Question

Ms. X is an 87 y/o Hispanic female who presented to the ED after experiencing an episode of syncope this AM. She was getting out the bed and when she stood up felt some chest pressure and fainted. She landed on her bed and did not sustain any injuries. She has not had any prior syncopal episodes. She has chronic dizziness which has not changed and has not started any new medications. She denies nausea, vomiting, diarrhea, a history of aortic stenosis, DVT, or PE. Currently she is experiencing chest pain, which is mild in severity, constant, dull and radiate to her back between her scapula. Her past medical history is positive for: Diastolic Heart failure, HTN, CAD, hypothyroidism, hyperlipidemia, and breast cancer for which she just completed chemotherapy. Prior surgeries included a hysterectomy and bilateral cataract removal. Physical exam: Vitals: 36.3-74-16-163/74, O2 sat is 89% on room air. Normocephalic. Alert & Oriented x3. Well developed. Eyes: PERL. No nystagmus Neck: Supple, no cervical lymphadenopathy Cardiovascular: Normal Rate and rhythm. No murmur, gallops. 2+/4_ radial, brachial, dorsalis Pedis pulses bilaterally. 3+ pitting edema of lower extremities. Pulmonary: mildly dyspneic, not using accessory muscles. Lungs are clear in all lung fields. Abdomen: Soft and nontender, active bowel sounds. No peritoneal signs. Skin: warm, dry and pale. EKG: no ST or T wave changes. QTc is normal. CXR: without any acute changes, CT of Head: Negative VQ scan: V/Q ratio is 1.3. Lab Result Na+ 134 mEq/L K+ 4.1 mEq/L creatinine 0.86 mg/dL BUN 17 mg/dL Troponin T <0.01 ng/ml BNP 100 pg/ml WBC 5,000 mm3 Hct 35.6 % Hgb 12 g/dL Platelet count 240,000 Calcium 9.2 mg/dL Magnesium 2.1 mg/dL Phosphorus 4.2 mg/dL Glucose 122 mg/dL Questions The clinical scenario is most consistent with which diagnosis? You may simply list your answer below using a bullet point format. This does not have to be in a complete sentence. What data in the clinical scenario supports your diagnosis? Make sure to interpret the lab values. You may simply list your answers below using a bullet point format. This does not have to be in a complete sentence. Interpret the labs that you list as part of your answer by indicating normal, high or low. What risk factor(s) led to this person’s diagnosis? You may simply list your answer below using a bullet point format. This does not have to be in a complete sentence. Describe the key pathophysiologic concepts of the diagnosis in question 1. To answer this question completely, you must answer all of the sub-questions below using complete sentences. Each sub-question may be answered in 1-6 sentences. What is the most common etiology for the diagnosis you identified in question 1? Describe how this disorder causes hypoxia. Describe the pulmonary ventilation to perfusion balance (V/Q)? What is the normal range for the VQ ratio? What is a V/Q mismatch? What does a low V/Q ratio indicate? What does a high V/Q ratio indicate? What type of V/Q mismatch is this patient likely experiencing and why? For what actual or potential complications related to the diagnosis in question 1 does she need to be monitored? You may simply list your answer(s) below using a bullet point format. This does not have to be in a complete sentence.

Answer 1

• Diagnosis: Pulmonary embolism. The patient had chest pain radiating down the scapula, episode of syncope, dyspnea, and low O2 saturation which confirm the diagnosis of pulmonary embolism. V/Q ration was elevated at 1.3, which is also typically associated with pulmonary embolism.
• Risk factors that led to the diagnosis: History of breast cancer and recent chemotherapy.
• Pathophysiologic concepts: A pulmonary embolism occurs when an embolus, usually a blood clot, blocks the blood flowing through an artery that supplies the lungs. The blood clot might start in the arm/legs. Several cancer treatment including chemotherapy and hormone therapy could trigger a blood clot. The clot breaks free and travels through the circulatory system towards the lungs, where it is too large to pass through the small vessels, and therefore form a blockage. This blockage stops the blood from flowing into a part of the lung, causing the affected section of the lung to die through lack of oxygen.
  • Common etiology: The common etiology include alteration in the blood flow caused by immobilization (after surgery, pregnancy), obesity and cancer. Any endothelial injury caused by surgical procedures is another cause. hormonal contraception, genetic thrombophilia, acquired thrombophilia, and cancer can cause the formation of pro-coagulant state.
  • Cause of hypoxia in pulmonary embolism: In pulmonary embolism, the emboli blocks the blood from flowing into the part of the lung, causing the affected section of the lung to die through lack of O2. The pulmonary blood flow is affected and there is a perfusion defect with defect in the blood flow. Gas exchange becomes highly insufficient leading to hypoxemia.
  • Pulmonary ventilation to perfusion scan (V/Q): V/Q ratio is the ratio used to assess the efficiency and adequacy of matching the ventilation (refers to the air that reaches the alveoli) and perfusion (the blood that reaches the alveoli via the capillaries). It is the ratio of the amount of the air reaching the alveoli per minute to the amount of the blood reaching the alveoli. The two variables, V&Q constitute the main determinants of the blood O2 and CO2 concentration.
  • Normal range of VQ ratio: In an average man, the ventilation rate (V) is roughly 5l/min and the perfusion of the lung (Q) is roughly 5l/min. The ideal V/Q ratio would be 1; however, the ratio varies depending on the part of the lung. The overall value in the average human is closer to 0.8.
  • V/Q mismatch: V/Q mismatch or V/Q defects are defects in the total lung ventilation perfusion ratio. It is a condition in which one or more areas of the lung receive O2 but no blood flow or they receive blood flow but no O2 due to some disease or disorders.
  • Low V/Q ratio: The low V/Q ration indicates impaired pulmonary gas exchange causing low paO2. Excretion of CO2 is also impaired but a rise in paCO2 is very uncommon as this leads to respiratory stimulation and resultant increase in alveolar ventilation, which returns the paCO2 to the normal range. Low V/Q ratio is often associated with chronic bronchitis, asthma, and acute pulmonary edema
  • High V/Q ratio: A high ratio decreases the paO2 and paCO2. Peripheral O2 saturation is also lower than normal leading to dyspnea and tachypnea. A high V/Q ratio is often seen in pulmonary embolism and emphysema.
  • Type of V/Q mismatch for this patient: The patient has a high V/Q ratio, which means the ventilation scan is normal but the perfusion is abnormal indicating any obstruction to the blood flow. the patient has a physiological dead space mismatch, where perfusion would be affected due to impairment in the arteries.     
  • Actual or potential complications of pulmonary embolism: Recurrence of pulmonary embolism, cardiac arrest, pleural effusion, pulmonary infarction, arrhythmia, pulmonary hypertension, and abnormal bleeding