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T G Keens

Publications and source records attributed to T G Keens.

At least 19 recordsLinked to original sources
PubMed1996

Arousal and cardiorespiratory responses to hypoxia in Prader-Willi syndrome.

Ventilatory responses to peripheral chemoreceptor stimuli are absent in patients with Prader-Willi syndrome (PWS) during wakefulness. Because arousal from sleep after rapidly developing hypoxia may require intact peripheral chemoreceptor function, we hypothesized that blunted hypoxic arousal responses during sleep Stage 3/4 would be present in PWS. Thirteen patients with PWS (mean age, 23.4 +/- 3.7 +/- SEM yr; 46% male; body mass index [BMI], 28.9 +/- 1.6 kg/m2) and 11 matched control subjects (mean age 28.0 +/- 5.4 yr; 54% male; BMI, 28.8 +/- 3.1 kg/m2) were studied. An abrupt decrease in inspired O2 tension to 80 mm Hg was introduced until arousal occurred or for a maximum of 3 min. One of the 13 patients with PWS and seven of the 11 control subjects were aroused by the hypoxic challenge (p < 0.02). During hypoxia, heart rate increased by 9 +/- 2% in the PWS group versus 22 +/- 4% in the control group (p < 0.005). Respiratory rate did not change in the PWS group (4 +/- 2%; p = NS), but it increased by 13 +/- 2% in the control group (p < 0.02). We conclude that abnormal arousal and cardiorespiratory responses to hypoxia are frequent in PWS. We postulate that intact peripheral chemoreceptor function is an important component underlying arousal mechanisms to rapidly developing hypoxia during sleep.

Adult↗
PubMed1996

Effects of overnight supplemental oxygen in obstructive sleep apnea in children.

Supplemental oxygen during sleep may be useful as a temporary palliative treatment in children with obstructive sleep apnea syndrome (OSAS) associated with significant hypoxemia. However, supplemental O2 may also blunt hypoxic ventilatory drive and worsen ventilation. To assess the safety of the use of supplemental O2 in children with OSAS, we studied 16 children ages 2-8 (mean: 4.28 +/- 2.88 yr) with OSAS secondary to adenotonsillar hypertrophy. Patients underwent two overnight polysomnograms within 1 mo, one on room air (RA) and one while receiving supplemental O2 via nasal cannula titrated by 1/4 lpm increments to achieve SpO2 > 95% during the first hour of sleep. Oxygenation measurements were significantly improved during supplemental O2 nights (average SpO2 increased from 89.5 +/- 4.8% on RA to 97.7 +/- 1.8% on supplemental O2 [p < 0.00001]) while alveolar ventilation remained unchanged (PETCO2 > 50 mm Hg: 3.6 +/- 8.9% total sleep time on RA and 3.3 +/- 6.3% total sleep time on supplemental O2 [p = NS]). Supplemental O2 significantly reduced hypopnea density, obstructive apnea index, and paradoxical breathing. The density and average duration of central apneas remained unchanged. In addition, supplemental O2 increased the percentage of REM sleep time and decreased the number of microarousals. We conclude that supplemental O2 might be a safe and beneficial temporary treatment in children with OSAS.

Age Factors↗
PubMed1996

Ventilatory responses to passive leg motion in children with congenital central hypoventilation syndrome.

During exercise, children with congenital central hypoventilation syndrome (CCHS) demonstrate coupling of VE to exercise load, despite the absence of a VE response to changes in FICO2. To assess the effect of movement on VE, we studied six CCHS patients and six matched controls during passive motion in a motor-driven ergocycle at pedaling frequencies (PF) of 6 to 60 rpm. VE, VO2, VCO2, VT, heart rate, respiratory rate, SPO2, and PETCO2 were measured. During steady-state conditions, VE was constant at PF of 0 to 30 rpm, but increased at PF > or = 40 rpm in both controls and CCHS patients (p < 0.005). The increase in respiratory rate in CCHS patients was greater than in controls (p < 0.05) whereas VT increased similarly in both groups. At 60 rpm, VO2 increased in both groups, but VE/VO2 and VE/VCO2 increased in the CCHS patients and remained constant in the controls (P < 0.03; p < 0.04). From PF of 0 to 60, PETCO2 decreased from 47 +/- 7 to 41 +/- 6 mm Hg in the CCHS patients (p < 0.001) but remained unchanged in the controls (38 +/- 3 mm Hg; p = NS). An analysis of on-transient responses at 60 rpm revealed that VE increased immediately with the first breath after onset of motion in both groups, and that comparable differences in ventilatory patterns persisted in the two groups. We conclude that passive leg motion at PF > or = 40 increases VE in both CCHS patients and controls. In controls, VE was tightly coupled to VO2 and VCO2. However, in CCHS patients, passive leg motion elicited normalization of PETCO2.

Adolescent↗
PubMed1995

Comparison of dynamic and passive measurements of respiratory mechanics in ventilated newborn infants.

Pulmonary mechanics may differ in intubated and ventilated infants depending on whether they are measured by a dynamic or passive method. The objective of this study was to compare respiratory mechanics measured by a dynamic technique with those obtained by a single-breath occlusion technique in ventilated newborn infants. Thirty-one preterm and 15 term infants (mean +/- SD: gestational age, 29.3 +/- 2.3 and 39.5 +/- 1.4 weeks; birth weight, 1.2 +/- 0.5 and 3.4 +/- 0.4 kg; postnatal age, 12 +/- 13 and 5 +/- 4 days, respectively) were studied. Flows were measured through a pneumotachometer placed between the endotracheal tube and the ventilator circuit: tidal volume by integration of flow, and airway pressure directly with a pressure transducer. Airway occlusion was performed with a Neonatal Occlusion Valve (Bicore pulmonary monitor) at the end of inspiration, and the following relaxed exhalation was analyzed to give passive respiratory system compliance (Crs) and resistance (Rrs). These values were compared with dynamic respiratory system compliance (Cdyn) and dynamic expiratory resistance (Re) obtained with the PEDS system (P) within 1 hour, without an esophageal balloon and on the same ventilator settings. Dynamic respiratory system compliance and resistance measured with the PEDS and the Bicore systems did not differ significantly and were well correlated. Mean Cdyn (P) values in preterm and term infants were 77% and 77% of Crs; the equation of the regression line was Cdyn = 0.75 Crs + 0.02 and Cdyn = 0.78 Crs - 0.02; and standard error of the estimate (SEE) was 0.2 and 0.3 mL/cmH2O with a correlation coefficient (r) of 0.89 and 0.89 (P < 0.0001), respectively. The mean Re(P) values in preterm and term infants were 68% and 64% of Rrs, and the equation of the regression line was Re = 0.3 Rrs + 63 and Re = 0.5 Rrs + 20, with SEE of 25 and 20 cmH2O/L/sec, and r of 0.65 and 0.69 (P < 0.0001, P < 0.005), respectively. The two methods are non-invasive and were well tolerated. We conclude that passive and dynamic respiratory compliance and resistance measured in intubated infants are highly correlated, although the values measured by the passive technique are higher than those obtained by the dynamic technique.

Airway Resistance↗
PubMed1995

Ventilatory responses to repeated short hypercapnic challenges.

In early phases of respiratory disease, patients are more likely to experience intermittent hypercapnia than a continuous increase in PCO2. The effect of intermittent arterial PCO2 elevation on subsequent breathing patterns is unclear. To examine this issue, a series of six ventilatory challenges (CH1-CH6), consisting of 2 min of breathing 5% CO2 in O2, followed by 5 min in room air (RA) were performed in 10 naive healthy subjects (age 12-39 yr). Minute ventilation (VE) increased from 11.9 +/- 1.0 (SE) l/min in RA to 27.6 +/- 3.0 l/min in 5% CO2 (P < 0.0005) in each of the six hypercapnic challenges. Respiratory rate increased from 21.3 +/- 2.6 breaths/min on RA to 29.6 +/- 3.9 breaths/min during CH1 (P < 0.05). However, respiratory rate consistently decreased with successive CO2 challenges (CH6: 21.5 +/- 2.6 breaths/min; P < 0.02). Thus, maintenance of VE was achieved by gradual increases in tidal volume with each of the first four consecutive CO2 challenges (CH1: 1.05 +/- 0.09 liters; CH4: 1.44 +/- 0.13 liters; P < 0.002). Similarly, the ratio of tidal volume to inspiratory time increased from CH1 (1.16 +/- 0.16 l/s) to CH6 (1.57 +/- 0.21 l/s; P < 0.001). These changes in ventilatory strategy were not observed when RA recovery periods were extended to 15 min in five subjects. We conclude that during repeated short hypercapnic challenges similar levels of VE are achieved. However, increased mean inspiratory flows are generated to maintain VE. We speculate that intermittent hypercapnia either modifies central controller gain or induces a long-term modulatory effect to account for the progressive changes in ventilatory components.

Administration, Inhalation↗
PubMed1995

Ventilatory response to consecutive short hypercapnic challenges in children with obstructive sleep apnea.

In healthy adults, a ventilatory pattern characterized by progressively increased tidal volume (VT), and decreased respiratory rate (RR) accompany repeated short hypercapnic ventilatory challenges, while minute ventilation (VE) remains constant. We hypothesized that the peculiar ventilatory pattern seen in adults would be blunted in children with obstructive sleep apnea syndrome (OSAS) who undergo comparable intermittent or chronic alveolar PCO2 elevation. We measured ventilatory responses to five challenges of 2-min duration (C1-C5) with 5% CO2 in O2, separated by 5-min room-air breathing intervals (R1-R4), in nine children with OSAS and in eight age-, sex-, and body mass index-matched controls. In all children, CO2 significantly increased VE when compared with baseline conditions (22.3 +/- 2.2 vs. 9.5 +/- 0.9 (SE) l/min; P < 0.001). In control subjects, progressive VT increases from 0.67 +/- 0.10 liter in C1 to 0.92 +/- 0.13 liter in C5 occurred (P < 0.01), whereas RR decreased from 33.9 +/- 5.1 breaths/min in C1 to 27.8 +/- 3.7 breaths/min in C5 (P < 0.02), resulting in VE increases across CO2 challenges (22.3 +/- 4.9 l/min in C1 vs. 25.1 +/- 5.0 l/min in C5; P < 0.005). The RR decrease was primarily related to progressive prolongation of expiratory time (TE) (1.1 +/- 0.1 s in C1 to 1.5 +/- 0.2 s in C5; P < 0.002). In contrast, VT, RR, and TE did not change in a consistent fashion in OSAS patients with repeated CO2 challenges (OSAS vs. control: P < 0.0001). Furthermore, in OSAS, VE was similar with repeated challenges (22.4 +/- 2.2 1/min in C1 vs. 23.9 +/- 1.9 l/min; P = not significant), such that changes in VE over time significantly differed in OSAS and controls (P < 0.001). We conclude that healthy children modify their ventilatory strategy to repeated hypercapnia. We speculate that in OSAS these mechanisms are already fully implemented because of recurrent alveolar hypoventilation accompanying increased upper airway resistance, leading to blunted temporal trends of ventilatory response.

Adolescent↗
PubMed1995

Peripheral chemoreceptor function in children with myelomeningocele and Arnold-Chiari malformation type 2.

Blunted rebreathing hyperoxic hypercapnic ventilatory and arousal responses are frequent in older children with myelomeningocele (MMC) and Arnold-Chiari malformation type 2 (ACM). In contrast, isocapnic hypoxic rebreathing ventilatory responses are only occasionally affected. Thus, regions mediating the hypoxic ventilatory response appear usually preserved in children with MMC and ACM. Peripheral chemoreceptor function (PCR), however, has not been critically assessed in these children. To study this, PCR was measured in ten children and adolescents with MMC and ACM with normal alveolar ventilation during wakefulness, and in ten sex- and age-matched controls by measuring the ventilatory responses induced by 100% O2 breathing, five tidal breaths of 100% N2, and vital capacity breaths of 15% CO2 in O2. In general, tidal breathing of 100% O2 resulted in smaller decreases in minute ventilation (VE) responses in patients with MMC, although absent VE responses to hyperoxia were found in four patients. Vital capacity breaths of 15% CO2 elicited similar increases in VE in five patients and in ten controls, but no changes in VE were found in the remaining five patients (p < 0.02). Acute hypoxia induced by N2 tidal breathing resulted in significant linear regression correlations between VE and SpO2 in five patients with MMC, while absent responses were measured in those same five patients with absent hypercapnic responses. We conclude that PCR, when assessed by acute hypoxia, hyperoxia, or hypercapnia is abnormal in some children with MMC and ACM, particularly in those demonstrating abnormal ventilation during sleep. We postulate that the large interindividual variability of PCR is dependent on the severity of brainstem involvement of PCR afferents or central respiratory integration sites.

Adolescent↗
PubMed1995

Hypercapnic arousal responses in Prader-Willi syndrome.

STUDY OBJECTIVE: Prader-Willi syndrome (PWS) is characterized by a number of abnormalities of hypothalamic function, such as hyperphagia, short stature, temperature instability, hypogonadotropic hypogonadism, and neurosecretory growth hormone deficiency. Patients with PWS are reported to have sleep-disordered breathing and have blunted hypercapnic ventilatory responses secondary to abnormal peripheral chemoreceptor function. Thus, we hypothesized that hypercapnic arousal responses would be abnormal in PWS. DESIGN: Hypercapnic arousal responses were tested in ten nonobese children and adults with PWS, aged 17.7 +/- 2.5 (SEM) years, 70% female, and nine control subjects, aged 14.2 +/- 2.6 years, 67% female. Hypercapnic challenges were performed during stage 3/4 non-rapid eye movement sleep. RESULTS: The PWS subjects had a significantly higher arousal threshold to hypercapnia compared with the controls (53 +/- 1.0 vs 46 +/- 1.7 mm Hg; p < 0.01). The PWS subjects had significantly higher baseline end-tidal CO2 levels (42 +/- 0.8 vs 38 +/- 1.1 mm Hg; p < 0.01) and more central apneas greater than 15 s/h of sleep (1.5 +/- 0.3 vs 0.1 +/- 0.1; p < 0.01). CONCLUSIONS: Elevated hypercapnic arousal thresholds during sleep are found in PWS subjects; these may be a manifestation of abnormal peripheral chemoreceptor function and may further contribute to sleep-disordered breathing in PWS patients.

Adolescent↗
PubMed1994

SIDS research.

Explore the source record for details and available documents.

Apnea↗
PubMed1994

Incidence of sudden infant death syndrome in infants with sickle cell trait.

The significantly higher incidence of both sickle cell trait (SCT) and sudden infant death syndrome (SIDS) in the black population suggests that SCT and SIDS may be epidemiologically related. To study this possibility, we identified, for the period of February 1990 to February 1992, all infants with SCT born in Los Angeles County whose disease was diagnosed through the California Newborn Screening Program. We matched these infants with all confirmed cases of SIDS in Los Angeles County from February 1990 to March 1993. Three cases of SCT among 589 infants confirmed to have had SIDS were identified. The incidence of SIDS was 1.25/1000 live births for the general population versus 0.58/1000 cases for the SCT group. This finding remained unchanged when rates were adjusted for ethnicity. We conclude that infants born with SCT are not at increased risk of dying of SIDS.

Black People↗
PubMed1994

Developmental pattern of hypercapnic and hypoxic ventilatory responses from childhood to adulthood.

The developmental pattern of ventilatory responses, through childhood and puberty into adulthood, is not known. Therefore we studied hypercapnic (HCVR) and hypoxic ventilatory responses (HOVR) in 59 subjects (29 males and 30 females) 4-49 yr of age, of whom 35 were children ( < 18 yr old). There was a significant correlation between HCVR and weight (r = 0.33, P < 0.02), vital capacity (r = 0.30, P < 0.05), and body surface area (r = 0.30, P < 0.05) but not height (r = 0.22, NS). There was no correlation between HOVR and any of the correcting factors. To account for disparities in body size, volume-related results were scaled for body weight. The HCVR corrected for weight (HCVR/WT) decreased with age (r = -0.57, P < 0.001). HCVR/WT was significantly higher in children than in adults (0.056 +/- 0.024 vs. 0.032 +/- 0.015 l.kg-1 x min-1. Torr end-tidal PCO2-1, P < 0.001). The (tidal volume/inspiratory duration)/weight, respiratory rate, and heart rate responses to hypercapnia were increased in the children, and the CO2 threshold was lower (36 +/- 5 vs. 40 +/- 6 Torr, P < 0.05). Similarly, the HOVR corrected for weight (HOVR/WT) decreased with age (r = 0.34, P < 0.05), and HOVR/WT was significantly higher in children than in adults (-0.035 +/- 0.017 vs. -0.024 +/- 0.016 l.kg-1 x min-1.% arterial O2 saturation-1, P < 0.02). The respiratory rate and heart rate responses to hypoxia were increased in the children. We conclude that rebreathing HCVR and HOVR are higher during childhood than during adulthood.

Adolescent↗
PubMed1994

Maturational differences in step vs. ramp hypoxic and hypercapnic ventilatory responses.

The influence of the speed of stimulus presentation on hypoxic and hypercapnic ventilatory responses (step vs. ramp) is not known. Furthermore, it is unclear whether children and adults respond similarly. We tested ramp ventilatory responses to hypercapnia and hypoxia with use of rebreathing in 8 prepubertal children and 11 adults. We tested step ventilatory responses to hypercapnia with single vital capacity breaths of 15% CO2 in O2 and to hypoxia with five tidal breaths of 100% N2. For children, slopes of step hypercapnic ventilatory responses were always greater than those of ramp responses (0.85 +/- 0.07 vs. 0.71 +/- 0.07 l.min-1.Torr end-tidal PCO2-1; P < 0.0005). Conversely, for adults, step responses were always less than ramp responses (0.88 +/- 0.19 vs. 2.10 +/- 0.29 l.min-1.Torr end-tidal PCO2-1; P < 0.0007). Similarly, for children, the slopes of step hypoxic ventilatory responses were always greater than those of ramp responses (-0.71 +/- 0.09 vs. -0.45 +/- 0.04 l.min-1.Torr O2 saturation-1; P < 0.02), and for adults, step responses were always less than ramp responses (-0.68 +/- 0.14 vs. -1.85 +/- 0.46 l.min-1.Torr O2 saturation-1; P < 0.04). We conclude that ventilatory responses vary depending on step vs. ramp presentation of hypercapnia or hypoxia and that the ratio of these responses is reversed in children compared with adults. We speculate that the responsiveness of peripheral chemoreceptors is increased in children compared with adults and that it may play a role in the mechanisms leading to increased ventilatory responses observed during childhood.

Adult↗
PubMed1994

Hypoxic and hypercapnic ventilatory responses in Prader-Willi syndrome.

Abnormalities of ventilatory control may play a significant role in the pathophysiology of sleep-disordered breathing in patients with the Prader-Willi syndrome (PWS). We measured rebreathing hypercapnic and hypoxic ventilatory responses (HCVR and HPVR, respectively) during wakefulness in 8 nonobese PWS (NOB-PWS) and 9 obese PWS (OB-PWS) patients and compared their results with those from 24 healthy nonobese control (NOB-CON) and 10 obese control (OB-CON) subjects. The slope of HCVR was similar in NOB-PWS patients and NOB-CON subjects (NS). However, HCVR was significantly lower in OB-PWS patients than in OB-CON subjects (P < 0.02). In PWS patients, the mean point of origin of the positive slope of HCVR occurred at a significantly higher end-tidal PCO2 than in either control group. During isocapnic hypoxic challenges, six PWS patients had no significant HPVR. In the remainder, mean slopes of HPVR were -0.80 +/- 0.06 l.min-1.%arterial O2 saturation-1 in five NOB-PWS patients and -0.68 +/- 0.15 l.min-1.%arterial O2 saturation-1 in six OB-PWS patients. These responses were significantly decreased compared with those in the control groups (P < 0.006). We conclude that NOB-PWS patients have normal HCVR, which is blunted in OB-PWS patients. Furthermore, isocapnic HPVR is either absent or markedly reduced in PWS patients. The severity of abnormality of the HPVR is independent of the degree of obesity. We postulate that the primary abnormality of ventilatory control in PWS affects peripheral chemoreceptor pathways.

Adult↗
PubMed1994

Absent peripheral chemosensitivity in Prader-Willi syndrome.

Abnormalities in ventilatory control during wakefulness and sleep have been observed in patients with Prader-Willi syndrome (PWS). The role of peripheral chemoreceptors in the pathophysiology of abnormal ventilatory responses in PWS is unknown. We studied peripheral chemoreceptor function during wakefulness in 17 genetically confirmed PWS patients [age 27.0 +/- 2.5 (SE) yr; 7 males, 10 females; body mass index 31.1 +/- 1.4 kg/m2] and compared their responses with 17 control subjects matched for age, sex, and body mass index. All PWS and control subjects had normal resting end-tidal PCO2 and arterial O2 saturation while awake. Peripheral chemoreceptor function was assessed by the ventilatory responses to 100% O2 breathing, five tidal breaths of 100% N2, and vital capacity breaths of 15% CO2 in O2. Control subjects decreased minute ventilation (VE) by 15.5 +/- 3.6% during hyperoxia. However, PWS patients increased VE by 17.6 +/- 3.3%, indicating a paradoxical response to hyperoxia (P < 0.00001). After CO2 vital capacity breaths, PWS patients showed no significant change and control subjects showed a marked increase (P < 0.0001) in VE. During N2 breathing, again PWS patients showed no change and control subjects exhibited a marked increase (P < 0.00005) in VE. We conclude that PWS patients have absent peripheral chemoreceptor ventilatory responses. We speculate that the lack of ventilatory responses is due to primary peripheral chemoreceptor dysfunction and/or defective afferent pathways to central controllers.

Adult↗
PubMed1994

Ventilatory responses during wakefulness in children with obstructive sleep apnea.

The pathophysiology of the obstructive sleep apnea syndrome (OSAS) is not fully understood. In children, airway obstruction secondary to tonsilloadenoidal hypertrophy is the leading cause of OSAS. However, not all children with tonsilloadenoidal hypertrophy develop OSAS. Thus, other factors, including abnormalities in ventilatory control, may contribute to the etiology of OSAS. To test this, we performed polysomnography and hypercapnic and hypoxic ventilatory response testing in 20 children and adolescents with OSAS (mean age, 8 +/- 3 [SD] yr) and 19 control subjects. Only two children with OSAS were obese. Children with OSAS had an apnea index of 16 +/- 20, peak PETCO2 of 54 +/- 5 mm Hg, and SaO2 nadir of 84 +/- 13% during polysomnography. Ventilatory responses were performed by rebreathing techniques. The slope of the hypercapnic ventilatory responses, corrected for body surface area, was 1.74 +/- 0.79 L/min/m2/mm Hg PETCO2 in children with OSAS and 1.45 +/- 0.58 L/min/m2/mmHg PETCO2 in control subjects (NS). Hypoxic ventilatory responses, corrected for body surface area, were -0.94 +/- 0.49 L/min/m2/% SaO2 in children with OSAS and -0.95 +/- 0.45 L/min/m2/% SaO2 in control subjects (NS); however, the sample size was small. There was a weak inverse correlation between the slope of the hypercapnic ventilatory response and the duration of hypoventilation during polysomnography (r = -0.44, p < 0.05). We conclude that children with OSAS have normal ventilatory responses to hypercapnia, and they may have normal ventilatory responses to hypoxia. We speculate that abnormal central ventilatory drive plays little if any role in the pathogenesis of pediatric OSAS.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoids↗
PubMed1994

Comparison of high frequency chest compression and conventional chest physiotherapy in hospitalized patients with cystic fibrosis.

Clearance of bronchial secretions is essential in the management of cystic fibrosis (CF) patients admitted for acute pulmonary exacerbation. Conventional physiotherapy (CPT) is labor-intensive, time-consuming, expensive, and may not be available as frequently as desired during hospitalization. High frequency chest compression (HFCC), which uses an inflatable vest linked to an air-pulse delivery system, may offer an attractive alternative. To study this, we prospectively studied 50 CF patients admitted for acute pulmonary exacerbation who were randomly allocated to receive either HFCC or CPT three times a day. On admission, clinical status and pulmonary function tests (PFT) in the HFCC group were not significantly different from those measured in the CPT group. Significant improvements in clinical status and PFT were observed after 7 and 14 d of treatment, and were similar in the two study groups, leading to patient discharge after similar periods of hospitalization. We conclude that HFCC and CPT are equally safe and effective when used during acute pulmonary exacerbations in CF patients. We speculate that HFCC may provide an adequate alternative in management of CF patients in a hospital setting.

Acute Disease↗
PubMed1993

Evolution of pulmonary function during an acute exacerbation in hospitalized patients with cystic fibrosis.

Few objective criteria have been validated for serial clinical monitoring in patients with cystic fibrosis (CF) during pulmonary exacerbations. While pulmonary function tests (PFT) are often used to monitor clinical improvement, it is not known which test correlates most closely with clinical improvement. To answer this, we measured routine PFT in 58 patients with CF before, during, and at discharge after 2-3 week hospital admission in 71 episodes of pulmonary exacerbation. Patients with CF were discharged based on clinical, radiological, and laboratory criteria. In general, all PFTs improved at midadmission and improved further by discharge, at which time forced expiratory volume in 1 second (FEV1), forced expiratory flow between 25% and 75% of forced vital capacity (FEF25-75), vital capacity (VC), maximal voluntary ventilation (MVV), and oxygen saturation by pulse oximetry (SPO2) increased. The residual volume to total capacity ratio (RV/TLC) and the slope of phase 3 in the single breath N2 washout curve (SP3 N2) decreased. The change in SP3 N2 was significantly greater than in any other PFT (P < 0.01 vs. VC and FEV1; P < 0.02 vs. RV and P < 0.001 vs. SPO2). A calculated optimal cut-off value for SP3 N2 improvement was significantly more sensitive in identifying patient improvement at discharge than any other pulmonary function test (P = 0.005). We speculate that clinical improvement in patients with CF is closely linked to improved distribution of ventilation.

Acute Disease↗