Respiratory Calculators

Calculates the alveolar-arterial oxygen gradient to assess for V/Q mismatch and diffusion defects.

Calculates peak expiratory flow rate as percentage of predicted to classify asthma severity.

Predicts 30-day mortality in community-acquired pneumonia. Simplified from the full Fine/PORT score.

Predicts mortality in COPD using BMI, airflow obstruction, dyspnoea, and exercise capacity.

Grades breathlessness severity to guide COPD management and pulmonary rehabilitation referral.

Distinguishes exudative from transudative pleural effusions using protein and LDH ratios.

Interprets spirometry FEV₁/FVC ratio to classify airflow obstruction severity per GOLD criteria.

Predicts 30-day mortality in acute PE to guide disposition (inpatient vs outpatient management). Validated in multiple large cohorts.

Simplified version of PESI using 6 binary variables to predict 30-day mortality after acute PE. Easier to calculate bedside than the original PESI.

11 clinical criteria to determine if a patient with acute PE is safe for outpatient (home) treatment. If ANY criterion is met, outpatient treatment is NOT recommended.

Stepwise algorithm combining 3 clinical items with D-dimer to exclude PE. Uses lower D-dimer threshold (500 μg/L) when ≥1 YEARS item present, higher threshold (1000 μg/L) when no YEARS items.

Estimates VTE risk in hospitalised medical patients to guide thromboprophylaxis decisions.

Screens for moderate-to-severe obstructive sleep apnoea (OSA) using 8 binary questions. Used pre-operatively and in outpatient settings.

Predicts the expected compensatory pCO₂ for a primary metabolic acidosis. A measured pCO₂ outside this range indicates a co-existing respiratory disorder.

Calculates the ratio of arterial oxygen tension to inspired oxygen fraction. Used to classify severity of hypoxaemic respiratory failure and diagnose ARDS per Berlin criteria.

Simplified pneumonia severity score not requiring urea measurement. Used in community and primary care settings to guide admission decisions in CAP.

Predicts need for intensive respiratory or vasopressor support (IRVS) in community-acquired pneumonia. Identifies patients who may require ICU-level care.

Predicts 3-month mortality in patients with pleural infection (empyema/complicated parapneumonic effusion) to guide management intensity. Validated in the MIST2 trial cohort.

Predicts risk of postoperative pulmonary complications (atelectasis, respiratory failure, pleural effusion, pneumonia, pneumothorax, bronchospasm) in non-cardiac surgery patients.

Calculates total arterial oxygen content — oxygen bound to haemoglobin plus dissolved in plasma. Used to assess oxygen delivery (DO₂ = CaO₂ × CO × 10).

Calculates the age-adjusted D-dimer threshold for excluding PE in patients over 50. Reduces unnecessary CTPA in elderly patients with low-to-moderate pre-test probability. Formula: age × 10 μg/L.

GOLD 2023 ABCD assessment tool for COPD combining symptom burden (CAT/mMRC) and exacerbation history to guide therapy.

2012 Berlin Definition of ARDS. Classifies severity by PaO₂/FiO₂ ratio with PEEP ≥ 5 cmH₂O.

8-item patient-reported outcome measure quantifying COPD symptom impact on daily life. Validated for GOLD ABCD grouping.

2017 Fleischner Society guidelines for management of incidentally discovered pulmonary nodules on CT in adults ≥ 35 years.

Estimates probability of malignancy in a solitary pulmonary nodule (SPN) using 6 independent predictors. Validated in multiple cohorts.

Stepwise interpretation of arterial blood gas. Identifies primary acid-base disorder and degree of compensation.

Pre-test probability score for pulmonary embolism. Guides decisions regarding D-dimer testing and CT pulmonary angiography (CTPA) in suspected PE.

Revised Geneva Score for pre-test probability of pulmonary embolism. Fully objective score using only clinical and laboratory variables — no physician gestalt required.

Risk stratification tool for intermediate-risk (haemodynamically stable) PE patients. Identifies those at risk of PE-related complications and death within 30 days.

Severity scoring for community-acquired pneumonia (CAP). Guides decision between outpatient, inpatient, and ICU care. British Thoracic Society standard score.

Predicts probability of deep vein thrombosis (DVT) in outpatients. An alternative to the Wells DVT score with similar performance.

Dyspnoea, Eosinopenia, Consolidation, Acidaemia, and Atrial Fibrillation (DECAF) score predicts in-hospital mortality in acute exacerbations of COPD.

BUN, altered mental status, pulse ≥109, age ≥65 (BAP-65) score predicts in-hospital mortality and need for mechanical ventilation in AECOPD.

Predicts 90-day mortality in viral pneumonia. Validated in influenza and non-influenza viral pneumonias. MuLBSTA = Multilobar infiltrates, Lymphopenia, Bacterial co-infection, Smoking, Tumour, Age.

Predicts 30-day serious adverse events (SAEs) in patients with AECOPD presenting to the emergency department. Score ≥1 associated with significantly increased SAE risk.

Predicts failure of high-flow nasal cannula (HFNC) in patients with acute hypoxaemic respiratory failure. ROX <3.85 at 12h predicts HFNC failure and need for intubation.

Predicts successful extubation in mechanically ventilated patients. RSBI = respiratory rate / tidal volume (L). Values <105 predict weaning success.

Gender, Age, Physiology (GAP) index predicts 1, 2, and 3-year mortality in idiopathic pulmonary fibrosis (IPF) using clinical and physiological variables.

Predicts 1-year mortality in IPF from a single clinical visit using age, hospitalisation history, %predicted FVC, and 24-week FVC change. du Bois risk score ranges 0–100.

Predicts survival in patients with malignant pleural effusion (MPE). Scores LDH, ECOG status, NLR, and tumour type (LENT) to guide management decisions.

Diagnoses ventilator-associated pneumonia (VAP) using clinical, radiological, and microbiological criteria. Score >6 suggests VAP.

Calculates static lung compliance (Cstat) in mechanically ventilated patients. Reduced compliance (<60 mL/cmH₂O) indicates stiff lungs (ARDS, pneumonia, pulmonary oedema).

Non-invasive surrogate for the PaO₂/FiO₂ ratio using pulse oximetry. Avoids arterial blood gas requirement. S/F ratio <315 correlates with ARDS (P/F <300).

Predicts malignancy probability in pulmonary nodules found on CT screening. Validated for nodules 6–30 mm. Used alongside Fleischner and BTS guidelines.

Drug Resistance in Pneumonia (DRIP) score identifies patients with community-acquired pneumonia at risk of drug-resistant pathogen infection (excluding MRSA/Pseudomonas HCAP criteria). Score ≥4 indicates high-risk.

Lung Injury Score (LIS) assesses severity of acute lung injury (ALI). Score ≥2.5 indicates severe ALI / ARDS. Used historically to assess ECMO candidacy.

Predicts difficult intubation in critically ill patients in the ICU. MACOCHA = Mallampati III or IV, Apnoea/OSA, reduced mobility of Cervical spine, Opening mouth, Coma, Hypoxaemia, non-Anaesthesiologist.

Heart rate, Acidosis, Consciousness, Oxygenation, and Respiratory rate (HACOR) score predicts the risk of non-invasive ventilation (NIV) failure and need for intubation in patients with acute respiratory failure. Assessed at 1-2 hours after NIV initiation. Score above 5 predicts NIV failure with 72% sensitivity and 89% specificity. Validated by Liu et al. 2017 in 449 patients.

Prognostic score for patients with malignant pleural effusion (MPE). Predicts 3-month mortality. Based on LENT score variables plus Performance status. Score 0-7: score 0-1 = low risk (median survival above 12 months); 2-4 = intermediate; 5-7 = high risk (median survival 2 months). Helps guide intervention choices (indwelling pleural catheter vs talc pleurodesis). From Bibby et al. 2018.

Severe Community-Acquired Pneumonia (SCAP) score for predicting adverse outcomes (need for ICU, mechanical ventilation, death) in hospitalised CAP patients. 8-variable score. High score predicts severe outcome. Validated by Espana et al. 2006. Can be used alongside PSI/PORT and CURB-65 for ICU triage.

Full PESI score predicts 30-day mortality in acute pulmonary embolism. Classifies patients into 5 risk classes (I-V) based on age, sex, cancer, heart failure, COPD, heart rate, systolic BP, respiratory rate, temperature, mental status, and O2 saturation. Risk Class I-II (very low/low) may be suitable for outpatient treatment with DOAC. Validated in 11,000+ patients. Note: simplified PESI (sPESI) also available in this app.

Novel 4-level clinical probability score for pulmonary embolism that includes age and directly classifies patients into unlikely/low/intermediate/high PE probability. Developed by Roy et al. 2021 as an improvement over Wells and revised Geneva scores in the age of D-dimer adjustment. Designed to reduce unnecessary CTPA ordering. Validated in 1,746 patients.

Lung Injury Prediction Score (LIPS) identifies patients at risk for developing Acute Lung Injury (ALI) / ARDS early in the hospital course (before ALI is established). Enables early preventive strategies (lung-protective ventilation, restrictive fluid strategy, avoidance of blood products). Validated by Gajic et al. 2011 in 5,584 patients. Score above 4 = high risk (ALI development rate 18% vs 3% for low risk).

Respiratory ECMO Survival Prediction (RESP) score. Predicts in-hospital survival for patients receiving veno-venous ECMO (VV-ECMO) for acute respiratory failure. Based on 12 pre-ECMO variables. Score -22 to +15; Class I (score above 5) = 92% survival; Class V (score below -5) = 18% survival. Developed by Schmidt et al. 2014 from the ELSO registry of 2,355 patients. Used to guide ECMO candidacy decisions.

Assesses risk of postoperative pulmonary complications (PPC) in adults undergoing surgery. Guides preoperative optimisation and perioperative respiratory monitoring.

2012 Berlin Definition of ARDS. Classifies ARDS severity (mild/moderate/severe) based on PaO₂/FiO₂ ratio while on PEEP ≥5 cmH₂O. Replaces the American-European Consensus Conference definition.

CRB-65 score assesses severity of community-acquired pneumonia (CAP) in primary care or ED settings (no blood tests required). Guides hospital admission decisions.

CURB-65 score predicts 30-day mortality in community-acquired pneumonia (CAP). Hospital-based version of CRB-65; requires blood urea measurement. Standard tool for CAP severity assessment.

Estimates probability of malignancy in incidental pulmonary nodules detected on CT. Based on the Pan-Canadian Early Detection of Lung Cancer Study. Guides surveillance and biopsy decisions.

Drug Resistance in Pneumonia (DRIP) score. Predicts risk of drug-resistant pneumonia pathogens to guide empirical antibiotic selection in CAP and HCAP patients.

Global Initiative for Obstructive Lung Disease (GOLD) 2023 COPD classification. Grades spirometric severity (GOLD 1–4) and ABCD group based on symptom burden (mMRC/CAT) and exacerbation history.

Predicts risk of postoperative pneumonia requiring antibiotics or respiratory support within 30 days of non-cardiac surgery. Developed from the American College of Surgeons NSQIP database.

Dutch-English LEMS Tumour Association Prediction (DELTA-P) Score. Predicts prognosis in superior vena cava (SVC) syndrome from lung malignancy and guides treatment decisions.

Predicts clinical outcome of pulmonary embolism (PE) in cancer patients. Guides management intensity (outpatient vs admission vs ICU) and anticoagulation decisions.

Calculates the predicted FEV1 based on age, sex, and height using GLI-2012 reference equations. Used to interpret spirometry and classify COPD/restriction severity.

Estimates predicted peak expiratory flow (PEF) based on sex, age, and height using Nunn-Gregg or ECCS reference equations. Used to assess asthma severity (% predicted PEF).

Modified Pulmonary Embolism Rule-out Criteria (PERC) adjusted for altitude. At high altitudes (>4000 ft/1220 m), physiological SpO₂ is lower, so the cut-off is adjusted from 95% to 90% to maintain specificity.

GINA (Global Initiative for Asthma) 2023 severity and control classification. Guides step-up/step-down of inhaled therapy from Step 1 (PRN SABA) to Step 5 (biologic therapy).

Predicts failure of high-flow nasal cannula (HFNC) oxygen therapy and need for intubation in acute hypoxaemic respiratory failure.

Predicts likelihood of non-invasive ventilation (NIV) failure in acute hypercapnic respiratory failure (AHRF) and COPD exacerbations.

Calculates oxygen delivery (DO2) to tissues from cardiac output, haemoglobin, and oxygen saturation. Normal DO2: 950-1150 mL/min.

Estimates risk of hypercapnic respiratory failure when administering supplemental oxygen in COPD patients. Guides target SpO2 selection (88-92%).

Non-invasive assessment of fluid responsiveness using respiratory variation in pulse oximetry plethysmographic waveform amplitude.

Estimates maximum voluntary ventilation and breathing reserve index from FEV1. Used in pre-operative respiratory assessment.

Calculates physiological dead space fraction using the Bohr-Enghoff equation. Elevated VD/VT (>0.6) predicts poor outcomes in ARDS.

Patient-completed 5-question test for asthma control over past 4 weeks. Score <=19 = not well controlled; score <=15 = very poorly controlled.

Selects appropriate SpO2 target range based on clinical condition. Prevents both hypoxia and oxygen toxicity (hyperoxia). Based on BTS Oxygen Guidelines.