RTLE flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Alveolar oxygen equation

PAO2 equals FiO2 times barometric pressure minus 47, minus PaCO2 divided by respiratory quotient, usually 0.8; it estimates alveolar oxygen before diffusion.

Oxygen content formula

Arterial oxygen content equals 1.34 times hemoglobin times arterial oxygen saturation plus 0.003 times PaO2; the first term is bound oxygen and the second dissolved oxygen.

V/Q mismatch extremes

A shunt has a ventilation-perfusion ratio of zero and does not improve much with supplemental oxygen; dead space has a ratio approaching infinity and wastes ventilation without gas exchange.

Surfactant function

Type II alveolar cells secrete surfactant, which lowers surface tension, increases compliance, and helps prevent alveolar collapse and edema at end expiration.

Oxyhemoglobin curve right shift

Increased carbon dioxide, hydrogen ion concentration, temperature, and 2,3-BPG shift the oxyhemoglobin curve right, reducing hemoglobin affinity and releasing more oxygen to tissues.

Cylinder duration formula

Duration in minutes equals gauge pressure in psi times the cylinder factor divided by gas flow in liters per minute; an E cylinder factor is about 0.28.

Air entrainment ratio

For a Venturi device, air-to-oxygen ratio equals 100 minus desired FiO2 divided by desired FiO2 minus 21; total flow equals oxygen flow times one plus that ratio.

Oropharyngeal airway contraindication

An oropharyngeal airway is avoided in a conscious or semiconscious patient with an intact gag reflex because it can trigger gagging, vomiting, and aspiration.

Endotracheal cuff pressure

Adult endotracheal tube cuff pressure is kept near 20 to 30 cm H2O to seal the airway while limiting pressure injury to the tracheal mucosa.

Capnography waveform phases

Phase I is anatomic dead space, phase II is mixing of dead space and alveolar gas, phase III is the alveolar plateau, and phase IV is the inspiratory downstroke.

Volume-control ventilation

Volume-control ventilation delivers a set tidal volume at a set rate; peak airway pressure and plateau pressure vary with compliance and resistance.

Ideal body weight male

For a male, ideal body weight in kilograms equals 50 plus 2.3 times height in inches minus 60; tidal volume is based on this value.

ARDS Berlin definition

ARDS is acute onset hypoxemia with PaO2/FiO2 of 300 or less on PEEP of at least 5 cm H2O, bilateral opacities, and respiratory failure not fully explained by cardiac failure.

Auto-PEEP cause

Auto-PEEP occurs when expiration is incomplete, trapping gas and raising end-expiratory alveolar pressure; it can cause hypotension and barotrauma and is reduced by lengthening expiratory time.

Rapid shallow breathing index

The rapid shallow breathing index equals respiratory rate divided by tidal volume in liters; a value below 105 predicts a higher likelihood of successful weaning from mechanical ventilation.

Pulsus paradoxus

Pulsus paradoxus is an inspiratory fall in systolic blood pressure greater than 10 mm Hg, classically seen in severe asthma, COPD, and cardiac tamponade.

Mean arterial pressure

Mean arterial pressure is approximately diastolic pressure plus one third of the pulse pressure, or systolic pressure plus twice diastolic pressure divided by three.

Glasgow Coma Scale range

The Glasgow Coma Scale sums eye, verbal, and motor responses for a score of 3 to 15; a lower score indicates a lower level of consciousness.

Sudden ETCO2 drop

A sudden fall in end-tidal carbon dioxide may indicate tube disconnection, extubation, esophageal intubation, cardiac arrest, or pulmonary embolism and requires immediate assessment.

Normal arterial blood gas

Normal adult arterial values are pH 7.35 to 7.45, PaCO2 35 to 45 mm Hg, bicarbonate 22 to 26 mEq/L, and PaO2 80 to 100 mm Hg.

Anion gap formula

The serum anion gap equals sodium minus the sum of chloride and bicarbonate; a normal value is about 8 to 12 mEq/L, and elevation suggests organic acidosis.

Obstructive spirometry pattern

Obstruction shows a reduced FEV1/FVC ratio below 0.70, reduced FEV1, and often increased residual volume and total lung capacity from air trapping.

Bronchodilator response

A positive bronchodilator response is an increase in FEV1 or FVC of at least 12 percent and at least 200 mL from prebronchodilator values.

Apnea-hypopnea index

The apnea-hypopnea index is the number of apneas plus hypopneas per hour of sleep; 5 to 15 is mild, 15 to 30 is moderate, and above 30 is severe.

Beta2 agonist action

Beta2 agonists such as albuterol stimulate beta2 receptors, raise cyclic AMP, and relax bronchial smooth muscle; adverse effects include tachycardia, tremor, and hypokalemia.

Inhaled corticosteroid precaution

After inhaled corticosteroid use, rinsing the mouth and spitting reduces oropharyngeal candidiasis and dysphonia caused by local drug deposition.

Aerosol particle size

Aerosol particles of about 1 to 5 micrometers deposit most effectively in the lower respiratory tract; larger particles impact in the upper airway.

Theophylline therapeutic range

Theophylline has a narrow therapeutic serum range of about 5 to 15 micrograms per milliliter; toxicity can cause arrhythmias, seizures, and persistent vomiting.

Neonatal normal respiratory rate

A normal newborn respiratory rate is about 30 to 60 breaths per minute; sustained rates above 60 with retractions or grunting suggest respiratory distress.

Apgar score components

The Apgar score assesses appearance, pulse, grimace, activity, and respiration at 1 and 5 minutes; each component scores 0 to 2 for a total of 10.

Neonatal chest compression ratio

In neonatal resuscitation, chest compressions are given at a ratio of 3 compressions to 1 breath when the heart rate remains below 60 per minute after effective ventilation.

Pediatric uncuffed tube size

For a child older than 1 year, uncuffed endotracheal tube internal diameter in millimeters equals age in years divided by 4 plus 4.