CRT (IJCAHPO) cheat sheet

Normal adult resting values: respiratory rate 12-20/min, tidal volume 6-8 mL/kg ideal body weight, spontaneous minute ventilation ~5-6 L/min.

Ideal body weight (male) = 50 + 2.3 × (height in inches − 60); (female) = 45.5 + 2.3 × (height in inches − 60).

Static lung compliance = tidal volume ÷ (plateau pressure − PEEP); normal ~60-100 mL/cm H2O in ventilated adults.

Airway resistance = (peak pressure − plateau pressure) ÷ inspiratory flow; a gradient >10 cm H2O suggests increased resistive load.

A-a gradient = PAO2 − PaO2, where PAO2 = FiO2 × (PB − 47) − (PaCO2 ÷ 0.8); normal on room air is roughly 5-15 mm Hg.

Oxygen content CaO2 = (1.34 × Hb × SaO2) + (0.003 × PaO2); hemoglobin-bound oxygen dominates total content.

Oxygen delivery DO2 = cardiac output × CaO2 × 10; oxygen consumption VO2 = CO × (CaO2 − CvO2) × 10.

Bohr effect: increased PaCO2, decreased pH, and increased temperature shift the oxyhemoglobin curve right, reducing affinity.

Heliox lowers gas density and reduces turbulent flow; it is most useful in large-airway obstruction, not small-airway disease.

Aerosol output of a small-volume nebulizer depends on flow and fill volume; 6-8 L/min with 3-5 mL is typical for adult treatments.

MDI with valved holding chamber improves lung deposition and reduces oropharyngeal impaction versus an MDI alone.

Cuff pressure target is 20-30 cm H2O; higher pressures risk tracheal ischemia, lower pressures risk aspiration and leak.

Endotracheal tube depth at the incisors averages ~21 cm in adult women and ~23 cm in adult men; verify with chest radiograph.

High-efficiency particulate air filtration removes ≥99.97% of particles ≥0.3 µm; standard surgical masks do not.

Hand hygiene with alcohol-based rub is preferred when hands are not visibly soiled; soap and water is required for C. difficile spores.

Closed-suction systems preserve PEEP and reduce environmental contamination compared with open suctioning.

Lung-protective ventilation in ARDS: tidal volume 4-6 mL/kg predicted body weight, plateau pressure ≤30 cm H2O.

Permissive hypercapnia is accepted in ARDS as long as pH remains roughly ≥7.20-7.25 and the patient is hemodynamically stable.

Auto-PEEP is reduced by lengthening expiratory time, treating bronchospasm, and reducing minute ventilation.

Volume-control delivers a set tidal volume at variable pressure; pressure-control delivers a set pressure at variable volume.

Pressure support ventilation augments spontaneous breaths; it does not guarantee a minimum minute ventilation.

PEEP improves oxygenation by recruiting alveoli and preventing end-expiratory collapse, but can reduce venous return.

Weaning readiness indicators include RSBI <105 breaths/min/L, spontaneous tidal volume >5 mL/kg, and adequate cough.

Aerosol drug delivery during mechanical ventilation is maximized with a dry circuit, adequate inspiratory time, and a chamber placed near the airway.

Asthma exacerbation: short-acting beta-2 agonist is first-line; ipratropium is added in severe exacerbations.

COPD exacerbation: controlled low-flow oxygen targeting SpO2 roughly 88-92% in at-risk retainers, plus bronchodilators and corticosteroids.

Status asthmaticus unresponsive to bronchodilators may require magnesium sulfate, heliox, or noninvasive ventilation.

Croup presents with a barking cough and inspiratory stridor; nebulized epinephrine and dexamethasone are standard.

Epiglottitis causes drooling, tripod positioning, and muffled voice; avoid agitating the patient and secure the airway in a controlled setting.

Acute respiratory distress syndrome uses the Berlin definition: onset within 1 week, bilateral opacities, and PaO2/FiO2 ≤300 with PEEP ≥5.

Pulmonary embolism often produces sudden dyspnea with hypoxemia out of proportion to exam findings; D-dimer and CT angiography guide diagnosis.

Flail chest with pulmonary contusion is managed with analgesia, pulmonary hygiene, and ventilatory support rather than fluid loading.