Page 748 - Clinical Application of Mechanical Ventilation

714 Glossary

opioid analgesics: Drugs that are used to control pain via the central nervous system. Examples are morphine, codeine,
and meperidine (Demerol, a synthetic compound).
optimal PEEP: The lowest PEEP level leading to the best oxygenation status (or other indicators) without causing
significant cardiopulmonary complications.
oronasal mask: A mask that covers the nose and mouth. It is used in noninvasive positive pressure ventilation.
oropharyngeal airway: A device to relieve upper airway obstruction.
oxygen delivery: Total amount of oxygen carried by blood. It is the product of O content and cardiac output.
2
oxygenation: Amount of oxygen available for metabolic functions; affected by ventilation, diffusion, and perfusion.
oxygenation failure: Failure of the heart and lungs to provide adequate oxygen for metabolic needs.
P/F ratio: PaO /F O . Clinical assessment of oxygenation and degree of hypoxemia, ≤300 mm Hg for ALI, ≤200 mm Hg
2 I
2
for ARDS.
pandemic: An occurrence of infectious disease that is spreading through human populations across a large region,
continent, or world.
parasympatholytic bronchodilators: Anticholinergic bronchodilators. Drugs that dilate the airways by inhibiting
the parasympathetic branch of the autonomic nervous system. Examples are atropine and ipratropium bromide
(Atrovent).
peak alveolar pressure (P ALV ): Pressure obtained by performing an end-inspiratory pause, also called plateau pressure.
peak inspiratory pressure (PIP): Maximum pressure measured during one respiratory cycle, usually at end-inspiration.
permissive hypercapnia: Intentional hypoventilation of a patient by reducing the ventilator tidal volume to a range
of 4 –7 mL/kg (normally 10mL/kg). It is used to lower the pulmonary pressures and to minimize the risk of
ventilator-related lung injuries. The patient’s PaCO is significantly elevated and the resulting acidotic pH is
2
neutralized by bicarbonate or tromethamine.
physiologic deadspace: Sum of anatomic and alveolar deadspace. Under normal conditions, it is about the same as
anatomic deadspace.
pilot balloon: The small balloon on the proximal end of an endotracheal or tracheostomy tube. It is used to regulate
the volume of air in the cuff and to serve as an indicator of air volume in the cuff.
plateau pressure (P PLAT ): Pressure obtained by performing an end-inspiratory pause, also called peak alveolar pressure.
pneumatic drive mechanism: Operation of a ventilator with pressurized gas as a power source.
positive end-expiratory pressure (PEEP): PEEP is an airway pressure strategy in ventilation that increases the end-
expiratory or baseline airway pressure to a value greater than atmospheric pressure. It is used to treat refractory
hypoxemia caused by intrapulmonary shunting.
positive pressure ventilation: Mechanical ventilation in which the volume is delivered by a positive pressure gradient
(i.e., airway pressure higher than alveolar pressure).
power: A setting during HFOV that determines the amplitude of oscillation, tidal volume, and degree of ventilation.
preload: The end-diastolic stretch of the muscle fiber.
pressure compensation: A ventilator feature that makes self-adjustment of pressure or volume output based on
changing atmospheric pressure.
pressure support ventilation (PSV): A mode of ventilation in which the patient’s spontaneous tidal volume is
augmented by the application of a preset pressure plateau to the patient’s airway during the inspiratory phase of a
spontaneous breath.
pressure-controlled ventilation (PCV): Mode of ventilation in which a preset peak inspiratory pressure is used to provide
ventilation. The delivered volume during this mode of ventilation is affected by the changing compliance and
resistance.

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