Welcome to PICU Doc On Call, A Podcast Dedicated to Current and Aspiring Intensivists.
I'm Pradip Kamat and I'm Rahul Damania. We are coming to you from Children's Healthcare of Atlanta - Emory University School of Medicine.
Welcome to our discussion today on airway clearance in the critically-ill patient in the PICU. We will focus on the use of pharmacological as well as non-pharmacological techniques in critically ill children admitted to the ICU. This episode will be a general overview as specific clinical scenarios such as NM disease may warrant specific therapeutics.
Let’s get started with the case:
We have an 8-month old ex-34 week premie intubated for acute respiratory failure secondary to RSV bronchiolitis. The patient is on a conventional mechanical ventilator receiving a TV of 6ml/kg, rate of 20, PEEP 6, 40% FiO2 inspiratory time of 0.7
CXR shows a pattern suggestive of viral pneumonia with minimal hyperinflation and atelectasis of the right middle lobe. The patient has excessive secretions when the suction catheter is assessed. The patient is hemodynamically stable and is on feeds via a NG tube.
Rahul, Can you comment on how a child clears his/her pulmonary secretions normally when not ill?
That's an excellent question. Normally some baseline secretions are produced by all humans. Normal bronchial secretions are made up of contributions from mucus-secreting (goblet)cells as well as cells secreting serous fluid. The ciliary epithelium made of columnar cells line the entire tracheobronchial tree up to the alveolar ducts. This ciliary epithelium provides the coordinated rhythmic force that propels the overlying “mucus blanket” towards the central airways and upper respiratory tract.
Primary mechanisms of tracheobronchial clearance of these secretions consist of (1) The mucociliary (MC) escalator in the smaller airways and (2) Cough in central and larger airways. The co-ordinating activity of the beating cilia and their interaction with the overlying viscoelastic layer of mucus makes up the mucociliary escalator. The MC escalator helps remove both healthy and pathologic secretions from the airways as well as the removal of inhaled particles. This MC transport can be affected by mycoplasma, influenza and other viruses as well as exposure to toxins (cigarette smoke, vaping) as well as in CF, asthma, COPD, and ciliary dyskinesia just to name a few.
Once the secretions are in large or central airways they are coughed out or swallowed.
Let’s transition and talk a little on how one generates an effective cough:
For an effective cough one needs firstly to take a sufficiently deep breath in.
The glottis needs to close briefly to allow an increase in intrathoracic pressure
This is followed by expulsive glottic opening together with abdominal contraction, which results in air being forcibly expelled.

 Individuals with neuromuscular disease, bulbar insufficiency, obtunded patients, those on MV with chemical neuromuscular blockade, severe skeletal deformity may have decreased cough expiratory airflow. Reduced ability to cough results in secretion retention, mucus plugging, atelectasis and pre-disposition to infection even if the MC escalator function is normal.
Q2. Pradip can you tell us about atelectasis
This is a great question. The term atelectasis means “imperfect expansion” and indicates reversible loss of aerated lung with otherwise normal lung parenchyma.
Thats a nice concise definition, so if atelectasis reperesents imperfect expansion, what are mechanisms which keep our lungs open?
There are three major mechanisms:
1. Pulmonary Surfactant 
2. Collateral Ventilation 
3. Lung & Chest Wall Balance
Let’s go into each of these in more detail:
A pulmonary surfactant that covers the large alveolar surface is composed of phospholipids (mostly phosphatidylcholine), neutral lipids, and surfactant-specific apoproteins (termed surfactant proteins A , B , C , and D ). By reducing...