Exam II Flashcards
what is mechanical ventilation?
- a method to mechanically assist or replace spontaneous breathing when patients cannot do it on their own
- patient must be intubated with either an ET or trach for direct delivery of air and O2
- the purpose is to minimize the work of breathing while promoting gas exchange
lung volumes
tidal: volume of air inhaled and exhaled with normal breathing.
inspiratory reserve: max volume or air inhaled after a normal inhalation
expiratory reserve: maximum volume that can be exhaled forcibly after normal exhalation
residual: volume remaining in lungs after maximum exhalation
lung capacities
vital: max volume exhaled from the point of max inspiration
inspiratory: max volume inhaled after normal expiration
functional residual: volume remaining in lungs after normal expiration
total lung: volume of air in lungs after a maximum inspiration and = VT, IRV, ERV, RV.
indications for mechanical ventilation
acute respiratory distress/failure - hypercapnia (failure to ventilate) - hypoxemia (failure to oxygenate) assessment parameters - PaO2 50mmHg, with a pH of 7.25 or less - respiratory assessment
resp. assessment: s/s adequate ventilation
- bilateral anterior chest expansion
- breath sounds present and equal bilaterally
- stable bp and hr
resp assessment: adequate oxygenation
- PaO2 within desired range
- regular respirations
- stable hemodynamic status
- absence of: dyspnea, central cyanosis, accessory muscle use
resp assessment: adequate breathing pattern
- adequate depth, timing, and rhythm
- symmetrical anterior chest expansion
- patient indicates comfort of breathing
- absence of: nasal flaring, retractions, accessory muscle use
resp. assessment: inadequate ventilation
- rising arterial paCO2 (ABG)
- chest-abdominal asynchrony, irregular respirations
- apnea, bradypnea
- restlessness, confusion, headache, lethargy
- rising (early) and falling (late) arterial BP (lack of perfusion)
- tachycardia, arterial and ventricular dysrhythmias
procedure for intubation
- lubricate ETT with gel
- maintain head position
- suction as needed (make sure it’s on!)
- insert ETT between vocal cords
- cricoid pressure PRN
- inflate cuff
- ventilate with ambu bag
- auscultate breath sounds b/l
- auscultate epigastric area
- check chest xray
types of mechanical ventilators
all ventilators work under the principles of 3 of the 4 cycling mechanisms
- volume
- pressure
- flow
- time
volume cycled ventilator
delivers a preset tidal volume, allows for passive expiration
most common in critical care setting
advantage: patient is guaranteed to receive a preset tidal volume under normal operating conditions
disadvantage: peak inspiratory pressure may increase to levels high enough to cause barotrauma or damage to healthy alveoli
bad with pneumonia, ARDS, and kyphosis.
pressure cycled ventilator
delivers a preset pressure, then allows for passive expirations
volume, flow rate, and inspiratory time all vary on a breath to breath basis
advantage: limits peak pressure which can damage the lungs
disadvantage: delivers a lower tidal volume with a decrease in lung compliance and/or increase in resistance.
inspiratory:expiratory ratio (I:E)
length of inspiration compared to length of expiration.
respiratory rate:
# of breaths delivered by the ventilator per minute usual parameters: 4-20bpm
tidal volume
vol of gas delivered during each ventilator breath
usual parameters: 5-15mL/kg
fraction of inspired oxygen (FiO2)
percent of oxygen delivered by the vent to the patient
usual parameters: 21% to 100%; usually set to keep PaO2 >60mmHg or SaO2 >90%
pressure limit
maximum amount of pressure the ventilator can use to deliver a breath
usual parameters: 10-20 cm H2O above peak inspiratory pressure; maximum is 35 cmH2O
peak flow/flow rate
speed with which the tidal volume is delivered
sensitivity
controls the amount of patient effort needed to initiate an inspiration
sigh
delivers an occasional sigh with a larger tidal volume
tidal volume calculations
PBW formulas (kg) - Men: 50 + 2.3 (height[in] - 60) - Women: 45.4 + 2.3 (height[in] - 60) Ideal body weight (pounds) - Men: 106 + 6 (height[in] - 60) - Women: 100 + 5 (height[in] - 60) multiply by 8-10mL/kg to bet tidal volume
modes of mechanical ventilation
described by the pressure, flow, and volume patterns that occur over time. It refers to how the machine will ventilate the patient in relation to the patient’s respiratory effort.
Four types:
- Controlled Mandatory Ventilation
- Assist-Control Ventilation
- Synchronous Intermittent Mandatory Ventilation
- Pressure Support Ventilator
controlled mandatory ventilation
- delivers a preset volume or pressure regardless of patient’s own inspiratory effort
- used in patients who are unable to initiate a breath spontaneously
- spontaneous breathing patients must be sedated and/or paralyzed
Advantage: - no respiratory effort needed (also the problem)
Disadvantage: - long term use leads to muscle atrophy
rarely used
assist-control ventilation
- delivers breath in response to patient effort and if patient fails to do so within preset amount of time
- used for spontaneously breathing patients with weakened respiratory muscles
- patient initiates breath, machine delivers tidal volume.
Advantage - tidal volume guaranteed by ventilator, unless maximum airway pressure pattern exceeded
Disadvantage - ventilator assistance can lead to hyperventilation and respiratory alkalosis
- potential for muscle atrophy
SIMV
- ventilator breaths are synchronized with the patient’s respiratory effort
- used to wean patients from mechanical ventilation
Advantages - breaths are synchronized with patient effort
- mode allows for patient “exercise”
Disadvantages - increased work of breathing and respiratory muscle fatigue
patients may be on A/C at night.
pressure support ventilation
- preset pressure that augments the patient’s inspiratory effort and decreases work of breathing
- used with SIMV to overcome the resistance of breathing
Advantage: - helps lower peak and mean airway pressure
Disadvantages: - mode dependent upon patient initiating their own breath
- less compliant the lungs, the less volume inspired with each breath.
can be used in conjunction or by itself.
Mechanical ventilation adjuncts: PEEP
pressure applied at the end of expiration
used as adjunct to CMV, AC, and SIMV to improve oxygenation by opening collapsed alveoli
side effects:
- increased intrathoracic pressure leading to decreased venous return and decreased cardiac output
- increased risk of barotrauma
- pneumothorax
- increased intracranial pressure
Mechanical ventilation adjuncts: Continuous Positive Airway Pressure (CPAP)
- similar to PEEP, but used only with spontaneously breathing patients
- constant positive pressure in airways so resistance is decreased
- may be administered by mask and CPAP machine for patient who do not require mechanical ventilation, but need respiratory support
Mechanical ventilation adjuncts: Bi-level Positive Airway Pressure
- non-invasive form of mechanical ventilation provided by means of a nasal mask, nasal prongs, or a full face mask.
- the pressure varies with each breath cycle when the user inhales similar to CPAP. When they exhale, the pressure drops, making it much easier to breathe.
- inhale, pressure rises, exhale, pressure drops.
newer, not as commonly used.
airway pressure alarms
high
- kink in vent tubing
- secretions in ETT/airway, or condensation in tubing
- patient coughing, gagging, or biting ETT
- increased airway pressure from bronchospasms or pneumothorax
- patient trying to talk.
low
- leak in ventilator/patient circuit
- vent tubing not connected
- displaced ETT or trach tube
low exhale volume tube
- vent tubing not connected
- leak in ventilator/patient circuit
- leak in cuff or inadequate cuff seal
- occurrence of another alarm preventing full delivery of breath
apnea alarm
- ventilator disconnected from patient
- tubing disconnected along circuit
- patient is apneic
apnea test: silence alarm, turn off, see if patient breathes.
complications of mechanical ventilation: airway & ETT
airway: - aspiration: epiglottis can't close - decreased clearance of secretions - nosocomial or VAP ETT: - tube kinked or plugged - tracheal stenosis - cuff failure - sinusitis - laryngeal edema: damage vocal cords, scrape larynx
complications of mechanical ventilation: mechanical
- hypoventilation with atelectasis
- hyperventilation with hypocapnia and respiratory alkalosis
- barotrauma
- failure of ventilator alarms
- overheated inspired air, hyperthermia
- inadequate nebulization or humidification
complications of mechanical ventilation: physiological
- fluid overload with humidified air and sodium chloride retention
- depressed cardiac function and hypotension
- stress ulcers (H2, PPIs)
- paralytic ileus (decreased motility)
- gastric distension (NGT)
weaning from mechanical ventilation
process of removing a patient from mechanical ventilation via:
- T-piece with CPAP
- SIMV
- Pressure Support Ventilation
once respiratory and nonrespiratory factors have been considered, ventilatory support can be withdrawn rapidly or gradually.
weaning parameters
- respiratory rate:5 and 300mL
- NIF: >-20-25 H2O
- PaO2 >70mmHg, FiO2 <50% and PEEP of 5cm H2O or less.
rapid shallow breathing index
RSBI= respiratory rate/tidal volume
Normal less than 105
occlusion pressure (PO.1)
normal 2-6cm H20
pacemakers: timing circuit
- pulse repetition: programmed for fixed rate
- pulse duration: how long pulse happens
- refractory (rest) period: time before it happens again.
pacemakers: sensing circuit
- detects intrinsic cardiac activity
- sensing threshold: minimal cardiac activity that activates sensing circuit and PREVENTS (inhibits) pacer from firing.
lead placement
- endocardial/transvenous: threaded thru vein and advanced to heart
- myocardial/epicardial: attached to outside of heart. leads screwed into side of heart, wires come through incision.
- external/transcutaneous: pacer pads
- transthoracic: bunch of needles
lead fixation
transvenous - passive: lodged in trabeculae - active: screws into endocardium. more permanent. leads can be placed anywhere. myocardial/epicardial - stab, screw, or suture
synchronized vs. asynchronized pacing
synchronized is on demand - only occurs when necessary - rate is usually modulated/varies based on metabolic demand & intrinsic rate - sensing, can be rate responsive - kicks in if rate is dropping below 60 asynchronized pacing is fixed - every beat is paced - intrinsic rate be damned! - risk for R on T - 100% pacing
pacemaker capture
- the depolarization and resultant contraction of the atria or ventricles in response to an electrical stimulus emitted by a pacemaker
- one-to-one capture occurs when each electrical stimulus causes a corresponding depolarization and resultant cardiac contraction
pacemaker sensing
- definition: the ability of the pacemaker to sense an intrinsic electrical signal.
- the sensitivity setting of the pacemaker indicates the minimum intracardiac signal required by the pacemaker to initiate the pacemaker response (inhibited or triggered).
QRS complexes and pacemakers
- due to the location of ventricular lead implantation, the QRS complex may be widened
- depolarization of the ventricle may not follow the normal pathway (BB–>purkinje fibers).
pacemaker malfunction: failure to pace
- intrinsic cardiac depolarization
- oversensing: minimal activity required. Sensing things that aren’t there.
- broken, dislodged, disconnected leads
- impending battery depletion
pacemaker malfunction: failure to capture
- fibrosis at lead-tissue interface: pull out lead. firing, but can’t get through scar tissue.
- drugs or conditions with increase pacing threshold
- crosstalk inhibition with dual-chamber devices: feedback. close enough to interfere with one another. don’t want leads side by side.
pacer problems: undersensing and causes
an intrinsic depolarization that is present, yet not seen or sensed by the pacemaker (not detecting activity that it should)
ventricular dysrhythmia caused by pacer firing during vulnerable phase of T wave is of concern.
Causes:
- inappropriately programmed sensitivity
- lead dislodgment (may be floating back and forth)
- lead failure: insulation break; conductor fracture
- lead maturation
- change in the native signal: intrinsic rate, sensitivity changes
pacer problems: oversensing and causes
the sensing of an inappropriate signal. can be physiologic or nonphysiologic Causes: - lead failure - poor connection at connector block - exposure to interference
pacer problems: noncapture and causes
no evidence of depolarization after pacing artifact
Causes:
- lead dislodgment
- low output: poor batteries, leads, settings
- lead maturation
- poor connection at connector bloc
- lead failure
pacer problems: no output and causes
pacemaker artifacts do not appear on the ECG pacer rate is less than the lower rate - poor connection at connector block - lead failure - battery depletion - circuit failure
pacemaker complications
- pneumothorax
- ventricular irritability
- perforation: septum; ventricle–>tamponade
- catheter/lead dislodgment
- infection/hematoma
- pocket erosion
implantable cardioverter defibrillator: indications
- to prevent sudden cardiac death
- for heart failure patients (NYHA class II and III [IV not eligible]) with ventricular arrhythmias.
- survived v.fib and v.tach.
cardiac resynchronization therapy
- pacing system in which both ventricles are paced
- the atria may also be paced
- can be used with an ICD and is called CRT-D
ICD implantation procedure
- transvenous, single incision
- local anesthesia, conscious sedation
- programmable therapy options
- single, dual, and triple chamber
- up to 9 years longevity
- > 200,000 implants/year
the ICD system: how it works
atrium & ventricle: - bradycardia sensing - bradycardia pacing - antitachycardia pacing ventricle: - VT prevention - ATP - cardioversion: detects lethal dysrhythmias - defibrillation
nursing care: ICD pre-procedure
- diagnostic tests (EPS)
- continue antiarrhythmics
- education about the device (don’t just hand them a pamphlet)
- NPO, IV site
nursing care: ICD during procedure
- conscious sedation/anesthesia
- continuous monitoring of EKG, vital signs, pulse ox
- administer other mediations PRN (Versed, Medazolam)
nursing care: ICD post procedure
- continuous monitoring: if fires while patient is in recovery, we need to know
- interrogation of device
- contact physician if device fires
- psychosocial support
- join a support group
respiratory parameter: PaCO2
- normal by-product of cell metabolism
- measurement of ventilation: the faster the patient breathes, the more CO2 is blown off
- CO2 and pH are inversely proportional
causes of respiratory alkalosis
- hyperventilation
- anxiety/pain
- fever
HYPERventilation
causes of respiratory acidosis
- respiratory failure
- airway obstruction
- drug overdose/sedation
HYPOventilation
metabolic parameter: HCO3
- measures the metabolic (renal) component and indicates the amount of bicarbonate (buffering)
- As HCO3 rises, the pH also increases
- HCO3 and pH are directly proportional
causes of metabolic acidosis
increased acids:
- shock/hypoxia (lactic acidosis from anaerobic metabolism), renal failure, DKA, salicylate poisoning
Loss of base:
- diarrhea, intestinal fistulas
causes of metabolic alkalosis
loss of acids:
- vomiting, NGT suctioning, diuretics
gain of base:
- excess use of bicarb/LR, lactate admin in HD, excess use of antacids
