Respiratory System (HB)

As atmospheric air is drawn into the body, it is cleaned, humidified, and warmed before being delivered to the lungs. In the lungs is where oxygen moves into the bloodstream and carbon dioxide moves out of the body.

The Respiratory System is composed of five main parts: Upper Airway, Lower airway, Alveoli, Chest Wall and Diaphragm, and the Brain Stem.

Upper Airway

The upper airway’s job is to make dirty, dry, and cold air “100% clean, 100% humid and (not quite) 100 degrees” by the time it reaches the beginning of the lower airway.

The main problem that we have to deal with in the upper airway is an obstruction, which can be partial or complete.

Lower Airway

The lower airway is the apparatus connecting the upper airway to the alveoli. Starting at the trachea, air moves down and splits into each lobe of the lungs. From there, the tubes (bronchial) keep splitting and getting smaller in diameter till they reach the alveoli. These semi-rigid tubes are covered on the inside by mucosal membranes. Think of it like a tree trunk that branches smaller and smaller until it ends in leaves.

Swelling is the primary problem associated with the lower airway. Swelling decreases the amount of “fresh” air that goes into the lungs and prevents the “bad” air from going out with each breath. When the bronchial tubes’ internal membranes swell, then swelling takes the path of least resistance—which is inward, causing a restriction in airflow. It is like an old drain pipe in a house—all of that build up over the years makes the sink drain slow.

As the lower airway gets constricted, not only is it difficult to draw air in, but it makes it difficult to exhale, forcing the patient to use energy to force the air out.

Alveoli

The alveoli are where the oxygen and carbon dioxide trade places in the capillary beds surrounding the alveoli. As the air enters the alveoli, it has a high concentration of oxygen and a low concentration of carbon dioxide. As the blood moves through the capillary beds surrounding the outside of the alveoli, its concentrations of the two gases are the opposite. For reasons outside the scope of what is needed here, there is a difference in pressure between the inside of the alveoli and the capillaries. The cell wall between them is permeable, which allows the two gases to try and balance. Oxygen moves into the circulatory system for distribution, and the carbon dioxide moves into the respiratory system to be exhaled.

We can have two basic problems in the alveoli—fluid buildup or collapse. Fluid comes either from the body shifting fluids around (edema) or from external fluids like drowning. Fluid shifting occurs due to medical problems and leads to a condition called Pulmonary Edema. Chronic heart problems, kidney problems, high blood pressure, and diabetes are the main causes of aberrant fluid shifting. High altitude and scuba diving are examples of “environmental” mechanisms that can cause fluid buildup. Anaphylaxis and inhalation burns are examples of acute conditions and trauma that can also affect the alveoli.

Chest Wall

The chest wall and diaphragm are the structures that create the pressure differential to allow the air to move in and out of the lungs. The rib cage creates a semi-flexible rigid structure that houses the lungs. At the bottom of the lungs is the diaphragm, a large thin muscle that divides the abdominal cavity from the chest cavity. As the muscles of our rib cage and diaphragm contract, it causes the chest cavity to expand in size and volume. This causes negative pressure inside the lungs, and air moves from the higher pressure (outside the body) to fill in the created vacuum. As the muscles relax, the increased pressure on the inside now wants to escape to the outside. Problems with the chest wall will be addressed in another topic.

Brain Stem

The brain’s connection to the respiratory system is to monitor the amounts of oxygen and carbon dioxide along with the pH of the blood. The brain can adjust the rate and depth of respiration as needed according to metabolic demands. If you are sitting on a comfy chair in front of a computer, you are not using a lot of energy, and your demand for oxygen for the cells is low. If you are on a stationary bike working out, your needs are higher.

The process of moving air in is called “inhalation” and is an active process—it takes energy to breathe in. Exhalation is normally a passive process—it takes no energy to breathe out—your diaphragm and chest muscles are relaxing. Anything that affects any of the five parts of the respiratory system can lead to a critical system problem.

Our best immediate treatment for any respiratory system problem is PROP.

• Position of Comfort: Patients will put themselves into a position of comfort when they are having issues. Do not try to put them in a different position if they seem to be managing as they are—which is usually a sitting position or “tripod.” If the patient is unconscious, we need to anticipate airway compromise, so we should place them in the recovery position.
• Reassurance: All patients benefit from reassurance. Try and talk them into manually controlling the breathing—slower and deeper.
• Oxygen: Provide supplemental oxygen if available
• Positive Pressure Ventilation: If the patient is not breathing adequately, you need to start assisting with breathing. Do not wait until respiratory arrest occurs before assisting.