4.2 Airway Clearance and Lung Expansion

Clearance Versus Expansion

Airway clearance moves mucus from small airways toward large airways so it can be coughed or suctioned out. Lung expansion therapy re-inflates collapsed alveoli. TMC stems often combine the two, so first decide whether the scenario describes retained secretions, atelectasis from shallow breathing, or both.

Retained secretions present as rhonchi, coarse crackles, thick sputum, an ineffective cough, recurrent infection, or a sawtooth pattern on the ventilator flow waveform. Atelectasis risk presents after surgery, with pain-related splinting, a low inspiratory capacity, or basilar volume loss.

Intervention Decision Table

Airway Clearance Choices

Positive expiratory pressure (PEP) keeps small airways splinted open during exhalation, letting collateral channels fill behind mucus and push it proximally; typical resistance produces 10-20 cmH2O during exhalation. Oscillatory PEP (flutter, Acapella) adds vibration that loosens tenacious secretions in cystic fibrosis and bronchiectasis. Chest physiotherapy (CPT) combines postural drainage, percussion, vibration, and directed cough. Mechanical insufflation-exsufflation is the targeted choice for a neuromuscular patient whose peak cough flow is too weak to clear central secretions.

Note that suctioning removes only central-airway secretions — it does not mobilize peripheral mucus and does not re-expand atelectasis.

Lung Expansion Choices

Incentive spirometry works only in an awake, cooperative patient who can take a slow, deep breath and hold it for 3-5 seconds, mimicking a natural sigh to reopen alveoli; it is preventive or rehabilitative, never a rescue for acute distress. Intermittent positive-pressure breathing (IPPB) delivers a machine-assisted deep breath when a patient cannot generate an adequate volume voluntarily, but it can cause gastric insufflation, dizziness from hypocapnia, or barotrauma, so it requires monitoring of delivered volume and tolerance.

Sequencing, Tolerance, and Contraindications

Many stems reward a combined, ordered plan: give a bronchodilator first when wheezing or reversible obstruction is present, then perform oscillatory PEP, then coach huff coughing. Do not confuse secretion removal with volume restoration — suctioning a dry airway will not open postoperative atelectasis, and incentive spirometry alone will not clear copious infected sputum.

• Head-down drainage is unsafe with increased intracranial pressure, active hemoptysis, severe gastroesophageal reflux or recent vomiting, untreated pneumothorax, recent esophageal surgery, or hemodynamic instability — choose a modified position and continue targeted clearance rather than withholding all therapy.
• Stop or pause therapy for severe hypoxemia, chest pain, new arrhythmia, bronchospasm, marked dyspnea, or instability, then stabilize and pick a safer technique.

Evaluating Response

Effective clearance improves breath sounds, cough strength, secretion movement, oxygenation, and comfort; effective expansion improves inspiratory capacity, chest excursion, and radiographic atelectasis over time. Read trend language carefully: more sputum during a treatment is success when breath sounds and SpO2 improve afterward, while less sputum is not success if rhonchi, fever, and a weak cough persist. A rising inspiratory capacity and fewer basilar crackles matter more than completing a set number of breaths.

Use a consistent exam sequence: identify mucus versus atelectasis, choose the least invasive targeted therapy, add a bronchodilator or humidification when the stem supports it, check positioning contraindications, and reassess objective findings.

Matching the Technique to the Patient's Strength

Patient participation drives the choice as much as the chest assessment does. A cooperative, alert patient can learn huff coughing, the active cycle of breathing technique, autogenic drainage, and incentive spirometry — all effort-dependent. A fatigued, weak, or uncooperative patient needs effort-independent help: positive expiratory pressure devices, mechanical insufflation-exsufflation for a failing cough, suction access, or positive-pressure expansion.

The neuromuscular patient is the classic example — peak cough flow below roughly 160 L/min predicts an ineffective cough and points the answer toward mechanical cough assist rather than coaching. Tolerance clues such as pain, dizziness, desaturation, nausea, or fatigue should change the plan immediately; the right exam answer often pairs a clearance technique with pain control or supplemental oxygen rather than pushing a struggling patient through a full protocol.

Postural Drainage Positioning Logic

When the stem names an affected lung segment, the drainage position aims that segment uppermost so gravity assists. Upper-lobe segments drain with the patient sitting or leaning; the right middle lobe and lingula drain in a slight head-down position rotated toward the opposite side; the posterior basal segments of the lower lobes drain prone in steep head-down (Trendelenburg).

Because head-down positions are the ones contraindicated by increased intracranial pressure, reflux, recent surgery, and instability, the exam frequently tests a modified position — for example, flat side-lying instead of full Trendelenburg — that still biases drainage without the head-down risk.

Humidification's Role in Clearance

Dry inspired gas, especially through an artificial airway or a high-flow oxygen device, thickens secretions and defeats every clearance technique. The exam often expects you to fix the upstream cause: add adequate humidification, ensure systemic hydration, and only then reattempt clearance. A patient whose sputum has become thick and crusted on a long run of unhumidified oxygen needs humidification and hydration before percussion or suction will succeed, because no amount of mechanical effort will mobilize inspissated, dehydrated mucus efficiently.

Always reassess after the correction rather than escalating to a more invasive technique first.