Respiratory Therapy Review

Overview of Key Concepts in Respiratory Therapy

Helium and Heliox

  • Helium Characteristics

    • Colorless and tasteless gas used in certain medical applications.

    • Must be combined with oxygen for therapeutic use to prevent suffocation, as it doesn't bind with hemoglobin effectively.

  • Heliox Mixture

    • Typically consists of 80% helium and 20% oxygen.

    • Used as a carrier gas in obstructed airways due to its low atomic weight, allowing it to travel quickly and easily.

Nitric Oxide and its Applications

  • Nitric Oxide (NO)

    • Used as treatment for pulmonary hypertension.

    • Toxic level for nitric oxide (and nitrogen dioxide) is considered to be five parts per million (ppm).

Hyperbaric Therapy

  • Definition

    • Hyper = excessive; Baric = pressure.

  • Alveolar Air

    • Total pressure at sea level: 760 mmHg (atmospheric pressure).

    • Adjusting for water vapor: 760 mmHg - 47 mmHg (water vapor pressure) = 713 mmHg.

  • Use Cases

    • Beneficial for patients with foot wounds, diabetic ulcers, or carbon monoxide poisoning.

  • Physiological Effects

    • Raises partial pressure of gases, allowing improved oxygenation.

    • Improves dissolved oxygen in blood.

  • Pressure Levels

    • Maximum safe operational levels in hyperbaric therapy usually capped at 3 atmospheres.

    • Calculations: 760 mmHg x Pressure Level (1, 2, or 3 atmospheres) results in higher total pressures available for gas exchange.

Gas Exchange and Breathing Mechanics

  • Oxygen Transport

    • Oxygen is carried by hemoglobin (1.34 mL O2 per gram of hemoglobin).

    • Also exists in dissolved form (0.003 mL O2 per mmHg partial pressure).

  • Role of Respiratory Rate and Tidal Volume

    • Increasing respiratory rate increases minute volume but can decrease FiO2 due to more room air being inhaled.

    • Decreasing tidal volume while increasing respiratory rate can alter oxygen delivery (FiO2).

Oxygen Devices and Masks

  • Venti Masks

    • Can deliver FiO2 up to 50%.

    • Adjustments can be made for oxygen concentration by adding reservoirs or decreasing minute volume.

  • Low vs. High Flow Devices

    • Low flow devices are variable; High flow devices are stable and meet the patient’s inspiratory flow demands.

  • Oxygen Toxicity

    • Maximum exposure to 100% oxygen should not exceed 24 hours to avoid lung injury and atelectasis.

  • Documentation Criteria for Hypoxemia

    • Defined as PO2 < 60 mmHg or SpO2 < 90%. Documented hypoxemia must be clearly noted.

Oxygen and Pulmonary Conditions

  • Vasodilatory Effects of Oxygen

    • Oxygen therapy causes vasodilation in pulmonary vasculature, enhancing blood flow in hypoxic conditions.

  • Pulmonary Hypertension

    • Related to chronic low PO2 levels leading to vasoconstriction and cor pulmonale (right heart failure due to lung issues).

Flow Meters in Oxygen Therapy

  • Compensated vs. Uncompensated Flow Meters

    • Compensated meters adjust flow readings in response to pressure changes, ensuring accurate delivery.

    • Uncompensated meters do not reflect accurate flow during occlusion.

Medical Gases and Cylinder Safety

  • Oxygen Purity Standards

    • The FDA standards for oxygen purity require 99% oxygen concentration.

  • Cylinder Safety Regulations

    • Gas cylinders must undergo safety testing every 5-10 years, with seamless construction to withstand pressure.

    • PISS and DISS systems are defined for safe attachment of medical gases.

Oxygen Administration Guidelines

  • Adjustments for Pediatric Patients

    • Caution against maintaining PAO2 above 80 mmHg to prevent retinopathy of prematurity.

Summary of Important Equations and Principles

  • Alveolar Air Equation: Remember important variables and the need for calculations in tests relating to gas exchange.

  • Understanding Relationships: Be mindful of how changes in respiratory rates, tidal volumes, and minute volumes affect oxygenation and delivery.

  • Key Values: Ensure familiarity with numerical values that indicate safety limits and effective treatment ranges.