Difficult Oxygenation HELI.CLI.12 Purpose This procedure describes the processes and procedures for a lung protective strategy in the mechanical ventilation of patients that are difficult to oxygenate prior to and during retrieval, especially those with ALI / ARDS. Procedure Management of patients with difficult oxygenation. For Review Aug 2015 1. Introduction Greater Sydney Area HEMS is frequently tasked with retrieving patients with Acute Lung Injury (ALI) / Acute Respiratory Distress Syndrome (ARDS) and other patients who are difficult to oxygenate. In such patients the use of a protective ventilation strategy is recommended. 1,2 This strategy focuses on reduced tidal volumes (V T ), avoidance of high alveolar pressures (plateau pressure (P plat )) and the acceptance of elevated P CO2 (permissive hypercapnia). This protocol does not apply to obstructive pathologies such as asthma where high airway resistance is the main issue. 3. Scope Clinical Crew 4. Process 4.1 Pre-retrieval 4.1.1 When oxygenation/ventilation issues are identified in a patient planned for retrieval it is important to gather information during the phone handover to assist with mission planning. There is rarely any urgency to rapidly transfer the patient. 4.1.2 Ensure that the most senior doctor at the referring hospital is involved in the patient s care. 4.1.3 Assess whether current ventilation at the referring hospital is consistent with best practice and diplomatically suggest alternatives if not. 4.1.4 Ask for a period of test ventilation (one hour) at the referring hospital using an Oxylog 3000 plus or other transport ventilator if available, with documentation of ventilation parameters and blood gases if available. 4.1.5 Request a recent chest X-ray (within 6 hrs) if not already available If contemplating helicopter (non-pressurised) transfer, assess how expected altitude will further compromise oxygenation. (Consider fixed wing (sea level cabin) or road alternatives). 4.1.6 Involve the SRC in all cases where difficult ventilation is anticipated. Approved by: Executive Director, Health Emergency and Aeromedical Services Date Issued: 2013 pg.1
4.1.7 If adequate oxygenation during transfer is considered unlikely, the MRU and referring/receiving critical care consultants must be involved as it may be more prudent to arrange an early ECMO response. 4.2 Management of the Difficult to Oxygenate Patient 4.2.1 Patient positioning: Patients should be positioned as upright as their haemodynamic status and stretcher limitations will allow. 1,2 This aims to improve functional residual capacity (FRC), reduce V/Q mismatch, and improve alveolar recruitment.. 4.2.2 Sedation and NMJB: Lung protective strategies and recruitment manoeuvres require that the patient be well sedated. If patient-ventilator dys-synchrony or high pressures persist after adequate sedation, then the patient should have a trial of neuromuscular blockade (paralysis). 4.2.3 Ventilator Set-up: The Drager Oxylog 3000 plus 3 is the preferred transport ventilator for difficult to ventilate patients and should be taken on ALL missions where handover information suggests difficulty in ventilating a patient. Note the Oxylog 3000 plus is NOT stored routinely in the EC145. 4.2.4 Goals of Ventilation o SpO 2 88 92%: o ph 7.10 o P plat 30 mbar Rather than simply titrating up the FiO 2, the physiologic approach to hypoxaemia in the absence of confounding factors is to increase the mean airway pressure (P mean ) by increasing PEEP provided it is haemodynamically tolerated. PEEP should be increased as required to a maximum of 20 mbar (Maximum PEEP for Oxylog 3000). (Note: If PEEP > 10 mbar is required, press the rotary knob to Confirm PEEP above 10? ) Tidal volumes should be kept low with V T of 4-6mL/kg of ideal body weight. A rising PC02 with a falling ph (permissive hypercapnia) is generally well tolerated. The P plat should preferably be kept below 30 mbar (a P peak below 40 mbar is a reasonable surrogate during volume cycled ventilation if P plat is not available. Approved by: Executive Director, Health Emergency and Aeromedical Services Date Issued: 2013 pg.2
Typical respiratory rates for adult patients with ALI/ARDS range between 15 and 25 breaths per min. 5. Recruitment manoeuvres 1,3 In ARDS /ALI consider performing a recruitment manoeuvre. This aims to open as many closed lung units as possible. Several manoeuvres may be needed for full effect. Recruitment may be accomplished by manually ventilating with a self inflating bag with a PEEP valve for 60-90sec followed by increasing PEEP on the ventilator. Another strategy using a ventilator is to incrementally increase PEEP (e.g start at PEEP of 5 mbar, and use 5 mbar increments every 30 sec to a maximum of 35 mbar), and then decrements (steps as per increase) to a higher baseline PEEP (e.g 10 or 15 mbar). During this manoeuvre, limit the P peak to 35 mbar (which will mean that tidal volume will progressively decrease during the manoeuvre to zero, and then progressively increase again. (Note that the Oxylog 3000 has a maximum PEEP of 20 mbar, so this will be the endpoint of the manoeuvre once transferred to the transport ventilator.) To avoid loss of recruitment, ventilator disconnections should be minimised and the tracheal tube clamped between ventilator change-overs. 6. Unable to ventilate If after proceeding through the checklist the goals of ventilation can not be met with a transport ventilator, the case should be discussed with the SRC and referring / receiving ICU consultant. Depending on the clinical condition of the patient, consideration should be given to : - Delaying transfer until patient condition improves - High frequency/oscillatory ventilation - ECMO 7. Definitions ARDS/ALI: Acute Respiratory Distress Syndrome / Acute Lung Injury PCV: Pressure control ventilation P peak : Peak inspiratory airway pressure P mean : Mean airway pressure PEEP: Positive End Expiratory Pressure Approved by: Executive Director, Health Emergency and Aeromedical Services Date Issued: 2013 pg.3
8. Troubleshooting checklist: CHECK PATIENT ETT (+ suction) Ventilator circuit Breathing valve Examine patient for bronchospasm or tension pneumothorax and treat accordingly Consider CXR; bedside US Sedation / analgesia ± NMJB Patient positioning OPTIMISE VENTILATOR Oxylog 3000 Plus Aim SpO 2 88 95% Permissive hypercapnia Pressure control ventilation Limit airway pressure P plat 30 mbar, (P peak 40 mbar) Consider I:E ratio (longer I time) ARDS / ALI consider higher PEEP and recruitment manoeuvre STILL UNABLE TO VENTILATE ON OXYLOG 3000 Plus? Discuss with SRC / receiving ICU consultant Consider delaying transfer until patient s condition improves; ECMO; HFOV Approved by: Executive Director, Health Emergency and Aeromedical Services Date Issued: 2013 pg.4
Pressure vs Time for Volume Cycled Ventilation 9. References: 1. Dries DJ: key questions in the ventilator management of the burn-injured patient. Journal of Burns Care and Research. 2009; 30: 128-138. 2. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000; 342: 1301-1308. 3. Richard J-C, Maggiore SM, Mercat A: Clinical review: bedside assessment of alveolar recruitment. Crit Care 2004; 8: 163-169. 4. Drager: Oxylog 3000. Instructions for use manual. 5. Plantadosi CA, Schwartz DA: The acute respiratory distress syndrome. Ann Int Med 2004; 141: 460-470. 6. Diaz JV, Brower R, Calfee CS, Matthay MA: Therapeutic strategies for severe acute lung injury. Crit Care Med 2010; 38: 1644-1650. Approved by: Executive Director, Health Emergency and Aeromedical Services Date Issued: 2013 pg.5