Quiz 9: Ventilation Support Quiz Notes

Negative-Pressure Ventilation

• Negative-pressure ventilators work by decreasing pressure around the thorax. These ventilators create a pressure gradient that facilitates air entry into the lungs. This method mimics the natural breathing process more closely compared to positive-pressure ventilation.

• This increases the transthoracic pressure gradient Ptt = Palv − Pbs, drawing air into the lungs. This pressure difference is crucial for effective ventilation without the need for invasive measures.

Acute Cardiogenic Pulmonary Edema (ACPE) and Initial Therapy

• Presentation: Pink, frothy secretions, hypoxemia, and abnormal ABG values. These symptoms indicate fluid accumulation in the lungs due to heart failure, leading to impaired gas exchange.

• Initial Therapy: Mask CPAP with supplemental oxygen. CPAP helps maintain airway pressure, preventing alveolar collapse and improving oxygenation. Supplemental oxygen addresses hypoxemia by increasing the oxygen concentration in the inspired air.

• Mechanism:

  • Recruits collapsed alveoli. By increasing alveolar pressure, CPAP helps to open collapsed alveoli, enhancing gas exchange surface area.

  • Reduces venous return (preload) and left ventricular afterload. This reduces the workload on the heart, improving cardiac function and reducing pulmonary congestion.

Acute Pulmonary Edema and Hypoxemic Respiratory Failure

• If a patient doesn't respond to conventional treatments, consider noninvasive positive-pressure ventilation (NIV). NIV provides ventilatory support without intubation, avoiding the complications associated with invasive ventilation. It is especially useful when initial therapies are insufficient.

  • PEEP improves oxygenation. PEEP increases the functional residual capacity (FRC) and prevents alveolar collapse, leading to better oxygen exchange.

  • Pressure support reduces the work of breathing. By augmenting the patient's inspiratory efforts, pressure support decreases respiratory muscle fatigue.

Physiological Goals of NIV in Acute Respiratory Failure

• Resting the respiratory muscles. Reducing the strain on respiratory muscles allows them to recover, which is vital in managing acute respiratory failure.

  • NIV reduces work of breathing and muscle fatigue, which allows for more efficient ventilation and improves gas exchange. Efficient ventilation ensures adequate oxygen delivery and carbon dioxide removal.

Primary Goal of NIV in Acute Care

• Avoid invasive ventilation (endotracheal intubation). By effectively supporting ventilation, NIV can help patients avoid the risks and discomfort associated with intubation.

• NIV reverses respiratory failure early, reducing the need for invasive mechanical ventilation. Early intervention can prevent the condition from worsening, thereby decreasing the likelihood of needing more aggressive treatments.

NIV for Chronic Hypoventilation

• Patients typically need a minimum of 4–6 hours of nightly NIV to improve quality of life. Regular use of NIV can significantly enhance sleep quality, reduce daytime fatigue, and improve overall well-being.

NIV for COPD Exacerbation

• NIV is the standard of care for COPD exacerbations. It is a first-line treatment option for managing acute breathing difficulties in COPD patients.

• It improves alveolar ventilation and corrects hypercapnia, lowering the need for intubation. Effective ventilation helps to normalize blood pH and reduces the necessity for invasive interventions.

COPD Patient in Emergency Department

• Invasive mechanical ventilation is needed for patients with severe respiratory acidosis and uncooperativeness. In such critical conditions, intubation and mechanical ventilation may be necessary to stabilize the patient.

Patient with Shortness of Breath and Pulmonary Vascular Congestion

• Mask CPAP is used to improve oxygenation. CPAP provides continuous positive airway pressure, which helps to keep the airways open and improves gas exchange.

• It also reduces preload and afterload, which is beneficial in cardiogenic pulmonary edema. By easing the workload on the heart, CPAP helps to alleviate pulmonary congestion.

Tidal Volume in Bilevel Positive-Pressure Ventilation

• The gradient between IPAP and EPAP (pressure support level) determines the delivered tidal volume. The pressure difference influences how much air is moved into the lungs with each breath.

COPD Patient with Dyspnea and Hypersomnolence

• Nocturnal NIV should be recommended to the physician to correct nocturnal hypoventilation, alleviate morning headaches and daytime hypersomnolence, and reduce hospitalizations. Addressing hypoventilation during sleep can improve overall health and reduce the need for hospital care.

ALS Patient Complaining of Fatigue

• Nocturnal NIV is used to support inspiratory effort and improve alveolar ventilation, which alleviates fatigue and cognitive impairment. Supporting breathing during sleep can enhance oxygenation and reduce the symptoms of fatigue and cognitive dysfunction.

CPAP Requirements

• Adequate spontaneous ventilation helps the patient to generate tidal volumes and benefit from alveolar recruitment. Patients need to be able to breathe on their own to some extent for CPAP to be effective in opening up the alveoli.

Pressure Support Breath Termination

• Pressure