Restrictive Pulmonary Disease PDF

# Restrictive Pulmonary Disease ## Overview - Restrictive pulmonary diseases include many acute and chronic intrinsic pulmonary disorders, as well as extrinsic (extrapulmonary) disorders involving the pleura, chest wall, diaphragm, or neuromuscular function. - Respiratory gas exchange is usually...

# Restrictive Pulmonary Disease ## Overview - Restrictive pulmonary diseases include many acute and chronic intrinsic pulmonary disorders, as well as extrinsic (extrapulmonary) disorders involving the pleura, chest wall, diaphragm, or neuromuscular function. - Respiratory gas exchange is usually maintained until the disease process is advanced. ## Types of Restrictive Pulmonary Disease ### Acute Intrinsic Pulmonary Disorders - Pulmonary edema (including the acute respiratory distress syndrome [ARDS]) - Infectious pneumonia - Aspiration pneumonitis ### Chronic Intrinsic Pulmonary Disorders - Interstitial lung diseases ### Extrinsic Restrictive Pulmonary Disorders - Pleural effusions - Pneumothorax - Mediastinal masses - Kyphoscoliosis - Pectus excavatum - Neuromuscular disorders - Increased intraabdominal pressure from ascites, pregnancy, or bleeding - Marked obesity ## Restrictive Pulmonary Disease: Pathophysiology and Presentation This diagram illustrates the changes in lung volumes that occur in restrictive pulmonary disease. The normal lung is shown on the left, and the restricted lung is shown on the right. | Volume | Normal Lung | Restricted Lung | |------------------------------------|-------------|----------------| | Inspiratory Reserve Volume (IRV) | | Decreased | | Inspiratory Capacity (IC) | | Decreased | | Vital Capacity (VC) | | Decreased | | Tidal Volume (VT) | | Decreased | | Total Lung Capacity (TLC) | | Decreased | | Expiratory Reserve Volume (ERV) | | Decreased | | Functional Residual Capacity (FRC) | | Decreased | | Residual Volume (RV) | | Decreased | ### Clinical Features - **Dyspnea on exertion** - Sometimes a nonproductive cough. - Symptoms of cor pulmonale are present only with advanced disease. ### Diagnostic Tests - **Spirometry** - FEV1/FVC is normal or increased. - FEV1, FVC is decreased. - **FV Loop** - Witch's hat pattern - **Lung Volumes** - TLC and RV are decreased. - **Lung compliance** - Decreased - **DLCO** - Decreased ### Chest Radiograph - Progresses from a "ground-glass" appearance to prominent reticulonodular markings, and, finally, to a "honeycomb" appearance. ### Arterial Blood Gases - Mild hypoxemia with normocarbia. ### PFTs - Typical of a restrictive ventilatory defect. ## Management - **Acute Intrinsic Pulmonary Disorders:** - Patients with acute pulmonary disease should be postponed for elective surgery. - In preparation for emergency procedures, oxygenation and ventilation should be optimized preoperatively to the greatest extent possible. - Fluid overload should be treated with diuretics; heart failure may also require vasodilators and inotropes. - Drainage of large pleural effusions should be considered. - Massive abdominal distention should be relieved by nasogastric compression or drainage of ascites. - Persistent hypoxemia may require mechanical ventilation. - Anesthesia is most often provided with a combination of intravenous and inhalation agents, together with a neuromuscular blocking agent. - The decreased lung compliance results in high peak inspiratory pressures during positive-pressure ventilation and increases the risk of barotrauma and volutrauma. - **Ventilator strategy:** - Tidal volume: 4-6 mL/kg - Respiratory rate: 14–18 breaths/min - Airway pressure: not exceed 30 cm H2O - PEEP: High may be needed but with caution - FiO2: High - The ventilator on the anesthesia machine may prove inadequate for patients with severe ARDS due to limited gas flow capabilities, low pressure-limiting settings, and the absence of certain ventilatory modes. - **Airway pressure release ventilation (APRV):** - May improve oxygenation in the ARDS patient. - APRV is a novel ventilatory mode, and the literature supports its superiority to conventional modes of ventilation due to its ability to reduce peak airway pressure without compromising oxygenation. - During APRV, a high continuous positive airway pressure is delivered for a long duration and then falls to a lower pressure for a shorter duration. - Alveolar recruitment is increased by the high continuous positive airway pressure. - APRV offers advantages by promoting alveolar recruitment and improving oxygenation at lower peak airway pressures. - It allows for a slight elevation in mean airway pressures to overcome closing forces and recruit previously non-aerated, dependent lung units. - This mode allows for spontaneous breathing and improves V/Q matching and oxygenation in severe ARDS. - It allows for less sedation, improved cardiopulmonary function, and decreased time on ventilatory support. - Findings are not universal, however, and mortality has yet to be shown to improve with this mode of ventilation. - **Chronic Intrinsic Pulmonary Disorders:** - Chronic intrinsic pulmonary disorders are referred to as interstitial lung diseases. - Causes include hypersensitivity pneumonitis from occupational and environmental pollutants, drug toxicity (bleomycin and nitrofurantoin), radiation pneumonitis, idiopathic pulmonary fibrosis, autoimmune diseases, and sarcoidosis. Chronic pulmonary aspiration, oxygen toxicity, and severe ARDS can also produce chronic fibrosis. - Regardless of etiology, the disease process is generally characterized by an insidious onset, chronic inflammation of alveolar walls and perialveolar tissue, and progressive pulmonary fibrosis. - **Treatment:** - Directed at abating the disease process and preventing further exposure to the causative agent (if known). - Glucocorticoid and immunosuppressive therapy may be used for idiopathic pulmonary fibrosis, autoimmune disorders, and sarcoidosis. - If the patient has chronic hypoxemia, oxygen therapy may be started to prevent, or attenuate, right ventricular failure. - **Anesthetic considerations:** - The management of these patients is complicated by a predisposition to hypoxemia and the need to control ventilation to ensure optimum gas exchange. - The reduction in FRC (and oxygen stores) predisposes these patients to rapid hypoxemia following induction of anesthesia. - Anesthetic drug selection is generally not critical. - The inspired fractional concentration of oxygen (FiO2) should be kept to the minimum concentration compatible with acceptable oxygenation (Spo2 of > 88% - 92%). - Because these patients may be more susceptible to oxygen-induced toxicity, particularly patients who have received bleomycin. - **Ventilator strategy:** - I:E ratio: 1:1 (or even an inverse ratio ventilation) - RR: (10-15 breaths/ minute) - The above selected settings may help to maximize the inspiratory time per tidal volume and minimize the peak and plateau ventilatory pressures. - High peak inspiratory pressures during mechanical ventilation increase the risk of pneumothorax and should prompt adjustment of the ventilatory parameters. - **Extrinsic Restrictive Pulmonary Disorders:** - Extrinsic restrictive pulmonary disorders alter gas exchange by interfering with normal lung expansion. - They include pleural effusions, pneumothorax, mediastinal masses, kyphoscoliosis, pectus excavatum, neuromuscular disorders, and increased intraabdominal pressure from ascites, pregnancy, or bleeding. Marked obesity also produces a restrictive ventilatory defect. - **Anesthetic considerations** are similar to those discussed for intrinsic restrictive disorders. - **Types of V/Q Mismatch:** - Shunt is the primary mechanism of hypoxemia seen in: Atelectasis, Pulmonary edema, ARDS, Pneumonia. - V/Q mismatch is seen in COPD, shunt is not seen in COPD without coexistent complications such as Atelectasis, Pulmonary edema, ARDS, Pneumonia. - **Types of V/Q mismatch:** - **Low (Shunt Like)** - **High (Dead Space Like)**