Oxygen therapy- Rationale & Prescription By Subin Solomen MPT-CRD(Manipal) Professor EMS Memorial Co-operative Hospital & Research Centre Kerala Experience : 10 years, Publications: 17, Book Vascular rehabilitation under jaypee publishers :

Definition Increasing the concentration of oxygen in the inspired air to correct or prevent hypoxemia is oxygen therapy O2 administration aims at increasing PAO2 and there by increasing PaO2 and SPO2 of arterial blood Supplemental O2 delivery of oxygen more than 21% 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Rationale To treat or prevent hypoxemia There by preventing tissue hypoxia which may result in tissue injury and even cell death At the tissue level, mitochondrial activity requires oxygen for aerobic ATP synthesis for cellular activity In case of CO poisoning and cluster head ache In this case affinity of Hb to CO can be reduced The Half life of CoHb reduced from 4 hours to 40 minutes To resolve pneumothorax who do not require a drainage 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Indications Treatment of documented hypoxemia Adults, children, infants > 28 days,PaO2 < 60mm,SaO2 < 90% Neonates – PaO2 < 50mm hg, SaO2 < 88% Situations in which hypoxemia is suspected To decrease the work of breathing To decrease myocardial work Temporary hypoxaemia Before and after suction First time administration of bronchodilator with side effect Prior to heart surgery During exercise Patients with decreased oxygen carrying capacity Anaemia , sickle cell disease. 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Assessment of need Use of lab measures to document hypoxemia – Hb, PaO2, SPO2 Based on clinical problems CO poisoning, Cyanide poisoning, Shock, Trauma, Acute MI Clinical manifestations Respiratory- Tachypnea, Dyspnea, Cyanosis Cardio-Vascular - Tachycardia, Mild hypertension Neurological - Restlessness, Disorientation Skin – cool, clammy 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Oxygen delivery systems Low flow systems – variable performance Reservoir systems High flow systems – fixed performance Enclosures – Tent , Hood, Head Box 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Low flow systems Provides a portion of inspired gas Does not meet patients total ventilation Reservoir will be nasopharynx or oropharynyx Less than 8l/m Nasal cannula Nasal catheter Trans tracheal catheter 25/2/2016 Subin Solomen MPT(Manipal)- CRD

1. Nasal cannula Max Flow rate 6 L/m Prongs Max Flow rate 6 L/m Prong are inserted directly to nose FIO2 from.24 to .44 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Nasal Cannula Advantages Disadvantages Patient can eat and drink Well tolerated Low cost Disposable Easy to apply Unstable Easily dislodged Pressure sore around ear and nose May dry and irritate nasal mucosa Deviated septum may block flow Best use : Stable patient needing low FiO2, Home care patient requiring long term oxygen therapy 25/2/2016 Subin Solomen MPT(Manipal)- CRD

2. Nasal catheter Soft plastic tube with several holes at tip Inserted until the tip reaches the oropharynx Flow 6t08 l/m Best use : Procedures when cannula difficult to use in case of bronchoscopy 25/2/2016 Subin Solomen MPT(Manipal)- CRD

3. Trans tracheal catheter Directly to trachea 2nd or 3rd rings Flow 4 l/m Best use : Ambulatory patients who need increased mobility or do not accept nasal oxygen 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Reservoir systems – A) Cannula Reservoir cannula store O2 between breaths Types 1. Nasal reservoir 2. Pendent reservoir 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Reservoir System- B) Mask Simple mask Partial rebreathing mask Non rebreathing mask 25/2/2016 Subin Solomen MPT(Manipal)- CRD

1. Simple mask Cover both nose and mouth This increases the size of reservoir So higher FIO2 can be delivered Flow 5-12l/m Entrainment of room air & release of exhaled gases Vent Holes 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Simple Mask Disadvantages Advantages Patient may need to remove the mask for speaking, expectoration of secretions Difficulty in placing when Ryles tube in place Drying or irritation of eyes Uncomfortable with facial trauma Block vomitus in unconscious patients Light weight Inexpensive Easy to apply Disposable Can use with humidifier Delivery of FIO2 up to 0.60 Best use : Emergency patients requiring short term oxygen therapy with moderate fiO2 25/2/2016 Subin Solomen MPT(Manipal)- CRD

2. Partial rebreathing mask Reservoir bag No valves First one third expired gas enters reservoir bag This is form anatomic reservoir so it is high in oxygen and contains little CO2 Flow 6-10 l/m FIO2 from .60 to .80 Mask + Oxygen reservoir bag 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Partial Rebreathing Mask Advantages Disadvantages Higher delivery of FIO2 >0.60 Exhaled oxygen from the anatomic dead space is conserved Insufficient flow rate may lead to rebreathing of CO2 leads to suffocation hazard Limited access to mouth for eating, drinking, expectorating Eye irritation Best use : Emergency patients with short term oxygen therapy with moderate to high fiO2 25/2/2016 Subin Solomen MPT(Manipal)- CRD

3.Non re breathing mask One way valves over side ports and above reservoir bag Limits entrainment of air Prevent entrainment of room air Prevent exhaled gas entering into bag 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Non Rebreathing Mask Advantages Disadvantages Higher delivery of FIO2 Uncomfortable Limited access to mouth for eating, drinking, expectorating Eye irritation Best use : Emergency patients with short term oxygen therapy with moderate to high fiO2 25/2/2016 Subin Solomen MPT(Manipal)- CRD

High flow devices Are those in which the flow of gases is sufficient to meet all of the patients minute ventilation requirements Fixed air-oxygen entrainment ratio Venturi mask Large volume aerosol system High humidity tracheostomy mask High humidity T piece High humidity face mask High humidity face tent 25/2/2016 Subin Solomen MPT(Manipal)- CRD

High humidity face tent High humidity T piece High humidity face mask High humidity tracheostomy mask 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Venturi mask Jet nozzle and entrainment ports Delivered Fio2 dependent on the size of the nozzle, size of the entrainment ports and O2 flow Smallest jet provides highest O2 velocity , thus most air entrainment and the lowest fiO2 25/2/2016 Subin Solomen MPT(Manipal)- CRD

1) As forward velocity of gas increases Venturi mask Operates on Bernoulli principle 2) its lateral pressure decreases 1) As forward velocity of gas increases This leads to entrainment of room air 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Venturi mask Advantages Disadvantages Delivery of predictable FIO2 Useful in patients to whom delivery of excessive oxygen could depress the respiratory drive Limited access to mouth for eating, drinking, expectorating Claustrophobia Irritation to eyes Uncomfortable Noisy Best use : Unstable patients requiring precise low FiO2 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Venturi mask- port 25/2/2016 Subin Solomen MPT(Manipal)- CRD

High humidity T-piece One end Attaches to ET to TT tube Other end attaches to oxygen Third end attaches to reservoir Provide oxygen + humidification FiO2 range from 0.28 to 1.0 25/2/2016 Subin Solomen MPT(Manipal)- CRD

High Humidity T- piece Advantages Disadvantages Prevents drying of mucous Helps to thin secretions Accurate Fio2 can be delivered Tubing can become heavy with accumulated water Accidently accumulated water may drain into patients airway during position change 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Enclosures Oxygen Tent Oxygen hood 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Hazards of supplemental O2 Oxygen toxicity Oxygen induced hypoventilation Absorption atelectasis Retinopathy of prematurity Fire hazards 25/2/2016 Subin Solomen MPT(Manipal)- CRD

1. Oxygen toxicity Primarily involves lungs and CNS CNS: tremors , twitching and convulsion 100% fio2 complains chest tightness , decreased VC, Residual volume, lung compliance Results in broncho pneumonia , interstitial oedema, destruction of type I and 2 cells Due to over production of free radicals 25/2/2016 Subin Solomen MPT(Manipal)- CRD

2. Oxygen induced hypo ventilation Normally carbon dioxide (hypercapnea) is primary stimulant drive for respiration In patients with chronic hypercapnea CNS response to elevated CO2 level become blunted , then hypoxemia becomes major drive But Administration of high FiO2 blunts this drive which results in hypoventilation 25/2/2016 Subin Solomen MPT(Manipal)- CRD

3. Absorption atelectasis Due to depletion of alveolar and blood nitrogen All the alveolar oxygen is replaced to capillaries 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Absorption atelectasis Pathophysiology Normally Reduced ventilation leads to vasoconstriction to the affected segments With 100% FiO2 Vasoconstriction becomes dilated Whole nitrogen in alveoli and blood is replaced by oxygen Distal to obstruction whole air in the alveoli is absorbed to capillary Results in atelectasis 25/2/2016 Subin Solomen MPT(Manipal)- CRD

4. Retinopathy of pre maturity In neonates and infants Excessive O2 leads to retinal vasoconstriction which leads to necrosis= New vessels form and results in hemorrhage, results in scarring 25/2/2016 Subin Solomen MPT(Manipal)- CRD

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Limitations Directing oxygen into throat does not guarantee its arrival at the mitochondria Oxygen does not improve ventilation directly If hypoxemia is due to a large shunt then oxygen therapy is refractory to hypoxemia 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Oxygen Prescription Oxygen should be prescribed to achieve a target saturation of 94–98% for most acutely ill patients or 88–92% for those at risk of hypercapnic respiratory failure The target saturation should be written (or ringed) on the drug chart Oxygen should be reduced in stable patients with satisfactory oxygen saturation. Oxygen should be crossed off the drug chart once oxygen is discontinued 25/2/2016 Subin Solomen MPT(Manipal)- CRD

Summary Target the saturation range Choose the goal Short term oxygen therapy Long term oxygen therapy To choose a delivery system consider Device advantages & disadvantages FIO2 limits Appropriateness for a particular patient To call a high flow device atleast60l/min 20l/m is the upper limit for sick people 25/2/2016 Subin Solomen MPT(Manipal)- CRD