Use of the Hypoxia–Age–Shock Index at Triage to Predict Mortality in Geriatric STEMI Patients Undergoing Primary PCI

Response to Academic Editor Comment

Thank you for this insightful comment and for the opportunity to clarify this important methodological point.

Patients who arrived at the emergency department (ED) via ambulance were not excluded from the present study. In our study design, the inclusion criteria comprised two categories of patients: (1) patients breathing room air at the time of ED arrival, and (2) patients transported by ambulance.

For patients transported by emergency medical services (EMS), peripheral oxygen saturation (SpO₂) was routinely measured by emergency medical technicians (EMTs) prior to the initiation of any supplemental oxygen therapy in the prehospital setting. This initial SpO₂ measurement, obtained while the patient was breathing room air, was used by EMTs as part of their standard clinical assessment to determine the need for oxygen administration. Importantly, for the purposes of this study, we deliberately selected this first recorded prehospital SpO₂ value before oxygen supplementation for HASI calculation.

Upon arrival at the ED, although some patients were initially assessed while receiving supplemental oxygen, triage nurses routinely removed oxygen devices and reassessed SpO₂ as part of standard triage procedures. However, to ensure consistency and to avoid the confounding effects of oxygen therapy, we did not use these post-intervention measurements. Instead, we consistently used the earliest available SpO₂ value obtained while patients were breathing room air, including those measured in the prehospital setting prior to oxygen administration.

Therefore, patients who received supplemental oxygen during ambulance transport were not excluded, and their baseline oxygenation status was appropriately captured using pre-oxygen SpO₂ measurements recorded by prehospital staff. We have revised the Methods section to explicitly clarify this point and to improve transparency regarding SpO₂ data acquisition.

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We have revised 2.3. Definition of Physiologic Indices as follows:

Three hemodynamic indices were calculated at triage to quantify circulatory and oxygenation status. The SI was defined as the ratio of heart rate (beats per minute) to systolic blood pressure (mmHg). The ASI was calculated by multiplying the patient’s chronological age by the SI, thereby incorporating the effect of age into the assessment of hemodynamic instability. The HASI was computed by dividing the ASI by SpO₂, integrating oxygenation into the age-adjusted shock model [6].

Notably, the SpO₂ values used for HASI calculation were defined as the earliest available measurements obtained while patients were breathing room air, including those recorded in the prehospital setting by emergency medical technicians prior to the initiation of supplemental oxygen therapy for patients transported by ambulance. For patients arriving at the emergency department without prehospital oxygen supplementation, the first SpO₂ measurement obtained at ED triage while breathing room air was used. Post-intervention SpO₂ measurements obtained after oxygen administration were not used for analysis to avoid confounding effects of supplemental oxygen therapy.

All indices were derived from the first recorded vital signs reflecting baseline physiological status prior to the administration of pharmacologic therapy or performance of PCI. This pragmatic marker at initial assessment captures the early physiological state and potential pulmonary congestion or systemic hypoperfusion associated with acute myocardial infarction.

Response to Reviewer

We sincerely thank the reviewer for their careful reassessment of our revised manuscript. We greatly appreciate the reviewer’s time and effort and are pleased to learn that there are no further comments or concerns at this stage.

Response to Reviewer

We sincerely thank the reviewer for the careful evaluation of our revised manuscript and for the positive assessment. We appreciate the reviewer’s recognition of our responses and the substantial revisions made to improve the clarity and quality of the manuscript.

Response to Academic Editor Comment

Thank you for this insightful comment and for the opportunity to clarify this important methodological point.

Patients who arrived at the emergency department (ED) via ambulance were not excluded from the present study. In our study design, the inclusion criteria comprised two categories of patients: (1) patients breathing room air at the time of ED arrival, and (2) patients transported by ambulance.

For patients transported by emergency medical services (EMS), peripheral oxygen saturation (SpO₂) was routinely measured by emergency medical technicians (EMTs) prior to the initiation of any supplemental oxygen therapy in the prehospital setting. This initial SpO₂ measurement, obtained while the patient was breathing room air, was used by EMTs as part of their standard clinical assessment to determine the need for oxygen administration. Importantly, for the purposes of this study, we deliberately selected this first recorded prehospital SpO₂ value before oxygen supplementation for HASI calculation.

Upon arrival at the ED, although some patients were initially assessed while receiving supplemental oxygen, triage nurses routinely removed oxygen devices and reassessed SpO₂ as part of standard triage procedures. However, to ensure consistency and to avoid the confounding effects of oxygen therapy, we did not use these post-intervention measurements. Instead, we consistently used the earliest available SpO₂ value obtained while patients were breathing room air, including those measured in the prehospital setting prior to oxygen administration.

Therefore, patients who received supplemental oxygen during ambulance transport were not excluded, and their baseline oxygenation status was appropriately captured using pre-oxygen SpO₂ measurements recorded by prehospital staff. We have revised the Methods section to explicitly clarify this point and to improve transparency regarding SpO₂ data acquisition.

---------------------------------------------------------------------------------------------------------------

We have revised 2.3. Definition of Physiologic Indices as follows:

Three hemodynamic indices were calculated at triage to quantify circulatory and oxygenation status. The SI was defined as the ratio of heart rate (beats per minute) to systolic blood pressure (mmHg). The ASI was calculated by multiplying the patient’s chronological age by the SI, thereby incorporating the effect of age into the assessment of hemodynamic instability. The HASI was computed by dividing the ASI by SpO₂, integrating oxygenation into the age-adjusted shock model [6].

Notably, the SpO₂ values used for HASI calculation were defined as the earliest available measurements obtained while patients were breathing room air, including those recorded in the prehospital setting by emergency medical technicians prior to the initiation of supplemental oxygen therapy for patients transported by ambulance. For patients arriving at the emergency department without prehospital oxygen supplementation, the first SpO₂ measurement obtained at ED triage while breathing room air was used. Post-intervention SpO₂ measurements obtained after oxygen administration were not used for analysis to avoid confounding effects of supplemental oxygen therapy.

All indices were derived from the first recorded vital signs reflecting baseline physiological status prior to the administration of pharmacologic therapy or performance of PCI. This pragmatic marker at initial assessment captures the early physiological state and potential pulmonary congestion or systemic hypoperfusion associated with acute myocardial infarction.

Response to Reviewer

We sincerely thank the reviewer for their careful reassessment of our revised manuscript. We greatly appreciate the reviewer’s time and effort and are pleased to learn that there are no further comments or concerns at this stage.

Response to Reviewer

We sincerely thank the reviewer for the careful evaluation of our revised manuscript and for the positive assessment. We appreciate the reviewer’s recognition of our responses and the substantial revisions made to improve the clarity and quality of the manuscript.