Mechanical Ventilation Khaled Hadeli, M.D.

History

Criteria for mechanical ventilation Clinical Criteria, i.e. A.B.C Profound respiratory failure –RR >35 –MIF < 25 cm H2O –VC < cc/kg –PaO2 60% –PaCO2 >50 mm Hg with pH < 7.35

Physiology of MV Air moves in and out of the lung according to pressure gradient -ve pressure ventilation = creating negative intra thoracic pressure, i.e suck air in. +ve pressure ventilation = providing high pressure at the mouth, i.e push air in

Types of Ventilators -ve pressure ventilators –Iron lung –Rocking bed –Ventilator vest

Types of Ventilators cont. +ve pressure ventilators –Pressure triggered (cycled) Pressure control (PC) PC/IRV –Volume triggered (cycled) Asses control (AC) SIMV CMV = PC and AC PS

AC CMV, all breaths are machine breaths Back up rate Decrease work of breathing Complications: hyperventilation, Auto peep, ptx, patient need Sedation… You can start MV with this mode but you can’t wean.

SIMV Patient can breath- on his own- more than the set rate May boost with PS Increased work of breathing You can start MV and wean with this mode

PC You set the pressure limit You set the I:E OR T I Variable V m achieved Need to adequately sedate the patient Be careful how to put the order, “ total pressure v.s. pressure over the peep”

PC/IRV Normal I:E ratio = 1:2 IRV= 1:1, 2:1, 3:1 Use in ARDS when you can’t adequately oxygenate By trapping air increases the iPeep and improves oxygenation Heavy Paralysis and /or heavy sedation

PS Spontaneous breathing but each breath is boosted If patient don’t “trigger” the ventilator he will not get the breath Can be used in combination with SIMV

Ventilatory Settings I.Mode: PC, SIMV, AC, etc. II.Rate III.T V IV.Peep V.Fio2 VI.PS

Mode of Ventilation PC ventilation is more physiologic VC ventilation is used more because it is easy to operate AC ventilation if you want to rest the patient completely SIMV is an ok mode if added PS

Rate/ T V Corrects hypercapnea (respiratory alkalosis) TV cc/kg Correct for height/ gender Be aware of breath “stacking” Low TV ventilation/ ARDS

Fio2 Start with 100% Use peep to augment Decrease Fio2 to less than 40% ASAP 40%-60% low risk for ARDS More than 60% Dangerous zone

Peep Physiologic peep about 3 cm Increase as needed up to 25cm Peep above 10cm may affect CO Decrease peep no more than 2.5cm at a time

PS ventilation Can be an effective mode of ventilation if used solo Other uses include: combination with SIMV, overcome the ETT resistance, No PS if pt is on CMV or if pt has no spontaneous breathing Type of weaning

Special issues Permissive hypercapnea Recruitment maneuvers Best Peep Lung protective ventilation Triggering the ventilator Proning

CPAP Not a mechanical ventilation Pt provides the work of breathing Helps to keep air ways open –Rx sleep apnea (proximal air ways) –Improves oxygenation ( distal air ways) You can add PS to cpap

NIPPV CPAP wit /without PS Bilevel ventilation Neuromuscular diseases COPD Pulmonary edema (CPAP) High maintenance, needs the cooperation of MD, nurse, RT, and the patient

New modes of ventilations NO proven efficacy.

Weaning Should be started ASAP PS wean SIMV wean CPAP/T piece trial Wean to NIPPV

Liberation from MV Reversal of the primary condition leading to the respiratory failure Mental status Adequate strength “MIF” F/TV index ( rapid-shallow index) Spontaneous TV, rate, VC, Compliance

Sedation Adequate sedation, short acting sedatives with/without pain meds. Optimize the environment. Improve sleep cycles. TERN OF THE TV IN PATIENTS ROOM!! ICU psychosis

Paralytics Depolarizing (intubation), CI in denervated patients and with hyperkalemia. Non-depolarizing. Critical illness paralysis vs. steroid induced narcotizing myositis. Use minimal doses, avoid steroids, always sedate patients.

Care of the ventilated patient Nutrition DVT prophylactics GI prophylactics Daily* CXR Cuff leak Patient/ventilator synchrony ( sedation, paralysis, triggering, PS…)