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72 Cards in this Set
- Front
- Back
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Hypoxaemic respiratory failure is present when the Pa02 is... |
<8kpa or <60mmHg on room air |
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Hypercapnic respiratory failure is present when PaCO2 is... |
>6.7kPa or >50mmHg on room air |
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List 4 different causes of acute respiratory failure |
low inspired partial pressure of oxygen hypoventilation VQ mismatch diffusion abnormality |
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Define partial pressure of oxygen |
Fi02 x barometric pressure |
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What factors determine the values of alveolar P02 and PCO2 |
- barometric pressure - partial pressure of inspired O2 and CO2 - Rates of total body O2 consumption and CO2 production - rates of alveolar ventilation and perfusion
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Which form of respiratory failure is characterised by both hypercapnia and hypoxia |
hypoventilation |
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what is the A-a gradient? |
gradient between the partial pressure of oxygen in the alveolus and the arterial blood |
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What is the alveolar gas equation? |
Pa02 = FiO2 (PB - SVPH20) - PaCO2/R+F |
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Normal A-a gradient should be less than? |
20mmHg |
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High A-a gradient in setting of respiratory failure suggests... |
VQ mismatch or diffusion abnormality |
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Normal A-a gradient in setting of respiratory failure implies... |
hypercapnia |
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List causes of hypoventilation |
drugs, anaesthesia encephalopathy, fatigue, spinal cord injury, GBS, paralytic agents, myasthenia gravis, dysfuncion of the muscles of respiration (myopathy, dystrophy), chest wall abnormalitis (ankylosing spondylitis) |
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Causes of ventilation perfusion mismatch |
pneumonia, PE, pulmonary haemorrhage/contusion, atelectasis intracardiac shunting (e.g. ToF, Eisenmenger) |
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Causes of increased dead space resulting in hypercapnia... |
hypovolaemia, PE, poor cardiac function or high intrathoracic pressures (from positive pressure ventilation) |
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Causes of diffusion abnormalities causes respiratory distress |
pulmonary fibrosis, pulmonary edema, ARDs |
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Clinical features of resp distress |
tachypnoea, use of accessory resp muscles, nasal flaring, paradoxical breathing, sweating, tachycardia, HTN, altered mental status, cyanosis |
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The oxyhaemoglobin dissociation curve describes the relationship between... |
(pulse oximetry) saturation and Pa02 |
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What confounding factors may alter pulse oximetry readings |
dark skin, false nails, nail polish, lipaemia, bright ambiet light, poorly adherent probe, excessive motion, carboxyhaemoglobin |
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In patients with normal lungs and CO, the end tidal carbon dioxide tension provides an estimate of... |
PaCO2 |
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Which masks are designed to deliver constant concentrations of oxygen from Fi02 of 0.24-0.5 regardless of patients inspiratory flow pattern and respiratory rate |
venturi masks (air entrainment masks) |
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List indicators which predict intubation difficulty |
severe facial injury short neck, obese or muscular (thyromental distance <6cm), limited neck/jae movements, protruding teeth, small mouth, long high curved palate, or receding lower jaw, obstructing lesions in the oropharyng or larynx |
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Complications of oropharyngeal airways |
mucosal trauma, worsening obstruction by pressing the epiglottis against the laryngeal outlet or displacing the tongue more posteriorly |
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Complications of nasopharyngeal airways |
epistaxis, aspiration, laryngospasm, esophageal placement |
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What volume/rate of air should be introduced by manual ventilation |
300-500ml at 10-16/min |
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How much air should be used to inflate an LMA cuff? |
Approx 20-204ml for adult sizes |
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Contraindications to using a LMA or iLMA |
inability to open mouth, pharngeal pathology, airway obstruction at or below the larynx, low pulmonary compliance or high airway resistance |
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Complications of LMA |
aspiration, gastric insufflation, partial airway obstruction, coughing, laryngo-spasm, post-extubation stridor |
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What is postive end-expiratory pressure |
the pressure in the alveoli at the end of expiration or PEEP |
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What is the equations for total airway pressure during inspiration? |
flow x resistance + (volume/compliance) + PEEP |
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The mean alveolar pressure is dependent on... |
set tidal volume or set inspiratory pressure inspiratory time PEEP |
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Alveolar ventilation = |
respiratory rate x (tidal volume - dead space) |
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What causes shear injury? |
repetitive collapse and re-expansion of alveoli and tension at the interface between open and collapsed alveoli |
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What complications may result from shear injury? |
pneumothorax, pneumomediastinum, pneumopericardium, surgical emphysema, acute lung injury |
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In what setting does gas trapping ocurr? |
if there is insufficent time for alveoli to empty before the next breath |
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Gas trapping is more likely to occur in patients with... |
COPD, asthma (when inspiratory time is long) or when respiratory rate is high |
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Ventricular wall tension/afterload = |
transmural pressure x radius / 2x wall thickness where transmural pressure = intracavity pressure - intrapleural pressure |
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What are the 4 main ventilator modes? |
volume pre-set assist control ventilation pressure pre-set assist control ventilation pressure support mode synchronized intermittent mandatory ventilation |
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What is the I:E ratio? |
ratio of inspiratory time usually set to 1:2 |
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What is the recommended starting point for PEEP |
5cm H2O
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Which trigger method (pressure or flow) results in greater breath synchrony? |
flow |
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In general, minute ventilation should be titrated based on.... |
pH ( PaCO2 if raised ICP) |
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T or F: Under normal circumstances, airway pressure approximates to alveolar pressure because resistance is low. |
True |
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T or F: under normal circumstances, airway pressure approximates alveolar pressure |
True |
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A patient is receiving mechanical ventilation. A maximum pressure alarm is triggered. What are the possible causes? |
ventilator: inappropriate settings, malfunction circuit: kinking, pooling of condensed water vapour ET tube: kinked, obstructed with sputum, blood, endobronchial intubation Patient: bronchospasma, decreased lung compliance, decreased pleural compliance, decreased chest wall compliance, patient-ventilator dysynchrony, coughing |
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List patient factors which ma cause high airway pressures in volume preset modes? |
bronchospasm, decreased lung compliance (pulmonary edema, consolidation, collapse), decreased pleural compliance (pneumothorax), decreased chest wall compliance (abdo distention), patient-ventilator dysynchrony, coughing |
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in patients with disease affecting the lung parenchyma, the alveolar pressure should be ... |
<30 cm h20 |
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Inadequate tidal volume will results in .... |
inadequate ventilation, respiratory acidosis |
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A significant discrepancy between the inspiratory and expiratory tidal volume usually indicates... |
a leak in the system (ventilator, circuit, ET tube, patient) |
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Define minute ventilation |
tidal volume x respiratory rate |
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What are the causes of hypotension occurring immediately after the initiation of positive pressure ventilation? |
- Hypovolaemia, exacerbated by reduced venous return due to positive intrathoracic pressure - Drugs used for induction of anaesthesia for intubation - gas trapping due to excessive ventilation - tension pneumothorax (rare) |
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Why are lower tidal volumes more appropriate in ARDs |
heterogeneous lung compliance (due to focal consolidations/collapse) means smaller volume of lung is being ventilated. Higher tidal volumes will cause overdistension |
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What tidal volume and plateau pressure settings are recommended in a patient with ARDS |
6-8ml/kg (predicted body weight) <30cm H2O |
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In patients with asthma, which measurement is more useful to determine ventilator settings: airway pressure or plateau pressure? |
plateau pressure (which is better surrogate for alveolar pressure in patients with asthma) |
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What PEEP total and plateau pressures should be used in patients with ashtma |
<10cm h2o <20 cm h20 |
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List indirect clinical measures of tissue blood flow? |
LOC, temperature of peripheries, urine output |
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Normal urine output |
>0.5-1ml/kg/hr |
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Describe the recommended BP cuff size for an individual? |
width: 40% of circumferance (most important) length: 2x circumference |
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Cuffs which are too narrow tend to ____ blood pressure |
overestimate |
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Cuffs which are too wide tend to __ blood pressure |
underestimate |
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Complications of blood pressure cuffs |
ulnar nerve injury, edema of the limb, petechiae, bruising, friction blisters, IVC failure |
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Complications of invasive arterial pressure monitoring |
distal ischaemia, arterial thrombosis, embolism, infection, haemorrhage, accidental drug injection, damage to artery (e.g. aneurysm formation) |
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Why is the brachial artery avoided for placement of arterial lines? |
It is end artery supply of forearm and is relatively small callibre/low flow rates (e.g. relative to femoral artery). Vessel thrombosis can compromise limb. |
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Which is a better determinant of left ventricular coronary blood flow, systolic or diastolic BP? |
diastolic |
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Minimal change (<3mm Hg) in central venous pressure 5 mins following a fluid bolus indicates.... |
end-diastolic volume is low (preload) |
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Significant change (>5mmHg) in central venous pressure 5 mins following a fluid bolus indicated... |
fluid overload, high end diastolic volume, high preload. |
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When is the use CVP changes to estimate preload likely to be inaccurate? |
patients with isolated left or right ventricular failure, valvular disease, severe pulmonary disease |
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Complications of central venous line insertion |
pneumothorax, haemothorax, chylothorax, damage to vein or adjacent structures, vein thrombosis, thrombophlebitis, eection, catheter or guidewire embolization, cardiac arrhythmias, haemorrage |
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Describe the passive leg raising test as a means of assessing fluid status? |
Change the patient from a 45 degree head up postion to a 45 degree leg up position,. A rise in pulse pressure (as measured with arterial line) by 10% or more suggests that the patient is hypovolaemic |
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Mean arterial pressure = |
cardiac output x total peripheral resistance or heart rate x stroke volume x total peripheral resistance |
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Cardiac output = |
stroke volume x heart rate |
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Stroke volume is dependent upon.... |
preload, afterload and contractility |
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List 5 types of shock? |
Cardiogenic, hypovolaemic, distributive, obstructive, neurogenic |
