Guidelines Flashcards
Definition of FRC
volume of gas present in the lung at end expiration during tidal breathing
Definition of Expiratory Reserve Volume
volume of gas maximally exhaled from FRC
Definition of Inspiratory Capacity
Maximum amount of gas that can be inspired from FRC
Definition of Inspiratory Reserve Volume
Volume of gas maximally inhaled from end-inspiratory level during tidal breathing
Definition of Residual Volume
Volume of gas remaining in the lung after maximal exhalation
Definition of Tidal Volume
volume of gas inhaled or exhaled during the respiratory cycle
Definition of Total Lung Capacity
volume of gas in the lungs after maximal inspiration (of the sum of all volume compartments)
Definition of Vital Capacity
volume change between full inspiration and complete exhalation
What is the preferred time to measure ERV?
Immediately after acquisition of FRC followed by slow IVC
What are 4 ways you get measure FRC?
- Body Plethysmography
- Gas washout
- Gas dilution
- Radiography
Key points of Plethysmography (ie. what does it measure)
- Includes ventilated and non-ventilated regions of the lung - thus HIGHER than dilution/washout methods
- May also be increased by gas in other areas of the body (ie abdo)
Key points of gas dilution/washout methods
- Tend to underestimate the true FRC
2. Simple and inexpensive to do
How does Plethysmography work?
- Measures volume of intrathoracic gas measured when airflow occlusion happens at FRC
- Minimal difference compared to washout/dilution in healthy people
- Plethys results HIGHER in those with lung disease and gas trapping
- Based on Boyle’s law: P1V1 = P2V2
Measurement technique of Body Plethysmography
- Turn on and calibrate machine
- Patient to close mouth over mouthpiece with neutral neck position
- Close door and allow to equilibrate
- Patient to breathe quietly until stable and expiratory level is met
- Shutter closes at/near FRC
- Patient pants for 2-3 seconds (freq of 0.5-1 Hz). If can’t pant, can do rapid inspiratory maneuvers against closed shutter
Repeatability criteria for Plethysmography
If 3 FRC results are within 5%
Calculation of Delta V in Plethysmography
Box: P1V1 = P2 (V1-delta V)
Lung: P3 FRC = P4 (FRC + Delta V)
Key points for Nitrogen washout
- Based on washing out nitrogen from lungs while patient breathes 100% O2
Measurement technique for Nitrogen washout
- Turn on machine and calibrate
- Patient sits comfortably and breathes for 30-60 seconds to assure stable end-tidal expiratory level
- Patient breathes 100% oxygen
- Exhaled nitrogen is measures
- Considered complete if Nitrogen concentration <1.5% for at least 3 breaths
- Need to wait at least 15 min between attempts
Equation for FRC N2
FRC N2 = (N2 washed out -N2 from tissue)/ (FN21 - FN22)
FN21 = fraction of nitrogen before the washout
FN22 = fraction of nitrogen after the washout
(volume = area under the curve of a N2 fraction % vs volume graph)
Key point of measuring FRC using helium dilution
Based on equilibration of gas in lungs with known volume containing helium
C1V1 = (C1 + FRC) V2
Measurement technique for Helium Dilution
- Breathe for 30-60 seconds to ensure stable end tidal expiratory level
- Patient connected to test gas at end of normal tidal exhalation
- Continues to breathe regular tidal breaths
- O2 is increased to compensate for O2 consumption
- Helium concentration checked q15 seconds
- Test complete when change in concentration = <0.02% for 30 seconds
What is an important value for derivation of the references values
Height = most important factor
** Lung growth typically falls behind growth spurt in adolescents
Definition of FVC
Maximal volume of air exhaled with maximally forced effort from a max inspiration
Definition of FEV1
Maximal volume of air exhaled in the first second of a forced exhalation from a position of full inspiration
What is useful about the flow-volume loop?
Useful for assessing magnitude of effort
- *Should show 1 sec before start to allow for calculation of the back extrapolated volume
- Last 2 seconds should be displayed to show end of test criteria
Definition of Calibration
finding the relationship between the measured values of flow and the actual values of flow
** should be within 3%
3 phases of spirometry
1) Maximal Inspiration
2) Blast of Exhalation
3) Continued Complete Exhalation
Procedure for recording FVC
1) check calibration
2) Explain and prepare patient and get H & W
3) Correct position, noseclip and mouthpiece in mouth with lips closed around
4) For closed and open circuit = inhale completely and rapidly to TLC with <1 s pause, Exhale completely until no more air can be expelled while sitting upright, repeat for 3-8 maneuvers
If there is a delay between TLC and forced expiration, what would that affect?
Delay shown to cause reduction in PEF and FEV1
What is the Back Extrapolated Volume?
- creates a new “time zero”
- found by tracing back from the steepest part (largest slope) of the curve (volume/time) over an 80ms time period
- to be accurate: extrapolated value must be <150mls or <5% of FVC
2 recommended End of Test criteria
- Patient cannot or should not continue further exhalation
- Volume/time curve shows no change in volume (<0.025L) for >1 sec in someone who has exhaled long enough: <10 = >3 seconds, >10 = >6 seconds
*If test does not meet EoT criteria, it should not count towards one of the 3 acceptable maneuvers
7 factors for Acceptable curves
- Good start (extrapolated volume <5% of FVC or <150 mls)
- No cough during first second, or other times that affects accuracy of results
- No early termination (good end of test)
- No Valsalva/glottic closure/hesitation (reduced FEV1 +/- FVC)
- No mouthpiece leak
- No obstructed mouthpiece
- No extra breath during maneuver
3 Between maneuver criteria
- Need 3 acceptable curves
- Repeatability = FVC and FEV1 is <0.15L between largest and next (<0.1L if FVC <1L)
- Try not to exceed 8 blows
Test result selection
- Select largest FVC and FEV1 from acceptable curves
- May also obtain slow VC or IVC (IC tends to be larger than FVC)
Maneuver for doing Maximal Expiratory Flow-Volume Loops
Take rapid full inspiration to TLC from mouth - insert mouthpiece - then maximal expiration followed by maximal inspiration
OR
Insert mouthpiece during tidal breathing - at FRC make slow expiration to RV - slow inspiration to TLC- maximal expiration to RV - rapid inspiration back to TLC
When should patients not take meds before spirometry?
If aim of the study is to document reversible airflow limitation - should do test before regular drugs
(SABA > 4 hours, LABA > 12 hours, no smoking <1hr)
*If aim of study = determine whether lung function can be improved with therapy in addition to current therapy - subject can continue with regular meds
Method for documenting reversibility in spirometry
- After 3 pre-BD loops, give SABA (ventolin) via spacer (dose = 400ug) or ipratropium (4x40ug)
- wait 10-15 min for SABA or 30 min for anticholinergic
- Improved deposition with CFC free MDIs (smaller particle size)
When during the test should you measure Slow VC?
Should be done prior to FVC (due to potential for fatigue and history effects - repeated measurements may increase FRC due to gas trapping in those with severe airflow obstruction)
Can do either IVC or EVC maneuver
Maneuver for Peak Expiratory Flow
Flow achieved from maximal forced expiratory maneuver
Procedure must be rapid - deliver blow without delay
Repeat x 3 - need to be within 0.67L/s to be repeatable
Maneuver for Maximum Voluntary Ventilation
Maximum volume of air a subject can breathe over a specified time (12 sec for normal subjects)
- 3 resting tidal breaths
- breathing at a rate of 90-110/min
- maximal effort (as deep and rapid as possible)
- Sum of all individual exhalations calculated, multipled by correction factor during the best 12 seconds
- minimum of 2 attempts (should be within 20% of each other)
Goal = VT of 50% of VC with RR ~90/min
Definition of Accuracy
The closeness of agreement between the result of a measurement and the true value
Definition of Repeatability
Closeness of agreement between results of successive measurements with the same conditions
Definition of Reproducibility
Similar to repeatability, however the conditions are changed
Patient considerations for lung function testing
- Not within 1 month of MI
- chest/abdo pain, oral/facial pain exacerbated by mouthpiece, stress incontinence, dementia, confusion
What measurement can you use as a surrogate for height?
Armspan (tips of middle fingers)
Things to avoid before PFT
- Smoking within 1 hour
- Alcohol within 4 hours
- Vigourous exercise within 30 min
- clothing that restricts full chest and abdominal expansion
- large meals withn 2 hours
- SABA use within 4 hours
Ways to prevent infection in the PFT lab
- Hand washing, barrier devices
- wear gloves when handling potentially contaminated equipment
- wash hand between patients
- disinfect/sterilize reusable mouthpieces, tubes, valves and manifolds
- equipment that comes in contact with mucosal surfaces should be sterilized, disinfected or discarded
- closed circuit equipment should be flushed with room air 5 times
- open circuit - only the portion of the circuit where re-breathing occurred should be decontaminated
- Decontaminate equipment esp with hemotypsis or oral lesions
- TB: ventilation, air filtration, UV decontamination
What do the references values mean for PFTs?
Comparison to healthy subjects of same anthropometric characteristics and ethnicity
- important to measure height and weight for each person
- adjust for race if possible
Definition of air flow obstruction on PFT
Reduction in FEV1/FVC below 5th percentile of predicted value
*Earliest change = slowing in the terminal portion of the spirogram
Causes of reduced FVC and FEV1 in airflow obstruction
- patients who fail in inhale or exhale completely
- if flow is so slow that they can’t exhale to RV
- lower airway collapse causing gas trapping (RV may be elevated)
Definition of air flow restriction on PFT
Reduction in TLC below the 5th percentile of predicted value and a normal FEV1/VC
*Suspect with reduced VC, increased FEV1/FVC ratio or convex curve
Other causes for high ratio and reduced VC apart from restriction
- submaximal effort
- patchy peripheral airflow obstruction
Does a reduced VC alone qualify for air flow restriction?
No - Need to have reduced TLC as well
** Special = Pneumothorax and non-communicating bullae: normal ratio and normal TLC (on plethys), low FEV1 and low VC, (low TLC if gas dilution)
Definition of Mixed Abnormality on PFT
Presence of obstruction and restriction
*Present when low FEV1/VC AND low TLC
Which measure do you look at for severity classification for airflow obstruction?
FEV1
Mild >70 Moderate 60-69 Moderate-severe 50-59 Severe 35-49 Very severe <35
Why do FRC, RV, TLC and RV/TLC increase with severe obstruction?
Reduced lung elastic recoil
What is considered a meaningful bronchodilator response?
12-15% change from baseline in FEV1 +/- FVC (changes <8% are likely to be within measurement variability)
ATS: change in 12% AND 200ml difference (>12 yrs) from baseline
What variable seems most affected by upper airway obstruction on spirometry?
PEF (can be reduced)
Examples of variable extrathoracic airflow obstruction
Repeatable plateau of inspiratory flow (decreased because the pressure surrounding the airways cannot oppose the negative pressure generated by inspiratory effort)
Ex: VCD
Examples of variable intrathoracic airflow obstruction
Repeatable plateau of forced expiratory and normal forced inspiratory loop
Ex: Tracheomalacia
Examples of fixed airflow obstruction
Repeatable plateau during both expiratory and inspiratory loops
Ex: Subglottic stenosis
What does a sawtooth pattern on inspiratory or expiratory phases mean?
May represent mechanical instability of airway wall
What do you see on spirometry with unilateral mainstem bronchi obstruction?
Maximum inspiratory flow tends to be higher at the beginning than the end, because of a delay in gas filling
What is considered a significant changes in lung function over time?
If FVC or FEV1 change by more than 11-12% in 1 week - likely clinically significant
(>15% in one year = significant)
What is the lower limit of normal for DLCO?
Lower 5th percentile of reference population
Mild >60% but
What can cause isolated reduced DLCO?
Anemia Pulmonary Vascular Disorders ILD Emphysema PH
Causes of normal DLCO in the context of restrictive lung disease
Chest wall or neuromuscular condition
Causes of reduced DLCO in the context of restrictive lung disease
ILD
Sarcoidosis
Pulmonary fibrosis
Causes of reduced DLCO in the context of obstructive lung disease
Emphysema
Lymphangioleiomyomatosis
What can cause an elevated DLCO?
Asthma
Obesity
Intrapulmonary hemorrhage
What does a high DLCO/VA suggest?
Extrapulmonary abnormality (pneumonectomy or chest wall restriction)
What does a low DLCO/VA suggest?
Parenchymal abnormality
Steps in doing a single-breath CO test
- Tidal breathing after nose clips on and patient on mouthpiece
- Exhalation to RV (if severe obstruction, must be <12 seconds)
- At RV, patient connected to test gas and patient inhales to TLC (inspiratory volume should be at least 90% of VC)
- test gas: 0.3% CO, 21% O2, tracer + nitrogen
- tracer should be insoluble, chemically, and biologically inert
- DLCO calculated using alveolar volume, breath hold time, barometric pressure, frac concentration of CO and tracer gas in inspired and exhaled gas
How is dead space measured in the single breath CO test?
Fowler method (the volume at which the shaded area above the tracer gas on the gas washout vs exhaled volume curve = the shaded area below the curve)
How can you measure TLC from the single breath CO test?
Calculated by adding the expired volume to the end expiratory volume and subtracting dead space
What are the acceptability criteria for DLCO testing?
- Adequate inspiratory volume (>90% of the largest VC)
- Inhalation of > 85% of the test gas in 4 seconds
- Stable breath hold for 10 seconds with no leak
- Sample collection within 4 seconds of exhalation
What are the repeatability criteria for DLCO testing?
- 2 acceptable maneuvers within 2ml/min/mmHg
- should do at least 2 maneuvers and average results
What adjustments are made to predicted value of DLCO prior to interpretation?
1) Hemoglobin
2) Carboxyhemoglobin and CO back pressure (COHb can affect binding sites and CO also reduces the driving pressure for CO transport from alveoli to capillary)
* 2% decrease in DLCO for each 1% increase in COHb
3) Barometric Pressure: as BP decreases, the PiO2 decreases and DLCO increases (0.53% increase in DLCO for every 100m in increase in altitude)
3 Lung function test options for Sedated Infants
1) Raised-volume rapid thoracoabdominal compression (RVRTC) technique
2) Infant Pleth
3) Multiple breath washout = LCI
5 Lung function test options for Preschoolers
1) Spirometry
2) Pleth (specific airway resistance = sRaw)
3) Interrupter resistance technique (= Rint)
4) Forced oscillation technique (FOT)
5) Multiple breath washout = LCI
Equation for lung clearance index
Cumulative expired volume/FRC
Volume when concentration falls below 1/40th of original
Which lung disease as infant RVRTC been shown to be helpful in predicting early disease?
CF
What is the most accurate method for detecting early lung disease in preschoolers?
LCI
(LCI > sRaw > spirometry)
*recommendation - 25% decrease in sRaw as cut-off for asthma in young children
What are the 3 major roles for any lung function test?
1) Monitor disease severity over time
2) Evaluate response to treatment
3) Serve as objective outcome measures in clinical research studies
What are developmental differences in preschoolers vs older children regarding their ability
1) FEV1/FVC ratio is 90-95% in 5-6 year olds and even higher in young children
2) Utility in FEV1 in older children is due to its location on the effort-independent part of the curve
3) Unlikely that preschool children will not have the respiratory muscle strength to maintain flow limitation to lung volumes as low as 85-90%
What is the most useful lung function test for preschoolers with CF?
Lung Clearance Index
Spirometry recommendations for preschoolers (13)
1) Live flow-volume curves
2) Review FVC, FEV1, VBE, point when flow ceases as proportion of PEF
3) Acclimatize child to equipment and lab
4) Flow and Volume-driven incentives may be useful
5) Posture and nose-clip use should be recorded
6) Make sure no leak
7) Minimum 3 maneuvers, no max
8) Inspect curves for rapid rise to peak flow and smooth descent without cough or glottic closure
9) if VBE > 80mls or 12.5% FEV1 - inspect curve but dont always reject
10) Premature termination = cessation of flow at >10% FVC (may use FEV1 but not FVC or ratios)
11) Report highest FEV1 and FVC
12) starting point for FEV1 determined from back extrapolation
13) At least 2 acceptable curves with FEV1 and FVC within 0.1L or 10% of highest value
2 ways to measure tidal volume?
- Tidal expiratory flow analysis
2. Thoraco-abdominal motion analysis
Maneuver for tidal expiratory flow analysis?
- Stable breathing in seated/standing position
- At least 30 seconds /10 tidal breaths
- Report mean, SD, coefficient of variability
- inspect Flow volume curve for repeatability and flow-time to ensure steady tidal breathing
*Flow at the airway determined by driving pressure and resistance (F = P/R)
P determined by elastic recoil of the respiratory system and net pressure due to respiratory muscle activity
*Those with wheezing with have increased Time to Peak tidal expiratory flow/total expiratory time AND increased Volume at peak tidal expiratory flow/expired tidal volume (both decrease with ventolin)
Maneuvers involved in Thoraco-Abdominal Motion Analysis
With increasing negative intrathoracic pressure, rib cage lags behind abdomen and may even more inwards initially
- Measure with child seated, with mouthpiece
- Occlusion with valve closing in <10ms and for <100 ms
- Occlusion triggered by PEF in expiration
- Record 10 occlusions to get 5 acceptable maneuvers
- Report median
*During sudden occlusion, alveolar P will rapidly equilibrate with P at the mouth (Pmo)
Rint = Pmo/flow
Principles of Forced Oscillation Technique
External pressure wave applied at the mouth
Resulting pressure-flow pattern is analyzed in terms of respiratory impedance
Procedure for Forced Oscillation Technique
- System should be able to measure a reference impedance of >1.5 kPa.s/L within 10% of <0.1L
- Excitation frequency = 4-8 Hz
- Child is seated, breathing through mouthpiece with noseclips
- Acquisition over several breathing cycles, typically 8-16
- 3-5 measurements
- Mean reported as well as SD and CV
Point of doing Multiple Breath Washout Test
Assesses ventilation distribution and FRC
Procedure for Multiple Breath Washout Test
- child seated upright with mouthpiece or sealed facemark
- Deadspace = <1-2ml/kg
- Sufficiently long wash-in to allow gas to equilibrate in lung - usually 10s after inspired/expired concentrations are equal
- Washout continues until end-tidal concentration = 1/40th starting concentration, over 3 breaths
- Watch Vt and gas concentration to detect for any leaks
- FRC and indices of ventilation inhomogeneity should be calculated on each washout. Mean values, with different <10% from 2 washouts can be reported
- LCI = cumulative expired volume, minus dead space times number of breaths divided by FRC
Procedure for Bronchial Responsiveness Tests in Preschoolers
- Perform in children who are free from respiratory infection (>3 weeks), normal auscultation and PFTs including sat > 95%
- Agent should be delivered by tidal breathing (standard nebulizer output for 2 min) or dosimeter method (deep inhalation, nebulization 0.6 seconds, repeated every 5 min)
- if transcut pp O2 used - change >20%
- Avoid SpO2 as a sole marker of bronchoconstriction
- An increase in resistance of up to 35-40% = negative test
- Test should be ended with bronchodilator and confirmation that PFT is at baseline
For DMD, what is the best negative predictor of survival?
FVC <1L
What is considered to be ineffective airway clearance?
Peak cough flow <160L/min
MEP <45 cm H20
According to ATS, what values would benefit from assisted cough techniques?
Peak cough flow <270L/s
MEP <60 cm H20
*CDC: FVC <40%
BTS: peak cough flow <270 L/s
When should you offer nocturnal NIV to DMD patients?
Awake PaCO2 >45
O2 sat <92-95%
FVC <30-40%
When should you consider daytime NIV to DMD patients?
Daytime PaCO2 >50 or O2 sat <92%
What is the worry about providing oxygen to DMD patients?
Can mask underlying cause and they may lose their hypoxic drive to breathe
At what FVC is the prognosis for recovery from scoliosis surgery best?
FVC >40%
What should the extubation protocol for DMD kids include?
Airway clearance techniques
Immediate use of NIV following extubation
Indications for tracheostomy in DMD?
patient and family preference
cannot tolerate NIV
medical infrastructure can’t support NIV
3 failures to achieve extubation despite NIV and cough assist
Failure of cough assist to prevent aspiration of secretions
Gene for CCHS
Phox2B
“Paired like homeobox”
Inheritance pattern for CCHS
Autosomal dominant
Mosaicism in 5-10%
De novo mutations (most = de novo unless parents are affected)
Clinical picture of CCHS
Reduced tidal volumes, monotonous respiratory rates awake and asleep
More profound hypoventilation occurs with sleep
Often become hypoxic and hypercarbic
Lack responsiveness to the physiologic changes and often do not arouse
Lack perception of asphyxia during wakefulness (and exertion)
Aspects of autonomic dysregulation in CCHS
Hirschsprungs Neural crest tumours Reduced pupillary light response Esophageal dysmotility Breath holding spells Reduced basal temperature Sporadic profuse sweating Lack of perception to dyspnea Altered response to exercise challenge and environmental stressors
Mutations on PHOX2B that play a role in CCHS
Two polyalanine repeat regions in exon 3 - SECOND one is important!
Normal = 20 alanines
either PARM or NPARM mutations (NPARM worse)
Affected individuals have more polyalanines in this sequence (24-33)
**Most common = 20/25, 20/26, 20/27
How many patients have NPARM mutations in CCHS?
10%
Are PARM or NPARM mutations worse in CCHS?
NPARM
- Includes sequence changes outside of the polyalanine repeat and can cause frameshift variants
- Typically more severe phenotypes
Phenotypes with increased risk if you have NPARM mutation in CCHS
Continuous ventilatory support
Hirschsprungs
Neural crest tumours
Phenotypes with increased risk if you have PARM mutation in CCHS
Neural crest tumours (20/29-20/33)
Autonomic nervous system dysregulation
What is the theory behind later onset CCHS?
likely a reflection of variable penetrance of the 20/24 and 20/25 mutations or NPARM with environmental cofactor
Evaluation for CCHS
- H&P (including response to sedation/anesthesia and delayed recovery, unexplained seizures and neurocognitive impairment)
- Review photographs for facial dysmorphology
- 72 hour holter for investigation of prolonged sinus pauses
- PSG for ventilation impairment
- Hematocrit and reticulocyte count (polycythemia and response to hypoxemia)
- Bicarb level
- CXR, echo, or ECG (pulmonary HTN)
- Barium enema or manometry in cases of constipation
What disease is important to distinguish from CCHS?
ROHHAD-NET
Presents with rapid obesity, hypothalamic disorders, OSA, hypoventilation, autonomic dysregulation
Recurrence rates for CCHS
50% of transmitting it if affected parents
50% chance of recurrence with unaffected mosaic parents
Mechanism of PARM in CCHS
regarded as flexible spacer elements essential to conformation, protein-protein interaction and DNA binding
Mechanism of PHOX2B mutations in CCHS
Typically responsible for expression regulation of genes involved in the development of the ANS
Diagnosis and clinical course for CCHS
1) Need to send for PHOX2B screening test for diagnosis. Rule out other causes of hypoventilation + other lung disease muscle weakness, cardiac disease
2. Investigations for Hirschsprungs
3. Serial chest and abdo imaging essential for PARM and NPARM with 20/29-20/33
4. Annual 72 hour holter for abhorrent cardiac rhythms
5. Annual echo, hematocrit, reticulocyte count (at risk for PH)
6. Ophthalmologic evaluation
7. Reported to have decreased school performance - neurocognitive test annually
8. Biannual then annual comprehensive physiologic studies to assess ventilatory needs
What is the hallmark of CCHS?
Alveolar hypoventilation
- *Diminished tidal volume and minute ventilation is most easily seen in non-REM sleep but also abnormal in REM and wakefulness
- *Need for ventilatory support tied to PARM mutations (worse with more PARM >20/27) and NPARMs
Options for ventilatory management in CCHS
Trach
BiPAP
Negative pressure ventilators
Diaphragmatic pacing
Problem with diaphragmatic pacing?
Will be picked up in ECG so may artificially elevate HR and hide the sinus pauses
Should kids with CCHS swim?
NO!
Prohibited from underwater swimming as they won’t perceive asphyxia that occurs with drowning and breath holding
Is NIV optimal management in CCHS?
No
*Considered after 6-8 years
What form of ventilation is recommended for CCHS especially in the first few years?
Trach
**Portable postive pressure ventilator via trach = most common method of providing home ventilation
**Must have power generator and placement on emerge list for local power company and fire dept
4 signs that a trach needs upsizing
- Difficulty achieving adequate gas exchange and plateau on ETCO2
- Increasing ventilator settings to those above other similar aged children
- More frequent pneumonia
- Audible leak
*Bronch q12-24 months for assessment
Recommendation for BiPAP in CCHS
Can be used via nasal mask, prongs or facemark (but discouraged)
Provide continuous flow with fixed leak
Can adjust pressure accordingly
Should not be used outside of sleep - interferes with activity, skin breakdown, mid face hypoplasia
Recommendation for Negative Pressure Ventilation in CCHS
- Many children still need a trach
- Not portable
- Requires supine position
- Causes skin irritation and a “chilled” sensation
- Possible when older (6-8)
Mechanism for Diaphragmatic Pacing in CCHS
- Generates respiratory rate using the diaphragm
- Uses battery operated external transmitter sent via antenna with a radio signal sent to subcutaneous bilateral receiver - generates an electrical impulse which stimulates a breath
**Can give 12-15 hours of support
If needing 24 hours - need a second method of ventilation for part of the day
MUST have backup support
OSA may be a complication *dyssynchrony with the upper airway muscles
Optimal CCHS candidates for Diaphragmatic pacing
No or mild lung disease
Not obese
Intact phrenic nerve/diaphragm integrity
Needs tracheostomy initially
Lifestyle recommendations for CCHS
No alcohol or drug use
Be careful with pregnancy - increases respiratory load, decreases minute ventilation and central drive
Low mortality for those managed aggressively
Most children have prolonged survival with good quality of life
2 techniques for Multiple Breath Washout
1) Nitrogen
2) SF6
Explain how nitrogen washout works
1) RA in (nitrogen ~80%)
2) Washout: 100% O2
Done with N2 < 1.5% x 3 breaths
Cheapest and most commonly used
No wash-in needed
Intert but “intrinsic” gas - lungs excrete nitrogen
Explain how SF6 washout works
1) Wash-in: SF6 with 21% O2 - to 4%
2) Washout: RA (open circuit)
“Extrinsic”, not produced by the lungs
Easier detection
Disadvantages: greenhouse gas, expensive, longer wash-in period
Equation for Lung Clearance Index
(Cumulation expired volume to reach 1/40th gas)/FRC
What does LCI measure?
Measures ventilation homogeneity
Higher LCI = more lung inhomogeneity
Healthy = ~7 (5.7-7.7), age-dependent
Decreases in 1st 2 years of life - plateaus (toddler) - then increases
Can be normal in atelectasis/complete obstruction
Main application = CF
What are the 3 2019 End of Forced Expiration criteria for spirometry? (Need 1 of these)
- Expiratory plateau ≤ 0.025L/s in the last second
- Expiratory time > 15 seconds
- FVC within repeatability tolerance
> 6yr: ≤ 0.150L between 2 highest values for FVC and FEV1
<6yr: ≤ 0.100L or 10%
Activities to avoid before lung function testing
- Smoking +/- vaping +/- water per use within 1 hr
- Consuming intoxicants within 8 hr before testing
- Performing vigorous exercise within 1 hour before testing
- Wearing clothing that substantially restricts full chest and abdominal expansion
According to Canadian TB guidelines, who are the most affected populations in Canada for TB?
Canadian-born aboriginals
Foreign-born individuals
Disproportionate number of incident cases in North
Most common TB disease site
Pulmonary 64%
Peripheral lymph nose second most common 13%
Almost all cases culture confirmed (80%)
What is the most common co-infection with TB?
HIV