Oxygen Therapy 3o681q

By Dr Riham Hazem Raafat, MD Ainshams University

KEEP IN MIND High levels of oxygen in the blood and tissue

can be helpful or damaging depending on circumstances

Definitions -Oxygen is a colorless, odorless, tasteless gas that is essential for the body to function properly and to survive. -Oxygen therapy is the istration of oxygen at a concentration of pressure greater than that found in the environmental atmosphere. -The air that we breathe contain approximately 21% oxygen. -Oxygen therapy is a key treatment in respiratory care.

- Oxygen therapy refers to the istration of supplemental oxygen

as part of managing illness

- It is the istering of oxygen to patients to correct hypoxemia (low oxygen blood levels) or supplemental oxygen given to a patient as a medical treatment in managing respiratory diseases that alter oxygen supply to tissue cells (hypoxia).

Indications for Oxygen Therapy •Hypoxia- deficiency in the amount of oxygen reaching the tissues,

(Oxygen saturation of <92%).

•Acute and Chronic Hypoxemia- an abnormally low level of oxygen in arterial blood which leads to tissue hypoxia (PaO2 <60mmHg, Oxygen saturation <92%)  increased work of breathing and myocardial overload.

• Peri and post cardiac or respiratory arrest • Post operatively (dependent on instructions from surgical team)

• Respiratory failure • Low cardiac output and metabolic acidosis (HCO3 <18 mmol/L) • Hypermetabolic States (Burns, Trauma, Sepsis)

Causes of Hypoxia Hypoxic (arterial) Hypoxia: Results From: INADEQUATE OXYGENATION OF THE ARTERIAL BLOOD (Hypoxemia) Caused By: a)HYPOVENTILATION  not adequate alveolar ventilation Dec in alveolar and arterial Po2 & increase in alveolar and arterial Pco2 (Hypercapnia)

b)DIFFUSION LIMITATION  diffusion capacity of lungs decreased by a pulmonary disease c)PHYSIOLOGIC SHUNTS [ VA/Q imbalance ] most common cause of hypoxia d)ANATOMIC SHUNTS (mixing of venous and oxygenated (arterial) blood which decreases the Po2)  normally shunt of

Ischemic or Stagnant Hypoxia Results From: To entire body

INADEQUATE BLOOD FLOW or

Caused By: Congestive heart failure

Arterial Po2 may be normal BUT because

Localized area

Arteriosclerosis Q (blood flow), tissues

withdraw larger amounts of O2 from the blood, so Venous Po2

Histotoxic Hypoxia

Anemic Hypoxia

RESULTS FROM:

RESULTS FROM:

DISABILITY OF CELLS TO USE O2

INSUFFICIENT AMOUNT OF FUNCTIONAL HEMOGLOBIN

CAUSED BY: 1)INACTIVATION OF CERTAIN METABOLIC ENZYMES

2)CHEMICAL POISONS Tissues are unable to use O2 so Venous Po2 Increases

CAUSED BY: 1)Deficiency of essential nutrient (Fe, B12) 2)Blood loss Patients with have reduced O2 capacity  reduced content of O2 in blood

Symptoms of Hypoxia Depends on 

RAPIDITY and SEVERITY OF THE DECREASE OF ARTERIAL Po2

1) FULMINANT hypoxia -Arterial Po2 <20mmHg (aircraft loses cabin pressure above 30,000 feet and no supplemental O2 available) -Occurs in seconds -Unconsciousness in 15-20 sec -Brain death in 4-5 min

2) ACUTE hypoxia

3) CHRONIC hypoxia

-25mmHg <40mmHg (altitudes of 18,000-25,000 ft) -Symptoms similar to those of ethyl alcohol (lack of coordination, slowed reflexes, overconfidence) -Unconsciousness -Coma and death (in minutes to hours) if the regulatory mechanisms of the body are inadequate

- 40mmHg <60mmHg (at altitudes of 10,000-18,000 feet for extended periods of time) - Most clinical causes of hypoxia are in these category - Symptoms similar to those of severe fatigue DYSPNEA + RESPIRATORY ARRHYTHMIAS

Clinical Manifestations of Hypoxia • Impaired judgment, agitation (restlessness), disorientation, confusion, lethargy, coma • Dyspnea • Tachypnea (arterial chemoreceptor reflex response to Po2 dec) • Tachycardia, dysrhythmias (peripheral chemoreceptor reflex response to Po2) • Elevated BP • Diaphoresis • Central cyanosis caused by more than 5g of deoxyhemoglobin/dl in capillary blood (or less than 13ml O2 per 100ml of blood) *NOT RELIABLE SIGN OF HYPOXIA!!! - ANEMIC PATIENTS never develop cyanosis but are extremely hypoxic - PATIENTS WITH POLYCYTHEMIA may be cyanotic but they are perfectly oxygenated

NEED FOR OXYGEN IS ASSESSED BY • Clinical evaluation • Pulse oximetry

• ABG

Goal of therapy - SO2 of >90%

- For documented COPD patients (So2 88–92%)-(Pao2=55-60) - As SO2 normalizes  vital signs should improve • Heart rate should return to normal • Respiratory rate should decrease to normal • Blood pressure should normalize

Sources of Oxygen 1. Oxygen Cylinder. 2. Oxygen Concentrators. 3. Oxygen Wall Outlets.

1- Oxygen Cylinders: • The oxygen cylinder is delivered with a protective cap to prevent accidental force against the cylinder outlet.

• To release oxygen safety and at a desirable rate, a regulator is used.

• A reduction gauge that shows the amount of oxygen in the tank. • A flow meter that regulates the control of oxygen in liters per minutes. • Oxygen is moistened by ing it through a

humidifier to prevent the mucous membranes of the respiratory tree from

2- O2 Concentrator It works by: 1.Taking in air from its surroundings 2.Compressing air, while the cooling mechanism keeps the concentrator from overheating 3.Removing nitrogen from the air via filter and sieve beds

4.Adjusting delivery settings with an electronic interface 5.Delivering the purified oxygen via a nasal cannula or mask

3- Wall – outlet oxygen: • The oxygen is supplied from a central source through a pipeline. • Only a flow meter and a humidifier are required.

Oxygen Delivery Systems 1. Nasal Cannula 2. Simple Mask 3. Partial Re-Breather Mask 4. Non-Re Breather Mask (NRBM) 5. Venturi Mask 6. Oxygen Hood 7. Oxygen Tent 8. AMBU Bag 9. Tracheostomy Collar, 10. T-piece

Oxygen delivery devices are used to deliver oxygen to patients at different concentrations

•Low flow oxygen devices work by supplying oxygen at flow rates less than the patient’s inspiratory flow, usually 1 to 10 liters per minute  The remaining

inspired flow comes from the atmospheric air, diluting the delivered O2. •High flow oxygen devices supply flow rates high enough to accommodate two to three (2-3) times the patient’s inspiratory volume at 1 to 40 liters per

Low Flow (variable performance) •Low flow nasal cannula •Reservoir Systems - Face mask - Nonrebreather mask - Partial rebreather mask •Face tent •Nasal catheter •Trans-tracheal catheter Variable oxygen concentration depending on the MV or PIFR

High Flow (fixed performance) •High flow nasal cannula •Mechanical ventilators •Hyperbaric oxygen chambers •Venturi mask •Tracheostomy collar and T-piece

•Ambu bag Fixed concentration of Oxygen irrespective of the minute volume or PIFR of the patient.

Variables Affecting the Fio2 of Low Flow Oxygen Systems - Increased FiO2 :

- Decreased FiO2

•Higher O2 input, mouth closed

•Lower O2 input

breathing (cannula only). •Low inspiratory flow and low tidal volume

•High I:E ratio. •Slow rate of breathing •Small minute ventilation. •Long inspiratory time.

•Mouth open breathing. •High inspiratory flow and high tidal volume.

•Low I:E ratio. •Fast rate of breathing. •Large minute ventilation •Short inspiratory time.

Nasal cannula (prong) • Consists of a flexible tube that is placed inside the nares.

• It delivers a relatively low concentration of oxygen (21% to 44%) at flow rate 1 to 6 L per minute [1L- 24%, 2L- 28%, 3L- 32%, 4L- 36%, 5L- 40%, 6L- 44% oxygen]

• Rule of thumb- for patients with normal rate and depth of breathing, each liter per min of nasal oxygen increases the Fio2 by 4%. • Humidifier is used only if the input flow exceeds 4L/min.

• Flows greater than 6 to 8L/min can cause patient discomfort including dryness and bleeding. • In newborns and infants flows should be 2L/min or less.

Advantages • Simplicity of use • Patient acceptance

• Ability to eat and talk • Easy home setting

Disadvantages • Inability to achieve high concentration of inhaled O2 • Unable to use with nasal obstruction • Drying to mucous membranes, so flow greater than 4 L/min needs to be humidified

• Can dislodge from nares easily • Causes skin irritation or breakdown over ears or at nares • Not good for mouth breathers, deviated septum, polyps  may reduce Fio2.

• Patient’s breathing pattern affects exact FIO2

Nursing Interventions:

• Be alert for skin breakdown over the ears and in the nostrils from too tight an application • Observe for mucosal dryness • Check frequently that both prongs are in patients nares

Face mask (Hudson Mask) • The simple face mask covers the client nose and mouth but contain port in the body that allows exhale air to escape. • Delivers oxygen concentrations from 40% to 60% at liter flows of 5-10 L per

minute  Flow rate must exceed 5L/min to replace exhaled gas with fresh oxygen otherwise rebreathing of CO2 will occur • Provides low-flow oxygen and is suitable for patients with normal respiratory patterns, rates, and ventilation volumes. • Considered a reservoir system because the mask encloses a volume of 100-200ml

• If O2 input flow cease, the patient can draw in air through these holes and around the mask edge. {5 – 6L/min – 40%, 6 – 7 L/min- 50%, 7 – 8 L/min – 60%}

Advantages

• Slightly higher maximum FiO2 than low flow nasal prongs Disadvantages •

Like nasal prongs, Fio2 varies with the ventilator demand of the Patient

•

Needs tight seal to get higher O2

•

No oral feeding or conversation

•

Often it is used when an increased delivery

•

of oxygen is needed for short periods (< 12 hours)

•

Skin breakdown

Nursing Interventions: • Monitor patient frequently to check placement of the mask.

• Secure physician's order to replace mask with nasal cannula during meal time

Nasal Mask •Hybrid of nasal cannula and face mask.

•Supplemental oxygen equivalent to nasal cannula under low flow conditions for adult patients.

•Advantage – patient comfort, does not produce sores around nares

•Dry oxygen is not jetted into nasal cavity.

Partial Re Breather Mask • The mask is with a reservoir bag that must remain inflated during both

inspiration & expiration • It collects of part of the patients' exhaled air.

• It is used to deliver oxygen concentrations up to 80%. • The oxygen flow rate must be maintained at a minimum of 6 L/min to

ensure that the patient does not re-breathe large amounts of exhaled air. • The remaining exhaled air exits through vents.

Advantages

•Patient can inhale room air through openings in mask if oxygen supply is briefly interrupted Disadvantages •Requires tight seal (eating and talking difficult, uncomfortable)

Nursing Interventions

• Set flow rate so mask remains two thirds full during inspiration • Keep reservoir bag free of twists or kinks

•Non-rebreather mask One-way valves on the mask and between the reservoir bag and the mask prevent the room air and the patient

exhaled air from entering the bag so only the oxygen in • To prevent carbon dioxide build-up, the nonrebreather must not totally the bag isbag inspired. deflate during inspiration. If this occurs, the liter flow of oxygen should be increased. • Delivers the highest oxygen concentration possible 95% to 100% by means other than intubation or mechanical ventilation, at liter flows 10 to 15 L per minute. • It is used in severe hypoxemia to deliver the highest oxygen concentration.

Advantage Ability to deliver higher concentration of inhaled O2

Disadvantages - Impractical for long term Therapy - Malfunction can cause CO2 buildup - suffocation

- Expensive - Uncomfortable - Aerosolized bronchodilator therapy not possible

Nursing Interventions •Maintain flow rate so reservoir bag collapses only slightly during inspiration

•Check that valves and rubber flaps are function properly (open during expiration ) •Monitor SaO2 with pulse oximeter

Venturi mask (air entrainment device) • Has wide-bore tubing and color-coded jet adapters that correspond to a precise oxygen concentration and liter flow.

• Delivers an exact percentage of oxygen regardless of the patient’s tidal volume.

• Oxygen concentrations varying from 24% to 40% or 50% at liter flows of 4 to 10 L per minute. (constant FiO2)

• Used for patients with COPD to maintain constant oxygen concentration.

Advantages •Ability to deliver a constant FiO2 •Desirable in patients with chronic CO2 retention (Inadvertent increase in FiO2- further increase in arterial PCO2)

Disadvantages •Inability to deliver higher concentration of inhaled O2 uncomfortable

Nursing Interventions • Requires careful monitoring to FiO2 at flow rate ordered

• Check that air intake valves are not blocked

Face Tent •Replace oxygen masks when masks are poorly tolerated by the patient. •Oxygen delivery of 21% to 50% depends on

patient breathing (21% delivered with compressed air and up to 50% delivered with 10 L/min oxygen flow attached). •Often used for humidification as well as oxygen delivery in patients who do not like the claustrophobic feeling associated with more traditional masks

AMBU Bag AMBU- Artificial Manual Breathing Unit (or) Bag Valve Mask Ventilation •Is a hand-held device •Commonly used to provide positive pressure ventilation to patients who are not breathing or not breathing adequately.

Tracheostomy Collar/ Mask • Inserted directed into trachea

• Is indicated for chronic O2 therapy need • O2 flow rate 8 to 10L

• Provides accurate FIO2 • Provides good humidity.

• Comfortable ,more efficient

T-Piece •The T-piece is a T-shaped adapter used to provide oxygen to either

an endotracheal or Tracheostomy tube. •The flow rate should be at least 10 L/min with humidification.

•Flow can also be provided by a ventilator. •Used to provide a high-enough flow rate to ensure that there is a

minimal amount of entrained room air.

Trans-tracheal Catheter • A thin polytetrafluoroethylene (Teflon) catheter

• Inserted surgically with a guidewire between 2nd and 3rd tracheal rings • FiO2 – 22-35% • Flow – ¼ - 4L/min (low variable) -> no need to humidifier • Increased anatomic reservoir

Advantages - Lower O2 use and cost - Eliminates nasal and skin irritation - Better compliance - Increased exercise tolerance - Increased mobility

Disadvantages - High cost - Surgical complications - Infection - Mucus plugging - Lost tract

Nasal Catheter • Soft plastic tube with several holes at the tip. • Inserted by advancing along the floor of either nasal age and visualizing it just behind and above the uvula. • Once in position it is taped to the bridge of the nose. • Can be inserted to a depth equal to the distance from the nose to the tragus of either ear. • Flow – ¼ to 8L/min. • Fio2 range – 22% to 45%. • Variable performance system. • Low cost ,good stability, disposable. • Best used in the procedures in which cannula is difficult to use (bronchoscopy).

Disadvantages: • Difficult to insert. • High flow increases back pressure. • Needs regular changing(at least every 8hrs). • Polyps, deviated septum can may block insertion. • May provoke gagging, air swallowing, aspiration.

High Flow Nasal Oxygen Cannula

HYPERBARIC O2 THERAPY •HBO therapy is indicated in compromised O2 carrying capacity of Hb (e.g in CO poisoning) or if extra tissue O2

required (e.g severe burns & tissue infection) • This uses the ability ofisplasma & tissue fluid to accept an increased amount of O2 that is dissolved under pressure • HBO therapy delivers 100% O2 at a pressure above atm, in a pressurized multi

or one-person chamber • Complications of HBO therapy include barotrauma to ears, sinuses & lung, O2 toxicity, grand mal fits & reversible visual changes.

Complications associated with oxygen therapy • Drying of mucous membranes.

• Skin breakdown • Oxygen toxicity • Suppression of ventilation will lead to increased CO2 and narcosis • Potential of contamination and infection to patients. • Retrolental fibroplasia • Absorption atelectasis • Fire Hazard

A) Oxygen Toxicity • It is a condition which occurs due to inspiration of a high concentration of oxygen for a prolonged period of time. • Oxygen concentration greater than 50% over 24 to 48 hours can cause

pathological changes in the lungs. • Oxygen toxicity – can occur with

- Fio2 > 60% longer than 36 hrs - Fio2 > 80% longer than 24 hrs

- Fio2 >100% longer than 12hrs

Primarily affects lung and CNS. By 2 factors: PaO2 & exposure time 1- CNS O2 toxicity (Paul Bert effect)

• Occurs on breathing O2 at pressure > 1 atm • Tremors, twitching, convulsions

2- Pulmonary • Acute trachea-bronchitis • Cough and substernal pain • ARDS like state

PHYSIOLOGIC RESPONSE OF EXPOSURE TO 100% O2 •

EXPOSURE

PHYSIOLOGIC RESPONSE

0 - 12 hrs

Normal pulmonary function Substernal pain Tracheo-bronchitis

•

12 - 14 hrs

Decreasing vital capacity

•

24 – 30 hrs

Decreasing lung compliance Increasing P(A-a)O2 gradient Decreasing exercise PaO2

•

30-72 hrs

Decreasing diffusing capacity

PULMONARY O2 TOXICITY (LORRAIN-SMITH EFFECT) Pathogenesis:

• High pO2 for a prolonged period of time ↓ • Intracellular generation of free radicals e.g.: superoxide,H2O2 , singlet oxygen (anti-oxidants ineffective in high O2) ↓ • React with cellular DNA, sulph-hydryl proteins &lipids ↓ • Cytotoxicity & damages capillary endothelium ↓ • Interstitial edema • Thickened alveolar capillary membrane. • Low V/Q and Shunting then Hyaline membrane formation ↓ • Pulmonary fibrosis and hypertension

• Patients exposed to high Po2 for prolonged period has signs similar to broncho-pneumonia

• CXR- patchy infiltrates prominent in lower lung fields • Underlying the gross clinical signs is a major alveolar injury The GOAL should be to use lowest possible FiO2 with adequate oxygenation

Indications for 70% - 100% Oxygen

1. Resuscitation 2. Periods of acute cardiopulmonary instability 3. Patient transport

B) Depression of Ventilation • Seen in COPD patients with chronic hypercapnia • Mechanism: ↑PaO2 Suppresses peripheral V/Q mismatch Chemoreceptors

depresses ventilatory drive

↑ dead space/tidal volume ↑PaCO2

C) Absorption Atelectasis : • During 100% oxygen delivery, nitrogen in alveoli is washed out and replaced by oxygen.

• In contrast to nitrogen, oxygen is extremely soluble in blood and diffuses very quickly into the pulmonary vasculature, so that not enough gas is left in the alveoli to maintain patency, and the alveolus collapses; this is known as absorption atelectasis -> V/Q mismatch (increase shunt) • The risk of absorption atelectasis is greatest in patients breathing at low tidal volumes e.g. sedation, surgical pain, CNS dysfunction. • In these cases poorly ventilated alveoli become unstable when they loose oxygen faster than it can be replaced. • Result is gradual shrinking of alveoli to complete collapse.

oxygen

A – UNDERVENTILATED B – NORMAL VENTILATED

nitrogen

PO2 =673 PCO2 = 40 PH2O = 47

D) Retinopathy of Prematurity (ROP) • Premature or low-birth-weight infants who receive supplemental O2 • Mechanism ↑PaO2

↓ Retinal vasoconstriction ↓ Necrosis of blood vessels ↓ New vessels formation ↓

Hemorrhage → retinal detachment and blindness • To minimize the risk of ROP - PaO2 below 80 mmHg

E) Fire Hazard: • High FiO2 increases the risk of fire • Preventive measures - Lowest effective FiO2 should be used - Use of scavenging systems - Avoid use of outdated equipment such as aluminium gas regulators • Fire prevention protocols should be followed for hyperbaric O2 therapy

Precautions to be taken to prevent complications • Ensure that humidification system is applied when a patient needs high flow oxygen.

• Inspect the skin for skin integrity impairment and prompt application of barrier creams and cushions. • Ensure that patients are istered the minimal amount of oxygen to achieve and maintain a baseline Partial Pressure of arterial oxygen (PaO2) of 60mmHg. • ister oxygen only when required and use for the shortest time possible.

• Utilize the best Positive end-expiratory pressure (PEEP) and Continuous positive airway pressure (AP) when oxygen therapy is in use to prevent the cellular damages that can occur from oxygen toxicity. • ister oxygen at low flow concentration levels and closely monitor patient’s respiratory status. • Follow manufacturer policy on care and institution policy on infection

control.

Safety Precautions • Oxygen is a highly combustible gas. • Although it does not burn spontaneously or cause an explosion, it can easily cause a fire in a patient’s room if it s a spark from an open flame or electrical equipment

• Oxygen is a therapeutic gas and must be prescribed and adjusted only with a health care provider’s order. • Place an “Oxygen in Use” sign on the patient’s door and in the patient’s room.

• If using oxygen at home, place a sign on the door of the house. • No smoking should be allowed on the premises

• Keep oxygen-delivery systems 10 feet from any open flames.

• Determine that all electrical equipment in the room is functioning correctly. • When using oxygen cylinders, secure them so they do not fall over. Store them upright and either chained or secured in appropriate holders. • Check the oxygen level of portable tanks before transporting a patient to ensure that there is enough oxygen in the tank

Monitoring • CLINICAL ASSESSMENT • PHYSIOLOGIC PARAMETERS – ABG • PaO2, SaO2 AT :o Initiation of therapy o Within 12 hours if initial FiO2 >0.6 o Within 72 hours in acute MI

o Within 2 hours in COPD patients o Within 1 hour for neonates

• EQUIPMENT MONITORING - All oxygen delivery systems should be checked at least once a day - More frequent checks for systems which are : . Susceptible to variation in FiO2 e.g. hood, high flow blending systems . Applied to patients with artificial airways . Delivering a heated gas mixture . Applied to clinically unstable patients requiring FiO2 >0.5

Technique of Oxygen stration

Evaluation -Breathing pattern regular and at normal rate.

-Pink color in nail beds, lips, conjunctiva of eyes. -No confusion, disorientation, difficulty with cognition. -Arterial oxygen concentration or hemoglobin Oxygen saturation within normal limits.

Documentation • Date and time oxygen started. • Method of delivery.

• Oxygen concentration and flow rate. • Patient observation. • Add oro-nasal care to the nursing care plan.