The goal of this observational study is to compare the consistency of saline contrast Electrical Impedance Tomography(EIT) method and Computed Tomography Pulmonary Angiography (CTPA) in diagnosing acute pulmonary embolism. The main question it aims to answer is:
Can bedside saline contrast EIT method be used for the diagnosis of acute pulmonary embolism? The participants will undergo saline contrast EIT and CTPA examinations successively within 24 hours.
Patients with clinically suspected or confirmed acute pulmonary embolism (PE) presenting with acute respiratory failure;
Availability of CTPA results within 24 hours or scheduled to undergo CTPA within the next 24 hours;
Age >18 years; no gender restrictions;
Presence of central venous access (internal jugular or subclavian vein) or peripheral forearm venous access;
Pregnancy or lactation;
Relative contraindications to EIT examination (e.g., chest wall wounds at electrode belt placement site, presence of pacemakers);
Severe hypernatremia (serum sodium >155 mmol/L);
Inability to maintain expiratory breath-hold for ≥8 seconds;
Patients with clinically suspected or confirmed acute pulmonary embolism (PE) presenting with acute respiratory failure.
Case-control
Prospective
Saline contrast Electrical Impedance Tomography method
Diagnostic testThis study will enroll patients with clinically suspected or confirmed acute pulmonary embolism (PE) presenting with acute respiratory failure, who undergo electrical impedance tomography (EIT) with saline contrast within 24 hours before or after computed tomography pulmonary angiography (CTPA). The EIT procedure is performed as follows: 1. Breath-Hold Maneuver: (1)Spontaneous breathing patients: Supine position, instructed to hold expiration for ≥8 seconds. (2)Mechanically ventilated patients: Expiratory hold (\>8 sec) achieved via ventilator; deeper sedation will be applied when feasible to prolong breath-hold. 2. Venous Access: (1)Preferred: Central venous catheter (internal jugular or subclavian vein).(2)Alternative: Peripheral forearm vein (preferably the median cubital vein). 3. Contrast Administration:(1)Central venous route: 10 mL of 10% NaCl.(2)Peripheral venous route: 15 mL of 5% NaHCO₃.
Computed Tomography Pulmonary Angiography (CTPA)
Diagnostic testPatients who meet the inclusion criteria will undergo CTPA examination using conventional clinical diagnostic methods.
The ability of proportion of dead space ventilation to diagnose PE
The participant undergoes a saline contrast EIT examination, after which the distribution of pulmonary ventilation and perfusion will be obtained, respectively. A V-Q map will be subsequently generated. Using offline EIT data analysis tool, the proportion of lung regions with ventilation but without perfusion is calculated, representing the proportion of dead space ventilation (expressed as a percentage). Area under the receiver operating characteristic curve (AUROC), sensitivity, specificity, Youden's index, accuracy, Kappa statistic, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR) and negative likelihood ratio (NLR) will be used to evaluate the ability of proportion of dead space ventilation to diagnose acute pulmonary embolism (PE).
The ability of proportion of V/Q matching to diagnose PE
Following a saline contrast EIT examination, the participant's pulmonary ventilation and perfusion distributions will be obtained, allowing for the generation of a V-Q map. Using offline EIT data analysis tool, the proportion of lung regions demonstrating both ventilation and perfusion will be calculated, representing the proportion of V/Q matching (%). Area under the receiver operating characteristic curve (AUROC), sensitivity, specificity, Youden's index, accuracy, Kappa statistic, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR) and negative likelihood ratio (NLR) will be used to evaluate the ability of proportion of V/Q matching to diagnose acute pulmonary embolism (PE).
The ability of proportion of shunt to diagnose PE
Following a saline contrast EIT examination, the participant's pulmonary ventilation and perfusion distributions will be obtained, enabling the generation of a V-Q map. Using offline EIT data analysis tool, the proportion of lung regions exhibiting perfusion without ventilation will be calculated, representing the proportion of shunt (%). Area under the receiver operating characteristic curve (AUROC), sensitivity, specificity, Youden's index, accuracy, Kappa statistic, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR) and negative likelihood ratio (NLR) will be used to evaluate the ability of proportion of shunt to diagnose acute pulmonary embolism (PE).
The ability of other indicators reflecting pulmonary ventilation and perfusion to diagnose PE
Following a saline contrast EIT examination, the participant's pulmonary ventilation and perfusion distributions will be obtained, and a V-Q map will be subsequently generated. Using offline EIT data analysis tool, additional indices reflecting pulmonary ventilation and perfusion will be further calculated. Area under the receiver operating characteristic curve (AUROC), sensitivity, specificity, Youden's index, accuracy, Kappa statistic, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR) and negative likelihood ratio (NLR) will be used to evaluate the ability of other indicators reflecting pulmonary ventilation and perfusion to diagnose acute pulmonary embolism (PE).
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