Medical Gas Therapy: Low-Flow System

Chapter 42: Medical Gas Therapy - Low-Flow System

• Learning Objectives (1 of 3):
  • Describe when oxygen (O2) therapy is needed.
  • Assess the need for O2 therapy.
  • Describe precautions and complications associated with O2 therapy.
  • Select an appropriate O2 delivery system for the respiratory care plan.

Learning Objectives (2 of 3)

• Describe how to administer O2 to adults, children, and infants.
• Describe how to identify and correct malfunctions of O2 delivery systems.
• Assess and monitor a patient's response to O2 therapy.
• Describe how and when to modify or recommend modifications to O2 therapy.

Learning Objectives (3 of 3)

• Describe how to implement protocol-based O2 therapy.
• Identify the indications, complications, and hazards of hyperbaric O2 therapy.
• Identify when and how to administer specialty therapeutic gases.

Oxygen Therapy

• The overall goal of O2 therapy is to maintain adequate tissue oxygenation and minimize cardiopulmonary work.
• Clinical objectives for O2 therapy include correcting documented or suspected acute hypoxemia, decreasing symptoms associated with chronic hypoxemia, and decreasing the workload hypoxemia imposes on the cardiopulmonary system.

Assessing the Need for Oxygen Therapy

• Indications: Documented or suspected hypoxemia (PaO2 less than 60 mm Hg or SaO2 less than 90% breathing room air, or PaO2 or SaO2 below desirable range)
• Additional indications: Severe trauma, acute myocardial infarction (MI), post-op (short-term therapy or surgical intervention, e.g., postanesthesia recovery).

Clinical Signs of Hypoxia

• Mild to Moderate: Tachypnea, Dyspnea, Paleness, Tachycardia, Mild hypertension, Peripheral vasoconstriction, Restlessness, Disorientation, Headaches, Lassitude
• Severe: Tachypnea, Dyspnea, Cyanosis, Tachycardia, eventual bradycardia, arrhythmia, Hypertension and eventual hypotension, Somnolence, Confusion, Distressed appearance, Blurred vision, Tunnel vision, Loss of coordination, Impaired judgment, Slow reaction time, Manic-depressive activity, Coma.

Hazards of Oxygen Therapy

• Ventilatory Depression: Occurs in COPD patients with chronic hypercapnia.
• Absorption Atelectasis: FIO2 > 50% may cause atelectasis due to oxygen replacing nitrogen, a risk for patients breathing small tidal volumes.
• Retinopathy of Prematurity (ROP): Excessive blood O2 levels cause retinal vasoconstriction and necrosis.
• Oxygen Toxicity: Primarily affects the lungs and central nervous system, determining factors include PO2 and exposure time. Prolonged exposure to high FIO2 can cause lung parenchyma infiltrates.
• Fire Hazard: Fires in O2-enriched environments continue to occur. Practitioners in surgery suites and those administering hyperbaric O2 therapy have increased risk.
• Contamination: Risk of contamination.

Precautions & Hazards of Supplemental O2 (cont.)

• Depression of ventilation: Occurs in COPD patients with chronic hypercapnia.
• Absorption atelectasis: Can occur with FIO2 above 0.50; patients breathing small tidal volumes at greatest risk

Low-Flow Systems (Variable Performance)

• FiO2 can vary with patient's respiratory rate and pattern, flow of gas from the equipment, and equipment reservoir.
• Doesn't fully meet patient's inspiratory demand, requiring additional mixing with room air.
• Devices include nasal cannula, nasal catheter, and transtracheal catheters.

Oxygen Delivery Systems: (cont.)

• Nasal Cannula: Delivers FiO2 of 0.24 to 0.40, used with flow rates of 1 to 8 L/min. FiO2 depends on room air inhaled. Humidifier usually needed when input flow is more than 4 L/min.
• Nasal Catheter: Generally limited to short-term O2 administration during specialized procedures (bronchoscopy). Delivers FiO2 of 0.22 to 0.45, and should be replaced with a new one at least every 8 hours.
• Transtracheal Catheter: Surgically placed in trachea by physician. Uses 40% to 60% less O2 to achieve the same PaO2 as nasal cannula; used with flow rates of 1 to 4 L/min, requires careful maintenance and cleaning.
• Performance Characteristics: Concentration varies with air dilution, each 1 L/min of nasal O2 increases approximately 4% FiO2. Increased FIO2 results from higher O2 input, mouth-closed breathing, low inspiratory flow, low tidal volume, slow rate of breathing, small minute ventilation, long inspiratory time, and high I:E ratio.
• Troubleshooting: Common problems include inaccurate flow, system leaks and obstructions, device displacement, and skin irritation (particularly with flowmeters less than 3 L/min)

Reservoir Systems

• Conserves oxygen; nasal and pendant reservoirs.
• Reduce oxygen use by 50% to 75%.
• Humidification usually not needed.
• Systems include simple masks, partial rebreathing masks, and non-rebreathing masks
• Simple Mask: Input flow range 5 to 10 L/min; FiO2 range is 0.35 to 0.50; air dilution easily occurs during inspiration.
• Partial Rebreathing Mask: Input flow range minimum of 10lpm, prevents bag collapse; FiO2 range 0.40 to 0.70.
• Nonrebreathing Mask: More commonly used than partial rebreathing mask, input flow range minimum of 10 L/min, and a FiO2 range of 0.60 to 0.80, Prevents rebreathing with one-way valves.

Troubleshooting Reservoir Systems

• Common Problems: Device displacement, system leaks and obstructions, improper flow adjustment, skin irritation.

Oxygen Conservation Device

• Delivers oxygen only during inspiration.
• Can be used with nasal cannulas, nasal catheters, and transtracheal oxygen catheters.
• Delivers flows equivalent to 1 to 5 L/min.

High Flow Systems

• Provides fixed performance; provides flow rate adequate to meet patients' inspiratory flow needs.
• Provides relatively constant FIO2 by supplying all required gases without further room air dilution.
• Includes entrainment masks (Venturi masks), oxygen hoods, incubators, oxygen tents, high-volume aerosol and humidifiers.

Air Entrainment Mask (Venturi Mask)

• Oxygen delivered through an orifice, increasing flow rate.
• A pressure decrease on the other side of the orifice causes air to be entrained from the atmosphere.
• The oxygen and air mixes to obtain precise concentration. A primary application, providing oxygen therapy for patients with COPD.

Oxygen Hoods

• Encloses infant's head.
• The best method for delivering oxygen to infants.
• The FiO2 monitoring level is the same as the infant's nose.
• Noise levels can be problematic.

Incubators

• Regulate temperature, humidity, and FiO2 of infant's environment. -Include port to regulate FiO2; If port is open, FiO2 is 0.40 or less. If port is closed, FiO2 is 0.40 or higher. -FiO2 inside incubator can vary significantly due to opening chamber for nursing care. Hood inside incubator may be necessary to maintain consistent FiO2.

Oxygen Tents

• A frame and large soft plastic material encloses the patient, used in pediatrics, especially with croup.
• Tents receive oxygen from a high-flow aerosol system.
• FiO2 is difficult to control due to large volume.

Oxygen Blenders and Mixers

• Mixes 50 psig source of oxygen and air to obtain precise FiO2.
• Alarms signal failure of either compressed gas source.
• Pressure change of 10 psig will activate an alarm.

Other Oxygen Delivery Devices

• Various devices for oxygen delivery. (Images shown, but specifics are not provided in this document).

Table 41-8: Oxygen Delivery System Selection

• Selection of an oxygen delivery system is based on the desired FiO2 level and stability. This table assists in choosing appropriate devices based on the intended FiO2 levels (Fixed vs. Variable) and the specific needs of the patients (low, moderate, or high). A table of oxygen delivery systems based on desired oxygen concentration (low, moderate, high) and stability needed.

This quiz covers Chapter 42 of Medical Gas Therapy, focusing on low-flow oxygen delivery systems. You'll learn the indications for oxygen therapy, how to administer it for various age groups, and the precautions involved. Assess your knowledge on assessing patients' needs and correcting delivery system malfunctions.