated increased dead space ventilation in patients with CTEPH, which correlated significantly with hemodynamic severity of disease and patient-reported sensations of dyspnea. After PEA, dead space ventilation decreased and normalized in most patients. Moreover, the observed change in absolute dead space after PEA was independently associated with the reported changes in resting Borg score and NYHA functional class. Hence, although the primary objective of PEA is

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Cited by (55)

Performance-based outcome measures for assessing physical capacity in patients with pulmonary embolism: A scoping review
2024, Thrombosis Research
Up to 50 % of patients surviving a pulmonary embolism (PE) report persisting shortness of breath, reduced physical capacity and psychological distress. As the PE population is heterogeneous compared to other cardiovascular patient groups, outcome measures for assessing physical capacity traditionally used in cardiac populations may not be reliable for the PE population as a whole. This scoping review aims to 1) map performance-based outcome measures (PBOMs) used for assessing physical capacity in PE research, and 2) to report the psychometric properties of the identified PBOMs in a PE population.
The review was conducted according to the Joanna Briggs Institute framework for scoping reviews and reported according to the PRISMA-Extension for Scoping Reviews guideline.
The systematic search of five databases identified 4585 studies, of which 243 studies met the inclusion criteria. Of these, 185 studies focused on a subgroup of patients with chronic thromboembolic pulmonary hypertension. Ten different PBOMs were identified in the included studies. The 6-minute walk test (6MWT) and cardiopulmonary exercise test (CPET) were the most commonly used, followed by the (Modified) Bruce protocol and Incremental Shuttle Walk test. No studies reported psychometric properties of any of the identified PBOMs in a PE population.
Publication of studies measuring physical capacity within PE populations has increased significantly over the past 5–10 years. Still, not one study was identified, reporting the validity, reliability, or responsiveness for any of the identified PBOMs in a PE population. This should be a priority for future research in the field.
Exercise hyperventilation and pulmonary gas exchange in chronic thromboembolic pulmonary hypertension: Effects of balloon pulmonary angioplasty
2022, Journal of Heart and Lung Transplantation
Citation Excerpt :
It has been reported in a single study that changes in DLCO might be different depending on the lung regions targeted by BPA.31 Nevertheless, we consider that these findings cannot be applied to most CTEPH patients, for at least two reasons: firstly, patients included in this study had significant airflow limitation, a condition that may differently influence DLCO measurement depending on the etiology of airflow limitation (e.g., lower DLCO if airflow limitation is due to emphysema and higher DLCO if it is due to asthma32); secondly, patients included in this study who improved DLCO after BPA had intriguing findings at CPET: before BPA, their end-tidal CO2 fraction was 4.83% (corresponding to a PETCO2 of around 34.5 mm Hg, a value that is much higher compared with values reported in the literature for CTEPH patients eligible for BPA) and their V̇E/V̇CO2 slope was 35, a value that is much lower than values reported in CTEPH patients undergoing BPA.8,10,12,20,33-35 Our results suggest hypothesis regarding the mechanisms by which BPA improves pulmonary gas exchange.
Excessive ventilation (V̇E) and abnormal gas exchange during exercise are features of chronic thromboembolic pulmonary hypertension (CTEPH). In selected CTEPH patients, balloon pulmonary angioplasty (BPA) improves symptoms and exercise capacity. How BPA affects exercise hyperventilation and gas exchange is poorly understood.
In this longitudinal observational study, symptom-limited cardiopulmonary exercise tests and carbon monoxide lung diffusion (DLCO) were performed before and after BPA (interval, mean (SD): 3.1 (2.4) months) in 36 CTEPH patients without significant cardiac and/or pulmonary comorbidities.
Peak work rate improved by 20% after BPA whilst V̇E at peak did not change despite improved ventilatory efficiency (lower V̇E with respect to CO₂ output [V̇CO₂]). At the highest identical work rate pre- and post-BPA (75 (30) watts), V̇E and alveolar-arterial oxygen gradient (P(Ai-a)O₂) decreased by 17% and 19% after BPA, respectively. The physiological dead space fraction of tidal volume (VD/VT), calculated from measurements of arterial and mixed expired CO₂, decreased by 20%. In the meantime, DLCO did not change. The best correlates of P(Ai-a)O₂ measured at peak exercise were physiological VD/VT before BPA and DLCO after BPA.
Ventilatory efficiency, physiological VD/VT, and pulmonary gas exchange improved after BPA. The fact that DLCO did not change suggests that the pulmonary capillary blood volume and probably the true alveolar dead space were unaffected by BPA. The correlation between DLCO measured before BPA and P(Ai-a)O₂ measured after BPA suggests that DLCO may provide an easily accessible marker to predict the response to BPA in terms of pulmonary gas exchange.
Chronic Thromboembolic Pulmonary Hypertension: JACC Focus Seminar
2020, Journal of the American College of Cardiology
Citation Excerpt :
Approximately 25% of patients will not provide a prior history of acute embolism (27). As in other forms of PH, the complaint common to patients with CTEPH is progressive exercise intolerance and/or exertional dyspnea, which physiologically appear related to a limitation in cardiac output as well as to an increased dead space ventilation (34). As the disease progresses and RV dysfunction worsens, lower extremity swelling, abdominal distention, early satiety, chest pain or pressure, and exertional light-headedness with or without syncope may also present.
Chronic thromboembolic pulmonary hypertension (CTEPH) is the result of pulmonary arterial obstruction by organized thrombotic material stemming from incompletely resolved acute pulmonary embolism. The exact incidence of CTEPH is unknown but appears to approximate 2.3% among survivors of acute pulmonary embolism. Although ventilation/perfusion scintigraphy has been supplanted by computed tomographic pulmonary angiography in the diagnostic approach to acute pulmonary embolism, it has a major role in the evaluation of patients with suspected CTEPH, the presence of mismatched segmental defects being consistent with the diagnosis. Diagnostic confirmation of CTEPH is provided by digital subtraction pulmonary angiography, preferably performed at a center familiar with the procedure and its interpretation. Operability assessment is then undertaken to determine if the patient is a candidate for potentially curative pulmonary endarterectomy surgery. When pulmonary endarterectomy is not an option, pulmonary arterial hypertension–targeted pharmacotherapy and balloon pulmonary angioplasty represent potential therapeutic alternatives.
Critical Care of Patients After Pulmonary Thromboendarterectomy
2019, Journal of Cardiothoracic and Vascular Anesthesia
Citation Excerpt :
Prolonged utilization of iNO via high-flow or regular nasal cannula can promote the patient's recovery by allowing earlier mobilization and activity, but individual responsiveness to iNO and improvement in oxygenation should be evaluated during its use. Slow weaning of iNO and FIO2 often is warranted in patients with severe post-PTE hypoxia, and supplemental oxygen may be needed for months after hospital discharge.71,87 Throughout the early postoperative period, continuous diuresis for daily negative fluid balances while avoiding overt injury to the kidneys is crucial to minimize further compromise from coexisting pulmonary edema.
Pulmonary thromboendarterectomy (PTE) remains the only curative surgery for patients with chronic thromboembolic pulmonary hypertension (CTEPH). Postoperative intensive care unit care challenges providers with unique disease physiology, operative sequelae, and the potential for detrimental complications. Central concerns in patients with CTEPH immediately after PTE relate to neurologic, pulmonary, hemodynamic, and hematologic aspects. Institutional experience in critical care for the CTEPH population, a multidisciplinary team approach, patient risk assessment, and integration of current concepts in critical care determine outcomes after PTE surgery.
In this review, the authors will focus on specific aspects unique to this population, with integration of current available evidence and future directions. The goal of this review is to provide the cardiac anesthesiologist and intensivist with a comprehensive understanding of postoperative physiology, potential complications, and contemporary intensive care unit management immediately after pulmonary endarterectomy.
Chronic Thromboembolic Pulmonary Hypertension: An Update
2018, Clinics in Chest Medicine
Residual pulmonary hypertension after pulmonary endarterectomy: A meta-analysis
2018, Journal of Thoracic and Cardiovascular Surgery
Chronic thromboembolic pulmonary hypertension is surgically treated through pulmonary endarterectomy. Although pulmonary endarterectomy is the treatment of choice for chronic thromboembolic pulmonary hypertension in terms of both functional outcomes and survival, many patients experience persistent pulmonary hypertension after pulmonary endarterectomy. The study objective was to calculate the pooled estimates of outcomes after pulmonary endarterectomy, including persistent pulmonary hypertension.
Meta-analyses were conducted on published studies reporting residual/persistent/recurrent pulmonary hypertension in 4868 patients with chronic thromboembolic pulmonary hypertension after pulmonary endarterectomy. The rate of persistent pulmonary hypertension and change in mean pulmonary artery pressure, pulmonary vascular resistance, and 6-minute walk distance after pulmonary endarterectomy were outcomes of interest.
Twenty-five percent of patients with chronic thromboembolic pulmonary hypertension were diagnosed with persistent pulmonary hypertension after pulmonary endarterectomy. Pulmonary endarterectomy reduced mean pulmonary artery pressure and pulmonary vascular resistance by approximately 21 mm Hg (standardized mean difference, 1.75; 95% confidence interval, −1.62 to 1.88; P < .00001) and 561 dyn.s/cm⁵ (standardized mean difference, 1.64; 95% confidence interval, −1.58 to 1.70; P < .00001), respectively. Conversely, 6-minute walk distance increased by 96 m (standardized mean difference, −0.83; 95% confidence interval, −0.91 to −0.76; P < .00001) after pulmonary endarterectomy.
Pulmonary endarterectomy is the gold standard treatment for chronic thromboembolic pulmonary hypertension and provides immediate correction of hemodynamic parameters in most patients. However, in up to one quarter of operable cases, pulmonary hypertension persists after surgery. In those patients with persistent pulmonary hypertension, continued medical management with newer agents may be required to improve pulmonary hemodynamics and, therefore, patient outcomes.

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Original articleGeneral thoracicPulmonary Endarterectomy Improves Dyspnea by the Relief of Dead Space Ventilation

Background

Methods

Results

Conclusions

Section snippets

Material and Methods

Patient Characteristics

Comment

Curr Probl Surg

Prog Cardiovasc Dis

Ann Thorac Surg

J Thorac Cardiovasc Surg

J Thorac Cardiovasc Surg

Chest

Clin Chest Med

Respir Physiol

Br J Anaesth

Chest

Chronic thromboembolic pulmonary hypertension

N Engl J Med

Chronic thromboembolic pulmonary hypertension

Circulation

Principles of exercise testing and interpretation

Exercise pathophysiology in patients with primary pulmonary hypertension

Circulation

Pulmonary endarterectomy: experience and lessons learned in 1,500 cases

Ann Thorac Surg

Long-term results after thromboendarterectomy for chronic pulmonary embolism

Eur J Cardiothorac Surg

Mid term effects of pulmonary thromboendarterectomy on clinical and cardiopulmonary function status

Thorax

Original article
General thoracic
Pulmonary Endarterectomy Improves Dyspnea by the Relief of Dead Space Ventilation