mechanical ventilation Flashcards
what is mechanical ventilation?
- a machine that generates a controlled flow of gas into a pts airway
- O2 and air are generated from cylinders or wall outlets
- the gas is blended according to prescribed “inspried oxygen tension”- FiO2
- its accumulated in a receptacle in the machine, then delivered to pt via one of many available modes
indications for ventilation
-ventilatory failure
-inability to protect airway
-failure to clear the airway
(ARB, allergic reactions, etc.)
airway accesses
-Noninvasive ventilation
-nasal cannula, face mask, non-rebreather mask,
BiPAP
-Laryngeal Mack airway (LMA)
-endotrachial tube
-tracheostomy (for prolonged intubation)
types of ventilators
- negative pressure ventilators
- positive pressure ventilators
- non-invasive ventilation
negative- pressure ventilation
-creates negative pressure externally to draw the chest outward and air into the lungs
-mimics spontaneous breathing
-used for individuals with neuromuscular disorders
“iron lung”
Positive pressure ventilation
- Pushes air into lungs
- can be invasive or non-invasive
- amount of air delivered in: volume (milliliters), specific pressure
- used for individuals with acute respiratory failure
BIPAP
noninvasive positive pressure ventilator
- provides ventilator support, but uses a tight fitting mask
- used to avoid intubation
- supportive for patients with: sleep apnea, impending respiratory failure
- success varies and is limited to pt tolerance
Positive pressure ventilators
- normal respiratory properties will be reflected in your mechanical ventilation settings
- mode (spontaneous vs. mechanical)
- depth (tidal volume)
- oxygen (FiO2)
- rate
controlled mechanical ventilation (CMV)
- mode of positive-pressure ventilation
- breaths are delivered regulatory and independent of the pts own ventilatory efforts
- used when pt has no drive to breathe (-under anesthesia, chemically paralyzed)
- very rarely used
assist-controlled mechanical ventilation (ACV)
-mode of positive-pressure ventilation
-vent breath is triggered by pt inspiration
-used: to initiate mechanical ventilation
those at risk for respiratory arrest
-if the pt does not initiate a breath in a preset time the vent fires a breath at the preset vent rate
allows pt to breath faster but not slower
synchronous intermittent mandatory ventilation (SIMV)
mode of positive pressure ventilation
- allows pt to breath spontaneously without vent assistance between delivered vent breaths
- -vent has preset rate and tidal volume and will not fire when the pt produces their own breath
- coordinated with the pts own respiratory effort
SIMV commonly used
- to support ventilation
- to exercise the respiratory muscles between vent-assisted breaths
- during weaning process
Respiratory rate - SIMV rate =
spontaneous breaths
Tidal volume (VT)
- the volume of air delivered during each ventilator-augmented breath
- normal adult VT is 6-10 mL/kg or approx. 400-500mL
- increased VT = increased risk of barotrauma & decreased venous return/ CO
- decreased VT = increased risk of atelectasis
Oxygen
- 3% of the body’s oxygen is dissolved in the plasma
- PaO2=partial pressure of oxygen (mmHg)
- measures how much oxygen is in the alveoli
- SaO2 (oxygen saturation) measures the degree of oxygen bound to hemoglobin
FiO2
- set at lowest possbile level for adequate tissue perfusion
- FiO2 can be 21-100% oxygen
- try to keep
hypoxemia
- abnormally low concentration of oxygen in blood
- results from ventilation or circulatory problems
- VQ mismatching (shunting)
rate of ventilations
- normal RR= 12-20
- initially set at approx. 12-15 vent breaths/min
Positive end-expiratory pressure (PEEP)
special ventiltor setting
- used to maintain postive pressure in the lungs at the end of expiration
- improves the VQ relationship and diffusion across the alveolar- capillary membrane
- prevents: atelectasis, reduces hypoxemia, allows for lower % of FiO2
pressure support ventilation (PSV)
- preset pressure delivery augmenting pt own respiratory effort
- applies positive pressure during “spontaneous” inspiration
- can be used with all modes of ventilation
- used to: over come dead space of circuit & pts airways, decreases the work of breathing
- pt must be doing some spontaneous breathing
continuous positive airway pressure (CPAP)
- special ventilator setting
- elevates end-expiratory pressure during spontaneous breaths
- used for intubated and non-intubated pts
- used ot: maintain open airways, decrease the work of breathing
CPAP mask or BiPAP?
-used to improve oxygenation on pts who can breath on their own
-used for those experiencing sleep apnea at night
masks must be tight on the face
complications of mechanical ventilation-improper tube placement
- inflated lung vs. uninflated lung
- gastric distention
- aspiration
- facial skin necrosis
- crepitus
- drying of eyes and mucous membranes
- stress
- claustrophobia
- *need to perform oral and nasal care every 4 hrs
complications of mechanical ventilation-hospital acquired pneumonia
normal respiratory defense mechanisms bypassed
-open epiglottis
-cough/gag reflexes inhibited/ impaired
-secretions often thick and tenacious
-increases risk of atelectasis
hand washing vital in preventionother complications of mechanical ventilation
- aspiration
- oxygen toxicity
- resp. acidosis/alkalosis
- failure to wean
- decreased BP & CO
- poss. liver and renal dysfunction
- increased ICP
- fistulas
- barotrauma
- fluid retention
- loss of muscular conditioning
- malnutrition
ventilator weaning
- the process of removing ventilator support and re-establishing spontaneous, independent breathing
- process depends on: preexisting lung condition
- duration of mechanical ventilation
- pts general condition-physically and psychologically
vent. weaning cont.
- SIMV and PSV are used for weaning
- when duration of mechanical ventilation has been longer and respiratory muscle reconditioning is needed
- duration of periods off the vent is gradually increased until pt can maintain adequate independent breathing for several hours
using SIMV to wean
number of vent assisted breaths are gradually decreased
-when pt is able to tolerate an SIMV of 4 bpm a T piece or CPAP weaning is attempted
using PSV to wean
- pressure support levels are gradually decreased
- when PSV is just enough to overcome ETT resistance; support is DC’d; pt is extubated
terminal wean
- gradual withdrawal of mechanical ventilation when survival without assisted ventilation is not expected
- nursing considerations
- need to discuss option with pt/family/SO
- When? Where? What?
- provide education and comfort
