G.1. I see that the STANDARDS FOR ACCREDITATION state that we are to use the recommended
AASM guidelines, when available. Does this mean if our medical director chooses for us to
use an alternative rule that our accreditation is at risk?
The AASM Manual for the Scoring of Sleep and Related Events is not a guideline or practice parameter, and uses slightly different terminology. The key on page 15 indicates that "recommended," "alternative," and "optional" rules are all methods acceptable by AASM for scoring. An accredited center must follow all of the rules, but based on the discretion of the clinician or investigator a specific center may use "alternative" or "optional" rules in the place of the "recommended" rule. The use of "alternative" or "optional" rules would not create any risk to accreditation.
The term "recommended AASM guidelines" in the accreditation standards refers to the set of guideline papers published by the AASM Practice Parameters. Each paper has recommendations based on evidence and/or consensus with terms ("standard," "guideline" or "option") that are used to reflect the strength of evidence and/or consensus. An accredited center must follow all of the "standard" recommendations, and may or may not follow the "guidelines" or "options."
G.2. When/where will the committee’s response to this (and other) questions be published?
The Steering Committee provides responses to specific questions sent to the national office by
e‐mail to firstname.lastname@example.org such as the one you are reading. Questions of more general
interest have been posted over the past year at this website.
G.3. Is the Steering Committee you referred to the Standards of Practice Committee or is this an
extension of the Task Force for Unattended Testing?
The Steering Committee referred to in the “Clinical Guidelines for the Use of Unattended
Portable Monitors in the Diagnosis of Obstructive Sleep Apnea” was appointed the AASM Board
of Directors to develop, in conjunction with task forces and approval of the AASM Board, the
scoring rules published in “The Scoring of Sleep and Associated Events: Rules, Terminology, and
T.1. I have just bought NEW PSG EQUIPMENT. Do I need to change my equipment again to
become compliant with the technical specifications on pages 19‐21?
No, for AASM accredited centers and laboratories, all new equipment purchased after July 1,
2008 will need to be in compliance with the technical requirements on pages 19‐21. However,
even with existing equipment, by July 1, 2008, you will need to:
- Be compliant with the new rules for EEG, EOG, EMG and respiratory signals, including using both thermal and nasal pressure sensors to record respiratory events (pages 45 and 48)
- Have modified your reporting software to reflect the parameters to be reported (pages 17‐18) and the new sleep stage terminology (page 24)
- Be scoring stages and events according to the new rules
T.2. Is there a requirement for CONTINUOUS AUDIO RECORDING during polysomnography under
the new guidelines?
The manual does not specifically require audio recording. Most laboratories incorporate it within the required video recording process however because there are so many clinical situations in which audio is extremely useful, including but not limited to bruxism, snoring, behavioral disorders, parasomnias, seizures and catathrenia.
T.3. If my AMPLIFIER, purchased prior to July 1, 2008, does not have enough inputs to allow for
the additional EEG and EMG channels, and I am not required to replace this equipment, then
how am I to stage sleep using the new criteria?
Please refer to FAQ T.1. The exception granted for equipment purchased prior to July 1, 2008 refers only to the technical requirements listed on pages 19‐21. This does not include the number of amplifier channels. By July 1, 2008, you will need to have equipment enabling compliance with the new rules for scoring sleep using EEG, EOG and EMG signals. Therefore an adequate number of amplifier inputs to allow recording of the required number of EEG and EMG derivations will be needed.
T.4. I AM BUYING NEW EQUIPMENT in May 2008 with capabilities that will not be compliant with
some of the scoring manual specifications. When must I replace or modify the equipment?
Please note that it is only the technical specifications listed on pages 19‐21 that need not be
present in equipment purchased prior to July 1, 2008. All other requirements must be met as
specified in FAQ T.1. The AASM has not set a specific date by which older equipment not
fulfilling all the specifications on pages 19 21 need be replaced or modified. Any replacement
equipment purchased after July 1, 2008 must be in full compliance with all technical
T.5. The blanket technical requirement for all channels is 12-bit which makes sense for most channels, and especially the high frequency channels. But it doesn’t make sense for the Body Position channel. Eight bit resolution provides up to 256 values for a signal that generally has 5 total positions, so 12 bit is very much overkill with over 4,000 possible values. I would ask for reconsideration in the standard requirement specific to Body Position.
You are correct. The Scoring Manual assumes that a single digital resolution standard is applied to all channels. In fact, 3 bit resolution would be adequate for the body position sensor. The Body Position channel should be exempt from the digital resolution standard. However, the recommended sampling rate of 1 Hz remains in effect.
T.6. AASM guideline III.1.C.1. states that the resolution of the digital screen must be at least 1600x1200. It is becoming cost prohibitive to find the appropriate device now that the industry has standardized on widescreen models for LCD displays. Many of the widescreen models have a vertical resolution of 1080 (vs 1200). Are there any plans to adjust this resolution to adapt for the new monitor standard of wide screen?
Widescreen monitors with a minimum resolution of 1920×1080 (standard for HDMI with aspect ratio of 16:9, also known as "HD 1080") are also acceptable for PSG display.
V.1. Is it permissible to use the RECOMMENDED EOG derivations AND the ALTERNATIVE EEG
derivations for the same study, or must we use either the recommended or the alternate
derivations for both EEG and EOG?
You may choose between the recommended and alternative derivations for EEG and EOG
within the same study.
V.2. I currently use EOG derivations similar to the alternative ones (page 24, B.2.) but the
REFERENCE FOR EYE LEADS is Fz rather than Fpz. Is this permissible?
No, in the interests of standardization, the EOG derivations in the manual (recommended or alternative) should be followed exactly.
V.3. I currently record LEFT‐SIDED EEG (F3, C3, O1) and reference to M2. This is the mirror image of
the recommended derivations (page 23, A.1.) Is this permissible?
No, in the interests of standardization, the routine EEG derivations in the manual (recommended or alternative) should be followed exactly. Exceptions are allowed only in individual cases when applications are prevented by local conditions such as scalp conditions or focal encephalomalacia.
V.4. I plan to use the recommended EEG derivations (page 23, A.1.) If the C4 ELECTRODE BECOMES
DISCONNECTED during the study, can I replace C4 with C3 and continue to record F4‐M1 and
O2‐ M1, or must I then change all 3 derivations to recording from the left side of the head?
You need only change the derivation that incorporates the faulty electrode. However, in the scenario described above, you would change to C3‐M2, rather than C3‐M1, even if the M1 electrode is intact.
V.5. I plan to use the alternative EEG derivations (page 23, A.2). The amplitude of EEG activity
during stage N3 sleep should be measured using the frontal derivation (page 27, definition).
Won’t the use of the bipolar derivation Fz‐Cz result in EEG CANCELLATION EFFECTS, reducing
the amplitude of the signal compared to a referential derivation, such as F4‐M1?
You are correct. Fz‐Cz is not appropriate for measuring the amplitude of frontal activity for the reason you describe. If you are using the alternative EOG derivations (page 24, B.2.), then we recommend you use the E1‐Fpz derivation to measure frontal slow wave amplitude. Used in this way, Fpz will be the active electrode recording frontal activity and E1 the reference electrode in a referential derivation. If you are using the recommended EOG derivation (page 24, B.1.), then we suggest you measure EEG amplitude using the C4‐M1 derivation.
V.6. Regarding the END OF A PERIOD OF STAGE R SLEEP RULE [page 28, 7.C.]: Epoch 50 (see Figure
1 below) is typical R sleep, epoch 51 is R sleep with a K complex (but no arousal) in the 2nd
half of the epoch, epoch 52‐54 have low amplitude mixed frequency EEG activity and low
muscle tone but no REMs or K complexes, epoch 55 has low amplitude mixed frequency EEG,
low muscle tone and REMs in the first half of the epoch. Should epochs 52‐54 be scored N2 or
According to the rules for ending a period of stage R sleep (page 28, C1.e and page 29, Figure
7), epoch 51 would be scored as R and epoch 52 would be scored as N2. According to the rules
for the transition between stage N2 and R (page 30, D.3), epochs 53‐ 54 would be scored as R.
This question is in response to a previous question (V.6.) concerning the END OF A PERIOD OF
STAGE R SLEEP RULE [page 28, 7.c]. In the figure shown for question V.6., epoch 52 has no K
complexes or spindles and maintains a low chin EMG. If we are indeed moving to an epoch by
epoch scoring mandate then why would you score this epoch as N2 rather than REM? Rule 7
C specifically states ending stage R when the K‐complex occurs in the first half of the epoch.
The only exceptions I know of for the epoch by epoch staging mandate are those of when
REM begins before eye movements are seen i.e. when chin EMG drops in the absence of Kcomplexes
and spindles, and staging what used to be movement epochs which is now
determined by the following epoch's stage provided there was sleep in the previous epoch.
he epoch 52 in V.6 should be scored as N2 because REMs do not appear following the epoch;
this is consistent with both the right sided part of Figure 7 in the manual (p. 29) and the right
sided part of Figure 9 (p. 30) which shows REM scoring if subsequent epochs demonstrate
REMs. Please note also Rule 5.A.1 which mandates scoring stage N2 if a K complex or spindle
occurred in the second half of the previous epoch. The Committee feels that their response to
V.6 FAQ is a reasonable interpretation of an uncommon scenario.
V.7. How are epochs BETWEEN an initial N1 with slow eye movements AND an epoch of R with
rapid eye movements scored if all the epochs demonstrate low amplitude mixed frequency
and there are no changes in the EMG?
There are no rules in the AASM manual specifically dealing with stage N1‐R transitions.
R will only commence when rapid eye movements are seen in association with low muscle tone
and the typical EEG (Rule 7A. page 27).
Occasionally FRONTAL derivations are the only derivations that DETECT spindles, or arousals
during an epoch. Can these events be used to score sleep even if they are only found in the
frontal derivations? The scoring manual indicates that spindles are “maximal in amplitude
using central derivations” and that arousal should be scored from “both the occipital and
Yes. Although sleep spindles and frequency changes associated with arousals are more typically
noted in the central and occipital derivations respectively, these events should be used to score
sleep even if they are only noted in the frontal derivations.
V.9. If a patient has a generalized tonic‐clonic seizure during sleep, how do you score the following
With the exception of epochs that meet criteria for movement time, epochs that cannot be
scored as sleep or wake should be excluded from scoring and summary data. Appropriate
comments should be included in the summary statement section of the report. In the example
given, EEG slowing would not be scored or reported as wakeful or sleep time. The summary
report would note the seizure as well as periods of post‐ictal slowing that could not be scored.
V.10. The rule for N3 sleep (p. 27) says that you should score N3 whenever 20% of the epoch
consists of slow wave activity. This makes sense if the rest of the epoch is low amplitude
mixed frequency EEG, but what if there is an awakening after 6 seconds of dense slow wave
activity and alpha rhythm activity for the remainder of the epoch? Would this still be N3?
No, this would be scored as W using IV.2.B.3.
V.11. R ends with a transition to W (p. 28), but doesn’t end if there is an arousal that is not
followed by slow eye movements. What if the arousal consists of a shift to alpha rhythm that
lasts 3 seconds? Would that be a transition to W? How about 5 seconds? Or do you need an
epoch of W to end R?
Arousals in R do not end R. A 3 or 5 second shift to alpha in R requires a 1 second rise in EMG to
constitute an arousal in R under Rule V. An epoch containing alpha for greater than 15 seconds
would be scored W, ending R.
V. 12. I have a question regarding sleep study staging when the patient is disconnected from the recording equipment, to use the restroom for example. What stage should be scored? I was under the impression that it would be Wake since the patient is theoretically awake while using the restroom. My medical director was educating one of our fellows today and told her that it should be scored as Movement Time or Unscored.
Time with the patient disconnected from the recording equipment should be scored as stage W. Brief episodes of sleep during this time, if they occur, are not considered significant for the stage scoring summary.
A.1. Can you score AROUSALS IN AN AWAKE EPOCH if 10 seconds of sleep precedes the event and
all other criteria are met?
Yes. Arousals meeting all scoring criteria but occurring during an awake epoch in the recorded
time between “lights out” and “lights on” should be scored and used for computation of the
A.2. There is a disagreement between the scoring of arousals in wake and the scoring of respiratory events in wake. The scoring of arousals allows for one arousal every 13 seconds, resulting in a possible maximum arousal index of 276.9 per hour. Use of this rule introduces the statistical possibility for reporting of an irrational index. The AASM should reconsider its position with regard to scoring arousals in wake epochs, change the guidelines for scoring wake in the concurrence with "scorable" arousals or else change the definiton of C2 from the reported arousals per hour of sleep to arousals per hour in bed (Ar/hrTIB).
The ability to count respiratory events if they ”touch” sleep (R10) and reporting observations in the narrative (R5) help tie respiratory events to sleep fragmentation. A1 helps count arousals related to drowsiness/wake. Using epoch scoring rules one could not have a theoretical average of >1 arousal/epoch in wake (for 2 arousals, 10 seconds + 10 seconds = 20 seconds and thus sleep would be the majority of the epoch and would be scored as an epoch of sleep). Excessive scoring of arousals in wake does not seem a practical problem.
C.1. On page 39, 2. A and B scoring of tachycardia and bradycardia, what is meant by
Sustained sinus bradycardia or tachycardia is defined by more than 30 seconds of a stable
rhythm to distinguish it from transient responses associated sleep disordered breathing events
M.1. In scoring the PSG FEATURES OF RBD, how many epochs of REM sleep must show either
sustained or excessive transient muscle activity for REM sleep as a whole to be considered
compatible with RBD?
The manual has deliberately not specified this as there are little normative data. Clinicians are
encouraged to read the relevant section of the supporting paper (J Clin Sleep Med 2007;3:159‐
161) to help them decide how to address this issue in their own laboratories.
M.2. There are numerous leg movement sensors available. We switched from electrodes to
sensors several years ago and have been happy with the response. Will it be necessary to
return to LEG ELECTRODES to score PLMS?
Bipolar EMG electrodes are required for PLM scoring as noted in Parameters to be reported (II. A. 4.) and the notes appended to PLM scoring rules (VII.1.notes).
M.3. In our lab we score arousals associated with PLMs. Since you cannot score arousals unless
there is 10 seconds of sleep preceding the arousal, can I score an arousal that is associated
with a PLM when there can be as little as 5 seconds since the last PLM with arousal?
The short answer is no, you cannot score arousals with less than 10 seconds of intervening
sleep. Members of the Movement Rules and Arousal Rule task forces were consulted on this
question. The Movement Rules perspective was that conceptually it would be possible to have
multiple limb‐movement related arousals with the minimal interval between limb movements
(5 seconds from onset to onset). However, the Arousal Rule perspective is that the scoring of
such arousals would be technically quite difficult. Since an arousal must last a minimum of 3
seconds, this would leave only 2 seconds to determine that sleep had resumed. The Steering
Committee reviewed both perspectives and determined that the arousal rule should hold and
that a minimum of 10 seconds is necessary to reliably determine that the patient has returned
to sleep. When periodic limb movements occur with an interval of less than 10 seconds and
each is associated with a 3 second arousal, only the first arousal should be scored though both
limb movements may be scored. In this scenario, the arousal index and PLM index with arousal
but not the Periodic Limb Movement Index would be influenced by not scoring the second
M.4. Are limb movements counted even if they are isolated and do not occur in a series?
Limb movements are only counted if they meet all criteria in VII.1.A.1‐5 and are incorporated
within a PLM series as defined by VII.1.B.
I discovered an issue for clarification in the scoring manual on p 41 concerning note 1 in the
PLM section. It states “An LM should not be scored if it occurs during a period from 0.5
seconds preceding and apnea or hypopnea to 0.5 seconds following an apnea or hypopnea.”
I think the intent was to say that the LM should not be scored during a period from 0.5
seconds preceding to 0.5 seconds following the termination of an apnea or hypopnea. As
stated, it indicates that no PLMs would be scored at all during a respiratory event.
Note 1. in VII.1. is correct as stated: An LM should not be scored if it occurs during a period from 0.5 seconds preceding an apnea or hypopnea to 0.5 seconds following an apnea or hypopnea. This period is inclusive and no LMs should be scored.
R.1. I perform epidemiologic studies of sleep apnea. It is very important that all research studies
use the same criteria for hypopneas to allow valid comparisons between different protocols.
How will this be possible with TWO RULES FOR HYPOPNEAS?
We strongly recommend that investigators use the alternative rule for hypopneas (page 46,
4.B.) in all prospective epidemiological and outcome studies. For clinical purposes, sleep
specialists may select either the recommended (pg 46, 4.A.) or alternative (page 46, 4.B.) rule.
Certainly, for comparison purposes in clinical research or practice, both methods may be
R.2. What should be done when one AIRFLOW SENSOR FAILS? If I am monitoring with both a
thermal sensor and a nasal pressure sensor and the nasal pressure sensor stops working, how
can I now define hypopneas?
The manual recommends using back‐up sensors when one fails. When the nasal pressure
sensor fails, the oronasal thermal sensor should be used for scoring hypopneas. [pages 45 & 48,
R.3. Is CALIBRATED INDUCTANCE PLETHYSMOGRAPHY required for detection of respiratory
No. The recommended sensors for detection of respiratory effort are either calibrated OR
uncalibrated inductance plethysmography OR esophageal manometry.
R.4. Are PIEZO BELTS acceptable as sensors for detection of respiratory effort?
No. The recommended sensors for detection of respiratory effort are calibrated OR
uncalibrated inductance plethysmography OR esophageal manometry. As indicated in the
supporting review paper, (J Clin Sleep Med 2007; 3:172), piezo belts are not felt to be a
satisfactory reflection of respiratory effort.
R.5. Can we score apneas and hypopneas during epochs scored as wake?
Although it is recognized that apneas and hypopneas can occur during drowsiness preceding
stage N1 sleep, these should not be scored because of the difficulty of defining the
denominator to calculate an apnea hypopnea index. If these events are prominent and
interfere with sleep onset, their presence should be mentioned in the narrative summary of the
R.6. During CPAP TITRATION, are both thermal sensors and nasal pressure sensors required for
scoring apnea and hypopnea?
The scoring manual does not specifically apply to scoring of respiratory events during CPAP
treatment. Alternative methods for verifying flow such as flow output from the CPAP device will
be necessary during treatment as nasal pressure and thermal sensor measures may no longer
R.7. Are both a thermistor and a nasal pressure transducer recommended for detection of
Yes. A thermistor is recommended for detection of the absence of airflow for the purpose of
identifying apneas. A nasal pressure transducer with or without square root transformation of
the signal is recommended for the detection of a flow reduction for the purpose of identifying
hypopneas. As indicated in the scoring manual review paper, J Clin Sleep Med 2007; 3:169/, use
of only a nasal pressure transducer can result in misclassification of hypopneas as apneas.
R.8. Is arousal required for scoring RERAs in children?
Yes. Scoring of RERAs in both adults and children requires that the RERA be associated with an
arousal that conforms to the recommended AASM arousal rule.
R.9. The standards require an oximeter to have a maximum signal averaging time of 3 seconds.
But some OXIMETERS' SAMPLING TIMES are linked to heart rate and thus may at times be
longer during periods of bradycardia. Is this acceptable?
Yes, as long as the maximum signal averaging time at a heart rate of 80 beats per minute or
more is 3 seconds or less.
R.10. In some cases, APNEAS AND HYPOPNEAS may begin during an epoch scored as sleep, but end
during an epoch scored as wake. Can these events be scored and used for the computation of
Yes. If any portion of either the apnea or hypopnea occurs during an epoch that is scored as
sleep, then the corresponding respiratory event can be scored and included in the computation
of the AHI. This situation usually occurs when an individual has a high apnea hypopnea index
with events occurring so frequently that sleep is severely disrupted and epochs may end up
being scored as wake even though there are brief seconds of sleep between the respiratory
events. However, if the apnea or hypopnea occurs entirely during an epoch scored as wake, it
should not be scored or counted towards the apnea‐hypopnea index because of the difficulty of
defining a denominator in that situation. If these occurrences are a prominent feature of the
polysomnogram and/or interfere with sleep onset, their presence should be mentioned in the
narrative summary of the study as well.
R.11. I am concerned about the requirement that 90% of the EVENT DURATION must meet the
amplitude reduction criteria. I see that there was no evidence and no agreement by the
respiratory task force, and that this criterion was adjudicated by the steering committee.
If the amplitude and/or desaturation criteria are met during any contiguous 10 seconds of an
event that lasts longer than 10 seconds, then the event should be scored even if the duration of
the amplitude reduction does not constitute 90% of the total event duration. In the example
cited, any contiguous 10‐second period during the 17 seconds would be scored and classified
based on the amplitude and/or desaturation criteria for hypopnea or apnea. The event duration
would be that measured for the length of the entire episode.
R.12. It does not make sense to me that a 17‐second reduction in AMPLITUDE would not be
counted if the event is 20 seconds long, but that a 9‐second reduction would be adequate if
the duration of the event is 10 seconds. What is the rationale for this criterion?
Scoring of hypopneas and apneas requires a minimum duration of 10 seconds. If the amplitude
criteria are met during any contiguous 9 seconds of an event that lasts 10 seconds or longer
then the event should be scored even if the duration of the amplitude reduction does not
constitute 90% of the total event duration. In the example cited, any contiguous 9‐second
period during the 20 seconds would be scored and classified based on the amplitude and/or
desaturation criteria for hypopnea or apnea. The event duration would be that measured for
the length of the entire episode.
R.13. What is meant by "BASELINE" in the new AASM scoring manual? We are using the alternative
definition for hypopnea in non‐Medicare patients. Hypopnea is defined as > 50% drop in the
nasal pressure signal compared to baseline associated with either a 3% desaturation or an
arousal. I am meeting with our techs on a regular basis in an attempt to insure uniform
scoring under the new criteria. I have attached a typical example. The labeled events are
those scored by the technologist. There are other events present which are associated with
arousals which the tech did not score because he did not believe that there was a 50% drop in
flow. There is a 50% drop in flow compared to the recovery breaths but this may not be
"baseline" in that the patient is hyperventilating in response to the event. Is it acceptable to
use the amplitude of these three to four breaths following the event as "baseline" and
compare the reduced breaths to these?
If there is no clear baseline breathing to measure, due to a high frequency of abnormal
respiratory events, then the recovery breaths between the frequent apneas or hypopneas
would be acceptable to use for an approximate baseline against which to measure the percent
of drop for the next reduction in airflow.
R.14. Can the INTERCOSTAL EMG be used as an alternative sensor for detection of respiratory
As noted in Section VIII, 1, Note 3 of the scoring manual, “An alternative sensor for detection of
effort is diaphragmatic/intercostals EMG.” However, it should be emphasized that an
interpretable diaphragmatic/intercostal EMG signal is sometimes difficult to obtain especially in
obese patients. Thus, sole use of this sensor to assess respiratory effort is not encouraged.
R.15. Can the HYPOPNEA RULES 4a and 4b on page 46 be combined to compute a single AHI?
No. Each AHI reported should be based on consistent application of either rule 4a or 4b. Scoring
using 4a and 4b cannot be combined to compute a single AHI. Laboratories that choose to use
both rules must report AHI for each rule separately.
R.16. What, according to the new standards of the AASM, do they want us to do with SNORING?
Are we mandated to measure it? How are we to measure it? Score it? Interpret it?
The presence of snoring should be commented in the text of the report with interpretation of
severity left to the discretion of the clinician/investigator. The scoring manual does recommend
methods for data acquisition but not for reporting. Since there was insufficient evidence to
specify an objective measure of snoring, specific reporting measures are not required. For
example a statement such as follows may be an adequate way to handle the situation: "There
were frequent, almost continuous moderately loud to loud snores present. These occurred in
all positions but appeared to be worse supine. Intermittent snore related arousals appear
independent of definable apneas and hypopneas."
R.17. The new scoring manual indicates that piezo technology may not be used for chest and
abdominal movement. Does this mean that piezo technology may not be used for other
sensors such as nasal pressure?
The AASM scoring manual neither prohibits nor recommends the use of piezo technology for
other than abdominal or chest movement. [A device used for measurement of nasal pressure
should, however, provide semiquantitative airway pressure signal comparable to pressure
measured by transducer].
R.18. In your FAQ R 15, you state you can not combine 4a and 4b hypopneas. Are there any studies
that have looked at this, comparing AHI for scoring by 4b vs. combining 4a and 4b? I have a
problem ignoring hypopneas that fit your 4a recommended hypopneas rule, just to score
more "liberally" under 4b; are we accurately describing the patient’s true AHI if we ignore 4a
hypopneas? Also, is there really a difference between a 30% and 50% drop in flow, when we
are using qualitative rather than quantitative flow sensors? My understanding of thermistor
and pressure monitor is that they both are not quantitative, so is talking in terms of a percent
drop in flow really valid?
The AASM scoring manual has recommended standardization of rules to improve
reproducibility of measures. This requires the choice of a recommended or alternative rule and
sticking with it throughout the record. In the case of AHI, reproducibility would be degraded if
some laboratories chose to combine hypopnea rules and others employed and identified single
R.19. Is there a rule stating how many seconds from the end of a respiratory event until the
beginning of an arousal for them to be associated with each other?
The scoring manual does not specify the time requirement linking arousals and respiratory
events. Apneas and hypopneas did not require arousals for scoring. When arousals do occur
with respiratory events, they usually occur within 5 seconds of airway opening.
In the special article “Clinical Guidelines for the Use of Unattended Portable Monitors in the
Diagnosis of Obstructive Sleep Apnea” published in the December, 2007 issue of JCSM, it is
recommended in Section 2.2 that both nasal pressure transducers and thermistors be used to
detect apneas. However, the article details the limitations of both of these methods, namely
the inability to detect oral flow (nasal pressure devices) and the non‐linear relation to airflow
and overestimation of ventilation (thermistors). The guidelines also state in the next section
(2.3) that respiratory inductance plethysmography, when appropriately calibrated, provides
an accurate measure of tidal volume. Since (Tidal Volume) = (Flow) x (Time), might a
measurement of tidal volume calculated using calibrated RIP be an acceptable alternative for
measuring flow? How might we initiate some dialog with AASM regarding this alternative?
There is insufficient evidence to support the use of RIP as an alternative to standard flow measurements in respiratory event scoring in clinical settings. Given the careful evidence review and consensus underpinning the decision to employ nasal pressure and thermal sensors for flow detection detailed in the review “The scoring of respiratory events in sleep: reliability and validity” [ J Clin Sleep Med 2007;3:169‐200], nasal pressure and thermal sensors are recommended for flow detection for both the laboratory setting (“The Scoring of Sleep and Associated Events: Rules, Terminology, and Technical Specifications”) and in portable monitoring (“Clinical Guidelines for the Use of Unattended Portable Monitors in the Diagnosis of Obstructive Sleep Apnea”).
I am looking for clarification on the mixed apnea rule. It states, "Score a respiratory event as
a mixed apnea if it meets apnea criteria and is associated with absent inspiratory effort in the
initial portion of the event, followed by resumption of inspiratory effort in the second portion
of the event." Previously, my lab has scored events as mixed only if effort was absent during
the initial 10 seconds of the event. If the initial 10 seconds contained effort, it was classified
as an obstructive event in my lab. Is there a time criteria given for "initial" and "second
portion" in this rule?
There is not sufficient evidence to support a specific duration of the central and obstructive
components of a mixed apnea, thus specific durations of these components were not
I attended the June 8th APSS session, “Implementing the AASM Scoring Rules” in 2008. It was
very informative and well presented, but I and another audience member had a question
about the use of the word contiguous during the respiratory scoring lectures (and also in a
FAQ answer) that seemed to change the meaning of a rule in the 2007 scoring manual. The
FAQ question is R.11. The answer states that "if the amplitude criteria are met during any
contiguous 9 sec of an event that lasts 10 sec or longer then the event should be scored…"
The word contiguous was used on 6/8/08 by presenters as well. In the 2007 scoring manual,
the word contiguous is not used as far as I could see. When the word contiguous is used, it
seems to means that apneas and hypopneas need only be 9 seconds in duration thus
changing the duration criteria of the definitions. This is because the 1 second that does not
meet amplitude criteria must be at the beginning or end of the event if the event is 10
seconds in duration. When the specification of being contiguous is not used it means that
during a 10 second apnea or hypopnea there may be 1 second at any point during the event
that does not meet amplitude criteria so the event is still defined as being 10 seconds long.
We took the use of the word contiguous as meaning that now apnea and hypopneas are
defined as being 9 seconds long since the first or last second of a 10 second event need not
meet amplitude reduction criteria (even though I don’t see the word contiguous in the 2007
scoring manual itself.) Also‐ In reading both R.10 and R.11, I’m thinking that in the context of
the example of the 17 second event, I understand the recommendation to look for 9
contiguous seconds within that event. However for a 10 second event the manual does not
specify that the 9 seconds be contiguous and this is what seems to change the event duration
criteria to 9 seconds.
Respiratory events require a minimum duration of 10 seconds in adults and 2 breaths in children. The abnormality must last this specified duration though amplitude criteria are required for only 90% of the duration. Any event that does not have an abnormality lasting a total of 10 seconds [or 2 breaths in children] cannot be defined as an apnea or hypopnea. Abnormalities lasting only 9 seconds are not scored as respiratory events in adults. The published FAQ R12 states “Scoring of hypopneas and apneas requires a minimum duration of 10 seconds. If the amplitude criteria are met during any contiguous 9 seconds of an event that lasts 10 seconds or longer then the event should be scored even if the duration of the amplitude reduction does not constitute 90% of the total event duration.” Thus relatively rare events that incorporate only 7 or 8 seconds meeting amplitude criteria will not meet criteria for an event.
R.23. My question is about respiratory sighs during sleep. Was this normal, physiological event ever
addressed during the creation of the new respiratory scoring rules? I would like to know how
the committee feels about scoring or not scoring, single or multiple sighs during sleep. There
is no mention of sighing at all in the new handbook.
Many phenomena that occur during the recording sleep studies were not included in the
scoring manual because of their uncertain significance. Deep breaths that accompany arousals may be followed by single central apneas though the significance of this phenomenon is not
R.24. We are puzzled by a hypopnea rule on page 46. It is 'note #2' under '4.Hypopnea Rules' which
stages that "classification of hypopneas as obstructive, central or mixed should not be
performed without a quantitative assessment of ventilatory effort (esophageal manometry,
calibrated inductance plethysmography, or diaphragmatic/intercostal EMG)."
The questions are as follows:
1) We don’t understand how intercostal EMG channels can be quantitative. We use
intercostal EMG channels. This is a basic EMG channel. Would this channel be quantitative if
we added a grid to the display so that we could visualize the number of microvolts that
represent the EMG changes? Is there some other way to make this parameter quantitative?
All surface electrical recordings are quantitative. Although voltage specifications for
quantitative EMG are required for PLMs, there is no voltage requirement in recording
respiratory muscle activity.
2) A further question is how does quantitative assessment of ventilatory effort allow
someone to deduce whether or not a hypopnea is obstructive? Is the answer that when the
efforts increase but the airflow does not then the hypopnea is obstructive? This is
counterintuitive for me since the airflow channels are not quantitative and yet, to deduce
whether or not an event is obstructive, they are used with the efforts channels which would
be quantitative. (I would wonder why flattening of nasal pressure signal, paradoxical efforts
in RIP channels or snoring couldn’t be used as signs of obstruction.)
Classification of apneas as obstructive, central and mixed is recommended [VII.3.B] but
classification and reporting of hypopneas as obstructive, central, or mixed was not
recommended because of the lack of evidence for a reliable method for these classifications.
It is recognized, however, that some respiratory events meeting criteria for hypopnea may
occur as a result of decreased effort [for instance during REMs] rather than obstruction. The
note VII.5.1 was provided for those who would like to add interpretive comment that would
support obstructive or non‐obstructive evidence. Reduction in semiquantitative measure of
airflow with increase effort would suggest obstruction. We also agree that inspiratory flow
flattening and snoring suggest obstruction. Paradoxical movement is may be present during
REM [due to chest wall inhibition] without obstruction.
R. 25. What is considered "pre-event" baseline pulse oximetry for scoring a hypopnea? Can I choose a baseline pulse oximetry reading during stable, non-eventful N sleep and use this "baseline number" as my "pre-event" baseline number during the remainder of the recording OR is there a standard duration of time prior to or after a hypopnea which is used to determine a patient's "pre-event" baseline?
The pre-event baseline must be determined from the oximetry reading prior to each event. A single pre-event baseline obtained during any period of stable, non-event containing sleep cannot be used. The pre-event baseline should be defined as the closest stable oximetry reading prior to the event or in the case where events are sufficiently frequent such that recovery of oxygenation does not occur, the highest value prior to the event.
R. 26 For adult patients suspected of hypoventilation, the technologists have to apply a thermistor, a nasal pressure cannula and then another much larger cannula to monitor End Tidal CO2. Patients object and suffer significant anxiety when their nares are completely filled with 2 cannula and a thermistor. Is it possible to omit using a thermistor in cases where it is simply not practical or outright impossible to fit 2 cannula and a thermistor into a patient's nares?
End Tidal CO2 is considered adequate to detect the presence or absence of air flow, but does not provide the same amplitude variation as the nasal pressure signal. Therefore, in the setting when hypoventilation MUST be monitored and End Tidal CO2 is VALIDATED, End Tidal CO2 may be used as an ALTERNATIVE to the thermistor but only for apnea detection.
P.R.1. Is ETCO2 an acceptable air flow signal? Can it replace one or both of the others?
As specified in the notes following the technical considerations 1A and 1B on page 48, end‐tidal PCO2 may be used as an alternative sensor for the detection of apneas only when the oronasal thermal sensor is not reliable. It may not be used for detection of hypopneas.
P.R.2. In reviewing the respiratory rules for hypopneas in children, the only alternative sensor for
detection of airflow for identification of a hypopnea is an oronasal thermal sensor.
The option of using an uncalibrated or calibrated inductance plethysmography sensor when
the nasal pressure device is not functioning is listed as an alternative option in the adult
respiratory rules. It is NOT listed as an alternative for children. Is this an oversight?
It's important to have the option to use an inductance "sum" sensor in children. Directly
measured airflow signals placed under the nose like nasal pressure (or even oronasal airflow)
are frequently absent or poor quality because of mouth breathing or patient intolerance.
Slippage of the inductance plethysmography belts is common in children and the sum channel
is not considered to be an accurate measure of flow. Airflow should be measured at the nose in