Positive Airway Pressure For Sleep Disordered Breathing By Ahmad Younis professor of Thoracic Medicine Mansoura University

PAP for SDB Studies have shown CPAP to increase upper airway size, especially in the lateral dimension. Positive intraluminal pressure expands the upper airway (pneumatic splint) and increase in lung volume due to CPAP (due to a downward pull on upper airway structures during lung expansion “tracheal tug”), may also increase upper airway size and/or stiffen the upper airway walls, making them less collapsible.

Positive airway pressure (PAP) can: 1-Bring the AHI down to below 5 to 10/hr in the majority of patients. 2-Improves arterial oxygen saturation and decreases respiratory arousals. 3-Increase the amount of stage N3 and stage R. NB : 1-An occasional patient with very severe apnea will have a large REM or stage N3 sleep rebound on the first night of PAP treatment. 2-The most difficult problem with PAP treatment is that adherence is suboptimal in a large percentage of patients.

MODES OF PAP

1- CPAP Continuous pressure during inhalation and exhalation. 2- BPAP (S mode) IPAP. EPAP. IPAP − EPAP = PS. Flexible PAP, expiratory pressure relief (Cflex, EPR) Pressure falls in early exhalation Returns to set pressure at end-exhalation. 3-APAP autotitrating, autoadjusting PAP (autoCPAP) Titrates between maximum and minimum pressure limits to prevent apnea, hypopnea, airflow flattening, and airway vibration (snoring).

MODES OF PAP 4- Auto-BPAP Titrates IPAP and EPAP between EPAPmin and IPAPmax with PSmin = 3 and PSmax set by the clinician. PSmax constrained by IPAPmax. 5- BPAP with backup rate (NPPV) BPAP modes ST. T. 6- ASV PS varies to stabilize breathing. EPAP set to eliminate airway obstruction. Backup rate AVAILABLE

Autoadjusting (autotitrating) PAP, devices : 1-Autotitrating PAP to select an effective level of CPAP without the need for an attended titration 2- Aautoadjusting PAP for chronic treatment with the advantage of delivering the lowest effective pressure in any circumstance. Chronic treatment with APAP would also eliminate the requirement for a CPAP titration.

The APAP algorithms vary between different devices, but in most instances the pressure changes in response to variations in airflow magnitude (apnea or hypopnea), airflow limitation (flattening of the airflow contour), and snoring New technology used by Philips-Respironics attempts “ to differentiate clear airway apneas” versus obstructive apneas by delivering a small pressure pulse (1–2 cm H2O pressure pulse) after approximately 6 seconds of a reduction in airflow. If the pressure pulse does produce an increase in flow, this is compatible with an open airway (clear airway). If the pressure pulse does not increase flow, the airway is closed.

An APAP device using this technology does not increase pressure for “clear airway” apneas.

Autobilevel positive airway pressure with a minimum (EPAP) of 6 cm H2O and a maximum (IPAP) of 25 cm H2O.

ASV is a variant of BPAP that was developed to treat Cheyne- Stokes central apnea. Both ASV and BPAP devices with a backup rate are approved for use with patients with central apnea and complex sleep apnea

The ASV device responds to variation in flow by increasing PS when flow and ventilation are low and decreasing PS when flow is high.

COMFORT MEASURES Ramp Most PAP devices, with the exception of certain APAP devices, allow the patient to trigger the ramp option. In the ramp option, the pressure starts at a preset level—usually a low level of CPAP—and then slowly increases to the treatment pressure (CPAP) over the set ramp time Some APAP devices have a “settling time” at a low pressure before the device starts autoadjusting pressure.

Flexible Pressure Two manufacturers of PAP devices have developed flexible PAP 1- Philips-Respironics provide several comfort options (Cflex, Cflex+, and Aflex) 2- ResMed devices offer expiratory pressure relief (EPR). In Cflex, expiratory pressure drops at the start of exhalation but returns to the set CPAP at end-exhalation. The amount of drop (Cflex 1, 2, 3) is determined by a proprietary algorithm.

Cflex+ adds a smoothing of the transition from inhalation to exhalation. Aflex is a form of APAP that provides a 2 cm H2O lower end-expiratory pressure than the inspiratory pressure (in addition to the features of Cflex* For both BPAP and autoBPAP devices, a form of expiratory pressure relief is available (Biflex). The technology provides a smoothing of transition from IPAP to EPAP as well as expiratory pressure relief during the EPAP cycle (Biflex 1, 2, 3)..

B-Flex found in the Bipap

Humidification Today, most PAP devices come with the option of an integrated heated humidification system. They can be used in the cool humidity mode if desired. Heated humidity can deliver a greater level of moisture than cool humidification and may be especially useful in patients with mouth leak or nasal congestion. Mouth leak can cause a dramatic fall in relative humidity and a loss of humidity from the upper airway/CPAP system, thus drying the nasal or oral mucosa. Use of heated humidification is recommended to improve CPAP utilization. In the clinical guidelines for titration, having HH available for titration was recommended..

Interfaces: Nasal pillow masks are often better tolerated than traditional nasal masks by patients with claustrophobia and are useful in patients with a mustache or edentulous patients who have no dental support for the upper lip. For patients who have severe nasal congestion or open their mouths during PAP treatment, oronasal (full face masks) and oral interfaces are available If the patient gets up to use the bathroom during the night, we encourage disconnection of the hose from mask rather than taking off the mask. Masks that are removed in the middle of the night are often not replaced..

MODES OF PAP INFLAMMATIONINFLAMMATION AirwayHyperresponsivenessAirwayHyperresponsiveness Airflow Obstruction Risk Factors Risk Factors (for exacerbations) Risk Factors Risk Factors (for exacerbations) SymptomsSymptoms

INDICATIONS FOR PAP TREATMENT Patients must be diagnosed with either a PSG or a home sleep test. CPAP treatment if the AHI is 15/hr or greater with or without symptoms or if the AHI is 5/hr or greater but less than 14/hr if certain symptoms (excessive daytime sleepiness, impaired cognition, mood disorders, or insomnia) or certain disorders (hypertension, ischemic heart disease, or history of stroke) are present.