Assessment of respiratory distress in the mechanically ventilated patient
- David A Kaufman, MD
David A Kaufman, MD
- Assistant Clinical Professor
- Section of Pulmonary and Critical Care Medicine
- Yale University School of Medicine
- Barry Fuchs, MD
Barry Fuchs, MD
- Associate Professor of Medicine
- University of Pennsylvania School of Medicine
- Gregg Lipschik, MD
Gregg Lipschik, MD
- Clinical Associate Professor of Medicine
- University of Pennsylvania School of Medicine
Patients undergoing mechanical ventilation frequently develop respiratory distress, often referred to as "bucking" or "fighting" the ventilator [1-4]. The term used in the medical literature for this observation is patient-ventilator asynchrony or dyssynchrony. Clinical signs include anxiety, agitation, tachypnea, tachycardia, use of accessory muscles of breathing, uncoordinated thoracic wall or abdominal movement, and asynchrony with the ventilator . Because respiratory distress may signify the onset of a life-threatening complication, a rapid, focused evaluation is required (figure 1).
Respiratory distress that occurs soon after the initiation (or reestablishment) of mechanical ventilation is often the result of inadequate ventilator support or insufficient sedation. Errors in setting the ventilator are common, and also should be considered if respiratory distress occurs during procedures or patient transport . Respiratory distress can often be managed by observing the patient's breathing pattern, and changing the ventilator settings to match respiratory rate, triggering efforts, and requirements for peak inspiratory flow (see "Overview of mechanical ventilation"). Prospective data suggest that adjusting the ventilator is more effective than sedation at reducing breath-stacking, a common and potentially hazardous form of dyssynchrony, than increasing sedation and analgesia . Detecting and effectively treating dyssynchrony to improve patient-ventilator interaction is an important skill for clinicians who care for ventilated patients, since dyssynchrony is associated with respiratory muscle fatigue and a longer duration of mechanical ventilation .
The differential diagnosis and evaluation of respiratory distress in a previously stable patient receiving mechanical ventilation will be reviewed here. The acute respiratory distress syndrome (ARDS) is discussed separately. (See "Acute respiratory distress syndrome: Clinical features and diagnosis in adults" and "Acute respiratory distress syndrome: Epidemiology, pathophysiology, pathology, and etiology in adults" and "Mechanical ventilation of adults in acute respiratory distress syndrome".)
Respiratory distress in mechanically ventilated patients can be classified anatomically as originating in the airway, the pulmonary parenchyma, or outside the lungs. Common causes include endotracheal tube obstruction, heart failure, pneumonia, patient-ventilator asynchrony due to inadequate sedation, and compression of the lungs by pleural fluid or ascites (table 1).
Airway — The artificial airway is composed of the endotracheal tube (ETT) and, in many cases, a heat and moisture exchanger (HME). The artificial airway is an important cause of respiratory distress. As an example, the HME may become saturated with secretions, leading to increased airway resistance [9-12].
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