Residual Volume (RV)
Is the amount of air that can't be blown out after forceful exhalation. In obstructive diseases, as emphysema and asthma, this value may increase due to air trapped in the lung behind blocked airways. That is when the exchange of oxygen and carbon dioxide is hampered.

 S

Sequelea
Pathological consequences (objective, observable symptomology) of a medical condition.

Sepsis
The state of being infected with pus–producing organisms, usually used to refer to a major systemic or system–wide infection; a systeminc inflammatory response to infection; clinically manifested by two or more of the following conditions: (1) temperature >38fC or <36fC; (2) heart rate >90 beats/minute; (3) respiratory rate >20 breaths/min or PaCO₂<<32 mm HG; and (4) WBC count >12,000/mm3 or <4,000/mm3some, or >10% immature (band) forms.

Severe sepsis is sepsis associated with organ dysfunction, hypoperfusion, or hypotension, the latter two may include lactic acidosis, oliguria, or an acute alteration in mental state.

Septic shock is a subset of severe sepsis and defined as sepsis-induced hypotension despite adequate fluid resuscitation along with the presence of perfusion abnormalities that may include, but are not limited to, lactic acidosis, oliguria, or an acute alteration in mental status.

Septicemia
The persistence and multiplication of living bacteria in the blood stream (sometimes called blood infection, blood–borne infection).

Shunt
To bypass or divert.

Spirometer
An instrument for measuring the capacity of the lungs.

Stent
Small plastic or steel tube inserted to keep a valve or other aspect of the body open to Permit and allow drainage.

Steriods
See corticosteroids.

Stoma – the mouth, or any opening (see fenestra, fenestration, tracheostomy)

Subcutaneous
Below the skin.

Surface-active
The property of certain chemicals of altering the physiochemical nature of the surfaces to reduce the surface tension. Surface active agents (e.g. detergents) typically contain lipophilic and hydrophilic groups.

Surfactant
An important surface–agent in the lungs; a term used to describe those agents forming a monomolecular layer over pulmonary alveolar surfaces to stabilize the alveolar volume, reduce the surface tension, and alter the relationship between surface tension and surface area. for further information; see What–Is–Surfactant? in the What–Is section.

Supine
Face upwards.