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PubMed1998

Sleep in patients with chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease (COPD) become hypoxemic during sleep, particularly during rapid eye movement (REM) sleep. Those who are most hypoxemic when awake experience the most severe hypoxemia during sleep. The major cause of REM hypoxemia is hypoventilation, with additional contributions from alteration in ventilation/perfusion matching and functional residual capacity (FRC) reduction. REM hypoxemia probably contributes to the development of pulmonary hypertension and polycythemia and may predispose to cardiac arrhythmias in some patients. The most effective form of therapy is nocturnal oxygen therapy, but the indications for the use of nocturnal oxygen therapy are entirely based on daytime oxygenation levels. Routine polysomnography is not indicated in patients with COPD but should be performed in patients who have symptoms suggestive of coexisting sleep apnea/ hypopnea syndrome.

Clinical Trials as Topic↗

PubMed1984

Effect of continuous positive airway pressure on lung mechanics during high-frequency jet ventilation.

Six mongrel dogs were studied in a body plethysmograph to ascertain the effects of continuous positive airway pressure (CPAP) during high-frequency jet ventilation (HFJV), using an open system allowing gas entrainment. Increases in CPAP significantly reduced tidal volume. Increases in HFJV and inspiratory fraction caused progressively larger increases in functional residual capacity (FRC). Higher levels of CPAP dramatically reduced HFJV's effect on FRC, but lower levels of CPAP augmented this effect. At constant CPAP, tidal volume correlated well with the difference between peak airway pressure and CPAP, while the FRC change was correlated with the difference between end-expiratory pressure and CPAP. The relationship between end-expiratory airway pressure and total change in FRC was predictable from lung compliance at all levels of CPAP.

Animals↗

PubMed1978

Effects of continuous positive airway pressure on pulmonary function and blood gases of infants with respiratory distress syndrome.

Nitrogen washout measurements and blood-gas analyses were made on 32 newborn infants with severe RDS at continuous positive airway pressures (CPAP) of 5, 10, and 15 cm H2O. Increases in airway pressure resulted in significant increases in PaO2 and functional residual capacity (FRC). It also produced significant decreases in alveolar turnover rates of the "fast" and "slow" alveolar spaces of a two-space lung model. Changes in CPAP did not significantly affect the distribution of ventilation. The changes in PaO2, due to changes in CPAP, did not correlate well with changes in FRC/wt nor with changes in alveolar turnover rates. Thus, the effects of increasing CPAP on PaO2 were not simply due to increases in FRC. The changes in PaO2 are due to a complex relationship between changes in FRC, alveolar turnover rates, and to other alterations in cardiopulmonary function that are yet to be fully understood.

Carbon Dioxide↗

PubMed1990

Auto-PEEP and dynamic hyperinflation in COPD patients during controlled mechanical ventilation and high frequency jet ventilation.

We investigated the levels of auto-PEEP and dynamic hyperinflation during high frequency jet ventilation (HFJV) and controlled mechanical ventilation (CMV) in six patients with chronic obstructive pulmonary disease within the first 36 h of acute exacerbation. The comparative evaluation was performed at similar conditions of gas exchange in HFJV and CMV: PaO2 77.6 +/- 11 mmHg vs 80.8 +/- 12 mmHg; PaCO2 46.8 +/- 2.5 mmHg vs 47 +/- 2.8 mmHg; pH 7.38 vs 7.38. In this situation, the values of auto-PEEP and dynamic hyperinflation, expressed as delta over the apneic functional residual capacity (FRC) did not differ: (auto-PEEPHFJV 8.9 +/- 3.8 cmH2O; auto-PEEPCMV 8.8 +/- 4.7 cmH2O; delta FRCHFJV 0.56 +/- 0.19 l; delta FRCCMV 0.54 +/- 0.2 l). This result suggests that, with a suitable machine setting and similar gas exchanges, HFJV produces the same level of auto-PEEP and dynamic hyperinflation as CMV in patients with chronic obstructive pulmonary disease.

Aged↗

PubMed1978

An alternative to breathing.

If carbon dioxide is removed by an extracorporeal membrane lung ventilated with room air, the natural lung can be used for oxygen transport alone; we have demonstrated this in lambs by maintaining lungs "inflated" with 100 percent oxygen at constant pressure and removing all carbon dioxide through the membrane lung. This process is a variant of "apneic oxygenation" without its disadvantages, because the arterial pH, PCO2, and PO2 all remain normal. No nitrogen washout is needed. These studies were carried out in five lambs anesthetized and paralyzed for 24 hours. For carbon dioxide removal, blood from the subclavin artery was pumped through an extracorporeal membrane lung and was returned into the external jugular vein. For oxygen delivery, the lungs were inflated through a tracheostomy tube with 100 percent oxygen to a pressure of 5 cm. H2O. There was no significant change in arterial blood PO2 after perfusion had begun or at the end of the perfusion 24 hours later. The arterial PCO2 remained steady, and there was no change in acid-base balance. The functional residual capacity (FRC) and static lung compliance remained unchanged. The total dead space was 10 to 15 ml. All animals recovered and survived in good health. At equilibrium, alveolar nitrogen partial pressure was always equal to the partial pressure of nitrogen in the ventilating gas of the membrane lung and was the sole determining factor in controlling alveolar oxygen concentration. Direct measurement of pulmonary gas showed alveolar gas at the level of the carina.

Animals↗

PubMed1983

Dysanaptic lung growth: an experimental and allometric approach.

The postnatal development of the mammalian lung, which at birth has only a fraction of the adult number of alveoli, would suggest a mismatch (dysanapsis) of the changes in airway size and lung size with growth. This may have implications on the efficiency of breathing because for any given lung size the dimensions of the airways are the determinant of the amount of dead space (VD) ventilation and of airflow resistance. A comparison of the allometric functions of tracheal dimensions previously published suggests that the tracheal volume, taken as representative of VD, is smaller in newborns than in adults. This difference becomes more apparent when examined per unit of functional residual capacity (VD/FRC). The relatively smaller tracheal volume is the result of both a shorter and narrower trachea in the newborn. This latter difference implies a slightly but significantly higher resistance of the lower airways, as also demonstrated by experimental measurements of peak expiratory flows at a constant driving pressure in rats of different ages. Because the slightly higher resistance of the lower airways is probably compensated by the smaller resistance of the upper airways (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51: 641-645, 1981), it would seem that the structure of the newborn mammalian lung favors the alveolar ventilatory function without a substantial increase of the energetic losses.

Age Factors↗

PubMed1997

Incentive spirometry performance. A reliable indicator of pulmonary function in the early postoperative period after lobectomy?

OBJECTIVES: The purpose of our study was to validate the incentive spirometry (IS) as a simple mean to follow pulmonary function at the bedside after lung surgery. MATERIALS AND METHODS: We studied prospectively 19 patients (16 men, 3 women; mean +/- SE age, 60 +/- 2.8 years) undergoing lobectomy for lung cancer. All the patients had an obstructive pattern with FEV1/FVC below 75%. Lung volumes, including functional residual capacity (FRC) and residual volume (RV), measured using spirometry and the helium dilution technique, and IS were measured preoperatively and postoperatively at days 1, 2, 3, and 8, and at 2 months. RESULTS: Our results showed that in the postoperative period after lung resection, IS performance was well correlated (R) during the first 8 postoperative days with vital capacity (VC) (R between 0.667 and 0.870) mainly due to the excellent correlation with the inspiratory reserve volume (IRV, R between 0.680 and 0.895) but was poorly correlated with expiratory reserve volume (R below 0.340), RV (R below 0.180), and FRC (R below 0.470). CONCLUSIONS: IS can be used as a simple mean to follow lung function, especially VC and IRV, in the postoperative period in spontaneously breathing patients. IS is noninvasive and can be performed repeatedly at the bedside in the intensive care setting.

Expiratory Reserve Volume↗

PubMed2003

Spinal stiffness changes throughout the respiratory cycle.

Posteroanterior stiffness of the lumbar spine is influenced by factors, including trunk muscle activity and intra-abdominal pressure (IAP). Because these factors vary with breathing, this study investigated whether stiffness is modulated in a cyclical manner with respiration. A further aim was to investigate the relationship between stiffness and IAP or abdominal and paraspinal muscle activity. Stiffness was measured from force-displacement responses of a posteroanterior force applied over the spinous process of L2 and L4. Recordings were made of IAP and electromyographic activity from L4/L2 erector spinae, abdominal muscles, and chest wall. Stiffness was measured with the lung volume held at the extremes of tidal volume and at greater and lesser volumes. Stiffness at L4 and L2 increased above base-level values at functional residual capacity (L2 14.9 N/mm and L4 15.3 N/mm) with both inspiratory and expiratory efforts. The increase was related to the respiratory effort and was greatest during maximum expiration (L2 24.9 N/mm and L4 23.9 N/mm). The results indicate that changes in trunk muscle activity and IAP with respiratory efforts modulate spinal stiffness. In addition, the diaphragm may augment spinal stiffness via attachment of its crural fibers to the lumbar vertebrae.

Abdomen↗

PubMed1998

Effects of positive end-expiratory pressure on oscillated flow rate during high-frequency chest compression.

OBJECTIVE: To investigate the effects of positive end-expiratory pressure (PEEP) on end-expiratory lung volume (EELV) and mean oscillated flow rate (VOSC) during high-frequency chest compression (HFCC) in normal subjects and patients with severe COPD. DESIGN: Comparative study. SETTING: Pulmonary function and lung mechanics laboratory, University of Alberta Hospitals. PARTICIPANTS: Six normal subjects (five male; one female) and six patients with clinically stable COPD (five male; one female) with hypercapnia. INTERVENTIONS: A pneumatic vest system was operated at 10 Hz with a mean chest wall pressure of 16 cm H2O to provide the HFCC. A closed-circuit spirometer system permitted measurement of HFCC- and PEEP-induced changes in EELV that were expressed as per cent baseline functional residual capacity (FRC). An isothermic chamber connected near the mouthpiece permitted measurement of VOSC. RESULTS: For the normal subjects, HFCC caused a significant decrease in EELV to 82.0% of FRC (p < or = 0.01) and the addition of 4.8+/-0.5 cm H2O of PEEP during HFCC increased EELV to 97.5% FRC. In the COPD patients, HFCC decreased EELV to 92.3% of FRC (p < or = 0.01), and the addition of 3.7+/-1.0 cm H2O of PEEP increased EELV to 98.4% FRC. For the normal subjects, increasing EELV to near FRC caused VOSC during expiration to increase 14.6% (p < or = 0.01), but there was no significant effect on VOSC during inspiration (5.1% increase). In the COPD patients, PEEP increased VOSC during both inspiration (30.5%) and expiration (57.0%) (both, p < or = 0.01). CONCLUSIONS: Addition of a modest amount of PEEP during HFCC prevents the decrease in EELV and increases VOSC during both phases of spontaneous breathing in COPD patients. This higher VOSC during HFCC+PEEP may improve the effectiveness of HFCC in clearing mucus from the lungs of patients with airway disease.

Adult↗

PubMed1975

Post-operative epidural analgesia: effects on lung volumes.

A study was undertaken to assess the role of post-operative pain in reducing Functional Residual Capacity (FRC) and Vital Capacity (VC). The efficacy of post-operative epidural analgesia in reversing these changes was measured in eight subjects after upper abdominal operations. With pain, FRC and VC were 78 per cent and 37 per cent of control respectively. Following epidural analgesia, the values were 84 per cent and 55 per cent. These figures indicate the pain component in the post-operative reduction of these two lung capacities. This partial restoration may be of value in the prevention of post-operative pulmonary complications by avoiding closure of small airways during tidal breathing and by increasing the effectiveness of deep breathing and coughing in the removal of secretions and the reversal of atelectasis.

Adult↗

PubMed1999

Lung elastic recoil during breathing at increased lung volume.

During dynamic hyperinflation with induced bronchoconstriction, there is a reduction in lung elastic recoil at constant lung volume (R. Pellegrino, O. Wilson, G. Jenouri, and J. R. Rodarte. J. Appl. Physiol. 81: 964-975, 1996). In the present study, lung elastic recoil at control end inspiration was measured in normal subjects in a volume displacement plethysmograph before and after voluntary increases in mean lung volume, which were achieved by one tidal volume increase in functional residual capacity (FRC) with constant tidal volume and by doubling tidal volume with constant FRC. Lung elastic recoil at control end inspiration was significantly decreased by approximately 10% within four breaths of increasing FRC. When tidal volume was doubled, the decrease in computed lung recoil at control end inspiration was not significant. Because voluntary increases of lung volume should not produce airway closure, we conclude that stress relaxation was responsible for the decrease in lung recoil.

Adult↗

PubMed1981

Determination of respiratory resistance by an oscillation method. Studies of long-term and short-term variability and dependence upon lung volume and compliance.

The respiratory resistance (Ros) as measured by an oscillation method, and the airway resistance (Raw) as measured by body plethysmography were determined in 10 healthy volunteers thrice daily every week over a period of 22 weeks. Ros in 9 of this group was measured at different breathing levels at constant respiratory rate and volume. Additionally, the phase angle between oscillatory pressure and flow (phi), the thoracic gas volume, the end-tidal volume, the functional residual capacity, Raw and the lung compliance were determined. Furthermore Ros of 116 patients was measured together with the lung and thorax compliance. Compared to Raw, the variability of Ros is smaller and the sensitivity is higher. There is a reciprocal relationship between Ros and lung volume, lung compliance, and compliance of the lung and thorax system. Therefore, measurements of Ros should be performed at a normal, stabilized mean breathing level.

Adult↗

PubMed1987

Respiratory effects of a patent ductus arteriosus in premature newborn lambs.

We examined the respiratory effects of a patent ductus arteriosus in 29 premature lambs (131-135 days gestational age) after infiltrating the ductal wall with formaldehyde solution (Formalin) and placing a snare around the ductus to regulate its patency. The lambs were given sheep surfactant, paralyzed, and mechanically ventilated at birth. We first compared 8 lambs with open ductus and 13 lambs with closed ductus during the 12 h after birth. Although lambs with open ductus had greater pulmonary blood flow (301 +/- 36 vs. 188 +/- 11 ml.min-1.kg-1, mean +/- SE, at 12 h of age) and mean pulmonary arterial (44 +/- 3 vs. 33 +/- 2 mmHg) and left ventricular end-diastolic (6 +/- 0.6 vs 4 +/- 0.7 mmHg) pressures, we found no differences in dynamic respiratory compliance (Cdyn = 0.55 +/- 0.07 vs. 0.55 +/- 0.03 ml.cmH2O-1.kg-1), midtidal volume resistance (62 +/- 5 X 10(-3) vs. 62 +/- 7 X 10(-3) cmH2O.ml-1.s), or functional residual capacity (FRC = 27 +/- 3 vs. 26 +/- 2 ml.kg-1). Alveolar-arterial PO2 difference was lower in the lambs with open ductus (238 +/- 65 vs. 362 +/- 37 Torr). Next, we challenged eight lambs with two separate saline infusions (50 ml.kg-1 over 3 min), each given with the ductus alternately closed or open. When the ductus was closed, FRC was unchanged, but Cdyn increased by 18% immediately after the infusion. When the ductus was open, FRC decreased by 16% and Cdyn decreased by 12%. We conclude that the premature lamb is surprisingly resistant to changes in respiratory function from ductal patency during the immediate neonatal period.

Animals↗

PubMed1998

Rate of surfactant administration influences lung function and gas exchange in a surfactant-deficient rabbit model.

The aim of this study was to test whether the effect of surfactant treatment on lung function in a surfactant-deficient animal model can be influenced by the rate at which surfactant is administered. Surfactant deficiency was induced in 18 New Zealand white rabbits (weighing approx. 1 kg each) by lung lavage with normal saline. The arterial/alveolar oxygen ratio (a/A ratio), functional residual capacity (FRC), dynamic compliance of the respiratory system (Crs), tidal volume (V(T)), alveolar portion of the tidal volume (V(A)) and arterial P(CO2) (P(a,CO2)) were measured before and after lavage and 15, 30, 60, 90, and 120 min after administration of a single dose of surfactant (Survanta, 100 mg/kg). Two surfactant administration protocols were compared over a 2-h interval: an infusion lasting 4 min and an infusion over 2 min. Both administrations were given during continuous mechanical ventilation. The six lung function and gas exchange parameters improved significantly following surfactant administration over 2 min compared with a control group. However, only the a/A ratio and V(A) improved following the 4-min protocol. Comparison of the two intervention protocols yielded significantly differences in V(A) and P(a,CO2), favoring the shorter administration. These results support the hypothesis that fast (2 min) administration of surfactant will improve its distribution to formerly collapsed alveoli and results in better lung function, improved ventilation, and (to a lesser extent) better oxygenation than prolonged infusions (4 min).

Animals↗

PubMed2004

Lung volume and the response to high volume strategy, high frequency oscillation.

BACKGROUND: Infants with severe respiratory failure are frequently transferred to high volume strategy, high frequency oscillation (HFO). Mean airway pressure (MAP) is then elevated, the aim being to open up atelectatic lungs and hence improve gas exchange. AIM: To test the hypothesis that lung volume prior to transfer would predict the response to high volume strategy HFO and identify which factors related to poor outcome (death). METHODS: Lung volume was assessed by measurement of functional residual capacity (FRC) and the response to HFO determined by the change in the alveolar arterial gradient (AaDO2) on transfer from conventional mechanical ventilation (CMV) to the optimal MAP on high volume strategy HFO. PATIENTS: Forty-two infants with a median gestational age of 28 (range 23 to 40) wk were studied. RESULTS: FRC prior to transfer correlated significantly with the change in MAP necessary to optimize oxygenation (p = 0.012), but not the change in AaDO2 in response to HFO. There were no significant differences in the lung volumes of survivors and non-survivors, but those who died were more immature (p = 0.0009) and had a smaller response to HFO (p = 0.035). CONCLUSION: Lung volume prior to transfer to high volume strategy HFO might be helpful to guide oscillatory settings, but is a poor predictor of the response to high volume strategy HFO.

Birth Weight↗

PubMed1988

[Instrumentation support in respiratory kinesiotherapy].

The points of impact of instrumental support in respiratory physiotherapy are numerous; they concern primarily the pulmonary expansion, bronchial drainage and function of respiratory muscles. The pulmonary expansion may be helped by incitant spirometry and either intermittent or continuous positive pressure respiration, or indirectly by the utilisation of respiration against resistance (expiratory bottles, masks with uni-directional valves and expiratory resistances etc.). These different techniques may be used in the presence of instability of the respiratory units, secondary to an alteration of surfactant or to closure of the small airways induced by a transitory reduction (in the post-operative period) or permanent reduction (such as parietal wall disease of mechanical or neuro-muscular origin) of the functional residual capacity (CRF). If the continuous positive airway pressure (CPAP) seems particularly helpful for the CRF to recover to the pre-operative level it also appears on the contrary as the least efficacious technique to increase trans-pulmonary pressure. The instrumental support for bronchial drainage may theoretically affect the tension activity of the transport (instrumental help in the pulmonary expansion and in hyperventilation), muco-ciliary transport (external parietal vibration or internal vibrations applied to the upper airways), the biphasic flow (expiratory assistance by negative pressure and humidifiers). The function of the respiratory muscles may in certain cases be improved by the use of abdominal pneumatic cuirasses, by hyperventilation exercises in an isocapnoeic milieu or in breathing exercises against an additional inspiratory or expiratory resistance. If the physiological foundation of mechanical support in respiratory education may be frequently identified, the clinical results reported in the literature are often contradictory.

Drainage↗

PubMed1998

Position and shape of the diaphragm: implications for atelectasis formation.

To evaluate diaphragm movement, 18 consecutive patients undergoing surgery under general anaesthesia were allocated to Group 1 (n = 9: no neuromuscular paralysis) or Group 2 (n = 9: neuromuscular paralysis achieved with pancuronium). Spiral computerised tomography was performed awake and during anaesthesia at end-expiratory level and, additionally, in four patients (Group 2) at end-inspiration for subsequent analysis. There was a significant cephalad displacement of the most cephalad point of the diaphragm dome at functional residual capacity, particularly in its dependent portion, in the pancuronium group. During anaesthesia with no persisting muscle paralysis, there was only a minor and insignificant cephalad shift of the diaphragm dome. However, regional analysis showed that the most dorsal part of the diaphragm was significantly displaced cephalad. Compared with conscious, spontaneous breathing, mechanical ventilation decreased the inspiratory displacement of the dependent part of the muscle. This minor movement of the diaphragm may play an additional role in atelectasis formation.

Adult↗

PubMed1983

Redistribution of pulmonary extravascular water with positive end-expiratory pressure in canine pulmonary edema.

We studied the effect of positive end-expiratory pressure (PEEP) on the quantity and distribution of pulmonary extravascular water (PEW) and on lung mechanics and gas exchange in dogs with high pressure pulmonary edema. Lung volumes, intrapulmonary shunt (Qs/Qt), and dynamic compliance (Cdyn) were measured before (baseline) and after (postinfusion) administration of Ringer's Lactate (25% body weight) to maintain pulmonary wedge pressure between 35 and 40 cm H2O in 16 dogs. Animals were then randomly assigned to a control group (n = 8), ventilated to maintain normocarbia for 1.5 h, and to a PEEP group (n = 8) similarly ventilated with the addition of 10 cm H2O PEEP. After final measurements (1.5 h) and the injection of 51Cr tagged red blood cells, the dogs were killed and right lower lobes were excised and processed for morphometric examination and calculation of PEW by the gravimetric technique. The cuff area/vascular area ratios were measured on all extra-alveolar vessels, and total cuff H2O as well as the cuff H2O/PEW ratio was calculated. Postinfusion, Qs/Qt increased and functional residual capacity (FRC) and Cdyn decreased in both groups. At 1.5 h the PEEP group showed significant improvement in Qs/Qt, FRC, and Cdyn (p less than 0.05). When compared with the control group, the PEEP group had similar amounts of PEW but a greater proportion of cuff H2O. We conclude that PEEP improves gas exchange and lung mechanics, and that it is associated with redistribution of lung water to the "extra-alveolar" interstitial space.

Animals↗