Hyperbaric Oxygen, Nitric Oxide, Heliox 2017-2019 Seminar PDF

HYPERBARIC OXYGEN, NITRIC OXIDE AND HELIOX GHAT Module 2 Objectives Describe the mechanism of action of HBO Understand the indications and contraindications of HBO Describe the hazards of HBO Describe the mechanism of action of Nitric Oxide Describe the indications/contraindic...

HYPERBARIC OXYGEN, NITRIC OXIDE AND HELIOX GHAT Module 2 Objectives Describe the mechanism of action of HBO Understand the indications and contraindications of HBO Describe the hazards of HBO Describe the mechanism of action of Nitric Oxide Describe the indications/contraindications of Nitric oxide Describe the clinical indications for heliox Describe the clinical application of heliox Hyperbaric Oxygen Therapy Hyperbaric oxygen therapy (HBO2) is inhalation of oxygen at pressure greater than atmospheric pressure at sea level. (The therapeutic use of O2 at pressures greater than 1 atm) HBO2 multiple medical applications Henshaw built the first type in London (1662) First chamber built in USA in 1861 in Rochester, Currently available at more than 500 medical centers in the USA Undersea and Hyperbaric Medical Society (UHMS) in USA Blood Oxygen Content The majority of oxygen is transported by the arterial blood from the lungs to the tissues in chemical combination with hemoglobin (Hb). Effectiveness of blood oxygen transport is dependent on: – Partial pressure of oxygen in the arterial blood (PaO2) – Hemoglobin level – Percent saturation of the hemoglobin with oxygen Hyperbaric Oxygen Therapy Physiologic effects – Bubble reduction (Boyle’s law) – Hyperoxygenation of blood and tissue (Henry’s law) – Vasoconstriction – Enhanced host immune function – Neovascularization Copyright © 2017 Elsevier Inc. All Rights Reserved. 5 Principle of Operation :HBO2 Depends on several physical principles of gases and gas laws (e.g., Boyle’s, Henry’s, Dalton’s, Fick’s, and Amonton’s laws) Increasing atmospheric pressure 2−3 folds increases O2 dissolved in plasma by 3−5 times Further increase in FiO2 to 100%, increases O2 dissolved in plasma by 17−20 times Gas Laws Boyle’s Law: – at constant temperature – Increasing pressure will lead to reduction of gas bubbles in air embolism – During decompression of pressure, trapped gas in body cavity can expand and cause barotraumas Henry’s Law: – Mass of a gas = pressure × solubility – Explains the benefit of hyperbaric oxygen therapy in increasing the tissue oxygen tension (Hyperoxia). Increases the amount of O2 dissolved in plasma. (0.3 ml/dl RA at sea level to nearly7 ml/dl RA at 3 ATA) Gas Laws (cont.) Dalton’s Law: – Pressure of a gas = pressure of mixture × fraction of the gas in the mixture PO2 PO2 (mmHg) PO2 (mmHg) (mmHg) (1 ATA, (3 ATA, (1 ATA, RA) 100%) 100%) Inspired 160 760 2,280 Gas Alveolar 100 660 2,150 Gas Arterial 95 600 2,000 Blood Body 40 100 400 Tissues Gas Laws (cont.) Fick’s Law of Diffusion: R: rate of diffusion D: diffusion coefficient A: surface area of membrane P : partial pressure difference across membrane d: distance across the membrane Explains the increased O2 diffusion to tissues during hyperbaric O2 therapy by increasing the partial pressure difference across the membrane Application of Hyperbaric O2 Indications Gas embolism: (Air or other gas ) – Iatrogenic causes: surgical procedures, lung biopsy, central line placement – Treatment reduces the volume of gas bubble – Current recommendations: 2.8 ATA for 2−4 hours – Repeat treatment until no further improvement is seen Indications (cont.) Carbon monoxide (CO) poisoning: – HBO2 accelerates the rate of CO dissociation from Hgb – HBO2 decreases the COHgb half-life from 5.5 hrs on room air to 23 min breathing 100% at 3 ATA – Current recommendations: 2.5−3 ATA for 90−120 minutes – Repeat treatment for residual neurologic symptoms Indications (cont.) Clostridial myositis and myonecrosis (gas gangrene): – HBO2 should be started early – HBO2 improves tissue oxygenation, decreases production of toxins, and augments antibiotic activity – Current recommendations: 3 ATA for three 90-minute sessions on day 1 followed by twice-daily sessions for the next 2−5 days or until clinical improvement is seen Indications (cont.) Crush injuries, compartment syndrome, and acute traumatic ischemia: – HBO2 should be started early (within 4−6 hrs) – HBO2 improves tissue oxygenation, edema reduction, angiogenesis, and tissue protection from reperfusion injury – Current recommendations: 2−2.5 ATA for 90−120 minutes – Sessions three times daily for first 2 days then twice daily for the next 2 days, and then daily for the following 2 Indications (cont.) Decompression sickness (DCS): – HBO2 should be started within 6 hours – HBO2 reduces the gas bubble size, reverses the tissue ischemia, and reduces cerebral edema – Current recommendations: 2.8 ATA for 2−4 hours; can be repeated up to 10 times if symptoms persist Indications : wound healing Necrotizing fasciitis (NF): – HBO2 improves tissue oxygenation, decreases production of toxins, and augments antibiotic activity Problem wounds (chronic non-healing wounds): – HBO2 induces fibroblast proliferation and collagen synthesis, stimulates growth factors, and direct and indirect antimicrobial activity Contraindications Absolute contraindications: – Untreated pneumothorax – Concurrent treatment with bleomycin, cisplatin, doxorubicin, disulfiram Relative contraindications: – Pulmonary lesions – Obstructive lung disease – Seizure disorder – Acute viral illness – Reconstructive ear surgery – Optic neuritis – Congestive heart failure – Acidosis – Certain medications: narcotics, insulin, steroids, nicotine, nitroprusside, hydrocarbon-based ointment, or gels Complications Oxygen and CNS toxicity: – 100% O2 for short duration (90−120 minutes) under hyperbaric conditions at 2−3 ATA, not highly associated with pulmonary oxygen toxicity – Central and peripheral nervous system toxicity: Incidence of tonic-clonic seizures is estimated at 0.3% at 2.4 ATA and 2.5% at 3 ATA Risk factors: exertion, fever, hypoglycemia, hypercapnea, brain trauma, some medications Oxygen-induced seizures are self limiting and resolve quickly after discontinuing oxygen with no neurologic sequelae Complications (cont.) Claustrophobia: – Some patients may experience anxiety especially in small monoplace chambers Barotrauma: – In the middle ear, sinuses, or pulmonary system – Middle ear trauma (2%) resolves spontaneously – Pulmonary barotrauma in the form of pneumothorax needs immediate treatment Ophthalmologic: – Progressive myopia in patients undergoing more than 20 sessions – Temporary and resolves within 6 weeks after discontinuing treatment Hyperbaric Oxygen Therapy: Methods of Administration A multiplace chamber is a large tank capable of holding a dozen or more people – Have air locks that allow entry and exit without altering the pressure. – Generally filled with air – If indicated, only the patient breathes supplemental O2 (through a mask or another device). Monoplace chamber can hold only one patient Copyright © 2017 Elsevier Inc. All Rights Reserved. 20 HBO Chambers Copyright © 2017 Elsevier Inc. All Rights Reserved. 21 Figure 03.F15B: Monoplace chamber. Photos courtesy of Reimers Systems, Inc.  Figure 03.F12: Communication within monoplace chambers. © Chris Hondros, Getty Images News/Thinkstock Figure 03.F18: Diagram of a multiplace chamber showing the entry compartment and the treatment chamber. Courtesy of Reimers Systems, Inc. Figure 03.F16: Multiplace chamber showing an assistant with a patient and monitoring personnel. Courtesy of Reimers Systems, Inc. Figure 03.F19: Patient inside a multiplace chamber getting the hyperbaric oxygen through a hood. Courtesy of U.S. Air Force Photo/Ken Wright. Figure 03.F23: Mobile multiplace chamber in a trailer. Courtesy of Reimers Systems, Inc. Hazards Monitoring ECG, EEG, hemodynamics (invasive and noninvasive) Oxygenation: TcPO2 and pulse oximetry (special care with ABGs) Ventilation: End-tidal CO2, TcPCO2 Monitors are usually located outside chamber Mechanically ventilated patients: – Not all ventilators are approved for use in hyperbaric chambers – Manual ventilation might be an option; however, manual resuscitators should be equipped with a device that ensures the O2-enriched exhalation gas is vented out of the chamber – ET tube cuff should be deflated and filled with distilled water or air-filled cuff should be automatically controlled Nitric Oxide – When inhaled, it is a selective pulmonary vasodilator – Improves blood flow to lung – Reduces shunting – Improves oxygenation – Decreases pulmonary vascular resistance – Approved by FDA for persistent pulmonary hypertension of the newborn – When delivered along with O2, may form small amounts of nitrogen dioxide (toxic gas) Copyright © 2017 Elsevier Inc. All Rights Reserved. 30 Nitric Oxide Therapy (Cont.) Potential uses for inhaled nitric oxide – ARDS – Persistent pulmonary hypertension of the newborn – Primary pulmonary hypertension – Pulmonary hypertension after cardiac surgery – Cardiac transplantation – Acute pulmonary embolism – COPD – Congenital diaphragmatic hernia – Sickle cell disease – Testing pulmonary vascular responsiveness Copyright © 2017 Elsevier Inc. All Rights Reserved. 31 Nitric Oxide (cont.) In the US, only commercially available delivery systems are the INOmax and INOvent systems by Ikaria These can be used with or without mechanical ventilation Nitric oxide gas cylinders of 800 parts per million (ppm) During MV, NO is introduced in the inspiratory limb of the ventilator circuit NO flow is controlled to achieve the desired therapeutic NO doses (generally 5−20 ppm) Downstream monitoring of NO and NO2 is essential Nitric Oxide Therapy (Cont.) Adverse effects associated with nitric oxide therapy – Poor or paradoxical response – Methemoglobinemia – Increased left ventricular filling pressure – Complications of certain cardiac anomalies (coarctation of the aorta) – Rebound hypoxemia, pulmonary hypertension Copyright © 2017 Elsevier Inc. All Rights Reserved. 33 Nitric Oxide Therapy (Cont.) Expensive !! Alternatives: – Inhaled pulmonary vasodilators – Pill forms- Systemic effects : not specific to pulmonary system Copyright © 2017 Elsevier Inc. All Rights Reserved. 34 Helium-Oxygen Therapy Value of helium as therapeutic gas is based solely on its low density Can decrease work of breathing for patients with airways obstruction Guidelines for use: – Helium must always be mixed with O2 – Heliox can be prepared at bedside or used from premixed cylinders – In general, heliox should be delivered to patients via tight- fitting nonrebreathing mask with high flow Copyright © 2017 Elsevier Inc. All Rights Reserved. 35 Heliox Mixture of helium and oxygen (80/20; 70/30) Decreases the effective flow resistance in patients with upper airway obstruction It decreases turbulence around an airway obstruction Delivered with a non-rebreathing oxygen mask Heliox (cont.) Actual flow of heliox is either 1.8 (80:20) or 1.6(70:30) times the flow indicated on an oxygen-calibrated flowmeter Should not be delivered with ventilators not designed to deliver heliox Can be used to nebulize and deliver bronchodilators May improve aerosol delivery to pediatrics through a high-flow nasal cannula Helium-Oxygen Therapy (Cont.) Troubleshooting and hazards – Reduces effectiveness of coughing – Badly distorts patient’s voice – Hypoxemia can be problem Copyright © 2017 Elsevier Inc. All Rights Reserved. 39 Heliox as a driving gas for Medication nebulizers In one study, the deposition pattern of aerosol particles in the therapeutic range of 3.6 m was studied among asthmatic subjects breathing either air/oxygen or heliox mixtures. The relationship between the inspiratory flow pattern (how fast the patient inhaled) and the mixture of heliox was compared to air gas mixtures. The deposition of aerosols was increased by 63% at 0.5 L/s, and 83% at 1.2 L/s inspiratory flow with heliox mixtures, over aerosols inhaled in air using the same inspiratory maneuvers. This means that the patient that can inhale deeply at a moderate inspiratory rate improves the amount of medication that they can get into their lungs. This effect is increased in patients with acute asthma vs. normal patients without airway obstruction. In another study, the effect of heliox on nebulizer function was studied. The basic conclusion was that when heliox (80% He + 20%O2) was used to power or drive the nebulizer (as the primary gas), medication delivery was adversely affected. This makes perfect sense because of its lightweight density characteristics, which would mean that the gas driving force (flow) would need to be increased in order to produce the same geometric aerosol plume as a heavier primary driving gas.