A 52-year old woman with history of systemic lupus erythematosus (SLE) was evaluated in the emergency department (ED) for an 8 week history of progressive dyspnea on exertion, dysphonia, and dry, non-productive cough which acutely worsened in the past 24 hours. Her SLE was diagnosed 18 years prior, and is characterized by markedly positive anti-nuclear antibody titers, malar rash, and arthralgia for which she is taking azathioprine and prednisolone.
The patient describes a roughly 8 month history of orthopnea and reduced exercise tolerance. She denies a history of fever, headaches, hemoptysis, productive cough, lightheadedness, chest pain, pleurisy, palpitations, weakness, and has not had any new occupational health exposures. She is a non-smoker.
On admission to the ED, she has an oxygen saturation of 86% on room air, which increased to 97% on 6L/min of oxygen administered through face mask. She is normotensive, tachycardic with a heart rate of 108 beats per minute, tachypneic with a respiratory rate of 22 breaths per minute, with diffuse bibasilar crackles heard on chest auscultation. Electrocardiogram revealed sinus tachycardia.
Portable chest x-ray showed an elevated left hemidiaphragm. Serum laboratory evaluation, including complete blood counts, clotting profiles, cardiac enzymes, and basic metabolic panel were all within normal limits. Her serum creatinine was slightly increased at 1.2 mg/dL, which was unchanged from prior evaluation.
She underwent computed tomography with pulmonary angiogram which did not show any evidence of pulmonary emboli or fibrosis and minimal pleural thickening; however she showed markedly reduced lung volumes, bibasilar lung atelectasis, distension of the pulmonary outflow tract vessels, and elevation of the left hemidiaphragm. An echocardiogram revealed normal left ventricular size and function and mild right ventricular dilatation.
Within 6 hours of presentation to the ED, the patient’s respiratory function significantly deteriorated, with the patient exhibiting worsening dyspnea and tachypnea, oxygen saturation 86% on 100% oxygen administered via non-rebreather mask. An arterial blood gas (ABG) was drawn while patient was receiving oxygen, revealing respiratory acidosis (7.22/65/98/38/90%).
Consent was given for immediate intubation for airway protection and she was placed on synchronized intermittent-mandatory ventilation, with tidal volumes of 400 mL, respiratory rate of 14, and PEEP of 8 cm H20. Peak airway pressures were noted to drift above 40 cm H2O, and ventilation was changed to pressure controlled ventilation mode. In this mode, the patient was noted to have decreased tidal volumes between 220-300 mL, with a markedly reduced dynamic compliance. She was transferred to the medical intensive care unit for further management.