Titration Techniques

The current standard of care dictates CPAP therapy be commenced and titrated under direct supervision by a trained technician. Direct supervision allows for immediate assessment of various sleep-related disturbances, direct determination of the optimal CPAP pressure, and identification of significant sleep-related comorbidities, including but not limited to nocturnal seizures, cardiac arrhythmias, para-somnia activity, and nocturnal myoclonus. Furthermore, direct supervision allows for appropriate evaluation of persistent hypoxemia with PAP therapy in the absence of overt respiratory events, which may in turn require additional titration of supplemental oxygen. To date, there is little evidence regarding the safety and efficacy of CPAP titrations performed outside of a medically-supervised setting. In fact, current evidence suggests that patients have a greater likelihood of being compliant with therapy if initial introduction to CPAP is performed in a setting where education and support by a sleep professional are a part of the initial experience, and longitudinal support and positive reinforcement are offered as an ongoing part of patient care (87-89). Auto-titrating devices have called into question the current standard; however, current evidence does not support the use of these devices for CPAP initiation and further studies are needed.

The primary goal of the PAP titration study is three-fold: introduction of and acclimation to PAP therapy, determination of optimal mask interface type and fit, and determination of the optimal pressure that will normalize sleep-disordered breathing and correct hypoxemia. Introduction of PAP therapy is a critical step in helping towards long-term adherence. Data have suggested that patients who have difficulties on the first night of therapy have less likelihood of long-term adherence and are three times more likely to use their machines for less than four hours per night than those without first night problems (90).

Before the initiation of the PAP titration, extensive education about the pathophysiology of OSA, the consequences of untreated OSA, as well as PAP therapy should be given to the patient. Videotapes and supplemental reading are additional tools that may help patient adherence. Intensive patient education has been shown to improve the likelihood of adherence in various studies (see section: Improving Adherence) (88,89). Special care should be given by the supervising technician to ensure optimal mask fit in order to improve comfort and reduce the potential for mask leak. In some cases, a chinstrap or a full-face mask may be required to eliminate mouth breathing, which should be assessed once the titration study has begun (91). Mouth breathing has been shown to adversely effect CPAP adherence and should be addressed during the initial titration night (92).

When determining a titration algorithm, it is essential to understand that elimination of apneas, hypopneas, and oxygen desaturations is the first objective, but not the endpoint of the titration. Rather, the endpoint of the titration should be elimination of snoring and respiratory-related arousals in all positions and all stages of sleep (50,93). Persistent inspiratory airflow limitation is evidenced by a flattened airflow pressure tracing and can best be demonstrated with titrations that are performed with nasal pressure-flow transducers, as opposed to thermistors or other indirect measures of airflow (94). Although esophageal pressure monitoring is the most accurate means of assessing increased respiratory effort due to flow limitation, this modality is often poorly tolerated which may in turn limit its routine use in CPAP titration studies. When inspiratory airflow limitation is associated with spontaneous arousals, it is likely due to UARS and a further increase in airway pressure is indicated (95). An uncontrolled CPAP titration patient series has been reported, which suggests that careful monitoring of esophageal pressures, and / or CPAP airflow signals, generally demonstrates continued evidence of airflow resistance until CPAP pressures have been increased to 2 cm H2O, on average, above that needed to eliminate apneas and hypopneas (96). Surprisingly, it has been demonstrated that patients undergoing CPAP titration may display increased pressure requirements during titration from lower CPAP pressures upward, as compared to pressures required during downward titration from higher pressures (97). Accordingly, in some patients, it is appropriate during a titration study to titrate pressures upward until elimination of respiratory events has been achieved and a normal airflow pattern is attained; and then titrate downward to the return of obstructive events. This method is of particular use in patients who have difficulty tolerating PAP therapy due to high pressure requirements.

When performing a titration, it is important to note sleep stage and body position once optimal pressure is assumed as evidence that suggests that higher pressure requirements may be needed in the supine position (98) and in REM sleep (99). Once an optimal pressure has been attained, in addition to resolution of sleep-related breathing events, sleep continuity should theoretically improve, with a decrease in the number of spontaneous arousals and arousals associated with respiratory events. Commonly, slow-wave sleep rebound or REM sleep rebound will be seen with improved sleep continuity and this finding can be used as an indication that an effective pressure level is imminent (100). It has been shown that increased tidal volumes can induce central apneas in the setting of normocapnia due to neuro-chemical inhibition and possibly, baroreceptor activity (101). This finding has led to the practice of decreasing CPAP pressures when the emergence of central apneas is witnessed during an upward titration. However, it is important to continue to explore upward pressures with the appearance of central apneas, as there are several mechanisms that have been shown to elicit central apneas, including upper airway obstruction (51,52), which may be indicative of subtherapeutic pressures.

There is considerable debate regarding the use of bilevel ventilation as a strategy to improve adherence to PAP therapy in patients requiring high pressures to treat sleep-related breathing disorders. Studies using dynamic upper airway imaging have confirmed that expiratory collapse of the upper airway occurs, and does so in a more passive manner than does inspiratory airway collapse (102). This finding seems to be explained by the active, negative intraluminal pressures generated during inspiration, which are absent with the more passive expiration. As a result, it has been shown that lower expiratory pressures are required to maintain airway patency than with inspiration (103). The efficacy of using bilevel ventilation as a standard treatment modality in all patients with OSA is questionable; however, clinicians tend to consider unacceptably high CPAP pressures, as deemed by intolerance of the pressure by the patient during the study, as an indication to change to bilevel mode of ventilation. Although not studied systematically, clinicians generally feel that patients with lung disease, chest-wall disease, and/or neuromuscular disease may be most appropriate for bilevel mode of delivery of breath. There is at least one study that has suggested that bilevel PAP increases the incidence of CSA-CSR and non-CSR CSA in certain patients (104), which further reinforces the need for more studies in this area.

While CPAP therapy has been the standard of care for many years, there is a surprising lack of data validating standardized titration methods. In particular, details on the transition from CPAP therapy to bilevel therapy are lacking. In patients with OSA intolerant of CPAP, there exist primarily three different techniques employed: (i) an inspiratory pressure is chosen equal to the CPAP pressure where obstructive events were eliminated; (ii) an expiratory pressure is chosen equal to the CPAP pressure where obstructive events were eliminated; (iii) bilevel is initiated from a low starting pressure, beginning with baseline pressure settings and titrating upwards. Regardless of the technique followed, it is generally thought that a 4 to 5 cm H2O difference should be preserved in order to maintain airway patency during expiration. Commonly, expiratory pressure increases are performed in the setting of persistent or reappearing apneas, while inspiratory pressure increases are made in the setting of snoring, flow limitation, or hypopneas, maintaining a 4 cm difference between the two.

The use of BPAP in patients with OHS should be initiated in a similar fashion; however, if hypoxemia persists after resolution of respiratory events, in particular during REM sleep, the addition of supplemental oxygen in these patients is appropriate. Special consideration is needed when using BPAP in patients with CSA not responsive to CPAP, especially patients with CSA-CSR in the absence of OSA. These patients will often need a "timed mode" of inspiration as the bilevel unit will not be triggered due to lack of inspiratory effort. As previously stated, these patients are extremely difficult to treat and a definitive modality of therapy has yet to be determined. In light of this fact, ASV ventilation has been developed in the hope of creating a more effective means of treating CSA-CSR and improving adherence. ASV ventilation provides positive expiratory airway pressure and inspiratory pressure support that is servo-controlled based on the detection of CSR, with a backup respiratory rate. Initial studies show great promise for this device as means of effectively controlling CSA-CSR (65-67); however, further data are needed before this modality becomes the standard of care.

Another area of debate is the use of the "split-night" study as means to diagnose and treat OSA in a single night. This strategy has been devised in an effort to decrease the financial burden of two separate studies as well as to minimize the inconvenience to the patient. There are data to suggest that this is a reasonable approach (105), however, these nonrandomized studies were biased toward patients with more severe disease (106,107). There seem to be certain patients who are best suited for the "split-night" protocol; however, data are lacking to justify the routine use of these studies in the absence of insurance mandate or appropriate patient selection.

The use of "daytime" titrations is another method that has been proposed to derive optimal pressure settings. Again, limited efficacy and adherence data call this technique into question (105) though initial nonrandomized cohort studies do show some comparable results to overnight titrations (108,109).

Many factors may contribute to the therapeutic efficacy of PAP therapy over time. In the absence of significant clinical changes, a pressure level chosen during a single night's titration is generally effective on longitudinal nights (110). However, significant weight gain (111), heavy alcohol use (112), and nasal congestion are all factors that can alter the efficacy of CPAP therapy. If a patient who initially responded to treatment begins to complain of recurrent symptoms, consider these contributing factors as a potential cause. It is imperative for the clinician to consider all causes of "residual hypersomnolence" in the treated OSA patient, and far and away the most common cause of sleepiness in Western society is insufficient sleep. Additionally though, CPAP nonadherence, coexisting sleep fragmenting disorders, and chronic medical or psychiatric conditions may also play a role in the complaint of sleepiness or fatigue in the treated OSA patient.

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Responses

  • gerontius
    What are some pap titration techniques?
    6 months ago

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