12 - Therapeutic Medical Gases

causes of hypoxemia

• low atmospheric O₂ in blood (high altitudes)

• alveolar hypoventilation

• V/Q mismatch

• right-to-left shunt

manifestations of hypoxemia

• tachycardia

• HTN (systemic/pulmonary)

• tachypnea

• cerebral/coronary vasodilation

• restlessness

• agitation

• confusion

• cyanosis

• diaphoresis

• pallor

• secondary polycythemia

types of hypoxia

• hypoxemic

• anemic

• stagnant/circulatory

• histotoxic

• demand (tissue demand > supply)

oxygen administration devices

• low-flow

flow systems in which patient breathes portion of total amount of inspiratory flow (< 30 L/min)

• examples: nasal cannula, simple mask, non-rebreather mask

oxygen administration devices

• high-flow

flow systems that meet/exceed patient’s inspiratory flow (> 30 L/min)

• examples: air entrainment mask (Venturi, jet mixing mask), large volume nebulizers

hazards of O₂ therapy

• O₂ toxicity

• retinopathy of prematurity (ROP)

• absorption atelectasis

• environmental factors

administration of helium-oxygen (heliox)

• mixtures: 80/20, 70/30

• administered with non-rebreather

• side effects:

  • high-pitch voice

  • diminished cough effectiveness

nitric oxide (NO)

therapeutic gas that:

• lowers PHTN

• reduces pulmonary vascular resistance (PVR) with no change in systemic vascular resistance (SVR)

• enhances right heart function

• improves artery oxygenation by enhancing V/Q ratio

inhaled NO (iNO) administration and dosage

• treats increased PVR

• vasodilator

• unit: parts per million (ppm)

  • usual dose: 20-80 ppm

• devices: INOmax®, Genosyl®, NOxBOX_i®

indications for iNO

• increased PVR secondary to severe PHTN

• persistent PHTN of newborn (PPHN)

• ARDS

• other condition that results in increased PVR

monitoring iNO therapy

• monitor metHb, NO₂, NO₃

• wean in small amounts to avoid rebound PHTN