1/ How to identify/categorise/monitor the patient ...



Acute respiratory failureClinical problemsLEARNING OBJECTIVESAfter studying this module on Respiratory failure, you should be able to:Identify patients suffering from acute respiratory failure (ARF)Understand strategies for providing ventilatory supportBecome familiar with the associated supportive measuresRecognise and know how to manage the complications of ventilatory supportFACULTY DISCLOSURESThe authors of this module have not reported any disclosures.DURATION7 hoursCopyright?2009. European Society of Intensive Care Medicine. All rights reserved.ISBN 978-92-95051-62-1 - Legal deposit D/2005/10.772/9IntroductionAcute respiratory failure (ARF) is a common and important indication for admission into critical care units and is associated with a substantial mortality. For the purpose of this module, ARF is defined as any acute lung condition (with the exception of obstructive lung disease) that requires active ventilatory therapy.The reader should also be aware that there are a variety of clinical conditions that can precipitate ARF, such as acute cardiogenic pulmonary oedema, fluid overload, massive pulmonary embolism and coma. ARF is not a disease in itself but a reaction to an underlying condition, e.g. trauma, sepsis or pneumonia. Because definitions differ, the incidence and mortality rates for ARF vary across studies. In addition, the underlying condition strongly influences prognosis.Acute respiratory failure is always caused by an underlying condition that will need urgent treatmentMost ARF discussed in this module is due to lung failureThe reported incidence of ARF, including acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) varies between around 78–149 per 100 000 people >15 years of age per year.Ninety-day mortality is close to 40% for ARF and 31–60% for ALI / ARDS. Whether mortality?rates have decreased over time is still a?matter of debate.?The majority of patients have ARF of pulmonary origin with pneumonia as the predominant diagnosis.1/ How to identify/categorise/monitor the patient suffering from ARFThis Task will provide you with definitions, outline aetiology, risk factors, clinical manifestations and symptoms. The Task concludes with a section on how to monitor the course of acute respiratory failure.DefinitionsFor the purpose of this module, we will focus on ALI and ARDS. The definition of ARDS is under discussion but the definition proposed by a Joint North American–European consensus committee (NAECC) in 1994 is still accepted. ARDS is defined as an inflammatory process in the lungs with:An acute onset of respiratory failureNew bilateral pulmonary infiltrates on frontal chest radiograph or computed tomography (CT)?Absence of left ventricular failure (clinically diagnosed or a pulmonary artery occlusion pressure <18 mmHg)Hypoxaemia with a ratio between the partial pressure of oxygen in the arterial blood and the fraction of inspired oxygen (PaO2/FiO2) ≤27 kPa (201 mmHg) independent of the level of positive end-expiratory pressure (PEEP)ALI is defined by the same criteria except that the PaO2/FiO2?ratio is between 27 kPa (201 mmHg) and 40 kPa (300 mmHg).ALI/ARDS is a pulmonary inflammatory processHowever, there are problems with this definition:The definitions of left ventricular cardiac failure are vague, and the interpretation of a chest radiograph may be difficult.Lung recruitment manoeuvres and PEEP influence both the degree of hypoxaemia and the appearance of the chest radiograph.The PaO2/FiO2?ratio is dependent on the FiO2?used.It has been suggested, therefore, that the definition should be modified, for example by defining 'acute' and by specifying the PEEP level and the FiO2?at which PaO2?should be obtained (see references below).Another commonly used, but more complicated definition was suggested by Murray; the Lung Injury Severity Score (LISS). In this score, the PaO2/FiO2?ratio, the chest radiograph, compliance of the respiratory system and the level of PEEP are scored on a scale 0-4. If compliance is not measured this variable can be omitted and if the patient is not receiving mechanical respiratory support PEEP can also be excluded. The sum of the scores is then divided by the number of components. A total score greater than 2.5 defines ARDS.Heart failure can exist concomitantly with a pulmonary inflammatory process similar to ALI/ARDSNoteNeither LISS nor the initial degree of arterial hypoxaemia?(if PaO2?is not severely low) are related to outcome.In the next five patients who are admitted to your ICU with ARF check whether they fulfil the ARDS definition by LISS, the NEACC criteria or both. Please check the level of PEEP. For more information about the different definitions of ALI/ARDS see the following references.Aetiology and risk factorsALI/ARDS is an acute inflammatory condition in the lungs and not a disease in itself, and is therefore always due to an underlying disease process.The pulmonary inflammation may be caused by:A direct (primary or pulmonary) injury to the lungs orAn indirect (secondary or extra-pulmonary) injuryALI/ARDS due to a direct injury comprises 50-60% of all cases, with pneumonia as the most important single cause (40-50% of all cases). Other common direct causes are aspiration of gastric contents, pulmonary contusion, inhalation of toxic gases and near drowning.Indirect ALI/ARDS is caused by systemic inflammation with generalised activation of mediators, inflammatory cells and endothelium due to infection (sepsis, peritonitis), tissue ischaemia or tissue damage (trauma, cardio-pulmonary bypass, pancreatitis, major surgery and some intoxications and overdoses).Experimental and recent clinical studies have shown that ALI/ARDS might also be due to, or be accentuated by mechanical ventilation using high tidal volumes and low levels of PEEP.The independent risk factors for ARF are old age, infection, neurological disease, alcohol abuse and multiple transfusions.Because ALI/ARDS is always caused by an underlying disease process, treatment of precipitating factors, together with the patient's comorbidities and genetic predisposition are major determinants for the progression of the lung condition and its outcome.ThinkWhy are old age, neurological disease, infection, multiple transfusions and genetic diversity important risk factors for the development of ARF? See the references below for further information.Clinical manifestations and symptomsClinical manifestations and symptoms may be divided into:Pulmonary, caused by ALI/ARDS andExtra-pulmonary, caused by the underlying diseaseAscertain the diagnosis: laboratory tests and imagingAccording to the definitions, the diagnosis of ALI/ARDS is first established by:The medical history: acute onset of respiratory failure in combination with an underlying condition which has the potential to initiate pulmonary inflammation.A recent frontal chest radiograph or thorax CT showing bilateral infiltrates.A clinical examination (and medical history), echocardiography or pulmonary artery catheterisation (PCWP <18 mmHg) to exclude significant left ventricular failure.An arterial blood sample together with measurement of FiO2, showing a PaO2/FiO2?ratio ≤27 kPa for the diagnosis of ARDS and <40 kPa for the diagnosis of ALI.Early in ALI/ARDS, the blood gas analysis might, in addition to hypoxaemia, show a degree of hypocapnia due to an increased ventilatory drive induced by increased stiffness of the lungs. In addition, the patient is usually apprehensive. Respiratory acidosis develops rather late in the process and signals imminent respiratory decompensation. Metabolic acidosis may be seen, but usually this is a consequence of the underlying process (sepsis or tissue hypoperfusion) rather than ALI/ARDS.The results of other laboratory tests are usually non-specific and dependent on the underlying disease. It is common to find evidence of inflammation and coagulopathy.In ventilated patients, lung mechanics show a low respiratory system compliance and functional residual capacity is reduced.Clinical examination and obtaining a medical history are extremely important in the management of ALI/ARDS?How can you determine whether a low compliance (high elastance) is due to a pulmonary condition or to a stiff chest wall, e.g. caused by intra-abdominal distension?See the PACT module on Respiratory monitoring for more information?The chest radiograph typically shows bilateral interstitial infiltrates that later become diffuse and fluffy. In addition bilateral basal atelectasis?is common. Therapeutic intervention, i.e. recruitment manoeuvres and application of PEEP, might modify the findings and sometimes even normalise the appearance of the chest radiograph.NoteA chest radiograph obtained during expiration,?compared with one taken during inspiration will show more pronounced puted tomography (CT) examinations are useful for evaluation of the lung pathology. CT can more accurately define infiltrates, pleural effusions and small pneumothoraces especially those lying anteriorly or posteriorly. In extrapulmonary ARDS, bilateral symmetrical dorsal and caudal densities, indicating lung collapse and alveolar oedema, are common when the patient is supine. Bilateral pleural effusions are also typical findings. In pulmonary ARDS the more dense lung regions tend to be asymmetrical and localised to the areas most affected by the primary process. However, these differences in apprearance between pulmonary and extra-pulmonary ARDS are not always conclusive. Furthermore the findings change with time as the process evolves.ThinkConsider the benefits of obtaining a CT versus the costs and risk of moving the patient from the ICU.How to monitor the course of ARFSee also the PACT modules on Mechanical ventilation?,?Respiratory monitoring??and Haemodynamic monitoring?ALI/ARDS is frequently part of the multiple organ dysfunction syndrome. Therefore, it is important to monitor and detect early signs of additional organ involvement, e.g. renal dysfunction, and to rapidly institute measures to prevent further deterioration. Maintaining adequate tissue perfusion is of paramount importance, especially when arterial oxygenation is compromised.Monitoring is useless without correct interpretation of the data and appropriate decision makingNoteBefore initiating monitoring, particularly with invasive devices,?always consider whether such monitoring has the potential to usefully influence patient management.In all types of ARF, continuous monitoring should include:Depth of sedationRespiratory frequencyFiO2Peripheral oxygen saturation by pulse oximetryIn addition:If the patient is mechanically ventilated, all relevant ventilatory variables are automatically and continuously obtained. It is important to check that alarm limits for tidal volumes and pressures are set correctly.Ventilatory variables (mode, PEEP, auto-PEEP, peak and plateau pressures, tidal volume, inspiratory:expiratory (I:E) ratio, ventilator rate) should be noted at prescribed regular intervals.Arterial blood gases should be sampled at regular intervals and when deterioration in the patient's condition is clinically evident.A chest X-ray should be performed at least twice weekly if the course is benign and more often in those with severe lung injury.Continuous measurement of systemic blood pressure.Fluid balance and urine output should be updated hourly.Do not forget to examine the patient frequently!Additional monitoring (airway pressure-lung volume relationships, lung volume measurements, mixed venous or central venous oxygen saturation, cardiac output measurement, echocardiography, pulmonary artery catheterisation, or arterial transpulmonary indicator dilution catheter) should be instituted according to the severity of respiratory failure and the level of support required, as well as the degree of additional organ dysfunction and support. Nutritional therapy should be monitored biochemically. The clinical utility of a promising new monitoring method, electrical impedance tomography, is not clear.In the next five patients with ARF in your ICU observe the monitoring techniques employed. Do you agree with these monitoring protocols? Give arguments (pros and cons). Discuss the issues with your supervisor or a colleague.2/ Strategies for ventilatory support (lung protective ventilation)See also the PACT module on Mechanical ventilation?The goal for ventilatory therapy in ARF is to achieve adequate gas exchange (usually PaO2?>8 kPa, oxygen saturation of haemoglobin in arterial blood (SaO2) >90% and pH 7.2-7.4) without causing additional iatrogenic damage to the lungs and other organs, i.e. a lung protective ventilatory strategy. In this context it is important to recognise that a ventilator can only replace the work performed by the respiratory muscles and not the gas exchange function of the lungs. However, by using lung recruitment manoeuvres, positive end-expiratory pressure and by changing the inspired oxygen concentration, gas exchange can be improved and supported.In the reference below you will find more information about ventilatory support of patients with ARDS.?When to initiate ventilatory support?As a general rule,All patients with ALI/ARDS should immediately receive oxygen via a mask.If hypoxaemia persists and the clinical condition does not improve rapidly more active measures are urgently required.If the patient has concomitant conditions that compromise cardiopulmonary function, more active measures should be considered early.The mean inspired oxygen concentration via a standard face mask is only 40-50% at flow rates of 10-15 l O2?/minThe patient's clinical condition is more important than the values obtained by blood gas analysis in deciding when to start ventilator support.If the patient is fully awake, haemodynamically stable and is not fatigued there is no immediate need for ventilatory support even if blood gases indicate hypoxaemia. On the other hand, because almost all patients with ALI/ARDS require some form of ventilatory support, mechanical ventilation should always be considered early in the disease process.If the patient is exhausted, has a respiratory rate above 30-35/min, blood gases indicate significant hypoxaemia (PaO2?<7-8 kPa) on oxygen via mask, an increasing carbon dioxide pressure in the arterial blood (PaCO2) or pH is below 7.3 (showing that the patient cannot maintain a normal pH by spontaneous breathing) mechanical ventilation should be instituted expeditiously.If the patient is haemodynamically unstable but can maintain PaO2?above 8 kPa on oxygen via mask, haemodynamic support is indicated under careful ventilatory monitoring before invasive ventilatory support (intubation) is initiated.Oxygen consumption and CO2production increase by 6-10% per °C. This increased demand can exacerbate respiratory distress?Why does a low PaO2?not necessarily indicate tissue hypoxia? How can you improve tissue oxygenation without increasing PaO2?See PACT module on Respiratory monitoring for further information?Sedation and initiation of positive pressure ventilation may cause severe cardiovascular collapse in hypovolaemic patients.In the last five patients with ARF in your department what were the PaO2, PaCO2, arterial pH and respiratory rate before initiating ventilator therapy.Should we start a trial with non-invasive ventilation (NIV)?Non-invasive support with continuous positive airway pressure (CPAP) may be considered in otherwise stable patients with hypoxaemia in the absence of CO2?retention. Non-invasive positive pressure ventilation? is otherwise the preferred method in patients with ARF. NIV can only be considered if the staff members are experienced with the method and if the patient is:Fully consciousCooperativeHaemodynamically stableTolerant of short periods without ventilatory supportAble to take adequate tidal volumesNot fatiguedThe trial of NIV should be terminated if the patient does not markedly improve clinically within an hour.NIV should always be considered in patients who are immunosuppressed because of the importance of preventing nosocomial infections in such patients (tracheal intubation is associated with nosocomial pneumonia and sinusitis). This approach has been associated with improved outcomes.Never delay initiating invasive ventilation by applying NIV to a patient who is exhausted.AnecdoteA patient infected with human immunodeficiency virus (HIV) with bilateral pulmonary interstitial infiltrates on the chest radiograph was transferred to the ICU at 2.00 a.m. He was at that time fully awake, his respiratory rate was 40/min and his PaO2?was 7 kPa on? face mask O2?at 15 l /min. Pneumocystis jiroveci pneumonia was suspected and trimethoprim-sulfmethoxazole was started. Because the patient was cooperative NIV was started with pressure support ventilation (see PACT module on Mechanical ventilation) of 15 cm H2O above 5 cm H2O PEEP and FiO2?of 1.0. The patient improved initially. After two hours the patient became more tired with increasing PaCO2?and decreasing pH. However, since it was early morning (5.00 a.m.) the nurse decided to wait a further hour before informing the intensivist on call. When the intensivist arrived just after 6.00 a.m. he found the patient severely lethargic and exhausted with an arterial oxygen saturation of 77% on pulse oximetry. An emergency oral tracheal intubation was performed but unfortunately the patient developed cardiac arrest, which could not be reversed. This case illustrates the need for continuous close attention by experienced staff and that invasive ventilation should be instituted promptly if NIV is not successful.?What are the advantages and disadvantages of NIV in patients with hypoxaemic respiratory failure?See PACT module on Mechanical ventilation?Be aware that the administration of 100% oxygen for a prolonged period can exacerbate atelectasis.Intubation /tracheostomyThe indications for intubation in ARF are:Inadequate gas exchange with non-invasive respiratory support (oxygen via mask, CPAP or NIV) orWhen NIV is contraindicated or believed to be insufficient, e.g.Severe hypoxaemia (PaO2?<6-7 kPa)Severe respiratory acidosis (pH <7.2, PCO2?> 9-10 kPa)Semi-or unconscious/ unable to maintain and protect the airwayConcomitant central nervous system compromise (head injury, brain oedema due to meningitis, intracerebral bleeding, spinal injury)Recent surgeryIn patients with ARF there is a significant risk of complications during tracheal intubation:Pronounced hypoxaemiaAspiration of gastric contentsMisplacement of the endotracheal tubeHaemodynamic compromiseIntubation, therefore, should be performed with great caution. Because the indications are hypoxaemia or respiratory fatigue, immediate successful tracheal intubation is essential. All means to rapidly secure a safe airway should therefore be available; a variety of laryngoscopes, different designs and sizes of endotracheal tubes, stylets, bougies, forceps, a fibre optic bronchoscope or laryngoscope, airways and devices for cricothyroidotomy. It must be possible to suction and to administer 100% oxygen. It is important to avoid worsening of hypoxaemia during the procedure by administering 100% oxygen or maintaining NIV as long as possible before intubation.Always use capnography to confirm that the tube is correctly positioned in the tracheaThere are three different approaches for intubation:Oral intubationFibre optic awake intubationBlind nasal intubation?Oral intubationIf the patient is obtunded, oral intubation is the technique of choice. Oral intubation is easier, quicker and safer to perform than nasal intubation and in addition is associated with a lower incidence of sinusitis. Before? intubation, the equipment and the tube should be checked, and a decision made about the amount and type of drugs to be used to facilitate intubation. A skilled assistant should be available. These patients usually have slow gastric emptying and are at risk of regurgitation of stomach contents followed by pulmonary aspiration. Therefore a rapid sequence intubation with cricoid pressure should be performed.ThinkWhat do you do if you cannot intubate at the first attempt in a patient with ARF? What are your department's guidelines??See PACT module on Airway management for more informationFibre optic intubationFibre optic intubation is a good and safe choice in an awake patient, particularly if the upper airways are compromised.Fibre optic intubation should replace blind nasal intubation in patients with ARF.Nasal intubation may induce serious nasal bleeding in patients with thrombocytopenia or coagulation disorders.?How do you confirm correct positioning of an endotracheal tube?TracheostomyTracheostomy isSeldom a first-line measure except when the patient has a compromised upper airway.Performed when it is anticipated that the patient needs lengthy ventilatory support or to facilitate the weaning process, as in severe head trauma.Relatively contraindicated during the critical phase when the patient requires high inspired oxygen and difficult to ventilate.Relatively contraindicated in patients with bleeding tendency or coagulation disorders.It is not clear whether tracheostomy, even when performed early can decrease morbidity or mortality compared with prolonged tracheal intubation. In clinical practice, however, tracheostomy is more comfortable for the patient, facilitates suctioning and oral hygiene as well as the weaning process.NoteIn patients with ARF, tracheostomy should be performed by a skilled and experienced member of staff.?The procedure can be performed surgically or percutaneously. The approach adopted is mainly determined by local practices.Assist at five tracheostomies (percutaneous or surgical). Discuss with the operator and your supervisor / colleagues, what the arguments are for surgical, percutaneous or both procedures being used.What are the targets of ventilatory support?The objective is to achieve adequate gas exchange without injuring the lungs and other organs. The gas exchange targets are not clearly defined. It is common practice to aim for a PaO2?and SaO2?above 8 kPa and 90%, respectively, but lower values may be acceptable as long as there are no signs of tissue hypoxia. In fact, no studies have shown that increasing PaO2?improves outcome. PCO2?in itself is seldom important, but pH should usually be maintained between 7.2 and 7.4.See the PACT modules on Mechanical ventilation?and Respiratory monitoring.?Hypocapnia constricts coronary and cerebral arteries and hampers oxygen unloading?What are the benefits or drawbacks of hypercapnia? See reference?below for more information.How to adjust the ventilator settings in a patient with acute respiratory failureThe ventilator settings should be adjusted to ensure adequate gas exchange without causing:OverdistensionRepeated opening and closing of distal unitsThus, tidal volumes and the transpulmonary pressure difference between inspiration and expiration should be kept low.Ventilatory modeThere are no ventilatory modes (including high frequency oscillatory ventilation) that have been conclusively proven to be superior in ARF as long as end-inspiratory plateau pressures and tidal volumes are limited. However, there is some suggestion that modes which allow for spontaneous breathing (e.g. airway pressure release ventilation, APRV), improve oxygenation and haemodynamics, contribute to lung recruitment and decrease the need for sedation. On the other hand, recent studies suggest that a short initial period with heavy sedation combined with muscle relaxation might be beneficial. See the references below for further information about APRV and muscle relaxation.Use your clinical judgment at the bedside when adjusting the ventilator settingsSee PACT module on Mechanical ventilation?If possible, use modes early that allow spontaneous breathing as early as possibleTidal volume and airway pressuresVentilation with a tidal volume of 6 ml/kg ideal body weight has been shown to significantly decrease mortality (by 9%) when compared with ventilation with 12 ml/kg tidal volumes. However, the acceptable tidal volume may be more dependent on the condition of the lungs; in small and highly inflamed lungs tidal volumes should probably be lower than 6 ml/kg but in larger and less inflamed lungs tidal volumes somewhat larger than 6 ml/kg are probably safe.The end-inspiratory plateau airway pressures should be kept low (<28–30 cm H2O). However, because the transpulmonary pressure is more important than the airway pressure, the compliance of the chest wall should be taken into consideration. In a patient with a compliant chest wall, e.g. a small child, an airway pressure of 30 cm H2O will translate into a high transpulmonary pressure and is likely to injure the lungs, while in an adult, obese patient with intraperitoneal pathology, an airway pressure of 40 cm H2O might generate a low, risk-free, transpulmonary pressure.Low tidal volume and low pressure ventilation may be associated with a reduction in CO2?elimination. The rise in a PaCO2?should be tolerated (an approach termed permissive hypercapnia).?How can you improve CO2?removal without increasing the tidal volume??What are the drawbacks of low tidal volume ventilation?See the PACT modules on Mechanical ventilation?? and on Respiratory monitoring?Case 2You get a request from the surgical ward?for possible transfer of a 42-year-old woman, with previously normal cardio-pulmonary health, to the ICU. She had been operated on four days previously with a right-sided colectomy and ileo-colic anastomosis?for carcinoma of the ascending colon. The surgery and anaesthesia were uncomplicated, but afterwards she developed nausea, vomiting and abdominal pain. Now she is complaining about difficulties with breathing and her temperature has increased to 39.5 °C. The surgical resident suspects pneumonia and wants her transferred to the ICU.When you arrive at the surgical ward you examine the patient. She is pale, slightly cyanotic but has good peripheral circulation. She has a respiratory rate of 28/min and is somewhat dyspnoeic. Over both basal lungs you can hear crepitations. The abdomen is tender and tense. The wound is not infected. Blood pressure is 100/60 mmHg and pulse rate is 120/min. The patient has no urinary catheter and does not remember when she voided. She has received thromboembolic prophylaxis (low molecular weight heparin) and prophylactic antibiotics during surgery.?Which diagnosis is most probable and why?Learning issues??Aetiology of secondary ALI/ARDS??Clinical signs of secondary ALI/ARDS??Differential diagnosis of postoperative lung disorders?What other diagnoses do you consider??What is your first measure to improve the patient's condition? Why?NoteRefresh your knowledge about treatment of severe infections.?See PACT module on Severe infection?See PACT module on Sepsis and MODSCase 2 Screen 2You immediately discuss your findings with the surgical consultant. He is convinced that the patient can be handled in the surgical ward and that no further actions are necessary.Learning issues??Definition of ALI/ARDS??Pathogenesis of secondary ALI/ARDS??Management of secondary ALI/ARDS?Give arguments to convince him this is not the best approach for this patient?You and the surgeon decide that the patient should be transferred to the ICU for optimisation before a surgical exploration.?What are you planning to do in the ICU? Why?NoteComputed tomography examinations of the abdomen in this early period after surgery will not be of benefit for the diagnosis and will only delay the definitive treatment. Usually they should not be considered.The laboratory tests show a white blood cell count of 15 10?6/l, elevated CRP, Hb 90 g/l, liver function tests in the upper normal range, platelets 150 10?9/l, D-dimer slightly elevated, plasma creatinine 100??mol/l and plasma sodium and potassium in the normal range. Blood gas (on 100% O2?via a mask with a reservoir): PaO2?12 kPa, PaCO2?4.5 kPa, BE ?5, pH 7.38.Chest radiograph: see figure below (bilateral infiltrates and pleural effusion on the left side). Urine output in the last hour is 30 ml. Arterial blood pressure is 105/55 mmHg and pulse rate 115/min (after a rapid i.v. infusion of 1000 ml Ringer-solution).In the ICU a PA-catheter is introduced and shows CVP 5 mmHg, PCWP 15 mmHg and CO 8 l/min.?Considering the chest radiograph, laboratory tests and the patient's clinical condition what is your diagnosis??Should you or should you not restrict i.v. fluids in this phase of ARDS? Why?Learning issues??Fluid therapy in ARDSCase 2 Screen 3The patient is taken to surgery and found to have a generalised faecal peritonitis due to dehiscence of the anastomosis. The peritoneum is cleaned and the bowel ends are externalised (as two stomas). After surgery the patient is transferred back to the ICU intubated, mechanicallyventilated (volume control) with FiO2?1.0, PEEP 10 cm H2O, tidal volume of 700 ml (12 ml/kg), rate 20/min and I:E 1:2. The end-inspiratory plateau pressure is 45 cm H2O. The blood gas shows PaO2?7.5 kPa, PCO2?3.7 kPa, BE ?9, pH 7.45 and lactate is 5 mmol/l. Arterial blood pressure is 95/55 mmHg, pulse rate 124/min, CO 12 l/min, CVP 25 mmHg , PCWP 20 mmHg and PAP 45/25 mmHg on i.v. norepinephrine of 0.2 ?g/kg/min.During the resuscitation and surgery she had received 10 l of crystalloids, colloids and blood products. The bleeding was negligible during surgery. Urine output has been 5, 10 and 40 ml/h during the last three hours of surgery (i.e. with the abdomen open) despite the huge fluid intake and a 250 mg i.v. bolus dose of furosemide. The abdominal pressure measured via the urinary catheter is 8 mmHg. Plasma creatinine level is now 120 ?mol/l.?How can you improve oxygenation in this patient?NoteRefresh your knowledge about mechanical ventilation and ventilatory monitoring.?See PACT module on Mechanical ventilation.?Would you like to change the ventilator settings? Give reasons for your answer.Learning issues??Lung mechanics in ALI/ARDS??Ventilator therapy in ALI/ARDS??Targets for PaO2?, PCO2?and pH??Lung recruitment procedures??Prone position and adjuvant treatment??Ventilator-induced lung injuryCase 2 Screen 4In this patient the lungs are recruited by a manoeuvre consisting of three hyperinflations of 30 sec duration to? 50 cm H2O of airway pressure after which PEEP of 16 cm H2O is found to be adequate to maintain the improved oxygenation. The ventilatory mode is changed to pressure control with a plateau inspiratory airway pressure of 32 cm H2O, producing a tidal volume of 350 ml (apparatus dead space is minimised by 50 ml by removing the heat and moisture exchanger (HME) and the extension piece), the I:E-ratio is increased to 1:1 and the ventilator rate is reduced to 20/min. FiO2?can be decreased to 0.55. After the change, PaO2?is 9 kPa, PCO2?6 kPa and pH 7.3.?Is there any indication for continuous renal replacement therapy (CRRT)? Explain why.NoteRefresh your knowledge about treatment of acute renal failure.?See PACT module on Acute renal failure?See PACT module on Oliguria and anuria.In this patient CRRT is initiated but is stopped after three days. Her condition including lung function improves rapidly and after a week she is extubated. After four months she is operated uneventfully with a reanastomosis of the bowel and is discharged home after one week in good condition.?On reflection?What are your conclusions regarding the management priorities of secondary ARDS?Q1. Regarding ventilation in ALI/ARDSTop of FormA. All patients with ARDS should be intubated.TrueFalseB. Auscultation of the chest and upper abdomen is the best method to verify a correct position of an endotracheal tube.TrueFalseC. PaCO2?should be kept high (>7 kPa) in all patients with ALI/ARDS.TrueFalseD. Lung collapse after discontinuation of PEEP could occur within seconds in ARDS.TrueFalseCheck your answers before moving to the next question?Q1. Regarding ventilation in ALI/ARDSTop of Form?Your answersA. All patients with ARDS should be intubated.The correct answer is?:?False? ?B. Auscultation of the chest and upper abdomen is the best method to verify a correct position of an endotracheal tube.The correct answer is?:?False?-?Verification should be performed by end-tidal CO2 fraction measurement.?C. PaCO2?should be kept high (>7 kPa) in all patients with ALI/ARDS.The correct answer is?:?False?-?Although a high PaCO2 might be beneficial it is still regarded as a side-effect of low tidal volume ventilation.?D. Lung collapse after discontinuation of PEEP could occur within seconds in ARDS.The correct answer is?:?True? ?Your total score is 0/4Q2. Regarding complications in Acute Respiratory FailureTop of FormA. Air under the diaphragm on a chest radiogram is always due to other reasons (e.g. recent abdominal surgery) than pulmonary barotrauma.TrueFalseB. Ventilation with large tidal volumes (12 ml/kg) is associated with an increased mortality in ALI/ARDS compared with small tidal volumes (6 ml/kg).TrueFalseC. Nosocomial infections in ARDS patients are common.TrueFalseD. VAP does not influence the length of ventilator therapy or outcome in ARDS.TrueFalseCheck your answers before moving to the next question?Q2. Regarding complications in Acute Respiratory FailureTop of Form?Your answersA. Air under the diaphragm on a chest radiogram is always due to other reasons (e.g. recent abdominal surgery) than pulmonary barotrauma.The correct answer is?:?False? ?B. Ventilation with large tidal volumes (12 ml/kg) is associated with an increased mortality in ALI/ARDS compared with small tidal volumes (6 ml/kg).The correct answer is?:?True? ?C. Nosocomial infections in ARDS patients are common.The correct answer is?:?True? ?D. VAP does not influence the length of ventilator therapy or outcome in ARDS.The correct answer is?:?False?-?Ventilator associated pneumonia increases mortality and the length of stay?Your total score is 0/4Q3. Adjuvant therapy in ARDSTop of FormA. A trial of prone positioning is mandatory in all patients with persistent hypoxia after optimization of ventilatory settingsTrueFalseB. In severe ARDS e.g. with refractory air-leak, there is evidence that referral to an ECMO centre may be beneficialTrueFalseC. Steroids have no proven beneficial effects in early ARDSTrueFalseD. Inhaled nitric oxide or inhaled prostacyclin are shown to improve outcome in ARDSTrueFalseCheck your answers before moving to the next question?Q3. Adjuvant therapy in ARDSTop of Form?Your answersA. A trial of prone positioning is mandatory in all patients with persistent hypoxia after optimization of ventilatory settingsThe correct answer is?:?False?-?Even if oxygenation increases in more than 60% of patients there might be contraindications for prone position, e.g. intracranial hypertension, unstable fractures, facial fractures and skin lesions in areas exposed to pressure when positioned prone.?B. In severe ARDS e.g. with refractory air-leak, there is evidence that referral to an ECMO centre may be beneficialThe correct answer is?:?True?-?Peek GJ, Mugford M, Tiruvoipati R, Wilson A, Allen E, Thalanany MM, et al: for the CESAR trial collaboration. Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial. Lancet 2009; 374(9698): 1351-1363.? PMID 19762075?C. Steroids have no proven beneficial effects in early ARDSThe correct answer is?:?True? ?D. Inhaled nitric oxide or inhaled prostacyclin are shown to improve outcome in ARDSThe correct answer is?:?False?-?Even if both may improve gas-exchange there is no beneficial effect on outcome with inhaled nitric oxide and there is no outcome data with inhaled prostacyclin?Your total score is 0/4Respiratory failure Type A Q4Top of FormRegarding identification, categorising and monitoring of ARF, which of the following is trueA.B.C.D.E.A??? Improving lung function is always the highest priority when treating patients with ARF?B??? Hypoxaemia is the most important cause of death in ARF?C??? ALI/ARDS is an inflammatory condition in the lungs?D??? The scores obtained from the lung injury severity score (LISS) are related to outcome?E??? The PaO2/FiO2 ratio is only dependent on the lung pathology and is not influenced by lung recruitment manoeuvres or PEEPCheck your answers before moving to the next question?Respiratory failure Type A Q4Top of Form?Your answersRegarding identification, categorising and monitoring of ARF, which of the following is trueA??? Improving lung function is always the highest priority when treating patients with ARF?B??? Hypoxaemia is the most important cause of death in ARF?C??? ALI/ARDS is an inflammatory condition in the lungs?D??? The scores obtained from the lung injury severity score (LISS) are related to outcome?E??? The PaO2/FiO2 ratio is only dependent on the lung pathology and is not influenced by lung recruitment manoeuvres or PEEPThe correct answer is?:?C.? ?Your total score is 0/1Respiratory failure Type A Q5Top of FormRegarding lung recruitment manoeuvres and PEEP in ARF, which of the following is correct?A.B.C.D.E.A. Lung recruitment manoeuvres are often more effective in late than in early ARDS?B. Lung recruitment manoeuvres using airway peak pressures of 40 cm H2O or less do usually improve PaO2 in patients with elevated intra-abdominal pressure?C. High level of PEEP should always be used in severe ARDS?D. The main pulmonary effect of PEEP is prevention of lung collapse?E. Lung recruitment manoeuvres can be done safely in hypoxaemic patients in shock.Check your answers before moving to the next question?Bottom of FormRespiratory failure Type A Q5Top of Form?Your answersRegarding lung recruitment manoeuvres and PEEP in ARF, which of the following is correct?A. Lung recruitment manoeuvres are often more effective in late than in early ARDS?B. Lung recruitment manoeuvres using airway peak pressures of 40 cm H2O or less do usually improve PaO2 in patients with elevated intra-abdominal pressure?C. High level of PEEP should always be used in severe ARDS?D. The main pulmonary effect of PEEP is prevention of lung collapse?E. Lung recruitment manoeuvres can be done safely in hypoxaemic patients in shock.The correct answer is?:?D.? ?Your total score is 0/1Respiratory failure Type A Q6Top of FormRegarding supportive measures in Acute Respiratory Failure, the following are true EXCEPTA.B.C.D.E.A??? ARDS is associated with an increased resting energy expenditure and wasting of proteins?B??? Prone positioning improves oxygenation but not outcome in ARDS?C??? Although administration of high doses of corticosteroids are not mandatory, early in the ARDS process, there are indications for this therapy in some patients with ARDS?D??? Systematic reviews have shown that ketoconazole, surfactant and N-acetylcysteine increase survival in ARDS?E??? Fluid restriction may improve oxygenation in ARDSCheck your answers before moving to the next question?Respiratory failure Type A Q6Top of Form?Your answersRegarding supportive measures in Acute Respiratory Failure, the following are true EXCEPTA??? ARDS is associated with an increased resting energy expenditure and wasting of proteins?B??? Prone positioning improves oxygenation but not outcome in ARDS?C??? Although administration of high doses of corticosteroids are not mandatory, early in the ARDS process, there are indications for this therapy in some patients with ARDS?D??? Systematic reviews have shown that ketoconazole, surfactant and N-acetylcysteine increase survival in ARDS?E??? Fluid restriction may improve oxygenation in ARDSThe correct answer is?:?D.? ?Your total score is 0/1Respiratory failure Type A Q7Top of FormRegarding the aetiology and outcome in ALI/ARDS, which of the following is trueA.B.C.D.E.A??? The scores obtained from LISS (Murray) correlate well with outcome?B??? An increased dead space fraction in early ARDS is not associated with increased mortality?C??? An important underlying cause of ARDS is pneumonia?D??? The patient may have ARDS without any inflammatory process in the lungs?E??? A chest radiograph is not mandatory for the diagnosis of ARDSCheck your answers before moving to the next question?Respiratory failure Type A Q7Top of Form?Your answersRegarding the aetiology and outcome in ALI/ARDS, which of the following is trueA??? The scores obtained from LISS (Murray) correlate well with outcome?B??? An increased dead space fraction in early ARDS is not associated with increased mortality?C??? An important underlying cause of ARDS is pneumonia?D??? The patient may have ARDS without any inflammatory process in the lungs?E??? A chest radiograph is not mandatory for the diagnosis of ARDSThe correct answer is?:?C.? ?Your total score is 0/1Respiratory failure Type A Q8Top of FormWhich of the following is true of ventilatory treatment in ALI/ARDSA.B.C.D.E.A??? Non-invasive ventilation should always be the primary ventilatory therapeutic measure in ARDS?B??? The generally accepted goals with ventilator treatment are to maintain PaO2? 10-11 kPa and PaCO2 4-5 kPa?C??? Lung recruitment manoeuvres have been shown to improve outcome in ARDS?D??? A lung recruitment manoeuvre can be performed safely in patients with severe hypovolaemia?E??? A major effect of PEEP is prevention of de- recruitment of lung regionsCheck your answers before moving to the next question?Respiratory failure Type A Q8Top of Form?Your answersWhich of the following is true of ventilatory treatment in ALI/ARDSA??? Non-invasive ventilation should always be the primary ventilatory therapeutic measure in ARDS?B??? The generally accepted goals with ventilator treatment are to maintain PaO2? 10-11 kPa and PaCO2 4-5 kPa?C??? Lung recruitment manoeuvres have been shown to improve outcome in ARDS?D??? A lung recruitment manoeuvre can be performed safely in patients with severe hypovolaemia?E??? A major effect of PEEP is prevention of de- recruitment of lung regionsThe correct answer is?:?E.? ?Your total score is 0/1Respiratory failure Type A Q9Top of FormRegarding ventilatory treatment in ALI/ARDS, the following are true EXCEPTA.B.C.D.E.A??? Continuous monitoring of? airway pressures and tidal volumes during ventilator treatment is mandatory in ARDS?B??? High end-inspiratory airway pressures (> 40 cmH2O) and large tidal volumes (>12 ml/kg) should preferentially be used in ARDS?C??? Modes that allow for spontaneous breathing have been shown to be beneficial in ARDS?D??? Inverse ratio ventilation usually improves CO2-removal in ARDS?E??? A method to increase CO2-removal is to decrease apparatus dead spaceCheck your answers before moving to the next question?Respiratory failure Type A Q9Top of Form?Your answersRegarding ventilatory treatment in ALI/ARDS, the following are true EXCEPTA??? Continuous monitoring of? airway pressures and tidal volumes during ventilator treatment is mandatory in ARDS?B??? High end-inspiratory airway pressures (> 40 cmH2O) and large tidal volumes (>12 ml/kg) should preferentially be used in ARDS?C??? Modes that allow for spontaneous breathing have been shown to be beneficial in ARDS?D??? Inverse ratio ventilation usually improves CO2-removal in ARDS?E??? A method to increase CO2-removal is to decrease apparatus dead spaceThe correct answer is?:?B.? ?Your total score is 0/1Respiratory failure Type A Q10Top of FormRegarding the complications in ALI/ARDS, the following are true EXCEPTA.B.C.D.E.A??? The impairment in cardiovascular function, sometimes found after PEEP-application,? is pronounced in hypovolaemia?B??? Anterior pneumothorax is easily recognised on a frontal chest radiogram?C??? Over-distension and tidal closing and opening of lung units are probable mechanisms for development of ventilator-associated lung injury?D??? PEEP may prevent tidal opening and closing of lung units?E??? A critically? important measure in ARDS management is treatment of the underlying conditionCheck your answers before moving to the next question?Respiratory failure Type A Q10Top of Form?Your answersRegarding the complications in ALI/ARDS, the following are true EXCEPTA??? The impairment in cardiovascular function, sometimes found after PEEP-application,? is pronounced in hypovolaemia?B??? Anterior pneumothorax is easily recognised on a frontal chest radiogram?C??? Over-distension and tidal closing and opening of lung units are probable mechanisms for development of ventilator-associated lung injury?D??? PEEP may prevent tidal opening and closing of lung units?E??? A critically? important measure in ARDS management is treatment of the underlying conditionThe correct answer is?:?B.? ?Your total score is 0/1Bottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of FormBottom of Form?? ................
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