medical gas delivery
inspiratory demand
vt=vxti
What is retinopathy of prematurity and what can it cause
- Also called retrolental fibroplasias: Abnormal eye condition in some premature or low birth weight infants caused by supplemental oxygen - Excessive blood oxygen levels cause retinal vasoconstriction: causes necrosis of the blood vessels - Hemorrhage of the delicate vessels causes scarring behind the retina which can lead to retinal detachment and blindness - can affect neonates up to 1 month of age - hypercapnia, infection, anemia, hypothermia is also associated with ROP PaO2 greater than 80 with oxygen therapy in infants and neonates can cause retinopathy of prematurity
O2 induced hypoventilation
- COPD and chronic hypoxemia and hypercarbia - COPD rely on low levels of o2 to initiate breathing to much o2 will stop breathing -use venturi mask if tolerated
Indications of O2 therapy
- Documented hypoxemia: 1. PaO2 less than 60 mmHg 2. SaO2 less than 90% on room air 3. Severe trauma 4. Acute Myocardial Infarction (or suspected) 5. Short term therapy (post-anesthesia)
high flow oxygen
- Supply a given oxygen concentration at a flow equal to patients inspiratory demand - An air entrainment or lending system is used (except in case of NRB) - RULE OF THUMB: to qualify as a high flow device must provide at least 60LPM total flow
low flow oxygen
- typically provides supplemental O2 to the patients directly to the airway at a flow of 8 LPM or less - provides only part of the patient's inspired volume - low flow oxygen devices include: nasal cannula, nasal catheter, and the transtracheal catheter
Low-Flow Oxygen Delivery Systems
-Nasal cannula -Simple face mask -Partial rebreather mask -Nonrebreather mask
The objectives of Oxygen Therapy are:
1. Correct hypoxemia 2. Decrease symptoms associated with hypoxemia (WOB) 3. Decrease workload hypoxemia puts on cardiovascular system (WOH) Correcting Hypoxemia
When using Heliox, how would you calculate the actual Heliox flow from the observed O2 flow on the flowmeter (10 L/min)?
80% He / 20% O2 = Heliox factor: 1.870% He / 30% O2 = Heliox factor: 1.660% He / 40% O2 = Heliox factor: 1.4Observed flow on flow meter (10 L/min) X factor (1.8) = 18L/min of actual Heliox flow
When to add humidity to nasal cannula, what to do if humidifier pop off alarm is sounding and what is possible cause for alarm?
4lpm
Complications associated with hyperbaric O2 therapy
Barotrauma ØEar or sinus trauma ØTympanic membrane rupture ØAlveolar overdistention and pneumothorax ØGas embolism Oxygen toxicity ØCNS toxic reaction ØPulmonary toxic reaction Other ØFire ØSudden decompression ØReversible visual changes ØClaustrophobia ØDecreased cardiac output
Indications for hyperbaric o2 therapy
Acute conditions ØDecompression sickness ØAir or gas embolism ØCarbon monoxide and cyanide poisoning ØAcute traumatic ischemia (compartment syndrome, crush injury) ØAcute peripheral arterial insufficiency ØIntracranial abscesses ØCrush injuries and suturing of severed limbs ØClostridial gangrene ØNecrotizing soft tissue infection ØIschemic skin graft or flap Chronic conditions ØDiabetic wounds of the lower extremities and other nonhealing wounds ØRefractory osteomyelitis ØActinomycosis (chronic systemic abscesses) ØRadiation necrosis (HBO as an adjunct to conventional treatment)
Fio2 changes with downstream resistance for Air Entrainment nebulizer
Any increase in flow resistance downstream from (distal to) the point of air entrainment alters the performance of all air-entrainment systems ØIncreased downstream flow resistance causes back pressure ØBack pressure decreases both the volume of entrained air and the total flow output of these devices With less air entrained, the delivered O2 concentration increases ØBecause total flow output also decreases, the effect on FiO2 varies
Complications and Hazards of HBO
Barotrauma ØEar or sinus trauma ØTympanic membrane rupture ØAlveolar overdistention and pneumothorax ØGas embolism Oxygen toxicity ØCNS toxic reaction ØPulmonary toxic reaction Other ØFire ØSudden decompression ØReversible visual changes ØClaustrophobia ØDecreased cardiac output
Therapeutic use for heliox therapy
Can decrease work of breathing for patients with airways obstruction
Trouble shooting a NRB bag collapse, no collapse, slight collapse
Common problems with reservoir masks include: ØDevice displacement ØSystem leaks and obstructions ØImproper flow adjustment ØSkin irritation
What occurs to FiO2 when air entrainment ports are blocked
Delivered O2 concentration increases, but total output flow decreases
Interfaces for air entrainment nebulizers
Direct a high-pressure O2 source through a small nozzle or jet surrounded by air-entrainment ports The amount of air entrained at ports varies directly with the size of the port and the velocity of O2 at the jet FiO2 provided by air-entrainment devices depends on two key variables: ØThe air-to-O2 ratio ØThe amount of flow resistance downstream from the mixing site
Minimum LPM for simple mask and why?
Flows less than 5 LPM will allow the mask to act as deadspace and causes CO2 rebreathing
criteria for HBO in CO poisoning
History of unconsciousness Presence of neuropsychiatric abnormality Presence of cardiac instability or cardiac ischemia Carboxyhemoglobin level 25% (lower levels for children and pregnant women)
When should nonrebreathers be used
Most often used in patients who need high‐concentration oxygendelivery (10 to 15 L/min)• Should not be used in patients with apnea or poorrespiratory effort
What is the problem with input flows greater than 10 to 15 L/min in an infant Oxy-Hood?
Production of harmful noise levels
Device of choice for severe chest pain with central cyanosis
Simple Mask O2 Mask @ 8 L/min
FiO2 (fraction of inspired oxygen)
The concentration of oxygen in the air we breathe
flow output from flowmeter for heliox 80/20 and 70/30 mixtures?
The heliox factor for a 70% He/30% O2 mixture is 1.6 and the heliox factor for an 80% He/20% O2 mixture is 1.8.
how to calculate total flow
Total flow = Flowmeter setting X factor (use magic box) i.e 5 L X 11 = 55 L/ min If you are given total flow and have to calculate flowmeter setting. Find the factor then divide that into the total flow Take the factor and multiply by each answer to see which one matches the total flow
High flow oxygen delivery systems
Venturi mask Face tent Aerosol mask Tracheostomy collar T-piece
What device is the BEST for patients with COPD?
cpap
how to calculate fio2
equals liters per minute flow * 4 + 20
0.6: 1 is the Air/O2 ratio If the flowmeter is set on 15 LPM Total Flow = 1.6 X 15 LPM = 24 LPM Another Example: 50% FiO2 15 LPM
flowmeter on 15lpm
Total flow formula
flowmeter setting x factor
device used to deliver heliox
heliox should be delivered to patients via tight-fitting nonrebreathing mask with high flow
LPM, L/min
liters per minute (usually referring to oxygen delivery)
What is target oxygenation goal for patients with chronic hypercapnia?
paO2 greater than 60 can depress ventilatory drive in patients with hypercapnia - When breathing high oxygen concentrations, COPD patients with chronic hypercapnia tend to ventilated less
Appropriate initial O2 device for COPD patient
venturi mask
Minimum LPM for simple mask
ØAt a flow less than 5 L/min, the mask volume acts as dead space and causes carbon dioxide (CO2) rebreathing FiO2 range is 0.35 to 0.50 ØAir dilution easily occurs during inspiration through its ports and around its body, provides a variable FiO2 ØFiO2 varies depending on the O2 input flow, the mask volume, the extent of air leakage, and the patient's breathing pattern
oxyhood: what is it used for, what is the flow ranges to be set at, what temps should be set, what should be monitored, what happens when temps gets too low or flows get to high or low
ØOxygen hood (AKA: Oxyhood): Generally is best method for delivering controlled oxygen to infants ØIncubators (AKA Isolette): Can be used in conjunction with oxyhood
hyperbaric O2: treatment, computing barometric pressures for ATA, physiologic effects
ØThe therapeutic use of O2 at pressures greater than 1 atm Physiologic effects ØBubble reduction (Boyle's law) ØHyperoxygenation of blood and tissue (Henry's law) ØVasoconstriction ØEnhanced host immune function ØNeovascularization A multiplace chamber is a large tank capable of holding a dozen or more people ØHave air locks that allow entry and exit without altering the pressure. ØGenerally filled with air ØIf indicated, only the patient breathes supplemental O2 (through a mask or another device). Monoplace chamber can hold only one patient
