Effects of continuous positive airway pressure breathing on lung volume and distensibility

1990 ◽  
Vol 68 (3) ◽  
pp. 1121-1126 ◽  
Author(s):  
C. J. Duggan ◽  
W. D. Castle ◽  
N. Berend
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Transpulmonary Pressure ◽  
Normal Subjects ◽  
Small Degree ◽  
Elastic Behavior ◽  
Base Line ◽  
Upward Shift ◽  
Alveolar Duct

In this study the effects on lung elastic behavior of 10 min of breathing at a continuous positive airway pressure (CPAP) of 10 cmH2O were examined in 10 normal subjects. To investigate whether any changes were induced by release of prostaglandins, the subjects were also pretreated with the cyclooxygenase inhibitor indomethacin. CPAP produced a significant (P less than 0.001) upward shift of the pressure-volume (PV) curve [change in total lung capacity (delta TLC) 374 +/- 67 (SE) ml, mean delta volume at a transpulmonary pressure of 15 cmH2O (delta VL15) 279 +/- 31 ml] with no change in K, an index of lung distensibility. After CPAP the PV curves returned to normal base line within 20 min. The same pattern was observed after indomethacin, but the increase in TLC was significantly less (P less than 0.01) (mean delta TLC 206 +/- 42 ml) mainly because of a slight and not statistically significant increase in base-line TLC. In five subjects further PV curves with and without CPAP were obtained greater than or equal to 7 days after indomethacin. The responses were not significantly different from those obtained before indomethacin (mean delta TLC 366 +/- 89, mean delta VL15 296 +/- 42 ml). We conclude that CPAP produces an upward shift of the PV curve without a change in lung distensibility. In addition, there may be a small degree of resting alveolar duct tone that is influenced by indomethacin.

Positive airway pressure and vertical transpulmonary pressure gradient in man

1975 ◽  
Vol 38 (5) ◽  
pp. 896-899 ◽  
Author(s):  
K. Rehder ◽  
N. Abboud ◽  
J. R. Rodarte ◽  
R. E. Hyatt
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Pressure Gradient ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Transpulmonary Pressure ◽  
Vertical Gradient ◽  
Normal Subjects ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Consistent Change

Static transpulmonary pressure (Pao-Pes) and the vertical gradient of transpulmonary pressure were determined in five sitting conscious normal subjects at mean airway pressures of 0 (ambient), 11, and 21 cmH2O. All subjects exhibited a nonuniform transpulmonary pressure gradient down the esophagus. The vertical pressure gradient was consistently larger in the lower (8–20cm below esophageal artifact) than in the middle region (0–8cm) of the esophagus. The gradient was not significantly altered by continuous positive airway pressure (11 and 21 cmH2O) or by changes in lung volume (60, 70, and 80% of total lung capacity (TLC)). Continuous positive airway pressure also did not result in a consistent change of the overall static pressure-volume curve of the lung. There was a small but statistically significant increase in TLC with each increase in airway pressure.

Haemodynamic Effects of Continuous Positive Airway Pressure in Humans with Normal and Impaired Left Ventricular Function

1995 ◽  
Vol 88 (2) ◽  
pp. 173-178 ◽  
Author(s):  
Alberto De Hoyos ◽  
Peter P. Liu ◽  
Dean C. Benard ◽  
T. Douglas Bradley
Keyword(s):  
Heart Failure ◽  
Continuous Positive Airway Pressure ◽  
Stroke Volume ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Normal Subjects ◽  
Left Ventricular ◽  
Pulmonary Capillary ◽  
Patients With Heart Failure ◽  
Ventricular Filling

1. Continuous positive airway pressure increases intrathoracic pressure, thereby decreasing left ventricular preload and afterload. We hypothesized that there would be a dose-related alteration in cardiac and stroke volume indices in response to continuous positive airway pressure in normal subjects and patients with congestive heart failure and that the direction of response among those with heart failure would be related to left ventricular preload. 2. Cardiac and stroke volume indices were measured at baseline and after 10 min of continuous positive airway pressure at both 5 and 10 cmH2O (0.5 and 0.99 kPa respectively) in 16 patients with heart failure and five control subjects with normal cardiac function. Among the eight patients with heart failure and elevated pulmonary capillary wedge pressure (≧12 mmHg) (≦ 1.6 kPa), cardiac index increased from 2.47 ± 0.34 at baseline to 2.91 ± 0.32 to 3.12 ± 0.40 l min−1 m−2 (P < 0.025) while on 5 and 10 cm H2O of continuous positive airway pressure respectively. In the same patients stroke volume index increased from 27.8 ± 3.9 to 33.9 ± 4.2 to 36.8 ± 5.5 ml/m2 (P < 0.05). In contrast, in both the control subjects and patients with heart failure and normal pulmonary capillary wedge pressure (< 12 mmHg) there was a dose-related decrease in cardiac and stroke volume indices while on continuous positive airway pressure. 3. Continuous positive airway pressure causes dose-related increases in cardiac and stroke volume indices among patients with chronic heart failure and elevated left ventricular filling pressure. However, it induces dose-related reductions in cardiac and stroke volume indices among normal subjects as well as patients with heart failure and normal left ventricular filling pressures.

The acute impact of continuous positive airway pressure on nasal resistance: a randomized controlled comparison

2007 ◽  
Vol 102 (3) ◽  
pp. 1214-1219 ◽  
Author(s):  
Stephanie Willing ◽  
Maybelle San Pedro ◽  
Helen S. Driver ◽  
Peter Munt ◽  
Michael F. Fitzpatrick
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Normal Subjects ◽  
Acute Effect ◽  
Nasal Symptom ◽  
Nasal Resistance ◽  
Randomized Controlled ◽  
Before And After ◽  
Peak Nasal Inspiratory Flow

Subjective nasal obstruction is common among users of continuous positive airway pressure (CPAP). The aim of this study was to measure the acute effect of CPAP on nasal resistance and nasal symptoms in awake normal subjects. Twenty-four healthy CPAP-naive adults [8 men, 16 women; mean age 30 yr (SD 14)] underwent a randomized controlled crossover study comparing nasal CPAP (8 cmH2O) for 6 h on one occasion and the control condition (nasal mask without CPAP) on the other. Nasal resistance measurements (posterior active rhinometry) before and after the test exposure were similar on both test days. Nasal resistance during CPAP exposure [2.04 cmH2O·l−1·s (SD 0.72)] was significantly lower than that of the control [2.67 cmH2O·l−1·s (SD 1.07)]: mean difference 0.66 cmH2O·l−1·s, 95% confidence interval 0.19–1.13 cmH2O·l−1·s. The gradient in pressure from CPAP mask to posterior naris during CPAP exposure varied from 1.6 to 2 cmH2O but was not significantly different between time points. Subjective nasal symptom scores and peak nasal inspiratory flow rates did not change significantly on either test day. We conclude that in awake CPAP-naive normal subjects, acute CPAP exposure is associated with a reduction in nasal resistance compared with the control condition, but it is not associated with an immediate post-CPAP change in subjective or objective nasal resistance.

Inductance plethysmography measurement of CPAP-induced changes in end-expiratory lung volume

1990 ◽  
Vol 68 (4) ◽  
pp. 1732-1738 ◽  
Author(s):  
J. L. Werchowski ◽  
M. H. Sanders ◽  
J. P. Costantino ◽  
F. C. Sciurba ◽  
R. M. Rogers
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Tidal Volume ◽  
Lung Volume ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Normal Subjects ◽  
Residual Capacity ◽  
Highly Correlated ◽  
Induced Changes ◽  
Spontaneously Breathing

The respiratory inductance plethysmograph (RIP) has recently gained popularity in both the research and clinical arenas for measuring tidal volume (VT) and changes in functional residual capacity (delta FRC). It is important however, to define the likelihood that individual RIP measurements of VT and delta FRC would be acceptably accurate (+/- 10%) for clinical and investigational purposes in spontaneously breathing individuals on continuous positive airway pressure (CPAP). Additionally, RIP accuracy has not been compared in these regards after calibration by two commonly employed techniques, the least squares (LSQ) and the quantitative diagnostic calibration (QDC) methods. We compared RIP with pneumotachographic (PTH) measurements of delta FRC and VT during spontaneous mouth breathing on 0-10 cmH2O CPAP. Comparisons were made after RIP calibration with both the LSQ (6 subjects) and QDC (7 subjects) methods. Measurements of delta FRC by RIPLSQ and RIPQDC were highly correlated with PTH measurements (r = 0.94 +/- 0.04 and r = 0.98 +/- 0.01 (SE), respectively). However, only an average of 30% of RIPQDC determinations per subject and 31.4% of RIPLSQ determinations per subject were accurate to +/- 10% of PTH values. An average of 55.2% (QDC) and 68.8% (LSQ) of VT determinations per subject were accurate to +/- 10% of PTH values. We conclude that in normal subjects, over a large number of determinations, RIP values for delta FRC and VT at elevated end-expiratory lung volume correlate well with PTH values. However, regardless of whether QDC or LSQ calibration is used, only about one-third of individual RIP determinations of delta FRC and one-half of two-thirds of VT measurements will be sufficiently accurate for clinical and investigational use.

Changes in upper airway resistance with lung inflation and positive airway pressure

1990 ◽  
Vol 68 (3) ◽  
pp. 1075-1079 ◽  
Author(s):  
F. Series ◽  
Y. Cormier ◽  
J. Couture ◽  
M. Desmeules
Keyword(s):  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Upper Airway ◽  
Normal Subjects ◽  
Base Line ◽  
Upper Airways ◽  
Airway Patency ◽  
Lung Inflation ◽  
Bias Flow ◽  
Expiratory Positive Airway Pressure

The influence of pulmonary inflation and positive airway pressure on nasal and pharyngeal resistance were studied in 10 normal subjects lying in an iron lung. Upper airway pressures were measured with two low-bias flow catheters while the subjects breathed by the nose through a Fleish no. 3 pneumotachograph into a spirometer. Resistances were calculated at isoflow rates in four different conditions: exclusive pulmonary inflation, achieved by applying a negative extra-thoracic pressure (NEP); expiratory positive airway pressure (EPAP), which was created by immersion of the expiratory line; continuous positive airway pressure (CPAP), realized by loading the bell of the spirometer; and CPAP without pulmonary inflation by simultaneously applying the same positive extrathoracic pressure (CPAP + PEP). Resistance measurements were obtained at 5- and 10-cmH2O pressure levels. Pharyngeal resistance (Rph) significantly decreased during each measurement; the decreases in nasal resistance were only significant with CPAP and CPAP + PEP; the deepest fall in Rph occurred with CPAP. It reached 70.8 +/- 5.5 and 54.8 +/- 6.5% (SE) of base-line values at 5 and 10 cmH2O, respectively. The changes in lung volume recorded with CPAP + PEP ranged from -180 to 120 ml at 5 cmH2O and from -240 to 120 ml at 10 cmH2O. Resistances tended to increase with CPAP + PEP compared with CPAP values, but these changes were not significant (Rph = 75.9 +/- 6.1 and 59.9 +/- 6.6% at 5 and 10 cmH2O of CPAP + PEP). We conclude that 1) the upper airway patency increases during pulmonary inflation, 2) the main effect of CPAP is related to pneumatic splinting, and 3) pulmonary inflation contributes little to the decrease in upper airways resistance observed with CPAP.

Effect of raised thoracic pressure and volume on 99mTc-DTPA clearance in humans

1986 ◽  
Vol 60 (5) ◽  
pp. 1493-1497 ◽  
Author(s):  
K. B. Nolop ◽  
D. L. Maxwell ◽  
D. Royston ◽  
J. M. Hughes
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
High Volume ◽  
Solute Flux ◽  
Positive Pressure ◽  
Base Line ◽  
Half Time ◽  
The Mean ◽  
Low Volume

Although positive airway pressure is often used to treat acute pulmonary edema, the effects on epithelial solute flux are not well known. We measured independently the effect of 1) positive pressure and 2) voluntary hyperinflation on the clearance of inhaled technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA) in six nonsmokers and six smokers. Lung volumes were monitored by inductance plethysmography. Each subject was studied in four situations: 1) low end-expiratory volume (LO-), 2) low volume plus 9 cmH2O continuous positive airway pressure (LO+), 3) high end-expiratory volume (HI-), and 4) high volume plus continuous positive airway pressure (HI+). The clearance half time of 99mTc-DTPA for the nonsmokers decreased from 64.8 +/- 7.0 min (mean +/- SE) at LO- to 23.2 +/- 5.3 min at HI- (P less than 0.05). Positive pressure had no synergistic effect. The mean clearance half time for the smokers was faster than nonsmokers at base line but unaffected by similar changes in thoracic volume and pressure. We conclude that, in nonsmokers, positive airway pressure increases 99mTc-DTPA clearance primarily through an increase in lung volume and that smokers are immune to these effects.

Continuous Positive Airway Pressure (CPAP) Therapy for the Treatment of Hypernasality: A Single Case Study

2014 ◽  
Vol 24 (2) ◽  
pp. 48-58 ◽  
Author(s):  
Lakshmi Kollara ◽  
Graham Schenck ◽  
Jamie Perry
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Single Case ◽  
Treatment Method ◽  
Post Treatment ◽  
Subjective Perception ◽  
Cpap Therapy ◽  
Long Term Follow Up

Studies have investigated the applications of Continuous Positive Airway Pressure (CPAP) therapy in the treatment of hypernasality due to velopharyngeal dysfunction (VPD; Cahill et al., 2004; Kuehn, 1991; Kuehn, Moon, & Folkins, 1993; Kuehn et al., 2002). The purpose of this study was to examine the effectiveness of CPAP therapy to reduce hypernasality in a female subject, post-traumatic brain injury (TBI) and pharyngeal flap, who presented with signs of VPD including persistent hypernasality. Improvements in mean velopharyngeal orifice size, subjective perception of hypernasality, and overall intelligibility were observed from the baseline to 8-week post-treatment assessment intervals. Additional long-term assessments completed at 2, 3, and 4 months post-treatment indicated decreases in immediate post-treatment improvements. Results from the present study suggest that CPAP is a safe, non-invasive, and relatively conservative treatment method for reduction of hypernasality in selected patients with TBI. More stringent long-term follow up may indicate the need for repeated CPAP treatment to maintain results.

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