altitude_adjusted_perc: Altitude-Adjusted PERC Rule for Pulmonary Embolism

In cliot: Clinical Indices and Outcomes Tools

Altitude-Adjusted PERC Rule for Pulmonary Embolism

Description

Applies the Pulmonary Embolism Rule-out Criteria (PERC) with an adjustment for high altitude. Standard PERC requires an oxygen saturation (SaO2) >= 95%. The Altitude-Adjusted PERC lowers this threshold to >= 90% to account for the physiological hypoxia associated with higher elevations, maintaining specificity while preventing unnecessary imaging.

Usage

altitude_adjusted_perc(age, heart_rate, o2_sat, hemoptysis, estrogen_use,
                       surgery_trauma_4wks, prior_vte, unilateral_leg_swelling)

Arguments

age	Numeric. Patient age in years. (Criteria met if < 50).
heart_rate	Numeric. Heart rate in bpm. (Criteria met if < 100).
o2_sat	Numeric. Oxygen saturation in %. (Criteria met if >= 90% for altitude adjustment; Standard is 95%).
hemoptysis	Numeric (0 or 1). Presence of hemoptysis. (Criteria met if 0).
estrogen_use	Numeric (0 or 1). Exogenous estrogen use (OCPs, HRT, etc.). (Criteria met if 0).
surgery_trauma_4wks	Numeric (0 or 1). Recent surgery or trauma requiring hospitalization within 4 weeks. (Criteria met if 0).
prior_vte	Numeric (0 or 1). Prior history of DVT or PE. (Criteria met if 0).
unilateral_leg_swelling	Numeric (0 or 1). Unilateral leg swelling. (Criteria met if 0).

Value

A list containing:

Result	"PERC Negative" (Rule Out) or "PERC Positive" (Cannot Rule Out).
Recommendation	Guidance on the need for further testing (e.g., D-dimer).
Criteria_Violated	List of specific criteria that failed the rule-out.

References

Madsen T, et al. Prospective validation of the pulmonary embolism rule-out criteria at high altitude. Am J Emerg Med. 2020.

Examples

# Example 1: Negative Rule Out (High Altitude Context)
# 45yo, HR 90, O2 91% (Passes altitude cutoff), No other risks
altitude_adjusted_perc(45, 90, 91, 0, 0, 0, 0, 0)

# Example 2: Positive Rule Out (Fails O2)
# 45yo, HR 90, O2 88% (Fails even adjusted cutoff)
altitude_adjusted_perc(45, 90, 88, 0, 0, 0, 0, 0)

cliot documentation built on Dec. 1, 2025, 1:06 a.m.