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Background International guidelines suggest using a higher (>10 cmH2O) positive end-expiratory pressure (PEEP) in patients with moderate-to-severe acute respiratory distress syndrome (ARDS) due to the novel coronavirus disease (COVID-19). However, even if oxygenation generally improves with a higher PEEP, compliance and arterial carbon dioxide tension (PaCO2) frequently do not, as if recruitment was small. Research question Is the potential for lung recruitment small in patients with early ARDS due to COVID-19? Study design and methods Forty patients with ARDS due to COVID-19 were studied in the supine position within three days of endotracheal intubation. They all underwent a PEEP trial, where oxygenation, compliance, and PaCO2 were measured with 5, 10, and 15 cmH2O of PEEP and all other ventilatory settings unchanged. Twenty underwent a whole-lung static computed tomography at 5 and 45 cmH2O, and the other twenty at 5 and 15 cmH2O of airway pressure. Recruitment and hyperinflation were defined as a decrease in the volume of the non-aerated (density above -100 HU) and an increase in the volume of the over-aerated (density below -900 HU) lung compartments, respectively. Results From 5 to 15 cmH2O, oxygenation improved in thirty-six (90%) patients but compliance only in eleven (28%) and PaCO2 only in fourteen (35%). From 5 to 45 cmH2O, recruitment was 351 (161-462) ml and hyperinflation 465 (220-681) ml. From 5 to 15 cmH2O, recruitment was 168 (110-202) ml and hyperinflation 121 (63-270) ml. Hyperinflation variably developed in all patients and exceeded recruitment in more than half of them. Interpretation Patients with early ARDS due to COVID-19, ventilated in the supine position, present with a large potential for lung recruitment. Even so, their compliance and PaCO2 do not generally improve with a higher PEEP, possibly due to hyperinflation.

Background Increased pleural pressure affects the mechanics of breathing of people with class III obesity (BMI > 40 kg/m2). Research Question What are the acute effects of CPAP titrated to match pleural pressure on cardiopulmonary function in spontaneously breathing patients with class III obesity? Study design and Methods We enrolled six participants with BMI within normal range (control participants, group I) and 12 patients with class III obesity (group II) divided into subgroups: IIa, BMI of 40 to 50 kg/m2; and IIb, BMI of ≥ 50 kg/m2. The study was performed in two phases: in phase 1, participants were supine and breathing spontaneously at atmospheric pressure, and in phase 2, participants were supine and breathing with CPAP titrated to match their end-expiratory esophageal pressure in the absence of CPAP. Respiratory mechanics, esophageal pressure, and hemodynamic data were collected, and right heart function was evaluated by transthoracic echocardiography. Results The levels of CPAP titrated to match pleural pressure in group I, subgroup IIa, and subgroup IIb were 6 ± 2 cmH2O, 12 ± 3 cmH2O, and 18 ± 4 cmH2O, respectively. In both subgroups IIa and IIb, CPAP titrated to match pleural pressure decreased minute ventilation (IIa, P = .03; IIb, P = .03), improved peripheral oxygen saturation (IIa, P = .04; IIb, P = .02), improved homogeneity of tidal volume distribution between ventral and dorsal lung regions (IIa, P = .22; IIb, P = .03), and decreased work of breathing (IIa, P Interpretation In ambulatory patients with class III obesity, CPAP titrated to match pleural pressure decreased work of breathing and improved respiratory mechanics while maintaining hemodynamic stability, without impairing right heart function. Trial Registry ClinicalTrials.gov; No.: NCT02523352; URL: www.clinicaltrials.gov

Case Presentation A 63-year-old man was referred for slowly progressive dyspnea on exertion that had developed over 7 years. Dyspnea was initially only present during high-intensity physical activity, but was now present while walking rapidly on a flat surface. Symptoms were accentuated while supine and when bending forward. He reported respiratory difficulties when submerged in water and a recent onset of slight symmetric lower limb weakness that was only apparent during strenuous physical activity. He also had OSA, which was adequately controlled with continuous positive airway pressure therapy. Neurologic and rheumatologic histories were otherwise unremarkable. He denied any impact accidents or trauma to the cervical spine and prior neck or thoracic surgeries.

TOPIC: Pulmonary Physiology TYPE: Fellow Case Reports INTRODUCTION: Respiratory muscle weakness is known to occur in neurodegenerative disorders, including Huntington's disease (HD), and causes 25% of deaths in this population. Though diaphragmatic dystonia has been described in some neurodegenerative diseases, it has not been in HD. In general, little published data exists on overall respiratory function and diaphragmatic movement in HD. CASE PRESENTATION: We describe a 58-year-old male with HD, presenting with progressive dyspnea over 1 year and an accompanying choking sensation upon awakening. Cardiac evaluation with echocardiogram and dobutamine stress test revealed only left ventricular hypertrophy. Family history includes HD in his mother, diagnosed at autopsy age 72;an older brother with HD onset at 53 that died at 62;a maternal aunt with onset in her 50s that died in her 70s. His maternal grandmother and 2 other family members also had involuntary movements believed to be chorea. Most died from respiratory complications. Physical exam showed adequate air entry bilaterally, with clear breath sounds and decreased chest wall expansion. No abdominal paradox or diaphragm dysfunction was appreciated in supine or seated position. On walking oximetry, he became tachypneic and dyspneic after 2 minutes of walking, prompting him to stop. His saturation on room air did not drop below 96%. Heart rate increased to 110 beats per minute. Laboratory panel revealed hemoglobin 13.8 g/dl. A venous blood gas revealed pH 7.38 and pCO2 of 49.A dynamic digital chest radiography (DDR) was performed during two tidal breaths and a forced inspiratory and expiratory maneuver. This revealed decreased bilateral lung inflation. Diaphragmatic contours were elevated bilaterally with a mildly reduced excursion. During the breathing cycle multiple independent diaphragmatic contractions were appreciated on forced inspiration and exhalation resulting in paradoxical motion and dyssynchrony. There was exaggerated use of accessory muscles in the shoulder girdle as a compensatory mechanism. Spasms in the upper airway were also noted throughout the test. Because of covid restrictions, the patient is awaiting pulmonary function tests. DISCUSSION: DDR uniquely provides the opportunity to interrogate respiratory physiology and identify diaphragmatic abnormalities, such as coordination impairments and dyssynchrony compared to static chest radiography;with lower levels of radiation as used in video fluoroscopy. As previously described1, we suggest that the understanding of dyspnea in patients with neurologic disease is enhanced using DDR. CONCLUSIONS: We report the first case of diaphragmatic chorea in a patient with HD using DDR. Future studies are needed to better understand this newly recognized phenomenon of diaphragmatic discoordination and its association with shortness of breath. REFERENCE #1: O'Sullivan M, Singh A, Prime D, Moore J, Zink S. A Whole New Chest X-Ray. ATS 2019 ePoster Viewing Site. Published May 2019. Accessed April 28, 2021. https://cslide-us.ctimeetingtech.com/ats2019_eposter/attendee/eposter/poster/6529 DISCLOSURES: No relevant relationships by Norma Braun, source=Web Response No relevant relationships by Jose Concepcion, source=Web Response No relevant relationships by Natasha Garg, source=Web Response No relevant relationships by Mary O Sullivan, source=Web Response No relevant relationships by Valeria Santibanez, source=Web Response

A 43-year-old man was referred to our tertiary sleep center for the initiation of sleep apnea treatment. A prior diagnostic overnight polysomnography (Fig 1) had revealed an apnea-hypopnea index (AHI) of 22/h of sleep. The apneas were predominantly central (central AHI, 18.2/h; obstructive AHI, 3.8/h), more pronounced in the supine position (AHI supine, 36.6/h; AHI nonsupine, 11/h) and during non-rapid eye movement (non-REM) sleep (REM, 15.8/h; non-REM, 23.5/h). A continuous positive airway pressure (CPAP) trial in an outpatient setting had failed, as the fixed CPAP of 11 cm H2O was not tolerated by the patient because of a feeling of lightheadedness when wearing the mask. At referral, the patient complained about falling asleep in front of the computer in the afternoons despite regular bedtimes and 7 to 8 h of sleep per night. His Epworth Sleepiness Scale score was 11. He had no significant past history including cardiopulmonary disease. He was not taking any medication but had noticed a slow decline in general physical performance in the last year, with dyspnea (New York Heart Association class I) after running distances of 1 to 2 km. He had never experienced syncope. His family history was unremarkable.

Background: The goal of this study was to evaluate the effi cacy of ipsilateral opposite-side aspiration, a new method to overcome resistant pneumothorax after failure of a simple aspiration. The patient position is reversed (from prone to supine or vice versa) and the aspiration repeated. Methods: Between January 1, 2010, and April 3, 2012, 129 consecutive, CT image-guided, percutaneous needle biopsies of lung nodules were performed in 127 patients (75 men, 52 women; mean age, 67.8 years; range, 26-88 years). Two patients underwent repeated biopsies. The mean lesion diameter was 38 mm (range, 8-110 mm). Core biopsy and fi ne-needle aspiration (FNA) were performed in 126 procedures; in three cases, only FNA was performed. In the cases with symptomatic minimal pneumothorax and in all patients with pneumothorax . 10 mm, immediate, simple, manual aspiration was performed. Ipsilateral opposite-side aspiration was performed when simple aspiration failed. Results: Among 129 CT image-guided biopsies, pneumothorax was detected by CT scan in 54 (42%); 51 (39%) were detected during the biopsy. Delayed pneumothorax occurred in two patients (1.55%). Manual aspiration to treat pneumothorax was performed in 27 of 129 procedures (21%). Simple aspiration was successful in 20 of these 27 cases (74%). Ipsilateral opposite-side aspiration was accomplished in the remaining seven cases (26%) and was successful in six cases (86%). Two of 129 procedures (1.55%) required chest tube placement. Conclusions: Immediate, simple, percutaneous aspiration of iatrogenic pneumothorax was successful in 74% of patients needing treatment. Our proposed new method of ipsilateral oppositeside aspiration offers a solution for patients who remain with resistant pneumothorax after simple aspiration. CHEST 2013; 144(3):947–951

Background Unintentional leakage from the mouth or around the mask may lead to cessation of CPAP treatment; however, the causes of unintentional leaks are poorly understood. The objectives of this study were (1) to identify determining factors of unintentional leakage and (2) to determine the effect of the type of mask (nasal/oronasal) used on unintentional leakage. Methods Seventy-four polysomnograms from patients with OSA syndrome treated with auto-CPAP were analyzed (23 women; 56 ± 13 years; BMI, 32.9 kg/m 2 (range, 29.0-38.0 kg/m 2 ). Polysomnographic recordings were obtained under auto-CPAP, and mandibular behavior was measured with a magnetic sensor. After sleep and respiratory scoring, polysomnographic signals were computed as mean values over nonoverlapping 10-s intervals. The presence/absence of unintentional leakage was dichotomized for each 10-s interval (yes/no). Univariate and multivariate conditional regression models estimated the risk of unintentional leaks during an interval "T" based on the explanatory variables from the previous interval "T-1." A sensitivity analysis for the type of mask was then conducted. Results The univariate analysis showed that mandibular lowering (mouth opening), a high level of CPAP, body position (other than supine), and rapid eye movement (REM) sleep increased the risk of unintentional leaks and microarousal decreased it. In the multivariate analysis, the same variables remained independently associated with an increased risk of unintentional leakage. The sensitivity analysis showed that oronasal masks reduced the risk of unintentional leaks in cases of mouth opening and REM sleep. Conclusions Mouth opening, CPAP level, sleep position, and REM sleep independently contribute to unintentional leakage. These results provide a strong rationale for the definition of phenotypes and the individual management of leaks during CPAP treatment.

Critical pressure (Pcrit) is considered a reliable parameter to evaluate the mechanical properties of the passive upper airway (UA) and is significantly increased in patients with obstructive sleep apnea-hypopnea (OSAH) compared with normal subjects. The volume exhaled in the first 0.5 s after application at the mouth of 5 cm H(2)O negative pressure at the onset of expiration (V,NEP(0.5)) during wakefulness has been used as a marker of UA collapsibility. The aim of this study was to investigate if there is a significant relationship between V,NEP(0.5) and Pcrit in normal subjects, snorers, and patients with OSAH.Thirty men, 10 with OSAH (aged 64 +/- 9.1 years, BMI 32 +/- 4.9 kg/m(2), apnea-hypopnea index [AHI] 43.8 +/- 24, neck circumference 46.6 +/- 3.7 cm), 10 snorers (aged 68 +/- 11 years, BMI 26.6 +/- 4.6 kg/m(2), AHI 3.5 +/- 0.8, snoring timeor = 30% of sleep time, neck circumference 42.2 +/- 3.9 cm), and 10 controls (aged 67 +/- 12 years, BMI 25.4 +/- 2.2 kg/m(2), AHI 1.9 +/- 1.2, neck circumference 41.2 +/- 2.2 cm) underwent V,NEP(0.5) measurement in supine position while awake and Pcrit measurement during sleep. Correlation between V,NEP(0.5) and Pcrit was performed in all subjects.Controls had V,NEP(0.5) of 456 +/- 82 mL and Pcrit of -1.38 +/- 0.6 cm H(2)O, snorers had V,NEP(0.5) of 321 +/- 33 mL and Pcrit -0.55 +/- 0.3 cm H(2)O, and patients with OSAH showed V,NEP(0.5) of 295 +/- 67 mL and Pcrit of 0.99 +/- 1 cm H(2)O (P.001 vs normal subjects). A strong correlation was found between V,NEP(0.5) and Pcrit (r(2) = 0.61, P.0001).In males with neck circumference37 cm, V,NEP(0.5) during wakefulness strongly reflects Pcrit in a wide range of values. Our findings suggest that V,NEP(0.5) can be used as valuable substitute for Pcrit to assess UA collapsibility for clinical and research purposes in these subjects.

Background The relationships among systolic pulmonary artery pressure (SPAP), diastolic pulmonary artery pressure (DPAP), and mean pulmonary artery pressure (MPAP) have been found to be constant in humans breathing air, at rest, while supine. It would be important for those studying the pulmonary circulation if this relationship were maintained under other circumstances, such as change in posture, during exercise, or after pharmacologic manipulation. In particular, it would be useful if the relationship were maintained when treating pulmonary hypertension because this would allow different methods of measurement to be compared, such as SPAP from echocardiography and MPAP from right heart catheterization. Methods Data were reviewed from both healthy subjects and those with pulmonary hypertension (n = 65) who had a micromanometer-tipped, high-fidelity pulmonary artery catheter inserted for between 6 and 36 h in the Scottish Pulmonary Vascular Unit between 1997 and 2003. The 5-min averages, while the patient was supine at rest, were analyzed by linear regression to compare the response of SPAP and DPAP with MPAP. Results There were linear relationships (measured in millimeters of mercury) of SPAP with MPAP (SPAP = 1.50 MPAP + 0.46), and DPAP with MPAP (DPAP = 0.71 MPAP − 0.66). These were maintained with a high degree of accuracy following changes in posture and activity. Conclusions SPAP, MPAP, and DPAP were strongly related, and these relationships were maintained under varying conditions. This finding will allow comparison between invasive and noninvasive descriptions of pulmonary hemodynamics found in the literature.

A 51-year-old woman with a personal history of vitiligo, normal thyroid hormone studies, a simple hysterectomy for multiple uterine myomas at age 35 years, and childhood adenotonsillectomy was seen for progressive hearing loss. She reported mild asthenia, cold intolerance, mild dysphagia with frequent choking while eating and drinking, and a progressive increase in inspiratory effort, especially in the supine position. Her partner described a progressively worsening history of snoring and witnessed apneic episodes, mostly in the supine position. Mild to moderate daytime sleepiness was also present.

Background This study explored the sensitivity and specificity of ultrasound for diagnosing transient tachypnea of the newborn (TTN). Methods Ultrasound was performed by one export. Patients were placed in a supine, lateral recumbent, or prone position. The probe was placed perpendicular or parallel to the ribs, and each region of the lung was scanned. The scan results were compared with conventional chest radiographic results. Results A total of 1,358 infants were included in this study. We identified 412 cases without pulmonary diseases, 228 TTN cases, 358 respiratory distress syndrome (RDS) cases, 85 meconium aspiration syndrome (MAS) cases, 215 infectious pneumonia cases, and 60 other cases. The primary ultrasonic characteristic of TTN was pulmonary edema. “White lung” or a “compact B-line” were only observed in severe cases, whereas TTN primarily presented as pulmonary interstitial syndrome or “double lung point.” Furthermore, double lung point could appear during the recovery period of severe TTN or RDS, MAS, and pneumonia. Lung consolidation with air bronchograms was not observed in TTN patients. The results showed that white lung or a compact B-line exhibited a sensitivity of 33.8% and a specificity of 91.3% in diagnosing TTN, whereas double lung point exhibited a sensitivity of 45.6% and a specificity of 94.8% in diagnosing severe TTN. Conclusions Pulmonary edema, alveolar-interstitial syndrome, double lung point, white lung, and compact B-line are the primary ultrasound characteristics of TTN. Ultrasonic diagnosis of TTN based on these findings is accurate and reliable. TTN can be ruled out in the presence of lung consolidation with air bronchograms.

Study objective To determine if a 3-min bout of moderately intensive supine bicycle exercise, whole-body periodic acceleration (pGz), and passive motorized cycling cause nitric oxide (NO) release into the circulation, as detected by dicrotic notch descent on the diastolic limb of a finger pulse wave. Participants Fourteen healthy adults underwent two levels of supine bicycle ergometry that caused heart rate to rise to 56% (light moderate exercise) and 67% (heavy moderate exercise) of maximum predicted heart rate, and a single bout of pGz. Several months later, 9 of the 14 subjects underwent passive motorized cycling. Methods The ECG and finger pulse wave were recorded. The dicrotic notch position was computed from the amplitude of the digital pulse wave (a) divided by the height of the dicrotic notch above the end-diastolic level (b) and designated the a/b ratio. Increase of the a/b ratio due to dicrotic notch descent reflects the vasodilator action of NO on resistance vessels. The last 30 s of baseline, exercise or pGz, and recovery periods were analyzed. Results Compared to baseline, light moderate exercise produced a nonsignificant rise of the a/b ratio. Both heavy moderate exercise and pGz produced statistically significant rises of peak and mean a/b ratios over baseline. Heavy moderate exercise produced a greater mean a/b ratio than pGz, but the peak a/b ratio did not differ between the two. Episodic rises and falls of a/b ratios were more common during pGz than exercise. Passive motorized cycling did not alter the a/b ratio. Conclusions Dicrotic notch descent occurs during a brief bout of moderate cycling exercise, consistent with NO release into circulation. pGz produces comparable descent, but passive motorized cycling does not. In terms of the beneficial effects of NO, this suggests that pGz might serve as a substitute in subjects who are physically incapable of exercising.

Background Expiratory flow limitation (EFL) by negative expiratory pressure (NEP) testing, quantified as the expiratory flow-limited part of the flow-volume curve, may be influenced by airway obstruction of intrathoracic and extrathoracic origins. NEP application during tidal expiration immediately determines a rise in expiratory flow ( V ˙ ) followed by a short-lasting V ˙ drop (Δ V ˙ ), reflecting upper airway collapsibility. Purpose This study investigated if a new NEP test analysis on the transient expiratory Δ V ˙ after NEP application for detection of upper airway V ˙ limitation is able to identify obstructive sleep apnea (OSA) subjects and its severity. Methods Thirty-seven male subjects (mean ± SD age, 46 ± 11years; mean body mass index [BMI], 34 ± 7 kg/m 2 ) with suspected OSA and with normal spirometric values underwent nocturnal polysomnography and diurnal NEP testing at – 5 cm H 2 O and – 10 cm H 2 O in sitting and supine positions. Results Δ V ˙ (percentage of the peak V ˙ [% V ˙ peak]) was better correlated to apnea-hypopnea index (AHI) than the EFL measured as V ˙ , during NEP application, equal or inferior to the corresponding V ˙ during control (EFL), and expressed as percentage of control tidal volume (%Vt). AHI values were always high (> 44 events/h) in subjects with BMI > 35 kg/m 2 , while they were very scattered (range, 0.5 to 103.5 events/h) in subjects with BMI 2 . In these subjects, AHI still correlated to Δ V ˙ (% V ˙ peak) in both sitting and supine positions at both NEP pressures. Conclusions OSA severity is better related to Δ V ˙ (% V ˙ peak) than EFL (%Vt) in subjects referred to sleep centers. Δ V ˙ (% V ˙ peak) can be a marker of OSA, and it is particularly useful in nonseverely obese subjects.

Study objectives: In obese patients, obstructive sleep apnea syndrome (OSAS) is attributed to a reduction in pharyngeal cross-sectional area due to peripharyngeal fat deposition. The effect of weight loss on the size of the upper airways of obese subjects is still unknown. We analyzed the pharyngeal cross-sectional area before and after weight loss in morbidly obese patients with OSAS. Design, setting, and subjects: A group of 17 middle-aged, morbidly obese men was evaluated by anthropometry and cardiorespiratory sleep studies before and after weight loss obtained by insertion of an intragastric balloon. The pharyngeal cross-sectional area was measured by acoustic pharyngometry. Results: The mean ( SD) body mass index was 55.8 9.9 kg/m 2 at baseline and 48.6 11.2 kg/m 2 at the time of balloon removal (6 months after insertion) [p < 0.001]. At baseline, patients had visceral obesity, large necks, and severe OSAS. Weight loss was associated with a significant mean reduction of waist circumference (156.4 17.6 vs 136.7 18.4 cm, respectively; p < 0.001), sagittal abdominal diameter (37.8 3.0 vs 32.3 4.0 cm, respectively; p < 0.001), and neck circumference (51.1 3.7 vs 47.9 4.3 cm, respectively; p < 0.001). Moreover, weight loss induced a nearly complete resolution of OSAS (apnea-hypopnea index, 52.1 14.9 vs 14.0 12.4 events/h, respectively; p < 0.001). At baseline, obese patients had significantly lower pharyngeal cross-sectional areas compared to a group of 20 nonobese male control subjects, both in the upright and supine position, at different levels of the pharynx. In obese patients, the weight loss induced by the positioning of the intragastric balloon was associated with an increase in the size of the upper airway passage. After weight loss, both the mean pharyngeal cross-sectional area and the area at glottis level were still lower in obese subjects than in nonobese subjects; however, the pharyngeal cross-sectional area at the oropharyngeal junction was similar in the two groups. Conclusions: Morbidly obese men with OSAS have a reduced pharyngeal cross-sectional area. A weight reduction of about 15% of baseline body weight may substantially increase the pharyngeal cross-sectional area and substantially improve the severity of OSAS in morbidly obese subjects with sleep apnea. (CHEST 2005; 128:618–623)

In patients with acute left heart failure (LHF), orthopnea has also been related to the occurrence or worsening of expiratory flow limitation (EFL) in the supine position. We wished to assess whether short-term treatment with vasodilators and diuretics was able to abolish supine EFL and whether this could help to control orthopnea in patients with acute LHF.In nine nonobese (ie, mean [+/- SD] body mass index, 24 +/- 5 kg/m2), never-smoker patients (two men and seven women; mean age, 77 +/- 7 years) with acute LHF (mean ejection fraction, 43 +/- 15%), we assessed EFL by the negative expiratory pressure method and dyspnea by the Borg scale, with patients in both the seated and supine positions, before and after short-term treatment with vasodilators and diuretics until hospital discharge. Orthopnea was defined as a positive difference in the Borg score between measurements made with the patient in the supine and seated positions. Postural variations in the end-expiratory lung volume were inferred from changes in inspiratory capacity (IC) that were measured under the same circumstances.Before treatment, with the patient in the seated position the mean dyspnea score was 1.5 +/- 0.5, the mean IC was 1.49 +/- 0.38 L, seven patients were non-flow-limited, and two patients were flow-limited. During recumbency, the mean dyspnea score was 2.7 +/- 0.5 (p0.01 vs seated position values), the mean IC was 1.66 +/- 0.45 L, and seven patients exhibited EFL. After a mean duration of 17 +/- 8 days of treatment (range, 7 to 28 days), EFL was detected in two patients only in the supine position, IC increased both in the seated position (1.65 +/- 0.34 L; p0.01) and the supine position (1.81 +/- 0.41 L; p = 0.07) position, and, although only two patients denied orthopnea, the mean dyspnea score during recumbency actually decreased to 1.9 +/- 1.0 (p0.05).Our results indicate that short-term treatment with vasodilators and diuretics is able to control orthopnea and to remove supine EFL in most patients with acute LHF, suggesting a posture-related increase in bronchial obstruction as the main mechanism of EFL, which appears to play a role in the occurrence and severity of orthopnea in these circumstances.

A 75-year-old man was evaluated in consultation for dyspnea. He was admitted to the hospital 1 day earlier with chest pain and progressive dyspnea over 12 months, which was mild with exertion but worse when he lay flat. He noted increasing daytime fatigue over the same time period. He had been able to work until recently as a building maintenance man. After hospital admission, he underwent cardiac catheterization, which showed no evidence of coronary artery disease. A sudden worsening of dyspnea developed, however, while he was lying supine at the end of the procedure.

Background Prone positioning may improve oxygenation in patients with acute lung injury/ARDS. However, the beneficial effect of prone positioning on gas exchange has never been investigated in patients with diffuse pulmonary infiltrates who breathe spontaneously Objective To evaluate the effect of body position on gas exchange in patients with idiopathic pulmonary alveolar proteinosis (PAP) with special reference to the benefit of prone positioning Design A prospective study Setting Tertiary medical center Patients and methods Eight patients with PAP were studied on 25 occasions using spirometry, body plethysmography, and single-breath diffusing capacity of the lung for carbon monoxide (D lco ). Arterial blood gas levels were measured in the sitting position and in four lying positions randomly while patients breathed room air. To serve as control subjects, 16 age-matched healthy hospital personnel were studied. To evaluate the impact of oxygen therapy on positional effect in gas exchange, arterial blood gas levels were measured in the supine and prone positions in some PAP patients while breathing 40% oxygen Results Normal to varying degrees of restrictive ventilatory defect and gas exchange impairment, as evidenced by D lco , Pa o 2 , and alveolar-arterial oxygen pressure difference (P[A-a]O 2 ), were found in PAP patients. The ventilatory function parameters correlated positively with Pa o 2 and negatively with P(A-a)O 2 . The values of Pa o 2 and P(A-a)O 2 measured in four lying positions showed no significant difference in both PAP patients and healthy control subjects. Furthermore, the differences in Pa o 2 and P(A-a)O 2 between measurements made in the supine and prone positions and the ratio of Pa o 2 measured in the prone position/Pa o 2 measured in the supine position were comparable between PAP patients and healthy control subjects. Arterial blood gas levels showed no significant difference between measurements made in PAP patients in the supine and prone positions while breathing 40% oxygen Conclusions Positional change did not significantly affect gas exchange, and no benefit of prone positioning was found in both PAP patients and healthy control subjects. Further studies are needed to verify the benefit of prone ventilation in patients with diffuse pulmonary disorders who breathe spontaneously

Objectives We present reference values for arterial blood gas measurements for persons > 70 years old. At the same time, we wish to examine how different criteria for exclusion from the reference sample with regard to previous smoking and various comorbidities might influence reference values. Methods After first screening a random sample of the general elderly population by postal questionnaire, we selected 146 men and women without respiratory disease, significant dyspnea, symptomatic heart disease or hypertension, or current smoker status. Arterial blood samples were drawn from subjects while in the supine position. Results The mean (SD; lower limit of normal) Pao2 and arterial oxygen saturation (Sao2) for men was 77.0 mm Hg (9.1; 62.0) and 95.3% (1.4; 93.0), respectively, and for women was 73.5 mm Hg (8.4; 59.6) and 94.8% (1.7; 92.0). Mean (SD; upper limit of normal) Paco2 was 39.4 mm Hg (3.3; 44.8) for both sexes. None of the blood gas variables were associated with age, smoking history, or presence of various comorbidities. Conclusions The reference values for Pao2 and Sao2 in elderly persons are sex specific but age independent. Ex-smokers and persons with nonpulmonary comorbidities who do not have significant respiratory symptoms need not be excluded from the reference sample for arterial blood gases.

Study objective: To evaluate the tolerability and to find predictors of treatment success for an individually adjusted, one-piece mandibular advancement device in patients with snoring and obstructive sleep apnea. Design: Prospective study. Setting: Departments of Respiratory Medicine and Orthodontics, Umea University. Patients: Six hundred nineteen of 630 patients (98%), who consecutively received treatment for sleep apnea and snoring from February 1989 to August 2000, were followed up. They had a mean apnea-hypopnea index of 16 (range, 0.0 to 76) and a mean body mass index of 28 (range, 19 to 42). Measurements: Interviews, questionnaires, and overnight sleep apnea recordings. Patients with an apnea-hypopnea index of > 10 in the supine and/or lateral position were considered to have obstructive sleep apnea. A lateral apnea-hypopnea index of 10, defined supine-dependent sleep apneas. Results: One hundred forty-eight of the 619 patients (24%) discontinued treatment. Female gender predicted treatment success, defined as an apnea-hypopnea index of < 10 in both the supine and lateral positions, with an odds ratio of 2.4 (p 0.01). In the women, the odds ratios for treatment success were 12 for mild sleep apnea (p 0.04), and 0.1 for complaints of nasal obstruction (p 0.03). In the men, the odds ratios for treatment success were 6.0 for supinedependent sleep apneas (p < 0.001), 2.5 for mild sleep apnea (p 0.04), 1.3 for each millimeter of mandibular advancement (p 0.03), and 0.8 for each kilogram of weight increase (p 0.001). Conclusions: The mandibular advancement device is recommended for women with sleep apnea, for men with supine-dependent sleep apneas defined by a lateral apnea-hypopnea index of < 10, and for snorers without sleep apnea. Men who increase in weight during treatment reduce their chance of treatment success and are advised to be followed up with a new sleep apnea recording with the device. (CHEST 2004; 125:1270 –1278)

Background: The negative expiratory pressure (NEP) technique is used to detect intrathoracic expiratory flow limitation (EFL) in patients with respiratory disorders. Application of NEP may result in a sustained decrease of flow below control as a result of upper airway collapse, which may invalidate interpretation of the test. This response to NEP is common in patients with obstructive sleep apnea syndrome (OSAS). The prevalence of this phenomenon, however, has not been studied in healthy subjects and patients with obstructive and restrictive disorders without OSAS. Purpose: The purpose of this study was as follows: (1) to assess the effects of increasing NEP levels on upper airway patency, and (2) to determine the factors that predispose to intrathoracic flow limitation or upper airway collapse during NEP application in different postures in healthy nonobese and obese subjects, and in patients with obstructive and restrictive respiratory disorders. Subjects: Fifty-six patients with obstructive airway disease (21 patients with COPD, 16 patients with simple chronic bronchitis, and 19 patients with asthma) were compared with 47 patients with restrictive respiratory disorders, 20 nonobese and healthy subjects, and 9 obese subjects (body mass index > 30) without a history of snoring or OSAS. Methods: NEP at levels of 5 cm H2O, 10 cm H2O, and 15 cm H2O were applied at the mouth immediately after the onset of tidal expiration while seated and supine. Intrathoracic EFL was defined as no change in expiratory flow over any portion of the immediately preceding control breath. Upper airway collapse or narrowing was detected when flows decreased below those of the control breath. Results: Ten patients (18%) with obstructive airway disease (7 patients with COPD) exhibited EFL at NEP of 5 cm H2O (4 patients were supine only, and 6 patients were both supine and sitting). No patient with restrictive disorders or healthy obese and nonobese subjects presented EFL at NEP of 5c m H 2O. In almost all subgroups, both seated and supine, subjects exhibited a transient decrease of flow below control immediately after the application of NEP in occasional breaths. As NEP increased, the number of subjects who exhibited this response in occasional breaths declined, while the number of subjects who displayed this pattern in all breaths increased. Conversely, there were very few subjects in each subgroup who exhibited a sustained decrease in flow below control in occasional breaths at NEP at 5 cm H2O, and only one healthy obese subject who displayed this response in all breaths in supine position only. Conclusions: In general, an increase in NEP resulted in only rare instances of sustained decrease in flow below control in all breaths. While transient decreases in flow exhibited immediately after the onset of NEP in all breaths are common and become more prevalent as NEP is increased beyond 5 cm H2O, there are only rare instances of sustained decrease in flow below control throughout expiration at all levels of NEP tested, indicating an appropriate upper airway dilator response that maintains patency. Thus, in subjects without OSAS, assessment of intrathoracic EFL with NEP is valid in almost all instances. (CHEST 2004; 125:98 –105)

A pproximately 50% of patients who are admitted to the hospital with community-acquired pneumonia will develop a pleural effusion.1,2 While most parapneumonic effusions will resolve without specific therapy, approximately 10% will become complicated or progress to empyema.3 Because delays in the drainage of these clinically significant effusions have been associated with increased morbidity and mortality,4 prompt detection and accurate characterization of a parapneumonic effusion are important. Guidelines5 based on a consensus conference have comprehensively summarized the literature regarding parapneumonic effusions and have made specific recommendations for their management. Although this document reflects the “state of the art,” as the authors noted, most studies of parapneumonic effusions have been observational, often with a limited numbers of patients. One of the recommendations in the guidelines was that all patients with a parapneumonic effusion should have a chest radiograph performed with a lateral decubitus view.5 This recommendation also was incorporated into the American Thoracic Society guidelines6 for the care of adults with communityacquired pneumonia. The rationale is that if the thickness of the effusion on the lateral decubitus view is 1 cm, the effusion is small enough so that no further intervention is needed.1 While there is good evidence that small effusions resolve without specific therapy,1 the suggestion that a lateral decubitus radiograph is required to determine the appropriate course of action with respect to a parapneumonic effusion appears to have been made without sufficient supporting data. The purpose of this article is to review the indications and usage of the lateral decubitus chest radiograph and demonstrate its limited value in the setting of parapneumonic pleural effusions. Radiographs of the chest made with the patient in the standard erect position usually will not reveal the presence of a pleural effusion 300 to 500 mL in size, as the fluid usually pools in the posterior costophrenic sulcus.7,8 The varying volumes reported may be due to differences in patient size, as a larger individual probably can “hide” a larger volume of fluid than can a smaller individual. The lateral decubitus view was first described by Merlo Gomez and Heidenreich,9 in 1924, as a technique to identify the presence of small pleural effusions. Its first English-language description was by Rigler,7 in 1931, who used this technique to confirm the presence of pleural effusions in a small series of patients despite the absence of a visible effusion using the standard erect views. Subsequently, other investigators demonstrated that the sensitivity of this view can be increased by placing a pillow under the patient’s pelvis, so that the thorax slopes downward away from the lung base.10 By injecting known amounts of fluid into cadavers, in 1973 Moskowitz et al8 demonstrated that effusions as small as 5 to 10 mL could be detected using the lateral decubitus view.

Background Nontoxic goiters can cause extrathoracic upper airway obstruction and, if large, may extend into the thorax, causing intrathoracic airway obstruction. Although patients with goiter often report orthopnea, there are few studies on postural changes in respiratory function in these subjects. Purpose The aim of this study was to investigate the postural changes in respiratory function and the presence of flow limitation (FL) and orthopnea in patients with nontoxic goiter. Methods In 32 patients with nontoxic goiter, respiratory function was studied in seated and supine position. Expiratory FL was assessed with the negative expiratory pressure method. Goiter-trachea radiologic relationships were arbitrarily classified as follows: grade 1, no evidence of tracheal deviation; grade 2, tracheal deviation present in lateral and/or anteroposterior plane but with tracheal compression 20%. Subgroups were considered according to this classification and occurrence of orthopnea and FL. Results In all three groups of patients, the average maximal expiratory flow at 50% of FVC/maximal inspiratory flow at 50% of FVC ratios were > 1.1, suggesting the presence of upper airway obstruction. Grade 3 patients had a significantly lower expiratory reserve volume and maximal expiratory flow at 25% of FVC and higher airway resistance and 3-point FL score than patients with grade 1 and grade 2. The prevalence of orthopnea was highest in patients with grade 3 (75%, as compared to 18% in the grade 1 group). In patients with orthopnea, the prevalence of intrathoracic goiter was also higher (78%, vs 21% in patients without orthopnea). Conclusion There is a high prevalence of orthopnea in patients with goiter, especially when the location is intrathoracic and causes a reduction of end-expiratory lung volume and flow reserve in the tidal volume range, promoting FL especially in supine position. Obesity is a factor that increases the risk of orthopnea in patients with goiter.