Work of Breathing
Adequate minute ventilation (minute ventilation = TV x RR) is necessary for maintaining oxygenation and CO2 excretion.
In order to reduce energy consumption and fatigue, the TV and RR are optimized by the respiratory control centers to minimize the work of breathing while maintaining adequate minute ventilation.
2 types of resistances to consider:
The work done against the elastic resistance of the lung is increased when the tidal volume is increased, while the work done against airflow resistance is increased when the breathing frequency is increased.
For patients with stiff lungs (increased elastic resistance), the work of breathing is minimized when the RR is high and the TV is low.
Therefore, rapid and shallow breaths are favored
In contrast, in situations with high airflow resistance, patients tend to breath at a lower rate (slow, deep breaths) in order to minimize the work of breathing.
The haemoglobin–oxygen (Hb–O₂) dissociation curve is one of those core physiology concepts that keeps showing up in MRCP, PassMedicine, and real‑life clinical reasoning. Let’s expand it properly — mechanism‑based, clinically anchored, and exam‑ready, the way you prefer.
The Hb–O₂ dissociation curve is sigmoidal because of cooperative binding.
Right shift = Hb gives up O₂ more easily.
Left shift = Hb holds onto O₂ more tightly.