Arterial to end-tidal CO2 gradient as an indicator of silent pulmonary embolism

Cardiopulmonary exercise testing in transthyretin amyloid cardiomyopathy patients: a long-term follow-up study

AIMS

Patients with transthyretin amyloid cardiomyopathy (ATTR-CM) experience reduced functional capacity. We evaluated changes in functional capacity over extensive follow-up using cardiopulmonary exercise testing (CPX).

METHODS

ATTR-CM patients underwent CPX and blood testing at baseline, first [V1, 8 (6-10) months] and second follow-up (V2) at 35 (26-41) months after start of disease-specific therapy.

RESULTS

We included 34 ATTR-CM patients, aged 77 (±6) years (88.2% men). CPX showed two patterns with functional capacity improvement at V1 and deterioration at V2. Peak work capacity (P = 0.005) and peak oxygen consumption (VO2, P = 0.012) increased at V1 compared with baseline and decreased at V2. The ventilation to carbon dioxide relationship slope (VE/VCO2) increased at V2 compared with baseline and V1 (P = 0.044). A cut-off for peak VO2 at 14 ml/kg·min showed more events (composite of death and heart failure hospitalization): less than 14 vs. greater than 14 ml/kg·min (P = 0.013). Cut-offs for VE/VCO2 slope at 40 showed more events greater than 40 vs. less than 40 (P = 0.009).

CONCLUSION

ATTR-CM patients showed an improvement and deterioration in the short-term and long-term follow-up, respectively, with a better prognosis for those with peak VO2 above 14 ml/kg·min and for a VE/VCO2 slope below 40.

Integrative physiological assessment of cerebral hemodynamics and metabolism in acute ischemic stroke

Restoring perfusion to ischemic tissue is the primary goal of acute ischemic stroke care, yet only a small portion of patients receive reperfusion treatment. Since blood pressure (BP) is an important determinant of cerebral perfusion, effective BP management could facilitate reperfusion. But how BP should be managed in very early phase of ischemic stroke remains a contentious issue, due to the lack of clear evidence. Given the complex relationship between BP and cerebral blood flow (CBF)-termed cerebral autoregulation (CA)-bedside monitoring of cerebral perfusion and oxygenation could help guide BP management, thereby improve stroke patient outcome. The aim of INFOMATAS is to 'identify novel therapeutic targets for treatment and management in acute ischemic stroke'. In this review, we identify novel physiological parameters which could be used to guide BP management in acute stroke, and explore methodologies for monitoring them at the bedside. We outline the challenges in translating these potential prognostic markers into clinical use.

End-tidal arterial CO2 partial pressure gradient in patients with severe hypercapnia undergoing noninvasive ventilation

BACKGROUND

Patients with severe hypercapnia represent a particularly serious condition in an emergency department (ED), requiring immediate attention. Noninvasive ventilation (NIV) is an integral part of the treatment for acute respiratory failure. The present study aimed to validate the measurement of end-tidal CO2 (EtCO2) as a noninvasive technique to evaluate the effectiveness of NIV in acute hypercapnic respiratory failure.

METHODS

Twenty consecutive patients admitted to the ED with severe dyspnea were enrolled in the study. NIV by means of bilevel positive airway pressure, was applied to the patients simultaneously with standard medical therapy and continued for 12 hours; the arterial blood gases and side-stream nasal/oral EtCO2 were measured at subsequent times: T0 (admission to the ED), T1h (after 1 hour), T6h (after 6 hours), and T12h (after 12 hours) during NIV treatment.

RESULTS

The arterial CO2 partial pressure (PaCO2)-EtCO2 gradient decreased progressively, reaching at T6h and T12h values lower than baseline (P < 0.001), while arterial pH increased during the observation period (P < 0.001). A positive correlation was found between EtCO2 and PaCO2 values (r = 0.89, P < 0.001) at the end of the observation period.

CONCLUSION

In our hypercapnic patients, the effectiveness of the NIV was evidenced by the progressive reduction of the PaCO2-EtCO2 gradient. The measurement of the CO2 gradient could be a reliable method in monitoring the effectiveness of NIV in acute hypercapnic respiratory failure in the ED.

Lethal pulmonary thromboembolism misdiagnosed as pneumonia: A case report

Although pulmonary thromboembolism (PTE) is not rare, unfortunately for anesthesiologists, the signs and symptoms of PTE are unreliable and nonspecific. PTE is a potentially lethal condition without an accurate diagnosis and prompt treatment. We report a case of PTE misdiagnosed as simple pneumonia. A 60-year-old female, not receiving prophylactic anticoagulant therapy, underwent elective surgery for a left proximal tibial fracture. During induction of general anesthesia, a temporary bronchospasm occurred and subsided quickly. Because vital signs were stable and patient monitoring was normal, we did not identify a serious hypercarbic condition. After surgery, a massive hemoptysis occurred and the patient expired due to cardiopulmonary collapse. According to autopsy, the cause of death was a PTE originating in deep vein thrombosis.

Prognostic value of end-tidal CO2 pressure during exercise in patients with left ventricular dysfunction

We compared the prognostic power of end-tidal CO(2) pressure (PETCO(2)) during exercise, an index of arterial CO(2) pressure, with those of established respiratory gas indexes during exercise testing in patients with left ventricular dysfunction. Seventy-eight consecutive patients with a left ventricular ejection fraction (LVEF) Collapse

Key Words

• end-tidal co₂ pressure
• peak \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\rm{v}} $$\end{document}o₂
• exercise testing

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MESH Headings

• Aged
• Carbon Dioxide/metabolism
• Exercise/physiology
• Exercise Test/methods
• Female
• Follow-Up Studies
• Humans
• Kaplan-Meier Estimate
• Male
• Middle Aged
• Oxygen Consumption/physiology
• Predictive Value of Tests
• Prognosis
• Prospective Studies
• ROC Curve
• Respiratory Function Tests/methods
• Risk Factors
• Stroke Volume/physiology
• Ventricular Dysfunction, Left/diagnosis
• Ventricular Dysfunction, Left/mortality
• Ventricular Dysfunction, Left/physiopathology

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Affiliation(s)

Masayo Hoshimoto-Iwamoto The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan School of Health and Sports Science, Juntendo University, Chiba, Japan
Akira Koike The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Osamu Nagayama The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Akihiko Tajima The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Takeya Suzuki Department of Cardiovascular Medicine, Toho University Omori Medical Center, Tokyo, Japan
Tokuhisa Uejima The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Hitoshi Sawada The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Tadanori Aizawa The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan

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Early aerobic training increases end-tidal CO2 pressure during exercise in patients after acute myocardial infarction

BACKGROUND

End-tidal CO2 partial pressure (PETCO2) has been suggested as a noninvasive index reflecting cardiac output under constant ventilation. The aim of this study was to examine whether PETCO2 does reflect cardiac output, even during exercise, in patients with acute myocardial infarction (AMI) undergoing exercise training early after onset. Method and Results Patients aged 47-73 years were randomly assigned to either a training group (n=18) or a control group (n=18) 1 week after the onset of AMI. Those in the training group performed exercise training under supervision at the anaerobic threshold level for 2 weeks, while patients in the control group followed a conventional walking regimen. In the training group, but not in the control group, PETCO2 at the respiratory compensation point increased significantly from 39.1+/-3.5 to 41.1+/-3.7 mmHg (p<0.01). Similarly, the cardiac index at peak exercise increased only in the training group (from 6.04+/-0.98 to 7.31+/-0.97 L/min per m2, p<0.01). These 2 measurements correlated well both before and after the study period. Peak oxygen uptake and anaerobic threshold were increased only in the training group. Conclusions Aerobic exercise training early after the onset of AMI significantly increased PETCO2 during exercise, which may reflect an improvement in cardiac output during exercise in response to physical training via a decreased ventilation-perfusion mismatch.

Monitoring for suspected pulmonary embolism

It is fortunate that serious embolic phenomena are uncommon because, with the exception of neurosurgery in the sitting position and cardiac surgery, thoracic echocardiography and the precordial Doppler device, the most sensitive indicators of embolism, are seldom used. Vigilance is required of the anesthesiologist to recognize the rapid fall in end-tidal PCO2, the usual first indicator of a clinically significant PE. Any sudden deterioration in the patient's vital signs should include embolism in the differential diagnosis, particularly during procedures that carry a high risk of the complication.

PaCO(2)/ETCO(2) gradient: early indicator of thrombolysis efficacy in a massive pulmonary embolism

End tidal CO(2) measurement may be helpful in detecting the efficacy of thrombolysis after a massive pulmonary embolism. We report the case of a 76-year-old man with a massive pulmonary embolism, who required early intubation and mechanical ventilation. Thrombolysis with rtpA (total dosage: 60 mg) was initiated. During this procedure, clinical data, arterial blood gases and end-tidal CO(2) with a capnograph were recorded. Before thrombolysis the P(a-ET)CO(2) gradient was raised to 25 mmHg. During thrombolysis, the clinical data improved and the P(a-ET) gradient fell to 14 mmHg. We postulate that the P(a-ET)CO(2) gradient seems to be a reasonable indicator of efficacy of thrombolysis in this setting. However, the gradient did not return to normal values (4-5 mmHg). The possible reasons for this may be that during mechanical ventilation there was a large ventilation-perfusion ratio and the cardiac output may have still reduced. With these limitations, we conclude that the P(a-ET)CO(2) gradient should be evaluated as an indicator of pulmonary reperfusion in massive pulmonary embolism.

End-tidal CO2 pressure decreases during exercise in cardiac patients: association with severity of heart failure and cardiac output reserve

OBJECTIVES

We measured end-tidal CO2 pressure (PETCO2) during exercise and investigated the relationship between PETCO2 and exercise capacity, ventilatory parameters and cardiac output to determine the mechanism(s) of changes in this parameter.

BACKGROUND

It is unclear whether PETCO2 is abnormal at rest and during exercise in cardiac patients.

METHODS

Cardiac patients (n = 112) and normal individuals (n = 29) performed exercise tests with breath-by-breath gas analysis, and measurement of cardiac output and arterial blood gases.

RESULTS

PETCO2 was lower in patients than in normal subjects at rest and decreased as the New York Heart Association class increased, whereas the partial pressure of arterial CO2 did not differ among groups. Although PETCO2 increased during exercise in patients, it remained lower than in normal subjects. PETCO2 in relation to cardiac output was similar in patients and normal subjects. PETCO2 at the respiratory compensation point was positively correlated with the O2 uptake (r = 0.583, p < 0.0001) and the cardiac index at peak exercise (r = 0.582, p < 0.0001), and was negatively correlated with the ratio of physiological dead space to the tidal volume. The sensitivity and specificity of PETCO2 to predict an inadequate cardiac output were 76.6% and 75%, respectively, when PETCO2 at respiratory compensation point and a cardiac index at peak exercise that were less than the respective control mean-2 SD values were considered to be abnormal.

CONCLUSIONS

PETCO2 was below normal in cardiac patients at rest and during exercise. PETCO2 was correlated with exercise capacity and cardiac output during exercise, and the sensitivity and specificity of PETCO2 regarding decreased cardiac output were good. PETCO2 may be a new ventilatory abnormality marker that reflects impaired cardiac output response to exercise in cardiac patients diagnosed with heart failure.

Capnometry as a tool to unmask silent pulmonary embolism

Because pulmonary embolism is often silent, simple clinical procedures are desirable to identify patients with a low to intermediate probability of pulmonary embolism. Among 19,467 patients managed under general anesthesia, we had one bile tract surgery case and three neurosurgical cases whose silent pulmonary embolism was initially suggested by an increase in the arterial to end-tidal CO2 gradient (from 17 to 27 mmHg) after general anesthesia was induced or their trachea was intubated. During the preoperative assessment, the patients presented no clinical manifestations suggestive of pulmonary embolism. Our initial diagnosis was confirmed by scintigraphy and/or angiography done immediately after the operations. Because capnometry has been shown to be applicable to non-intubated, spontaneously breathing patients, we suggest that measuring the gradient may serve as an additional method for unmasking silent pulmonary embolism in patients at risk or with disturbed consciousness, whether they are scheduled for operations or not.