B4.054 Respiratory Failure Flashcards
definition of resp failure
patient loses ability to ventilate adequately or to provide sufficient oxygen to the blood and systemic organs
significance of resp failure
one of most common reasons for ICU admission
>75% of patients require mechanical ventilation during their stay
immediate interventions for respiratory failure
arterial blood gases drawn on room air
O2 is started/ nasal cannula
peripheral IV is started
CBC and chemistries drawn
what drug reverses opiod overdoses
naloxone
Type 1 resp failure
hypoxic
what is a likely cause of hypoxic resp failure
low V/Q ratio (shunt)
intrapulmonary
poor oxygenation of blood through pulmonary capillaries
what are possible sources of shunts?
blood
pus- pneumonia
water- CHF
atelectasis
does shunting dramatically influence PaCO2?
no, much greater effect on PaO2
body can blow off extra CO2 pretty easily and maintain near normal
does giving more O2 help PaO2 when a shunt is present?
no
good alveoli cant compensate for the bad due to the shape of oxygen binding curve
cant increase O2 content much
type 2 resp failure
hypercapnic
what is a likely cause of hypercapnic resp failure?
respiratory pump failure
always accompanied by resp acidosis when acute
ratio of physiologic dead space to tidal volume
1/3
2 basic mechanism of hypercapnic resp failure
- decreased capacity (extrapulmonary) > decreased minute ventilation
- increased load (pulmonary parenchymal or airway disorders) > increased dead space
sources of decreased capacity
decreased central respiratory drive
neuromuscular disorders
thoracic cage disorders
sources of increased load
increased resistive load
elastic load
increased VE demand
is ventilation is halved
PaCO2 doubles
if PaCO2 raises 10 mmHg
pH decreases 0.08 points
alveolar ventilation equation
VA=(VT-VD)*RR
type 3 resp failure
occurs in perioperative period when factors that reduce functional residual capacity combine with causes of increased closing volume to produce progressive atelectasis
type 4 resp failure
ensues when circulation fails and resolves when shock is corrected
why is the alveolar-arterial (A-a) gradient useful
distinguishes hypercapnic respiratory failure due to global respiratory failure from respiratory failure due to abnormal gas exchange from intrinsic lung disease
normal A-a gradient
global hypoventilation
widened A-a gradient
underlying lung disease (intrapulmonary shunt)
indications for mechanical ventilation
- airway protection for a patient with decreased level of consciousness
- hypercapnic respiratory failure due to airway, chest wall, or respiratory muscle disease
- hypoxic respiratory failure
- circulatory failure, in which sedation and mechanical ventilation can decrease the oxygen cost of breath
