2 respiratory support Flashcards
General methods / options for respiratory support?
- o2 therapy
- positive pressure ventilation
- humidification of inspired gases
- aerosol therapy
What is the primary indication for o2 therapy?
hypoxia
What are some conditions that may lead to hypoxia?
- inadequate inspired o2
- impaired pulmonary function
- ineffective o2 transport
- inc o2 demand [NOT met by normal o2 delivery]
What are objective measures to determining the need for o2 therapy in a patient?
And subjective signs?
- arterial blood gas (PaO2
What are some methods for o2 administration?
- face mask/flow by/nasal prongs
- baggie, e collar, hood
- o2 cage, chamber, tent
- intranasal catheter
- intratracheal catheter
- nasotracheal catheter
- endotracheal tube
- tracheostomy tube
When might an oxygen tent be employed?
- patient is sedated or depressed
- short term use
- often immediately post op
Some benefits to intranasal o2 supplementation?
a down side?
- have more control over % o2 animal is getting
- designed for more extended care
- more secure
- anchor tubes so more invasive
When inserting a intranasal tube, what is landmark on face of animal to measuring the length of the tube?
What is the basic procedure?
- medial canthus of the eye (or level of upper 4th pre molar)
- deaden area, measure tube, mark tube, puncture lateral canthus of nose with needle, put suture through needle, tie a square know, INSERT TUBE INTO VENTRAL MEATUS, thread straight, surgeon’s knot around top then secure suture to top of patient’s head
general procedure to intratracheal o2 supplementation?
- clip and prep neck
- caution to NOT introduce environmental pathogens
- puncture directly into trachea w/o filtration of nose first
B/c the filtration of the nose is lost with intratracheal o2 supplementation, what special consideration should be made?
flow rates slower than when tube goes into nose
also a softer catheter is used
when comparing intranasal vs intratracheal o2 administration, which yields more o2 delivery?
intratracheal
direct delivery into the trachea is same o2 flow rate but 1.5x more o2 reaches lungs - better effects
What is the main guideline for o2 administration?
- flow rates
- resultant FiO2 and PaO2
- the clinical patient’s physiological state may dictate higher or lower flow rates
What is the upper limit to PaO2 typically?
What situation is an exception?
- above 100 mmHg usually has limited benefit b/c SaO2 is 97%+ [Hb is saturated at this point}
- except in SIRS [patient needs all the help it can get and may rely on o2 dissolved in blood, whereas most patients only benefit from o2 on Hb]
Why is trachea delivery of o2 more efficient method?
- trachea serves as oxygen rich reservoir
- lower flow rates are more economical
Factors to influence choice btwn IN (nasal) or IT (tracheal) administration of o2?
- clipping and aseptic prep req for IT placement
- nasal trauma or dz may preclude use of IN tube
- upper airway obstruction must be INCOMPLETE to use IT o2 b/c obstruction may px escape of excessive IT flow
prolonged levels of what % o2 can lead to oxygen toxicity?
50-60%
How to monitor o2 therapy?
- clin signs: resp rate, character of resp, mucous mem color
- pulse oximetry
- arterial blood gas
describe function of pulse oximeter
- commonly used
- probe on tongue in anesthetized patient
- one side has diode that emits red and infrared light and other side has detector - light is sent through tissues and detected on the other side
What does the value from a pulse oximeter tell you?
- % of oxygenated Hb in Aa
- equal to SaO2 in arterial blood gas
Guidelines to weaning a patient off oxygen therapy:
- monitor clin signs
- monitor SpO2
- serial arterial blood gas
- trials off 02: re institute o2 administration as indicated and see if clin signs come back
what clinical signs indicate re institution of o2 therapy?
- clin signs of hypoxia
- inc resp rate
- abnormal respiratory rate
- pale, cyanotic, or “muddy” mucous membranes
- Sp02 (SaO2) less than 96% [ b/c at 90%, it drops of VERY fast ]
- PaO2 less than 80 mmHg
complications with o2 therapy?
- apnea in patients w severe respiratory dz: loss of hypoxic ventilatory drive
- intra pulmonary shunting
- o2 toxicity
Clinical manifestations of o2 toxicity?
- pulm edema
- atelectasis
- consolidation
- congestion
- hemorrhage
- fibrosis
- functional impairment
What is tricky about clinical manifestations of o2 therapy?
they are the same signs that would trigger the initiation of oxygen therapy
use judgement and knowledge of patient history to decide
oxygen toxicity pathogenesis?
- cytotoxic peroxides and free radicals
- result of excessive PaO2, but described in terms of FiO2:
microscopic changes and clin signs after 24 hours of 100% FiO2
death after 2-3 days of 100% FiO2
what level of FiO2 is apparently safe for long term o2 delivery?
50%
Indications for positive pressure ventilation?
- ventilatory failure: PaCo2 > 55mmHg
- failure of o2 therapy to reverse hypoxia
- adjunctive Tx for intracranial hypertension
Considerations with positive pressure ventilation in situations of intracranial hypertension cases / concern?
- physiologically, high PaCo2 causes vasculature of cerebrum to dilate, allowing more blood into cranial vault
- but space is limited in cranial vault
- ventilate to bring down PaCo2 and constrict vessels to control pressure necrosis
- BUT do not ventilate too much or the vessels constrict too much and not enough blood can get into cranial vault
Techniques of positive pressure ventilation?
- manual: anesthesia machine bag and ambu bag
- mechanical: controlled vs assissted OR pressure vs volume cycled
What is PEEP (positive end expiratory pressure) and CPAP (continuous positive airway pressure) used for?
- to treat alveolar collapse: help alveoli stay open longer to allow more time for gas exchange to occur
- do dec the work of breathing
- also helps maintain a more consistent flow
What are typical PEEP or CPAP settings to maintain PaO2 or Spo2 at acceptable levels?
5-10 cm H20
When is positive pressure ventilation and PEEP used?
- when o2 therapy fails - 100% inspired o2 fails to achieve normoxia
- greater than 50% inspired o2 is required to maintain normoxia, putting the patient at risk for o2 toxicity
What is high frequency ventilation?
- high respiratory rate and low tidal volume
- works by diffusion of gases along concentration gradient
An advantage to high frequency ventilation?
- low mean airway pressure
- can be used in presence of tracheal disruption
when/how to wean patient from ventilatory support?
- begin when animal is stable on the ventilator
- gradual reduction in minute ventilation to allow PaCo2 in inc enough to stimulate spontaneous ventilation
- monitor blood gases, SpO2, ETCO2 and respiratory pattern
T/F: alveolar air is normally 100% humidified at body temperaturs
TRUE
What are the effects of dry medical gases?
- inc humidification requirement
- inc vaporization leading to cooling of liquid surfaces and patient heat loss
- mucosal drying
Effects of mucosal drying?
- inc viscosity of secretions
- impaired mucociliary transport
- retention of tenacious secretions
- mucosal inflammation and degeneration
- small airway closure, atelectasis and inc shunting
- dec residual capacity
- dec pulmonary compliance
- inc risk of infection
What types of humidifiers are there?
- bubble humidifiers
- heated bubble humidifier
- humidity exchange filters
- nebulizers
What is an aerosol?
a fine suspension of liquid droplets in a carrier gas
What is aerosol therapy used for?
Delivery of substances to respiratory surfaces to:
- px desiccation (water)
- loosen secretions and stim coughing (saline)
- treat resp dz (drugs)
What factors affect aerosol deposition into patients airways?
- particle size: smaller particles deposit in more peripheral (deeper) airways
- rate and depth of breathing
Where does slow/deep breathing deposit aerosol particles?
And rapid/shallow breathing?
slow/deep -> peripheral airways
rapid/shallow -> upper airways
types of nebulizers?
purpose?
jet
babbington
ultrasonic
to break liquid into smaller particles
how does a jet nebulizer work?
stream of gas over immmersed capillary tube
how does a babbington nebulizer work?
stream of gas from sphere or like surface onto which fluid is dropped
how does an untrasonic nebulizer work?
- piezoelectric crystal
- oscillations of reservoir cause particles to eject from liquid
methods of aerosol administration?
- mask, enclosure, breathing circuit
- 15-20 mins every 4-8 hours
- maintain patient hydration
- thoracic physiotherapy (coupage)
- bronchodilators
- sterile delivery system
T/F: aerosol therapy can be used indefinitely and long term for a patient
FALSE
limited to 15-20 mins q 4-8 hours
to prevent over hydration
what is the purpose of thoracic physiotherapy? often used with aerosol therapy
to help loosen respiratory secretions
coupage
why is bronchodilator therapy often used with aerosol therapy?
to facilitate particle delivery
what drugs can be delivered via nebulization?
- abx: aminogylcosides
- bronchodilators: aminophylline and beta 2 agonists
