1. Mechanical ventilation
Dr.Poddutoori
PGY3

2. Introduction
Specially designed pumps that support Ventilatory functions of RS and improve oxygenation through high O2 and positive pressure.

3. Indications for MV Hypercarbic resp failure: Hypoxemic Resp Failure:
Basically decreased Min Ventilation or increased Physiologic dead space.
Neuromuscular disease:M. Gravis, Ascending polyradiculopathy, Myopahty
Muscle fatigue diseases: Asthma, COPD, restrictive lung disease
Pco2 >50mm Hg and Ph <7.3
Hypoxemic Resp Failure:
Basically a V/Q mismatch and shunt problem
Pneumonia, Pulm edema, ARDS, Pulm hemorrhage
Sao2 <90 despite >60% fio2.

4. Other indications for MV
Increased ICP – controlled Hyperventilation to reduce cerebral blood flow
Post Op pulmonary HTN: to improve pulmonary hemodynamics
CHF in presence of Myocardial ischemia: To reduce preload and afterload and to reduce work of breathing
Prevent aspiration of Gastric contents: unstable patients needing Lavage for drug overdose and EGD

5. Physiologic aspects of MV
Hypoxia : fio2
Hypercarbia: TV x RR = Min Ventilation
PEEP helps maintain patency of alveoli – reverses hypoxemia and atelectasis by improving V/Q matching
Normal is Can be increased if refractory hypoxemia needing Fio2 >0.6

6. Modes of ventilation O2 by Nasal cannula, ventimask, Nonrebreather
Non Invasive Positive pressure ventilation: CPAP and BIPAP
Invasive ventilation:
Assist control
SIMV

7. Establishing and maintaining airway
Cuffed ETT is used to maintain Positive pressure and prevent aspiration
Medications used:
Sedatives – avoid long acting benzos. Use Propofol or etomidate
Analgesics – Avoids morphine – can worsen bronchospasm. Use fentanyl.
Paralyzing agents – Succinylcholine should be avoided in renal failure, Tumor lysis, Hyperkalemia.

8. When do you consider tracheostomy?

9. Terminology
Modes:refers to the manner in which ventilator breaths are triggered,cycled and limited. SIMV, AC
Trigger: defines what the ventilator senses to initiate an assisted breath -an inspiratory effort or time based signal
Cycle: refers to factors that determine the end of inspiration – volume, pressure or flow or time cycled.
Limiting factors: are operator specific values: ex Airway pressure.

10. Assist control mode
Inspiratory cycle is initiated by inspiratory effort of pt or by timer signal ( back up rate)
Every breath delivered consists of operator specified TV.
Vent rate is determined by either by pt or Operator specified backup rate – which ever is higher

11. ACMV
Advantages:
Often used for initiation of MV – to ensure backup min Ventilation and synchronization of vent cycle with pts insp effort.
Disadvantages:
-Respiratory Alkalemia:leading to myoclonus and seizures
-Dynamic hyperinflation – auto PEEP and barotrauma, decreased Cardiac output.

12. SIMV Pt is allowed to breath spontaneously
Preferred in pts with intact resp drive
Fixed mandatory breaths are delivered in addition to pts RR.
Only the preset number of breaths are ventilator assisted.
Total respiratory rate is Pts RR + Preset rate

13. SIMV Advantages: Exercise respiratory muscles Easy to wean
Disadvantages:
-difficult to use in tachypnea- as dysynchrony might occur
-cannot be used paralyzed pts.

14. CPAP and BiPAP Non invasive ventilation
Used early stages of respiratory distress
Pt should be alert and cooperative
CPAP can also be used to assess extubation potential in intubated pts.

15. General support in ventilated patients
Sedation – Propofol or etomidate
Analgesia - fentanyl is best
GI prophylaxis: H2 receptor blockers/ carafate/antacids – carafate is preferred as it doesn’t change gastric Ph – so less colonization by nosocomial organisms
Nutrition support: Early feeding is encouraged.
Delayed Gastric emptying: Consider Reglan

16. Complications of MV Pulmonary:
Barotrauma ( if Pr >50cm H2O )
Vent Associated Pneumonia –( If intubated >72 hrs) – G –ve rods, S.Aureus, Anaerobes.
O2 toxicity
Tracheal stenosis
Respiratory deconditioning
Hypotension – almost always responsive to Volume support
GI:
Stress ulceration– H2 receptor blockers / sucralfate
Cholestasis – Total bilirubin < 4 mg/dl

17. Weaning criteria - MV
Upper airway functioning should intact – stridor or aspiration.
Intact cough – mobilizes secretions
Alveolar ventilation: Ph 7.35 – 7.45, Sao2 >90 %,Fio2 <0.5, PEEP <5.
Respiratory drive and chest wall function should be assessed ( TV, Insp Pressure, RR, VC)
Weaning index: breathing frequency/ TV <105.
VC >10 ml/kg, Insp Pr> -30 cm H2O.

18. Methods of weaning
Short term ventilated pts: 5 min/ hr. Gradually increased every hour.
T Piece ( on O2)
CPAP
Long term ventilated pts:
SIMV – decrease mandatory backup rate 2-4 breaths/min and reasses each time( if >25 or worsening PH indicates difficulty in weaning)
PSV - Gradually reduce the pressure to below Peak insp pressures by 5cm H2O until the pressures Just equal to ET tube pressure (5-10 normally)

19. THANK YOU!