Digital PEN stands for:

D – Digits (Fingers and toes)
P – Penis
E – Ear
N – Nose tip

1. Drugs that can be given via endotracheal tube – Mnemonic
2. Individuals at high risk for respiratory complications of anesthesia – Medical mnemonic
3. Components of optimal preparation for securing the airway in anesthesia – Medical mnemonic

SOAP stands for:

S - Suction
O – Oxygen
A – Airway
P – Pharmacology

1. Individuals at high risk for respiratory complications of anesthesia – Medical mnemonic
2. Anaesthetic agents used in day care anesthesia – Medical mnemonic
3. Tools for intubation – Medical mnemonic

COUPLES stands for:

C – COPD
O – Obese
U – Upper abdominal surgery
P – Prolonged bed rest
L – Long surgery
E – Elderly
S – Smokers

1. Risk approach in antenatal care
2. Anaesthetic agents used in day care anesthesia – Medical mnemonic
3. Components of optimal preparation for securing the airway in anesthesia – Medical mnemonic

1. Halothane delivery device
2. Causes of renal papillary necrosis – Medical mnemonic
3. Asherman syndrome – Features – Mnemonic

• Infections of larynx
• Neck mobility abnormalites
• Teeth abnormalties(loose tooth,protuberant tooth)
• Upper airway abnormalties (strictures or swellings)
• Bull neck deformities
• Ankylosing spondylitis
• Trauma/tumour
• Inexperience
• Oedema of upper airway
• Narrowing of lower airway

1. Tools for intubation – Medical mnemonic
2. Differential diagnosis of poor breath sounds after intubation – Mnemonic
3. AIIMS November 2011 – MCQ 63

• Displaced tube
• Obstruction
• Pneumothorax
• Esophageal intubation

1. VINDICATE – Mnemonic for differential diagnosis
2. Vesicular Breath Sounds : Mechanism of formation
3. Differential diagnosis of low set ears – Medical mnemonic

1. ENT – MCQ 18 – Earliest manifestation of carcinoma glottis
2. Differential diagnosis of poor breath sounds after intubation – Mnemonic
3. Anatomy – MCQ 19 – Common carotid artery divides at the level of

Reference:
Hypertension: a companion to Brenner and Rector’s the kidney By Suzanne Oparil, Michael A. Weber

1. Physiology – MCQ 22 – Cardiovascular changes in isometric exercise
2. Anaesthesia – MCQ 10 – Dissociative anaesthesia
3. Heart conditions in which pregnancy is contraindicated

Terminology

PEEP: positive end expiratory pressure

Cycling: change from inspiration to expiration or the reverse. It can be volume cycled, pessure cycled, time cycled or flow cycled.

Modes of ventilation: controlled mode, assist controlled mode, assist mode

Controlled mode – every breath by the ventilator; even if the subject wants breath spontaneously, it is not permitted. Volume and pressure controlled modes are available.

Assist control mode – IMV and SIMV (synchronized intermittent mandatory ventilation). SIMV removes the chance of fighting with the ventilator. It is a popular weaning method. Both these modes are volume cycled.

Assist mode – ventilator only supports patient’s effort. eg. Pressure support ventilation (PSV). This mode is for weaning in a conscious patient. It will be disastrous in those prone for apnea.

While using volume controlled ventilation, peak airway pressure has to be monitored. In pressure controlled ventilation, the tidal volume has to be monitored for adequacy.

Positive end expiratory pressure (PEEP): Begin with 5 cm and step up if necessary. PEEP improves oxygenation by preventing alveolar collapse and recruits lung units. It increases FRC and prevents cyclical collapse of alveoli. PEEP can reduce cardiac output and overdistension of normal units.

Sedation / muscle relaxation for IPPV

Sedation is necessary for the person to tolerate ventilation. Midozolam or propofol are preferred. Instead of bolus doses, infusions may be better. Muscle relaxants are seldom used now-a-days in the ICU setting as relaxatants have their on problems. Relaxants may be used initially. But good sedation has to be given before giving relaxants.

Ventilator induced lung injury (VILI)

Causes: Barotrauma, Volutrauma, Biotrauma, Shear injury, PEEP, Peak pressure

Ventilator associated pneumonia (VAP) has a mortality of about 30%

Prevention of VILI:

Permissive hypercapnia – accept higher PaCO2 upto 60 mm Hg, limit airway pressue (<35 cms), low tidal volume (6 ml/kg)

Permissive hypoxia - accept lower level of PO2.

Weaning: Graduallly reduce ventilatory support using SIMV or PSV or T piece ventilation.

1. Anaesthesia – MCQ 37 – Weaning from mechanical ventillation
2. Inspiratory decrease in systolic blood pressure and pulse volume – Mechanism
3. Oxygen pressure guage

If the oropharyngeal reflexes are not adequate, an oropharyngeal airway is useful. If oropharyngeal airway is not suitable, a nasopharyngeal airway can be used. Advanced airways are considered if even this is not suitable. Advanced airways are endotracheal tubes, laryngeal marks and combi-tubes.

E-C clamp for holding chin and Ambu bag while giving ventilation. E shape of fingers holding the chin and C shape of fingers holding the mask.

RSI: rapid sequence intubation

Sellick’s maneuver: cricoid pressure during intubation to prevent aspiration of regurgitated stomach content.

Rescue airways: gum elastic bougie, laryngeal mask airway (LMA), combitube. Combitube and LMA are blind intubation devices. In case of combitube, it is immaterial whether it goes into the esophagus or the trachea. If it goes into the esophagus, distal cuff inflation permits air to reach the trachea. If it goes into the trachea, ventilate just like in case of an endotracheal tube.

In trauma cases, cervical spine protection should not be forgotten. One person should stabilise the spine while another person is intubating.

Needle Cricothryotomy is useful in an emergency to secure an airway. High frequency ventilation is used through this airway to buy time for planning a regular tracheostomy.

Confirmation of airway postion

Always confirm the airway position by ausculation, starting from the stomach and then over the chest, during trial ventilation (exclude wrong postion first!). Esophageal detector devices are also useful in checking whether the airway is in the wrong postion.

1. Anaesthesia – MCQ 35 – Laryngeal mask airway
2. Components of optimal preparation for securing the airway in anesthesia – Medical mnemonic
3. Causes of failed intubation – Medical mnemonic

Pasteur point: Critical PO2 below which mitochondrial oxygen transport cannot occur (less than 1 mm Hg).
Global oxygen delivery (oxygen flux): Total amount of oxygen delivered to the tissue.
Oxygen extraction ratio: how much oxygen is extracted at tissue level – normal extraction is about 20-30%. It can increase in situations of oxygen deficit.

Oxygen dissociation curve: Shift to right of the oxygen dissociation curve means oxygen affinity to Hb is decreased so that oxygen delivery to tissue is increased. The opposite occurs in a shift to left of the oxygen dissociation curve.

Hypoventilation: decreases arterial PO2 and increases arterial PCO2.

Ventilation perfusion mismatch: either normally perfused, but poorly ventilated or normally ventilated and poorly perfused.

Right to left shunts: Physiological right to left shunt contributes about 2-3% desaturation. Pathological shunts can occur in lung diseases, inctracardiac shunts and extracardia shunts like patent ductus arterious.

Diffusion impairment: No limitation in normal subjects. Exercise induced diffusion abnormality in patients with lung disease.

Role of oxygen therapy in different types of hypoxia:

Supplemental oxygen is useful in hypoxic hypoxia. Oxygen therapy may be useful in anemic hypoxia along with correction of the abnormality. Supplemental oxygen is useful along with other modalities of treatment in stagnant hypoxia also. But it is not useful in histotoxic hypoxia.

Oxygen therapy systems: Low flow system and high flow systems are available.

Low flow systems: Nasal prongs and catheters, face masks, mask with reservoir bags. Usually they are used to deliver 2-4 litres of O2 per minute. 3-4% of FiO2 increase can be expected with one litre per minute flow rate. Low flow systems are inexpensive and easy to use.
Face masks can supply FiO2 of 0.4 – 0.6. Addition of reservoir to face mask increases reservoir capacity to 750 – 1250 ml and increases the FiO2 levels to 0.6 – 0.8. Partial rebreathing and non-rebreathing masks are also available, depending on the type of valves. In non-rebreathing mask, if the bag collapses completely during inspiration, the oxygen flow rate is inadequate.

High flow systems (Venturi device)
Delivers constant FiO2. There is colour coding of masks for the FiO2 achievable and the oxygen flow rate recommended.

Monitoring oxygen therapy

Patient clinical status – symptomatic improvement
Measurement of ABG and SPO2

Oxygen therapy in special situations

COPD: Hypercapnia is a problem which can occur due to loss of hypoxic drive for ventilation. Never withold oxygen therapy for fear of abolishing hypoxic drive.

Oxygen toxicity

Can occur with 100% oxygen for 12 hrs, 80% oxygen for 24 hrs or 60% oxygen for 36 hrs.
All these are in those with normal lung – can occur with lower levels in those with lung disease. A safe level for those with normal lung is 50%. If there is no response with these safe levels, addition of other modalities like CPAP have to be considered.
Home oxygen therapy devices:

Compressed cylinders, oxygen concentrator and liquid oxygen cylinders are the devices available for home oxygen therapy.

Indication for long term oxygen therapy: Hypoxemia at rest (PaO2 less than 55 mm Hg), borderline hypoxemia or hypoxemia with exercise.

1. Nitrous oxide and oxygen flow meters
2. Anaesthesia – MCQ 4 – Side effects of oxygen therapy
3. Oxygen pressure guage

Double lumen endotracheal tube

1. Drugs that can be given via endotracheal tube – Mnemonic
2. Halothane delivery device
3. Destruction of 2nd rib

Oxygen pressure guage

Oxygen pressure guage attached to a Boyle’s machine for general anaesthesia.

1. Nitrous oxide pressure guage
2. Boyle’s machine
3. Halothane delivery device

Nitrous oxide pressure guage

Nitrous oxide pressure guage attached to a Boyle’s machine for general anaesthesia.

1. Oxygen pressure guage
2. Boyle’s machine
3. Nitrous oxide and oxygen flow meters

Isoflurane delivery device

1. Halothane delivery device
2. Boyle’s machine
3. Oxygen pressure guage

Halothane delivery device

Halothane delivery device used for delivering metered dose of halothane for general anaesthesia. The device can be attached on the Boyle’s machine and halothane vapour delivered along with oxygen through the endotracheal tube. Halothane is an inhalational anaesthetic agent like nitrous oxide and isoflurane.

1. Isoflurane delivery device
2. Boyle’s machine
3. Nitrous oxide and oxygen flow meters

Boyle's machine

Boyle’s machine used for delivering oxygen and anaesthetic gases for general anaesthesia. Flow meters for nitrous oxide and oxygen as well as delivery device for isoflurane are seen attached to the top bar. Pressure guages for nitrous oxide with blue screens are seen on the left side and those for oxygen with white screens are seen on the right side.

1. Nitrous oxide pressure guage
2. Nitrous oxide and oxygen flow meters
3. Oxygen pressure guage

Nitrous oxide and oxygen flow meters

Nitrous oxide and oxygen flow meters as part of a Boyle’s apparatus used for anaesthesia. The position of the float in the graduated tubing goes up as the flow increases.

1. Nitrous oxide pressure guage
2. Boyle’s machine
3. Oxygen pressure guage