Moderate and deep sedation represent the middle range of a spectrum of anesthetic depths that include light sedation (or anxiolysis), moderate sedation (or conscious sedation), deep sedation and general anesthesia (see Table 6.3). The differences in the sedation depth are evident by the difference in the way that patients respond to stimuli. Under moderate sedation, for example, patients demonstrate preserved protective airway reflexes. Also under moderate sedation, patients show appropriate responses to verbal or light tactile stimulation. Under deep sedation on the other hand, the patient may lose the protective airway reflexes and may not respond to verbal or light tactile stimuli. Patients under deep sedation may respond to repeated or painful stimuli. The choice to use either moderate or deep sedation techniques depends on the procedure planned, the experience of the pulmonologist, the experience of the sedation nurse or anesthetist, and the patient’s comorbidities and concerns.

Studies that look at whether sedation techniques can improve bronchoscopic procedures are conflicting. Some studies show that moderate sedation can improve the patient outcomes for bronchoscopic procedures. Other studies show no improvement. One study by Putinati et al. identified as much as half the serious complications as coming from unwanted effects of the sedation. From a review of the literature, one can conclude that there is no conclusive evidence to argue for the administration of one sedation technique over another. The final decision must include the consideration of the safety and comfort of the patient, the experience of the pulmonologist and the anesthetist, and the anatomic requirements of the procedure.

In the United States, the Joint Commission requires that all clinicians who administer sedation for interventional pulmonary procedures adhere to nine standards:

The presedation assessment requires a standard history and physical exam with certain information that directly relates to the safe conduct of moderate or deep sedation. This information includes:

The assessment of the airway is crucial because it helps to identify those patients in whom maneuvers to establish airway patency and to perform intubation may be difficult. These maneuvers can become necessary if the patient becomes oversedated. The Mallampati classification is one method to categorize patients who may prove difficult to intubate. To perform this examination, have the patient open his or her mouth fully and extend the tongue without phonating. The extent to which the palate and tonsils are visible determines the Mallampati classification (Fig. 6.1):

In addition to the Mallampati classification, there are several other anatomic predictors of difficult intubation and by inference, difficulty in rescue from oversedation. A receding mandible, limited mouth opening of less than 3.5 cm between the upper and lower incisors, pronounced overbite and/or an inability to prognath the jaw, a decreased thyromental or hyomental distance, a history of obstructive sleep apnea, and a history of a difficult or failed intubation. Patients who possess one or more of these anatomic predictors of a difficult intubation may benefit by having their sedation provided by an anesthesiologist.

Comorbid conditions can also influence the safety and conduct of moderate or deep sedation. A general assessment of the impact of comorbidities on operative mortality is the ASA physical status. Based on the patient’s comorbid conditions and their impact on the patient’s daily living, the ASA physical status consists of the following categories:

While a general assessment is important, consideration of the risks and potential complications resulting from specific comorbidities must also be considered. Conditions that limit the patient’s cognitive function such as stroke and dementia can make the patient more sensitive to sedative medications. Patients with severe COPD more often experience the side effects of respiratory depression and respiratory failure due to opioids and benzodiazepines, for example. Cardiac problems such as uncompensated congestive heart failure and aortic stenosis can result in hemodynamic instability following modest doses of sedative/hypnotics. Liver and kidney disease can affect the metabolism and excretion of many drugs and can result in exaggerated and prolonged effects. While a detailed discussion of the specific effects of comorbidities is beyond the scope of this chapter, the pulmonologist should respect the potential problems that such comorbidities can present.

The safe provision of moderate or deep sedation requires the equipment necessary to provide the next deeper level of sedation, namely, general anesthesia. Such rescue equipment is listed in Table 6.4. The availability, functionality, and sterility (where applicable) of the equipment should be assessed regularly, and the providers of sedation should be familiar with the location of each item.

Although essential equipment is important, the most crucial element to providing safe sedation is a vigilant and trained sedation provider. This provider, if a nurse, should have no other significant clinical duties during the procedure and should have the same level of training and privileges in providing sedation as the physician performing the interventional pulmonology procedure. Inadequate monitoring of patients has been a frequent cause of adverse events during bronchoscopy. Vital signs (heart rate, respiratory rate, blood pressure, oxygen saturation) should be recorded every 5 min along with level of consciousness and skin condition. Temperature should be documented at regular intervals. In addition, the timing and doses of individual drugs should be recorded along with the indications and effectiveness. The administration of intravenous fluids should be quantified. While the respiratory rate can be obtained through the measure of chest impedance using electrocardiogram electrodes, this author prefers the use of carbon dioxide monitors as a method to not only obtain respiratory rate but also to document the continuous production of CO₂ as well as the continuous patency of the airway (See Fig. 6.2).

Among the most difficult assessments for the provider of sedation are the adequacy of the airway and the depth of sedation. Chest movement may continue despite near total obstruction of the airway. The electrocardiogram may calculate normal respiratory rates despite absent alveolar ventilation. Observation of condensation on a face mask can occur from insufflation of the stomach. One solution to the problem of assessing the adequacy of ventilation is the use of end-tidal carbon dioxide monitors. This monitor has been shown to be nearly 100% sensitive in the detection of hypoventilation. Early detection of mild hypoventilation, on the other hand, can prevent subsequent hypoxemia. Thus, the use of carbon dioxide monitors can greatly increase the detection of hypoventilation and prevent the development of hypoxemia. In the patient undergoing moderate or deep sedation, the use of nasal cannula devices with side-port CO₂ detection can be employed with minimal discomfort to the patient and no disturbance to the proceduralist.