Airway management and artificial ventilation in intensive care Reto Stockera and Peter Birob Purpose of review Abbreviations This article defines the indication for airway-securing A/CV assist-control ventilation measures and describes the actual state of knowledge ARDS acute respiratory distress syndrome BIPAP bilevel positive airway pressure about the available techniques. Various modes of ventilation CMV controlled mandatory ventilation and their rationale are presented. COPD chronic obstructive pulmonary disease CPAP continuous positive airway pressure Recent findings FPPS flow-proportional pressure support New techniques in airway management and ventilation ICU intensive-care unit LMA laryngeal mask airway strategy are presented, explained and evaluated. NIV non-invasive ventilation Summary PAV proportional-assist ventilation PCV pressure-controlled ventilation Respiratory failure is a major confounding factor of PEEP positive end-expiratory pressure morbidity and mortality in critical care patients and PEEPe extrinsic positive end-expiratory pressure PEEPi intrinsic positive end-expiratory pressure contributes considerably to prolonged intensive-care unit PSV pressure support ventilation stay. When respiratory impairment is acute, rapid SIMV synchronized intermittent mandatory ventilation VCV volume-controlled ventilation assessment of essential respiratory functions such as VPPS volume-proportional pressure support airway patency, gas exchange, and cough function have the highest priority in patients in life-threatening conditions. # 2005 Lippincott Williams & Wilkins Securing the airway is a basic and vital procedure that has 0952-7907 to be applied either in an elective or an emergency situation. Various levels of difficulty in laryngoscopy, intubation and maintaining oxygenation can occur and require Introduction standardized protocols, an adequate level of expertise and In critical care, artificial respiration is both a necessity and appropriate equipment. In intubated patients as well as in an efficient tool in the treatment of patients. Therefore it patients without secured airway, ventilatory assistance of is essential to be updated with the newest achievements various degrees and invasivities may be required. In this in the management of the airway and ventilation tech- article all clinically applied forms of ventilation, their nology and the strategies employed. When respiratory advantages and disadvantages as well as the relevant impairment is present, rapid securing of the airway has to settings are extensively presented and discussed. be applied immediately. Various levels of difficulty in laryngoscopy, intubation and maintaining oxygenation Keywords can occur and require standardized protocols, an ade- airway management, artificial ventilation, endotracheal quate level of expertise and appropriate equipment. In intubation, intensive care, ventilation modes, weaning intubated as well as in patients without secured airway, ventilatory assistance of various degree and invasivity Curr Opin Anaesthesiol 18:35–45. # 2005 Lippincott Williams & Wilkins. may be required. The newest techniques in airway management and ventilation strategy are presented, aDivision of Intensive Care, University Hospital Zu¨rich, Switzerland and bInstitute of Anaesthesiology, University Hospital Zu¨rich, Switzerland explained and evaluated. Correspondence to Peter Biro, MD, Institute of Anaesthesiology, University Hospital Zu¨rich, Raemistr. 100, CH-8091 Zu¨rich, Switzerland Airway management in intensive care Tel: +41 1 255 11 11; fax: +41 1 255 44 09; e-mail: [email protected] In critical care patients, assessment of respiratory functions Current Opinion in Anaesthesiology 2005, 18:35–45 such as airway patency, gas exchange, and cough assume the highest priority in patients with life-threatening con- ditions. Initiation of therapy must always proceed rapidly when tissue oxygen delivery is threatened. The indica- tions for endotracheal intubation can be summarized in four categories: (1) acute airway obstruction; (2) loss of protective reflexes; (3) excessive pulmonary secretions; and (4) respiratory failure [1]. Respiratory failure is either caused by failure to ventilate leading to increased arterial carbon dioxide tension (PaCO2), or failure to oxygenate, leading to a decrease in arterial oxygen tension (PaO2). Failure to oxygenate results from a decreased alveolar 35 36 Thoracic anaesthesia oxygen tension, reduced O2 diffusion capacity or a ventila- occurs rapidly, usually there is a lack of equipment at the tion perfusion mismatch. The objectives of mechanical affected site. During the time taken to prepare the ventilation are primarily to decrease the work of breathing necessary equipment and anaesthetic drugs, at least and reverse life-threatening hypoxemia or acute progres- one trained person, who stays behind the patient’s head, sive respiratory acidosis. Consequently the major indica- must apply the above-mentioned airway manoeuvre tions for mechanical ventilation are therefore acute and eventually also ventilate the patient with a face-mask respiratory failure (66%) (including acute respiratory dis- and bag-valve device until the intubation can be com- tress syndrome [ARDS], heart failure, pneumonia, sepsis, menced. The use of bag-valve devices with a reservoir is complications of surgery, and trauma) coma (15%), acute strongly emphasized, since only this type enables the exacerbation of chronic obstructive pulmonary disease delivery of a higher oxygen concentration for a patient (13%), and neuromuscular disorders (5%) [2]. who may have previously acquired a considerable oxygen debt. Pre-intubation evaluation Even in the most urgent situation, a rapid assessment of Airway adjuncts the airway anatomy can decrease the likelihood of com- In order to facilitate the performance of airway opening, plications and enable the most useful measures to be either an oro-pharyngeal tube (of the Guedel type) or a taken. Examination of the oral cavity is mandatory. Mal- naso-pharyngeal tube (of the Wendl type) may be intro- lampati and associates [3] developed a test to predict duced. Both help considerably to keep an open route difficult tracheal intubation which is easy to apply in through the hypophyarynx [10,11]. The Wendl tube may conscious patients, but which is characterized by a limited have certain advantages in patients with still prevailing sensitivity of 56% and specificity of 81% [4]. In conscious defence reflexes, while the Guedel tube is easier to insert patients, difficulties in intubation can also be anticipated if in patients with a deeper state of unconsciousness, in the patient is an adult and cannot open the mouth more which it definitely improves the patency of the face than two finger breadths, if the patient has a high arched mask. palate, or if the normal range of flexion-extension of the neck is decreased (less than 358 in both each direction) A more invasive device to secure the airway and to enable [1,3,5]. Another popular predictor is Patil’s sign, which a more effective spontaneous or assisted ventilation is the states that a thyro-mental distance of less than 6 cm is laryngeal mask airway (LMA). Although it does not associated with difficult intubation conditions [6]. These guarantee a sealing of the airway like a cuffed endotra- predictors derive from routine anaesthesiological practice, cheal tube, it maintains a wide-open route to the glottis, and cannot be transferred simply to the situation in an and is also feasible as an interface to a bag-valve device or intensive-care unit (ICU), where space andlight conditions even a respiratory system. The handling of the LMA are usually less favourable than in an operating theatre. needs a certain level of skill and experience, which is usually available only in people trained in anaesthesia Emergency airway management techniques. Nevertheless, the LMA offers a good interim Depending on the posture, the weight of the cervical solution until a definitive airway-securing technique is tissues may compress the hypopharynx and cause a partial adopted [12]. or even total obstruction of the airway. The resulting hypoventilation is often characterized by visible respira- In cases of difficulty in maintaining both oxygenation tory efforts as well as noises; in more advanced cases, the and ventilation, the Combitube may be a valuable means mechanical expenditure decreases and hypercarbia and of securing the airway and enabling oxygenation and hypoxaemia become more apparent. In such cases CO2 elimination. This device consists of two separate immediate measures to reverse the imminent suffocation lumens, of which one is always in connection with are mandatory. The so-called chin-lift or jaw-thrust man- the esophagus while the other one is connected to the oeuvre and application of oxygen, either via nasal insuf- airway. The main advantage of the Combitube is its flation or a face mask, is a very simple and effective means universal feasibility in nearly any kind of anatomical or to improve airway patency [7,8]. However, in the context functional state of the head-neck region. Its disadvan- of the prevailing cause and the neurological and respira- tage is mainly its lack of use in elective situations, which tory state of the patient, a more invasive and sustainable precludes the acquisition of a reasonable level of famil- treatment has to be adopted. In patients with suspected iarity [13]. cervical spine injuries, the jaw-thrust manoeuvre without a head-tilt is safest [9]. In cases of very