Ventilatory failure acute

The term analeptics refers to convulsants and respiratory stimulants (i.e. central nervous system stimulants). They comprise a reverse group of agents (for example amphifrnazole and doxapram (respiratory stimulants) and strychnine, biculline and picrotoxin). Analeptics are mainly experimental drugs. Only amphifrnazole and doxapram are occasionally used for the treatment of acute ventilatory failure. 

In order to effectively treat respiratory acidosis, the causative process must be identified and treated. If a cause is identified, specific therapy should be started. This may include naloxone for opiate-induced hypoventilation or bronchodilator therapy for acute bronchospasm. Because respiratory acidosis represents ventilatory failure, an increase in... 

Respiratory stimulants have a much reduced role in the management acute ventilatory failure, with the ready availability of mechanical methods for assisting respiration. Situations where they may still be encountered are ... 

Respiratory failure may be classified as hypoxemic (type 1) or hypercapnic (type II or ventilatory failure) (3), either of which may be acute and chronic. Hypoxemic respiratory failure is due to failure of the lungs, caused by acute (cardiogenic pulmonary edema, pneumonia, acute respiratory distress syndrome) or chronic (emphysema, interstitial limg disorders) diseases (Tables 1 and 2). It is characterized by hypoxemia with normocapnia or hypocapnia. In these conditions central respiratory drive is high and there is sufficient alveolar ventilation (VA) to eliminate CO2 and prevent hypercapnia. 

Quinnell TG, Pilsworth S, Shneerson JM, et al. Prolonged invasive ventilation following acute ventilatory failure in COPD weaning results, survival and the role of noninvasive ventilation. Chest 2006 129(1) 133-139. 

Figure 1 Rate of use of three different noninvasive interfaces (oro-nasal mask, nasal mask, nasal pillows), as reported by the studies where noninvasive ventilation was utilized to treat acute left) and chronic (right) patients. The oro-nasal mask is the interface of choice in patients with acute or acute on chronic ventilatory failure, while it is less commonly employed for domiciliary treatment of stable chrcniic ventilatory failure. The nasal mask is preferred for long-term treatment of chronic patients. Source From Refs. 39 and 40.

The use of MI-E has been demonstrated to be very important in extubating NMD patients following general anesthesia, despite their lack of any breathing tolerance, and managing them with NIV (8,9,60). It is also permitted to avoid intubation or to quickly extubate NMD patients in acute ventilatory failure with no breathing tolerance and profuse airway secretions due to intercurrent chest infections (37,83,84). MI-E in a protocol with manually assisted coughing, oximetry feedback, and home use of noninvasive intermittent positive pressure ventilation was shown to effectively decrease hospitalizations and respiratory complications, and mortality for patients with NMD (7,85). 

Many patients with NMD develop CO2 narcosis with supplemental oxygen. Hypoventilation is often first recognized during a respiratory infection when bronchial mucus plugging triggers acute respiratory failure. Ventilatory failure can also develop suddenly or over a period of hours or days in patients with acute cervical myelopathies, Guillain-Barre syndrome, myasthenia gravis, acute poliomyelitis, or exacerbations of multiple sclerosis. 

Noninvasive positive-pressure ventilation (NPPV) provides ventilatory support with oxygen and pressurized airflow using a face or nasal mask with a tight seal but without endotracheal intubation. In patients with acute respiratory failure due to COPD exacerbations, NPPV was associated with lower mortality, lower intubation rates, shorter hospital stays, and greater improvements in serum pH in 1 hour compared with usual care. Use of NPPV reduces the complications that often arise with invasive mechanical ventilation. NPPV is not appropriate for patients with altered mental status, severe acidosis, respiratory arrest, or cardiovascular instability. 

A 36-year-old HIV-infected woman who had been receiving stavudine, saquinavir, ritonavir, and didanosine developed lactic acidosis (serum lactate 11.4 mmol/1) and hepatomegaly. She had acute pancreatitis and, despite ventilatory support for respiratory failure, died after 8 weeks. 

Hypercapnic respiratory failure is due to failure of the ventilatory pump caused by acute (drug overdose, acute neuromuscular diseases) or chronic (chest wall abnormalities, chronic neuromuscular diseases) disorders. It is characterized by alveolar hypoventilation, which leads to hypercapnia with coexistent, usually mild, hypoxemia. The central drive may be globally reduced with the fall in Pa02 resulting from the increase in alveolar CO2. More commonly, the drive remains high, but the mechanical load on the respiratory systan is too great or the capacity of the muscles too low to ensure efficient CO2 elimination (Fig. 1). 

Figure 6 Ventilatory management in OHS and ARF. Abbreviations OHS, obesity hypoventilation syndrome ARF, acute respiratory failure. Source From Ref. 47.

Ventilatory impairment results from inspiratory muscle weakness, central hypoventilation, thoracic restriction, upper airway narrowing, extreme obesity, abdominal distension, and improperly fitting thoracolumbar orthoses. In NMD, pulmonary infiltrates and respiratory failure are precipitated by mucus plugging due to an ineffective secretion clearance, especially during acute respiratory infections (2,7). 

As our population continues to grow, more and more patients are becoming dependent on longterm ventilatory support. Therefore, the need for quality options such as home mechanical ventilation is fast becoming a necessity. Ventilatory Support for Chronic Respiratory Failure (CRF) is the first resource to authoritatively address the needs of the acute or chronic respiratory patient through the transition from the hospital to the home-care setting. This reference covers best practices in the management of CRF patients who are ... 

Meanwhile, years of productive research have demonstrated that patients with chronic respiratory insufficiency can also benefit from mechanical ventilation. As the Preface of this volume mentions their survival as well as their health status may be dependent on long-term ventilatory support. The ever increasing incidence and prevalence of chronic respiratory disease suggests that the use of ventilatory support will markedly increase. However, the techniques and strategies to use it, and when and where (non-intensive care unit, or home), are very different from treating the respiratory failure resulting from acute conditions and in patients with structurally near normal lungs. 

---