Sniff test: Does what we measure at the nose reflect what happens in the chest wall?

The strength of respiratory muscles is measured in terms of pressure, being the gradient that moves flow/volume to ventilate the lungs. Sniff test is a technically simple voluntary test that quantifies the strength of inspiratory muscles. Sniff nasal inspiratory pressure (SNIP) is a non-invasive parameter extensively used in the clinical, being considered more natural and pleasant than maximal inspiratory pressure measurements. It solves the possible leak problems of the use of a mouthpiece, particularly in neuromuscular patients. In amyotrophic lateral sclerosis, for example, SNIP is a predictor of survival and tracheostomy.