7.2 Oxygen Therapy & Respiratory Care Support

Oxygen Therapy & Respiratory Care Support

Oxygen therapy represents one of the most common, life-saving therapeutic interventions in acute and long-term healthcare environments. Ambient room air contains approximately 21% oxygen (along with 78% nitrogen and 1% trace gases). When pathological conditions such as pneumonia, chronic obstructive pulmonary disease (COPD), pulmonary embolism, congestive heart failure, or severe anemia compromise alveolar gas exchange or oxygen-carrying capacity, supplemental oxygen must be administered to prevent cellular hypoxia, metabolic lactic acidosis, and organ failure.

However, oxygen is legally classified as a prescription drug. Administering improper flow rates or concentrations can cause severe clinical harm—ranging from oxygen toxicity and carbon dioxide narcosis to fatal combustion accidents. Allied healthcare professionals must master oxygen delivery devices, combustion safety mandates, pulse oximetry monitoring, and tracheostomy care boundaries.

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1. Pharmacology of Oxygen & Combustion Safety Principles

Because oxygen is a regulated pharmacological agent, it must be ordered by a licensed healthcare provider (physician, physician assistant, or nurse practitioner) except during emergent basic life support resuscitation. The physician's order must specify:

1. The specific delivery device (e.g., nasal cannula, Venturi mask).
2. The flow rate in liters per minute (L/min) or exact percentage of inspired oxygen (FiO2).
3. The target oxygen saturation range (e.g., maintain SpO2 ≥ 92%, or maintain SpO2 between 88% and 92% for chronic hypercapnic patients).

Combustion Hazards and Safety Protocols

Oxygen does not burn by itself; rather, it vigorously accelerates combustion. Materials that burn slowly in room air ignite explosively and burn with intense, uncontrollable heat in an oxygen-enriched environment.

• Signage: Prominently display "Oxygen in Use - No Smoking" signs on the entrance door of the patient's room and directly above the head of the bed.
• No Open Flames: Open flames, lit matches, lighters, candles, and smoking or vaping materials are strictly prohibited within 10 feet of oxygen delivery equipment.
• Electrical Safety: All electrical equipment in the room (hospital beds, IV infusion pumps, telemetry monitors) must be grounded (three-prong plugs) and regularly inspected by biomedical engineering. Frayed power cords, spark-producing electric razors, and friction toys are banned.
• Anti-Static Fabrics: Wool blankets and synthetic fabrics (nylon, polyester) generate electrostatic sparks upon movement. Patients receiving oxygen should be provided with 100% cotton blankets, gowns, and bed linens.
• The Critical Lubrication Rule (Absolute Petroleum Ban): Strictly avoid oil-based, petroleum-based lubricants or hydrocarbon ointments (such as Vaseline, petroleum jelly, mineral oil, or oil-based lip balms) on the lips, nares, or face of patients receiving oxygen. Hydrocarbon oils exposed to pressurized oxygen can undergo spontaneous, explosive ignition, causing catastrophic facial flash fires and third-degree airway burns. Use ONLY water-soluble lubricants (such as K-Y jelly, water-based saline gels, or glycerin-based products) to relieve oral and nasal mucosal dryness.

[Pressurized Oxygen Flow]
           +
[Flammable Hydrocarbon (Petroleum Jelly)]  ===>  [CATASTROPHIC FLASH FIRE]
           +
[Electrostatic Spark / Heat Source]

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2. Low-Flow vs. High-Flow Delivery Systems

Oxygen delivery devices are categorized based on whether they supply the patient's entire inspiratory gas demand:

• Low-Flow Systems: Supply oxygen at flow rates lower than the patient's total inspiratory peak flow rate. The patient entrains a variable volume of ambient room air (21% O2) around the device, meaning the actual Fraction of Inspired Oxygen (FiO2) varies depending on the patient's respiratory rate, tidal volume, and inspiratory effort.
• High-Flow Systems: Supply a total gas flow that meets or exceeds the patient's maximal inspiratory peak flow rate, delivering a precise, fixed FiO2 regardless of the patient's breathing pattern.

Nasal Cannula (Low-Flow)

• Flow Rate: 1 to 6 L/min.
• Delivered FiO2: 24% to 44%.
  • Room air baseline = 21% FiO2.
  • 1 L/min ≈ 24%
  • 2 L/min ≈ 28%
  • 3 L/min ≈ 32%
  • 4 L/min ≈ 36%
  • 5 L/min ≈ 40%
  • 6 L/min ≈ 44%
  • Clinical Rule of Thumb: Each 1 L/min increase in oxygen flow adds approximately 4% to the delivered FiO2 above ambient air.
• Humidification Mandate: Medical gas piped from hospital wall outlets or cylinders is completely dry. Flow rates of 4 L/min or higher require bubble humidification with sterile water. Unhumidified high flows desiccate the nasal mucosa, impair ciliary movement, cause thick mucus plugging, and trigger severe epistaxis (nosebleeds). (Humidification may also be added at 1–3 L/min if the patient complains of mucosal dryness).
• Proper Application: Insert the two prongs into the nares with the curvature pointing downward and inward, matching the anatomical path of the nasopharynx. Loop the tubing over the ears, and slide the cinch ring comfortably under the chin. Inspect the superior aspect of the ears and cheeks regularly for pressure injuries; apply foam padding sleeves over the tubing if redness occurs.

Simple Face Mask (Low-Flow)

• Flow Rate: 5 to 10 L/min.
• Delivered FiO2: 35% to 50%.
• The Absolute Safety Threshold (The 5 L/min Rule): The flow rate on a simple face mask must NEVER be set below 5 L/min. A minimum flow rate of 5 L/min is mandatory to continuously flush the patient's exhaled carbon dioxide out through the mask's exhalation ports. If the flow rate is set at 2 to 4 L/min, exhaled CO2 accumulates inside the mask cavity, forcing the patient to re-breathe carbon dioxide, resulting in severe respiratory acidosis and asphyxiation.

Non-Rebreather Mask (NRB) (Low-Flow / High Concentration)

• Flow Rate: 10 to 15 L/min.
• Delivered FiO2: 80% to 95% (approaching 100% under ideal seal).
• Indications: Acute clinical emergencies, severe hypoxemia, carbon monoxide poisoning, pulmonary edema, and acute respiratory distress while preparing for advanced airway management.
• Design Features: Equipped with a soft reservoir bag and a system of one-way flutter valves. One valve sits between the mask and the reservoir bag, allowing 100% oxygen from the bag into the mask during inhalation while preventing exhaled air from entering the bag. One or two flutter valves on the lateral mask ports permit exhaled air to escape during expiration while closing during inhalation to block room air entry.
• The Mandatory Pre-Inflation Rule: The technician must FULLY PRE-INFLATE the reservoir bag with oxygen before securing the mask over the patient's face. Pre-inflate the bag by placing a clean finger over the one-way valve inside the mask until the oxygen flow fills the bag completely.
• Maintaining Inflation: Set the flow rate between 10 and 15 L/min so that the reservoir bag remains at least one-half to two-thirds inflated during peak inhalation. If the reservoir bag collapses completely when the patient takes a breath, the oxygen flow rate is dangerously low; the technician must increase the flow rate immediately. A collapsed bag causes the patient to suffocate.

Venturi Mask (High-Flow / Precise Concentration)

• Flow Rate: 4 to 12 L/min (dictated by the specific adapter).
• Delivered FiO2: Precise, fixed concentrations: 24%, 28%, 31%, 35%, 40%, and 50%.
• Mechanism: Operates on Bernoulli's principle of fluid dynamics. Pressurized oxygen enters through a narrow orifice at high velocity, creating a localized drop in lateral pressure that draws in (entrains) a precise, calibrated volume of ambient room air through side entrainment ports.
• Clinical Indication (The COPD Gold Standard): The Venturi mask is the absolute gold standard for patients with Chronic Obstructive Pulmonary Disease (COPD), chronic bronchitis, and emphysema.
• Pathophysiology of Hypoxic Drive: In healthy individuals, ventilation is controlled by central chemoreceptors in the brainstem that respond to elevated arterial carbon dioxide (PaCO2). In patients with severe chronic COPD, arterial CO2 is chronically elevated, desensitizing the central chemoreceptors. These patients adapt to rely on peripheral chemoreceptors (in the carotid bodies and aortic arch) that respond to hypoxemia (low arterial oxygen / PaO2) to stimulate breathing—a state known as the hypoxic drive.
  • If high, uncontrolled oxygen concentrations (such as a simple mask or non-rebreather) are administered, the patient's PaO2 rises abruptly. The peripheral chemoreceptors sense adequate oxygen and shut down the stimulus to breathe.
  • The patient develops hypoventilation, severe hypercapnia, CO2 narcosis (somnolence, confusion, lethargy), respiratory arrest, and death.
  • The Venturi mask prevents this catastrophe by delivering an exact, predictable low-to-moderate FiO2 (e.g., exactly 24% or 28%), correcting life-threatening hypoxemia without abolishing the patient's hypoxic drive.
  • Current evidence note: Research now attributes most oxygen-induced CO2 retention in COPD to ventilation-perfusion mismatch and the Haldane effect rather than loss of hypoxic drive alone. The bedside rule is the same either way: give only the ordered oxygen and keep SpO2 within the ordered range (often 88% to 92%).
• Critical Care Rule: Never cover or obstruct the air entrainment ports of a Venturi mask with bedsheets, clothing, or blankets, as blocking ports reduces air entrainment and delivers unpredictably high oxygen concentrations.

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3. Oxygen Delivery Systems Comparison Table

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4. Pulse Oximetry Monitoring & Accuracy Troubleshooting

Pulse oximetry provides non-invasive, continuous measurement of functional arterial hemoglobin oxygen saturation (SpO2).

Clinical Standards and Alarm Safety

• Target Saturation: Normal SpO2 in healthy adults is 95% to 100%. In patients with severe chronic COPD or chronic hypercapnia, target SpO2 is typically titrated between 88% and 92%.
• Alarm Parameters: The PCT must verify that pulse oximeter high and low alarm limits are active at all times. Never silence, disable, or ignore pulse oximetry alarms. If an alarm sounds, immediately assess the patient's clinical appearance (respiratory effort, work of breathing, skin color, mental status) before troubleshooting equipment.

Factors Impairing Pulse Oximetry Accuracy

Pulse oximeters calculate SpO2 by transmitting two wavelengths of light (red light at 660 nm and infrared light at 940 nm) through a vascular bed, measuring the pulsatile differential absorption between oxygenated and deoxygenated hemoglobin. Multiple clinical factors interfere with this optical transmission:

1. Peripheral Vasoconstriction & Hypoperfusion: Cold extremities, hypothermia, shock, severe hypotension, and peripheral vascular disease reduce pulsatile capillary blood flow. The sensor cannot detect a reliable arterial pulse wave, displaying erratic readings or dashes. Action: Warm the extremity with a warm compress, or move the sensor to an alternate site (earlobe, forehead, or nasal bridge sensor).
2. Nail Polish and Artificial Acrylic Nails: Dark pigments—especially black, dark blue, purple, and metallic polishes—absorb light wavelengths, producing falsely low readings. Action: Remove nail polish using an acetone wipe, turn the sensor sideways across the finger pad, or place the sensor on an earlobe or toe.
3. Shivering and Motion Artifact: Tremors, seizure activity, or shivering create optical noise. Action: Secure the sensor cable to prevent movement, or use an earlobe or forehead reflectance sensor.
4. Bright Ambient Light: Direct overhead surgical lights, phototherapy lamps, or bright sunlight can flood the photodetector. Action: Cover the sensor with a towel or opaque blanket.
5. The Carbon Monoxide (CO) Poisoning Trap: Standard two-wavelength pulse oximeters cannot distinguish carboxyhemoglobin (carbon monoxide bound to hemoglobin) from oxyhemoglobin. Carbon monoxide binds to hemoglobin with an affinity 200 times greater than oxygen. In a patient with carbon monoxide toxicity (from smoke inhalation or furnace leaks), the pulse oximeter will display a falsely reassuring, normal SpO2 of 99% to 100%, even though the patient is experiencing profound, lethal cellular hypoxia. Clinical Rule: In suspected CO poisoning, pulse oximetry is invalid; arterial blood gas analysis with co-oximetry is mandatory.

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5. Tracheostomy Care & Airway Support within PCT Scope

A tracheostomy is a surgically created opening (stoma) in the anterior trachea below the vocal cords to establish an artificial airway for long-term mechanical ventilation, upper airway obstruction, or secretion management.

Anatomical Components of a Tracheostomy Tube

• Outer Cannula: The permanent external shaft that maintains the anatomical patency of the tracheal stoma. It has a faceplate (flange) that rests flush against the patient's neck with slots for securing ties.
• Inner Cannula: Fits snugly inside the outer cannula and locks into place. It can be removed for regular cleaning (reusable inner cannula) or discarded and replaced (disposable inner cannula) to prevent mucus accumulation and airway obstruction.
• Obturator: A solid, bullet-shaped plastic stylet with a smooth, rounded tip used only during the initial insertion of the tracheostomy tube. It guides the outer cannula smoothly through the stoma into the trachea without tearing tracheal rings. Once the tube is in place, the obturator is immediately withdrawn so air can pass.
  • The Mandatory Bedside Obturator Rule: The obturator belonging to the patient's specific tracheostomy tube must be kept in a clear, sealed plastic bag taped securely to the head of the bed or kept on the bedside table AT ALL TIMES. If the tracheostomy tube is accidentally dislodged (decannulated), the nurse or physician must have immediate access to the exact obturator to reinsert the tube before the tracheal stoma spasms and collapses.
• Neck Ties / Tracheostomy Collar: Soft Velcro collars or twill tapes that encircle the neck and secure the flange firmly in place. Always ensure one flat finger fits between the neck and the collar.

Scope of Practice Boundaries for Patient Care Technicians

Clinical regulations and state practice acts strictly delineate what a PCT may and may not perform regarding artificial airways:

• PERMITTED PCT Actions:
  • Providing routine oral hygiene and brushing teeth.
  • Inspecting peri-stomal skin for erythema, maceration, or purulent drainage during routine care.
  • Performing superficial oral and oropharyngeal suctioning using a rigid tonsil-tip (Yankauer) suction catheter to clear pooled secretions from the mouth and back of the throat.
  • Replacing pre-cut tracheostomy drain sponges (split gauze dressings) beneath the faceplate.
  • Assisting the registered nurse during tracheostomy care by holding the outer cannula faceplate securely against the neck while the nurse changes ties.
• PROHIBITED PCT Actions:
  • DEEP TRACHEAL / ENDOTRACHEAL SUCTIONING is strictly outside the PCT scope of practice. Inserting a flexible suction catheter into the tracheostomy tube down into the trachea or bronchi is an invasive, sterile procedure requiring continuous clinical assessment of heart rate, oxygenation, and airway trauma. Deep suctioning is reserved exclusively for the Registered Nurse (RN) and Respiratory Therapist (RT).
  • Cutting Standard Gauze: Technicians must NEVER cut standard woven 4x4 gauze sponges to place beneath a tracheostomy flange. Cut gauze frays, shedding tiny loose cotton fibers and lint that can be aspirated directly into the stoma, causing a foreign-body reaction, granulomas, or fatal bronchial obstruction. Only commercially manufactured, pre-cut, bound-edge tracheostomy drain sponges may be used.

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6. Clinical Scenarios & Practice Traps

Bedside Scenario: The Petroleum Jelly Trap

A technician is performing morning care on an 86-year-old patient with congestive heart failure who is receiving oxygen at 3 L/min via nasal cannula. The patient complains that the plastic prongs are irritating the nares, which are dry and bleeding slightly. The technician finds a jar of petroleum jelly in the bedside drawer and prepares to apply it liberally inside both nostrils.

• Clinical Trap: Applying petroleum jelly or oil-based ointment to skin or mucous membranes in contact with oxygen.
• Pathology: Hydrocarbons in petroleum jelly accelerate combustion. If an electrostatic spark occurs (e.g., from bedsheets), a localized flash fire can ignite, causing severe facial disfigurement and inhalation burns. Additionally, petroleum aspirated into the lungs causes lipoid pneumonia.
• Correct Action: Do not use petroleum jelly. Apply a water-soluble lubricant or water-based saline gel to the nares. Check with the nurse about adding bubble humidification to the oxygen flow meter.

Bedside Scenario: The Collapsing Reservoir Bag

A technician enters the room of a patient receiving oxygen via a non-rebreather mask for acute hypoxemia. With every inhalation, the reservoir bag collapses completely flat, and the patient appears anxious, tachypneic, and is using accessory intercostal muscles. The technician notes the wall flow meter is set at 4 L/min.

• Clinical Trap: Setting a non-rebreather mask at low flow rates.
• Pathology: A non-rebreather mask has one-way valves that seal off room air. If the oxygen flow rate is too low to keep the reservoir bag inflated, the patient is breathing trapped air inside the mask and suffocating, leading to severe hypercapnia and cardiac arrest.
• Correct Action: Immediately turn the flow meter up to 10 to 15 L/min until the reservoir bag fills and stays at least 1/2 to 2/3 inflated during inspiration. Alert the registered nurse immediately to assess the patient.