OXYGEN THERAPY.pptx

Oxygen therapy and oxygen delivery devices in ICU

1. METHODS OF OXYGEN THERAPY IN ICU Dr. Kanika Chaudhary

2. OVERVIEW History Oxygen content and oxygen delivery Indications of oxygen therapy Oxygen delivery systems ECMO Oxygen toxicity

3. HISTORY Joseph Priestley described oxygen as a constituent of atmosphere. Lavoisier demonstrated that oxygen is absorbed by the lungs, metabolized in the body and then eliminated as co2 and H2o. J.S.Haldane – Father of modern oxygen therapy.

4. OXYGEN CONTENT & OXYGEN DELIVERY Tissue hypoxia exists when delivery of O2 is inadequate to meet the metabolic demands of the tissues. Arterial oxygen content (Cao2) depends on the arterial partial pressure of O2 (PaO2), the hemoglobin concentration of arterial blood ( Hb ), and the saturation of hemoglobin with O2 (Sao2). Cao2 = Sao2 x Hb x 1.34 + Pao2 x 0.0031 1.34 : O2 carrying capacity oh hemoglobin 0.0031 : solubility co-efficient of oxygen in plasma Normal Cao2 is approximately 20ml/dl for an adult with Hb of 15g/dl

5. O2 delivery (DO2) is calculated by multiplying cardiac output (liters per minute) by the arterial O2 content DO2 = Cao2 x CO x 10 DO2 for a 70-kg, healthy patient, it is approximately 1000 mL/min OXYGEN CONTENT & OXYGEN DELIVERY

6. Decrement of any of the determinants of DO2 like anemia, low cardiac output, hypoxemia, or abnormal hemoglobin affinity (e.g., carbon monoxide toxicity) HYPOXIA Inspiration of enriched concentrations of O2 Increase the PaO2, the percentage of saturation of hemoglobin and the O2 content AUGMENT DO2

7. Hypoxemia is defined as a deficiency of O2 tension in the arterial blood i.e PaO2 value less than 80 mm Hg

8. Consequences of untreated hypoxemia Tachycardia Acidosis Increased myocardial O2 demand Increased minute volume and work of breathing By treating hypoxemia , supplemental O2 restores homeostasis and decreases the stress response and its resultant cardiopulmonary sequelae

9. Documented hypoxemia as evidenced by PaO 2 < 60 mmHg or SaO 2 < 90% on room air Acute care situations in which hypoxemia is suspected Severe trauma Acute myocardial infarction Short term therapy (Post anaesthesia recovery) O 2 Therapy : Indications ( AARC CLINICAL PRACTICE GUIDELINES 2012

10. CLASSIFICATION OF OXYGEN DELIVERY DEVICES PERFORMANCES (Based on predictability and consistency of Fi O 2 provided) Fixed Variable DESIGNS Low- flow system Reservoir systems High flow system Enclosures

11. Oxygen delivery systems Normobaric Hyperbaric Low dependency Medium dependency High dependency Variable performance Fixed performance

12. I - BASED ON PERFORMANCE In a non –intubated patient breathing in an “open” system the ability of the oxygen delivery device to meet the patient’s inspiratory flow will determine the amount of room air that will be entrained. The FiO 2 delivered from the oxygen source will be diluted by the entrained room air. Therefore, the oxygen delivery systems are categorized as either variable performance ( no control on FiO 2 ) or fixed performance ( controlled FiO 2 ) systems

13. The variable performance systems are ‘ patient-dependent ’ because the FiO 2 that the patient receives will change with changes in the respiratory parameters. For example, nasal catheters, nasal cannulae and masks with or without a rebreathing bag.   The fixed performance systems are usually considered as ‘ patient-independent ’ because regardless of changes in respiratory parameters, the patient will receive a constant, predetermined inspired oxygen concentration (FiO 2 ). For example, Ventimask . I - BASED ON PERFORMANCE

14. II - BASED ON DESIGN Low-flow systems deliver oxygen at flows that are insufficient to meet the patient’s inspiratory flow rate leading to air entrainment. As a result of this, FiO 2 may be low or high, depending on the specific device and the patient’s inspiratory flow rate and minute ventilation (variable performance). Low flow systems do not mean low FiO2 values and they produce FiO2 values between 21-80%.

15. Variation of FiO2 in low flow

16. Low dependency Low flow systems High flow systems Nasal c a n nula Simp l e mask R e s e r v o i r mask Partial r e b r e a ther Non r e b r e a ther V e n turi mask HFNC Blen d e r s

17. Nasal Cannula / Prongs A plastic disposable device consisting of two tips or prongs 1 cm long, connected to oxygen tubing Inserted into the vestibule of the nose; nasopharynx serves as the reservoir FiO 2 – 24-44% Flow – 0.25 - 8L/min (adult) < 2 L/min(child) Humidifier is needed when the input flow exceeds 4 L/min

18. MERITS Easy to fix Not much interference with further airway care Low cost Compliant DEMERITS Can get dislodged High flow uncomfortable Nasal trauma Mucosal irritation, epistaxis, headache if oxygen is not humidified when >4lt/min is used FiO2 can be inaccurate and inconsistent Nasal Cannula / Prongs

19. Estimation of FiO 2 provided by nasal cannula O 2 Flow rate (L/min) FiO 2 1 0.24 2 0.28 3 0.32 4 0.36 5 0.40 6 0.44

20. NASAL CATHETER A soft plastic tube with several small holes at the tip. Available from 8-14 FG size. It is inserted along the floor of either nasal passage till the tip is just above and behind the uvula. Once in position it is taped to bridge of nose. It is blindly inserted to a depth equal to the distance from nose to tragus. Oropharynx acts as the anatomic reservoir. Should be replaced every 8 hrs. Avoided in patients with maxillofacial trauma, basal skull #, nasal obstruction and coagulation abnormalities

21. TRANSTRACHEAL CATHETER A thin polytetrafluoroethylene (Teflon) catheter Inserted surgically with a guidewire between 2 nd and 3 rd tracheal rings FiO2 – 22 – 35% Flow – 0.25 - 4L/min Because the catheter resides directly in trachea, O2 builds up both there and in upper airway during expiration, increases anatomical reservoir and increases Fio2 at any flow

22. TRANSTRACHEAL CATHETER Lower O 2 use and cost Eliminates nasal and skin irritation Better compliance Increased exercise tolerance Increased mobility High cost Surgical complications Infection Mucus plugging MERITS DEMERITS

23. Simple face mask / Hudsons Mask / Mary Catterall Mask Open ports for exhaled gas. Air is entrained through ports if O 2 flow does not meet peak inspiratory flow. Because air dilution easily occurs during inspiration through its ports and around its body, it provides a variable fiO2 Gas flow>8 doesn ’ t significantly increase fio2 as the o2 reservoir is filled

24. Reservoir - 100-250 ml (adult) ; 70-100ml (pediatric) Low flow, Variable performance device FiO 2 varies with O 2 input flow mask volume Fitting of the mask patient ’ s breathing pattern FiO 2 : 40 – 60% Input flow range is 5-8 L/min Minimum flow – 5L/min to prevent CO 2 rebreathing Simple face mask / Hudsons Mask / Mary Catterall Mask

25. MERITS Moderate but variable FiO2. Good for patients with blocked nasal passages and mouth breathers Easy to apply DEMERITS Uncomfortable Interfere with further airway care Proper fitting is required Risk of aspiration in unconscious patient Rebreathing (if input flow is less than 5 L/min) O 2 Flowrate (L/min) Fi O 2 5-6 0.4 6-7 0.5 7-8 0.6 Simple face mask / Hudsons Mask / Mary Catterall Mask

26. RESERVOIR MASKS Have a 600 ml-1litre reservoir bag attached to o2 inlet. Because bag increases the reservoir volume, they provide higher fio2. they are low flow, variable performance devices. Partial rebreathing mask Nonrebreathing mask

27. PARTIAL REBREATHING MASK No valves Mechanics – Exp: first 1/3 of exhaled gas (anatomic dead space) enters the bag and last 2/3 of exhalation escapes out through ports Insp: the first 1/3 exhaled gas and O2 are inhaled FiO2 - 60-80% FGF 6-10L/min The bag should remain inflated to ensure the highest FiO2 and to prevent CO2 rebreathing If the total ventilatory demands are met without room air entrainment, it acts as fixed performance device O 2 Exhalation ports +

28. Non rebreathable mask Rebreathable mask

29. NON-REBREATHING MASK Has 3 unidirectional valves Expiratory valves prevents air entrainment Inspiratory valve prevents exhaled gas flow into reservoir bag FiO 2 - 0.80 – 0.90 FGF – 10 – 15L/min To deliver ~100% O 2 , bag should remain inflated Factors affecting FiO 2 air leakage and patient’ s breathing pattern One-way valves O 2 Reservoir

30. RESERVOIR MASKS MERITS Variable FiO2 depending on mask fit Not well tolerated by claustrophobic patients Interfere with feeding Children are not compliant Entrainment ports may get blocked and alter performance Aspiration of vomitus in patients with blunted airway reflexes Fast and easy to set up Compliant DEMERITS

31. RESERVOIR SYSTEMS Reservoir system stores a reserve volume of O 2 between patient breaths , that equals or exceeds the patient ’ s tidal volume Patient draws oxygen from this reserve whenever inspiratory flow exceeds O 2 flow, Thus , room air entrainment is reduced. Variable performance device. Delivers moderate - high FiO 2 . Reservoir may include the anatomic reservoir, mask and reservoir bag.

32. HIGH FLOW SYSTEMS

33. Air entrainment devices Based on Bernoulli principle – A rapid velocity of gas exiting from a restricted orifice will create subatmospheric lateral pressures , resulting in atmospheric air being entrained into the mainstream.

34. Mechanism of Air entrainment devices When a pressurized oxygen is forced through a constricted orifice the increased gas velocity distal to the orifice creates a shearing effect that causes room air to be entrained through the entrainment ports at a specific ratio so that variation in orifice or entrainment port will change fio2. oxygen room air exhaled gas

35. Jet-mixing Venturi Mask/ Air Entrainment Mask (AEM)

36. Characteristics of Air entrainment devices Amount of air entrained varies directly with size of the port and the velocity of O2 at jet They dilute O 2 source with air - FiO 2 < 100% The more air they entrain, the higher is the total output flow but the lower is the delivered FiO 2

37. DEVICE FLOW RATE The air:O 2 ratio for an air entrainment mask at FIO 2 40%? Air:oxygen= 100-FiO 2 = 100-40 = 60 = 3.2 FiO 2 -21 40-21 19 Ratio for 40% is (3.2 : 1) If the O 2 Flow meter is set at 10 L/min Then the entrained air will be 10x3.2 = 32 L/min Total flow = (air + O 2 ) = (10 + 32) = 42 L/min

38. Venturi / Venti / HAFOE (high airflow with oxygen enrichment) Mask FiO 2 regulated by size of jet orifice and air entrainment port FiO2 – Low to moderate (0.24 – 0.60) HIGH FLOW FIXED PERFORMANCE DEVICE

39. These masks are colour coded and labeled with the FiO2 that will be delivered and the O2 flow required to achieve this . A known FiO2 can also be delivered to spontaneously breathing patients on endotracheal tube by attaching the Venturi device to the T-piece. Venturi masks are often useful when treating patients with COPD who may develop worsening respiratory distress and dead space ventilation by supplemental increases in O2 fraction. Venturi / Venti / HAFOE (high airflow with oxygen enrichment) Mask

40. 35 - 60% 24 - 31%

41. Adjustable venturi valve

42. Approximate air entrainment ratio, O 2 flow rates and colour coding related to FiO2 of venturi devices FiO 2 Colour Flow rate (l/min) Air:oxygen entrainment Total gas Flow (l/min) 0.24 Blue 2 25:1 52 0.28 White 4 10:1 44 0.31 Orange 6 8:1 54 0.35 Yellow 8 5:1 48 0.40 Red 10 3:1 40 0.60 Green 15 1:1 30

43. Caution Obstructions distal to the jet orifice or occlusion of the exhalation ports can produce back pressure and an effect referred to as Venturi stall . When this occurs, room air entrainment is compromised, causing a decreased total gas flow and an increased FIO2. Aerosol devices should not be used with these devices. Water droplets can occlude the O2 injector. If humidity is needed, a vapor humidity adapter collar should be used.

44. HIGH FLOW NASAL CANNULA Delivers heated and humidified oxygen via special devices . The apparatus comprises an air/oxygen blender, an active heated humidifier, a single heated circuit, and a nasal cannula. At the air/oxygen blender, the inspiratory fraction of oxygen (FIO2) is set from 0.21 to 1.0 in a flow of up to 60 L/min. The gas is heated and humidified with the active humidifier and delivered through the heated circuit.

45. HIGH FLOW NASAL CANNULA

46. High flow of adequately heated and humidified gas is considered to have a number of physiological effects. 1. High flow washes out carbon dioxide in anatomical dead space. 2. Although delivered through an open system, high flow overcomes resistance against expiratory flow and creates positive nasopharyngeal pressure. 3. The difference between the inspiratory flow of patients and delivered flow is small and FIO2 remains relatively constant. 4. Because gas is generally warmed to 37°C and completely humidified, mucociliary functions HIGH FLOW NASAL CANNULA

47. HIGH FLOW NASAL CANNULA

48. BLENDING SYSTEMS When high O 2 conc / flow is required Inlet – seperate pressurized air, O 2 source Gases are mixed inside either manually or with blender Output – mixture of air and O 2 with precise FiO 2 and flow Ideal for spontaneously breathing patients requiring high FiO 2

49. O 2 blending device

50. Blending systems FiO 2 – 24 – 100% Provide flow > 60L/min Allows precise control over both FiO 2 and total flow output - True fixed performance devices

51. ENCLOSURES

52. OXYGEN HOOD An oxygen hood covers only the head of the infant O2 is delivered to hood through either a heated entrainment nebulizer or a blending system Fixed performance device Fio2 – 21-100% Minimum Flow > 7L/min to prevent CO2 accumulation Easy access to chest, abdomen and extremities

53. OXYGEN TENT Consists of a canopy placed over the head and shoulders or over the entire body of a patient  FiO 2 – 50-70% @12-15L/minO 2 Variable performance device Temperature is regulated by flowing oxygen and air over ice chunks to prevent accumulation of heat of the exothermic reactions Disadvantage Expensive Cumbersome Difficult to clean Constant leakage Limits access to the baby

54. INCUBATOR Incubators are polymethyl methacrylate enclosures that provides temperature-controlled environment with supplemental humidified O2 FiO2 – 40-50% @ flow of 8-15 L/min Variable performance device

55. Long term O 2 delivery systems Gas supplies Oxygen concentrators Compressed gas Liquid oxygen Delivery devices for LTOT include most of the low flow devices Designed to “conserve” home oxygen by improving efficiency of oxygen delivery

56. LTOT delivery devices: Nasal cannulae Reservoir nasal cannulae Electronic conserving devices pulse devices (fixed volume/breath) demand devices (variable volume – length ) Transtracheal catheters Long term O 2 delivery systems

57. Noninvasive positive pressure ventilation Refers to mechanical ventilation delivered to a patient without placement of endotracheal or tracheostomy tube. Indications -reduction of respiratory workload in obesity. -acute respiratory failure -acute hypercapnic excerbation of copd Contraindication -apnea -unable to handle secretions -facial trauma -claustrophobia

58. Delivered by using CPAP OR BIPAP NPPV interfaces include nasal mask,oronasal mask,nasal pillows and full-face mask. CONTINUOUS POSITIVE AIRWAY PRESSURE It increases FRC and improves oxygenation but gives no ventilatory assistance Most common use is in the treatment of chronic obstructive sleep apnea at home. Noninvasive positive pressure ventilation

59. II. BILEVEL POSITIVE AIRWAY PRESSURE It has an inspiratory positive airway pressure (IPAP) setting that provides mechanical breaths and an expiratory positive airway pressure (EPAP) level that functions as positive end expiratory pressure(PEEP) Two major indications are acute respiratory failure and acute hypercapnic excerbations of copd . Noninvasive positive pressure ventilation

60. EXTRA CORPOREAL MEMBRANE OXYGENATION ECMO consists of a specific heart lung machine to provide gas exchange for prolonged support of patients with severe but potentially reversible respiratory or cardiac failure or both. The main purpose of ECMO is to provoide adequate oxygen delivery and CO 2 clearance in proper proportion to systemic needs. The overall goal of cardiorespiratory care is to keep DO 2 at least twice oxygen consumption. When medical treatment is unable to maintain this equilibrium and/or the risk of ongoing ventilator or vasopressor induced iatrogenic injury arises, then ECMO may be indicated to provide life support, allowing time for diagnosis and treatment until cardiorespiratory system is restored.

61. TYPES OF ECMO In general, when only respiratory assistance is required, veno venous ECMO is advisable. If cardiocirculatory support is necessary, then veno arterial ECMO is needed. In the venoarterial route ,blood goes from the right atrium (via the internal jugular vein ) to the aortic arch (via the right common carotid artery).This route oxygenates the blood and supports the patient’s cardiac function. In the venovenous route ,blood goes from the right atrium(via the right internal jugular vein) and returns to the right atrium(via the femoral vein).This route oxygenates the blood only and does not support the patient’s cardiac function.

62. COMPLICATIONS PHYSIOLOGIC Bleeding secondary to the high level of heparin required for anticoagulation. Intracranial haemorrhage Seizures Infection Haemotologic complications anaemia,leucopenia,thrombocytopenia –caused by the consumption of blood components by the membrane oxygenator. MECHANICAL Failure of the pump,rupture of the tubing,failure of the membrane and difficulties with the cannulas.

63. Complications of oxygen therapy Progressive hypercapnia commonly seen in patients with copd Circulatory depression- rare complication Drying and crusting of secretions Fire - oxygen support combustion O2 tents and pressure chambers are most hazardous forms of O2 therapy

64. Oxygen toxicity Pulmonary toxicity (Lorrain Smith effect) -most common manifestation of oxygen overdosage seen in clinical practice Retrolental fibroplasia in neonates Hypoventilation – seen in patients with chronic hypoxaemia and hypercarbia Central nervous system toxicity (Paul Bert effect)

65. Pulmonary toxicity First described by a pathologist Lorrain Smith in 1899. It appears when O2 is administered at a pressure varying from 0.7 to 3 ATA. MECHANISM Absorption collapse – simple atelectasis resulting from blockage of small airways with resultant absorption of gases trapped peripheral to the obstruction.

66. PATHOLOGICAL FINDINGS Exudative phase - interstitial oedema -destruction of type I pneumocytes II. Proliferative phase -proliferation of type II pneumocytes -thickening of alveolar wall thereby decreasing alveolar space Earliest sign is substernal distress ,cough Decrease in vital capacity is the most sensitive indicator.As toxicity progresses MV, respiratory rate,compliance of lung will deviate from normal Pulmonary toxicity

67. CNS TOXICITY(PAUL BERT EFFECT) First described by Paul Bert in 1878 Exposure to oxygen at pressures in excess of 3 ATA(2280 mm hg ,304 kpa ) Treatment Immediate withdrawal of high pressure of oxygen and the patient allowed to breath room air RETROLENTAL FIBROPLASIA/RETINOPATHY OF PREMATURITY Result of o2 induced retinal vasoconstriction Occurs in premature neonates

68. Prevention of oxygen toxicity Use of lowest possible oxygen concentration for shortest period of time Early use of PEEP to decrease large shunt fraction Toxic effect can be inhibited by SH Compounds – glutathione, cysteine Antioxidants – vitamin E and C

69. SELECTION OF DEVICE 3 P’s Purpose Patient Performance - Goal is to match the performance characteristics of the equipment to both the objectives of therapy ( purpose ) and the patient ’s special needs

70. Purpose – improve arterial hypoxemia Patient factors in selection - Severity and cause of hypoxemia Patient age group (infant, child, adult) Degree of consciousness and alertness Presence or absence of tracheal airway Stability of minute ventilation Mouth breathing vs. nose breathing patient

71. SCENARIO 1 Critically ill adult patient with moderate to severe hypoxemia Goal – PaO 2 > 60 mm Hg / SpO 2 > 90 % Reservoir / high flow system (>60% FiO 2 )

72. SCENARIO 2 Critically ill adult patient with mild to moderate hypoxemia Immediate post op phase, recovering from MI Stability of FiO 2 is not critical System with low to moderate FiO 2 Nasal cannula / simple mask

73. SCENARIO 3 Adult patient with COPD with acute-on- chronic hypoxemia Goal – adequate arterial oxygenation without depressing ventilation Adequate-(SpO 2 of 85%-92%)(PaO 2 50-70mm Hg) venturi mask ( 0.24- 0.28 ) or low flow nasal cannula

74. REFERENCES Benumof’s airway management 2 nd edition A practice of anesthesia, 5 th edition,Wylie and Churchill Davidson. Ward’s textbook of anaesthetic equipment 6 th Edn Miller’ s anesthesia 6 th edition Clinical application of mechanical ventilation 4 th edition David w.chang Nishimura Journal of Intensive Care (2015) 3:15 DOI 10.1186/s40560-015-0084-5 High-flow nasal oxygen therapy  N Ashraf- Kashani , BSc FRCA,  R Kumar, MD FRCA DICM EDIC FFICM BJA Education , Volume 17, Issue 2, February 2017