physiology

Breathing Patterns

A patient’s breathing pattern can help guide response to therapies and diagnostics. Normal breathing is regular and comfortable at a rate of 12-20 breaths per minute (bpm). Tachypnea and bradypnea have rates above and below...

Left Atrial And Ventricular Pressure Throughout The Stages Of Diastole

The left ventricle’s (LV) variously arranged muscle fibers twist and contract during systole, storing potential energy as blood is ejected (imagine wringing water out of a towel). This stored energy is released in diastole:...

Hypernatremia And Free Water Deficit

Sodium (Na) fluctuations portend increased in-hospital death for ICU patients, and when working them up, it's essential to determine if these disorders are acute or chronic (> 48 hours or unknown duration). For hypernatremia...

West’s Lung Zones

Alveoli that are well ventilated (V) should be associated with good pulmonary capillary blood perfusion (Q) to maximize gas exchange. This is the idea behind V/Q matching. Gravitational forces create heterogeneity perfusing dependent portions...

Cardiac Action Potential

In order for the heart muscle to actually contract, the physiological process of excitation-contraction coupling must occur via an action potential propagated through the myocardium. Normally, these muscle cells have a resting transmembrane potential...

Antibody Structure

With all the discussion surrounding antibody production after receiving a COVID-19 vaccine, let’s talk about the structure of an antibody. An antibody (immunoglobulin, or Ig) is a protein synthesized by plasma B cells targeting unique...

What’s A P/F Ratio?

The P/F ratio is a simple way to assess the severity of hypoxemia. It's the ratio of the PaO2 (arterial oxygen partial pressure obtained from an arterial blood gas) to the FiO2 (fraction of...

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch (H-H) equation illustrates the incredibly important role of the bicarbonate buffer system comprised of the partial pressure of carbon dioxide (PaCO2, primarily regulated by the lungs) and bicarbonate (HCO3-, primarily regulated by...

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