Airway

Question 1

What are the types of tracheostomy?

Answer 1

1. Upper airway absent
   –> End stoma formed when pt has had laryngeal resection. There is no upper airway connection to the lungs.
2. Upper airway present
   –> surgical tracheostomy: performed under direct vision, surgical cut is made in trachea
   –> Percutaneous dilatational tracheostomy: seldinger technique used to dilate needled hole

Most important difference is between laryngeal stoma, in which case there is no remaining upper airway connection with the lungs, and those forms of tracheostomy that allow management of upper airway if problems arise

Question 2

Indications for tracheostomy

Answer 2

Upper airway obstruction

Post laryngeal/upper airway surgery

MSK disorders affecting ventilation (muscular dystrophy, spinal cord injury, motor neurone disease, post traumatic brain injury)

To assist weaning from ventilation on critical care
–> Reduced airway resistance
–> Improved airway toilet
–> Allows reduction in sedation as better tolerated than oral tube

Incompetent swallow/impaired upper airway reflexes

Question 3

What are the types of tracheostomy tubes?

Answer 3

Cuffed: used if airway seal is required (e.g. for intermittent ventilation in critical care)

Uncuffed: if long term tracheostomy as less likely to cause trauma (which is usually due to cuff pressure)

Unfenestrated: Usually used in association with cuffed tracheostomy tube when intermittent ventilation is required, e.g. in surgical patients

Fenestrated: allow upper airway flow for phonation, designed for medium to long term use

Question 4

What are the most common problems with tracheostomies?

Answer 4

-Displacement
-Obstruction
-Haemorrhage

DOH!

Question 5

How can you determine the chronicity of type 2 respiratory failure?

Answer 5

Chronic type 2 resp failure (e.g. copd) patients will have high bicarb

Question 6

What are the causes of respiratory failure in the surgical patient?

Answer 6

1. Acute fall in functional residual capacity (FRC) without pulmonary vascular dysfunction:
   –> Failure of chest mechanics after trauma or other processes which render lungs stiff/non compliant
   –> Post op atelectasis, sputum retention, pneumonia, pharmacological respiratory depression (analgesia, sedatives, neuromuscular blocking drugs)
2. Acute fall in FRC with pulmonary vascular dysfunction
   –> PE, ARDS, LVF
3. Airflow obstruction
   –> asthma, COPD

Question 7

What factors increase risk of respiratory problems?

Answer 7

-Hx asthma/copd
-Smoking
-Obesity
-Thoracic surgery
-upper abdominal surgery
-Older age

Question 8

How to prevent respiratory compromise following surgery

Answer 8

-Identify those at risk
-Encourage early mobilisation
-Provide adequate analgesia
-Chest physio
-Nebulised salien
-Humidified oxygen at titrated dose
-Sputum culture

Question 9

System for interpreting chest XR

Answer 9

Soft tissues (emphysema, foreign body)
Bones (ribs, sternum, clavicle)
Lung markings (does it extend all the way to edge)
Opacifications
Costophrenic angle
Abdominal abnormality: air under diaphragm, dilated bowel loops
Heart size/position/trachea

Question 10

Increasing escalation of respiratory support

Answer 10

Mask oxygen therapy –> mask/tracheal CPAP –> NIV –> Intubation and ventilation –> PEEP and recruitment –> adjunctive therapies

Question 11

When would CPAP be helpful? What is its mechanism?

Answer 11

-Type 1 respiratory failure
-During ventilation, airway pressure cannot drop below pressure indicated on the valve

This leads to:
–> recruitment of underventilated alveolae
–> increased FRC
–> Decreased intrapulmonary shunt (when blood passes through lungs but fails to take part in gas exchange)
–> decreased work of breathing

Question 12

Patient selection for CPAP

Answer 12

-Must have reasonable resp rate and tidal volume
-Must be in control of airway
-Must be able to cooperate

Question 13

When would NIV be used?What is it?

Answer 13

-Type 2 respiratory failure

-Two different pressures applied to pt via a facemask: higher pressure during inhalation, lower pressure during exhalation
-This is bilevel positive airway pressure mask ventilation (BIPAP)
-Ventilation is predominantly provided by iPAP, whereas ePAP provides recruitment of underutilised alveoli allowing for gas exchange and removal of exhaled gas

https://geekymedics.com/cpap-vs-niv-bipap/

Question 14

Which patients would not be suitable for NIV?

Answer 14

-cardiovascularly unstable
-Decreased level of conciousness
-Severe metabolic acidosis
-Poor respiratory rate
-Must be in control of own airway
-Must be able to cooperate

Question 15

What is minute volume in ventilation?

Answer 15

-Volume of gas inhaled or exhaled from person’s lungs per minute

Question 16

How can minute volume be altered?

Answer 16

-Altering tidal volume or rate of respirations
-The greater the minute volume, the greater the removal of carbon dioxide
-However if tidal volume is too high, barotrauma may result
-Low tidal volume approach delivers best outcomes

Question 17

What is high flow nasal oxygen?

Answer 17

-Can deliver up to 100% o2 with high flows and high humidity
-Positive airway pressure comparative to low pressure CPAP is delivered which helps work of breathing
-Generally well tolerated, allows communication and oral nutrition
-Usually used for type 1 respiratory failure in surgical patients

Question 18

What is synchronised intermittent mandatory ventilation? What is controlled mandatory ventilation?

Answer 18

-SIMV preserves some of patients respiratory muscle activity by synchronising ventilation around the patient’s own respiratory effort

-Controlled mandatory ventilation: requires full sedation due to compulsory positive-pressure breaths from ventilator. Allows pt to play no part in breathing and is rarely used

Question 19

What is PEEP?

Answer 19

-Pressure is administered during expiration to prevent airway collapse and recruit underventilated alveoli

Question 20

When can ventilatory weaning be attempted?

Answer 20

-When original cause of respiratory failure has been treated successfully
-Sedative drugs have been reduced to a level at which they will not depress respiration
-Low inspired oxygen concentration maintains normal paO2
-CO2 elimination is no longer a problem
-Sputum production is minimial
-Nutritional status, minerals, trace elements are normal
-Neuromuscular function of diaphragm and intercostals are adequate
-Pt is reasonably cooperative

However baseline function must be considered

Question 21

What is atelectasis? What causes it?

Answer 21

-Absence of gas from all or part of lung
-Commonly seen following abdominal and thoracic procedures

Casued by:
-Reduced lung expansion from pain and splinting of diaphragm (reduced contraction to avoid pain)
-Leads to retention of secretions, distal airway collapse
-Exacerbated in the elderly/overweight/smokers/those with pre-existing lung disease

Question 22

How is atelectasis treated?

Answer 22

-Physiotherapy
-Mobilisation
-Incentive spirometer
-High flow o2 if available

Question 23

What are the most common organisms for hospital acquired pneumonia?

Answer 23

-MRSA
-Pseudomonas
-Enterobacter
-Serratia

Question 24

How is PE treated?

Answer 24

-usually LMWH initially then NOAC
-UFH infusion if moderate risk of bleeding
-In very high risk patients, IVC filter
-D/w haematology if unsure

Question 25

Normal ranges for ABG components:

Answer 25

-pH: 7.35-7.45
-PaCO2: 4.5-6 kpa
-Hco3-: 24-28 mmol/L
-Base deficit/base excess: normal range +2 to -2
-PaO2: 10-14
-Serum lactate: <1.2
-Anion gap: 10-15

Question 26

What is the anion gap?

Answer 26

–> AG = ([Na+] + [K+]) - ([Cl-] + [HCO3-])

Raised anion gap:
–> increase in unmeasured anions (e.g. lactate and ketones)

Normal anion gap
–> total concentration measured anions are unchanged
–> most commonly following overuse of NAcl, also seen after bladder surgery and ileal conduit formatoion

Question 27

How are hydrogen ions produced?

Answer 27

-As a result of production of CO2 (excreted by lung-controlled by chemoreceptors in medulla)
-Small amount produced as products of metabolism: excreted by kidney
-Therefore 2 methods of H+ ion homeostasis: renal and respiratory

Question 28

Describe the respiratory control mechanism of pH

Answer 28

-Rapid response system that requires normal CNS function (central pH chemoreceptors) and lung function to allow CO2 to be transferred from pulmonary venous blood to alveolar gas and excreted in expired gas

-Dysfunction of mechanics/control of respiration causes retention of CO2 and rise in H+ ion concentration (respiratory acidosis) or overexcretion and fall in H+ concentration (respiratory alkalosis)

Question 29

Describe the renal control mechanism of pH

Answer 29

-Slower responding system that depends on excretion of H+ ions in urine by distal nephron

Conditions that impair renal function will prevent H+ excretion resulting in metabolic acidosis

e.g.
–> obstructive uropathy
–> circulating volume depletion

Question 30

Describe the acid buffer equation

Answer 30

Left side volatile (respiratory) right side non volatile (renal)

Question 31

Describe respiratory acidosis

Answer 31

-Retention of CO2 causes rise in H+ by driving acid-base equation to the right
-Kidney responds slowly over 48 hrs to compensate by increasing H+ excretion in distal nephron, returning H+ towards normal, although normality cannot be achieved

Question 32

Describe metabolic acidosis

Answer 32

Inability of kidney to excrete non-volatile H+ ion or sudden increase in non-volatile acid load (e.g. in sepsis) will drive equation to the right and resp function will rapidly respond by increasing minute volume, reducing CO2 and cause H+ to return to normal

Question 33

Describe respiratory alkalosis

Answer 33

-Results when minute ventilation is higher than required to maintain appropriate PaCO2
-PaCO2 is driven down and H+ falls (pH rises)

Causes
-This is usually caused by increased central respiratory drive commonly caused by fever, hepatic disease, aspirin toxicity or CNS dysfunction

Question 34

Metabolic alkalosis

Answer 34

-Abnormal retention of bicarb (loop directics, chronic hypokalaemia)
-Loss of H+ (GOO, chronic nasogastric aspiration

Question 35

What are the causes of metabolic acidosis?

Answer 35

-Impaired tissue perfusion (tx cause, improve circulation)
-Renal failure (tx cause, ? need for bicarb/RRT)
-Hepatic failure (? for transplant)

Question 36

What are the causes of respiratory acidosis?

Answer 36

-Head/spinal injury - ventilation
-Drug overdose: antidote +/- ventilation
-Chest wall deformity/injury - ventilation if indicated, surgery for flail chest/multiple rib #
-Myopathy/peripheral neuropathy - ventilation if indicated
-Pulmonary disease: tx disease, respiratory support and ventilation if indicated
-Massive PE: re-establish perfusion of ventilated lung