Breathing Rate & Pattern Calculator
Calculate breathing rate, minute ventilation, inspiratory-to-expiratory ratio, and identify breathing patterns (normal, tachypnea, bradypnea, Kussmaul, Cheyne-Stokes indicators).
Formulas Used
1. Breathing Rate (RR):
RR (breaths/min) = (Breaths Counted ÷ Observation Time in seconds) × 60
2. Breath Cycle Time:
Tcycle (s) = 60 ÷ RR
3. Minute Ventilation (MV):
MV (L/min) = RR × VT (L)
where VT = tidal volume in litres
4. Alveolar Ventilation (V̇A):
V̇A (L/min) = (VT − VD) × RR
where VD = anatomical dead space (estimated: ~150 mL adult, scaled by age group)
5. I:E Ratio:
I:E = TI : TE (normalised to 1 : TE/TI)
Normal physiological range: 1:1.5 to 1:2
6. Pattern Classification thresholds (adults):
Eupnea: 12–20 breaths/min | Tachypnea: >20 | Severe Tachypnea: >30 | Bradypnea: <12
Assumptions & References
- Normal adult RR: 12–20 breaths/min (Tortora & Derrickson, Principles of Anatomy and Physiology, 15th ed.).
- Paediatric normal ranges from: Fleming S et al. (2011). Normal ranges of heart rate and respiratory rate in children from birth to 18 years. The Lancet, 377(9770), 1011–1018.
- Anatomical dead space estimated at ~2.2 mL/kg or approximately 150 mL for a 70 kg adult (West, Respiratory Physiology, 10th ed.).
- Normal I:E ratio at rest is approximately 1:1.5 to 1:2; prolonged expiration (>1:2.5) suggests obstructive disease (GOLD guidelines, 2023).
- Kussmaul breathing: deep, rapid respirations associated with metabolic acidosis (Kussmaul A, 1874).
- Cheyne-Stokes respiration: cyclical crescendo-decrescendo pattern; heuristic flags here are indicative only and require clinical observation.
- Minute ventilation normal range at rest: ~5–8 L/min for adults.
- This calculator does not account for altitude, body position, sleep state, or underlying pathology.
- Not a substitute for clinical assessment, pulse oximetry, capnography, or arterial blood gas analysis.