Critical care and ventilation Flashcards
what is mechanical ventilation
mechanical ventilation replaces the function of the inspiratory muscles by delivering gas under positive pressure to the lungs. this substitutes for the respiratory pump. respiratory pump= the abdominal and thoracic structures that contribute to the expansion and contraction of the lungs, if patient triggered- the ventilator delivers the breath as soon as it senses the beginning of the patient inspiration
compliance
compliance- reflects ability to change the shape of a structure when mechanical load applied, so lung compliance is the ability of the alveoli and lung tissue to expand on inspirations. Compliance varies depending on the elasticity and surface tension of lungs (stiffer lungs= less compliant= lungs are harder to mechanically ventilate)
indications to ventilate
respiratory failure (COPD), prolonged post op recovery (heart ,head, abdominal), altered conscious level (cannot maintain airway), inability to protect airway, respiratory failure- inadequate gas exchange as reflected in ABGs
What is PEEP
positive end expiratory pressure, pressure maintained in the alveoli at the end of expiration to prevent alveolar and airway collapse
volume controlled ventilation
ventilator delivers a pre set TV, pre set inspiratory time, pre set pause time, airway pressure tissues slowly as the ventilator reaches the desired volume
how does peak airway pressure vary
it varies from breath to breath as this mode is volume controlled and the ventilator will deliver its set volume irrespective of how hard that might be because of variations in lung compliance and resistance to flow
pressure controlled ventilation
flow is delivered to a pre set target pressure limit during inspiration, pre set respiratory rate, pre set inspiratory time, pressure is constant and set so the volume can change from breath to breath depending on lung compliance (better lung compliance leads to larger lung volumes and vice versa)
main advantage of pressure controlled ventilation q
pressure can be controlled reduce the risk of baraotruma in patients with stiff lungs
dual control ventilator
combines volume control and pressure control, delvers a pre set volume with the lowest possible pressure, if the volume falls below the pre set value the pressure level rises but only to a point, if the upper pressure limit is reached before the ventilator can deliver the appropriate amount of volume that has been set, the volume will alarm,
pressure support (PS) or AKA assisted spontaneous breath (ASB)
a spontaneous mode- so the patient must trigger the machine or there will be no breath given, provides a pre set pressure boost to each breath
volume support
spontaneous mode, a set TV is delivered with different pressure support from the ventilator depending on the patients effort/activity
biphasic positive airway pressure
pressure controlled mode giving the patient unrestricted opportunities for spontaneous breathing at pre set high and low pressure levels. uses 2 shifting pressure levels- IPAP and EPAP
automode
interactive mode, allow patient to receive a supported breath if triggered or a mandatory breath if not. allows for weaning
CPAP
provides positive pressure but with no mandatory breaths so the patient has to breathe spontaneously. it increases FRC improving gas exchange by splinting open alveoli. it delivers the same flow of gas through inspiration as expiration. can be delivered non invasively via a face mask
examples of spontaneous modes
such as PS, ASB, CPAP
