Chapter 12 Resuscitation in special circumstances Flashcards
(136 cards)
1
Q
In acidosis, does serum potassium increase or decreases?
A
Increase as H+ ions are shifted intracellularly in exchange for K+
2
Q
At what level is hyperkalaemia considered severe?
A
> 6.5 mmol/L
3
Q
What drugs can cause hyperkalaemia?
A
ACE-I Angiotensin II receptor antagonist Potassium sparing diuretics (spironolactone) NSAIDs Beta-blockers Trimethoprim
4
Q
What endocrine condition can cause hyperkalaemia?
A
Addison’s disease (adrenal insufficiency)
5
Q
In what conditions/diseases is potassium release from tissues of the body?
A
Rhabdomyolysis
Tumour lysis
Haemolysis
Burns
6
Q
What are symptoms of hyperkalaemia?
A
Weakness
Flaccid paralysis
Paraesthesias
Depressed deep tendon reflexes
7
Q
What ECG changes are seen in hyperkalaemia?
A
Tall, peaked T waves (T wave larger than R wave in more than one lead) Shortening of QT interval 1st degree heart block Bradycardia ST segment depression Flattened or absent p waves Widened QRS S and T wave merging (sine wave pattern) Ventricular tachycardia Cardiac arrest (PEA, VF/ VT, asystole)
8
Q
When treating a patient for hyperkalaemia with an insulin infusion, how long after the infusion stops is the patient at risk of hypoglycaemia?
A
Usually 3 hours but can be up to 6 hours
9
Q
What medication should you give along with resonium A to avoid complications of this medication?
A
Laxative
10
Q
Does a K+ level of 5.5 to 5.9 mmol/L need treatment?
A
Usually not.
Address underlying cause of hyperkalaemia (drugs/diet) and avoid further rise.
If it does need to be treated, give:
Resonium A 15 -30g orally or a retention enema, onset < 4 hours.
Consider IV fluids
11
Q
Does K+ level 6.0 to 6.4mmol/L need treatment?
A
Yes Shift intracellularly with: 10 units novorapid 25 g glucose (50ml 50% glucose) IV over 15 - 30 minutes Duration of action 4 - 6 hours Remove potassium from the body (resonium, dialysis)
12
Q
What dose of nebulised salbutamol would you give for hyperkalaemia? How long will it last?
A
10 - 20 mg nebulised. Onset 15 minutes, duration 4 - 6 hours
13
Q
What dose of insulin and glucose will you give for hyperkalaemia? How long does it last?
A
10 units novorapid, 50ml 50% glucose (25g) over 30 minutes
Onset 15 - 30 minutes, duration 4 -6 hours
14
Q
If the patient is acidotic and has hyperkalaemia, what treatment could you consider?
A
50ml 8.4% sodium bicarbonate = 50mmol
15
Q
How many mmol of calcium in 10ml of 10% calcium chloride and 10ml 10% calcium gluconate
A
Calcium chloride = 6.8mmol
Calcium gluconate = 2.2 mmol
16
Q
What steps do you take when a patient arrest DURING haemodialysis?
A
1) Assign a nurse to dialysis machine
2) STOP ultrafiltation (fluid removal)
3) Give a fluid bolus
4) Return patients blood
5) Disconnect from dialysis machine (most machines recommend this before giving any shocks)
6) Leave dialysis access open and use for drug administration
7) Now treat as you would for all patients, however most likely cause is hyperkalaemia/VT/VF
17
Q
At what level is hypokalaemia severe?
A
< 2.5mmol/L
18
Q
What are the possible causes of hypokalaemia?
A
GIT: diarrhoea Drugs: diuretics, laxatives, steroids Renal losses: renal tubular disorders, diabetic insipidus, dialysis Endoncrine: cushings syndrome, hyperaldosteronsim Metabolic alkalosis Magnesium depletion Poor dietary intake Treatment of hyperkalaemia
19
Q
What are the signs and symptoms of hypokalaemia?
A
Nerves and muscles affected: Fatigue Weakness Leg cramps Constipation If severe (< 2.5mmol/L): rhabdomyolysis, ascending paralysis, respiratory difficulties
20
Q
What are the ECG features of hypokalaemia?
A
U waves T wave flattening ST segment changes Arrhythmias (including AF, especially if patient is on digoxin) Cardiac arrest (VF/pVT, PEA, asystole)
21
Q
What is the maximum IV dose of K+ and the fastest rate you can give it for an unstable arrhythmia when cardiac arrest is imminent?
A
20 mmol over 10 minutes = 2 mmol/min
followed by 10mmol magnesium
22
Q
What is the maximum recommended rate of K+ replacement IV ?
critically low K+ but stable
A
20 mmol/hour
23
Q
What dose of K+ do you give for a cardiac arrest due to hypokalaemia?
A
5mmol bolus followed by 10mmol magnesium
24
Q
What monitoring is needed when giving IV potassium?
A
Telemetry
25
What are the causes of hypercalaemia? (Ca2+ > 2.6mmol/L)
Primary or tertiary hypeparathyroidism
Malignancy
Sarcoidosis
Drugs
26
How does hypercalcaemia present?
```
Confusion
Weakness
Abdominal pain
Arrhythmias
Cardiac arrest
```
27
What are the ECG features of hypercalcaemia?
```
Short QT interval
Prolonged QRS
Flat T waves
AV block
Cardiac arrest
```
28
What is the treatment of hypercalcaemia?
```
IV fluid replacement
Frusemide 40mg IV
Hydrocortisone 200mg IV
Pamidronate 30 - 90mg IV
Treat underlying cause
```
29
What are the causes of hypocalcaemia? ( <2.1 mmol/L)
```
Chronic renal failure
Acute pancreatitis
Calcium channel blocker overdose
Toxic shock syndrome
Rhabdomyolysis
Tumour lysis syndrome
```
30
What are the symptoms of hypocalcaemia?
```
Paraesthesias
Tetany
Seizures
AV block
Cardiac arrest
```
31
What are the ECG features of hypocalcaemia?
Prolongs QT interval
T wave inversion
Heart block
Cardiac arrest
32
What are the causes of hypermagnaemia?
Renal failure
| Iatrogenic
33
What are the symptoms of hypermagnaesaemia?
```
Confusion
Weakness
Respiratory distress
AV block
Cardiac arrest
```
34
What are the ECG findings of hypermagnaesaemia?
Prolonged PR and QT interval
T wave peaking
AV block
Cardiac arrest
35
How do you treat hypermagnaesaemia?
Consider if > 1.75 and symptomatic
Calcium chloride 10% 5 - 10ml IV repeated as necessary
Saline diuresis: normal saline + frusemide
IV haemodialysis if ventilatory support needed
36
What are the cause of hypomagnasaemia?
```
GI losses
Polyuria
Starvation
Alcoholism
Malabsorption
```
37
What are the symptoms of hypomagnasaemia?
```
Tremor
Ataxia
Nystagmus
Seizures
Arrhythmias - torsades de pointes
Cardiac arrest
```
38
What are the ECG findings of hypomagnesaemia?
```
Prolonged PR and QT interval
ST segment depression
T wave inversion
Flattened p waves
Increased QRS duration
Torsades de pointes
```
39
How much and how quickly can you replace magnesium in unstable patient (torsades de pointes, seizures)
2g or 10 mmol over 10 minutes
40
When a patient has progressed to septic shock ( lactate > 4 mmol/L or hypotension unresponsive to fluids), what is the mortality rate?
50%
41
Is there much evidence supporting improved clinical outcomes when activated charcoal is used for overdoses?
No, but may still be beneficial in large overdoses.
| Use up to 2 hours post overdose, effectiveness decreases over time
42
What is the dose of intralipid for local anaesthetic overdose?
20% intralipid 1.5ml/kg as bolus (=100ml in 70kg adult)
bolus can be repeated 1-2 times in cardiac arrest at 5 min intervals
then, 0.25ml/kg/min for 30 - 60 minutes (about 600ml over 30 minutes in 70kg adult)
Can double infusion rate if BP declines
43
What routes can naloxone be given?
Intranasal, subcut, IM, IV
dose range 100mcg up to 800mcg
Duration of action 45 - 70 minutes
44
What is the risk of rapid reversal of opioids in a patient who is opioid dependent?
Acute withdrawal syndrome, sympathetic surger:
Behavioural disturbance/severe agitation
Acute pulmonary oedema
Ventricular arrhythmia
45
What is the risk of giving flumazenil to a patient that is dependent on benzodiazapines, epileptic, or co-ingestion with tricyclic antidepressent?
Withdrawal syndrome
Seizure
Arrhythmias
Hypotension
46
Would you give naloxine or flumazenil to a patient suspected over overdose who has has a cardiac arrest?
No, just follow usual protocol
47
What pH would you try to target/stop giving sodium bicarbonate in a TCA overdose?
pH 7.44 to 7.55
| Increases protein binding and increases sodium load
48
What dose of atropine would you give for organophosphate, carbamate or nerve agent poisoning?
Large dose 2-4mg bolus IV
49
In anaphylaxis, what % of patients may not exhibit a skin reaction?
10 - 20%
50
Why is adrenaline so well suited for treating anaphylaxis?
Alpha receptor agonist: treats vasodilation
Beta 1 agonist: increased myocardial contractility
Beta 2 agonist: treats broncospasm
Suppressed histamine and leukotriene release
51
How many IM doses of 0.5mg 1:1000 adrenaline do you give before giving IV infusion?
2 or 3 (ideally rotate sites)
52
A patient has anaphylaxis treated with IM adrenaline but has ongoing
a) Stidor
b) Wheeze
How would you treat a) compared to b) ?
a) nebulised adrenaline (5ml of 1:1000)
| b) nebulised salbutamol
53
How common are biphasic reactions in anaphyalxis?
3 - 20%
| Monitor for 4 hours post LAST dose of adrenaline
54
What dose of corticosteroid do you give for anaphylaxis?
prednisone 50mg PO
| hydrocoritsone 200mg IV
55
What can be measured to help diagnose anaphyalxis if the diagnosis is unclear?
Mast cell trypase, which is released during mast cell degranuation and is markedly elevated in anaphylaxis. Use serum tuble
Minimum: one sample 1-2 hours post start of symptoms
Ideally three times samples
1st as soon as possible
2nd 1-2 hours post onsent
3rd at 24 hour of convalesence (provides baseline tryptase)
56
Name 3 causes of cardiac arrest in pregnant women?
```
Cardiac disease ( congenital and acquired)
Pulmonary embolism
Psychiatric disorders (depression, suicide)
Hypertensive disorders of pregnancy
Sepsis
Haemorrhage
Amniotic fluid embolism
Ectopic pregnancy
```
Also consider other cause of arrest in a young person
(anaphylaxis, drug overdose, trauma)
57
What is an alternative to using the left lateral position in a pregnant women in distress?
Manually displace the uterus to the left
58
Name three doctors you would call to assist with resuscitation of a pregnant woman?
Anaesthetist
Obstetrician
Neonatologist/paediatrician
59
At how many weeks gestation does the gravid uterus start to push down on the IVC (and potentially) limit the effectiveness of CPR?
20 weeks
60
Can you use a pillow or wedge instead of a full length tiling table (operating table) for a pregnant patient needing CPR?
No. Use left lateral displacement of the uterus instead
61
A pregnant unconscious patient is more likely to have a pulmonary aspiration event, what can you do to reduce the risk?
Early intubuation
62
For a pregnant patient with massive haemoarrhage what fluid/drugs would you use to control bleeding?
Massive transfusion protocol
1g tranexamic acid then infusion
If post partum: uterine massage, oxytocin, ergotamine, prostaglandins
63
There is ongoing bleeding, you suspect from the uterus in pregnant patient. What specialties can help control the bleeding?
Interventional radiology
| Surgeons/gynaecologist
64
A pregnant woman with eclampsia was being treated with magnesium then has a cardiac arrest. You suspect magnesium toxicity. What is the antidote?
8.4mmol (10ml) calcium chloride
65
What are the signs of an amniotic fluid embolism?
```
sudden:
cardiovascular collapse
breathlessness
cyanosis
arrhythmias
hypotension
haemorrhage associated with DIC
```
66
What is the treatment for amniotic fluid embolisation ?
Supportive and correction of coagulopthy
67
For best survival rates of infants delivered by a peri-mortal caesarean section, how quickly should they be delivered from the collapsed mother?
5 minutes after CPR has begun
68
Would you consider a peri-mortem in a patient < 20 weeks gestation?
No. Gravid uterus at this stage is unlikely to compromise maternal output and foetal viability is not an issue
69
Would you consider a peri-mortem caesarean section of a patient 20 - 23 weeks gestion?
Yes but only to assist the mother, infant survival is unlikely.
70
Are there good outcome for prolonged CPR in the setting of trauma?
No.
| Stop after 20 minutes
71
Is CPR effective in the setting of a tension pneumothorax, tamponade or hypovolaemia/haemorrhage?
No. Continue CPR but priorities treating these reversible causes (some will say prioritise over CPR)
72
A patient has been involved in a major trauma and the patient is bleeding, you can not feel a radial pulse. You don't have blood available. What volume of fluid do you give and to what endpoint?
250ml bolus normal saline until radial pulse palpable or systolic BP of 80 - 90mmHg (or 100 -100mmHg in TBI or spinal injury)
73
Why is needle aspiration of tamponade in the setting of trauma unlikely to be successful?
It is likely a haemopericardium and the clotted blood cannot be aspirated readily. Need to do a thoracotomy
74
When would you consider a resuscitative thoractomy?
```
Penetrating torso trauma
< 15 minutes CPR
OR
Blunt torso trauma
< 10 min pre-hospital CPR
```
Ideally seen to be alive or have ECG activity before the arrest
75
A patient has a sudden drop off of their end-tidal CO2 and pulse oximeter stops reading but telemetry shows a sinus rhythm.
Should you:
a) check a BP
b) check a pulse ?
Check the pulse. Coud be a PEA arrest
76
Name some causes of sudden and unexpected cardiac arrest in theater?
A - loss of airway
B - undiganosed tension pneumothorax
C - catastrophic haemorrahge (may be confinded into cavitiy chest or abdomen)
D - cardiovascular collase (anaphylaxis from NM blocker, hypovolaemia, vagal stimulation)
77
A patient has arrested in theater, they have and IVC. Would you give the full 1mg adrealine dose IV? If not, what dose and why?
No, give 50 to 100mcg IV adrenaline and titrate up to 1mg if no response
Monitored arrest, you have get a rapid response, 1mg IV is a LARGE dose and could do harm if you had only brief CPR with quick ROSC
78
A patient developed anaphylaxis after rocuronium was given. They have an IVC. Do you give IM or IV adrenaline. What dose?
IV 50mcg boluses to response. If repeated dose needed change to adrenaline infusion
79
What are the reasons for considering urgent resternotomy in post-op cardiothoracic patients?
Chest compression are ineffctive in the setting of cardiac tamponade and hypovolaemia (common causes for arrest).
It may also cause sternal disruption and cardiac damage
Pt should have arterial line in-situ, you should be able to acheive BP > 60/25 with CPR, if not, it's a sign you NEED to reopen.
80
What is the rate of cardiac arrest following cardiac surgery?
0.7 to 8%
81
What are the caues of cardiac arrest in post-op cardiac surgery patients?
```
Cardiac tamponade
Myocardial ischaemia
Pacing failure
Hypovolaemia
Tension pneumothorax
```
82
During an arrest post cardiac surgery, what dose of IV adrenaline would you consider giving opposed to the full 1mg?
100mcg boluses
83
What is the emergency setting for a patient with failed pacing due to external pacing wires?
VOO
HR = 100
Amplitude: maximum
Asynchronous pacing
84
How many shocks would you provide to a post cardiac surgery patient in VF before resternotomy?
3 shocks for VT/VF then reopen
85
What is the time-frame for resternotomy in a cardiac arres patient post cardiac surgery?
5 minute. Use this to quickly treat anything resversible then reopen
86
Are submersions of less 10 minutes associated with a good outcome?
Yes
87
During an episod of immersion (head above water body in cold water) the blood can be shunted away from peripheries , rising BP. What does this result in as a compensatory measure?
Diuresis
Natriueresis
Kaliuresis
Patient is often hypovolaemia on rescue and can arrest on removal from water.
Keep them lying down. Provide fluids
88
Why might a supraglottic airway be ineffective in a drowned patient?
High airway pressure due to aspirated water and gastric contents
89
In a drowned patinet who is spontaneously breathing but needing NIV. How much PEEP would you use?
5 - 10mmHg - lung is full of water
| Decompress stomach with NG
90
Why are IV fluids essential during CPR on a drowned patient?
They are hypovolaemia from cessation of hydrostatic pressure of water on body + cold environment promotes diuresis
91
How long should you do CPR on a drowned patient?
Poor outcomes associated if victim submerged more than 25 minutes
OR
CPR ongoing > 30 minutes
Increased surivical if icy cold water + child patient but still unlikely to have good outcome if CPR > 30 min
92
Are antibiotics beneficial in a drowned patient?
Pneumonia is common but prophylactic antibiotics have not been prove to be of benefit but should be considered if drowned in contaminated water (sewage)
93
What temperatures correspond with the following:
Mild hypothermia
Moderate hypothermia
Severe hypothermia
Mild 32 - 35 C
Moderate 28 - 32 C
Severe < 28 C
94
How cold is too cold to resuscitate?
< 13.7 degree core temperature there has been irreversible damage
95
What sort of thermometer do you need for moderate to severe hypothermic patients?
low reading core thermometer
96
In a hypothermic patient, when continuous CPR is not possible (sole rescuer), what is an alternative?
5 min CPR 5 min break and alternate this way
97
True or false:
Avalanche victims are not likely to survive when they are:
Buried > 60 min (or core temp < 30 C) and in cardiac arrest with an obstructed airway on exctrication
Buried and in cardiac arrest on extrication with an initial potassium of > 8mmol/L
True
98
How can an USS assist you in advanced life support in the hypothermic patient?
To assess for cardiac output
| Peripherial pulses may be hard to assess
99
Drug metabolism is slow leading to potentailly toxic plasma levels of any drugs given during CPR of a hypothermic patient. They are also quiet inefficient.
At what temperature may you consider holding of drug delivery until patient has been warmed?
Consider witholding until > 30 degrees
| Between 30 - 35 degree double time between giving drugs
100
Does bradycardia (including slow AF) and VF need treatment in severe hypothermia (< 28 degrees)
No
Bradycardia is physiological, do not pace or treat unles persisting when > 28 degrees
VF also resolves on rewarming, cardioversion and amiodarone are ineffective until patient is > 28degrees
101
What is the definition of heat stroke?
Systemic inflammatory reponse with core temp > 40.6 accompanied by mental state changes and varying levels of organ dysfunction
Mortality 10 - 50%
102
What is the clinical presentation of heat stroke?
```
Can appear similar to septic shock:
temp > 40 C
Hot dry skin (sweating in 50%)
Extreme fatigue, headache, fainting, facial flushing, vomiting, diarrhoea
Cardiovascular dysfunction: arrhythmias, hypotension
Respiratory dysfunction including ARDS
CNS dysfunctin: seizures, coma
Liver and renal failure
Coagulopathy
Rhabdomyolysis
```
103
A patient is hyperthermic, other than sepsis, what are some other causes?
```
Heat stroke
Drug toxicity
Drug withdrawal
Serotonin syndrome
Neuroleptic malignant syndrome
Endocrine disorder (thyroid storm, phaeochromocytoma)
```
104
Is the prognosis of cardiac arrest in a hyperthermic patient better or worse than a normothermic patient?
Worse
| Risk of unfavourable neurological outcome increase for ever degree > 37
105
Is dantrolene useful in environemntal or exertional heat stroke?
No
106
What is malignant hyperthermia and what is the treatment?
Life-threatening genetic sensitivity of skeletal muscle to voltile anaesthetics and depolarising neuromuscular blocking drugs. Occuring during or after anaesthesia.
Ecstacy and amephatmine can cause a similar condition.
Treat with dantrolene
107
Name the ways an eletrical shock and can damage or dysfunction to the heart
Aysytole (primary) or secondary to asphyxia following respiratory arrest
Current precipitates VF if it passes myocardium during vulnerable period (similar to R on T phenomena)
Myocardial ischaemia from coronary spasm
Myocardial necrosis due to massive catecholamine release
108
What are special consideration in provided initial support to a surivor of an eletrical shock?
Ensure you are safe to apraoch/touch patient first
Secure airway early (before swelling)
Muscle paralysis may be ongoing for hours
Consider blunt force trauma C-spine + other injuries
Remove smoldering clothing
Tissue damage may be much worse than what is visible (electricity follow neurovascular bundles)
Give IVFs and monitor urine output to guide
109
Other than snakes, what animals in Australia can cause paralysis and respiratory arrest?
Jellyfish
Tick
Octopus
109
Other than snakes, what animals in Australia can cause paralysis and respiratory arrest?
Jellyfish
Tick
Octopus
110
True or false: the risk of anaphylaxis after a snake bite can be more lifethreatening thant he toxin itself
true
111
How long does it take for signs and symptoms of envenomation to occur?
In children can be minutes, but can be up to hours in adults and depending in amount of envenomation
112
A snakebite may be painless and not noticed. What are early signs of a snake envenomation?
```
Headache
Nausea, vomiting
Collapse
Confusion
Blurred vision
Abdominal pain
Drooping eyelids
Difficulty speaking, swallowing, breathing
Swollen tender glands in grion or axilla or bitten limb
Weakness, paralysis
Respiratory arrest
```
113
Snake envenomation can be very painful due to muscle spasms. Why are narcotics usually contraindicated?
Patient may develop diaphragmatic parlysis, exaccerbated by opioids
114
What can you do to as an alternative to pressure and immobisation to treat a snake bite if you have no dressing and splints?
Wrap bite site to apply pressure with clothing
| Sit still
115
What do you do as an alternative to pressure immobilisation if a snake bite is on a torso or abdomen?
Apply manual pressure
116
What as the signs of envenomation by a funnel web sider and how long does it take?
```
Effect can be from 10 minutes to hours
Pain at bite site
HTN
Tachycardia
Perioral tingling
Profuse sweating
Copious secretions, bronchorrhoea
Altered GCS
Aponea
```
117
How do you provide first aid to a funnel web bite?
Pressure immobisation dressing like a snak bite
118
When do you remove a pressure bandage after a snake or funnel web bite?
When antivenom and resuscitation equiptment is available
119
How do you treat the pain of redback bite?
Ice for 20 min
| Consider antivenoma if able to monitor (if for symptom relief only, caution anaphylaxis)
120
Other than the funnel web, are they any other snake bites that benefit from pressure immobilisation?
No
121
Are the signs and symptoms of a sting from an irikanji jellyfish immediate or delayed?
Delayed
Initial sting it not very painful and may not be noticed.
Then massive catecholamine surge, risk of APO, cardiomyopathy and hypertensive crisis
122
Box jelly fish + irikanji
Blue bottle
Which jellyfish group is treated with vinegar and which with hot water?
Box jelly fish and irikanji is with vinegar. Assume these are the culprit if in or north of Bundaberg
Hot water for Blue bottle (vinegar can worse sting by causing nematocyst discharge
123
Is there an antivenom for blue bottle stings?
Yes
| Magesium 10mmol then 5mmol/h has shown benefit too
124
How do you remove adherent or suspected jellyfish tentacles in a non-tropical area?
Wash with sea water (not fresh as this will worsen)
Do this even if you can't see them as they may still be present so do at scene before removal
Prevent patient from rubbing or scartching
Heat pack provides relief, change every 20 min. If no relief, try hot packs
125
Is there an anti-venom for the blue-ringed octopus or cone shell sting?
No
126
How dangerous is a blue-ring octopus sting? What happens?
Very lethal. Fortunately only envenomates when handled/attacked.
sodium channel blocker causing respiratory paralysis
127
Is a pressure immobilisation bandage helpful in treating a blue-ringed octoput or cone shell sting?
Yes, apply quickly before respiratory paralysis occurs
128
How dangerous is a cone shell sting? what happens?
Very painful, can cause respiratory paralysis
129
Is there an antivenom for a stonefish sting?
yes
130
How do you treat the pain of non-lethal fish stings?
Hot water for 20 minutes, can repeat cycle for 2 hours or 4 times.
131
An obese patient has arrested, CPR is underway, you have SGA in but there is significant leaking. What should you do?
Return to 30:2 or intubate
| Obese patients have higher airway resistance
132
You have an obese patient in VF arrest. The first shock at 200J was unsuccesful, what could you do?
Increase to 360J
133
Obese patients can have difficult pulses to palpate. How else can you check for mechanical capture if you are concerned about PEA?
Auscultate for HS
| Echo
134
In bariatric patients, what are some normal variants in ECGs?
```
Low voltage waveform
Left axis deviation
Flattened infero-lateral T waves
Atrial enlargement
False positive criteria for inferior wall myocardial infarction
```
135
Can you ramp an obese patient getting CPR?
No, it makes chest comperssions less effective
