Respiratory Flashcards
Label picture 27 (9)
See picture 28
Name 5 causes hypoxemia (low pa02)
• low fio2
• hypoventilation
•decreased DLCO (diffusing capacity of lungs for Carbon monoxide) - ability to assess lungs’ ability to transfer gas to blood. Damage to alveolar-capillary interface.
• shunt ( po2 (A -a) > 15)
. VQ mismatch ( part of lung receive oxygen but no blood flow or other way around) (deadspace ventilation and intrapulmonary shunting)
Normal Pa02?
80-100 mmHg
(The amount of O2 in blood available to bind with Hb)
Define mild hypoxia value
Pa02 60-80 mm Hg
Define moderate hypoxia value using paO2
Pa02 40-60 mmHg
Define severe hypoxaemia value
<40 mmHg PaO2
What is physiological peep?
2-3 cm H2O
Result of too much peep?
Dead space ventilation
Name 4 causes haemoglobin oxygen dissociation curve to left
Increased affinity for oxygen
• hypothermia
• decrease pco2
• decrease 2,3 DPG (facilitate oxygen release)
• decrease hydrogen (increase ph)
Name 4 causes haemoglobin oxygen dissociation curve to right
Decreased affinity
• hyperthermia
Increase pco2
• increase 2,3 DPG
• increase hydrogen (decrease PH)
How much fio2 given intra-op?
At least 30%
How does general anaesthesia affect shunt fraction?
Increase by 5%
Lung compliance formula?
Change in volume ( l) ÷ change in pressure (cm)
Minute ventilation (mv) formula?
TV X rr
Which 3 factors are important in considering pa02?
• Fi02
• Pbarometric
• age
Identify pathology picture 29
Obstructive lung disease atelectatic
Simple formula for pa02?
102 - age/3
Identify pathology picture 30
Obstructive lung disease
Identify pathology picture 31
Bronchiectatic obstructive lung disease
Differences in static lung volumes in obstructive lung disease? (3)
• Larger FRC functional residual capacity
• increase tlC total lung capacity
• increase rv residual volume significant!
Diagnosis obstructive lung disease? (2)
FEV1: FvC <70% predicted and not reversible with bronchodilators
FEF 25-75% (forced expiratory flow )
Identify pathology picture 32
Graph 1: normal
2: obstructive
3: restrictive
Identify pathology picture 33
Restrictive lung disease
Identify pathology picture 34
Restrictive lung disease
Name changes of static lung volumes in restrictive lung disease (3)
• Decreased TLC (total lung capacity)
• decreased FRC
Also decrease FEV1 and FvC severely
Tidal volume distribution formula in normal awake breathing?
2 4 6 rule
Vtidal (6 ml/kg) = Valveolar (4ml/kg) + Vdeadspace (2ml/kg)
33 % therefore don’t reach alveoli
Tidal volume distribution formula in anaesthetised ventilated patient?
Rule of 3 3 6
Vt (6ml/kg) = Va (3) + Vd (3)
Therefore 50% doesn’t reach alveoli.
How is problem of only 50% gases reaching alveoli in anaethetised intubated patient solved? (4)
Give initial Vt of 8-9ml/kg (instead of normal 6)
Cautiously adjust to need of patient according to
• underlying lung disease
• airway pressure
• EtCO2
Describe the different degrees of postoperative lung restrictions in upper abdominal, lower abdominal and thoracic, and other anatomical sites
•Upper abdominal surgery non-laparascopic: most profound restrictive defect post-op, 40-50% decrease FRC
• lower abdominal or thoracic surgery: 30% decrease FRC
• other operative sites eg ENT, intracranial: 15-20% decrease FRC
Name 4 complications of decrease in FRC post op (atelectasis)
• Shunt
• hypoxaemia
• pulmonary infection
• Respiratory failure
Pre-op management and anaesthetic implications of recent URTI in obstructive lung disease?
• Attempt to reduce secretions pre-op
• limit manipulation of potentially hyperresponsive airway
-Regional preferred to general anaesthesia
- if general, use SGA rather than ETT
Treatment of intra-op bronchospasm? (6)
- Call for help
- Stop offending agent/stimulus eg ET tube
- 100 % oxygen and deepen anaesthesia with volatiles (potent bronchodilators), sedation or combination
- Administer beta 2 (salbutamol inhalation/IV) (will decrease BP) or alpha 2 agonist
5 IV epinephrine in doses of 10 mcg/kg - IV corticosteroids for later when need to extubate
Ketamine may also be considered, good bronchodilator. Also MgSO4
Most effective treatment aspiration pneumonitis?
Supplemental oxygen and ventilator support including peep
Tidal volume given to patients with obstructive lung disease?
10-12 ml/kg
(Normal 6-8)
Tidal volume given to patients with restrictive lung disease?
6-8 ml/kg (normal)
Ventilation rate given to patients with obstructive lung disease?
8-10 bpm
(Normal =12)
Ventilation rate given to patients with restrictive lung disease?
16-20 bpm
(Normal 12)
I:E given to patients with obstructive lung disease?
1:3
(Normal 1:2)
I:E given to patients with restrictive lung disease?
1:1,5 to 1:1
(Normal 1:2)
Peak inspiritory pressure given to patients with obstructive lung disease?
Low as possible <30 cm H2O (normal)
Peak inspiritory pressure given to patients with restrictive lung disease?
Low as possible <35 cm H2O
Normal <30
Plateau inspiritory pressure given to patients with obstructive lung disease?
Low as possible <25 cm H2O (normal)
Plateau inspiritory pressure given to patients with restrictive lung disease?
Low as possible <30 cm H2O
(Normal < 25)
Hbsa02 given to patients with obstructive lung disease?
> 80-90%
(Normal 92-98%)
Hbsa02 given to patients with restrictive lung disease?
> 88-90 %
(Normal 92-98 %)
PaCO2 given to patients with restrictive and obstructive lung disease?
> 39 mmHg
(Normal 31-39)
Name 4 risk factors hypercarbia
• Co2 retention pre-op
• high dose opioids
• airway obstruction
• inadequate muscle relaxant reversal
Name 5 signs bronchospasm
• increased peak airway pressures (normal plateau inspiratory pressure)
• wheezing
• increased expiratory time (causes shark fin appearance on capnogram , and may even cause pneumothorax due to auto-peep activation on machine)
• increased end tidal co2 with upsloping et c02 waveform (shark fin capno)
• decreased tidal volumes if pressure contro)
How should an asthma patient be anaesthetised? (7)
• Regional anaesthesia best so can maintain own airway
. If Ga necessary, use supraglottic airway device if no risk aspiration
• if intubation required: deep plane anaesthesia.
• induction: propofol/etomidate (thiopentone contraindicated, release histamine)
• analgesia: synthetic opioids eg tramadol, fentanyl ; ketamine (morphine contraindicated)
• muscle relaxant: vecuronium/cis-atracurium (atracurium, mivacurium, roc release histamine in high doses)
• volatiles safe to maintain (bronchodilators)
• use drugs that promote bronchodilatation: inhalation, ketamine, mgs04
Name 5 at risk groups for laryngospasm
•Children
• airway surgery
• thyroid surgery: recurrent laryngeal nerve injury
• parathyroid surgery: recurrent laryngeal nerve injury, hypocalcaemia ( cause stridor)
• patients not completely awake (MAC 0,7-03)
How does laryngospasm present (2)
• Stridor
. See saw movement of chest and abdo - trying to breathe against closed vocal cords
What is normal p/f ratio?
(Pa02/fi02)
>300
What is acute lung injury p/f ratio?
200-299
Go to high care
What is ARDS p/f ratio?
<200
Go to ICU and keep intubated and ventilated
Name the ventilator settings used for COPD patients (6)
• Mode: volume control (more control for physiological parameters)
• tidal volume: 8 ml/kg (higher than normal 6 - hyperinflation, low compliance)
• Respiratory rate: 10 (lower than normal 12 - slow rate = increased expiration time)
• i:e: 1:3 (higher than normal 1:2- increased expiration time so lungs can empty)
• fi 02 : lower. sats 88-92%, pre-op blood gas (hypoxia drive needed to breathe, high oxygen =decreased spontaneous breaths)
• PEEP: 0. (Auto-peep due to air trapping)
Name 4 types hypoxia according to delivery of oxygen formula
1 stagnation hypoxia (cardiac output deranged) - cardiac failure, valvular disease, pericarditis. Treat cause.
2. Anemic hypoxia (hb) - treatment is transfusion, if hb < 3 it’s inadequate to maintain supply to match vo2
3. Hypoxic hypoxia (Sats) - any path interfering with gas exchange (shunt / ventricular septal defect). treat by increase oxygen, cpap, intubate and ventilate
4 toxic hypoxia (1,34 binding capacity of hb) - Co poisoning eg, treat with exchange transfusion (depend on poison)
Define functional residual capacity
Residual volume plus expiratory reserve volume
Ventilator settings for restrictive lung disease? (4)
• Tidal volume 6-8 ml /kg
• Respiratory rate high. 16
• aim for saturations > 88-90%
• i:e low 1:1
Nb name 10 causes increase peak inspiratory pressure
If high difference (>5cm h20) between peak and plateau pressures (high peak, low plateau): increased restrictive work
• bronchospasm
• anaphylaxis
• endotracheal tube obstruction
• ventilator circuit obstruction eg ventilator tubing kinked
If low difference (high peak and plateau): acute decrease lung compliance, increased elastic work
• pneumothorax
• tension pneumothorax
• evolving pneumonia
• pulmonary oedema
• ARDS
• auto-peep caused by “breath stacking”