critical care medicine
Oxygen Desaturation
Evaluation of Oxygen Desaturation
Total fluid volume given during the hospital stay and, in particular, during the previous 24 hours should be ascertained to identify Volume Overload . Drugs should be reviewed for sedative administration and dosage. In significant hypoxia (oxygen saturation Very sudden onset dyspnea and hypoxia suggest Pulmonary Embolism (PE) (PE) or Patency of the airway and strength and adequacy of respirations should be assessed immediately. For patients on mechanical ventilation, it is important to determine that the endotracheal tube is not obstructed or dislodged. Findings are suggestive as follows: Unilateral decreased breath sounds with clear lung fields suggest pneumothorax or right mainstem bronchus intubation; with crackles and fever, pneumonia is more likely. Distended neck veins with bilateral lung crackles suggest volume overload with pulmonary edema, cardiogenic shock, Cardiac Tamponade (often without crackles), or acute valvular insufficiency. Distended neck veins with clear lungs or unilateral decrease in breath sounds and tracheal deviation suggest tension pneumothorax. Bilateral lower-extremity edema suggests heart failure, but unilateral edema suggests DVT and hence possible PE. Wheezing represents bronchospasm (typically asthma or allergic reaction, but it occurs rarely with PE or heart failure). Decreased mental status suggests hypoventilation. Hypoxia is generally recognized initially by pulse oximetry. Patients should have the following: A chest x-ray (eg, to assess for pneumonia, pleural effusion, pneumothorax, heart failure, or atelectasis) ECG (to assess for arrhythmia or ischemia) Arterial blood gases (ABGs), to confirm hypoxia and evaluate adequacy of ventilation Bedside echocardiography done by an intensivist may be used to assess for hemodynamically significant pericardial effusion or reduced global left ventricular or right ventricular function until formal echocardiography can be done. Bedside ultrasonography can also be done to identify pneumothorax. Elevated serum levels of brain (B-type) natriuretic peptide (BNP) may help differentiate heart failure from other causes of hypoxia. If diagnosis remains unclear after these tests, Diagnosis should be considered. Bronchoscopy may be done in intubated patients or in patients with a tracheostomy to rule out (and remove) a tracheobronchial mucous plug. 