Difference between revisions of "PAP Technology"
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| A/H flow comparison || Prior 1 min RMS moving average. || Prior 1 min RMS moving average. || Average of 80th–90th percentile WPFs of prior 4 min moving average. || Prior 5 min scaled flow amplitude. || 3 min including time before and after event RMS moving average | | A/H flow comparison || Prior 1 min RMS moving average. || Prior 1 min RMS moving average. || Average of 80th–90th percentile WPFs of prior 4 min moving average. || Prior 5 min scaled flow amplitude. || 3 min including time before and after event RMS moving average | ||
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| − | | Apnea detection || 2 s RMS moving average <25% for 10 s. || 2 s RMS moving average <25% for 10 s. || WPF per breath <20% for 10 s, terminating with breath >30%. || Recent 1 min with flow amplitude <10% for 10 s (or set 0%–20% for 6–150 s). || 4 s RMS moving average <10% for 10 s. | + | | Apnea detection || 2 s RMS (Root Mean Square) moving average <25% for 10 s. || 2 s RMS moving average <25% for 10 s. || WPF (Weighted peak flow) per breath <20% for 10 s, terminating with breath >30%. || Recent 1 min with flow amplitude <10% for 10 s (or set 0%–20% for 6–150 s). || 4 s RMS moving average <10% for 10 s. |
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| Non-OA detection || S8: None S9–S10: 1 cm 4 Hz FOT throughout apnea with mixed apnea detection. || 1 cm 4 Hz FOT with mixed apnea detection. || Pressure pulse few seconds into apnea but if larger than expected breath at end of apnea, event is defined as obstructive. || <5% for 10 s || Modulating 0.07 cm 3.5–4.5 Hz micro-oscillation throughout apnea. | | Non-OA detection || S8: None S9–S10: 1 cm 4 Hz FOT throughout apnea with mixed apnea detection. || 1 cm 4 Hz FOT with mixed apnea detection. || Pressure pulse few seconds into apnea but if larger than expected breath at end of apnea, event is defined as obstructive. || <5% for 10 s || Modulating 0.07 cm 3.5–4.5 Hz micro-oscillation throughout apnea. | ||
Revision as of 02:18, 19 June 2019
Overview of device types CPAP maintains a continuous Positive Airway Pressure (PAP) throughout inspiration and expiration. Autoadjusting (Auto) CPAP can gradually increase or decrease the pressure based on respiratory events, but similarly maintains the same pressure throughout the respiratory cycle. This can be helpful for patients who may need a higher pressure in rapid eye movement (REM) or supine position, but cannot tolerate the higher pressure through the entire night. AutoCPAP can also be used diagnostically to determine a fixed pressure setting.
Most CPAP devices allow for pressure settings between 4 and 20 (all pressures in cm⋅H2O). An EPAP of 4 is the lowest pressure needed to provide enough flow to clear the dead space from the device, tubing, and airway to prevent rebreathing of exhaled air. The goal of CPAP is to increase upper airway pressure enough to provide a pneumatic splint to open the airway, which may collapse during inspiration. Typically, the pressure is set to prevent hypopnea, apnea, snoring, flow limitation, and arousals. By providing positive end expiratory pressure, CPAP may recruit alveoli and improve ventilation.
BiPAP provides a higher pressure during inspiration and lower pressure during expiration. This may improve tolerance and help with ventilation. A backup rate can be added to give a breath with weak or absent respiratory effort. AutoBiPAP may adjust either the expiratory positive airway pressure (EPAP) and inspiratory positive airway pressure (IPAP) with a fixed pressure support (PS) or may adjust them independently.
SV is a bilevel system that continuously changes the inspiratory PS on a breath-by-breath basis in order to achieve a target ventilation or flow for a more constant breathing pattern, especially in the treatment of periodic breathing or Cheyne–Stokes respiration (CSR). Auto forms of SV also increase EPAP in response to obstruction.
Volume-assured pressure support (VAPS) is a variable bilevel PAP that allows the target volume or ventilation to be programmed, which allows more control of ventilation. This is useful for patients with combined periodic breathing and hypoventilation or patients with REM-related hypoventilation related to conditions like chronic obstructive pulmonary disease (COPD), neuromuscular disorders, or obesity, who may need different PS levels at different times.
Table 1 ResMed’s logic for phase determination
| Flow | Rate of change | Phase |
|---|---|---|
| Zero | Increasing | Start inspiration |
| Small positive | Increasing slowly | Early inspiration |
| Large positive | Steady | Peak inspiration |
| Small positive | Decreasing slowly | Late inspiration |
| Zero | Decreasing fast | Start expiration |
| Small negative | Decreasing slowly | Early expiration |
| Large negative | Steady | Peak expiration |
| Small negative | Increasing slowly | Late expiration |
| Zero | Steady | Expiratory phase |
Table 2 AutoCPAP algorithms
| Device | ResMed S8/S9/S10 AutoSet | ResMed S10 AutoSet for Her | Respironics System One REMstar Auto | DeVilbiss IntelliPAP AutoAdjust | DeVilbiss IntelliPAP AutoAdjust 2 |
|---|---|---|---|---|---|
| Sampling rate | 50 Hz. | 50 Hz. | 125 Hz. | 205 Hz. | 250 Hz. |
| Ventilation measure | RMS of the variance of moving average scaled low-pass-filtered absolute value of respiratory flow. | RMS of the variance of moving average scaled low-pass-filtered absolute value of respiratory flow. | WPF of 20%–80% of inspiratory volume. | Scaled amplitude. | RMS of filtered flow. |
| A/H flow comparison | Prior 1 min RMS moving average. | Prior 1 min RMS moving average. | Average of 80th–90th percentile WPFs of prior 4 min moving average. | Prior 5 min scaled flow amplitude. | 3 min including time before and after event RMS moving average |
| Apnea detection | 2 s RMS (Root Mean Square) moving average <25% for 10 s. | 2 s RMS moving average <25% for 10 s. | WPF (Weighted peak flow) per breath <20% for 10 s, terminating with breath >30%. | Recent 1 min with flow amplitude <10% for 10 s (or set 0%–20% for 6–150 s). | 4 s RMS moving average <10% for 10 s. |
| Non-OA detection | S8: None S9–S10: 1 cm 4 Hz FOT throughout apnea with mixed apnea detection. | 1 cm 4 Hz FOT with mixed apnea detection. | Pressure pulse few seconds into apnea but if larger than expected breath at end of apnea, event is defined as obstructive. | <5% for 10 s | Modulating 0.07 cm 3.5–4.5 Hz micro-oscillation throughout apnea. |
| Hypopnea detection | S8: 12 s RMS scaled average 25%–50% for 10 s. S9–S10: above with at least 1 obstructed breath. | 12 s RMS scaled average 25%–50% for 10 s with at least 1 obstructed breath. | 20%–60% for 10 s and ending either with terminating breath over 75% of recent WPF or at 60 s | 10%–50% for 10 s (adjustable to 30%–70% for 6–150 s). | RMS average 10%–40% default (adjustable to 30%–50%) for 10 s. |
| Flow limitation detection | S8: mid-inspiration flatness S9–S10: breath-by-breath flow limitation index from breath shape index, RMS flatness index, and ventilation change and breath duty cycle. | Breath-by-breath flow limitation index from breath shape index, RMS flatness index, and ventilation change and breath duty cycle. | 4 breath average of roundness, skewness, and flatness indices and weighted peak inspiratory airflow. | NA | Flow limitation index based on average of 12 s of breath-by breath-flatness of mid inspiration. Index scored as none, mild, moderate, and severe. |
| Other events detection | S9–S10: unknown apnea – apnea with leak >30 L/min. | Undetermined apnea – apnea with leak >30 L/min. | 1. Hypoventilation – 5 consecutive breaths with mean ventilation <40% 2. Variable breathing – standard deviation/adjusted mean flow over 4 min window above threshold. | Report expiratory puff index number of expiratory puffs per hour. | Expiratory puff index based on strings of several breaths scored as none, mild, moderate, and severe. |
| OA/hypopnea response | Increases pressure based on current pressure every 10 s of apnea: increment max 3 when pressure is 4. Increment drops linearly down to 0.5 when pressure is 20. S8: no increase above 10. | Increases pressure based on current pressure every 10 s of apnea: increment max 2.5 when pressure is 4. Increment drops linearly down to 0.5 when pressure is 20. | If 2 apneas or 1 apnea/1 hypopnea or 2 hypopneas-increases by 1 and holds for 30 s. NRAH logic limits max pressure to 11 or 3 higher than preapnea baseline. If more apneas within 8 min decrease pressure by 2/15 min down to 1 over level that prevents snore then holds pressure for 10 min. Pressure will continue to increase in response to 2 hypopneas. | Increases pressure 0.5/min if one event or 1 cm/min if 2 events are present on previous min. | Increases pressure 1/min for OA. If event is near end of min, response is delayed until following minute so centered moving window completes to allow event to be scored. Increases pressure 0.5/min if hypopnea with 1 other event in 6 min window or 1/min if hypopnea with >1 events in 6 min window. |
| Flow limitation response | S8: increment max 0.45/breath. Lower increment if high leak or as pressure increases further above 10; S9: uses 3 breath average FL index. Increment typically around 0.6/breath for severely flow limited breaths. Lower increment if lower FL index, high leak or as pressure increases further above 15; S10: increment max 0.6/breath otherwise same as S9. | Uses single breath FL index: increment max 0.5/breath for severely flow limited breaths. Lower increment if lower FL index, high leak or as pressure increases further above 10. | Pressure increases by 0.5/min in response to FL. Intermittent upward scans by 1.5 over 3 min to see if improvement in FL then deceases if no improvement. If pressure not held by snore, A/H, or VB logic, then enters testing protocol which collects 3–5 min data, then downward search sequence for Pcrit begins ramping down 0.5/min until Pmin as long as no worsening in FL. If worsening, Pcrit is set, and pressure quickly increases by 1.5 and held for 10 min. Then Popt search increases pressure by 0.5/min for at least 2.5 min to test if FL improve, worsen, or stay the same. If improvement, continues 0.5/min pressure increase; if no improvement pressure decreases by 1.5 and sets Popt and holds for 10 min. FL or other events end all holds. | NA | 0.5/min for moderate–severe flow limitation index as long as there has been an obstructive apnea or hypopnea within the past 8 min. No response if high leak or high expiratory puffs. |
| Vibratory snore response | S8–S9: increment max 1/breath. Lower increment if snore is less severe, high leak or as pressure increases further above 10 S10: increment max 0.6/breath for a loud snore otherwise same as S9. | Increment max 0.5/breath. Lower increment if snore is less severe, high leak or as pressure increases further above 10. | If 3 snores within 30 s from each other, increase 1 over 15 s then hold for 1 min with higher snore threshold at higher pressures. | 1/min for 3 snores per 6 min window. | 0.5/min for moderate–severe snore with no response if high leak or expiratory puffs. |
| Other pressure changes | S8: gradual decrease to Pmin over 20 min after apnea or over 10 min after FL or snoring event as soon as breathing is stable. S9–S10: gradual decrease to Pmin over 40 min after apnea, over 20 min after FL or snoring. | Gradual decrease to Pmin over 40 min after apnea, over 20 min after snore, and over 60 min after flow limitation as soon as breathing is stable. | 1. If high variable breathing is noted, then if recent (5 min) pressure was stable then pressure stays same, if recent pressure decrease then increases by 0.5/min up to 2, and if recent pressure increase then decreases by 0.5/min up to 2. 2. If large leak, reduces pressure by 1 over 10 s and holds pressure for 2 min. | Decreases 0.6 every 6 min until either lowest pressure or events occur. If high expiratory puffs, no response for 1–2 min. | Decides whether to decrease every min. If no events in 1 min period, small decrease of <0.1/min.
If no events in 6 min period, decrease by 0.1/min. If central apnea, pressure decreases and no increase for 6 min. If periodic breathing, no increase, then pressure decreases if persists. |
| High leak detection | 95th percentile leak >24 L/min. | 95th percentile leak >24 L/min | Leak level exceeds flow limit for a given pressure | 95 L/min. | 95 L/min or expected leak for given CPAP level. |
| Ramp | S8–S9: 0–45 min ramp S10: fixed 0–45 min ramp or AutoRamp starts ramping when sleep onset is inferred. | 0–45 min ramp or AutoRamp starts ramping when sleep onset is inferred. | Smart ramp increases faster if obstructive events or FL occur. | 0–45 min ramp. | 0–45 min ramp. |
| Pressure relief | Off or 1–3 cm H2O. | Off or 1–3 cm H2O. | Off or 1–3. | Off or 1–3 cm H2O. | Off or 1–3 cm H2O. |
Note: All pressures in cm ·H2O.
Abbreviations: A/H, apnea/hypopnea; AutoCPAP, auto-adjusting continuous positive airway pressure; CPAP, continuous positive airway pressure; FL, flow limitation; FOT, forced oscillation technique; Hz, hertz; max, maximum; min, minute; NA, not applicable; NRAH, nonresponse apnea hypopnea logic; OA, obstructive apnea; Pcrit, critical pressure; Pmin, minimum pressure; Popt, optimal pressure; RMS, root mean square; s, second; VB, variable breathing; WPF, weighted peak flow.
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