Page 742 - Clinical Application of Mechanical Ventilation

Glossary

acetylcholine: An ester that plays a role in the transmission of nerve impulses at synapses and neuromuscular junctions.
It is metabolized by an enzyme, cholinesterase. Too much or too little acetylcholine at the motor endplates may
lead to muscle blockade.
acute lung injury: A condition of sudden onset, characterized by non-cardiogenic pulmonary edema on chest
radiograph and a PaO /F O of ≤ 300 mm Hg.
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acute respiratory distress syndrome: A condition of sudden onset, characterized by non-cardiogenic pulmonary edema
on chest radiograph and a PaO /F O of ≤ 200 mm Hg.
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acute ventilatory failure: An increase of PaCO (.50 mm Hg) with a concurrent decrease of arterial (pH ,7.30).
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adaptive pressure control: A mode of pressure-controlled breath that utilizes closed-loop control of the pressure setting
to maintain a minimum delivered tidal volume.
adaptive support ventilation (ASV): A mode of ventilation that changes the number of mandatory breaths and pressure
support level according to the patient’s breathing pattern.
afterload: The resistance of the blood vessels into which the ventricle is pumping blood.
airway resistance: The degree of airflow obstruction in the airways.
airway opening pressure (P AO ): Sum of transairway pressure (P ) and alveolar pressure (P ALV ).
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airway pressure release ventilation (APRV): A mode of ventilation in which the spontaneous breaths are at an elevated
baseline (i.e., CPAP). This elevated baseline is periodically “released” to facilitate expiration.
alarm: An absolute value of a parameter on the ventilator beyond which an alert is invoked to warn that the safety
limit has been breached.
alveolar deadspace: The normal lung volume that has become unable to take part in gas exchange because of
reduction or lack of pulmonary perfusion (e.g., pulmonary embolism).
alveolar pressure (P ALV ): Pressure required to overcome the elastic recoil property of the lungs.
alveolar volume: The portion of tidal volume that takes part in gas exchange.
alveolar-arterial oxygen pressure gradient [P (A-a) O 2 ]: The difference of P O and PaO . A gradient over 450 mm Hg
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while on 100% oxygen indicates severe hypoxemia or intrapulmonary shunting.
anatomic deadspace: The volume occupying the conducting airways that does not take part in gas exchange
(estimated to be 1 mL/lb ideal body weight).
anion gap: The difference between cations (positive ions) and anions (negative ions) in the plasma. The normal range
is 15–20 mEq/L when K is included in the calculation (10 to 14 mEq/L when K is excluded).
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antiemetic: Preventing nausea and vomiting.
anxiolysis: Diminishing anxiety.
apnea index: Average number of apneas in each hour of sleep during a test.
apnea-hypopnea index: Average number of apnea and hypopnea in each hour of sleep during a test.

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