Medical Gas Therapy

  1. Correct documented or suspected acute hypoxemia (pneumonia, V/Q mismatch

  2. Decrease WOB associated w chronic hypoxemia (COPD and ILD patients report less dyspnea w O2 therapy)

  3. Decreased workload hypoxemia imposes on cardiopulmonary system (MI, pulmonary edema)

Mild hypoxemia- 60-80

Moderate hypoxemia- 40-60

Severe hypoxemia- <40

Peripheral vasodilation- patient may be warm

Pulmonary vasoconstriction- shunting in the lung increase PVR

Cerebral hypoxia causes patient to be confused

Assessing need for O2 therapy

  1. Lab documentation for adult/child is PaO2 <60 mmhg, SaO2 <90%, SpO2 <93%

  2. An acute care situation in which hypoxemia is suspected (patient suspected of carbon monoxide poisoning )

  3. Sever trauma

  4. Acute MI

  5. Surgical intervention

  • Oxygen toxicity

    • Primarily affected lungs and central nervous -O2 is not likely to affect kidneys like vent issues

    • Patients at risk when they receive high Fio2 >50% for periods of >24 hours

Retinopathy of Prematurity- blindness occurring in premature infants and newborns as a result of high PaO2

In NICU a PaO2 goal of <80mmHg

ROC- return of circulation

COPDers and Blunted Hypoxic Drive (depression of ventilation)

–Central Chemoreceptors are blunted due to chronic increased CO2

–Peripheral Chemoreceptors are back up.  However, increase the PaO2 and it blunts peripheral chemoreceptors, which in turns increases their PCO2

Signs: Decreased RR and VT, increased PaO2, Increased PaCO2, decreased pH, patient sensorium – lethargic, sleepy, confused

High O2 because we are over oxygenating them

Giving a patient a precise amount of oxygen we use a Venturi mask for COPD patients so they have a precise amount of FiO2

Absorption Atelectasis

  • Can occur with FiO2 above .50

  • Gradually change FiO2 n 5-10% increments

To much oxygen to a patient can lead to absorption atelectasis this can lead to alveoli becoming to filled and pressure causes it to collapse

Oxygen can be administered with nebulizers and humidification systems

•Signs & Symptoms patient is experiencing hazardous effects:

–Nausea and vomiting

–Substernal chest pain and tightness

–Refractory hypoxemia

–Tachypnea

–Decreased surfactant production

–Decreased compliance

–Pulmonary edema

Remember: Oxygen is considered a drug with therapeutic effect but is given without conclusive timeframe like pharmacological agents

When deciding which O2 device select for your patient it is your responsibility to understand the properties and individual capabilities of the device/equipment

Low flow systems (.5-5L) nasal cannula

Mid flow- 6-15

High flow 15>

2L=humidification

Anything under 85% you want to give the best flow (nonrebreather mask)

Appropriate choices are~ Blood gases/pulse ox, RR, VT, Ventilatory pattern, patient cooperation

CPAP= oxygenation issues BiPAP= ventilatory issues (inspiratory pressure and expiratory pressure)

  • If oxygen therapy is correctly implemented it will

    • Decrease ventilatory demand

    • Decease work of breathing (WOB)

    • Decrease cardiac output (CO)

•Nasal cannula (excluding High-flow version discussed later)

–Appropriate for stable COPD patients with stable RR and VT

—Delivers FiO2 of 0.22 to 0.40 (24%-44% per rule of 4)

—Used with flow rates of ¼ to 6 L/min

–FIO2 depends on how much room air patient inhales in addition to O2

Bubble humidifier may be added. Typically initiated when patient is on >2 LPM oxygen, also for anybody on a prolonged device

RA= 21% FiO2 Ex. 1L=24% 2L= 28% 3L=32% 4L=36% 5L=50% 6L=44%

Trans tracheal catheter~

-surgically placed in trachea through neck

-uses 40-60% less O2 to achieve same PaO2 by nasal cannula

-provides 22%-35% fiO2

Reservoir cannula aka oxymizer designed to conserve oxygen, can reduce oxygen use as much as 50-75%, “cuts flow in half” humidification not needed, holds 20ml of oxygen

Patients breathing pattern as well as their anatomy (size of nares) affects how oxymizer works

Trouble shooting low flow devices

•Inaccurate flow is the biggest concern with reservoir devices. If flow is <5 L/min, masks/reservoirs act as dead space. This causes CO2 rebreathing.

•System leaks

•Obstructions

•Device displacement

  • Skin irritation

Reservoir Masks~

•Simple mask

–Minimum 5-10 LPM/35-50% Variable FiO2

•Partial rebreathing mask

–minimum 10 LPM / 40-70% Variable FiO2

•Nonrebreathing mask

–minimum 10 LPM 60-80%

-Flow to prevent bag from collapsing on inspiration

With Reservoir Devices:

•Patient exhales through the exhalation ports

•Minimum 5 LPM flow otherwise patient will re-breathe CO2

•Variable FIO2 because the air is diluted during inspiration

Partial rebreather vs non rebreather is non rebreather has a valve

Trouble shooting reservoir system

•Flow rates must be sufficient enough to keep bag from collapsing

–If bag collapses, increase flow

–If patient inhales and bag does not slightly contract:  mask is not tight, seal mask, NRB valve is stuck, replace mask

•Obstructions

•Improper flow adjustment

  • Skin irritation

To qualify as a high flow device the system should provide at least 60 L/min flow

Air Entrainment Mask (AEM) aka Venturi mask

•OXYGEN DELIVERY IS BASED ON FIXED JET SIZE COUPLED WITH A FIXED ENTRAINMENT PORT. SYSTEM FLOW DOES NOT EFFECT FI02

Smaller orifice= increased velocity= more air entrained= decreased FiO2

Larger orifice= decreased velocity= less air entrained= increased FiO2

Ideal for patients with irregular VT and breathing patterns

If entrainment port is occluded clean it out

•The actual FiO2 delivered to the patient does not depend on oxygen gas flow from the jet port.

What does is the 1) air-to-oxygen ratio of the device and 2) any resistance downstream from the jet.

Oxygen hood aka oxyhood: generally best method for delivering precise oxygen to infants

Use a low flow of about 7 LPM but no higher than 10 LPM

Bag-mask device provide 100% FiO2 often during emergencies

PEEP= positive end expiratory pressure

Peep keeps the alveoli open by applying pressure

Patient must be spontaneously breathing they have to be able to maintain their own minute ventilation and they have to maintain their own RR otherwise intubate

Oxygen therapy device selection

Low (<35%)

  • Fixed AEM, AEM neb, blending system, isolette

  • Variable nasal cannula, nasal catheter, trans tracheal catheter, OxyMask

Moderate (35%-60%)

  • Fixed AEM, AEM neb, oxyhood, high flow nasal cannula

  • Variable fixed AEM, tent, nasal cannula with reservoir, oxymask

High (>60%)

  • Fixed AEM, AEM neb, oxyhood, high flow nasal cannula

  • Variable partial rebreather, non-rebreather, oxymask

*oxymask- mask device with widest range of FiO2 and liter flow

Common acute conditions for hyperbaric chamber

  1. Air embolism

  2. Carbon monoxide poisoning

Nitric Oxide therapy

-improves blood flow to lung

-reduces shunting

-improves oxygenation

Nitric oxide therapy~

  • ARDS

  • COPD

  • Sickle cell disease

  • Cardiac transplant

Rebound affect can be dangerous causing hypoxia for nitric oxide therapy

-reduce NO to its lowest effective dose (5ppm)

-hyper-oxygenate patient before discontinuation

-ensure patient is hemodynamically stable

Helium comes in a brown tank

Helium can decrease WOB for patients w airway obstructions

*in general Heliox should be delivered to patients via tight fitting non rebreather mask w high flow

Carbon dioxide-oxygen is not a common gas

Pulse oximeters are based on light absorption resulting from arterial blood flow pulsations