Limits...
Testing limits to airflow perturbation device (APD) measurements.

Lopresti ER, Johnson AT, Koh FC, Scott WH, Jamshidi S, Silverman NK - Biomed Eng Online (2008)

Bottom Line: This was not statistically significant.Larger leaks given by 4.8 and 6.4 mm tubes reduced measurements significantly (3.4 and 3.0 cm cmH2O.sec/L, respectively).Although breathing through a 52 cm length of flexible ventilator tubing reduced the APD measurement from 4.0 cm H2O.sec/L for the control to 3.6 cm H2O.sec/L for the tube, the difference was not statistically significant.

View Article: PubMed Central - HTML - PubMed

Affiliation: Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA. erikalopresti@yahoo.com

ABSTRACT

Background: The Airflow Perturbation Device (APD) is a lightweight, portable device that can be used to measure total respiratory resistance as well as inhalation and exhalation resistances. There is a need to determine limits to the accuracy of APD measurements for different conditions likely to occur: leaks around the mouthpiece, use of an oronasal mask, and the addition of resistance in the respiratory system. Also, there is a need for resistance measurements in patients who are ventilated.

Method: Ten subjects between the ages of 18 and 35 were tested for each station in the experiment. The first station involved testing the effects of leaks of known sizes on APD measurements. The second station tested the use of an oronasal mask used in conjunction with the APD during nose and mouth breathing. The third station tested the effects of two different resistances added in series with the APD mouthpiece. The fourth station tested the usage of a flexible ventilator tube in conjunction with the APD.

Results: All leaks reduced APD resistance measurement values. Leaks represented by two 3.2 mm diameter tubes reduced measured resistance by about 10% (4.2 cmH2O.sec/L for control and 3.9 cm H2O.sec/L for the leak). This was not statistically significant. Larger leaks given by 4.8 and 6.4 mm tubes reduced measurements significantly (3.4 and 3.0 cm cmH2O.sec/L, respectively). Mouth resistance measured with a cardboard mouthpiece gave an APD measurement of 4.2 cm H2O.sec/L and mouth resistance measured with an oronasal mask was 4.5 cm H2O.sec/L; the two were not significantly different. Nose resistance measured with the oronasal mask was 7.6 cm H2O.sec/L. Adding airflow resistances of 1.12 and 2.10 cm H2O.sec/L to the breathing circuit between the mouth and APD yielded respiratory resistance values higher than the control by 0.7 and 2.0 cm H2O.sec/L. Although breathing through a 52 cm length of flexible ventilator tubing reduced the APD measurement from 4.0 cm H2O.sec/L for the control to 3.6 cm H2O.sec/L for the tube, the difference was not statistically significant.

Conclusion: The APD can be adapted for use in ventilated, unconscious, and uncooperative patients with use of a ventilator tube and an oronasal mask without significantly affecting measurements. Adding a resistance in series with the APD mouthpiece has an additive effect on resistance measurements, and can be used for qualitative calibration. A leak size of at least the equivalent of two 3.2 mm diameter tubes can be tolerated without significantly affecting APD measurements.

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Picture of the oronasal mask used to measure nasal, mouth, and nasal plus mouth resistances. This mask was attached to the APD through a regular cardboard mouthpiece that fits over the pneumotach entrance.
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Figure 3: Picture of the oronasal mask used to measure nasal, mouth, and nasal plus mouth resistances. This mask was attached to the APD through a regular cardboard mouthpiece that fits over the pneumotach entrance.

Mentions: Next, the subject moved to Station 2 where the oronasal mask was used (Adult Mask 4–5+; Laerdal Medical; Wappingers Falls, NY). Four measurements were taken at this station. The first measurement used the control mouthpiece. For the second measurement, the oronasal mask was placed over the mouth and nose, and the subject wore a nose clip so that breathing occurred only through the mouth. A control mouthpiece was taped to the exit of the mask so that it would fit on the mouthpiece of the APD (Figure 3). A third measurement was taken while the subject was wearing the mask, but no nose clip was worn. Finally, a measurement was taken where the subject's mouth was closed and breathing occurred only through the nose.


Testing limits to airflow perturbation device (APD) measurements.

Lopresti ER, Johnson AT, Koh FC, Scott WH, Jamshidi S, Silverman NK - Biomed Eng Online (2008)

Picture of the oronasal mask used to measure nasal, mouth, and nasal plus mouth resistances. This mask was attached to the APD through a regular cardboard mouthpiece that fits over the pneumotach entrance.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2600779&req=5

Figure 3: Picture of the oronasal mask used to measure nasal, mouth, and nasal plus mouth resistances. This mask was attached to the APD through a regular cardboard mouthpiece that fits over the pneumotach entrance.
Mentions: Next, the subject moved to Station 2 where the oronasal mask was used (Adult Mask 4–5+; Laerdal Medical; Wappingers Falls, NY). Four measurements were taken at this station. The first measurement used the control mouthpiece. For the second measurement, the oronasal mask was placed over the mouth and nose, and the subject wore a nose clip so that breathing occurred only through the mouth. A control mouthpiece was taped to the exit of the mask so that it would fit on the mouthpiece of the APD (Figure 3). A third measurement was taken while the subject was wearing the mask, but no nose clip was worn. Finally, a measurement was taken where the subject's mouth was closed and breathing occurred only through the nose.

Bottom Line: This was not statistically significant.Larger leaks given by 4.8 and 6.4 mm tubes reduced measurements significantly (3.4 and 3.0 cm cmH2O.sec/L, respectively).Although breathing through a 52 cm length of flexible ventilator tubing reduced the APD measurement from 4.0 cm H2O.sec/L for the control to 3.6 cm H2O.sec/L for the tube, the difference was not statistically significant.

View Article: PubMed Central - HTML - PubMed

Affiliation: Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA. erikalopresti@yahoo.com

ABSTRACT

Background: The Airflow Perturbation Device (APD) is a lightweight, portable device that can be used to measure total respiratory resistance as well as inhalation and exhalation resistances. There is a need to determine limits to the accuracy of APD measurements for different conditions likely to occur: leaks around the mouthpiece, use of an oronasal mask, and the addition of resistance in the respiratory system. Also, there is a need for resistance measurements in patients who are ventilated.

Method: Ten subjects between the ages of 18 and 35 were tested for each station in the experiment. The first station involved testing the effects of leaks of known sizes on APD measurements. The second station tested the use of an oronasal mask used in conjunction with the APD during nose and mouth breathing. The third station tested the effects of two different resistances added in series with the APD mouthpiece. The fourth station tested the usage of a flexible ventilator tube in conjunction with the APD.

Results: All leaks reduced APD resistance measurement values. Leaks represented by two 3.2 mm diameter tubes reduced measured resistance by about 10% (4.2 cmH2O.sec/L for control and 3.9 cm H2O.sec/L for the leak). This was not statistically significant. Larger leaks given by 4.8 and 6.4 mm tubes reduced measurements significantly (3.4 and 3.0 cm cmH2O.sec/L, respectively). Mouth resistance measured with a cardboard mouthpiece gave an APD measurement of 4.2 cm H2O.sec/L and mouth resistance measured with an oronasal mask was 4.5 cm H2O.sec/L; the two were not significantly different. Nose resistance measured with the oronasal mask was 7.6 cm H2O.sec/L. Adding airflow resistances of 1.12 and 2.10 cm H2O.sec/L to the breathing circuit between the mouth and APD yielded respiratory resistance values higher than the control by 0.7 and 2.0 cm H2O.sec/L. Although breathing through a 52 cm length of flexible ventilator tubing reduced the APD measurement from 4.0 cm H2O.sec/L for the control to 3.6 cm H2O.sec/L for the tube, the difference was not statistically significant.

Conclusion: The APD can be adapted for use in ventilated, unconscious, and uncooperative patients with use of a ventilator tube and an oronasal mask without significantly affecting measurements. Adding a resistance in series with the APD mouthpiece has an additive effect on resistance measurements, and can be used for qualitative calibration. A leak size of at least the equivalent of two 3.2 mm diameter tubes can be tolerated without significantly affecting APD measurements.

Show MeSH
Related in: MedlinePlus