The anatomic and physiologic changes of the cardiac (see Chap. 8) and respiratory systems explain why respiratory symptoms are common during pregnancy. The most frequent respiratory complaint is shortness of breath (dyspnea). Other symptoms include cough and hemoptysis. Unfortunately both benign and life-threatening conditions present with similar complaints. A careful evaluation of these symptoms will allow the practitioner to discern between pregnancy-related complaints and a more severe condition. Even when deemed benign, cardiorespiratory symptoms should be noted and evaluated prospectively in subsequent visits of the patient. Some of the conditions that can be suggested by history or physical examination are included in Fig. 12-3. Specific algorithms addressing the evaluation of dyspnea, cough, and hemoptysis (Figs. 12-4,12-5, 12-6) are suggested.
Evaluation of hemoptysis.
The most frequent indications for mechanical ventilation among obstetric patients admitted to an ICU are acute respiratory failure (39%) and hemodynamic failure (38%), followed by impaired consciousness (17%) and postoperative ventilation (6%).
Leading causes of acute respiratory distress syndrome (ARDS) during pregnancy are infection, preeclampsia or eclampsia, and aspiration.
The two most helpful clinical adjuncts in the evaluation of respiratory conditions during pregnancy are:
Arterial blood gas interpretation. The changes induced by the pregnant state are summarized in Table 12-4. Figures 12-1 and 12-2 illustrate the evaluation of ventilation and oxygenation through the laboratory analysis of an arterial blood sample.
Chest x-ray interpretation. Table 12-5 summarizes the changes described for pregnancy. Aside from heart enlargement secondary to hypervolemia and cardiac remodeling and some cephalad flow redistribution, all other criteria used to interpret chest radiograms remain the same as in the nonpregnant state. Figure 12-7 provides a guideline for evaluation of chest x-rays and the most common pathologic processes encountered by the site of affliction. As was the case with the arterial blood gases, more than one process may coexist and affect the patient.
Evaluation of chest x-ray.
TABLE 12-5.Changes in Chest X-Ray During Pregnancy ||Download (.pdf) TABLE 12-5. Changes in Chest X-Ray During Pregnancy
Apparent cardiomegaly (enlarged transverse diameter)
Enlarged left atrium (lateral views)
Increased vascular markings
Straightening of left heart border
Postpartum pleural effusion (right-sided)
Multiple intercurrent diseases in the pregnant woman and several conditions specific to pregnancy may compromise the processes of oxygenation or ventilation. While the specific treatment of these conditions may differ, the recognition of the need for supportive respiratory therapy and the prompt institution of adequate ventilation and oxygenation support may be the difference between life and death.