Assessment of seriously ill patient/acute respiratory failure Flashcards
What is mean arterial pressure
The average blood pressure in an individual during a single cardiac cycle.
Map can be estimated by DP+1/3PP where PP is SP-DP
Describe the AA gradient
AA gradient described the difference between estimated PAo2 using alveolar gas equation and Pao2 measured in arterial blood
usually <20mmhg if higher then this suggest VQ mismatch or diffusion abnormality
Discuss causes of low VQ mismatch (shunt)
Collapsed or occluded alveolar by fluid, blood or pus reduce ability to diffuse o2. Alveola remain relatively well perfused however in time hypoxic vasoconstriction will occur cause less blood to flow to the poorly ventilated alveolar
Describe cause of high VQ mismatch (increased dead space)
Occlusion of pulmonary vasculature IE pulmonary embolism reduced blood flow to well ventilated alveolar
relatively little hypoxia and as long as nil fatigue increased minute ventilation will maintain normocapnia
Describe cause for hypoventaliation causing hypoxic failure
CNS depression: drugs, trauma, encephalitis
Bellow: trauma, neuromuscular disease GB, myasthenia gravis, kyphoscoliosis
Disruption of signal from CNS to affector: spinal injury GB
Decreased lung compliance
Describe causes of VQ mismatch
Low: Pneumonia, pneumo/haemo, pulmonary odema
High: PE
Anatomical shunting: hypoxic congenital cardiac disease
List the maximum fio2 that can be achieved with different o2 delivery systems and whether they are fixed or variable device
Nasal prongs: fio2 .4 variable not well tolerated at higher flow rates as dries nasal canal
Highflow nasal cannulae: fio2 .6 variable deliver warm humidified air. If mouth remains closed 1mmhg of CPAP can be achieved also reduces deadspace by flushing oropharynx
Air entrainment masks (venturi): fio2 0.24 to 0.5 constant delivery used when it is necessary to deilver a known fio2 accurately. Achieved by high gas flow rates
Non rebreather: fio2 .7 at 15l as no seal is obtained and atmospheric air is breathed
BVM: fi2 1 if seal is achieved PEEP valve available and can be used to deliver spontaneous oxygen in those breathing
List factors to be considered when deciding to ventilate a patient
- Degree of respiratory failure
- Response to oxygen delivery system
- CPR – reduced reserve should be ventilated early
- adequacy of compensation patient failing to compensate should be ventilated early
- increased ventalitory demand (IE sepsis, severe metabolic acidosis)
- expected length of course of illness
- risk of complications with ventilation ie asthma increased risk of iatrogenic pneumothorax
- need for mechanical ventilation to secure airway (ie surgery)
Identify factors that may lead to difficult intubation
- Structural upper airway obstruction
- severe traumatic facial injury
- anatomical/disease related features of difficult intubation
- – short neck, obese or muscular (thyromental distance of <6cm)
- –limited neck and jaw movments (trismus, arthritis)
- protruding teeth, small mouth, high curved palate or receeding jaw
- obstructing lesions in the oropharynx and larynx
Discuss contraindication and complications of LMA and ILMA
Contraindications:
- inability to open the mouth
- pharayngeal pathology
- aiway obstruction below the level of the larynx
- low pulmonary compliance of high airway resistance
Complications:
- aspiration
- gastric insufflation
- partial airway obstruction
- coughing
- laryngo-spasm
- post extubation stridor
List complications of ET intubation
Occurring during intubation
- incorrect tube placement
- -pharyngo-laryngeal trauma
- -htn and tachycardia
- -increased ICP
- -hypoxaemia
- -aspiration
While the tube is in place
- -blockage
- -dislodgement
- -tube deformation
- -damage to larynx
Following extubation
- aspiration
- post-extubation airway obstruction
- -laryngeal and tracheal stenosis
