/P/F Ratio (ARDS)

P/F Ratio (ARDS)

Assesses severity of hypoxia in ARDS

PaO2 (Arterial O2)
mmHg
FiO2 (Fraction of Inspired O2)
%

Total Score

0

Severe ARDS. Consider prone positioning, ECMO, or severe lung protective strategies.

301–999+Low
201–300+Moderate
101–200+High
0–100+High

Disclaimer: The clinical scoring and algorithms on this platform are intended strictly for professional informational purposes. They do not constitute a definitive medical diagnosis, treatment, or clinical decision. The final judgment and responsibility lie with the treating physician.

Yasal Uyarı: Bu platformdaki klinik skorlamalar ve algoritmalar yalnızca sağlık profesyonellerini bilgilendirme amaçlıdır. Herhangi bir kesin tıbbi teşhis, tedavi veya klinik karar yerine geçemez. Nihai karar ve sorumluluk hastayı yatak başında değerlendiren hekime aittir.

Clinical Overview

The PaO2/FiO2 (P/F) ratio is a cornerstone clinical indicator of hypoxemia and pulmonary gas exchange efficiency. According to the Berlin Definition, it is the primary physiological metric used to classify Acute Respiratory Distress Syndrome (ARDS) into mild (≤300), moderate (≤200), and severe (≤100 mmHg) categories, guiding advanced mechanical ventilation strategies.

Clinical Pearl

To fulfill the Berlin criteria for ARDS, the P/F ratio calculation MUST be performed while the patient is on a minimum Positive End-Expiratory Pressure (PEEP) or CPAP of 5 cmH2O. A P/F ratio drop solely due to atelectasis off PEEP does not strictly constitute ARDS.

Pitfalls & Warnings

  • Altitude significantly affects atmospheric PaO2; the ratio may need mathematical adjustment in high-altitude ICUs.
  • It assumes a linear relationship between PaO2 and FiO2, which breaks down clinically at very high or very low shunt fractions.

Academic References

ARDS Definition Task Force, Ranieri VM, Rubenfeld GD, et al. Acute respiratory distress syndrome: the Berlin Definition. JAMA. 2012;307(23):2526-2533.

Disclaimer: The clinical scoring and algorithms on this platform are intended strictly for professional informational purposes. They do not constitute a definitive medical diagnosis, treatment, or clinical decision. The final judgment and responsibility lie with the treating physician.