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Mechanical Ventilation

85

 

Praveen Khilnani and Rajiv Uttam

 

A 2-year-old girl with fever and cough for the past 4 days was admitted to the hospital with worsening respiratory distress and tachypnea. Her SpO2 on room air was 83%. She was put on oxygen at 12 L/min. In spite of high ßow of oxygen, SpO2 was still 85Ð88%. Chest X-ray showed ßuffy shadows bilaterally. In view of clinical exhaustion, severe hypoxemia, and evidence of respiratory acidosis on blood gas, she was intubated.

Mechanical ventilation is the process of delivery of tidal volume with a set FiO2 at a certain rate by presetting the peak inspiratory pressure (pressure ventilation) or tidal volume (volume ventilation) on the ventilator, with a purpose to remove CO2 from lungs and deliver oxygen to the pulmonary capillaries. This is based on gradient of mean airway pressure in the alveoli resulting from delivery of peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) for the entire duration of the respiratory cycle (inspiratory time and expiratory time).

Step 1: Initial resuscitation

¥Patient is resuscitated and rapid sequence intubation (RSI) is planned within 1 min (Table 85.1 and Fig. 85.1).

¥The main purpose of RSI is to avoid positive-pressure ventilation by bag and mask and prevent gastric inßation in patients at risk of aspiration.

P. Khilnani, M.D., F.C.C.M. (*)

Pediatric Critical Care and Pulmonology, BL Kapur Memorial Hospital, New Delhi, India e-mail: khilnanip@hotmail.com

R. Uttam, M.R.C.P.

Pediatric Critical Care and Pulmonology, Max Superspeciality Hospitals, Patparganj,

Delhi, India

R. Chawla and S. Todi (eds.), ICU Protocols: A stepwise approach,

685

DOI 10.1007/978-81-322-0535-7_85, © Springer India 2012

 

686

P. Khilnani and R. Uttam

 

 

Table 85.1 The eight ÒPÓs of RSI

 

Time

Action

Zero minus 10 min

Preparation

Zero minus 5 min

Preoxygenation

Zero minus 3 min

Pretreatment

Time zero

Paralysis with induction

Zero plus 20Ð30 s

Protection and positioning

Zero plus 45 s

Placement

Zero plus 45 s

Proof

Zero plus 1 min

Postintubation management

Rapid sequence intubation

Objective:to secure the airway rapidly and prevent aspiration of gastric contents

Steps

Preparation

Preoxygenation

Pretreatment

Paralysis with induction

Protection and positioning

Placement with proof

Post intubation management

Paralysis with induction

Rapidly acting induction agent

Midazolam: 0.1–0.5 mg/kg Ketamine: 1–3 mg/kg

Rapidly acting neuromuscular paralyticagent:

Succinylcholine: 1–2 mg/kg

Rocuronium: 1 mg/kg

Preparation

Assess patient: anatomy (short neck, micrognatghia), habitus, injuries

Establish IV

Monitor SpO2

Monitor ECG, BP continuously

Assemble equipment: tube and stylet, test cuff

Choose laryngoscope blade, test light

Protection and positioning Watch for apnea within 20 seconds

Bag mask ventilation

Sellick’s maneuver Cricoid cartilage pressure Helps prevent aspiration

Continue until tube is placed or paralysis worn off

No bagging during RSI after induction

Postintubation management

Secure tube

Recheck vital signs

Heart rate Blood pressure

Postintubation management

Medications

Continued paralysis

Vecuronium: 0.1 mg/kg

Sedation

Benzodiazepines

Opioids

Preoxygenation: Pre oxygenate for full 3 minutes, to wash all the nitrogen out of the lungs and create a reservoir of O2

Pretreatment

Often optional step

Mitigate adverse reactions

Lidocaine(1 mg/kg)

Opioids

Atropine for children

<8 years

Defasciculating dose of paralytics

Placement with proof

Tube placement

Test jaw for flaccidity 45 seconds after succinylcholine

Insert ETT

Sellick’s maneuver discontinued after cuff is

inflated

Confirm tube placement

ETCO2 Breath sounds Chest rise Chest X-ray

Fig. 85.1 Rapid sequence intubation protocol

85 Mechanical Ventilation

687

 

 

¥Bag-and-mask ventilation may be necessary in apneic patients or those with ineffective spontaneous breathing.

¥In such patients, SellickÕs maneuver is performed to prevent air entering into stomach, and gentle AMBU bagging can be done.

Step 2: Initiation and ventilator management

Monitor the status of oxygenation and ventilation and titrate ventilator parameters accordingly (Fig. 85.2).

A.Initial ventilator settings: pressure limited

¥ModeÑpressure control.

¥FiO2Ñstart with 1 and wean down to get good SpO2 (>90%).

¥Optimal positive end-expiratory pressure (PEEP)Ñto achieve adequate alve-

olar recruitment so that saturations are maintained at minimum FiO2 (<0.6) and compliance is best with no hemodynamic compromise.

¥Respiratory rateÑnormal for age (adjust if there is air trapping).

¥Pressure control above PEEP (peak inspiratory pressure [PIP]-PEEP)Ñso that tidal volume equal to 6Ð8 mL/kg is delivered with adequate chest rise.

¥Inspiratory timeÑnormal for age, 0.4 s for neonates, 0.5Ð0.6 s for infants, 0.6Ð0.8 s for toddlers, and 0.9Ð1.0 s for older children (adjust in case of air trapping or severe acute respiratory distress syndrome [ARDS]).

B.Volume limited

¥ModeÑvolume control

¥Tidal volumeÑ6Ð8 mL/kg of ideal body weight, look for adequate chest rise

¥Inspiratory timeÑnormal for age (adjust in case of air trapping or severe ARDS)

¥Optimal PEEPÑadequate alveolar recruitment so that saturations are main-

tained at minimum FiO2 (<0.6) and compliance is best with no hemodynamic compromise

¥Respiratory rateÑnormal for age (adjust if there is air trapping)

¥FiO2Ñto get good SpO2 (>90%)

C.Sedation and analgesia

¥Most patients can be managed with adequate sedation and analgesia without muscle relaxants. Muscle relaxants should never be started without adequate sedation.

¥Midazolam and morphine or fentanyl are used for most of the cases. In case of speciÞc scenarios, other agents can be tried.

¥Morphine is not preferred in hemodynamic instability and wheezing. Ketamine can be used.

¥Midazolam is not preferred in severe hemodynamic instability and liver failure.

¥Ketamine is preferred in shock and wheezing. Ketamine is not used in raised intracranial pressure.

688

P. Khilnani and R. Uttam

 

 

 

 

 

Choose conventional

 

 

 

 

 

 

ventilation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Initiation

 

 

 

 

 

 

Choose mode

 

 

Choose initial settings

 

 

Set trigger sensitivity

 

 

Set alarm limits

 

 

Select sedation and analgesia

 

 

Monitor SpO2, HR, and BP

 

 

ABG (1 hour after starting then

 

 

 

6-hourly after any major change),

 

 

 

Chest xray

 

 

 

 

 

 

 

 

 

 

 

 

 

Troubleshooting

 

 

 

 

 

 

Displacement

 

Respiratory care protocol

 

 

 

 

 

 

 

Obstruction

 

Head end elevation

 

Pneumothorax

 

Position change 2-hourly

 

Equipment failure

 

Suction (in line or otherwise)

 

 

 

 

 

as needed

 

 

 

 

Chest physiotherapy if

 

 

 

 

 

required

 

 

 

 

Increase PEEP increase FiO2

 

 

 

 

• NO IMPROVEMENT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Choose HFOV

 

 

 

 

 

 

Table 85.2

 

 

 

 

 

 

 

 

 

Increase MAP, FiO2 for poor oxygenation

Increase amplitude and decrease frequency for high PaCO2

MAP - 2 Cm H2O above conventional

FiO2 –minimum to keep saturations above 88%

Frequency–according to age ( 10-12 for newborns, 8-10 for small children, 6-8 for big children)

Amplitude and power-for wiggle up to groin or mid thigh

Inspiratory time – 33%, bias flow>25 L/min

Do ABG and CXR one hour after starting and after every major change in settings

Make changes according to SPO2, ABG

Wean FiO2, MAP as condition improves

Switch to conventional when MAP <20, FiO2 0.4

Spontaneous breathing trial

Extubation

Fig. 85.2 Ventilator management protocol

Step 3: Change settings according to arterial blood gas

¥Poor oxygenationÑincrease FiO2, optimize PEEP, increase inspiratory pressure or tidal volume(Vt) if chest rise is not adequate, increase inspiratory time(Ti), and try inverse ratio ventilation if severe ARDS.

85 Mechanical Ventilation

689

 

 

Table 85.2 Indications for high-frequency oscillatory ventilation

Requiring mean airway pressure more than 20

Not maintaining saturations with PEEP more than 14, FiO2 more than 0.6

Oxygenation index more than 16 (oxygenation index = mean airway pressure × FiO2 × 100/PaO2)

Consider early use rather than as a rescue therapy

¥High PaCO2Ñignore if pH is acceptable (>7.2) unless there is increased intracranial pressure or severe pulmonary hypertension (permissive hypercapnia).

¥To decrease PaCO2, increase rate or increase PIP or Vt. In bronchospasm, decrease rate and increase expiratory time to prevent air trapping.

¥High PaO2Ñdecrease FiO2.

¥Low PaCO2Ñdecrease rate and decrease Vt.

Step 4: Weaning

Ventilatory settings are reduced once the primary pathology or condition that led to ventilation is improving. There are no set protocols for weaning. Different protocols are followed by different institutions. Generally, the following pattern is adopted:

¥FiO2 is weaned Þrst to 0.4, maintaining saturation in acceptable range.

¥Mode is changed to Synchronized intermittent mandatory ventilation (SIMV) with pressure support mode or pressure support mode.

¥PEEP is decreased gradually in steps of 2 cm H2O to 4Ð5 cm H2O.

¥SIMV rate is decreased to 5Ð10.

¥The patient is reassessed after each change in the settings, and if the oxygen requirement goes up or the patient develops respiratory distress or is hypercarbic on blood gas, weaning process is paused and the support level is increased.

Some patients (especially when the lung is normal or short ventilation for neuro-

logical indications) can be directly given a spontaneous breathing trial after stopping sedation and extubated without weaning.

Step 5: Spontaneous breathing trial

¥Spontaneous breathing trial is done before extubation to assess extubation readiness. It can be done with a T piece after disconnecting ventilator, endotracheal continuous positive airway pressure (CPAP), or minimal pressure support with CPAP.

¥Usually the pressure support (PS) level is adjusted to the size of endotracheal

tube (ETT) (6 cm H2O PS for ETT >5 mm, 8 cm for ETT 4Ð5 mm, and 10 cm for ETT 3Ð4 mm).

Duration of the trial ranges from 30 min to 2 h. The following are the criteria for

terminating a spontaneous breathing trial.

¥Inability to maintain gas exchange (needing more than 0.5 FiO2 for saturations greater than 95%)

¥Inability to maintain effective ventilation (measured exhaled tidal volume <5 mL/ kg; PaCO2 >50 mmHg or increase >10 mmHg above baseline)

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