Page 1

CLINICAL VIGNETTE 2016; 2:3

Editor-in-Chief: Olufemi E. Idowu. Neurological surgery Division, Department of Surgery, LASUCOM/LASUTH, Ikeja, Lagos, Nigeria.

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

1


MECHANICAL VENTILATION ABOLUDE M. O.

Department of Anaesthesia, Lagos State University Teaching Hospital, Ikeja, Lagos, Nigeria.

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

2


INTRODUCTION • CLASSIFICATION • INDICATION FOR MECHANICAL VENTILATION (MV) • TYPES OF VENTILATOR • MODES OF VENTILATOR • COMPLICATIONS OF MV/MGT • CONCLUSION Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

3


INTRODUCTION • A METHOD TO MECHANICALLY ASSIST OR REPLACE SPONTANEOUS BREATHING • FIRST DESCRIBED- GALEN • ALSO VESALIUS AND GORGE POE Type I respiratory failure- low oxygen, and normal or low carbon dioxide levels Type II respiratory failure- low oxygen, with high carbon dioxide Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

4


PRINCIPLES OF VENTILATION 1. NEGATIVE-PRESSURE VENTILATION

2. POSITIVE-PRESSURE VENTILATION

 ALSO KNOWN AS DRINKER AND SHAW TANK  DEVELOPED IN 1929  REFINED DURING POLIO EPIDEMIC 1940  PRINCIPLES=VACCUM-AIR INFLOW

• PPV CAN BE CLASSIFIED INTO: 1. NON-INVASIVE POSITIVE PRESSURE VENTILATION(NIPPV) A METHOD OF POSITIVE PRESSURE VENTILATION WITHOUT USE OF ETT AN EXAMPLE IS ‘WATER’S CIRCUIT 2. INVASIVE POSITIVE PRESSURE VENTILATION

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

5


• GUIDELINES FOR MV RESPIRATORY GAS TENSION DIRECT INDCES: -PaO2 < 50mmHg or PaCO2 >50mmHg in absence of metabolic acidosis DERIVED INDICES: -PaO2/FiO2 < 300mmHg

MODES OF MECHANICAL VENTILATORS 1. PRESSURED-CYCLE VENTILATORS: delivers inspired gas to the lungs until a preset pressure level is reached 2. VOLUME-CYCLED VENTILATORS: DELIVERS A PRESET TIDAL VOLUME TO THE PATIENT REGARDLESS OF THE PRESSSURE REQUIRED

TYPES OF MECHANICAL VENTILATORS 1. TRANSPORT VENTILATORS 2. ICU VENTILATORS 3. NICU VENTILATORS Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

6


MODES OF MECHANICAL VENTILATORS COMMON MODES OF VENTILATION 1. CMV (controlled mech. Ventilation) 2. ACV (assist-controlled ventilation) 3. IMV (intermittent mandatory ventilation) 4. SIMV (synchronised IMV) 5. PCV (pressure-controlled ventilation) 6. PSV (pressure-support ventilation) 7. IRV (inverse ratio ventilation) 8. HFV (High-frequency ventilation) Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

ADJUNCT MODES • PEEP- Positive end-expiratory pressure • CPAP- continuous positive airway pressure • BiPAP- bilevel positive airway pressure

7


BAG-VALVE-MASK RESUSCITATOR

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

8


A MECHANICAL VENTILATOR

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

9


INDICATIONS FOR MV • 1. HYPOXIA (HYPOXIC FAILURE) TYPE I -Pneumonia -Pulmonary edema from any cause -CVA -ARDS -Acute lung injury -Muscular dystrophies -Pneumothorax -COPD, shock , Sepsis, Hypotension

• 2. VENTILATORY FAILURE TYPE II -Drug overdose(opiates,narcotics) -Head injury -CVA -Gullian Barre -Poliomyelitis -Muscular dystrophies -Amyotropic muscular sclerosis -Myaesthenia gravis -Kyphoscoliosis

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

10


MODES OF MV CMV: -USED IN PT WITH NO RESP. EFFORT -PRESET RESP. FREQUENCY & VT -HEAVILY SEDATED AND PARALYSED -UNCONSCIOUS PATIENT, APNEIC

ACV: - PATIENT CAN BREATH -DELIVERS A SET MINIMUM NUMBER OF MANDATORY BREATHS IF SPONTANEOUS R.R FALLS BELOW PRESET

SIMV: -THIS MODE PREVENTS THE STACKING OF BREATHS -BY TIMIMING MECHANICAL BREATHS TO COINCIDE WITH SPONTANEOUS BREATH IMV: ALLOWS PATIENT TO BREATHE SPONTANEOUSLY THROUGH THE CIRCUIT WHILE THE VENTILATOR INTERMITTENTLY DELIVERS POSITIVE-PRESSURE AT A PRESET TIDAL VOLUME AND FREQUENCY A MODE FOR WEANING PATIENT OF VENTILATOR LESS BAROTRAUMA

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

11


INITIAL VENTILATOR SETTINGS • PEEP • VT • INSP. PRESSURE • FREQUENCY • I:E RATIO • PRESSURE TRIGGER • FLOW TRIGGER • INITIAL FiO2 • PRESSURE SUPPORT

= 5cm H2O = 7-10ml/kg = 20cm H2O = 10-15/min = 1:2 = -2cmH2O = 2L/min = 100% = 15cm H2O Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

12


Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

13


CONTINOUS I.V SEDATION MORPHINE • 50mg IN 50mg N/S INTO 50mls SYRINGE(1mg/ml) • 2-3mls BOLUS,INFUSION=3mls/hr • Dose range=0-5mls/hr FENTANYL • 2500mcg (UNDILUTED) IN 50mls SYRINGE(50mcg/ml) • 2-3 mls BOLUS,INFUSION=3mls/hr • Dose range=0-5ml

PETHIDINE • 500mg IN 50mls N/S INTO 50mls SYRINGE(10mg /ml) • 2-3mls BOLUS,INFUSION=3mls/hr • Dose range=0-5mls/hr MIDAZOLAM • 50mg IN 50mls N/S INTO 50mls SYRINGE • GIVE 2-3mls BOLUS,THEN STAR INFUSION AT 3mls/hr, CAN GO UP TO 5mls/hr IF SEDATION SCORE < 2

PENTAZOCINE • 300mg IN 50mls IN 50mls N/S INTO 50mls SYRINGE(6mg/ml) GIVE 2-3mls BOLUS THEN INFUSION AT 3mls/hr • Dose range=0-5mls/hr

PROPOFOL • 10mg/ml GIVE 2-3mls BOLUS THEN START INFUSION 5mls/hr • CAN GO UP TO 10mls/hr • CAN ADD MIDAZOLAM FOR DIFFICULT TO WEAN PATIENT

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

14


PARALYSIS PARALYSIS MAY BE OF BENEFIT IN SPECIFIC SITUATION e.g INTRACRANIAL HYPERTENSION OR UNCONVENTIONAL MODE OF RESPIRATION

DRAWBACKS TO PARALYSIS • LOSS OF NEUROLOGIC EXAMINATION • ABOLISHED COUGH • POTENTIAL FOR AN AWAKE PARALYSED PATIENT • DEATH FROM VENTILATOR DISCONNECT • DIFFICULT WEANING

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

15


COMPLICATIONS OF MV • PNEUMOTHORAX; BAROTRAUMA • VAP, BRONCHITIS • DECREASED CO/BP DUE TO INCREASE INTRATHORACIC PRESSURE • SEVERE HYPOXIA/HYPERCARBIA FROM ACCIDENTAL DISCONNECTION • WATER RETENTION- ADH IS INCREASED IN PATIENT ON MV • GI BLEEDS DUE TO STRESS ULCER- NEED FOR PROPHYLAXIS • DIFFICULTY IN WEANING FROM VENTILATOR

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

16


• WEANING FROM MV • INTACT AIRWAY REFLEXES AND A COOPERATIVE PATIENT ARE ALSO MANDATORY PRIOR TO COMPLETION OF WEANING • SIMILIARLY ADEQUATE OXYGENATION(ARTERIAL Hb SATURATION >90% WITH <5cmH2O PEEP IS IMPERATIVE PRIOR TO EXTUBATION • CLINICAL SIGNS OF IMPROVEMENT WHICH MAY BE SUPPORTED BY LAB AND RADIOGRAPHIC FINDINGS • THE MOST USEFUL WEANING PARAMETERS ARE ABG, R.R, RSBI

WEANING MODES ON MV

• IMV • SIMV • PSV

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

17


REFRENCES • CLINICAL ANAESTHESIOLOGY BY MORGAN 7th EDITION • OXFORD HANDBOOK OF ANAESTHESIA • BARASH CLINICAL ANAESTHESIA 5th EDITION • ANAESTHESIA SECRETS 3rd EDITION • ANAESTHESIA AND RESUSCITATION 2001

Copyright- Frontiers of Ikeja Surgery, 2016; 2:3

18

Fis 2016 vol 2 3 mechanical ventilation