- Respiratory acidosis
- Low pH (< 7.35) with a high PaCO2 (> 45 mm Hg) from hypoventilation (COPD, sedation, neuromuscular weakness).
- Respiratory alkalosis
- High pH (> 7.45) with a low PaCO2 (< 35 mm Hg) from hyperventilation (anxiety, pain, PE, hypoxia).
- Metabolic acidosis
- Low pH (< 7.35) with a low HCO3 (< 22 mEq/L) — DKA, lactic acidosis, renal failure, diarrhea.
- Metabolic alkalosis
- High pH (> 7.45) with a high HCO3 (> 26 mEq/L) — vomiting, diuretics, NG suction.
- Normal ABG values
- pH 7.35–7.45 · PaCO2 35–45 mm Hg · HCO3 22–26 mEq/L · PaO2 80–100 mm Hg · SaO2 95–100%.
- ABG interpretation order
- 1) pH (acidemia/alkalemia) → 2) PaCO2 vs HCO3 to find the cause → 3) assess compensation. The value moving with the pH is the primary cause.
- Fully compensated acid–base
- The pH is back in the normal range while PaCO2 and HCO3 both stay abnormal — e.g., chronic respiratory acidosis in COPD with renal retention of HCO3.
- P/F ratio
- PaO2 ÷ FiO2 (as a decimal). Berlin ARDS: 200–300 mild, 100–200 moderate, ≤ 100 severe (with PEEP ≥ 5).
- P/F ratio example (80 on 0.80)
- 80 ÷ 0.80 = 100 → severe ARDS. (90 ÷ 0.60 = 150 → moderate; 250 ÷ 0.50 = 500 → normal.)
- A–a gradient
- Alveolar PO2 minus arterial PaO2. A widened gradient = a gas-exchange problem (V/Q mismatch, shunt, diffusion), not simple hypoventilation.
- Minute ventilation
- Respiratory rate × tidal volume. Example: 12 × 500 mL = 6,000 mL = 6 L/min.
- Alveolar ventilation
- (Tidal volume − dead space) × rate. Example: (600 − 150) × 10 = 4,500 mL = 4.5 L/min — only gas reaching the alveoli.
- Carboxyhemoglobin
- Hemoglobin bound to carbon monoxide; cannot carry O2. Pulse ox reads falsely normal — detect with CO-oximetry. Treat with 100% O2.
- Methemoglobin
- Hemoglobin with iron in the ferric (Fe3+) state; cannot bind O2. Causes cyanosis with SpO2 stuck near 85%; detected by CO-oximetry.
- Capnography after intubation
- A normal square waveform with end-tidal CO2 ~35–45 mm Hg confirms the tube is in the trachea, not the esophagus.
- End-tidal CO2 rise during CPR
- A sudden rise in end-tidal CO2 signals return of spontaneous circulation as pulmonary blood flow is restored.
- FEV1/FVC ratio
- Fraction of FVC exhaled in the first second. Below ~0.70 = obstructive (asthma, COPD). Normal/high with low volumes = restrictive.
- Rapid shallow breathing index (RSBI)
- Rate ÷ tidal volume in liters. Below ~105 predicts weaning success; above 105 predicts failure (e.g., 32 ÷ 0.3 ≈ 107).
- Maximum inspiratory pressure (MIP)
- Inspiratory muscle strength, measured against an occluded airway. More negative than ~ −20 to −30 cm H2O favors weaning; −15 is inadequate.
- Peak vs plateau pressure
- Peak reflects airway resistance + compliance; plateau (inspiratory hold, no flow) reflects compliance only. The gap = airway resistance.
- Auto-PEEP
- Trapped gas from incomplete exhalation (COPD/asthma, high rate). Found with an expiratory-hold; managed by lengthening expiratory time.
- Low-flow oxygen device
- Nasal cannula, simple mask, nonrebreather — supplies less than total inspiratory demand, so FiO2 varies with the breathing pattern.
- High-flow oxygen device
- Air-entrainment (Venturi) mask, high-flow nasal cannula — total flow meets/exceeds demand, giving a fixed, predictable FiO2.
- Nasal cannula FiO2
- Low-flow; roughly 24–44% at 1–6 L/min (about 4% FiO2 per liter), varying with the patient's breathing pattern.
- Nonrebreather mask
- Reservoir bag + one-way valves; ~60–80% O2 at 10–15 L/min. Keep the bag from fully collapsing — raise the flow if it does.
- Air-entrainment (Venturi) mask
- High-flow device that delivers a precise FiO2 (24–50%) set by the jet size and entrainment ports, regardless of breathing pattern.
- Ventilator high-pressure alarm
- Obstruction or stiffness: secretions/mucus plug, kinked or bitten tube, bronchospasm, falling compliance, pneumothorax, coughing.
- Ventilator low-pressure alarm
- Leak or disconnection: circuit disconnect, underinflated ET cuff, loose connection, ruptured cuff or chest-tube leak.
- Oxygen analyzer calibration
- Two-point calibration: expose the sensor to room air (21%) and to 100% O2. A galvanic cell reading low on room air signals a depleted fuel cell.
- Levey-Jennings chart
- Plots blood-gas control results over time to detect trends and shifts (e.g., six points on one side of the mean = a systematic shift).
- Westgard rules
- Multirule QC system that distinguishes random from systematic error and decides whether to accept or reject a run. A result > 3 SD (1-3s rule) rejects the run.
- Spaulding classification
- Critical → sterilize; semicritical (mucous membranes) → high-level disinfection; noncritical (intact skin) → low/intermediate disinfection.
- Reusable laryngoscope blade
- Contacts oral mucosa → semicritical under Spaulding → requires high-level disinfection between patients.
- Airborne precautions
- Negative-pressure room + fit-tested N95 for small droplet nuclei: tuberculosis, measles, varicella.
- Droplet vs contact precautions
- Droplet (surgical mask): influenza, pertussis. Contact (gown/gloves): MRSA, C. difficile.
- ET tube cuff pressure
- Keep 20–30 cm H2O — seals the airway without exceeding tracheal capillary pressure. Above 30 risks mucosal ischemia (remove air).
- Extubation readiness
- Intact gag and cough (airway protection) with the underlying cause of failure resolved — not just good vitals or numbers.
- Cuff-leak test
- No leak when the cuff is deflated suggests laryngeal edema and a risk of post-extubation stridor; treat with racemic epinephrine.
- Blocked tracheostomy
- New trach + sudden dyspnea + can't pass a suction catheter → remove the inner cannula first to check for a mucus plug.
- Assist-control (A/C) ventilation
- Every breath — patient- or machine-triggered — is delivered at the full set tidal volume or pressure; the most support, rests the muscles.
- SIMV
- Synchronized mandatory breaths plus the patient's own spontaneous breaths in between (often with pressure support); used for weaning.
- Pressure support ventilation (PSV)
- Augments each spontaneous breath with a set inspiratory pressure and cycles to expiration when inspiratory flow falls.
- ARDSnet lung-protective ventilation
- Low tidal volume ~6 mL/kg of ideal body weight with plateau pressure < 30 cm H2O to limit volutrauma and barotrauma.
- Lung-protective tidal volume (70 kg IBW)
- 70 kg × 6 mL/kg = 420 mL — start ARDS ventilation near this volume, set by ideal body weight, not actual weight.
- Permissive hypercapnia
- Deliberately tolerating an elevated PaCO2 to protect the lung with low tidal volumes, as long as the pH stays within the protocol limit.
- Albuterol
- Short-acting beta-2 agonist; rapidly relaxes bronchial smooth muscle — first-line for acute bronchospasm (asthma, COPD).
- Ipratropium
- Short-acting anticholinergic bronchodilator that blocks muscarinic receptors; slower onset, often combined with albuterol.
- Racemic epinephrine
- Reduces upper-airway swelling by mucosal vasoconstriction — used for croup and post-extubation stridor.
- Dornase alfa
- Mucolytic (DNase) that thins the sticky DNA-rich sputum of cystic fibrosis, improving airway clearance.
- Postural drainage
- Positions the affected lung segment uppermost so gravity drains secretions toward the larger central airways for clearance.
- Incentive spirometry vs IPPB
- Incentive spirometry: alert, cooperative patient takes slow deep breaths. IPPB: for patients who can't take an adequate deep breath on their own.
- Long-term oxygen therapy threshold
- Indicated for a resting room-air PaO2 ≤ 55 mm Hg (or SaO2 ≤ 88%), or ≤ 59 mm Hg with cor pulmonale, edema, or hematocrit > 55%.
- Tidal volume (VT)
- Volume of gas moved in one normal breath, ~5–8 mL/kg ideal body weight (about 500 mL in an adult). Set near 6 mL/kg IBW in lung-protective ventilation.
- Vital capacity (VC)
- Maximum volume exhaled after a maximal inspiration (IRV + VT + ERV). Normal ~65–75 mL/kg; below ~10–15 mL/kg signals inadequate ventilatory reserve.
- Functional residual capacity (FRC)
- Volume remaining in the lungs after a normal exhalation (ERV + RV). PEEP and CPAP raise FRC; it falls in restrictive disease, ARDS, and obesity.
- Residual volume (RV)
- Gas remaining after a maximal exhalation; cannot be measured by simple spirometry (needs body plethysmography or gas dilution). Increased in air trapping/COPD.
- Total lung capacity (TLC)
- Total volume after a maximal inspiration (~6 L). Decreased in restrictive disease; increased with hyperinflation in obstructive disease.
- Anatomic dead space
- Conducting airways that hold gas but do no gas exchange, ~1 mL/lb of ideal body weight (~150 mL). Part of each breath that never reaches the alveoli.
- Alveolar dead space
- Alveoli that are ventilated but not perfused (e.g., pulmonary embolism). Combined with anatomic dead space gives physiologic dead space.
- Static lung compliance
- Volume change per unit pressure change, VT ÷ (plateau pressure − PEEP). Normal ~60–100 mL/cm H2O; low in ARDS, pneumonia, pulmonary edema.
- Airway resistance (Raw)
- Opposition to airflow, (peak − plateau pressure) ÷ flow. Rises with bronchospasm, secretions, kinked or small-bore ET tubes.
- Oxyhemoglobin dissociation curve
- Sigmoid relationship of SaO2 to PaO2; a PaO2 of 60 corresponds to ~90% saturation (the steep upper-shoulder reference point).
- Right shift of oxyhemoglobin curve
- Lower Hb-O2 affinity (unloads O2 to tissues) from acidosis, hypercapnia, fever, and increased 2,3-DPG. Mnemonic: "CADET, face Right."
- Left shift of oxyhemoglobin curve
- Higher Hb-O2 affinity (holds O2) from alkalosis, hypocapnia, hypothermia, low 2,3-DPG, carboxyhemoglobin, and fetal hemoglobin.
- Hypoxemia
- Low arterial oxygen: mild PaO2 60–79, moderate 40–59, severe < 40 mm Hg on room air. Distinct from hypoxia (low tissue O2 delivery).
- Refractory hypoxemia
- Hypoxemia that does not correct with increasing FiO2, indicating a large intrapulmonary shunt (ARDS); treated by recruiting alveoli with PEEP.
- Intrapulmonary shunt
- Blood passing perfused but unventilated alveoli (atelectasis, ARDS, pneumonia). Causes hypoxemia poorly responsive to oxygen; corrected with PEEP/recruitment.
- V/Q mismatch
- Imbalance of ventilation to perfusion; the most common cause of hypoxemia. Low V/Q = shunt-like; high V/Q = dead-space-like. Usually responds to oxygen.
- Anion gap
- Na − (Cl + HCO3); normal 8–12 mEq/L. A high gap metabolic acidosis points to lactic acidosis, ketoacidosis, renal failure, or toxins.
- Base excess/deficit
- Metabolic component of acid–base balance; normal ±2 mEq/L. A negative value (base deficit) indicates metabolic acidosis; positive indicates metabolic alkalosis.
- Mixed venous oxygen saturation (SvO2)
- O2 saturation of pulmonary artery blood (normal ~60–80%). A fall reflects worsening delivery or rising consumption (shock, anemia, hypoxemia).
- Oxygen content (CaO2)
- (1.34 × Hb × SaO2) + (0.003 × PaO2). Hemoglobin-bound O2 dominates, so anemia drops content even when PaO2 and SaO2 look normal.
- DLCO
- Diffusing capacity for carbon monoxide; reflects the alveolar-capillary membrane. Low in emphysema, fibrosis, anemia; high in alveolar hemorrhage and polycythemia.
- Flow-volume loop
- Plots flow against volume in one cycle. A scooped expiratory limb = obstruction; flattened inspiratory/expiratory limbs = fixed upper-airway obstruction.
- Bronchodilator response (PFT)
- An increase in FEV1 of ≥ 12% and ≥ 200 mL after a bronchodilator indicates significant reversibility, characteristic of asthma.
- Peak expiratory flow rate (PEFR)
- Maximum flow during a forced exhalation; tracks asthma control. A drop from the patient's personal best signals worsening obstruction.
- Methacholine challenge test
- Provocation test for suspected asthma; a ≥ 20% fall in FEV1 at a low dose confirms airway hyperresponsiveness. Have a bronchodilator ready.
- Six-minute walk test
- Measures distance walked and desaturation over 6 minutes to assess functional capacity and titrate oxygen in COPD and pulmonary hypertension.
- Chest radiograph: ET tube position
- The tip should sit 2–6 cm above the carina (~at the aortic knob, T4–T5). Too low = right mainstem intubation; pull back.
- Right mainstem intubation signs
- Diminished/absent left breath sounds, asymmetric chest rise, hypoxemia, and a tube tip past the carina on x-ray. Withdraw the tube.
- Pneumothorax on chest film
- Absent lung markings peripherally with a visible visceral pleural line; tension pneumothorax adds mediastinal shift away and a depressed hemidiaphragm.
- Air bronchograms
- Air-filled bronchi outlined by surrounding alveolar opacity, indicating consolidation such as pneumonia or ARDS.
- Silhouette sign
- Loss of a normal border on a chest film localizes a lesion; e.g., a lost right heart border places consolidation in the right middle lobe.
- Kerley B lines
- Short horizontal lines at the lung periphery from interstitial fluid, classically seen in pulmonary edema/heart failure.
- Sputum Gram stain interpretation
- Gram-positive diplococci suggest S. pneumoniae; gram-negative rods suggest Klebsiella/Pseudomonas; guides empiric antibiotic choice in pneumonia.
- Pulsus paradoxus
- A systolic BP fall > 10 mm Hg on inspiration, seen in severe asthma, cardiac tamponade, and tension pneumothorax.
- Clubbing
- Bulbous fingertips and loss of the nail-bed angle from chronic hypoxemia (cystic fibrosis, bronchiectasis, lung cancer, interstitial lung disease).
- Accessory muscle use
- Recruitment of sternocleidomastoid and scalene muscles signaling increased work of breathing and impending respiratory failure.
- Tactile fremitus
- Palpable vibration during speech; increased over consolidation (pneumonia) and decreased over pleural effusion or pneumothorax.
- Crackles (rales)
- Discontinuous popping breath sounds from fluid or reopening alveoli — heard in pulmonary edema, pneumonia, and fibrosis.
- Wheezes
- High-pitched continuous musical sounds from narrowed airways; expiratory in asthma/COPD. Sudden silence ("silent chest") signals severe obstruction.
- Stridor
- High-pitched inspiratory sound from upper-airway narrowing (croup, post-extubation edema, foreign body); treat with cool mist or racemic epinephrine.
- Pleural friction rub
- A grating sound during inspiration and expiration from inflamed pleural surfaces (pleurisy, pulmonary embolism with infarction).
- Glasgow Coma Scale
- Scores eye, verbal, and motor responses from 3 to 15; ≤ 8 indicates an unprotected airway and the need to consider intubation.
- Apnea test (brain death)
- Off the ventilator on oxygen, a PaCO2 rise to ≥ 60 mm Hg (or ≥ 20 above baseline) with no respiratory effort supports brain death.
- Bedside spirometry weaning criteria
- VC > 10–15 mL/kg, spontaneous VT > 5 mL/kg, RR < 35, MIP more negative than −20, RSBI < 105 suggest readiness to wean.
- Recommend chest physiotherapy
- Indicated for retained secretions with ineffective cough (cystic fibrosis, bronchiectasis, > ~25–30 mL sputum/day), not routine pneumonia.
- Recommend bronchoscopy
- Suggest for retained secretions or atelectasis unresponsive to therapy, foreign-body removal, hemoptysis evaluation, or specimen collection.
- Recommend arterial line
- Indicated when frequent ABGs or continuous beat-to-beat blood-pressure monitoring is needed in unstable, ventilated patients.
- Modified Allen test
- Confirms collateral ulnar flow before radial arterial puncture; the hand should re-pink within ~5–15 seconds after releasing the ulnar artery.
- Cardiac output (Fick principle)
- Oxygen consumption ÷ arteriovenous O2 content difference. A low output widens the a−v O2 difference and lowers SvO2.
- Central venous pressure (CVP)
- Right-heart preload, normal ~2–6 mm Hg. Elevated in fluid overload, right heart failure, cor pulmonale, tamponade, and tension pneumothorax.
- Pulmonary capillary wedge pressure (PCWP)
- Reflects left-atrial filling pressure, normal ~4–12 mm Hg. High (> 18) = cardiogenic pulmonary edema; normal/low with edema = ARDS.
- Pulmonary artery pressure
- Normal ~25/8 mm Hg (mean < 20). Elevated in pulmonary hypertension, PE, hypoxic vasoconstriction, and left heart failure.
- Sinus tachycardia
- Normal upright P waves with a rate > 100/min; in respiratory patients consider hypoxemia, hypercapnia, anxiety, fever, or beta-agonist effect.
- Premature ventricular contractions (PVCs)
- Wide, early QRS complexes without a preceding P wave; often triggered by hypoxemia, hypokalemia, or acidosis — check oxygenation first.
- Atrial fibrillation
- Irregularly irregular rhythm with no discrete P waves; reduces cardiac output and is common in COPD, hypoxemia, and heart failure.
- Cor pulmonale
- Right ventricular hypertrophy/failure from chronic lung disease and pulmonary hypertension; managed by correcting hypoxemia with oxygen.
- Hyperkalemia ECG signs
- Peaked T waves, widened QRS, and loss of P waves; can cause life-threatening arrhythmias, sometimes accompanying metabolic acidosis.
- Apgar score
- Rates newborn Appearance, Pulse, Grimace, Activity, Respiration 0–2 each at 1 and 5 minutes; 7–10 normal, 4–6 moderate distress, 0–3 needs resuscitation.
- Silverman-Andersen score
- Grades neonatal respiratory distress (retractions, nasal flaring, grunting); a higher score means worse distress, opposite to Apgar.
- Transcutaneous monitoring
- Noninvasively trends PtcO2 and PtcCO2 through heated skin, mainly in neonates; rotate the site to prevent burns and recalibrate periodically.
- L/S ratio
- Lecithin-to-sphingomyelin ratio in amniotic fluid; ≥ 2:1 indicates fetal lung maturity and low risk of respiratory distress syndrome.
- Galvanic vs polarographic O2 analyzer
- Galvanic (fuel cell) self-powered, slower; polarographic (Clark) needs a battery, faster response. Calibrate both to 21% and 100% O2.
- Pulse oximeter limitations
- Unreliable with poor perfusion, motion, nail polish, carboxyhemoglobin (falsely high), and methemoglobin (drifts toward 85%). Confirm with CO-oximetry.
- Capnograph waveform phases
- Phase I baseline (dead space), II rising upstroke, III alveolar plateau, then inspiratory downstroke. End of plateau = end-tidal CO2.
- Shark-fin capnogram
- A sloped, blunted upstroke on capnography indicates bronchospasm or obstruction (asthma, COPD); flattens after effective bronchodilation.
- Curare cleft
- A notch in the capnogram plateau showing spontaneous effort against the ventilator as paralytic wears off — reassess sedation/neuromuscular blockade.
- Pneumotachometer
- Measures gas flow (and integrates to volume) via a pressure drop across a fixed resistance; condensation or secretions cause inaccurate readings.
- Wright respirometer
- A handheld vane device that measures exhaled tidal and minute volume at the bedside; reads inaccurately at very low or very high flows.
- Heated wire circuit
- Heats the ventilator circuit to prevent condensation ("rainout") that can cause auto-triggering, inaccurate volumes, and false alarms.
- Water seal chamber (chest drainage)
- Acts as a one-way valve; continuous bubbling signals an air leak, and tidaling (fluid rising/falling with breathing) confirms patency.
- Chest tube: continuous bubbling
- Bubbling in the water-seal chamber indicates an air leak — check connections first; if persistent, suspect a bronchopleural leak.
- Bubble humidifier
- Adds water vapor to dry gas for low-flow oxygen above ~4 L/min; a popping pressure-relief valve signals downstream obstruction or kinked tubing.
- Heated humidifier
- Delivers warmed, fully saturated gas (target ~37 °C, 100% relative humidity at the airway) for intubated patients to prevent mucosal drying.
- Heat and moisture exchanger (HME)
- A passive "artificial nose" that recycles exhaled heat and moisture; avoid with thick secretions, hemoptysis, or large air leaks (increases dead space).
- Small-volume nebulizer
- Pneumatic jet nebulizer driven at 6–8 L/min that aerosolizes medication; tapping the cup and proper fill volume reduce dead-volume waste.
- Metered-dose inhaler with spacer
- A holding chamber slows aerosol and reduces oropharyngeal deposition, improving delivery for patients with poor hand-breath coordination.
- Ultrasonic nebulizer
- Uses a vibrating piezoelectric crystal to make a dense aerosol; can deliver large water volumes for sputum induction but may cause bronchospasm.
- Aerosol particle size (MMAD)
- Particles 1–5 microns deposit in the lower airways; larger particles impact in the upper airway, smaller ones are exhaled.
- Bourdon gauge flowmeter
- A pressure-based flowmeter that reads accurately regardless of position but over-reads flow if there is downstream obstruction.
- Thorpe tube flowmeter
- A gravity-dependent, back-pressure-compensated flowmeter; must stay upright to read accurately. A stuck float signals a contaminated tube.
- DISS and PISS connections
- Diameter-Index and Pin-Index Safety Systems prevent connecting gas equipment to the wrong gas source — a safeguard against gas mix-ups.
- E-cylinder duration calculation
- Minutes remaining = (gauge psi × 0.28 cylinder factor) ÷ flow in L/min. A full O2 E-cylinder holds ~625 L at ~2,200 psi.
- Oxygen concentrator
- Uses molecular sieve beds (zeolite) to deliver ~90–95% O2 at low flows for home use; output purity drops if the sieve fails or at high flow.
- Bacterial filter on ventilator
- Placed on the expiratory limb to protect the ventilator and environment; a wet or clogged filter raises resistance and triggers high-pressure alarms.
- Ventilator self-test / leak test
- Run before connecting a patient to verify circuit integrity, alarm function, and sensor calibration; a failed leak test means find and fix the leak first.
- Sterilization vs disinfection
- Sterilization destroys all microbes including spores (autoclave, ethylene oxide); disinfection kills most pathogens but not all spores.
- Glutaraldehyde
- A chemical agent used for high-level disinfection of semicritical equipment (e.g., bronchoscopes); requires adequate soak time and thorough rinsing.
- Standard precautions
- Treat all blood and body fluids as infectious: hand hygiene plus gloves, gown, mask, and eye protection based on anticipated exposure.
- Ventilator-associated pneumonia bundle
- Elevate the head of bed 30–45°, daily sedation and extubation-readiness assessment, oral care, and DVT/stress-ulcer prophylaxis to lower VAP risk.
- Closed (in-line) suction catheter
- Allows suctioning without disconnecting the patient, preserving PEEP and reducing exposure/contamination in high-FiO2 or infectious patients.
- Sweep speed and gain (waveform QC)
- Adjust display sweep speed and amplitude to read ventilator graphics correctly; misreading a flat or compressed trace can mask auto-PEEP or asynchrony.
- Three-point blood-gas QC
- Run low, normal, and high control levels to validate analyzer accuracy across the clinical range before reporting patient results.
- CPAP
- Continuous positive airway pressure for spontaneously breathing patients; raises FRC to improve oxygenation in atelectasis, OSA, and cardiogenic edema.
- BiPAP
- Noninvasive ventilation with separate IPAP and EPAP levels; the IPAP–EPAP difference (pressure support) drives ventilation in COPD exacerbation.
- Noninvasive ventilation indications
- First-line for COPD exacerbation with respiratory acidosis and for cardiogenic pulmonary edema; avoid with apnea, shock, or inability to protect the airway.
- PEEP
- Positive end-expiratory pressure that keeps alveoli open, raises FRC, and improves oxygenation in ARDS; excess PEEP lowers cardiac output and risks barotrauma.
- Optimal (best) PEEP
- The PEEP that gives the best oxygenation and compliance with the least hemodynamic compromise; titrate by oxygenation, compliance, and blood pressure.
- Pressure-controlled ventilation (PCV)
- Delivers a set inspiratory pressure with a decelerating flow; tidal volume varies with compliance and resistance, so monitor VT closely.
- Volume-controlled ventilation (VCV)
- Delivers a guaranteed tidal volume with a fixed flow; airway pressure varies with compliance and resistance, so watch the peak/plateau pressures.
- Pressure-regulated volume control (PRVC)
- A dual-control mode that targets a set tidal volume at the lowest pressure, adjusting inspiratory pressure breath to breath as compliance changes.
- Airway pressure release ventilation (APRV)
- Prolonged high CPAP with brief timed releases; recruits collapsed alveoli in ARDS while allowing spontaneous breathing.
- High-frequency oscillatory ventilation (HFOV)
- Delivers very small tidal volumes at high rates around a constant mean airway pressure; a lung-protective rescue mode in severe neonatal/ARDS hypoxemia.
- Inspiratory-to-expiratory (I:E) ratio
- Normal ~1:2 to 1:3; lengthen expiration (e.g., 1:4) for obstructive air trapping, and consider inverse ratio to improve oxygenation in ARDS.
- Flow trigger vs pressure trigger
- Flow triggering (sensing a flow change) generally requires less patient effort than pressure triggering; sensitivity set ~1–3 L/min or −1 to −2 cm H2O.
- Adjust ventilation for high PaCO2
- To lower PaCO2, increase minute ventilation by raising the respiratory rate or tidal volume (staying lung-protective).
- Adjust oxygenation parameters
- To raise PaO2/SpO2, increase FiO2 and/or PEEP; once FiO2 exceeds ~0.60, raise PEEP to recruit alveoli and limit oxygen toxicity.
- Oxygen toxicity
- Prolonged FiO2 > 0.50–0.60 can cause absorption atelectasis and alveolar injury; use the lowest FiO2 maintaining adequate oxygenation.
- Ventilator dyssynchrony
- Mismatch between patient effort and ventilator delivery (double-triggering, flow starvation, auto-PEEP); fix by adjusting flow, trigger, or sedation, not just paralysis.
- Prone positioning
- Improves V/Q matching and oxygenation in moderate-to-severe ARDS; guidelines support ≥ 12–16 hours prone per session for sustained benefit.
- Spontaneous breathing trial (SBT)
- A brief trial on minimal support (low PSV or T-piece) to test readiness to extubate; failure shows as tachypnea, distress, desaturation, or hemodynamic change.
- Rapid-sequence intubation (RSI)
- Near-simultaneous sedative and paralytic for emergent intubation in patients at aspiration risk; have suction, bag-mask, and rescue airways ready.
- Sniffing position
- Slight neck flexion with head extension aligns the oral, pharyngeal, and laryngeal axes to optimize the view for intubation in adults.
- Oropharyngeal airway
- Holds the tongue forward to maintain an airway in an unconscious patient; in an awake patient it triggers gagging or vomiting — use a nasopharyngeal airway instead.
- Laryngeal mask airway (LMA)
- A supraglottic device for ventilation when bag-mask is difficult or intubation fails; it does not fully protect against aspiration.
- Endotracheal tube size (adult)
- Typical internal diameter 7.0–8.0 mm for women and 8.0–9.0 mm for men; larger bore lowers airflow resistance and eases bronchoscopy and secretion clearance.
- ET tube size (pediatric)
- Uncuffed tube size ≈ (age ÷ 4) + 4 mm; e.g., a 4-year-old needs roughly a 5.0 mm internal-diameter tube.
- Suctioning technique
- Pre-oxygenate, limit each pass to ≤ 15 seconds, apply suction only on withdrawal, and keep adult vacuum about −100 to −150 mm Hg.
- Suction catheter size
- Outer diameter should be less than half the ET tube's internal diameter; size in French ≈ (ET tube ID × 2) to limit airway pressure drop.
- Hazards of suctioning
- Hypoxemia, vagally mediated bradycardia, dysrhythmias, mucosal trauma, atelectasis, and raised intracranial pressure — preoxygenate and limit duration.
- Tracheostomy care
- Clean or replace the inner cannula and stoma regularly; keep an obturator and a spare tube of the same and a smaller size at the bedside.
- Speaking valve (Passy-Muir)
- A one-way valve on a tracheostomy that lets air exit through the upper airway for speech; the cuff must be deflated before placement to avoid suffocation.
- High-flow nasal cannula (HFNC)
- Delivers heated, humidified gas up to 60 L/min with a precise FiO2; washes out dead space and provides a small PEEP effect in hypoxemic respiratory failure.
- Heliox therapy
- A helium-oxygen mix that is less dense than air, lowering resistance through narrowed airways in severe asthma and upper-airway obstruction; flowmeters need a correction factor.
- Inhaled nitric oxide
- A selective pulmonary vasodilator that improves oxygenation in persistent pulmonary hypertension of the newborn and refractory ARDS; wean slowly to avoid rebound.
- Surfactant replacement therapy
- Instilled into the airway of premature neonates with respiratory distress syndrome to lower surface tension; monitor for transient desaturation during instillation.
- Levalbuterol
- The R-isomer short-acting beta-2 agonist; bronchodilates with potentially fewer tachycardia/tremor side effects than racemic albuterol.
- Salmeterol / formoterol
- Long-acting beta-2 agonists (LABAs) for maintenance bronchodilation; never used as monotherapy in asthma — combine with an inhaled corticosteroid.
- Tiotropium
- A long-acting anticholinergic (LAMA) for maintenance bronchodilation in COPD; not a rescue medication for acute bronchospasm.
- Inhaled corticosteroids
- Anti-inflammatory controllers (budesonide, fluticasone) for persistent asthma; rinse the mouth after use to prevent oral thrush and dysphonia.
- Systemic corticosteroids
- Oral or IV steroids (prednisone, methylprednisolone) reduce airway inflammation in asthma and COPD exacerbations over hours, not minutes.
- N-acetylcysteine (Mucomyst)
- A mucolytic that breaks disulfide bonds to thin secretions; its sulfur odor and irritant effect can trigger bronchospasm, so pretreat with a bronchodilator.
- Cromolyn sodium
- A mast-cell stabilizer used prophylactically for asthma (including exercise-induced); it has no role in treating an acute attack.
- Pentamidine (aerosolized)
- Inhaled antibiotic for Pneumocystis pneumonia prophylaxis; deliver in a negative-pressure room with a filtered nebulizer to protect staff.
- Tobramycin (inhaled)
- An inhaled aminoglycoside antibiotic for chronic Pseudomonas in cystic fibrosis; delivers high airway concentrations with low systemic toxicity.
- Magnesium sulfate (asthma)
- IV adjunct in severe asthma exacerbations that relaxes bronchial smooth muscle when standard bronchodilators and steroids are insufficient.
- Epinephrine in anaphylaxis
- Intramuscular epinephrine is the first-line treatment for anaphylaxis with bronchospasm and hypotension; give early into the anterolateral thigh.
- Tension pneumothorax management
- A life-threatening emergency: immediate needle decompression (2nd intercostal space, midclavicular line) followed by chest-tube placement.
- Compression-to-ventilation ratio (adult CPR)
- 30:2 for one or two rescuers without an advanced airway; with an advanced airway, give continuous compressions and one breath every 6 seconds.
- High-quality chest compressions
- Rate 100–120/min, depth ≥ 2 inches (5 cm) in adults, full recoil, and minimal interruptions for the best perfusion during CPR.
- Defibrillation rhythms
- Shock ventricular fibrillation and pulseless ventricular tachycardia; do not shock asystole or pulseless electrical activity (treat with CPR and epinephrine).
- ACLS epinephrine dosing
- 1 mg IV/IO every 3–5 minutes during cardiac arrest to improve coronary and cerebral perfusion through vasoconstriction.
- Amiodarone in cardiac arrest
- An antiarrhythmic given for shock-refractory VF/pulseless VT: 300 mg IV/IO first dose, then 150 mg if needed.
- Post-cardiac-arrest oxygenation
- After return of spontaneous circulation, titrate FiO2 to keep SpO2 ~92–98% and avoid hyperoxia, which worsens reperfusion injury.
- Manual resuscitator (bag-valve-mask)
- Delivers near-100% O2 with a reservoir at 10–15 L/min; ventilate ~10–12/min in adults, watching for visible chest rise.
- Pediatric CPR compression-ventilation ratio
- 30:2 for a single rescuer and 15:2 for two rescuers in infants and children; compression depth about one-third the chest's AP diameter.
- Neonatal resuscitation initial steps
- Warm, dry, stimulate, and position; if apneic or HR < 100, start positive-pressure ventilation, and begin compressions if HR < 60 despite effective PPV.
- Croup management
- Viral subglottic edema causing a barking cough and stridor; treat with cool humidified mist, racemic epinephrine, and corticosteroids.
- Epiglottitis precautions
- Acute supraglottic swelling (drooling, tripod posture); avoid agitating the child or examining the throat, and prepare for controlled intubation in the OR.
- Pursed-lip breathing
- A technique that creates back-pressure to splint airways open, slowing exhalation and reducing air trapping and dyspnea in COPD.
- Positive expiratory pressure (PEP) therapy
- Exhaling against resistance keeps airways open and moves secretions centrally; flutter/Acapella devices add oscillation for airway clearance.
- High-frequency chest wall oscillation
- An inflatable vest that vibrates the chest to loosen secretions in cystic fibrosis and bronchiectasis without manual chest physiotherapy.
- Pulmonary rehabilitation
- A structured program of exercise training, education, and breathing techniques that improves dyspnea, exercise tolerance, and quality of life in COPD.
- Smoking cessation counseling
- The single most effective intervention to slow COPD progression; combine behavioral support with nicotine replacement or pharmacotherapy.
