Term
|
Definition
| Adult Respiratory Distress Syndrome (ARDS) caused by damage to the respiratory (alveolar-capillary) membrane |
|
|
Term
| What is the survival rate of ARDS? |
|
Definition
| Mortality ranges from 30-63%. |
|
|
Term
| What are the signs & symptoms of ARDS? |
|
Definition
| Patients develop severe dyspnea and a decrease in arterial PO2 (and O2 sat) that does not respond to supplemental oxygen therapy |
|
|
Term
| Are there lasting effects from ARDS? |
|
Definition
| Patients who recover usually have mild restrictive lung disease (usually caused by fibrosis & and will have long term hypoxemia). Some have a decreased PO2. |
|
|
Term
| What will a chest e ray show on a person with ARDS? |
|
Definition
| CXR may be normal initially; CXR shows widespread infiltrates/whiteout |
|
|
Term
| What are the causes of ARDS? |
|
Definition
| There are many causes, including severe trauma, pneumonia, sepsis (>40% of cases), aspiration of gastric acid (>30% of cases), and shock |
|
|
Term
| What are the mechanisms of ARDS? |
|
Definition
| The exact mechanism is unknown. The damage to the respiratory membrane can be caused by direct (eg. aspiration) or indirect injury (eg. shock). The subsequent inflammatory response leads to an increase in capillary permeability. |
|
|
Term
| What results from the damaged pulmonary capillaries in a patient with ARDS? |
|
Definition
| The result is leakage of fluid and protein from the pulmonary capillaries, which causes interstitial and alveolar pulmonary edema (non-cardiogenic pulmonary edema). |
|
|
Term
| What are Common findings of ARDS? |
|
Definition
| Common findings include: 1)severe hypoxemia, 2) decreased lung compliance, and 3) a decrease in the FRC (functional residual capacity, FRC = RV + ERV). |
|
|
Term
| Why does FRC decrease in a patient with ARDS? |
|
Definition
| The FRC is decreased because the lungs are very stiff and non-compliant. The alveolar edema causes increased surface tension, which makes it more difficult to expand the alveoli. This leads to atelectasis (collapsed alveoli) and loss of lung volume. |
|
|
Term
| What is a cause of the loss of alveolar surface tension in a patient with ARDS? |
|
Definition
| There is also a loss of surfactant activity, which further increases alveolar surface tension |
|
|
Term
| What type of ventilator pressures are needed to correct the tidal volume in a patient with ARDS? |
|
Definition
| High ventilator pressures are required to deliver a normal tidal volume |
|
|
Term
| What causes the hypoxemia in ARDS? |
|
Definition
| The hypoxemia is due to: 1) decreased diffusion through the respiratory membrane, 2) the perfusion of poorly ventilated alveoli (VQ mismatch), and 3) the perfusion of non-ventilated alveoli (intrapulmonary shunting). |
|
|
Term
| When will a patient begin to present with ARDS? |
|
Definition
| The onset of respiratory failure is often 1-2 days after the initiating event and may be sudden.Dyspnea and hypoxemia progressively worsen |
|
|
Term
| How does the dyspnea respond to oxygen therapy in a patient with ARDS? |
|
Definition
| The hypoxemia does not respond to supplemental oxygen therapy, and may progress to hypotension and cardiac arrest |
|
|
Term
| What will the ABG's show? |
|
Definition
| ABG's show hypoxemia, metabolic acidosis, and elevated PCO2 |
|
|
Term
| How do you manage and treat ARDS? |
|
Definition
| Management involves treating the underlying cause, along with mechanical ventilation |
|
|
Term
|
Definition
| Positive end-expiratory pressure (PEEP) and high FIO2 (fraction of inspired oxygen) levels are often required to maintain an adequate PO2. The goal is to keep the PO2 > 60 mmHg (O2 sat 90%). PEEP involves maintaining a positive airway pressure between the end of expiration and the beginning of inspiration. It prevents alveoli from collapsing between breaths. |
|
|
Term
| Why is it important not to administer excess fluids to ARDS patients? |
|
Definition
| Avoiding excess fluid administration is important, since it tends to increase the edema (pulmonary). |
|
|
Term
|
Definition
| Infant Respiratory Distress Syndrome (IRDS); This has features similar to ARDS. |
|
|
Term
| Who typically presents with IRDS? |
|
Definition
| It primarily occurs in premature neonates. The hypoxia doesn't respond to increasing levels of supplemental oxygen |
|
|
Term
| What type of incidence rates or there of IRDS? |
|
Definition
| The incidence in neonates born at less than 30 weeks gestation is 60%. If corticosteroids are given before birth, the incidence is decreased to 35%. After 34 weeks, the incidence is 5%. |
|
|
Term
| What is the primary cause of IRDS? |
|
Definition
| The primary cause is lack of pulmonary surfactant, leading to increased alveolar surface tension and decreased compliance. Surfactant is normally produced by the type II alveolar cells beginning at about 32 weeks. |
|
|
Term
| What is the pulmonary compliance in a patient with IRDS? |
|
Definition
| In IRDS the pulmonary compliance is only 10-20% of normal |
|
|
Term
| Why is difficult for a patient with IRDS to breath? |
|
Definition
| The neonate must generate very high negative intrathoracic pressures (-25 to -35mmHg) in order to inhale. The work of breathing is significantly increased |
|
|
Term
| What takes place with the progression of IRDS? |
|
Definition
| Progressive atelectasis, increased pulmonary vascular resistance, hyopxemia, and acidosis develop. |
|
|
Term
| Why do proteins leak from the capillaries with IRDS? |
|
Definition
| Increased surface tension also increases the leakage of protein and fluid into the alveoli |
|
|
Term
| Why is there a VQ mismatch with IRDS? |
|
Definition
| Immature pulmonary capillaries also cause some degree of VQ mismatch |
|
|
Term
| What are the signs of IRDS? |
|
Definition
| Signs include rapid, shallow respirations, intercostal or sternal retractions, and decreased breath sounds. Cyanosis and expiratory grunting may be present. Exhaling against a partially closed glottis produces a grunting sound and helps to keep the alveoli open |
|
|
Term
| What do the ABG's show in an IRDS patient? |
|
Definition
| ABG's show hypoxemia and metabolic acidosis. Increased PCO2 occurs later |
|
|
Term
| What will a CXR show in a patient with IRDS? |
|
Definition
| CXR is normal at birth. Diffuse whiteout and hypoinflation appear later |
|
|
Term
|
Definition
| Management usually requires mechanical ventilation with PEEP. The goal is to maintain PO2 levels between 50 and 90 mmHg |
|
|
Term
| What should the FI02 levels be at for IRDS? |
|
Definition
| The FIO2 should be kept as low as possible. |
|
|
Term
| Can you give 100% oxygen? Why or why not? |
|
Definition
| Breathing 100% O2 for prolonged periods can cause further alveolar damage and other problems. |
|
|
Term
| What is a treatment that is used to help IRDS patients? |
|
Definition
| Surfactant can be delivered through the endotracheal tube. This decreases surface tension and decreases the negative pressure required to inflate the lungs |
|
|
