How do I ventilate normal lung?

Dr Anand.TiwariF.N.B Critical care medicine.

Consultant neuro-intensive careRuby hall clinic

History

2012

1950

When do I ventilate a normal lung?

BrainstemSpinal cordNerve root

Airway

Nerve

Neuromuscular junction

Respiratory muscle

Lung

Pleura

Chest wall

EXTRAPULMONARYComponents

Choosing the interface

Increased vascular

resistance

Decreased venous return

Decreased distensibility

Decreased distensibility

Decreased venous return

Alveoli

Septal displacement

Heart- Lung Interaction Physiology

Volume / Compliance

Flow x Resistance

Pressure=flow x resistance

Alveolar pressure=volume/compliance + PEEP

Airway pressure=Flow x Resistance + volume/compliance + PEEP

Flow=volume/time

B (P A LV)A (P AW)

Physics of Positive pressure ventilation

3 key ventilator phase variables

When the breath is delivered What limits gas delivery what end the gas delivery

Trigger

Limit

cycle

Assisted Mode(Volume-Targeted Ventilation)

Assisted Mode(Volume-Targeted Ventilation)

Time (sec)Time (sec)

Flow(L/m)

Pressure(cm H2O)

Volume(mL)

Preset VT

Volume Cycling

Patient triggered, Flow limited, Volume cycled Ventilation

Assisted Mode (Pressure-Targeted Ventilation)

Assisted Mode (Pressure-Targeted Ventilation)

Pressure

Flow

Volume

(L/min)

(cm H2O)

(ml)

Set PC level

Time (sec)Time (sec)

Time-Cycled

Patient Triggered, Pressure Limited, Time Cycled Ventilation

SIMV +PS

Pressure support

Physiological PEEP

Case scenario!!

• 25 yr old female admitted with history of BZD and antidepressant,no past medical history in. Registrar calls you in evening 7p.m patient is unwell gurgling sounds, mild airway obstruction drowsy .Respiration appears shallow ?

• U advise -ABG ?• NIV ? Invasive ventilation.?

Goals during Positive pressure ventilation

• Adequacy of ventilation• Oxygenation• Decreased work of breathing• Patient comfort• Synchrony with ventilator• Avoiding complication-VILI,VAP• Early wean ability

What mode ??Which setting ??

Settings

• Fio2• R.r• Tidal volume• I:E ratio• Trigger• Peep• Set alarms

Monitoring during ventilation• Pulse oximetry - 95 % • ABG

– pH. 7.32– PCO2- 55– Po2 414– HCO3 28

• EtCo2 -50• Chest x ray Vitals- P-120/min B.p- 90/60

Note—no replacement to a vigilant Intensivist bedside

Hypovolemia

What next?

• Wake up call for consultant?

• Registrar reports increase in pressure alarm repeatedly ? U Advice

• A)Suction• B)Nebulization• C) Chest X ray

PIP vs PplatPIP vs Pplat

NormalNormal High RHigh Rawaw

High FlowHigh FlowLow ComplianceLow Compliance

Time (sec)Time (sec)

Paw

(c

m H

Paw

(c

m H

22O)

O)

PIPPIP

PPPlatPlat

PIPPIP

PIPPIP PIPPIP

PPPlatPlatPPPlatPlat

PPPlatPlat

Interpretation of Ventilator Graphics v.1 ©2000 RespiMedu

Complications

• Related to intubation and extubation.

Ventilator related

• Extra pulmonary – gut ischemia, Water ADH +

• F• A• S• T• H• U• G

anand tiwari

Ancillary care

Give your patient a fast hug (at least) once a day*Jean-Louis Vincent, MD, PhD, FCCM

Day 3 patient start to wake up trigger ventilator frequently some breath stacking,vitals stable

• Restless ,bites the tube intermittently restless• As reported by the nurse and physiotherapist.• You suggest—• A)weaning• B) Sedate and ventilate

ABCDE bundle

Mechanical VentilationWeaning: Predictors (Parameters)

• Respiratory Rate < 30/min• Spontaneous Vt > 4 ml/kg

• Inspiratory Pressure > - 20 cm H2O

• Breathing Index (f/Vt) < 105

• PEEP < 8 cmH2O

• PaO2/FIO2 > 200

• FIO2 < .50

Winning modes

Esteban, N Engl J Med 1995; 332:345

Summary of recommendations of weaning

• Protocol-directed - favorable outcome• SBT or PS trials than-- SIMV• 30min and 120min trials are equally successful• Twice daily SBT no advantage over once daily• Sedation vacation better outcome.• Early compared to late tracheostomy leads to

better outcomes

So mechanical ventilation of normal lung should not end up in an abnormal lung… think & act!!!!!!!!