4.3 Aerosol Medications and Gas Therapy
Key Takeaways
- Aerosol device selection depends on the drug, patient coordination, inspiratory flow, artificial-airway status, and whether continuous delivery is needed.
- Short-acting beta agonists such as albuterol are judged by improved peak flow, longer expiratory phase, reduced wheeze, and easier speech; tachycardia and tremor are side effects, not proof of success.
- Ipratropium is an anticholinergic; keep it out of the eyes because it can worsen narrow-angle glaucoma, and inhaled corticosteroids require mouth rinsing to prevent thrush.
- Heliox lowers gas density to reduce work of breathing through narrowed airways, but it is useless once a high FiO2 leaves too little helium in the mixture.
- Inhaled nitric oxide is a selective pulmonary vasodilator (monitor methemoglobin and nitrogen dioxide), and surfactant treats neonatal respiratory distress syndrome.
Delivery Technique Is Part of the Drug
Aerosol items are not only drug-name recall. The TMC expects you to decide whether the patient can operate the device, whether the dose can reach the lower airway, how to correct poor technique, and how to judge effect. A metered-dose inhaler (MDI) demands timed actuation, a slow inspiration, and a breath hold; a spacer removes the coordination demand and cuts oropharyngeal deposition. A small-volume nebulizer (SVN) is the choice when the patient is acutely dyspneic, cannot coordinate an MDI, or needs repeated or continuous delivery.
A dry-powder inhaler (DPI) needs a strong inspiratory flow, so it is a poor choice during a severe exacerbation.
Aerosol Decision Table
| Situation | Device direction | Key monitoring point |
|---|---|---|
| Stable patient, good technique | MDI or DPI | Symptom relief, technique check |
| Poor hand-breath coordination | MDI with spacer | One actuation at a time |
| Severe dyspnea or fatigue | Small-volume nebulizer | Heart rate, tremor, airflow |
| Artificial airway | MDI adapter or in-line nebulizer | Placement, humidifier effect, leaks |
| Upper-airway edema with stridor | Racemic epinephrine, if ordered | Rebound symptoms, heart rate |
| Severe distress, low inspiratory flow | Avoid DPI | Use SVN instead |
Medication Patterns and Endpoints
Albuterol and other short-acting beta agonists relax bronchial smooth muscle for reversible bronchospasm. Look for a higher peak expiratory flow, a longer expiratory phase, less wheeze, reduced accessory-muscle use, and easier speech. Tachycardia and tremor are beta-adrenergic side effects, not evidence the treatment worked. Ipratropium is an anticholinergic bronchodilator commonly combined with albuterol in COPD exacerbations; protect the eyes because it can precipitate or worsen narrow-angle glaucoma.
Inhaled corticosteroids reduce inflammation over days, are not rescue drugs, and require a post-dose mouth rinse to prevent oral candidiasis (thrush) and dysphonia. Racemic epinephrine reduces mucosal edema in croup and post-extubation stridor; watch for rebound edema and tachycardia.
Correcting Delivery Barriers and Technique
The same drug fails when delivery is poor. For MDI with spacer: exhale normally, actuate one puff into the chamber, inhale slowly and deeply, then hold the breath about 5-10 seconds; firing several puffs into the spacer at once wastes drug and increases impaction. For an SVN, visible mist confirms only that aerosol is being generated — it does not prove effect; reassess breath sounds, respiratory rate, heart rate, SpO2, and peak flow.
With an artificial airway, place the device so the circuit carries particles toward the airway, account for humidifier and filter losses, and prefer an in-line option over breaking the circuit.
Specialty Gases
Heliox (helium-oxygen) is less dense than air, so it converts turbulent flow to laminar flow through a narrowed airway, reducing work of breathing in upper-airway obstruction, severe asthma, or post-extubation stridor while definitive care is arranged. The catch the exam loves: a helium-rich mix (such as 80/20 or 70/30) is required, so heliox becomes useless once the patient needs a high FiO2 — there is no longer enough helium to lower density, and priority shifts to oxygenation and airway control.
- Inhaled nitric oxide (iNO): a selective pulmonary vasodilator for pulmonary hypertension and refractory hypoxemia. Monitor methemoglobin and nitrogen dioxide formation, and never stop it abruptly because of rebound pulmonary hypertension.
- Surfactant: replacement therapy for neonatal respiratory distress syndrome; lung compliance and oxygenation can change rapidly after instillation, so confirm tube position and be ready to reduce settings.
Safety Notes
Do not keep repeating bronchodilator treatments without reassessment when tachyarrhythmia, chest pain, severe tremor, or hypokalemia appears. Infection control matters too: nebulizer cups, masks, and circuit adapters can transmit pathogens if not cleaned or stored properly. Tie every gas or aerosol decision to its endpoint.
Aerosol Deposition Physics the Exam Tests
Particle size determines where an aerosol lands. Particles in the 1-5 micron range deposit in the lower airways and are the therapeutic target for bronchodilators; larger particles (above about 10 microns) impact in the mouth and oropharynx, while particles below 1 micron are largely exhaled. This explains several test answers: a fast, forceful inhalation increases inertial impaction in the throat and reduces lower-airway delivery, which is why slow inhalation is coached; a spacer lets large droplets settle out before they reach the mouth, cutting oropharyngeal deposition and the thrush risk from inhaled steroids.
Breathing pattern matters too — a slow, deep breath with an end-inspiratory hold lets gravity and diffusion settle small particles onto the airway wall, while shallow, rapid breaths waste the dose. When a stem describes good drug choice but poor response, suspect a delivery failure (wrong device for the patient's flow, no spacer, broken technique, circuit leak) before assuming the medication is ineffective.
Continuous Bronchodilator and Status Asthmaticus
In severe asthma not responding to intermittent treatments, the exam may move toward continuous nebulized albuterol (often 10-20 mg/hr) while monitoring for tachyarrhythmia, tremor, and hypokalemia, because beta agonists drive potassium intracellularly. The therapeutic endpoint is improving airflow and a longer expiratory phase, not a rising heart rate. If the patient tires despite maximal bronchodilation, the answer shifts away from more aerosol and toward ventilatory support, because exhaustion in status asthmaticus is an impending-failure sign.
Specialty Gas Delivery Details
Heliox must be delivered through a system calibrated for low-density gas: a standard oxygen flowmeter under-reads heliox flow, so the actual delivered flow is higher than the dial shows (multiply by roughly 1.8 for 80/20 and 1.6 for 70/30). When heliox drives a nebulizer, increase the flow because the low-density gas generates a different aerosol output. For inhaled nitric oxide, deliver through a circuit that injects gas proximal to the patient and continuously monitors delivered nitric oxide, nitrogen dioxide, and oxygen; abrupt discontinuation risks rebound pulmonary hypertension, so wean rather than stop.
Surfactant is instilled directly into the endotracheal tube, after which compliance can jump quickly and require prompt downward adjustment of pressures or volumes to avoid overdistension.
A patient using an MDI with a spacer actuates three puffs into the chamber and then takes one rapid breath. Which coaching point should the therapist correct first?
After a bronchodilator treatment for wheezing, which finding best supports that the medication had its intended therapeutic effect?
A patient with post-extubation stridor is being considered for heliox. SpO2 is 86% despite FiO2 0.70 by mask, and the work of breathing is increasing. What is the best interpretation?