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Similar to Ventilation in obstructive airway disease
Ventilation in obstructive airway disease
- 1. Ventilation In ObstructiveAirway Disease Dr Girish Agrawal Consultant Pulmonary, Critical Care and Sleep Medicine Ramkrishna Care Hospital Raipur C.G.
- 2. NIV Invasive Ventilation Criteria forIntubation Full Spontaneous Breathing NO YES Failure Success Success Success Acute Respiratory Failure Requiring Ventilatory Support
- 3. Indications and Contraindicationsof NIV Indications AT least Two of the following Criteria 1) R/R > 25/min 2) Moderate to severe acidosis Ph 7.25-7.30, Paco2 45-60 mm hg 3)Moderate to severe Dyspnea with use of accessory m/s of respiration and paradoxical breathing. Absolute -Cardio Respiratory arrest -CVS instability -Non respiratory Organ failure -Patent TOF -Inability to protect Airways -Un Cooperative Patient -Bad interface Relative -Copious Secretions -Nasopharyngeal abnormality -Extreme Obesity Contra Indication Pilbeams Mechanical ventilation Sixth edition
- 4. NIV Failure/ SwitchOver Respiratory Arrest R/R > 35 Severe dyspnea with Use of accessory m/s, Paradoxical Breathing PaO2 <40 or P/F <200 pH <7.25 and PaCo2 >60 mm hg Hypersomnolence, Impaired mental status CVS complications (Shock, hypotension, Heart Failure) Other circumstances (Metabolic abnormalities, Sepsis, Pneumonia, PE, Barotrauma, Massive Pleural effusion) Pilbeams Mechanical ventilation Sixth edition
- 5. Disease Specific Indication COPD AcuteExacerbation with dyspnea, tachypnea, Acute respiratory acidosis Plus atleast one of the following Acute CVS instability Aletred Mental Status Inability to protect Lower Airways Copious Secretions Asthma Exhaustion (eg. r/r progressively decreases, decreased level of consciousness), with Met acidosis, in presence of normal or increasing PaCO2 If audible b/l wheeze becomes distant air trapping increases (silent chest, hyper-resonant to percussion or fixed on palpation) Severe hypoxemia on O2 support CXR showing signs of Air trapping Altered Mental Status Life threatining Dysarrythimias Respiratory acidosis on Met acidosis Cadio-respiratory Arrest
- 6. Objectives Physiological objective To SupportGas Exchange Increase Lung Volume Reduce work of Breathing Clinical Objectives Reverse acute respiratory failure Reverse respiratory distress and muscle fatigue Reverse hypoxemia Prevent/reverse atelectasis and ,maintain FRC Reduce systemic and myocardial oxygen consumption To minimize associated complication Pilbeams Mechanical ventilation Sixth edition
- 7. Ventilator settings inCOPD Operator dependent Mode of Ventilation VC/ PC-CMV may unload the work of respiratory muscle more then IMV PC-CMV may be ideal as it provides Flow on demand to meet pt need Patient –triggered CMV in alert patient may increase the risk of hyperinflation Adjust Peak Inspiratory flow to meet patient’s demand in VC-CMV using descending Flow pattern : Flow >60 liters Vt 6-8 ml/ kg and r/r of 8-16/minute with Ti 0.6 -1.2 sec PEEP of 5 cm of H20 or about 70-80% of Auto PEEP (often 3-5 cm is adequate)
- 8. Monitor and minimizeDHI (auto-PEEP) by setting lowest possible Ve which leads to acceptable gas exchange –target patient Baseline ph and PaCo2 (usually pH of 7.3-7.4 and Paco2 of 50-60 mm hg) Provide Longest Expiratory Time (Te) If by increasing PEEP , PIP start rising then safe limit has been crossed P Plat should be kept below 30 cm of H2O Maintain PaO2 at 55-75 mm Hg or near patient Normal with Fio2 less then 0.5 Other Suitable modes is VAPS as it provides Pressure ventilation with set Volume Pilbeams Mechanical ventilation Sixth edition
- 9. Ventilator settings inBronchial Asthma PC-VC/CMV are acceptable, easier to control Pressure with PC-CMV Plat < 30, Maintain Minimal PIP Target Pao2 60-100 mm hg (fio2>0.5) Permissive Hypercapnia (PaCo2 45-80 mm hg) , pH >7.20 Bicarbonate can be used as and when required to maintain pH Paralytics if required then for first 24 hour only PEEP only to counter PEEPi (as already has high FRC)
- 10. If PIP increasewith PEEP e- decrease PEEPe Prolonged Expiratory time R/R <8 /min Vt6-8 ml /kg, Ti<1sec, Inspi flow 80-100 ml / min with descending flow pattern Pilbeams Mechanical ventilation Sixth edition
- 11. Trouble Shooting Auto PEEP(PEEPi) Dynamic Hyperinflation Time Constant
- 12.
- 13. Weibel ER/ westJB: Respiratory Physiology 9th ed Anato mical Dead Space Dist- 5 mm Note Extemely Rapid Increase in total cross sectional are of airways in Respiratory Zone As a result gas Flow changes from Conductive to diffusive mode and spatial co relation of Flow
- 14. In other words Allthe alveoli are not equally ventilated, even in normal lung Tc of a region of Lung is product of its resistance and compliance Reasons are Gravitational and non gravitational influence on gas distribution Time Constant (Tc) is Non – Gravitational concept, besides series in-equality.
- 15. • It isspecific for particular region of lung • i.e diff for diff region or diff lung unit • i.e each lung unit inflates and deflates at different time constant • A unit with large Tc is still incompletely filled before expiration starts i.e poor ventilation • i.e at higher respiratory rate , lesser time for ventilation • A unit with small TC , filss rapidly, and may receive higher proportion of gas from anatomic dead space, hence poor ventilation • Smaller lung unit (small Tc) recieves greater gas flow by diffusion due to asymmetry of structure
- 16. A, Filling ofa normal lung unit. B, A low-compliance unit, which fills quickly but with less air. C, Increased resistance; the unit fills slowly. If inspiration were to end at the same time as in (A), the volume in (C) would be lower
- 17. Dynamic Hyper Inflationand Auto PEEP
- 18. Airway Closure andClosing Volumes In Young individual Airway Closes at volume below FRC In Older Individuals airway Closes at increasing Volumes and may approach FRC Similar Situations is seen in Patient with COPD
- 19. Equal Pressure Point Pressureinside Lung =Ppl +Recoil pressure At EPP pressure inside Airway is equal to intrathorasic pressure and airway tends to collapse As air passes through tube , pressure drops occur Increase effort will increase pleural, as well lung recoil pressure as a result it causes greater narrowing of airway downstream to EPP and flow remains constant Chest Wall Lung Equal Pressure Point (pressure is equal to Ppl)
- 20. Dynamic Hyperinflation Worsening ofSmooth muscle cell contraction, Airway Wall edema and luminal obstruction with mucus are the reason for Asthma Exacerbation This trapping of air is called Dynamic Hyper inflation Narrowing of the airways (smooth muscle contraction) occurs disproportionately in medium and large bronchi As a result patient breaths at higher FRC’s , have low Tidal Volume and thus Low FVC EPP is reached much distally- leading to air trapping
- 21. Levy BD, KitchB, Fanta CH: Medical and ventilatory management of status asthmaticus. Intensive Care Med 1998, 24:105-117.
- 22. 10 cm H2o 10 cmH20 Obstructed Airway 0 cm H2O Alveolar Pressure Pleural Pressure Ppl=Palv Cleveland Clinic Journal of Medicine Volume 72. Number ( Sep2005)
- 23. Auto- PEEP (PEEPi) Presenceof Positive Pressure in alveoli at the end of Expiration that is greater than atmospheric pressure without application of external PEEP Dynamic hyperinflation ,without Intrinsic expiratory flow limitation Dynamic hyperinflation ,with Intrinsic expiratory flow limitation Exaggerated expiratory Activity without dynamic hyperinflation It can be measured by applying Pause at the end of Expiration Three Types
- 24. Physiologic Mechanism ofauto positive end expiratory pressure Dynamic hyperinflation with intrinsic expiratory flow limitation COPD Dynamic hyperinflation without intrinsic expiratory flow limitation Breathing Pattern and ventilator settings Rapid Breaths High Tidal Volume Inspiration greater than expiration End-inspiratory Pause Added flow resistance Fine-bored endotracheal tube Ventilator tubings and device obstruction Without dynamic hyperinflation Recruitment of expiratory muscles
- 25. How to recognizeAuto-PEEP • Exhalation that continues until the next breath starts, as seen on graphic display of expiratory flow vs time in a patient on a ventilator that is set to deliver a certain number of breaths per minute • A delay between the start of inspiratory effort and the drop in airway pressure or the start of machine-delivered flow in a patient on a ventilator that is set to deliver breaths on demand • Failure of peak airway pressure to change when external PEEP is applied • In paralyzed or heavily sedated patients, reduction of plateau pressure after prolonged exhalation.
- 26. Exhalation Valve closedduring exhalation hold Cleveland Clinic Journal of Medicine Volume 72. Number ( Sep2005)
- 27. Decrease trigger Sensitivity(to generate negative pressure that is great enough to trigger the ventilator ) Hemodynamic Compromise (increased Intra-thorasic pressure – decrease venous return) Hyperinflation- Volutrauma Consequences Increased work of breathing , leading to fatigue
- 28. Note Failed triggerand sucessful trigger
- 29. Occult PEEP Non- Homogenouslung ventilation Crti Care Med 1996:;24:541-546
- 30. Treatment of auto-positiveend-expiratory pressure Change ventilator settings Increase expiratory time Decrease respiratory rate Decrease tidal volume Reduce ventilatory demand Reduce anxiety, pain, fever, shivering Reduce dead space Give sedatives and paralytics Reduce flow resistance Use large-bore endotracheal tube Suction frequently Give bronchodilators Counterbalance expiratory flow limitation External positive end-expiratory pressure
- 31. -1 cm H20 -3cm H20 -13 cm H20 Increased Work of breathing +10 cm H2o +8 cm H20 +9 cm H20 +6 cm H20 PEEPe allows negative deflections in Ppl Cleveland Clinic Journal of Medicine Volume 72. Number ( Sep2005)
- 32. GOTTFRIED SB: THEROLE OF PEEP IN MECHANICALLY VENTILATED COPD PATIENT. IN MARINI JJ, ROUSSOS C (EDITORS): VENTILATORY FAILURE. NEW YORK, SPRINGER-VERLAG,1991:392–418:
Editor's Notes
- #14 Spatial Flow : neighbouring region will have similar flow then region located apart
- #20 Similarly there is bernoulli effect It says that as gas flows through a tube , lateral pressure exerted by particles are less then the pressure driving flow by an amount proprotional to velocity of the gas. Thus as gas velocity increases there is tendency for tubes to collapse. Bernoulli effect is prominent at high volumes and flow , where as EPP is important at low volumes and flow
- #33 Top, expiratory flow limitation within a lung. The alveolar pressure at the end of passive expiration (auto-PEEP) in a dynamically hyperinflated patient exceeds the critical pressure at which dynamic airway compression occurs. External PEEP, applied at the airway opening, will not worsen auto- PEEP if it does not exceed the critical pressure. Bottom, analogous circumstances governing hydrostatic pressure above and below a waterfall. The amount of flow over the waterfall remains constant until the level of water in the stream below (the airway pressure) reaches the height of waterfall (the critical pressure) but not the stream above (the alveolar pressure).