O2 Delivery

Non-Invasive Delivery of Supplemental Oxygen

Overview

Presenter: Rebecca Pham, PT, DPT, CCSThis presentation aims to explore the significance of supplemental oxygen delivery, particularly focusing on the non-invasive methods that can enhance patient outcomes in various respiratory conditions.

Review of Pulmonary Anatomy & Physiology

Understanding the components and functions of the respiratory system is crucial in relation to oxygen therapy. The lungs facilitate gas exchange; oxygen is absorbed into the bloodstream while carbon dioxide is expelled.

Guiding Questions Set 1

Definitions:

  • Mechanical Ventilation: A medical intervention involving a machine to assist or replace spontaneous breathing, moving air in and out of the lungs to ensure adequate gas exchange.

  • Alveolar Ventilation: The portion of the respiratory cycle that contributes to gas exchange; it represents the airflow to the alveoli, where oxygen and carbon dioxide are exchanged.

  • Oxygenation: The process of loading oxygen onto hemoglobin in the blood, crucial for sufficiency in tissue metabolism.

  • Respiration: The biological process where gas exchange occurs—oxygen is inhaled and carbon dioxide is exhaled.

  • Oxygen Delivery: The efficiency of transporting oxygen from the lungs through the circulatory system to tissues throughout the body.

  • Oxygen Consumption: The rate at which oxygen is utilized by tissues during metabolic processes.

Key Terms:

  • FiO2: Fraction of inspired oxygen; room air contains approximately 21% oxygen. In clinical settings, oxygen levels can be adjusted to meet patient needs.

  • SaO2: Arterial oxygen saturation; a measure of how much oxygen the blood is carrying as a percentage of the maximum it could carry, typically assessed through pulse oximetry or arterial blood gas testing.

  • SpO2: Non-invasive pulse oximetry measurement of arterial oxygen saturation, providing a quick assessment but with known limitations.

  • PaO2: Tension of oxygen in arterial blood; lower values indicate inadequate oxygenation and may necessitate intervention.

  • PaCO2: Tension of carbon dioxide in arterial blood; an important marker for assessing ventilation adequacy and may indicate respiratory failure if elevated.

  • Minute Ventilation (MV): The total volume of gas entering or leaving the lungs per minute. It is calculated as Tidal Volume (TV) multiplied by the Respiratory Rate (RR). This measure is pivotal in evaluating the effectiveness of a patient’s breathing pattern.

Hypoxemia vs. Hypoxia:

  • Hypoxemia: Characterized by a deficiency of oxygen in the bloodstream, it can be diagnosed using blood gas analysis.

  • Hypoxia: Refers to low oxygen availability in tissues; it can persist even with normal blood oxygen levels and is critical to address to prevent cellular injury or organ damage.

Oxygen Therapy:

Indicated to prevent or correct hypoxia, oxygen therapy requires a physician’s order. It encompasses various methods to augment the concentration of oxygen in the inspired air, aiming to enhance arterial oxygen tension (PaO2) and improve saturation levels (SaO2).

Indications:

  • Hypoxemia defined as SpO2 <90% or PaO2 <60%.

  • Noticeable increased work of breathing and myocardial demand, which may indicate the need for supplemental support.

  • Refractory Hypoxemia: A persistent lack of adequate oxygenation that does not respond effectively to supplemental oxygen.

Respiratory System Pathway of Air:

The flow of air follows a clear pathway: Nose -> Nasal Cavity -> Pharynx -> Larynx -> Trachea -> Bronchi -> Alveoli. Each anatomical structure plays a vital role in filtering, warming, and humidifying the air before it reaches the alveoli for gas exchange.

Oxygen Vocabulary: General Concepts

  • Gas Exchange: Involves both ventilation (the actual movement of air into and out of the lungs) and oxygenation (the loading of oxygen from air into blood).

  • Understanding oxygen delivery and consumption rates is essential for accurate respiratory function assessment and monitoring.

Important Terms for Oxygen Therapy

  • Definitions:

    • Hypoxemia: Insufficient oxygen in arterial blood, identified through specific saturation metrics.

    • Hypoxia: Insufficient oxygen in target tissues or organs despite possibly normal blood oxygen levels.

    • FiO2: Varies according to the additional methods of oxygen delivery.

Oxygen Therapy Definition

Increasing the concentration of oxygen in inspired air is fundamental for preventing or correcting hypoxia. Successful oxygen therapy aims to improve both PAO2 (Alveolar Oxygen Tension) and PaO2, which fundamentally enhances SaO2 (Oxygen Saturation) levels in the bloodstream.

Indications for Supplemental Oxygen

Supplemental oxygen is typically indicated when SpO2 falls below 90%, with further subdivision of hypoxemia severity:

  • Mild Hypoxemia: PaO2 70-79 mmHg.

  • Moderate Hypoxemia: PaO2 60-69 mmHg.

  • Severe Hypoxemia: PaO2 50-59 mmHg.

  • Extreme Hypoxemia: PaO2 <50 mmHg.

Causes of Hypoxemia

Typical causes include:

  • Alveolar Hypoventilation: Reduced airflow may reduce oxygen intake.

  • Diffusion Defects: Impairment in the transfer of gases between alveoli and blood.

  • Circulation Defects: Problems with blood flow may affect oxygen delivery.

  • Anemia: Reduced hemoglobin levels impair oxygen transport capacity.

  • Refractory Hypoxemia: Persistent hypoxemia that does not improve even with oxygen supplementation.

Effects of Supplemental Oxygen

Supplemental oxygen has numerous benefits:

  • Increases exercise tolerance and reduces the sensation of dyspnea (shortness of breath).

  • Enhances minute ventilation and optimizes muscle function, while reducing hypoxic pulmonary vasoconstriction, which can lead to improved pulmonary blood flow and oxygenation.

Oxygen Delivery Systems

Types:

  1. Low-Flow Systems: Deliver oxygen at flow rates less than 8 L/min, and the FiO2 can vary considerably—typical examples include nasal cannulas.

  2. Reservoir Systems: Capable of delivering higher FiO2, potentially up to approximately 80-100%. Simple face masks are common examples.

  3. High-Flow Systems: These provide a set or fixed FiO2 at higher flow rates, generally exceeding 15 L/min, which is particularly useful in specific patient populations needing consistent oxygenation.

Flow & FiO2 Relationship

The relationship between flow rate and FiO2 is critical to the effectiveness of oxygen delivery. The delivered FiO2 can vary significantly depending on the specific device in use and the individual patient’s breathing mechanics.

Device Classifications

  • Low-Flow Systems: Typically deliver flows less than 8 L/min, exhibiting variable FiO2 concentrations; suitable for less severe hypoxemia cases and providing an easy-to-use option for patients.

  • Reservoir Systems: Deliver higher FiO2 (up to ~80-100%), allowing for short bursts of higher oxygen concentration for patients who may not require constant high-flow oxygen.

  • High-Flow Systems: Offer a precise and unchanging FiO2 regardless of patient breathing patterns while providing flow rates above 15 L/min, ideal for those needing stable oxygen levels.

Role of Physical Therapists

Physical therapists are becoming recognized as potential oxygen titrators, empowered to assess and regulate oxygen saturation levels during both rest and activity. This role is essential in providing comprehensive care for patients with various respiratory conditions.

Medicare Coverage

There are specific criteria for Medicare coverage based on clinical indicators such as PaO2 and SpO2 measurements, highlighting the importance of adequate documentation and adherence to guidelines for the provision of supplemental oxygen to patients.

Summary & Conclusion

A thorough understanding of oxygen therapy is pivotal in managing patients with respiratory issues. Each oxygen delivery device has unique properties and caters to specific clinical scenarios based on patient need, thus ensuring optimal treatment outcomes in various healthcare settings.